bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing and Improving Evapotranspiration and Soil Water Balance of the DSSAT Crop Models
Authors: Sau Federico , Boote Kenneth J. , McNair Bostick W. , Jones James W. , Inés Mínguez M.
Published: July 2010

Crop models have proven to be useful in establishing strategies to improve production under water‐limiting conditions; however, this requires that models have accurate water balance. The objective of this paper was to evaluate various potential evapotranspiration (E0) equations and different ways of partitioning E0 between soil evaporation and crop transpiration within the DSSAT models and particularly the CROPGRO faba bean (Vicia faba L.) model. The default DSSAT E0 options of Priestley–Taylor (PT) and Penman‐FAO (P‐FAO24) as well as several equations based on Penman‐Monteith theory, and an alternative E0 partitioning function were evaluated against measured time‐series data on soil water content, actual evapotranspiration (ET), and crop biomass accumulation of faba bean grown under rainfed conditions in southwest Spain. We conclude (i) the PT option is reasonable but tends to overpredict ET, especially in early season, and its ET predictions are significantly improved when the extinction coefficient is reduced from its default value of 0.85 to 0.5; (ii) P‐FAO24 is the least adequate to simulate ET and biomass; (iii) the Penman–Monteith reference method (PM‐REF based on FAO no. 56 manual) gave good predictions for faba bean but tended to underpredict ET in other locations with soybean [Glycine max (L.) Merr.]; and (iv) dynamic forms of the Penman–Monteith option that use crop‐model–predicted leaf area index and height effects on aerodynamic and surface resistance to water vapor transport also gave good predictions. For this crop and environment, ET prediction accuracy with all the ET options except the PM‐REF was improved using a 0.5 extinction coefficient for net radiation.
The Effects of Soil Fertility and Other Agronomic Factors on Infestations of Root Maggots in Canola
Authors: Dosdall Lloyd M. , Clayton George W. , Neil Harker K. , O’Donovan John T. , Craig Stevenson F.
Published: July 2010

The quantity and availability of soil nutrients can affect the amount of damage inflicted by insect herbivores on their host plants and the ability of infested plants to compensate for herbivory, but this relationship has not been investigated previously in canola agroecosystems. Two field experiments were conducted in central Alberta, Canada, from 1999 to 2001, for a total of five experiment‐years, to determine the relationship between soil fertility (0.5, 1.0, 1.5, and 2.0 times the recommended rates of N, P, K, and S) and root maggot (Delia spp.) (Diptera: Anthomyiidae) infestations in canola (Brassica napus L.). The experiments also investigated effects of cultivar, timing of weed removal, and seeding rate on root maggot infestations. In both experiments, fertilizer rate significantly affected larval damage to taproots, with greatest damage occurring at the two highest levels of soil fertility. Egg deposition, however, was unaffected by the fertility treatments, suggesting that increased canola nutrient levels enhanced survival and development of root maggot larvae. Results of this study support the plant vigor hypothesis, which holds that insect herbivores perform better on plants growing vigorously than on plants under physiological stress. Although the yield advantage from improved plant nutrition at high rates of fertilization was diminished by losses due to greater attack by root maggots, vigorous plants were better able to compensate for damage than plants grown with less fertilizer. Optimal crop management in areas where root maggots are annually responsible for significant economic damage should continue to incorporate recommended fertilizer applications, in view of the enhanced compensatory ability of canola grown in nutrient‐rich soil.
Estimating Site‐Specific Nitrogen Crop Response Functions: A Conceptual Framework and Geostatistical Model
Authors: Hurley T. M. , Malzer G. L. , Kilian B.
Published: July 2010

Confirming the precision agriculture hypothesis for variable‐rate N applications (VRAs) is challenging. To confront this challenge, researchers have used increasingly sophisticated statistical models to estimate and compare site‐specific crop response functions (SSCRFs). While progress has been made, it has been hampered by the lack of a conceptual framework to guide the development of appropriate statistical models. This paper provides such a framework and demonstrates its utility by developing a heteroscedastic, fixed and random effects, geostatistical model to test if VRA can increase N returns. The novelty of the model is the inclusion of site, spatial, treatment, and treatment strip heteroscedasticity and correlation. Applied to data collected in 1995 from two corn (Zea mays L.) N response experiments in south‐central Minnesota, results demonstrate the importance of including site, spatial, treatment, and treatment strip effects in the estimation of SSCRFs. Results also indicate a significant potential for VRA to increase N returns and that these potential returns increase as the area of the management unit decreases. At one location, there was greater than a 95% chance that VRA could have increased profitability if the cost of implementing VRA was less than $14.5 ha−1. At the other location, if implementation costs were less than $48.3 ha−1, there was greater than a 95% chance of increased profitability.
Application of Wood Ash to Acidic Boralf Soils and its Effect on Oilseed Quality of Canola
Authors: Patterson S. J. , Acharya S. N. , Bertschi A. B. , Thomas J. E.
Published: July 2010

