bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Dynamics and Balance in Intensified Rainfed Lowland Rice‐Based Cropping Systems
Authors: Tripathi B. P. , Ladha J. K. , Timsina J. , Pascua S. R. 
Published: July 2010

AbstractNitrogen dynamics and balances in intensive and diversified lowland rice (Oryza sativa L.)‐based cropping systems that receive heavy fertilization, tillage, and irrigation have not been explored. Such information is essential to improve the efficiency of N fertilizer, an input based on a nonrenewable energy resource and whose oxidized products pose hazards to human health and the environment. Field experiments at an experimental farm on an Inceptisol and in two farmers' fields, one with an Inceptisol and one with a Vertisol soil, quantified (i) NO‐3‐N and NH+4‐N in different soil layers in relation to water‐filled pore spaces (WFPS), (ii) N balance, and (iii) systems‐level N efficiencies in several cropping patterns. Nitrate‐N and NH+4‐N were quantified monthly from July 1993 to June 1994. The WFPS remained <0.80 mL mL‐1 in the beginning of the wet season and throughout the dry season that enhanced nitrification. Ammonium‐N in the 100‐cm layer was 20 to 40 kg ha‐1 in the wet season and <10 kg ha‐1 in the dry season. Nitrate‐N, however, ranged from 27 to 54 and from 67 to 195 kg ha‐1 in the two seasons; it was higher in farmers' fields (192–195 kg ha‐1) than in the experimental farm (67–112 kg ha‐1). Total N loss was 34 to 549 kg ha‐1 across sites, with the largest in rice‐sweetpepper (Capsicum annuum L. var. annuum) and rice‐tomato (Lycopersicon esculentum Miller). Despite a lack of a consistent trend in N efficiency among the different cropping systems, it was higher with tobacco (Nicotiana tabacum L.) and garlic (Allium sativum L.). There appears an opportunity to grow a NO‐3 catch crop during the dry‐wet transition in rice‐sweetpepper and rice‐tomato systems to capture and recycle soil NO‐3‐N.
Rice Plant Growth and Nitrogen Accumulation in Drill‐Seeded and Water‐Seeded Culture
Authors: Bufogle, A. , Kovar J. L. , Bollich P. K. , Norman R. J. , Lindau C. W. , Macchiavelli R. E. 
Published: July 2010

AbstractNitrogen fertilization strategies for flooded rice (Oryza sativa L.) depend on understanding plant N demand. Seasonal N accumulation research in general is limited, and is nonexistent in water‐seeded (WS) culture. A field study was conducted for 3 yr in Louisiana and 1 yr in Arkansas to characterize plant growth and N accumulation by rice at different development stages, and to compare these factors in drill‐seeded (DS) and WS culture. ‘Cypress’ rice was grown on a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf). Straw, grain, roots, and soil were collected at eight growth stages. Nitrogen‐15‐labeled urea was applied to 75 by 75 cm microplots enclosed by stainless steel retainers. Total dry matter increased each season, and grain dry matter was similar each year. In 1994 and 1995, both surface and subsurface root growth increased linearly until 90% heading. Fertilizer N accumulation increased to the four‐leaf plus 21‐d or panicle differentiation (PD) stages. Native soil N and remobilization of N from straw provided N needed for maturing grain. From heading plus 21 d to maturity, factors did not differ under either DS or WS each year. At early and late stages of development, factors did not differ under DS and WS in Louisiana. Differences in N accumulation and fertilizer N recovery were seen in Arkansas. This suggests that, under Louisiana conditions, results from experiments in DS and WS are interchangeable. Variation of the measured factors among years was significant, suggesting that even when labeled N is used, results from multiple seasons are required for accurate interpretation.
Field‐Scale Variability of Phosphorus and Potassium Uptake by No‐Till Corn and Soybean
Authors: Borges R. , Mallarino A. P. 
Published: July 2010

