Spreadsheet: 10a347cf-2f2c-4a31-bb5d-12681ee3713e
Sheet: Author Response

Surname | Given Name | Organization | Chapter | Section | Page | Line | Reviewer Comments | Author Response | Review Editor Comments
[NAME] | Mark | University of Illinois at Urbana-Champaign | 4 | 0 | 0 | 0 | The overall mass balance looks to be quite well done within the limitations of the data available. The authors are commended for pulling together the best estimates of N fluxes for a complex state with many vegetable crops. | Thank you.
[NAME] | Mark | University of Illinois at Urbana-Champaign |  |  | 0 | 0 | One of the largest inputs (synthetic fertilizer) seems to have some major problems with record keeping in California. I have seen this problem in Illinois as well, and have worked around this. The comparison of calculated fertilizer based on crop recommendations and fertilizer sales was a good idea, and gives support to the final value used. I think the authors did the best they could with this important input. | Thank you.
[NAME] | Mark | University of Illinois at Urbana-Champaign | 4 | 4.2.5 | 20 | 405-411 | Leaching to groundwater turns out to be a major flow, but there really isn't a rigorous way to estimate it. I appreciate the two methods used, but is it possible that more of this leached N (nitrate) is removed through denitrification somewhere in the flow path (below the soil zone where you earlier estimated N gas loss)? | We consider nitrate leached below the rooting zone to be a loss for cropland.  We have added an estimate for denitrification in groundwater.  We don't believe much denitrification occurs in the unsaturated zone, but we have decreased groundwater storage considerably by adding a denitrification term.
[NAME] | Mark | University of Illinois at Urbana-Champaign |  |  | 42 | 910-913 | Might discuss what the major crops were, as I didn't see a list anywhere. I would think a supplemental table of the crops grown would be useful, with the % of N harvested by each. If there isn't a major one, note it, or discuss further the top few. Is corn a major crop at all? If so, be aware that grain protein N has been declining and that change would not be in the USDA database. | We have added a table with the most important crops for the mass balance.  We agree that the nutrient content database is somewhat dated, but we are unaware of more recent information for most of the important crops in California.
[NAME] | Mark | University of Illinois at Urbana-Champaign |  |  |  | 926-928 | Something got dropped here? Doesn't make sense. | We have clarified this.
[NAME] | Mark | University of Illinois at Urbana-Champaign |  |  |  | 963 | The cows were dry? Does this mean no milk production? Might explain to be clear. | We have clarified this.
[NAME] | Mark | University of Illinois at Urbana-Champaign |  | Table 4.3 | 84 |  | The estimated alfalfa N2 fixation rate is much higher than what others have used in mass balances. Is the [NAME] et al. (2010) approach really supported? They only compiled data for Australia and their range of data is much lower than yields in California. Since this is the major N fixing crop you should compare this value to what others have used, to make clear you are using a much greater value. | We agree that it is important to get the alfalfa fixation rate correct.  We tried to trace back the values that others have used and were not very successful in identifying the original research that measured fixation or found that the rates might not be representative.  We feel that a measure that takes into account productivity differences is more realistic for alfalfa.  There is a surprising lack of data on alfalfa N fixation in California where productivity is at least double if not 5 times higher than many other parts of the US.  We feel that the [NAME] et al 2010 synthesis provides a more reliable estimate than the few individual studies that report rates on a kg N/ha basis largely from the upper midwest and Canada. For example, [NAME] et al. (2002) cite [NAME] et al. (1984) which quantified fixaiton from one site in Minnesota.  Jordan and [NAME] (1996) cite a value from Wiscosin in Keneey (1979) which was equal to harvested N plus residual N and not necessarily fixed [NAME]
[NAME] | Mark | University of Illinois at Urbana-Champaign | Supplemental tables |  |  |  | These are a good addition, and cover many of the assumptions, data sources, and other information used in the mass balance chapter. I suggest a list of crops grown in California along with the %N used in harvested tons (see also my earlier comment). | As above, we have added a table with the most important crops for the mass balance.  We agree that the nutrient content database is somewhat dated, but we are unaware of more recent information for most of the important crops in California.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | Main message | 5 | 73-76 | there is a difference between the amount indicated in the title and the sum of the components, 519 vs 521 (424+44+53) | We have revised the mass balance calculations throughout and double checked that the numbers in the tables and figures match the text.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | Main message | 5 | 87-90 | line 87 said "Synthetic fertilizer (466 Gg N yr-1) is the largets source of N to cropland". According to line 74 the 466 Gg of N should be coming from cultivated agriculture plus environmental horticulture, which is also a different amount 424+44=468. If this is correct, please re-write or include both in one paragraph. | As above, we have revised the mass balance calculations throughout and double checked that the numbers in the tables and figures match the text.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | Main message | 5 | 84-86 | In the last ~4 years all dairy producers in CA are doing NMP for liquid and solid manure required by the Water Quality Control Board. They are using manure as a N fertilizer based on chemical analysis of manure and crops requirements. In other words, "a large fraction" of manure is been applied in a NMP. | We have learned that the manure reported in the Agricultural Commissioners' reports was not actual manure sales but "potential" manure sales.  We therefore have no way of determining the partitioning of manure use statewide.  There is the potential to use the NMP submitted to the WQCBs, but at the time of these calculations, those data are not yet easily accessible. The implementation of NMPs and their future potential is now discussed in the chapter.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | Main message | 8               17           22 | 142-143     343-345      457-458 | It is suggested to indicate in the Main Message the importance of the "potential" use of NMP and N balances information from the CA  WQCB. This data base is critical for the future mass N balances in CA. | This has been updated.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | 4.1.3.2. | 22-23 | 461-464 | Comment, most of dairy farmers are using liquid manure for irrigation (mixed or diluted with water), dry manure from corrals and composted manure is used as bedding and the rest of manure is exported. | We have removed the discussion of liquid manure.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | 4.2.5 | 43 | 926-928 | please, check paragraph | This has been updated.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | 4.2.6. | 46 | 1005-1006 | please, explain how it was estimated the milk N:solid manure N ratio of 1.33:1 | We have removed this discussion.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | 4.27. | 47 | 1022 | please, delete the comma at the end of the line. | This has been updated.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | figure 4.1 | 71 | 1570 | please, check where said "(feed, fiber, and feed)" | The figure and its legend have been checked for accuracy.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County | 4 | table 4.7. | 88 | 1702-1703 | Please, explain "this is not equivalent to portioning of N in excretion", its relationship with the formula described in page 47 line 1009-1010,   and the paragraph in page 17 lines 339-342. | We have removed this discussion.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County |  | Supplemental Data Tables |  |  | Table 15. Manure. Most of the uncertaninties indicated in this Table can be resolved using the NMP information from the WQCB. Also, due to manure NH3 volatilization and the low N:P ratio in the manure dairy producers are combining manure and inorganic fertilizers, this information is included in the NMP. | The NMP will be a great resource once they are easily accessible. The implementation of NMPs and their future potential is now discussed in the chapter.