Acidic Typic Cryoboralf soils amended with wood ash can raise soil pH and can supplement plant growth by adding minerals and micronutrients. However, presence of other elements in soils such as Cd, S, and Zn can affect plant growth and seed quality. In an earlier paper, we have shown that wood ash applications on Typic Cryoboralf and Typic Cryocrept soils in Alberta, Canada, increased canola (Brassica rapa L.) yield by 72%. In this study, the effect of a single application of 0, 6, 12.5, and 25 t ha−1 (dry weight) wood ash on oilseed quality, based on oil, protein, chlorophyll, and glucosinolate content, was examined over three growing seasons from 1998 to 2000. Seed oil and protein content of ash‐treated plots either increased or remained the same as controls. In contrast, significant increases (p < 0.05) in tissue concentrations of S and seed oil glucosinolates were observed in ash‐amended plots. While these changes remained within acceptable limits for canola, seed oil and tissue quality were lower than the average level found in Canada no. 1 grade canola. During the 3‐yr period, average Zn content of the oilseed was not different from control plots (P > 0.05). Levels of B in ash‐treated soils were different from each other but not from the controls (P < 0.05). Cadmium levels were below detection limits for the instrumentation used (0.08 mg kg−1). These results indicate that use of wood ash on acidic soils has the potential to increase seed oil content but may adversely affect quality of the oilseed produced.
Starter Nitrogen Fertilizer Management for Continuous No‐Till Corn Production
Authors: Niehues Brad J. , Lamond Ray E. , Godsey Chad B. , Olsen Colin J.
Published: July 2010

High residue levels provide excellent erosion control but can result in cool, wet seedbeds creating a situation where starter fertilizer may be beneficial. Research was conducted from 1999 to 2001 evaluating N rates in starter containing N, P, K, and sometimes S; and different starter fertilizer placements for continuous no‐till corn (Zea mays L.). Placements consisted of direct seed contact, dribble over‐the‐row, and a subsurface band (5 cm below and 5 cm to the side of the seed row). Nitrogen rates for direct seed and dribble placements were 11, 22, 45, and 56 kg N ha−1; and 34, 67, 101, and 134 kg N ha−1 for the subsurface placement. Nitrogen was balanced at 168 kg ha−1 on all treatments, including a no‐starter check using broadcast ammonium nitrate at planting. Addition of S in starter was evaluated with subsurface placement. Starter fertilizer, regardless of placement, often increased early season dry matter production and significantly increased grain yields. Increasing N above 22 kg ha−1 in direct seed contact did not increase yields and significantly reduced stands 2 of 3 yr. Stands were unaffected with higher N rates in dribble over‐the‐row and subsurface placements; however, applying N above 11 and 34 kg ha−1, respectively, resulted in little added yield benefit. Inclusion of 11 kg S ha−1 in a subsurface starter fertilizer sometimes increased early season dry matter production, grain yield, and nutrient uptake. Results suggest starter fertilizer is an effective, efficient way of stimulating early growth and improving yields of continuous no‐till corn in Kansas.
Simulating Planting Date Effects on Corn Production Using RZWQM and CERES‐Maize Models
Authors: Anapalli Saseendran S. , Ma L. , Nielsen D. C. , Vigil M. F. , Ahuja L. R.
Published: July 2010

Corn (Zea mays L.) production in northeastern Colorado is constrained by a frost‐free period averaging 11 May to 27 September. For optimization of yield, planting at the appropriate time to fit the hybrid maturity length and growing season is critical. Crop models could be used to determine optimum planting windows for a locality. We calibrated the plant parameters of the Root Zone Water Quality Model (RZWQM) and genetic coefficients for the CERES‐Maize model and validated their performance against experimental data of three corn hybrids varying in days to maturity, planted on three planting dates in 2 yr at Akron, CO, under irrigation. Both models could be calibrated to predict leaf area index, soil water content, crop water use, and yield with similar levels of accuracy. Both models simulated the observed decline in yield with delayed planting date, but CERES‐Maize simulated the yield from the latest planting date much more accurately for all three hybrids than did RZWQM (13% underpredicted by CERES‐Maize; 50% overpredicted by RZWQM). Using the long‐term Akron weather record, the latest planting dates for the short‐, mid‐, and long‐season hybrids to have a 50% chance of achieving a break‐even yield under irrigation were 13 May, 20 May, and 6 May, respectively. Long‐term simulations also revealed that the longer maturity length hybrids lose yield faster than short maturity length hybrids with planting delay. The information generated by either RZWQM or CERES‐Maize can be useful for making both planting and replanting decisions for corn hybrids of varying maturity length in northeastern Colorado.
Remote Sensing of Canopy Dynamics and Biophysical Variables Estimation of Corn in Michigan
Authors: Elwadie M. Eldaw , Pierce Francis J. , Qi J.
Published: July 2010

Remotely sensed data can aid in estimating biophysical variables of corn (Zea mays L.). This study identifies spectral wavelengths, spectral vegetation indices (SVIs), and timing needed for estimating yield and leaf area index (LAI) for corn. Canopy reflectance (460–810 nm range) was measured periodically in 1999 and 2000 within a field study varying N and irrigation management for corn. Corn grain yield was strongly related to canopy reflectance for either individual wavelengths or for SVIs, reaching an optimum (R2 > 0.9) at R5 dent stage in both years. Green reflectance based on simple ratio (green simple ratio index, GSRI) had the highest R2, lowest RMSE, and most consistent slope and intercept between years. In contrast, LAI was best predicted by normalized difference vegetation index (NDVI) (RSME = 0.426) while green normalized difference vegetation index (GNDVI) performed poorly (RMSE = 0.604). Corn grain yield in this study was best predicted at stage R5 using the green simple ratio index.
Using Lidar Remote Sensing for Spatially Resolved Measurements of Evaporation and Other Meteorological Parameters
Authors: Eichinger W. E. , Cooper D. I.
Published: July 2010