AbstractUse of precision farming technologies requires better understanding of nutrient variability in soils and plants. This study assessed patterns of spatial variability of plant P and K content of no‐till corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] on eight fields that had varied histories of fertilization. One hundred composite whole‐plant samples (five corn plants and 10 soybean plants at V5 to V6 growth stages) were collected in late spring from 2.2‐m2 areas spaced 3.05 m along two intersecting transects. Dry weight (DW) and total P and K concentrations were measured in all samples. Plots of observed values, variography, and fast Fourier transform (FFT) analyses revealed clustering of values and periodic patterns of DW and nutrient content in most fields. The patterns of variability varied greatly among fields and directions within a field. The diversity of patterns probably results from nonuniform distribution of fertilizers and animal manures. Patterns of plant K uptake (KU) followed patterns of plant K concentration (KC) in some fields and those of DW in others. Patterns of plant P uptake (PU), however, usually followed those of DW. Implementation of plant analysis for no‐till fields should address situations with high spatially structured variability of cyclic or clustered structure. The results show that the structure of the variability in P and K uptake is site specific and that both the sampling scheme and the optimal separation distance between sampling positions would vary greatly among fields. The results suggest that plant analysis would have similar sampling problems to those of soil testing for representing the P and K supplies of corn and soybean fields.
Optimizing Corn Production and Reducing Nitrate Losses with Water Table Control‐Subirrigation
Authors: Drury C. F. , Tan C. S. , Gaynor J. D. , Oloya T. O. , van Wesenbeeck I. J. , McKenney D. J. 
Published: July 2010

AbstractWater table control‐subiriggation (WTC) systems have increased crop production and improved water quality; however, the relationship between N management, water table depths, and corn production has not been well defined. We hypothesized that optimizing water table depth would increase corn (Zea mays L.) growth, improve N fertilizer efficiency, and reduce NO‐3 losses. A greenhouse incubation study with three water table depths (30, 60, and 80 cm) and four N rates (0, 0.7, 1.4, and 2.1 g N plant‐1) was conducted using undisturbed soil columns (Fox sandy loam, Typic Hapludalf) planted to corn. The 30‐cm WTC treatment had the greatest NO‐3 loss through tile drainage (715 µg N column‐1). The 60‐cm WTC treatment reduced these losses by 54%. Nitrate losses through tile drainage were proportional to drainage volume, which followed the order 30 cm > 60 cm > 80 cm WTC. The 60‐cm WTC treatment increased crop yields (95 g plant‐1) compared with the 30‐cm (68 g plant‐1) and 80‐cm WTC (18 g plant‐1) treatments at the optimal N rate of 1.4 g N plant‐1. After the first simulated rainfall event, N2O production was increased by 12.7 times with the 30‐cm WTC treatment (825 µg N column‐1 d‐1) compared with the 60‐ and 80‐cm WTC treatments. Water stress imposed by the 80‐cm WTC treatment limited crop growth, N uptake, leaching, and N2O emissions. However, up to 28% of added N (664 mg N column‐1) remained in the soil after corn was harvested from the 80‐cm WTC treatment, which would be susceptible to leaching between cropping seasons.
Determination of Soil Sorptivity and Hydraulic Conductivity from the Disk Infiltrometer
Authors: Zhang Renduo 
Published: July 2010

AbstractA simple two‐term infiltration equation was used to determine soil sorptivity and hydraulic conductivity from cumulative infiltration data from the disk infiltrometer. Parameters of the equation were obtained by fitting the equation to cumulative infiltration data. The parameters of the first and second terms in the equation were related to soil sorptivity and hydraulic conductivity, respectively. By using the twoterm infiltration equation, sorptivity and hydraulic conductivity were estimated for various soils, radii and tensions of the disk infiltrometer, and initial infiltration conditions. Sorptivity and hydraulic conductivity values calculated using the method and simulated cumulative infiltration data resulted in excellent agreement with the theoretical results. The relative error of estimation of sorptivity and hydraulic conductivity was within 5% for most cases. The method can be used to determine the soil hydraulic properties from infiltrometer infiltration for a wide range of soils, having a retention function of the type of either van Genuchten, Russo, or Zhang and van Genuchten.
A Model Describing Pesticide Bioavailability and Biodegradation in Soil
Authors: Shelton Daniel R. , Doherty Michael A. 
Published: July 2010

