bluuebunny/crossref_metadata_2025_split huggingface dataset:
Line‐Source Sprinkler Systems for Experimentation with Sprinkler‐Applied Nitrogen Fertilizers
Authors: Lauer D. A. 
Published: July 2010

AbstractA triple line‐source system was developed and evaluated as an alternative field plot design that allows superimposition of a continuous gradient of sprinkler‐applied N within uniform sprinkler irrigation. Two outer laterals are used to apply water only while a third lateral centered between the outer laterals is used to apply water plus injected N fertilizer. This layout provides duplication of the N gradient on each side of the center lateral. Equality of slopes and intercepts of linear regressions individually fit on both sides of the center lateral indicates good duplication and symmetry of the N gradient about the center lateral. The main disadvantage of the technique is the potential statistical bias stemming from the nonrandom treatment arrangement. Having good symmetry of response variables across the N source line indicates lack of statistical bias associated with nonrandom treatments because of the low probability that unknown gradients coincident with the N gradient would exist at the same magnitude at 180 degrees to each other. The technique is probably best suited for single independent variable investigations which exhibit large treatment differences relative to potential bias. In using this or any other continuous variable designs, the main inherent disadvantage of nonrandom treatment arrangement must be balanced against the main inherent advantages of smaller plot areas associated with the elimination of border areas and considerable savings of other research resources.
Soil Properties in a Mesquite‐Dominated Sonoran Desert Ecosystem
Authors: Virginia Ross A. , Jarrell W. M. 
Published: July 2010

AbstractSoil was collected in 30‐cm depth increments to 90 cm from beneath Prosopis glandulosa Torr. var. glandulosa (L. Benson) M. C. Jtn. (mesquite) and from the nonvegetated area between mesquite trees in a phreatophytic stand in the Sonoran Desert of southern California. Total N, NO‐3‐N, NH+4‐N, organic C, NaHCO3‐extractable PO3‐4‐P, and saturation extract K+ were significantly higher beneath mesquite, while Na+ and Cl‐ were significantly higher between mesquite trees. Differences in pH, the osmotic potential of saturation extracts, saturation percent, and SO2‐4‐S were nonsignificant. Large amounts of N (1.68 g kg−1 of soil) have accumulated in the surface 30 cm beneath mesquite. This N most likely had been symbiotically fixed by mesquite. Over 20% of the N in this ecosystem occurred as NO‐3. This unusual NO‐3 accumulation was possible since leaching and denitrification were probably limited by aridity. The Na+ adsorption ratio of saturation extracts (SAR), 0–30 cm, was significantly lower at the center of tree canopies (7.9) than in soil between trees (17.3) and also was lower than the groundwater (12.7). Foliar analysis indicated mesquite was excluding Na+. Consequently, the decomposition of mesquite litter produced a soil with a lower SAR than the nonvegetated soil. Soil N was determined at six additional Sonoran Desert sites. Nitrogen accumulation beneath mesquite was related to soil texture and water regime. Total soil N was highest on low relief phreatophytic sites with high clay content (1.34 g of N kg−1 of soil, 0–15 cm) and lowest in aeolian sand dunes (0.18 g of N kg−1 of soil, 0–15 cm). Woody legumes such as mesquite, through the accumulation of symbiotically fixed N and the accretion of other nutrients in the surface beneath their canopies, may be important in maintaining the long‐term productivity of some desert ecosystems.
The Effect of Suspended Solids in Wastewater on Soil Hydraulic Conductivity: II. Vertical Distribution of Suspended Solids
Authors: Vinten A. J. A. , Mingelgrin U. , Yaron B. 
Published: July 2010

AbstractA method for labelling of suspended solids in sewage effluent is used to trace the distribution of deposited solids in three soils following leaching with effluent. This distribution is related to the effect of sewage effluent application on the soil hydraulic conductivity. A sand, a sandy loam, and a loessial silt loam were studied. The reduction in relative hydraulic conductivity was greatest for the silt loam. This was due to accumulation of solids at the soil surface. In the sand little deposition of solids in the soil and little change in hydraulic conductivity occurred. Results indicate that with proper management sewage effluent can he used for irrigation without causing problems due to lack of soil permeability.
A General Soil Volume Change Equation: II. Effect of Load Pressure
Authors: Giráldez Juan V. , Sposito Garrison 
Published: July 2010