Remote sensors are useful tools for making measurements that are not possible with conventional point instruments. We developed methods to obtain spatially resolved latent energy fluxes from Raman water vapor data and the regional virtual potential heat flux from elastic lidar data. The evaporation method is based on Monin–Obukhov similarity theory applied to spatially and temporally averaged data. Latent heat flux estimates were found to be well correlated (R2 = 0.84, slope = 0.98) compared with eddy correlation measurements. The standard error of the flux estimates was 36.5 W m−2 (a 14% root mean square [RMS] difference), which is close to the predicted uncertainty of 15%. A vertically staring elastic lidar was used to obtain a continuous record of the boundary layer height and thickness of the entrainment zone between a soybean [Glycine max (L.) Merr.] and a corn (Zea mays L.) field. The surface heat flux was calculated using the Batchvarova–Gryning boundary layer model. The virtual potential heat flux estimates were found to be well correlated (R2 = 0.79, slope = 0.95) compared with eddy correlation measurements. The standard error of the flux estimates was 21.4 Wm−2 (31% RMS difference between estimates and surface measurements), higher than the predicted uncertainty of 16%. Other parameters such as the Monin–Obukhov length, the stability correction functions, and integral scale can be obtained from lidar data.
Response of Perennial Cool‐Season Grasses to Clipping in the Southern Plains
Authors: Gillen Robert L. , Berg William A.
Published: July 2010

Many forage‐livestock systems in the Southern Plains depend on the use of winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) to support rapid gains of growing beef cattle (Bos taurus L.) from November through May. Complementing these annuals with cool‐season perennial grasses could reduce inputs and soil erosion, but these perennial grasses have not been extensively tested under dryland conditions in this region. We determined the production potential and response to clipping of four Triticeae grasses under dryland conditions on a Grandfield fine sandy loam (fine‐loamy, mixed, superactive, thermic Typic Haplustalf). ‘Barton’ western wheatgrass [Pascopyrum smithii (Rydb.) A. Löve], ‘Luna’ intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia ], ‘Jose’ tall wheatgrass [Elytrigia elongata (Host) Nevski], and ‘Bozoisky‐Select’ Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski] were harvested at either 10 or 15 cm at 30‐, 45‐, or 60‐d intervals. Forage production was different among species in only 1 of 3 yr. Despite above‐average winter and spring precipitation, production declined for all grasses over years, averaging 2270, 1860, and 880 kg ha−1 in 1998, 1999, and 2000, respectively. There were no consistent differences in crude protein or in vitro digestible dry matter concentrations among the wheatgrasses. Crude protein concentration was higher for Russian wildrye in April and June but higher for the wheatgrasses in May. In vitro digestible dry matter was lower for Russian wildrye in May compared with the wheatgrasses. Warm‐season grasses invaded all plots over years. Western wheatgrass was most resistant to invasion. Intermediate and tall wheatgrasses were not adapted to the conditions of this study, and any further research should focus on western wheatgrass or Russian wildrye.
Cropping Sequence Effects of Four Broadleaf Crops on Four Cereal Crops in the Northern Great Plains
Authors: Miller P. R. , Holmes J. A.
Published: July 2010

The productivity and cropping sequence effects of broadleaf crops are not well known within no‐till systems in the semiarid northern Great Plains. We compared productivity of cool‐ and warm‐season broadleaf crops with spring wheat (Triticum aestivum L.), measured cropping sequence effects of broadleaf crops on subsequent cereal crops, and tested if different cereal crops interacted with previous crops. During 1999–2001 we conducted 2‐yr cropping sequence experiments at five sites in Montana under climatic conditions ranging from severe drought to average rainfall. Grain yield and quality were measured for chickpea (Cicer arietinum L.), flax (Linum usitatissimum L.), pea (Pisum sativum L.), proso millet (Panicum miliaceum L.), sunflower (Helianthus annuus L.), and wheat in Year 1. In Year 2, four cereal test crops [barley (Hordeum vulgare L.), durum (Triticum durum L.), spring wheat, and winter wheat] were grown following the Year 1 crops and a fallow control to measure cropping sequence effects. Comparative productivity varied among crops by site, affirming that crop diversity mitigates production risk. Under average rainfall, the cereal test crop yields following flax, pea, and chickpea ranged from 84 to 101% of the fallow control and were greater than that following wheat in seven of nine cases. However, yields following sunflower were equal or less than those following wheat. Under severe drought, cereal test crop yields following broadleaf crops ranged from 21 to 41% of the fallow control and were equal or less than those following wheat. Previous crops affected four cereal test crop species similarly.
Current and Potential U.S. Corn Stover Supplies
Authors: Graham R. L. , Nelson R. , Sheehan J. , Perlack R. D. , Wright L. L.
Published: July 2010

Agricultural residues such as corn (Zea mays L.) stover are a potential feedstock for bioenergy and bio‐based products that could reduce U.S. dependence on foreign oil. Collection of such residues must take into account concerns that residue removal could increase erosion, reduce crop productivity, and deplete soil carbon and nutrients. This article estimates where and how much corn stover can be collected sustainably in the USA using existing commercial equipment and estimates costs of that collection. Erosion constraints to collection were considered explicitly, and crop productivity and soil nutrient constraints were considered implicitly, by recognizing the value of residues for maintaining soil moisture and including the cost of fertilizer to replace nutrients removed. Possible soil carbon loss was not considered in the analysis. With an annual production of 196 million Mg of corn grain (∼9.2 billion bushels), the USA produces 196 million Mg of stover. Under current rotation and tillage practices, ∼30% of this stover could be collected for less than $33 Mg−1, taking into consideration erosion and soil moisture concerns and nutrient replacement costs. Wind erosion is a major constraint to stover collection. Analysis suggests three regions of the country (central Illinois, northern Iowa/southern Minnesota, and along the Platte River in Nebraska) produce sufficient stover to support large biorefineries with one million Mg per year feedstock demands and that if farmers converted to universal no‐till production of corn, then over 100 million Mg of stover could be collected annually without causing erosion to exceed the tolerable soil loss.
Phosphorus and Sediment in Runoff after Core Cultivation of Creeping Bentgrass and Perennial Ryegrass Turfs
Authors: Kauffman Gordon L. , Watschke Thomas L.
Published: July 2010