AbstractA model is proposed for describing pesticide‐substrate bioavailability and rates of biodegradation in soil. The model accounts for sorption to soil surfaces, diffusion into the internal matrix of soil organic matter or aggregates, and microbial growth. Rates of sorption and diffusion are approximated by first‐order kinetics while microbial growth is approximated by Monod kinetics. Model verification was performed using 2,4‐D (2,4‐dichlorophenoxyacetic acid) degradation data from high and low organic matter soils inoculated with pure cultures of 2,4‐D degrading bacteria. Estimates of sorption, diffusion, and Monod constants were obtained sequentially by fitting the defining differential equations to the data using nonlinear regression techniques. Independent estimates of initial biomass (X0) and growth yield (Y) were required, although X0 could be approximated from the number of colony‐forming units assuming a bacterial weight of 0.1 pg cell−1. The model could account for the partitioning of 2,4‐D between soluble and sorbed phases and provided estimates of the Monod constants, µmax and KS, which were generally consistent with values previously determined in pure culture. In conjunction with pest toxicology data, the model may be useful in predicting the time between application and loss of efficacy (i.e., window of efficacy) for biodegradable pesticides.
Spodosol Development as Affected by Geomorphic Aspect, Baraga County, Michigan
Authors: Hunckler Robert V. , Schaetzl Randall J. 
Published: July 2010

AbstractIn midlatitude locations with steep slopes, geomorphic aspect can be an important factor in determining spatial variations in soil development. This study examines the influence of aspect on soil development in Baraga County, Michigan, as a means of explaining within‐landform variability. The soils are sandy and have spodic morphologies. All are located on steep slopes (45–73%) of contrasting aspect. Ten pedons each from backslopes on north‐to‐northeast‐(N‐NE) and south‐to‐southwest‐(S‐SW) facing slopes were described, sampled, and compared using standard techniques.Variation in slope gradient was not, statistically, a determining factor in the differential soil development found here. Aspect has strongly influenced soil development, however, with soils more strongly developed (i.e., more podzolized) on N‐NE slopes than on S‐SW slopes. Several soil characteristics indicative of strong podzolization were found on N‐NE slopes, including higher values of solum thickness and POD index, greater losses of extractable Fe and Al from E horizons and concomitant gains in B horizons, and darker and redder B horizon colors. Soils were generally cooler on N‐NE slopes in summer, with essentially similar temperatures under snowpacks in winter. Cooler temperatures and greater amounts of infiltrating water in soils with N‐NE aspects may have accelerated podzolization by allowing more organo‐metallic complexes to be formed and translocated. Podzolization driven by translocation of amorphous, inorganic compounds appears, however, to be nearly equivalent on sites of differing aspect.Of the ten pedons on N‐NE slopes, nine classified as Spodosols (Entic or Typic Haplorthods) and the other was an Entisol. Seven of the 10 pedons on S‐SW slopes classified as Entisols (Udipsamments or Udorthents), and the remaining three were Spodosols.
Aggregate Stabilities of Some Southeastern U.S. Soils
Authors: Levy G. J. , Miller W. P. 
Published: July 2010

AbstractSoils from humid regions have traditionally been considered to have stable aggregates. Some humid southeastern U.S. soils have demonstrated poor structural stability. We hypothesized that a sensitive measure of aggregate stability of southeastern U.S. soils would demonstrate that stability of macroaggregates may depend on some soil properties and may not correlate with soil erosivity. This study evaluated the stability of aggregates from southeastern U.S. soils employing a sensitive aggregate stability test, and compared it with previously published data for the same soils. Stability of 0.5‐ to 1.0‐ mm aggregates of 11 Georgia topsoils were determined using the high‐energy‐moisture‐characteristic method, where the destructive force used to break the aggregates is a controlled wetting process. Aggregates were wetted either rapidly by a matric potential of 0.0 J kg−1, or slowly where they were initially subjected to a matric potential of −2.0 J kg−1, which was then gradually increased to 0.0 J kg−1. Two water qualities were used for wetting: tap water (electrical conductivity [EC] 0.097 mS cm−1) and a saturated CaSO4 solution (EC 2.24 mS cm−1). Stability ratio (ratio of fast to slow structural indices) of the soils ranged between 0.40 and 0.95. Six soils had a stability ratio of ≤0.5 (low aggregate stability). Aggregate stability in unstable soils with pH >6.5 rose to ≥0.62 when saline solution was used. The measured aggregate stability indices significantly correlated with published infiltration rate data (R = 0.622), but not with soil splash or soil loss.
Resin Capsules for On‐Site Assessment of Soil Nutrient Supply in Lowland Rice Fields
Authors: Dobermann A. , Pampolino M. F. , Adviento M. A. A. 
Published: July 2010