Castillo | Alejandro R. | UC Cooperative Extension, Merced County |  | references |  |  | Because references are 'in development', please do not hesitate to email me the new version to check the references in the final manuscript. | Thank you.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | General comment |  |  | Overall, this mass balance chapter is very nicely done.  The analysis is comprehensive and each term is completely discussed and well justified.  Really nicely done!I had some trouble with the organization and I think that there is a need for some comparison with previous mass balance studies as detailed below.  I was asked to focus on section 4.1.6 so I made more detailed comments on that section. | Thank you. We have added a new synthesis section to compare our mass balance to other similar ones at vaious spatial scales around the world.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | General comment |  |  | It would be nice to see a summary statement about the uncertainty analysis, a brief discussion of just which terms are good and which are bad and are the really big terms good or bad?  It seems to me that the really important terms are pretty well constrained.  It might be nice to state that. | There is now a main message related to uncertainty, additional text and a figure has been added to the introduction , and the uncertainty terminology has been added to the mass balance tables.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | General comment |  |  | It would be nice to see some comparison with other regional mass balance studies.  Several of these were done in the 1970s and then many, many country-wide studies have been done in the last 10 years or so.  You've done an excellent job of describing the N mass balance in California.  But how does it compare with the rest of hte world? | We have added a new synthesis section to compare our mass balance to other similar ones at vaious spatial scales around the world.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | General comment |  |  | The organization might be backwards in that the results are presented before the Methods.  This makes it very difficult to read and review.  I think it would be better to present the data sources (including the very nicely done supplementary tables) and calculations first and then the results. | We agree that the structure is not typical of a research paper, but based on our goals, we felt that having the main messages followed by results followed by methods and supplemental information would be the most effective way to reach our audience.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 9 | 146-148 | I am assuming that earlier chapters establish that nitrogen is a threat to the "health and vitality of California . . ."  Otherwise you might want to support this statement a bit with some specific examples from California.   Many readers may not be aware that "nitrogen is a problem. | We touch on the issue here, but the main discussion of the problems associated with excess N are addressed elsewhere in the assessment.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 9 | 152-156 | Has the term "ecosystem services" been defined earlier.  This may not be a familiar term to many readers. | This is a term that will be included in the glossary.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 11 | 202 | Do you have a list of the small flows that you did not include? | No.  All of the flows we tried to estimate were greater than 1 Gg N/yr except for N2O emissions from fire.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 14 | 269 | Maybe specify how much of the export was as N2 - an important conversion of reactive N to non-reactive N. | This has been added.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 15 | 293 | Townsend-Small et al. (2010) published some data on C accumulation in turfgrass in California; Townsend-Small, A. and [NAME]. 2010. Carbon sequestration and greenhouse gas emissions in urban turf. Geophysical Research Letters 37:doi:  L0270710.0271029/0272009gl0041675. | This reference has been added.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 15 | 296-297 | It is hard to infer anything about storage of N from burial of waste products without knowing anything about the C:N ratio of those products. | This has been updated.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 21 | 423-429 | Adding water and fertilizer should definitely increase the C and N content of agricultural soils. | We agree that the evidence suggests this, but there are limited data on the magnitude of N storage.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 |  | 23 | 483 | Some turfgrass gas flux studies in California:  Townsend-Small, A., [NAME], [NAME], and [NAME]. 2011. Nitrous oxide emissions and isotopic composition in urban and agricultural systems in southern California. [NAME]. [NAME]. 116:[NAME].                   Bijoor, [NAME], [NAME], [NAME], and [NAME]. 2008. Effects of temperature and fertilization on nitrogen cycling and community composition of an urban lawn. Global Change Biology 14:2119-2131. | These references have been added.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | 4.1.6.1 | 27 | 564-596 | The calculation for natural land inputs seems reasonable to me.  The atmospheric deposition numbers are from a state-of-the-art model and the N fixation estimate is well reasoned if not well supported by actual data.  Uncertainties are well presented in the supplementary table. | Thank you.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | 4.1.6.2 | 29 | 599-605 | This is where I got frustrated with presenting the results before the Methods.  I read this and I am wondering what  these gas estimates are based on.  It is only much later that I see that it is based on a compendium of published studies.  I note that I didn't see the appendix with the N2O studies.  I am hoping that they include the early work by [NAME]. that found some very high rates of N2O and N2 flux in California agricultural systems. | Several decades ago, there were many important papers published on denitrification in agricultural soils in California, including many by researchers at UC Davis.  These studies for N2 emissions are included in the Schlesinger 2011 database that we base our N2:N2O emissions on.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | 4.1.6.2 | 29 | 606-613 | Aren't there some data from actual emissions of specific N species from fires? I remember some papers by [NAME] on this topic . . . | We could not locate a source that included an estimate of the emisisons of all four N gases.  We could only find estimates of each gas (except [NAME]) individually and an estimate of total N volatilized.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | 4.1.6.2 | 29 | 615-622 | The calculations for runoff, and the modifications for California seem reasonable to me. | Thank you.
Groffman | [NAME] | Cary Institute of Ecosystem Studies | 4 | 4.1.6.2 | 30 | 626-636 | The estimate of storage seems reasonable to me.  Many other natural ecosystems appear to be storing [NAME]  It might be worth making some comparisons to see if the storage here is similar to what has been observed elsewhere.  I suspect it is. | In the new synthesis section (4.3) we include a comparison of storage.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 5 | The discussion about the lack of a standard analytical protocol for field N2O fluxes is unnecessary and not particularly correct.  There are no standard protocols for many of the variables in this mass balance. Lack of a standard protocol is not the key factor  limiting our understanding of N2O fluxes by any means. | This has been updated.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 5 | The statement that "Ongoing research in California . . .suggests that with proper management, N2O emissions from well managed California crops can be significantly lower than the global averages" is puzzling given that very high rates of N2O production have been reported in California agroecosystems (Ryden studies in the 1970s) and is not supported by data. | Several state agencies have been funding coordinated studies on N2O emissions from the major crops in California using current fertilization and soil management practices.  While these data are not published yet,meeting abstracts suggest that rates are much lower on an absolute and relative basis compared to some of the earlier studies.  Many of the early studies reported quite high fertilization rates (in excess of 500 kg N/ha) on vegetable crops which may explain the extremely high measured values.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 5 | In the discussion about methods for measuring dinitrogen fluxes there is an error.  [NAME], not ethylene is used for these assays. | This has been corrected.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 5 | For dinitrogen, note that some of earliest/best measurements of of both 15N2O and 15N2 were made in California by [NAME] and colleagues in the 1970's.  And [NAME] also made acetylene-based estimates of in situ N2 flux in California in the 1970s. | This has been noted.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 5 | I know that some soil nitric oxide flux measurements were made in California by [NAME] and also by [NAME].  I'm not sure just what systems though. | There are a handful of studies measuing NO in natural lands in California and [NAME] has published some excellent mechanistic work on NO in agricultural soils.