Limited research has been conducted on nutrient and sediment loss in runoff from mechanically disturbed turfgrass sites. This study assessed the effect of turfgrass species after core cultivation and fertilization on total dissolved P (as PO43−) loss and sediment transport. Six sloped (9–11%) plots (18.9 by 6.4 m or 121 m2) consisting of either creeping bentgrass (Agrostis palustris Huds.) or perennial ryegrass (Lolium perenne L.) were maintained as golf course fairways. Composite runoff samples were collected after simulated rainfall (152 mm h−1) and sediment yield was determined. Phosphate‐P concentrations in runoff were equal to or lower than previously reported losses from turfgrass sites and were highest, 6 mg L−1, within 24 h after fertilizer application. The initially high PO43−–P concentrations were temporary and decreased with time. Phosphate‐P export was significantly higher for perennial ryegrass than creeping bentgrass on one occasion following fertilization and simulated rainfall. Sediment loading did not differ between turfgrass species and was considered low, never exceeding 0.35 kg ha−1. As a consequence, the initially high but temporary PO43−–P concentrations found in runoff, and the minimal erosion, should not be considered a serious threat to surface waters after core cultivation.
Carbon Storage in Soils of the North American Great Plains: Effect of Cropping Frequency
Authors: Campbell C. A. , Janzen H. H. , Paustian K. , Gregorich E. G. , Sherrod L. , Liang B. C. , Zentner R. P.
Published: July 2010

Summer fallow (fallow) is still widely used on the North American Great Plains to replenish soil moisture between crops. Our objective was to examine how fallowing affects soil organic carbon (SOC) in various agronomic and climate settings by reviewing long‐term studies in the midwestern USA (five sites) and the Canadian prairies (17 sites). In most soils, SOC increased with cropping frequency though not usually in a linear fashion. In the Canadian studies, SOC response to tillage and cropping frequency varied with climate—in semiarid conditions, SOC gains under no‐till were about 250 kg ha−1 yr−1 greater than for tilled systems regardless of cropping frequency; in subhumid environments, the advantage was about 50 kg ha−1 yr−1 for rotations with fallow but 250 kg ha−1 yr−1 with continuous cropping. Specific crops also influenced SOC: Replacing wheat (Triticum aestivum L.) with lentil (Lens culinaris Medikus) had little effect; replacing wheat with lower‐yielding flax (Linum usitatismum L.) reduced SOC gains; and replacing wheat with erosion‐preventing fall rye (Secale cereale L.) increased SOC gains. In unfertilized systems, cropping frequency did not affect SOC gains, but in fertilized systems, SOC gains often increased with cropping frequency. In a Colorado study (three sites each with three slope positions), SOC gains increased with cropping frequency, but the response tended to be highest at the lowest potential evaporation site (where residue C inputs were greatest) and least in the toeslope positions (despite their high residue C inputs). The Century and the Campbell et al. SOC models satisfactorily simulated the relative responses of SOC although they underestimated gains by about one‐third.
A Structured Procedure for Assessing How Crop Models Respond to Temperature
Authors: White J. W. , Hoogenboom G. , Hunt L. A.
Published: July 2010

Crop simulation models are widely used to analyze temperature effects on crop growth, development, and yield. Unfortunately, temperature responses of models often are not examined critically to ensure that a model is appropriate for a given research application. This paper describes a procedure for assessing how models respond to temperature. The procedure treats major processes in a balanced fashion but does not require access to source code. The results are easily interpretable by nonmodelers and readily documented and employed with different models. Sensitivity analyses are run using standardized conditions of nonlimiting water and N with regimes of constant mean temperatures from 3 to 40°C and daily range of 10°C. Daily model outputs define responses that are grouped in seven categories: crop mass (including economic yield), phenology, reproductive growth, canopy development, root growth, resource use efficiency, and water balance. To avoid interactions of duration of life cycle with growth, several responses are assessed before partitioning to reproductive growth reduces total aboveground biomass. Emphasis is on graphical analysis of individual variables vs. mean temperature, but cardinal temperatures and a response index are also estimated. When applied to the CSM‐CERES‐Sorghum and CSM‐CROPGRO‐Drybean models, the procedure readily identified differences in temperature adaptation of the two crops. Various examples were found where modeled responses appeared to differ from data from field or controlled‐environment studies. The proposed procedure will require adjustments for specific situation but provides a foundation for assessing modeled responses to temperature in a structured and reproducible fashion.
Nitrogen Application to Soybean at Early Reproductive Development
Authors: Barker Daniel W. , Sawyer John E.
Published: July 2010