AbstractUsing ion‐exchange resin capsules for assessing nutrient supply in lowland rice (Oryza sativa L.) fields requires strategies for estimating field means of resin adsorption quantities (RAQs). To develop recommendations for on‐site use of capsules, we conducted two experiments in rice fields on Typic Tropaquepts and Tropaqualfs in the Philippines. Resin capsules were placed in situ (ISI) or inserted into composite soil samples for on‐site incubation (OSI). Capsules were retrieved after 1, 2, 4, 7, and 14 d and RAQs of NH4‐N, P, K, Ca, Mg, Na, Fe, and Mn were measured. In ISI or OSI of single soil cores, coefficients of variation in RAQs of N, P, and Fe ranged from 17 to 71%, whereas those for K and Ca ranged from 10 to 20%. Between one and five capsules per 0.25‐ha field were required to estimate the average RAQ of P, K, and Ca after 14 d with a precision of ± 10%, compared with four to 10 capsules per field for estimating the RAQ of NH4‐N and Fe after 14 d. Soil core sampling and OSI of composite soil samples reduced microvariability in RAQs. About eight to 10 soil cores (0–15‐cm depth) were required per field for resin capsule OSI. Because of soil physical changes, degassing, and oxidation during soil mixing, RAQs of P, Fe, K, and Ca were lower for OSI than for ISI. The ISI method is recommended for routine soil testing in lowland rice fields. The OSI requires fewer capsules but more labor. Its reliability depends on the extent to which mechanical disturbance, degassing, and exposure to air can be minimized.
Sesbania Phosphorus Requirements When Used as Biofertilizer for Long‐Term Rice Cultivation
Authors: Ventura W. , Ladha J. K. 
Published: July 2010

AbstractGreen manures may affect the long‐term nutrient supplying capacity of soils. In a long‐term trial that compared the performance of azolla (Azolla microphylla Lam.), sesbania (Sesbania rostrata Bremek. & Oberm.), urea, and no fertilizer N on rice (Oryza sativa L.), a progressive decline in the growth of and N accumulation by sesbania was observed after the ninth crop. This study examined the reasons for sesbania decline with emphasis on the effect of fertilizer P on sesbania performance in relation to soil available P, cropping history, and moisture regime. In the 1992 dry season (14th crop), sesbania performance with and without P was determined in (i) field microplots within main long‐term plots, and (ii) pots containing soil monoliths from long‐term plots. Without P fertilizer, sesbania grew poorly and accumulated <40 kg N ha−1. But addition of 28.4 kg P ha−1 increased sesbania N accumulation 3 to 11 fold and the greater N availability increased rice production. Addition of P improved sesbania biomass and N accumulation in dried‐flooded and continuously flooded regimes but not in the dried‐moist regime. Sesbania P requirements were greater than for rice. Continuous rice‐sesbania cropping without addition of P limited sesbania growth, N accumulation, and green manure value even though it did not limit rice production, suggesting that the P requirements will be greater for a long‐term rice cropping system that depends solely on green manure N than for rice grown with fertilizer N.
Mineralogical Variations of Bulk and Rhizosphere Soils from a Norway Spruce Stand
Authors: Courchesne François , Gobran George R. 
Published: July 2010

AbstractThe mineralogy of bulk and rhizosphere soil materials was compared to assess the effect of roots on mineral weathering in a Podzol supporting a homogeneous Norway spruce [Picea abies (L.) Karst] stand. Six horizons were sampled in two profiles at the Skogaby site in southwestern Sweden. The soil adhering to the roots after shaking was considered as rhizosphere soil, a layer <3 mm thick intimately associated with root surfaces. The remaining material was regarded as bulk soil. The mineralogy of the clay‐sized particles of both fractions was determined by x‐ray diffraction (XRD) and normalized with respect to quartz (I/IQZ). Amorphous solid phases were estimated by extracting Fe and Al with acid‐ammonium oxalate (AlO, FeO). Mineral abundance (I/IQZ) near roots differed consistently from that in the bulk soil. The rhizosphere contained significantly lower amounts of amphiboles and expandable phyllosilicates (α = 0.10) relative to the bulk soil. This trend was paralleled by a systematic increase in AlO and FeO (α = 0.10) at the root‐soil interface. Lower amounts of plagioclase were also seen in the rhizosphere samples from five of the six horizons, but the difference from the bulk soil was not significant when all horizons were integrated in the comparison. No rhizosphere effect was detected for K‐feldspars. This study provides converging results that emphasize the pedogenic significance of the rhizosphere zone and the role of roots as dynamic weathering agents.
Applicability of Analytical Solutions for Flow from Point Sources to Drip Irrigation Management
Authors: Eugenio Coelho F. , Or Dani 
Published: July 2010