Groffman | [NAME] | Cary Institute of Ecosystem Studies |  |  |  | Supplementary data table 9 | For soil nitrogen storage under turfgrass you should consult some of the work done in more arid regions instead of the [NAME] et al. work done in Maryland).  Good work has been done in Phoenix ([NAME], [NAME]), Colorado (Kaye, Golubiewski) and in California (Pataki, Townsend-Small). | There has been work in arid regions on C storage, but as far as we are aware, not N storage.
Horneck | [NAME] | Oregon State University | 4 | general |  |  | get rid of synthetic, N is not syntetic like plastics…  Can substitute inorganic, industrially fixed… | We recognize that there is no generally accepted term for the materials we are including as synthetic N. We chose to use synthetic N  for any N not fixed by biological processes.  Inorganic is not appropriate as many of the chemicals made from fixed NH3 are organic compounds.  Industrially fixed N could include industrial emissions of NOx which we treat separately.  Even Haber-Bosch N is not completely inclusive as much of the ammonium sulfate is produced as a byproduct of industrial processes.  We have clarified what we mean in section 4.1 and define this term in the glossary.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 73 | there is no such thing as synthetic fertilizers, commercial fertilizer or commercial fertilizers sold in retail establishments | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 77 | manure does not create N as stated in previous section.  This is either fixed N from legumes or commercial fertilizer from plants fed | We do not claim that manure creates N, but in our budget it can be an input or ouput depending on the subsystem.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 80 | get rid of natural | Similar to the word synthetic, we use the word "natural" because of a lack of better terminology.  We are clear that natural refers to areas that are not included as agricultural or urban according to our data sources.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 83 | composting cause a large loss of N into the air and is relatively stabel in the soil compared to manures | The loss of N during composting of manure should be included in our estimate of manure NH3 emissions.  There is likely some emission of N2O as well.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 87 | no such thing as synthetic | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 89 | synthticall should eith be haber-bosh process or fixed anthropogenically | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 91 | natural land?  Is there unatural? | As above, we refer to natural land as areas that are not included as agricultural or urban according to our data sources.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 91-91 | The depostion of N from antropogenic soures has increased of which a large portion is from the haber bosh process | This is true, but for our accounting it doesn’t matter what the initial source of the N was to calculate the transfer of N from the atmosphere to the surface.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 92 | biological fixation was… | Text has been clarified.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 94 | new inputs? How about just inputs | We use the word new to distinguish newly fixed N from the transformation of existing N.
Horneck | [NAME] | Oregon State University | 4 | main messages | 5 | 94 | depostion rate | Comment is unclear. But, text has been revised and includes N deposition.
Horneck | [NAME] | Oregon State University | 4 | main messages | 6 | 95 | you mean depostion in cities and cropland is 150 kg N/ha? | This has been clarified.
Horneck | [NAME] | Oregon State University | 4 | main messages | 6 | 97 | sentence makes no sense to me...    Deposition instead of fixation and moderate as comapred to?  I do not get the fixation part, anyways this sentence needs help | This sentence has been clarified.
Horneck | [NAME] | Oregon State University | 4 | main messages |  | 103 | urban land is accumulating N?  This is had to believ in a very arge sense, all N sources turn over at some rate into reactive N and move. | There is some accumulation of N in turfgrass soils, but a large fraction of the N accumulation is in long-lived fiber products and synthetic chemicals and material buried in landfills.
Horneck | [NAME] | Oregon State University | 4 | main messages |  | 112 | into the ocean | We prefer "to" instead of "into".
Horneck | [NAME] | Oregon State University | 4 | main messages | 8 | 142-143 | discharge? Will be a problem? | This has been clarified.
Horneck | [NAME] | Oregon State University |  |  |  | 152 | what human health effects?  All the nitrte stuff is largely been discredited | The human health effects are discussed at length later in the assessment (chapter 5).
Horneck | [NAME] | Oregon State University |  |  | 9 | 165 | get rid of about | Changed
Horneck | [NAME] | Oregon State University |  |  | 10 | 169 | to make  informed  management and policy decision. | Changed
Horneck | [NAME] | Oregon State University |  |  |  | 208 | ornamental horticulture | We prefer environmental horticulture.
Horneck | [NAME] | Oregon State University |  | 4.1 | 13 | 245 | flows should be flow | Changed
Horneck | [NAME] | Oregon State University |  | 4.1.1 | 13 | 251 | synthetic fixation?  Industrial fixation is probably better stated | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University |  |  |  | 253 | synthetic=industrial | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University |  |  |  | 256 | synthetic=industrial | As above, we refer to any fertilizer that results from the non-biological fixation of NH3 as synthetic.
Horneck | [NAME] | Oregon State University |  |  |  | 275 | get rid of as | Changed
Horneck | [NAME] | Oregon State University |  |  |  | 275 | what about NH3 volatilization from ammonia based fertilizers? | This section only deals with exports from the state.  NH3 from fertilizer leaves the cropland subsystem, but isn't necessarily an export from the state as it can be redeposited.
Horneck | [NAME] | Oregon State University |  |  | 15 | 282 | stored in groundwater and soils is not the same thing.  Stored in soils insinuated that it the N is still available and can be stored in the food pool and even exported.  Stored in groundwater insinuates a much longer residence time in tehi pool than the soil pool | This has been clarified.
Horneck | [NAME] | Oregon State University |  |  |  | 288 | I view the storage of n in soils to be much like the air.  A temporary holding place but the net flux  in storage amount is pretty low year to year.  This N moves on else the N concentration in soils is going up… probably not.  [NAME] may be going up, vadose zone N may be going up but probably not soil N.  with better manure management it may very well be going down. | The literature suggests that many of the soils in California have been slowly accumulating N for decades because of increasing N inputs.  It is certainly true that this N can be mobilized if the management changes, but the evidence is consistent that groundwater, the vadose zone, and soils are all increasing in the N stored there.
Horneck | [NAME] | Oregon State University |  |  |  | 291-… | yes nitrogen storage is related to C storage.  Perenial crops such as grapes and trees may have slight increases in C but crops like alfalfa which will increase C for a period will lose all its stored C upon  plowing so for stand life there is accumulation but not much long term.  these soils also do not increase in C very rapidly or very much.  There is also a ceiling they do not accumulate C forever. | We agree that soils can not accumulate organic forever.  However, based on the empirical evidence, it is suggested that the N content in soils is increasing.
Horneck | [NAME] | Oregon State University |  |  | 16 | 309 | we are showing N volatilization losses averaging 25% of applied N where urea is used.  Not as unconsequential as we have thought in the past. | We agree that there is high potential for N losses from particular N fertilizers.  We chose to use an average across a range of fertilizers since the volatilization depends on the type, amount, and method of application of the fertilizer.