Nitrogen application during soybean [Glycine max (L.) Merrill] reproductive stages has the potential to increase soybean productivity. The objective of this study was to determine the impact of N fertilizer applied to the soil at the beginning pod growth stage on soybean yield and grain quality. Additional objectives were to study alternative N fertilizer and application practices that might enhance soybean use of applied N. A field study was conducted at five locations in Iowa during 1999 and 2000. Nitrogen treatments were urea and polymer‐coated urea broadcast and subsurface band placed between the rows at 45 and 90 kg N ha−1 and a no‐N control. The study showed few, small, and inconsistent effects of N material, placement, and rate on grain yield and quality components at individual sites or when combined across individual sites. There were no significant effects on grain yield, with only a 39 kg ha−1 increase from applied N. Grain protein, oil, and fiber concentrations were the same with or without N application. Aboveground plant dry matter (DM) at the R6 growth stage was greater with the higher N rate, but plant DM with N application was lower than the no‐N control. Nitrogen concentration in plant DM was significantly increased with applied N. In conclusion, N application increased N concentration in R6 soybean plants, but N rate and alternative application practices had no positive effect on plant DM, grain N concentration and removal, grain yield, or grain quality components. It was concluded that growers should not consider fertilizer N applied to soil during early reproductive stages as a method to increase soybean yield or grain quality.
Corn Grain Yield, Early Growth, and Early Nutrient Uptake as Affected by Broadcast and In‐Furrow Starter Fertilization
Authors: Kaiser D. E. , Mallarino A. P. , Bermudez M.
Published: July 2010

In‐furrow starter fertilization for corn (Zea mays L.) is being preferred to alternative starter application methods by farmers in the U.S. Corn Belt. This study assessed corn grain yield, early growth (V5 to V6), and early P and K uptake responses to in‐furrow P–K starter fertilization with or without broadcast P–K fertilization for 2‐yr corn–soybean [Glycine Max (L.) Merr.] rotations. Sixteen trials were conducted on Iowa fields managed with no‐till or chisel‐plow tillage. Soil‐test P (STP) was 5 to 77 mg P kg−1 (Bray‐P1), and soil‐test K (STK) was 88 to 237 mg K kg−1 (ammonium acetate). Treatments replicated four times were a control, 3–8–15 (N–P–K) liquid starter at 5 to 7 kg P ha−1 and 10 to 14 kg K ha−1, granulated P–K fertilizer broadcast at 49 to 66 kg P ha−1 and 112 to 140 kg K ha−1, and broadcast plus starter. Nitrogen was applied across all treatments. Fertilization increased grain yield at nine sites (0.80 to 2.11 Mg ha−1). Starter fertilization produced less yield than broadcast fertilization at five sites (0.30 to 1.48 Mg ha−1 less), four of which tested low in STP (≤15 mg P kg−1). Starter fertilization in addition to broadcast fertilization did not increase yield further at any site. Starter fertilization increased corn early growth and P and K uptake more than broadcast fertilization did at most sites. In‐furrow starter P–K fertilization for corn is not an effective practice when applied in addition to 2‐yr broadcast P–K fertilization rates for corn–soybean rotations.
Self‐Seeding Winter Cereal Cover Crops in Soybean
Authors: Singer Jeremy W. , Kohler Keith A. , McDonald Paul B.
Published: July 2010

Soil protection and nutrient scavenging benefits of cover crops have been widely reported. Nevertheless, adoption of cover crops in agronomic farming systems is low. Cover crop systems that do not require annual planting may increase adoption. The objectives of this study were to compare self‐seeding and competitiveness of winter wheat (Triticum aestivum L.), triticale (x Triticosecale Wittmack), and rye (Secale cereale L.) using different planting configurations and management options while growing concurrently with soybean [Glycine max (L.) Merr.]. Cover crops were planted with two or four 19‐cm rows between each 76‐cm soybean row. A no‐cover crop check treatment was also included for comparison. Cover crop species and species × management system interactions were not significant for seed production or soybean seed yield. Averaged across management system, cereals produced 10 656 and 4051 seeds m−2 in 2004 and 2005. The two‐row band, no‐chop treatment (2RBNC) produced the most seed (20 347 and 14 511 seeds m−2) in 2004 and 2005, but also lowered soybean yield the greatest (45 and 40%). The four‐row treatment with a late glyphosate band (4RLB) was the least competitive and yielded 3114 and 3717 kg ha−1 compared to 4019 and 4391 kg ha−1 in the check. Wheat had the greatest self‐seeding, averaging about 31% of the original plant density. The four‐row treatment without a glyphosate band (4RNB) could be used in organic production systems, although additional research is needed to develop less competitive self‐seeding systems for conventional production systems.
Dynamic Cropping Systems: Increasing Adaptability Amid an Uncertain Future
Authors: Hanson J. D. , Liebig M. A. , Merrill S. D. , Tanaka D. L. , Krupinsky J. M. , Stott D. E.
Published: July 2010

