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Short-term studies have demonstrated that drainage water management (DWM), or controlled drainage (CD), can be used to substantially reduce the loss of nitrogen (N) from drained lands for a wide range of soils, crops, locations, and climates. Long-term studies on the effects of the practice are limited. This article presents results on the effects of CD on nitrate-N (NO3-N) losses for three crops, corn (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max [L.] Merr.), in a two-year rotation in North Carolina. Nitrate losses were measured on replicated plots under CD and conventional, or free drainage (FD), treatments for nine years between 1992 and 2012 on a tile-drained site near Plymouth, North Carolina. The site is on a Portsmouth sandy loam soil with parallel drains 22.9 m apart and 1.15 m deep. The subsurface drainage characteristics under FD were drainage intensity (DI) = 8 mm d-1, drainage coefficient (DC) = 14 mm d-1, and Kirkham coefficient (KC) = 18 mm d-1. Compared to FD, CD reduced annual drainage outflow by 33% and NO3- N export by 30%, with an average annual reduction of 6.3 kg ha-1 year-1. CD increased average NO3-N concentrations by 0.9 mg L-1, but the difference was not significant. The reduction in NO3-N export observed in the CD treatment was equal to the increase in N removed by the harvested grain. The results document the effects of CD on NO3-N export over a wide range of weather conditions during the nine-year study. While the average 30% reduction in NO3-N losses in drainage water is in the midrange of that reported by previous studies for different soils and climates, this is believed to be the first time such a reduction has been attributed to the effect of CD on increasing yields and N removed in the harvested grain. [ABSTRACT FROM AUTHOR]

Effective management of variable-rate irrigation (VRI) is a critical factor for maximizing the benefit of a VRI system. In this study, the influences of soil properties on winter wheat and summer maize were studied to verify whether differences in soil available water holding capacity (AWC) had an influence on crop growth parameters, yield, and water productivity (WP). A center-pivot VRI system was employed to deliver irrigation water across the field in an alluvial flood plain in China, and AWC was used to delineate VRI management zones. Three management zones with substantial differences in AWC were created, with AWC varying from 152 to 161 mm, from 161 to 171 mm, and from 171 to 185 mm for zones 1, 2, and 3, respectively. All zones were managed using the same allowed depletion. In the two-year study, the seasonal irrigation amount was basically equivalent among management zones for both winter wheat and summer maize. Differences in crop growth parameters were detected in plant height and leaf area index for winter wheat. The maximum plant height and leaf area index observed in zone 2 were 5 cm and 2.1 greater, respectively, than in the other zones. For both winter wheat and summer maize, the highest yield and WP were observed in zone 2, except for summer maize WP in the 2014 season. Compared with the average value for this field, the yields in zone 2 were 27% and 23% greater for winter wheat and 4% and 11% greater for summer maize in the 2014 and 2015 seasons, respectively. We demonstrate that AWC is an effective parameter for zone identification in VRI management, and differences in AWC and the layered-textural soils in a field may influence the crop growth parameters, yield, and WP of winter wheat and summer maize. [ABSTRACT FROM AUTHOR]

Estimation of the quantity of stored grain is important for crop insurance, financial statements, and inventory control. Traditionally, the height of grain has been measured using weighted tape measures, and the volume is subsequently computed using standard geometric shapes (cylinders and cones) along with visual correction of the grain surface. Field measurements by four trained USDA Farm Service Agency and crop insurance agents on older farm-sized bins (8.2 to 11.0 m, or 27 to 36 ft, in diameter) resulted in standard deviations between 0.02 and 0.30 m for the equivalent height when the grain surface was not level. The largest errors were observed with off-center surface profiles. When the grain surface inside the bins was manually leveled, the standard deviation of the equivalent height varied between 0.02 and 0.18 m. Error propagation analysis was performed to evaluate the error in measuring the volume of stored grain caused by the uncertainty associated with measuring the bin diameter and grain height as a function of the ratio of equivalent level grain height to bin diameter (EH/D). The errors were examined using an assumed range of uncertainties to explore how each factor contributed to the error in different scenarios. The uncertainty increased as the EH/D ratio decreased, especially in smalldiameter bins with shallow grain heights where the volume bounded by the surface profile of the grain represented a large percentage of the total volume within the structure. Therefore, any errors in defining the surface profile resulted in large errors in the total estimated volume of grain in small-diameter bins. Conversely, for large-diameter bins with large grain heights, the surface profile represented a very small percentage of the total volume of grain. Consequently, any errors in defining the profile produced much smaller errors in the total grain volume. For accurate measurements, defined as a standard deviation of 1.2 cm (0.04 ft) in the diameter and 7.6 cm (0.25 ft) in the equivalent level height, the overall uncertainty in the volume measurement never exceeded 5% for smaller bins (<10 m in diameter) and decreased to less than 1% for larger bins (>10 m in diameter). A sensitivity analysis was performed on the three most common methods used to convert the measured volume to a quantity of grain. In each method, the quantity of grain stored in a bin is the product of the volume measurement and the pack factor. With all three methods, the sensitivity of the pack factor determination resulted in an error of less than 1% in the estimated total quantity of stored grain. The volume measurement accounted for the majority of the error in the estimation of bin inventory. As a result, accurate measurement of the bin volume is critical for determining the quantity of stored grain. [ABSTRACT FROM AUTHOR]