AbstractThe two‐parameter model of soil volume change developed by the authors is extended to account for the load pressure effects expected in the upper 2 m of a soil profile. The extended model equation is based on two principal assumptions: (i) that only the dry soil pore volume and the air‐entry water content are affected significantly by changes in load pressure, and (ii) that changes in the dry soil pore volume with load pressure are proportional. These assumptions require only one additional adjustable parameter in the extended model, the soil bulk modulus. The extended model describes available data on soil volume change under load pressure very well.
Influence of Velocity on Hydrodynamic Dispersion during Unsteady Soil Water Flow
Authors: Bond W. J. , Smiles D. E. 
Published: July 2010

AbstractA recent solution of the equation for hydrodynamic dispersion during unsaturated, unsteady soil water flow is extended to include the velocity dependence of the dispersion coefficient. The effect of this velocity dependence on the solute concentration profiles is illustrated for the case of horizontal constant concentration absorption of water by an initially dry soil. The application of the theory to other soil water flow situations, including constant flux absorption, is also examined.
Fixation Kinetics in Potassium–Iron—Orthophosphate Systems
Authors: Kim Y. K. , Gurney E. L. , Hatfield J. D. 
Published: July 2010

AbstractThe rate of removal of phosphate and potassium from solution was studied by contacting an iron‐impregnated, cation exchange resin with solutions of monopotassium orthophosphate in concentrations of 0.05 to 0.25M and with atomic ratios Fe:P from 0.25 to 4.0. The removal of both P and K from solution followed first‐order reaction models for all experimental conditions, the K being removed faster than the P. The rate constants, k1 and k2, for P and K removal, respectively, increased with the ratio Fe:P and were affected to a lesser extent by the initial concentration of KH2PO4. The concentration of Fe with time agreed with a consecutive first‐order reaction mechanism involving liberation, k3, and precipitation, k4, of Fe. The rate constants were evaluated by nonlinear regression analysis, and the reaction model represents the data well. The rate constants, k3 and k4, increased with the ratio Fe:P, whereas increasing the initial concentration of KH2PO4 caused k3 to increase and k4 to decrease. The precipitate was prepared in 1M KH2PO4 solution and identified as potassium iron phosphate, K[Fe(OH)1.33]3·(H2PO4)6·2H2O, by chemical and x‐ray analysis.
Effects of Nitrogen and Phosphorus Application Method and Nitrogen Source on Winter Wheat Grain Yield and Leaf Tissue Phosphorus
Authors: Leikam D. F. , Murphy L. S. , Kissel D. E. , Whitney D. A. , Moser H. C. 
Published: July 2010

AbstractThe positive effect of placing N (especially NH+4‐N) with P on crop growth has been demonstrated many times in short‐term greenhouse studies. Under field conditions, however, the effect has not been well defined. The present objective was to evaluate N and P placement methods on the P nutrition and final grain yield of wheat (Triticum aestivum L.) grown in the field and greenhouse. Anhydrous ammonia (NH3), urea‐ammonium nitrate solution (UAN), and sodium nitrate (SN) were N sources while liquid ammonium polyphosphate (APP) was the P source. Methods of N‐P application included: knife N‐knife P (‘dual knife’), knife N‐hroadcast P, broadcast N‐knife P, and broadcast N‐broadcast P. Two nitrification inhibitors were included in some studies. In the greenhouse, APP was labelled with 33P orthophosphate and 32P pyrophosphate to examine P uptake of its ortho‐ and polyphosphate fractions with different N‐P‐K application methods each with either a NH+4‐N or NO‐3‐N source.Dual knife N‐P applications gave higher leaf P concentrations and grain yields than other N‐P application methods in many of the field studies when ammoniacal N sources were used. Sodium nitrate dual knife applications were not as effective as dual knife applications of UAN or ammonia. The inclusion of the nitrification inhibitor nitrapyrin to dual knife treatments increased grain yield and/or leaf tissue P level in two 1978 studies, but had no effect in 1979. In the greenhouse the highest leaf P levels resulted from the banded NH3‐APP application. The banded SN‐APP application gave the second highest P uptake. This study also demonstrated that the N and APP need to be placed together, not separately in the soil. The amounts of the initial ortho‐ and polyphosphate portions of the APP absorbed by the plants seemed to be a function of fertilizer P demand and not related to fertilizer N in the same band. Including KCl in a band of APP did not affect leaf tissue P concentrations.
Densities of Wet Aggregated Sediment from Different Textured Soils
Authors: Rhoton F. E. , Meyer L. D. , Whisler F. D. 
Published: July 2010