Horneck | [NAME] | Oregon State University |  |  | 19 | 383 | need to check how much of your fertilizer was sold as urea.  Losses from urea are being shown to be much higher than previously thought in MT and OR | See above
Horneck | [NAME] | Oregon State University |  |  | 21 | 447 | was excreted should be is excreted | We use the past tense to report all the N flows.
Horneck | [NAME] | Oregon State University |  |  | 23 | 462 | lose the period (.) | The chapter has been edited for grammer and langauge.
Horneck | [NAME] | Oregon State University |  |  |  | 461-464 | this sentence is very vague and confusing and needs some clarification…  them, those… | The section on liquid manure has been removed
Horneck | [NAME] | Oregon State University |  |  |  | 472 | "was a major floe of N"  really means notheing and should be left out or reworded | We define the categories for the size of flows in Box 1.
Horneck | [NAME] | Oregon State University |  |  |  | 473-478 | this sentences has too many periods to be understandable | The chapter has been edited for grammer and langauge.
Horneck | [NAME] | Oregon State University |  |  |  | 488 | any N seems a bit extreme.  Does not turfgrass get mowed and clippings get harvested?  There is substantial N in clippings.  What about gasseous losses as NH4 from surface applications? Though grasses are very efficient and leaching losses are minimal where the clippings go is wher the N loss is when collected. | This has been clarified.  We assume that clippings largely stay in place.  However, for the purposes of the mass balance calculation the two possible fates for fertilizer N applied to turfgrass are soils or the landfill which are both urban land storage terms.  We do account for some gas losses, but assume dissolved losses are small.  While this is reasonable for well managed turfgrass, we don't have a way to account for this except that some of the 5.6 kg N/ha in runoff  origniates from some combination of fertilizer, deposition, and sewage.
Horneck | [NAME] | Oregon State University |  |  |  | 502 | What about gardens where lots of N gets applied and there is much greater risk for leaching loss? | We assumed that all N fertilizer on urban land was applied to turfgrass.
Horneck | [NAME] | Oregon State University |  |  |  | 508-515 | this paragraph is much better written in the present tense rather than the past.  You are using the past to predict what has happened and currently being done in CA. | We write all of the results of the mass balance in the past tense.
Horneck | [NAME] | Oregon State University |  |  |  | 522 | are not most septic systems built around turfgrass as the cover for the drain field and did you not state that turf grass has an unlimited ability to acuumulate N?  So don't these statements contradict?  I know my turf grass is getting quite a bit of N from the drain field as you can see the lines and grass growth is greener and much more vigorous | There is limited evidence for the fate of N from septic systems and the fates undoubtedly depends on how well designed the system is.  There are certainly cases where the N fertilizes plants near the drain field.  In addition, there is evidence that septic systems can contaminate surface water bodies and the groundwater.  We chose to assume that all of the N from septic systems went to groundwater.  This assumption results in the maximum potential contribution of septic systems to groundwater.
Horneck | [NAME] | Oregon State University |  |  |  | 541 | complete the sentence | The chapter has been edited for grammer and langauge.
Horneck | [NAME] | Oregon State University |  |  |  | 546 | you would not expect no3 to be present in these waste streams.  I assume they measure organic carbon if there is not any then other forms of N are unlikely. | There are relatively few measurements of forms of N other than NH3 from wastewater treatment plants.  However, for the few examples in California, NO3 and DON contribute ~10% of the total N load.
Horneck | [NAME] | Oregon State University |  |  |  | 555 | are you assuming that all this N is stored in the turf system? | We assume that all dog waste stays in soils and all cat waste goes to the landfill.
Horneck | [NAME] | Oregon State University |  |  |  | 585-586 | hard to belive that N deposition is influencing fixation at the low deopsition rates.  If this is true you need a reference | We have added a reference suppoting the notion that increased N availability leads to a loss of N fixing species.
Horneck | [NAME] | Oregon State University |  |  |  | 589 | without some references I disagree that the low end of N is where you should be, more likely middle of the road | We disagree that the middle values are more likely and state several reason why we make this assumption. If the references existed on N fixation rates in California, we would be happy to include them.
Horneck | [NAME] | Oregon State University |  |  |  | 590-596 | this seems like apolitical statement.  While true what is the point.  I f you are going use this statement why not include a statement about ubanization and the increased food production in the state.  Left as is this insinuates that we should go back to non indutrialized [NAME] (biological) alone probably eceeds this "natural" figure on a statewide basis. | This paragraph does not suggest any political viewpoint, but is included to show how much humans have altered the N cycle in the state.  The mass balance is simply an accounting of all the N flows.
Horneck | [NAME] | Oregon State University |  |  |  | 599 | what about the gaseos chemicals such as terpenes and such? | We ignore all foliar uptake and emission of N.  There is limited evidence for the rates of uptake and emission of gases like NH3 and NO from plants.  The deposition models include the uptake, but are currently be improved to allow for bidirectional NH3 movement.  We agree that terpenes and other volatile organic compounds released by plants have significant consequences for the C cycle and air chemistry. We are unaware of any measurements of the rates of the emission of any nitrogenous volatile organic compounds.
Horneck | [NAME] | Oregon State University |  |  |  | 634 | while the N would be difficult to detect in storage the carbon would not be in the short term.  It is hard to belive the storgae flow in your natural landscapes is not in equilibrium and inflow = outflow.  Otherwise in the log term these increases become significant. | We disagree that natural landscapes should be in equilibrium.  Even in the absence of human alteration of the N cycle, N accumulates and is released after disturbances (e.g. Perakis et al. 2011).  With the large changes to the N cycle related to human activity, it is even more likely that the N stored in ecosystems is changing.
Horneck | [NAME] | Oregon State University |  |  |  | 658 | I am not sure that you have such an acurrate handle on NH4 nd Nox from manure management and fertilizer management in general.  Yet these numbers are very specific and give no room for argument.  This is not right and could be taken as gospel in the future as is currently stated. | These values are based on the emissions inventories produced at the state and federal level.  We agree that there are potentially problems with these calculations, but the approaches have been vetted by many others. As with all of the flows, we report in the body of the chapter our best estimate based on as many sources of evidence that we have.  We discuss in the supplemental data tables the sources of uncertainty in these measurements.
Horneck | [NAME] | Oregon State University |  |  |  | 685-687 | oxidized - reduced?  Use NH4 and Nox these are much better and discriptive forms of the N that are being dexcribed | We use oxidized and reduced because the deposition model includes compounds that are created in the atmosphere from the emissions of NOx and NH3 such as HNO3, ammonium nitrate particles, etc.