Future trends in population growth, energy use, climate change, and globalization will challenge agriculturists to develop innovative production systems that are highly productive and environmentally sound. Furthermore, future agricultural production systems must possess an inherent capacity to adapt to change to be sustainable. Given this context, adoption of dynamic cropping systems is proposed to meet multiple agronomic and environmental objectives through the enhancement of management adaptability to externalities. Dynamic cropping systems are a form of agricultural production that relies on an annual strategy to optimize the outcome of (i) production, (ii) economic, and (iii) resource conservation goals using ecologically‐based management principles. Dynamic cropping systems are inherently complex, possessing larger crop portfolios and greater crop diversity and sequencing flexibility as compared with monoculture and fixed‐sequence cropping systems. Greater crop diversity and sequencing flexibility within dynamic cropping systems may result in reduced weed and disease infestations, greater nutrient‐ and precipitation‐use efficiency, decreased requirements of exogenous inputs, and lower production risk. The multiple interactions among management components of dynamic cropping systems demand greater management intensity than monoculture and fixed‐sequence cropping systems. Further development of dynamic cropping systems is important for managing crop production systems in a sustainable manner. These systems can ultimately assist land managers to develop new and improved land‐use strategies to the benefit of generations to come.
Hillslope Variability in Corn Response to Nitrogen Linked to In‐Season Soil Moisture Redistribution
Authors: Schmidt John P. , Hong Nan , Dellinger Adam , Beegle Doug B. , Lin Henry
Published: July 2010

Spatial variability of corn (Zea mays L.) yield within a field is often identified as the primary criterion to justify site‐specific nitrogen (N) management; yet, observed yield variability may be unrelated to N supply. The objective of this study was to characterize the spatial variability in economic optimum N rate (EONR) for corn. Ten plot locations were selected in 2005 along a 300‐m toposequence of a field in central Pennsylvania. At each location, two replications of six N treatments (0, 56, 112, 168, 224, and 280 kg N ha−1) were broadcast applied at planting as NH4NO3. Soil water content (0‐ to 90‐cm depth) was recorded approximately weekly at each location between 5 June and 2 September. The quadratic‐plateau response was selected as the most appropriate grain yield response function for 9 of 10 locations and for the field‐mean response. The EONR ranged from 47 to 188 kg N ha−1 among the nine locations, whereas EONR for the mean response was 137 kg N ha−1. At four of nine locations, observed EONR deviated from field‐mean EONR by 40 to 50 kg N ha−1. The relationship between EONR and the change in soil profile water content (0–90 cm) between 30 June and 25 July (representing the driest and wettest soil conditions early in the growing season) was the defining relationship in this study (r2 = 0.92; P > F < 0.0001). Successful site‐specific N management depends on an evaluation of the spatial variability in EONR and the corresponding causal factors.
Nature of the Reactions of Monocalcium Phosphate Monohydrate in Soils: III. Studies with Metastable Triple‐Point Solution
Authors: Lindsay W. L. , Lehr J. R. , Stephenson H. F.
Published: July 2010

Metastable triple‐point solution (MTPS), the solution saturated with respect to Ca(H2PO4)2·H2O and CaHPO4·2H2O, was reacted with a series of soil samples in order to simulate the initial reaction zone that occurs adjacent to a dissolving granule of superphosphate in soil.

As this acidic solution (initially pH 1.48) contacted successive soil increments, appreciable quantities of Al, Fe, Mn, K, and Ca were dissolved or exchanged from the soil. The solution formed during this series of reactions gradually became supersaturated with respect to certain Ca and Fe‐Al phosphate compounds. As the pH rose above 2.3, more rapid precipitation of phosphates occurred and was accompanied by the simultaneous removal of Ca, Al, Fe, and K from solution. The crystalline compound, CaHPO4·2H2O, CaHPO4, and H6K3Al5(PO4)8·18H2O, were identified petrographically and by X‐ray as precipitates that later formed in solutions filtered during the reaction sequence. The results are compared to those of a previous study in which soil was reacted with TPS (the stable equilibrium solution saturated with respect to Ca(H2PO4)2·H2O and CaHPO4).
Degradation of Structure of Yolo Loam by Compaction
Authors: Vomocil J. A. , Flocker W. J.
Published: July 2010

Field compaction of Yolo loam soil over 6 years resulted in marked changes in several physical characteristics of the soil. The degradation of structure was more than temporary in that air drying, crushing, and sieving of the soil did not remove all evidence of the deliberate compaction. Remolded briquets of crushed and sieved soil from the plots receiving supplemental compactive effort had a modulus of rupture of 3,300 millibars, while briquets of soil from plots receiving only the minimum traffic necessary for cultivation over the 6‐year period had a modulus of rupture of 1,200 millibars. The water stability of aggregates by wet sieving was reduced from 9% to 2%. Unconfined compressive and tensile failure tests on remolded samples showed that the soil from compacted plots reconsolidated after wetting and drying into stronger casts. Increased mechanical strength of remolded soil from the compacted plots was demonstrated by compression and penetrability measurements. The changes in strength were taken as evidence of reduction of water stability of soil aggregates by compaction. A residual effect of the compaction was definitely detected.
Effect of Method of Incorporation of Zinc in Fertilizer on Zinc Uptake and Yield of Pea Beans (Phaseolus Vulgaris)
Authors: Ellis B. G. , Davis J. F. , Judy W. H.
Published: July 2010

Incorporation of either ZnO or ZnSO4 into fertilizer reduced the water solubility of Zn, the Zn uptake by pea beans, and the final yield as compared to the same rate and carrier of Zn hand mixed with fertilizer at planting time. Zn‐EDTA chelate remained 100% water‐soluble when coated on the fertilizer granule in conjunction with MnSO4; however, it was only 40% water‐soluble if coated in conjunction with MnO, and only 10% water‐soluble if incorporated into the fertilizer granule. The reduced water solubility was reflected in the uptake of Zn and the yield of pea beans.
Seasonal Variation in Soil Nutrients Under Six Rocky Mountain Vegetation Types
Authors: Weaver T. , Forcella F.
Published: July 2010