Experimental investigations of grain flow can be expensive and time consuming, but computer simulations can reduce the large effort required to evaluate the flow of grain in handling operations. Published data on material and interaction properties of selected grains and oilseeds relevant to discrete element method (DEM) modeling were reviewed. Material properties include grain kernel shape, size, and distribution; Poisson's ratio; shear modulus; and density. Interaction properties consist of coefficients of restitution, static friction, and rolling friction. Soybeans were selected as the test material for DEM simulations to validate the model fundamentals using material and interaction properties. Single- and multi-sphere soybean particle shapes, comprised of one to four overlapping spheres, were compared based on DEM simulations of bulk properties (bulk density and bulk angle of repose) and computation time. A single-sphere particle model best simulated soybean kernels in the bulk property tests. The best particle model had a particle coefficient of restitution of 0.6, particle coefficient of static friction of 0.45 for soybean-soybean contact (0.30 for soybean-steel interaction), particle coefficient of rolling friction of 0.05, normal particle size distribution with standard deviation factor of 0.4, and particle shear modulus of 1.04 MPa. [ABSTRACT FROM AUTHOR]

Adsorption and desorption of phosphorus (P) and nitrogen (N) by stalk residues may influence the concentrations of P and N in runoff A laboratory study was conducted to measure the effects of P and N constituents in solution on adsorption and desorption of P and N by corn, soybean, and wheat stalk residues. Experimental variables included type of stalk material (corn, soybean, and wheat), inorganic nutrients in solution (PO4-P and NO3-N; PO4-P and NH4-N, NO3-N and NH4-N, and PO4-P, NO3-N, and NH4-N), solution concentration (0, 6, 12, and 24 µg g-1 residue), and stalk immersion period (25, 250, 2500, 25000, and 86400 s). The initial concentration of each of the P and N constituents in a particular test solution was the same (0, 6, 12 or 24 µg mL-1). Corn-stalk residues released PO4-P, NO3-N, and NH4-N. The quantity of PO4-P released generally increased as the length of time the corn stalks were immersed became greater. The presence of P and N constituents in solution in general did not affect the quantity of NO3-N released by corn-stalk residues. Soybean-stalk residues released PO4-P and adsorbed relatively small amounts of NH4-N. Wheat-stalk residues released PO4-P, and adsorbed NO3-N and NH4-N. The presence of stalk residues, P or N solution concentration, and residue immersion period may influence P and N concentrations of overland flow. The amount of P and N adsorbed or desorbed by residue materials can be significantly different if more than one nutrient constituent is present in solution. [ABSTRACT FROM AUTHOR]

Increasing demand of corn for ethanol production places significant pressure on the availability of corn for food and animal feed. Other feedstocks such as crop residues, energy crops, wood waste, and forest residues are being considered for cellulosic ethanol production in the near future. The availability of crop residues for cellulosic ethanol production in Ohio was analyzed in this study. Results showed that two clusters of counties, each with a collection radius of less than 80 km (50 miles), had the capability to provide feedstock for two ethanol plants with feedstock demand of 5,000 dry tons per day each. These two plants would be located in the northwestern region of Ohio to produce a total of 927 million L (245 million gal) of ethanol per year. Other counties that have low biomass availability could grow energy crops such as switchgrass and provide mixed feedstocks for a cellulosic ethanol plant. [ABSTRACT FROM AUTHOR]

Crop residues value when left in the field and also when removed form the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil surface with nearly full coverage by corn stover or standing wheat stubble. E was also measured from a oil surface that was partially covered with corn stover without crop shading. E was measured with mini-lysimeters that were 300 mm in diameter and 140 mm deep. Surface coverage and amount of dry matter of crop residues influenced E. E was reduced nearly 50% compared with bare soil E when corn stover and wheat stubble nearly covered the surface under a corn canopy during the growing season. Partial surface coverage, from 25% to 75%, with corn stover caused small reductions in E compared with bare soil when there was no crop canopy. Full surface coverage reduced energy limited E 50% to 65% compared with E from bare soil with no shading. No-till management, using crop residues to significantly reduce E, required soil surfaces to be nearly covered. Economic benefits of crop residues for E suppression during the growing season can be as much as $365 ha-1. [ABSTRACT FROM AUTHOR]

A double-cropping system such as that of winter wheat and summer maize in north China requires irrigation to achieve production goals. The soil during the seeding stage of summer maize is usually dry. For summer maize, soil moisture before sowing (SMBS) is important for seedling growth, yield, and water use. Our objective was to investigate the effects of applying different irrigation schedules to winter wheat on the SMBS, yield, and water use efficiency (WUE) of summer maize. Field experiments involving winter wheat with 0, 1, 2, and 3 irrigation applications (T0, T1, T2, and T3, respectively) were conducted in a dry year (2002), moderate year (2003), and humid year (2005). Irrigation of winter wheat increased the average SMBS of summer maize in the 1.2 m soil profiles to 17.7, 57.3, and 79.6 mm in T1, T2, and T3, respectively. Differences in the soil moisture content among the treatments were significant in the late growing season of summer maize in the dry and moderate years but not in the humid year. In 2005, maize yields among the treatments were not significantly different as compared to those in T0; the yields increased from 22.1% to 56.0% in 2002 and from 1.9% to 11.4% in 2003. Compared to T0, the WUE of summer maize increased by 15.3%, 23.6%, and 24. 7% in T1, T2, and T3, respectively, in 2002 and by 0.01%, 3.4%, and 5.4% in 2003; however, it decreased by 2.4%, 5.6%, and 12.4%, respectively, in 2005. Considering the combined WUE of winter wheat and summer maize, there was no significant difference between T2 and T3 (LSD, P < 0.05). These results suggest that winter wheat should be irrigated at the jointing and heading stages to achieve reasonable grain yield and WUE for both the crops. [ABSTRACT FROM AUTHOR]