Horneck | [NAME] | Oregon State University |  |  |  | 708-719 | since this is an estimate of loading this has to be an annual figure for resivoir loading.  Do you actually have evidene that this amount of annual loading is occurring in the sediments behind the dams? | Our calculation is based on modeled sedimentation rates, N content of the sediment, and the assumption that there is no mineralizaiton of the N in the sediments.  However, there is a large difference  between what we believe N in runoff is to what we calculate N to be for the rivers discharging to the ocean. Sedimentation in reservoirs is one possible fate along with gaseous loss.  Typically, studies of the effects of reservoirs on N combine these two potential "retention" mechanisms that decrease the load of N downstream of reservoirs.
Horneck | [NAME] | Oregon State University |  |  |  | 725-730 | manure vs cropland, how do you separate out the manure from crop land since manure when exported off the dairy is is exported to cropland and some manured fields would also get some industrially fixed [NAME] | The distinction is that some leaching occurs on the dairy facility, but most of the leaching associated with manure happens after it is applied to fields.  We can't distinguish which of the N inputs is actually leached.  We can only calculate the total N inputs and partition that between the various loss pathways.
Horneck | [NAME] | Oregon State University |  |  |  |  | This also makes some huge and variable assumtions on the efficiency of all the different systems.  Though  NASS etc has croping figures these are also very general and | Not sure what this refers to.
Horneck | [NAME] | Oregon State University |  |  |  | 736 | some estimate of statewide recharge exists as you have to manage your water resources.  This number though vague is no vaguer than the nitrogen flow estimates that are being presented here. | The understanding of groundwater budgets varies considerably among groundwater basins in the state, so there is no statewide recharge value.  We use the volume of recharge for the Central Valley, Salinas Valley, and Imperial Valley to provide an upper estimate of the concentration.  These locations include the vast majority of agricultural land and much of the groundwater recharge.
Horneck | [NAME] | Oregon State University |  |  |  | 739 | I am at a loss how you came to this conclusion | The calculation is described in 4.2.10, but briefly we divided the total N leaching from cropland soils by the volume of recharge in the
Horneck | [NAME] | Oregon State University |  |  |  | 746 | estimated not calculated | We use these terms interchangeably.
Horneck | [NAME] | Oregon State University |  |  |  | 832 | there is no empirical formula for converting alfalfa production into N biologically fixed except for in very stated onditions.  For example a maured field may have a great crop but in reality little N would be fixed. | We agree that fertilizing alfalfa would decrease N fixation rates, but we assumed that it would not be fertilized.  In California, the recommendation is to add a small amount of fertilizer at planting and then no fertilizer for the remaining years of harvesting as adding manure often decreases the quality of the crop.
Horneck | [NAME] | Oregon State University |  |  |  | 871 | or as nh4 in the air | Unsure what this comment means.
Horneck | [NAME] | Oregon State University |  |  |  | 888 | chicken manure in particular is used as a fertilizer | This section has been updated.
Horneck | [NAME] | Oregon State University |  |  |  | 889 | in reality in the arid west all manures and such replace industrially fixed N as a soil test is taken and adustments are made | See above
Horneck | [NAME] | Oregon State University |  |  |  | 893 | if I calculate this right 100 ppm times 2 m = about 1600 kg N/ha  this seems a bit unrealistic to me.  Many of these nureseries are also recycling their waters | The values of fertilization rate are extremely high, so are the harvested values, such that the ratio of harvest:applied N is similar for these crops compared to other agricultural crops.  Nurseries certainly reycle their water, but there is no evidence that they alter the N added to the irrigation water depending on the dissolved N concentration. Fertilization rates in environmental horticulture is currently an area with very few data.
Horneck | [NAME] | Oregon State University |  |  |  | 904 | did [NAME]'s tell you what percentage of the market they own and how much "regular" fertilizer was sold into these markets? | This has been updated.
Horneck | [NAME] | Oregon State University |  |  |  | 926 | annual? | This has been updated
Horneck | [NAME] | Oregon State University |  |  |  | 936 | what is being harvested that has this kind of N removal? | This value is for the N in the biomass of the plants.
Horneck | [NAME] | Oregon State University |  |  |  | 949 | with or withoout the bark on, this will make a difference | We agree that the N content of harvested wood is uncertain.  Both the presence/absence of bark, the ratio of sapwood:heartwood and the species all affect the value.
Horneck | [NAME] | Oregon State University |  |  |  | 1085 | how can you assume all N from septic goes to groundwater? | We chose to make this assumption to highlight that even if all of the N from septic systems leached to groundwater, it is still a minor contributor to groundwater [NAME]We agree that certainly not all of the septic N reaches groundwater, but this is a relatievly small flow.
Horneck | [NAME] | Oregon State University |  |  |  | 1109 | I suspect you are low on volatilization losses | This is probably an overestimate for some fertilizers and and underestimate for others.
Horneck | [NAME] | Oregon State University |  |  |  | 1164 | what bout the loss of mineral N in surface waters to N2, Nox etc | Our estimate for gaseous losses for surface water as N2 or N2O are described two paragrahs below.
Horneck | [NAME] | Oregon State University |  |  |  | 1213 | you mean to say that 0.6 kg/ha N is leached annually from ever Ha in the state?  This number is way too low for Ag | This value is only for natural areas in the closed basins of eastern California which are quite arid.
Horneck | [NAME] | Oregon State University |  |  |  | 1215 | one way to view the groundwater issue is if nitrates are still going up inputs exceed outputs but if nitrates in groundwater are stable inputs = outputs and decreasing inputs are less than outputs.  Having a handle on GW nitrates will help you balance this piece of you model | We use several lines of evidence related to the volumes of water flow and concentrations of nitrate to estimate the N balance of groundwater.
Reed | Sasha | US Geological Survey | 4 | 0 | 0 | 0 | I am impressed by the time and effort that must have gone into this assessment. The portions I read covered the important pools and fluxes in a structured and understandable way. I learned new things (e.g., I never realized pets were such a player in the California N cycle) and I enjoyed the synthesis. Nice job! | Thank you.
Reed | Sasha | US Geological Survey | 4 |  |  | 8 | I'm not sure if it's warranted, but a statement about uncertainty could be useful in this overarching section.It's stated as one of the chapters goals (line 227, page 12) and so it could be good to discuss it briefly? | There is now a main message related to uncertainty, additional text and a figure has been added to the introduction, and the uncertainty terminology has been added to the mass balance tables.
Reed | Sasha | US Geological Survey | 4 |  | 11 | 203 | Indent paragraph | Changed
Reed | Sasha | US Geological Survey | 4 |  | 13 | 239 | I would recommend either putting the definitions here (there aren't very many of them) and/or stating which Table they can be found in. | We have added a reference to the table with the definitions.