AbstractThe density of wet aggregated sediment is a major factor controlling its fluvial transport and deposition. Since this property varies depending on the volume of aggregate pores filled with water, the use of dry aggregate densities in sediment transport studies may result in significant underestimations of wet sediment densities and consequently overestimations of transport distances. Therefore, this study was conducted to measure the densities of wet aggregates that exist during fluvial transport of sediment from agricultural soils. Samples from six soils, ranging in texture from silty clay to sandy loam, were wetted and agitated to simulate the stresses of raindrop impact. Two size ranges (1.00 to 0.50, and 0.50 to 0.25 mm) were collected from this sediment by wet sieving, then drained at a suction of 50 cm of water and weighed. The sediment volume was measured to the nearest 0.05 mL in a displacement vessel. Wet aggregate densities approximated 2.0 Mg/m3 and varied little among soils, or between the two size ranges. No variations in aggregate density could be directly attributed to differences in aggregate textures.
Distribution of Phosphorus Forms in Virgin and Cultivated Soils and Potential Erosion Losses
Authors: Sharpley A. N. , Smith S. J. 
Published: July 2010

AbstractThe relative amounts and distribution of P forms in virgin soil profiles are compared with those of similar soils that had been cultivated and fertilized for at least 15 years. Eight agriculturally important soil series, representative of different U.S. cropping areas, are included. Cultivation and fertilizer P application resulted in an increase in the total and inorganic P content for five soils and a decrease in organic P content for seven of the eight soils. Overall the change in total, inorganic, and organic P contents of cultivated surface horizons was +25, +118, and −43%, respectively. Fertilizer P application and mineralization of organic P during cultivation increased the available P (Bray‐I) content of all surface horizons. The content of all P forms in the subsoils was relatively unaffected by cultivation. Little change in total N/organic P ratio, exchangeable K, and cation exchange capacity was observed with cultivation and profile depth. The change in content of P forms with cultivation and fertilizer P application was closely correlated with P content of the virgin soils and amount of fertilizer P added during cultivation. The effect of sheet erosion of the surface 15 cm of virgin and cultivated soil on the content of P, N, and C forms, was estimated by comparing the nutrient contents of the 0‐ to 75‐ (uneroded) and 15‐ to 90‐cm (eroded) depths. Sheet erosion of the surface 15 cm of soil would reduce the inorganic P, organic P, available P, mineralizable N, and organic C contents of the virgin soil profile by an average of 15, 18, 25, 46, and 31%, respectively, while increasing P sorption index by 51%. The percent decrease in these P, N, and C forms (16, 2, 9, 35, and 22%) in the cultivated soil profile following sheet erosion was smaller than for the virgin soil. In general, simulated sheet erosion affected the P status of the soil profiles less than that of N.
Displacement of Nutrients into Windrows during Site Preparation of a Flatwood Forest
Authors: Morris Lawrence A. , Pritchett William L. , Swindel Benee F. 
Published: July 2010

AbstractNutrient displacement into windrows during site preparation, which followed the harvest of a natural stand of slash (Pinus elliottii Engelm.)—longleaf (Pinus palustris Mill.) pine, was examined on a 36‐ha flatwoods site in northcentral Florida. Almost 150 m of windrow were formed per hectare of site‐prepared area. The average width of the windrows was 4.2 m. The windrows averaged 2.5 m2 in cross‐sectional area and occupied approximately 6% of the harvested area. Total weight of the soil, fine wood, and coarse wood components were 154, 12, and 14 t/ha, respectively. Total N, P, and K contents were 373, 18, and 27 kg/ha of harvested area. These quantities of nutrients were equivalent to the quantities which would be removed in six bolewood harvests, and represented > 10% of the site's nutrient reserves.
Leaching of Soil Calcium, Magnesium, and Potassium in Irrigated Orchard Lysimeters
Authors: Neilsen G. H. , Stevenson D. S. 
Published: July 2010