Soils under vegetation types dominated by Festuca idahoensis, Artemisia tridentata, Populus tremuloides, Pseudotsuga menziesii, and Abies lasiocarpa were sampled at monthly intervals during 1974 and 1975 to determine the magnitude of seasonal variation in nutrient availability. Results may be summarized by expressing minimal values observed in 1974 as a percentage of maximum values: nitrate 27%, ammonium 30%, phosphorus 45%, potassium 65%, calcium 77%, magnesium 82%, sodium 60%, and organic matter 80%. Nutrients were most available in the early fall (September — October) and least available at midwinter (January — April). Rates of change in nutrient availability were smallest in winter and spring. Seasonal variation in Abies forests was notably less than in other vegetation types.
Nitrous Oxide Production and Reduction during Denitrification as Affected by Redox Potential
Authors: Letey J. , Valoras N. , Focht D. D. , Ryden J. C.
Published: July 2010

Nitrous oxide evolution from soils may contribute to partial destruction of the ozone layer in the stratosphere. Knowledge of factors affecting the N2O/N2 evolution ration from soils is important in properly assessing the hazard associated with N2O evolution. Previous investigations demonstrated that air‐dry soils incubated in the laboratory under conditions to cause denitrification had an initial high N2O/N2 evolution ratio which rapidly decreased and approached zero. It was not possible to determine whether the observed time effect on the gaseous evolution was related to concurrent changes in the redox potentials in the soil. Experiments were conducted to measure the production, reduction, or both, of N2O at various redox potentials in incubation containers. Equal weights of soil and KNO3 solution were added to the incubation containers which were placed in a temperature‐controlled waterbath shaker. The container was evacuated and refilled with helium. Small amounts of oxygen were periodically injected into the container to achieve the desired redox potential. Gas samples were withdrawn daily and analyzed for N2O, N2, O2, and CO2 on a gas chromatograph. Nitrate‐nitrogen concentrations in solution were analyzed at the beginning and end of the incubation and were found to range from approximately 200 to 400 mg/liter during the incubation. There was essentially no denitrification at redox potentials of 300, 350, or 400 mV as determined by gas analyses and measurement of nitrate‐nitrogen. When no oxygen was added to the system, the redox potential decreased and poised at approximately 200 mV throughout the incubation. At a redox potential of 200 mV, the N2O concentration increased, reaching a maximum at approximately 3 days, and decreased thereafter, reaching zero in 5 to 7 days after initiation of incubation. Thus, the previously observed time dependency of N2O evolution was repeated in these experiments and the results cannot be attributed to change in redox potential with time. The data also demonstrate that N2O can be reduced more rapidly than NO3‐, even in the presence of relatively high NO3‐ concentrations.
The Mechanism of Copper(II) Binding by Humic Acid: An Electron Spin Resonance Study of a Copper(II)—Humic Acid Complex and Some Adducts with Nitrogen Donors
Authors: Boyd Stephen A. , Sommers Lee E. , Nelson Darrell W. , West Douglas X.
Published: July 2010

Electron spin resonance (ESR) spectroscopy was used to study the mechanism of Cu2+ binding by humic acid (HA) extracted from a Chalmers silt loam soil. The Cu‐HA complex and some adducts with nitrogen donors were examined. The ESR data presented showed that the addition of pyridine (py) and 1,10‐phenanthroline (phen) to the Cu‐HA complex resulted in the substitution of coordinated H2O ligands by the nitrogen donor ligands without displacement of HA oxygen donor ligands also coordinated to the Cu2+ center. The addition of a more basic nitrogen donor, ethylenediamine (en), resulted in the displacement from Cu2+ of both coordinated H2O ligands and HA oxygen donors, forming Cu(en)22+. The g‖ and A‖ values obtained for the py and phen adducts revealed that there were two HA oxygen donors coordinated equatorially to the Cu2+ center in the original Cu‐HA complex. The characterization of the adducts with phen and en was consistent with the formation of a Cu2+ chelate in the original Cu‐HA complex, where the two equatorial Cu‐HA oxygen bonds would occupy cis‐ positions. The crystal field strength of HA oxygen donor ligands coordinated to the Cu2+ center was stronger than that of H2O.
Effect, and Statistical Evaluation, of Soil Sterilization on Aniline and Diuron Adsorption Isotherms
Authors: Dao T. H. , Marx D. B. , Lavy T. L. , Dragun J.
Published: July 2010

A laboratory study evaluated the effects of six treatments on the adsorptive capacity of three soils for a labile chemical, aniline hydrochloride (amino‐benzene‐HCl), and a relatively stable one, diuron (3‐3,4‐dichlorophenyl‐1,1‐dimethylurea). Detailed statistical procedures were outlined for presenting the reliability of the experimental results and were applied to compare the effects of air drying, oven drying, the addition of propylene oxide, autoclaving, cobalt‐60 irradiation, and moist preincubation on aniline‐HCl and diuron adsorptions on soil.