Reed | Sasha | US Geological Survey | 4 | 1.2.2 | 19 | 380 | Indent paragraph | Changed
Reed | Sasha | US Geological Survey | 4 | 1.2.2 | 20 | 395 | Can you cite where you got the 1.66 ratio? | We chose to avoid using references to the methods in the results section.  Our approach is described in 4.2.8
Reed | Sasha | US Geological Survey | 4 | [NAME] | 67 | 1499 | change 'is' to 'are' I think | Changed
Reed | Sasha | US Geological Survey | 4 | [NAME] |  |  | Sometimes here nitrogen is written out and sometimes shown as N | We have replaced nitrogen with N in the text, but not in the titles of the figures/tables.
Reed | Sasha | US Geological Survey | 4 | Fig 4.6 |  |  | I got a little distracted by the cartoon people (was there one next to food and two next to waste for a quantitative reason? Are men's restrooms to blame? Totally just a stylistic suggestion, but I would recommend just writing out human food and waste. | This has been changed
Reed | Sasha | US Geological Survey | 4 |  |  |  | I would double-check in the text and figures that you've always got NO vs. NOx when you mean to. | This has been checked.
Reed | Sasha | US Geological Survey | 4 |  |  |  | I think it would be good to reference Chapter 3.5 in the BNF section of this Chapter. | A reference to chapter 3.5 has been added to section 4.2.3.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | [NAME], General comments: Chapter 4 does an excellent job of conceptualizing the mass balance calculations for different scales and sectors and then pulling together information from many sources to complete the mass balances.  The chapter advances the methods for doing N budgets, considers more processes (e.g., fire, plastics, food waste, pets), more factors, and more details than other nitrogen mass balances I have read.  The chapter updates approaches (e.g. better atmospheric ammonia accounting) and suggests areas where improvements in nitrogen accounting and are needed.  The chapter will be a great resource for others trying to assemble N budgets and should be helpful for studies of anthropogenic effects on other elements such as phosphorus.  The chapter also as many implications for policy makers on tracking and managing N fluxes. | Thank you.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | One thing that stood out for me was the implication of the ultimate fate of anthropogenic N inputs to California.  A small percentage (<3%) of new N inputs is discharged to the ocean.  It seems from this budget that much of the new N accumulates within CA in groundwater, reservoirs, urban lands, and natural lands.  Relatively little of the N inputs are suggested to be converted back to N2 and released to the atmosphere.  This leads to the question of how long the storage pools could continue to absorb the N inputs in the future. | This is a great question, but one that is not easily answered and wlll vary on the type of storage.  [NAME] have huge storage potential as does groundwater.  Soils will likely reach saturation at some point and start leaking N to surface water or groundwater.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | Other N budget studies have discussed the problem of the “missing N,” net anthropogenic N inputs (NANI) that are not discharged from watersheds.  The missing N in watersheds is often more than half of the NANI.  Some estimates suggest that the fate of most of the missing N is conversion back to N2 (e.g. [NAME] et. [NAME]. 2002. Biogeochemistry 57/58:267-293).   The CA N budget arrives at the conclusion that most is stored within the system.  I think that the estimate of N2 release in CA depends a lot on the N2:N2O emission ratio from [NAME] (2009).  There is a lot of uncertainty in estimates of N2 production at large spatial scales.  To some extent the ultimate effects of anthropogenic N inputs depend on whether they are converted back to N2 or stored.  The issues of estimating N2 production and relying on [NAME] (2009) might warrant a bit more discussion the chapter 4 or elsewhere in the assessment volume. | The emission of N2 is very difficult to measure.  Instead of calculating it by difference, we attempted to use empirical data to estimate this N flow.  We agree that the [NAME] (2009) data is a relatively small samples.  We discuss the limitations of this approach in the supplemental data tables.  However, even using the relatively high N2 emissions rate from early work in California Agricultural soils, N2 emissions appear to be small compared to leaching losses.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | The supplemental tables contain a lot of important information and highlight areas needing more research or better data reporting (e.g. fertilizer use).  I think it would be good to include the main messages from the supplemental tables in the main messages section for the whole chapter.  Otherwise, some important findings may be overlooked by readers who don’t delve into the supplemental tables. | There is now a main message related to uncertainty, additional text and a figure has been added to the introduction, and the uncertainty terminology has been added to the mass balance tables.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | Main messages section: It seems like there should be some mention of the net N exchanges due to trade of livestock feed or human food.  Also, I was looking for a comparison of net storage of anthropogenic N versus return of anthropogenic N to atmospheric N2. | We can't distinguish anthropogenic N from "natural" N in our calculations.  For example, in natural ecosystems, there is N input from deposition which is predominantly anthropogenic and N input from biological fixation which is "natural".  If we assumed that N2 production occurred proportional to the inputs, then we could do this calculation.
Jordan | [NAME] | Smithsonian Environmental Research Center | 4 | 0 | 0 | 0 | The main messages section didn’t highlight data needs or uncertainties.  These are explored in the supplemental tables.  I think it would be good to include the main messages from the supplemental tables in the main messages for Chapter 4. | We have added a bullet point in the main messages about uncertainty
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.1 | 15 | 299 | Here or elsewhere discuss possible limits of N storage capacity. | We have added a discussion of the limits to storage potential.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.1 | 18 | 350 | CDFA sales amount differs from amount selected for sales in line 328 p. 17.  It is unclear why these differ. | Line 328 is the total fertilizer sales 519 Gg N which is subdivided into [NAME]) and turfgrass (53 Gg N).
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.1 | 18 | 363 | Clarify here that river guages are considered the boundary of the state. | This has been clarified.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.1 | 18 | 366 | Give concentrations for both surface and groundwater to make the comparison.  It is unclear which is 2 mg/L | This has been clarified.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.1 | 19 | 373 | What about timber as another fiber crop? | Based on our land use maps, timber is harvested from natural land and not cropland.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.2 | 0 | 0 | In [NAME]. 4.5, the loss of N as volatilized NH3 seems small.  I guess that is because loss from manure is attributed to the livestock sector of the budget.  Is the volatilization of NH3 from manure the total of that lost before plus after application to cropfields or does the NH3 loss from cropfields include loss from manure after application to fields, while NH3 loss from livestock is loss from manure before application to cropfields.  Manure is considered an input to cropfields so loss from manure after application should be an output from cropfields.  This could use some clarification. | We assumed that all NH3 volatilization from manure occurred in the animal feeding facilities prior to land application.  This has been clarified in section 4.2.6.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.3 | 0 | 0 | Was loss of N due to waste of feed considered, as was loss of N in food wasted by humans? | This is a difficult question, but it represents a relatively large potential error.  We assumed that there was no waste of feed.  Unlike with food for humans, we are not aware of any recent studies on the spoilage of animal feed.  The most widely cited value is from Jordan and Weller (1996) of 10% of non-hay, non-silage crops.  These authors cite Pimentel et al. (1975), but there is not an obvious spoilage fraction in this earlier work.  In California, alfalfa hay and silage corn are the two most important feed crops grown in the state.  These along with other hay/haylage crops account for more than 50% of the feed with the bulk of the remaining feed imported grain corn.  If the spoilage happens before this arrives in California we wouldn't need to account for it.  If it happens in California we may be underestimating the feed import by ~10% or 20 Gg N.  It is also not clear what happens to the spoiled feed. This is clearly an area where more research is needed and we have updated the supplemental data table 11 to disucss the uncertainty in feed spoilage.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.3.2 | 23 | 464 | Therefore, can you conclude that manure application delivers N at rates beyond the demands of the crops? | This section has been rewritten, but we do believe that prior to 2007, manure N was applied at rates beyond the crop demand.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.4 | 0 | 0 | In general it seems odd that humans are not considered a component of urban land.  I think of urban N budgets as dominanted by food N imports to feed humans.  However,  I realize that you decided to separate out humans as a different sector for budgeting. | We realize that separating humans from the urban land and livestock from the cropland is not ideal, but it was the best way to account for all the flows of [NAME]
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.4 | 23 | 468 | Where is the N stored?  In land-fills, structures, soils, or other sinks? | This has been clarified
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.4.2 | 23 | 484 | Can you add citations to literature for both sentences in this line? | There is a table of the field measurements of N2O emisisons from California agricultural soils that is described in section 4.2.8 but is located in a chapter that is still under development .