AbstractThe design and management of drip irrigation systems requires understanding of water distribution and dynamics within the wetted soil volume. This information can be obtained by means of analytical or numerical solutions of the multidimensional Richards equation. Though steady‐state solutions have been advocated as design tools for drip irrigation, very little information about their performance under practical field conditions is available. The objective of this study was to evaluate the applicability of analytical solutions for steady and transient flows from point sources to practical drip irrigation management. The emphasis was on the adaptive and dynamic aspects of management vs. conservative design considerations. Experiments were carried out in containers and in the field to determine steady‐state attainment rates and to provide information on spatial and temporal dynamics of water content and matric potential during irrigation cycles. The main results were: (i) analytical solutions for steady and transient flow conditions predicted reasonably well measured distributions of water content and matric potential in the absence of plants; (ii) steady flow conditions were seldom realized under practical drip irrigation; (iii) transient flow solutions provided a more realistic description of soil water dynamics; and (iv) introducing uptake terms into transient analytical solutions provided a simple and effective framework for capturing soil water dynamics in the presence of plant roots.
Use of Pseudo‐Crossvariograms and Cokriging to Improve Estimates of Soil Solute Concentrations
Authors: Zhang R. , Shouse P. , Yates S. 
Published: July 2010

AbstractEstimating mass and distributions of chemicals in soils is one of the key steps to study chemical transport in the vadose zone and groundwater systems. In this study, solute mass and distributions were computed in an 800 by 800 by 1.8 m soil volume using kriging and cokriging with nonsymmetric pseudo‐crossvariograms. Among the measured chemicals of Cl−, SO2−4, Ca2+, Mg2+, Na+, P2O−5, K+, and NO−3 in the three‐dimensional system, Cl− was used as the model to show the estimation process and results. Using pseudo‐crossvariograms maximized the use of available information at different soil depths and improved solute estimation. All sample pseudo‐crossvariograms between depths were modeled successfully with common variogram functions such as spherical and linear. Therefore, it was relatively easier to test the positive definiteness of the cokriging coefficient matrix adapted to pseudo‐crossvariograms. Cokriging allows easily obtained information at shallower depths to be used to improve solute estimations at deeper depths. Compared with kriging, cokriging reduced the mean squared errors of estimations between 30 and 60% at different depths, and reduced the mean kriging variances between 35 and 58%. In the total mass estimation of Cl− in the soil, cokriging with nonsymmetric pseudo‐crossvariograms used less than half the data; potentially it could reduce more than half the sampling cost of kriging estimation. Meanwhile, cokriging reduced the estimation error by about 18%, when compared with kriging estimates using all observations. Using the same data at each layer, cokriging would reduce the estimation error 40% more than kriging because cokriging efficiently incorporated information at upper layers without increasing the sample requirement. Cokriging with nonsymmetric pseudo‐crossvariograms is an accurate and economical way to calculate solute distributions and total mass in a large field.
Soil Nitrogen and Carbon Response to Maize Cropping System, Nitrogen Source, and Tillage
Authors: Reeves Margaret , Lal Rattan , Logan Terry , Sigarán Juan 
Published: July 2010

AbstractThese experiments were conducted to evaluate the combined effects of intercropping and N source and the interaction of these two factors with tillage on N dynamics. Maize (Zea mays L.) was planted in two consecutive years in Costa Rica to measure changes in soil mineral N, soil C, and maize grain N in response to monoculture or polyculture and legume residues or NH4NO3 fertilizer under conventional (CT) or minimum (MT) tillage. Soil mineral N levels were greater with fertilizer than with residues at the end of the first season and greater with residues at the beginning of the second season, reflecting a residual effect from the previous season. There were no treatment interactions. The dominant form of mineral N shifted from NO−3‐N (first season) to NH+4‐N (second season). The shift corresponded to an overall increase in soil C (from 27.6 to 30.2 g kg−1), which was significantly greater under monoculture and with residues (33.2 and 33.4 g kg−1, respectively) than under polyculture and fertilizer (31.1 and 30.9 g kg−1, respectively). A positive cropping system × N source interaction resulted in 67% greater maize grain N in the polyculture under residues than with fertilizer N. Maize response to polyculture and legume residues, together with soil N and C data, were used to propose a mechanistic explanation for how these strategies may help maintain productivity (and minimize N loss) in low‐input farming systems.