Oven drying soil samples at 90°C for two 24‐h cycles resulted in increased aniline‐HCl adsorption but had no effect on diuron adsorption. Propylene oxide, inducing a soil pH change, decreased the adsorption of aniline‐HCl. It caused a general increase in diuron adsorption in the three soils due to the high amount of residue remaining in the treated soil. Although autoclaving and cobalt‐60 irradiation were effective methods of soil sterilization, both treatments decreased the adsorptive capacity of the soil samples. The above four treatments modified soil properties and altered the adsorption of organic chemicals on soil, when compared to the air‐dried and preincubated controls. Care must be exercised in the interpretation of adsorption data obtained using pretreated soil samples. Adsorption measurements should be taken preferably during a short period subsequent to soil‐solvent mixing, before enhanced microbial activity could take place in air‐dried soil samples.
Fluorite Precipitation in a Calcareous Soil Irrigated with High Fluoride Water
Authors: Tracy P. W. , Robbins C. W. , Lewis G. C.
Published: July 2010

Lysimeters filled with Freedom silt loam soil (fine‐silty, mixed, mesic, Xerollic Calciorthids) were irrigated with geothermal well water from south central Idaho. The water contained 7 mg F/L. Alfalfa (Medicago sativa L.) was grown in the lysimeters and the water was applied at a rate to give either a 0.30 or 0.15 leaching fraction. After irrigating the 1.0 m deep soil samples for 600 d, over 98% of the added F remained in the soil. Soil extract and lysimeter leachate analysis showed that fluorite precipitation was occurring in the upper profile, but only after another fluoride adsorption mechanism was saturated and the fluoride and calcium ion activities exceeded the CaF2 ion activity product. The F concentration in the upper profile extracts exceeded 20 mg F/L and with the additional high F water irrigation, the soluble F would be expected to leach deeper in the soil. Under field conditions the F would be expected to eventually move into the groundwater with continued irrigation with high F water.
Effect of Ionic Strength and Anions on Zinc Adsorption by Two Soils
Authors: Shuman L. M.
Published: July 2010

It is important to assess the effects of ionic strength and type of anion when studying adsorption of metals on soils and soil components because the background salt may complex metals and compete for adsorption sites. Four experiments were carried out to determine the effect of ionic strength and anions on Zn adsorption by two soils and to determine the effects of these two factors on the pH‐adsorption relationships. Zinc adsorption using NO‐3 at ionic strengths of 0.005 and 0.01 mol L−1 was the same but the adsorption at 0.05 and 0.1 mol L−1 was lower than for the other ionic strengths. The SO2‐4 ion produced higher adsorption than NO‐3 or Cl‐ ions which yielded the same isotherm at pH 6. Increased ionic strength had similar effects at all pH levels studied. The three anions had no effect on the pH‐adsorption curves which were exactly the same within a soil type. Plotting the activity of the free Zn in the systems vs. adsorbed Zn gave much the same results as when concentration data were used. In general, ionic strength and anions had no influence on the shape of the isotherms, showing that the same relationships would be found regardless of ionic strength or anion. The absolute values of the adsorption maxima were different in some cases.
Urea and Manure Effects on Soil Nitrogen and Corn Dry Matter Yields
Authors: Xie Rongjing , MacKenzie A. F.
Published: July 2010

Fresh (FC) and composted (CC) cow (Bos taurus) manures, liquid hog (Sus scrofa domesticus) manure (HM), and urea (U) were applied as N sources for silage corn (Zea mays L., hybrid W844) production on a Chicot (Hapludalfs) and a St. Benoit soil (Eutrochrepts) at rates of 0 to 240 N ha−1. Soil NO3‐N levels were significantly increased while soil NH4‐N levels were only temporary increased by N additions. Highest NO3‐N levels were noted 30 and 60 d (June and July) after N applications for the St. Benoit and the Chicot soils respectively. Hog manure resulted in more NO3‐N compared with FC and CC manures. One to 5 kg manure‐N was found to be equivalent to 1 kg of urea‐N in terms of increasing soil NO3‐N levels at the end of growing season. Differences between surface spreading or incorporating of manures on corn dry matter yields (DMY) and N uptake were not significant. Nitrogen uptake increased with increases in N application rates and was higher with HM than with CC or FC manures. Regression between DMY or N uptake and N application rates showed linear relationships with manure‐N and quadratic relationships with urea‐N. In 1984, 1 to 4 kg manure‐N resulted in similar corn DMY as 1 kg urea‐N. Cumulative effects of treatments on yields and on nutrient uptake observed in second and third years were greater on the St. Benoit soil than on the Chicot soil.
Clinoptilolite in South Texas Soils
Authors: Ming Douglas W. , Dixon Joe B.
Published: July 2010

Clinoptilolite, Cax(Na,K)6‐2x{Al6Si30O72}·24H2O, frequently has been recognized in Cenozoic volcanogenic sedimentary rocks; however, its occurrence in soils has received little attention. In the course of this study, clinoptilolite was identified in calcareous soils derived from volcanic‐rich sediments of the Catahoula Formation in south Texas. The mineralogical properties of clinoptilolite were characterized by x‐ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe analysis, and analysis of exchangeable cations. About 2 to 5% clinoptilolite by weight was found in the A and B horizons and concentrations progressively increased with depth to as high as 20% in the C horizons. No differences in the zeolite structural framework or Si/Al atomic ratio were detected throughout the soil profiles examined. Unlike Na‐ and K‐saturated clinoptilolites in sedimentary deposits, clinoptilolite in these calcareous soils was predominantly Ca‐saturated. Clinoptilolite was concentrated in the silt fractions as clusters of closely spaced laths that were 1 to 2 µm in thickness and 5 to 10 µm in length. Aggregates of the crystal plates and laths were as large as 50 to 60 µm in diam. Clinoptilolite in these soils appeared to have been inherited from zeolite‐rich, tuffaceous parent materials. The smooth, angular, euhedral nature of the clinoptilolite crystals indicated their relative stability. Exceptional, slightly pitted and fractured crystals were observed in the A and B horizons indicating minimal weathering.