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.5.2 | 25 | 518 | Why 20% not consumed instead of 27% wasted as cited above in line 512? | Thank you for finding this discrepancy.  We are now consistent between the methods and results section in calculating food waste as the difference between available food N and consumed food N.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.5.2 | 26 | 549 | Can you cite a reference for this 20 Gg N/yr? | We have clarified this and added a reference.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.6.2 | 29 | 613 | Is this for the whole nation or just for California?  If national, then what is it for CA? | We have clarified that this is for California.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.7.2 | 32 | 684-685 | Not clear why these percentages differ from those in line 677. | This has been updated and corrected.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.9.2 | 34 | 736 | Aren't some streams fed by emerging groundwater at some times?  Are all streams fed by surface runoff?  Do all streams loose water due to infiltration into the groundwater? | This assumption was explained in 4.2.10, but we expanded the expalnation here as well. There is exchange between groundwater and surface water, but the net flow is close to zero.  Further, the typical N concentration is similar in groundwater and surface water.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.1.9.2 | 35 | 739 | 36 mg N/L seems like a high concentration for groundwater recharge.  Can you cite direct measurements of concentration to back this up? | Similar to the N2O emissions from California cropland, there will be a table with the actual data for leaching from cropland soils.  However, this table will be located in a chapter that is still under development .
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2 | 0 | 0 | Section 4.2 in general seemed to have some breaks in the text as if there were cutting and pasting errors.  I wondered whether pieces were cut and relocated in editing the document.  Section 4.2 seems to provide the details of the calculations behind the mass balances presented in section 4.1, almost as in extended footnotes.  The supplemental tables are even more like extended footnotes.  I wondered whether text was cut up later and relocated to section 4.2 or the supplemental tables.  The general organizational plan is fine but section 4.2 needs careful proofreading. | We have carefully proofread this section.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.5 | 43 | 927-931 | There seem to be breaks in the text with missing words: "…be 5.0 kg [line break] N yr…"  Also, does "off-farm food outputs" mean waste of food, or uneaten food?  These lines need clarification. | This has been clarified.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.6 | 46 | 1005-1006 | How can milk N be greater than manure N?  The production efficiency would be too high.  Should that be the ratio of milk N to solid manure N? | This section has been removed.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.6 | 46 | 1009-1010 | This equation is confusing as written.  "N" should be specified after "Manure" or "Feed" as it is after "Milk" and "input."  Parts of the equation in parentheses look like they are meant to be multiplied by other variables.  It might be clearer to list the components of milk N and waste N as proportions of feed [NAME]  For example, Milk N=0.25(Feed N); NH3-N emissions=0.285(Feed N); Solid manure N=0.188*(Feed N); Liquid manure N=0.277(Feed N). | This section has been removed.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.7 | 47 | 1022 | The end of this line seems to be missing some words: "…several potential fates, [missing words here]."  The line after that might be the beginning of the next paragraph. | This section has been clarified.  We calculate food waste as the differnce between the per capirta food available in the US and the food conusmption following [NAME] et al. (2001) based on the demography of the population in California.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.7 | 49 | 1055 | I was a bit confused here.  I would expect denitrification to be important when advanced treatment is used but removal of N in solids (i.e. sludge) would be the main process in more conventional treatment. | This has been clarified, but we assumed that the 50% reduction in dissolved N was all converted to N2 by denitrification.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.7 | 49 | 1068 | "no gaseous outputs…"  Wouldn't there be loss of volatilized ammonia? | While some gas losses do occur during the application of treated wastewater to land, we felt that these losses would be minor ; similar to cropland soils where less than 10% of the N input is lost in gaseous.  We also felt that it was better to err on the side of overestimating groundwater N inputs from wastewater because we frequently heard that there are many other sources of groundwater nitrate besides agriculture.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.7 | 50 | 1085 | "assumed all N…leached…" Didn't earlier text say that 91% of N was leached from septic systems? | This has been corrected to accounte for the % of septic N that is a part of the biosolids flow.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.8 | 0 | 0 | Shouldn't this section include something on ammonia emissions from livestock waste before and after application to croplands? | We assumed that all of the ammonia emitted from manure would occur prior to land application.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.8 | 51 | 1106-1108 | I think earlier in the document there was an assumption that fire N emissions were essentially all N2. | This section has been updated.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.8 | 51 | 1118 | Citation of appendix: is that meant to be the supplementary tables?  Also later in the line: "…emissions [from] cropland…" | This table will be located in a chapter that is still under development.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.8 | 52 | 1126-1127 | It should be noted that the accuracy of N2 emission estimates depend on the accuracy of N2O emissions and the accuracy of the assumed N2:N2O ratios from Schlesinger 2009.  I think the N2 emissions estimates are very uncertain. | We agree that the N2:N2O ratios are very uncertain and this is discussed in the supplementary data tables. We have also included a discussion in section 4.1.2.2 of what the range of N2 emissions might be from cropland.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.9 | 52 | 1139 | "…as part of the [missing words?]" | This has been corrected.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.9 | 52 | 1140 | "162 facilities…" clarify what kind of facilities.  The word facilities (line 1138) last refered to food processors.  Are these 162 food processors? | This has been clarified.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.9 | 53 | 1159 | Why the reliance on Beaulac and Reckhow (1982)?  There have been many measurements of export coefficcients since their excellent review in 1982.  The cited [NAME] et al. (2011) study with coefficients developed in CA is a good example.  There are many others.  Maybe export in surface water is too small a part of the budget to warrant extensive consideration of export coefficients? | The differences among watershed are small, and the total N load does not change, but we have updated this approach by using [NAME] et al. (2008) instead of Beaulac and Reckhow (1982).  The former includes the data presented in the latter and provides a more recent and comprehensive review of export coefficients in the U.S.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.9 | 54 | 1169 | By "return" do you mean an input to the state because the N had already been exported past the USGS gauges, which are considered in this budget to be the border of the state?  This may need some clarification. | This has been clarified.