AbstractLeaching under intense irrigation and nitrogen fertilization has reduced soil basic cation concentrations and soil pH in irrigated apple orchards. The objective of this study was to measure the effects of N fertilizer and grass cover vs. clean cultivation on Ca, Mg, and K leaching, and to determine the changes in concentrations of these cations in soil and leaf and fruit tissue of ‘McIntosh’ apple trees (Malus domestica Borkh.). Twelve lysimeters, each containing an Osoyoos sandy loam soil and a single ‘McIntosh’ apple tree, have been monitored for Ca, Mg, and K concentration of soil, drainage water, and tree leaves and fruit from 1976 to 1980. Lysimeter treatments included factorial combinations of Kentucky bluegrass (Poa pratensis) and clean cultivation and two N fertilization rates [162 (N1) and 324 kg N ha−1 year−1 (N2) as NH4NO3]. Clean cultivation had the greatest effect on cation leaching with significantly higher Ca and Mg concentrations and higher Ca, Mg, and K losses frequently measured in drainage from these plots. By 1981, exchangeable Ca, Mg, and soil pH at the 0‐ to 0.10‐m soil depth in the cultivated plots had declined by 4.3 mmol kg−1, 2.2 mmol kg−1, and 0.3 units, respectively, relative to the grass plots. Drainage from N2 relative to N1 lysimeters had a significantly higher Mg concentration for 4 years but significantly higher Ca and Mg loss rates in only 1 year because of lack of differences in drainage volumes between N2 and N1 plots. Neither the cultivation or fertilizer treatments had altered Ca, Mg, or K concentration of McIntosh fruit or foliage in 4 years. For all lysimeters, Ca and Mg leached more rapidly than K. Annual losses over all treatments, 1976 through 1980, averaged 387 kg Ca ha−1, 118 kg Mg ha−1, and 44 kg K ha−1. Such leaching would eventually lead to enrichment of local soils with K relative to Mg and Ca. This is undesirable since McIntosh trees are susceptible to Mg deficiency and K:Ca antagonism. Therefore, periodic additions of Ca and Mg as through dolomitic liming should be considered for these orchards. Also, K fertilization accelerates existing trends to relative enrichment of these soils with K.
Evaluation of Fertilizer Phosphate Residues by Plant Uptake and Extractable Phosphorus
Authors: Olsen S. R. , Watanabe F. S. , Bowman R. A. 
Published: July 2010

AbstractResidual phosphate from fertilizer P or manure seemed to accumulate mainly as octocalcium phosphate (OCP) in 23 alkaline and calcareous soils of eastern Colorado. Soil solution composition data were corrected for six ion pairs in calculating the calcium phosphate potential. These soils contained 37 to 162 mg kg−1 NaHCO3‐soluble P. Phosphorus removed by cropping varied between 58 and 275 mg kg−1 with five to eight crops before P deficiency reappeared. Phosphorus uptake was highly correlated with available P before cropping as measured by NaHCO3‐soluble P (four successive extracts), resin‐extractable P, and labile P by 32P isotopic dilution. Plants absorbed more P at equal initial concentrations of soluble P (in 0.01M CaCl2) from soils containing higher clay contents. All the OCP dissolved during cropping. This material seems to have a very high availability coefficient for plants. Accumulation of fertilizer P residues in this form would appear to be beneficial since this P is potentially all available to crops. Therefore, methods for estimating the amount of OCP in soils should be useful.
Comparison of Soil Phosphorus Extractants as Predictors of Mycorrhizal Dependency
Authors: Ojala J. C. , Jarrell W. M. , Menge J. A. , Johnson E. L. V. 
Published: July 2010

AbstractTo determine which of several soil P extraction techniques best predicted the response of citrus (Poncirus trifoliate X Citrus sinensis) seedlings to mycorrhizal fungi (Glomus fasciculatus), 25 nursery and field citrus soils from southern and central California were collected and analyzed for available P by five methods. Mycorrhizal dependency (MD), defined as the dry weight (mycorrhizal plants)/dry weight (nonmycorrhizal plants) × 100, was significantly correlated with the reciprocal of extractable soil P regardless of the extraction method. Those methods whose results depend most on soil solution P concentrations gave best results. Saturation extract P(PSE, R2 = 0.67***), anion exchange resin P(PAER, R2 = 0.57***), and 1:10 soil to water extract P(P1:10, R2 = 0.51***) were all acceptable for predicting mycorrhizal response. Bicarbonate‐extractable P (PB1C, R2 = 0.32**) and ammonium fluoride P (PAF, R2 = 0.19*) were less acceptable. Using regression models, based upon the reciprocal of the extractable‐P value, a MD > 200% was predicted where PSE < 0.65 mg L−1, PAER < 62 mg kg−1 soil, P1:10 < 0.66 mg L−1, PBIC < 34 mg kg−1 soil, and PAF < 54 mg kg−1 soil. Where analytical capabilities are adequate, PSE is the preferred method for predicting response, while PAER would suffice where higher analate P concentrations are required. Alternatively, inclusion of both PSE and PAER gave an excellent correlation with response (R2 = 0.82***). Inclusion of DTPA‐extractable Mn significantly improved regression equations in all cases except that of PSE, where DTPA‐extractable Zn significantly improved the relationship.
New Chemical Criteria for Defining the Spodic Horizon
Authors: Mokma D. L. 
Published: July 2010