Jordan | [NAME] | Smithsonian Environmental Research Center |  |  |  |  | Note how different the ratio of N2:N2O emission is compared to the assumed ratio of emission from land based on [NAME] (2009). | We agree that the aquatic N2:N2O ratios are much higher than the terrestrial rates reported in Schlesinger (2009).  While there are no aquatic measurements, the database does include an average ratio of 11 for wetland/flooded soils where the ratio is intermediate between the ratio of 1-2 for upland soils and the ratio of 18 we calculate for aquatic systems.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.9 | 54 | 1185 | "Retention" can be a confusing term.  Here it is used just for storage but sometimes it includes N lost in gaseous froms as in line 1195 at the end of the paragraph.  It might be clearer to avoid the term retention here and elsewhere. | We agree that this is a confusing term to anyone outside of the discipline since it includes any storage in the lake as well as any gas loss from denitrification.  We have clarified what we include for storage in reservoirs.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.10 | 0 | 0 | I am having trouble completely understanding the flux of N through groundwater.  Is there a net loss or gain of water to the groundwater?  Leaching of N to groundwater is a major loss from cropland ([NAME]. 4.4b).  Little of the leached N is returned via irrigation ([NAME]. 4.4a), which presumably is irrigation with groundwater.  N concentrations in cropland leachate are high (36 mg N/L, line 739).  Denitrification in groundwater is stated to be negligible but the Green et al. (2008) study cited to support this concluded 50% of the N is denitrified in 31 years.  Given the slow turnover of groundwater, maybe that is a lot of denitrification.  Am I right that irrigation is with groundwater?  If so, how old is irrigation water?  Does groundwater for irrigation contain low amounts of N compared to the water leached to the groundwater?  Will leached N eventually be returned in irrigation water or be denitrified?  What will be the fate of the N leached to groundwater?  I would like to see some more clarification and discussion of N flux through groundwater. | We have revised our groundwater calculations to include a denitrification loss term that we estimate with several different approaches.  The majority of the denitrification comes from exisiting pool of nitrate as opposed to the annual flux.  It is a small fraction (~2%) of a very large pool.  [NAME] pumping for irrigation is the only other loss term and it is relatively small compared to the annual N in recharge. The ultimate fate of N in groundwater is still up in the air.  The three possibilities are extraction for irrigation/drinking water which will continue to grow dirtier, denitrfication, or discharge to surface water.  Given the residence time of most groundwater in the Central Valley (decades to millenia), there is a growing concern that the early inputs to groundwater when N inputs increased exponentially starting in the 1950s will not be completely denitrified and there will be increasing pollution of surface waters from groundwater.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | 4.2.10 | 56 | 1229 | Specify that 1 mg N/L refers to concentration in surface water and cite source of this concentration estimate. | We have clarified where this concentration comes from.
Jordan | [NAME] | Smithsonian Environmental Research Center |  |  | 77 |  | Fig. 4.4a, b.  It might be interesting to include bar graphs for groundwater, surface water, and maybe atmosphere, which are all treated as internal to CA in [NAME]. 4.1. | We include figure 4.4 to highlight the comparison among the 3 land uses. We feel that this is not necessary for the atmosphere, surface water, and groundwater such that tables 4.13, 4.14, and 4.16 convey the necessary information.
Jordan | [NAME] | Smithsonian Environmental Research Center |  |  | 79 |  | Fig. 4.6 arrow for synthetic chemicals should be bold. | This has been fixed.
Jordan | [NAME] | Smithsonian Environmental Research Center |  |  | 80 |  | Fig. 4.7.  N2 and N2O fluxes are 13 in text and 12 in Fig. | This has been fixed.
Jordan | [NAME] | Smithsonian Environmental Research Center |  | Supl. Tables | 18 |  | Supplemental Table 10.  Decline in protein content of 6%: for which crop? | This has been clarified.
Burow | [NAME] | U.S. Geological Survey | 4 | Box 4.X. | 2 | 31-32 | This is a rather broad statement that most aquifers in California have low denitrification rates. The studies cited in the next few lines are all from the San Joaquin Valley or Salinas Valley, hardly representing the extent of the California aquifers. I suggest softening this statement and also noting that there is localized denitrification occurring in all of these aquifers. | We agree that this statement is overbroad, especially given the lack of measurements in most California aquifers.  We have revised this to reflect the fact the where denitrification has been measured in the shallow aquifers of the Central Valley, the rates are often low.  The denitrification rates in the vast majority of California aquifers are not known.
[NAME] | [NAME] | CSU East Bay | 4 | Box 4.X. | 1 | 5 | edit: remove (e.g. energy) | changed
[NAME] | [NAME] | CSU East Bay | 4 | Box 4.X. | 1 | 14 | edit: replace replace "flux of N2 from" with "flux of N2 in" | changed
[NAME] | [NAME] | CSU East Bay | 4 | Box 4.X. | 1 | 16 | edit: replace "studies" with "calculations" | changed
[NAME] | [NAME] | CSU East Bay | 4 | Box 4.X. | 2 | 25 | edit: add  "dissolved" O2 | changed
[NAME] | [NAME] | CSU East Bay | 4 | Box 4.X. | 2 | 29 | edit: omit "particularly" | changed
[NAME] | [NAME] | CSU East Bay |  |  | 2 | 31-37 | Sentence starting with "It is tentatively agreed by most": There are a lot of waffle words in this passage; even so, I wouldn't agree with the main message.  In natural groundwater systems, the water will eventually pass through a low oxygen zone with reduced sulfur species, so deep, old groundwater is likely to be denitrified.  However, in shallow, alluvial groundwater in agricultural settings, episodic irrigation return brings dissolved oxygen into the system, preventing denitrification.  Use of synthetic (vs. organic) fertilizer also makes de-N less likely, by not providing organic [NAME] is therefore more likely for dairy and septic sources of N.  When de-N does occur, it tends to be complete - the microbial population adapts quickly to the amount of NO3 available.  Also, in agricultural settings, groundwater is often pumped out before it is transported to deep, reduced zones of the aquifer. De-N in the vadose zone is likely when there is sufficient residence time, i.e., when irrigation is very efficient or offset in time from fertilizer application. | We agree that denitrification may proceed to completion in certain portions of the aquifer where the conditions are favorable as stated several sentences later.  We also agree that nitrate leaching from manure does provide a carbon source.  However, we are making the point that the exisiting literature largely suggests that in the shallow aquifers of the Central Valley that have been studied, the denitrification rates are on the low side for groundwater.  The low rates may be a function of time scale, such that it may take decades to centuries for the nitrate rich waters to reach reduced portions of the aquifer where denitrification is likely to occur.