AbstractMany soils which morphologically appear to be Spodosols do not meet the chemical requirements for the spodic horizon. The purpose of this study was to develop new chemical criteria for defining the spodic horizon. New chemical criteria were developed using samples from 18 pedons and were further tested with samples from 28 soil monoliths. The proposed criteria for the spodic horizon are: (i) more Cp + Alp + Fep than the overlying E horizon or A horizon if the E horizon is absent; (ii) Cp + Alp + Fep ≥ 0.50%; (iii) Cp/ (Alp + Fep) atomic ratio is 5.8 to 25.0; and (iv) illuviation index ≥ 5.0 for subhorizons with 1, 2, and 3. All 32 pedons or monoliths with Spodosol morphology met the new chemical criteria. All 11 pedons or monoliths with nonSpodosol morphology failed to meet the criteria. One of the three monoliths with weak Spodosol morphology met the new criteria.
Soil Water Change as Related to Position of Wheat Straw Mulch on the Soil Surface
Authors: Smika D. E. 
Published: July 2010

AbstractA field study was conducted in the Central Great Plains to determine the effects of the position of wheat straw mulch on soil water change of a silt loam soil (a montmorillonitic, mesic Aridic Paleustoll) during three 14‐month fallow periods. Treatments of 4600 kg/ha of wheat straw mulch flat on the soil surface, ¾ flat and ¼ standing, or ½ flat and ½ standing (normal position following standard combine harvesting) were compared with bare soil. Standing stubble was 0.46 m tall. Soil water content of one 1‐m3 hydraulic lysimeter within each treatment was measured daily and changes summed for each week, and at a distance of 2 m from each side of the lysimeter a neutron depth probe was used to determine soil water content weekly except when the soil was frozen. The relationship of soil water change for each weekly period with weekly values of total precipitation, total open‐pan (U.S. Weather Bureau Class A) evaporation, average daylight‐hour vapor pressure deficit, average maximum air temperature, average daily air temperature, average daylight‐hour air temperature, total solar radiation, and average daily wind movement, was determined by single and multiple‐correlation techniques. Soil water increases were related only to precipitation events with the highest correlation resulting from the ½ flat ½ standing wheat straw position treatment. Soil water losses were best correlated with wind movement with r2 values of 0.55, 0.41, 0.41, and 0.32 for bare soil, flat ¾ flat‐¼ standing, and ½ flat‐½ standing treatments, respectively. Soil water loss occurred from both bare soil and where the mulch was flat with winds of 0.08 MS−1. When ¼ or ½ of the mulch was standing, a wind of at least 0.55 MS−1 was needed before soil water loss occurred. Standing wheat straw does not function as a wick for loss of water from the soil.
The Effect of Exchangeable Sodium and Gypsum on Surface Runoff from Loess Soil
Authors: Keren R. , Shainberg I. , Frenkel H. , Kalo Y. 
Published: July 2010

AbstractSurface runoff from a deep silt loam loess soil at two exchangeable sodium percentage (ESP) values (4.6 and 19.3), and the beneficial effect of industrial gypsum, were studied in field plots (of 150 m2 each) under natural rainfall conditions. The ESP of the soil was found to have a very pronounced effect on the surface runoff in spite of the fact that the final infiltration rate of the soil was affected only slightly by the ESP of the soil. The effect of ESP on the percent of surface runoff is probably through its effect on the rate of crust formation. The percent of surface runoff increased during the rainy season, for both ESP levels, because the runoff from already crusted soil was higher. However, the effect of consecutive storms depended on the degree of drying between storms. Application of industrial gypsum was found to be very effective in lowering surface runoff from the soil. Spreading the gypsum over the soil was more effective than mixing it in the upper 10 cm of soil by disk. Localization of the gypsum at the soil surface, where crust is formed, explains this effect. Gypsum application lowered the ESP of the upper 10‐cm layer for both gypsum treatments. Since the ESP of the soil in both gypsum treatments was about the same, it seems that the most important factor which controlled infiltration was the electrolyte concentration in the percolating solution.