Soil management and cropping systems have long-term effects on agronomic and environmental functions. This study examined the influence of contrasting management practices on selected soil chemical properties in eight long-term cropping system studies throughout the Great Plains and the western Corn Belt. For each study, soil organic C (SOC), total N (TN), particulate organic matter (POM), inorganic N, electrical conductivity (EC), and soil pH were evaluated at 0-7.5, 7.5-15, and 15-30 cm within conventional (CON) and alternative (ALT) cropping systems for 4 years (1999)(2000)(2001)(2002). Treatment effects were primarily limited to the surface 7.5 cm of soil. No-tillage (NT) and/or elimination of fallow in ALT cropping systems resulted in significantly (P < 0.05) greater SOC and TN at 0-7.5 cm within five of the eight study sites [Akron, Colorado (CO); Bushland, Texas (TX); Fargo, North Dakota (ND); Mandan, ND; and Swift Current, Saskatchewan (SK), Canada]. The same pattern was observed with POM, where POM was significantly (P < 0.05) greater at four of the eight study sites [Bushland, TX, Mandan, ND, Sidney, Montana (MT), and Swift Current, SK]. No consistent pattern was observed with soil EC and pH due to management, although soil EC explained almost 60% of the variability in soil NO 3 -N at 0-7.5 cm across all locations and sampling times. In general, chemical soil properties measured in this study consistently exhibited values more conducive to crop production and environmental quality in ALT cropping systems relative to CON cropping systems.

Uncertainty remains concerning the magnitude of symbiotic N fixation by the soybean crop [Glycine max (L.) Merr.] when grown under varied N management systems. For deriving further enlightenment on the issue, 15N‐enriched fertilizer was applied on two soybean isolines with objectives of measuring the fraction of N derived from symbiotic fixation, residual soil N and applied fertilizer N. Plant samples were collected at full bloom, beginning‐seed, and full‐maturity stages in a field experiment conducted at the University of Nebraska Field Lab on Sharpsburg soil (Typic Argiudoll) of 3.3% organic matter content. Nitrogen fertilizer was applied at rates of 45, 89, and 134 kg/ha at planting or at full bloom. Nitrogen fertilization had no significant influence on yield or N and oil concentration of the nodulating isoline seed but increased these parameters of the non‐nodulating isoline, with delay in N fertilization being distinctly advantageous. Fertilizer utilization percentage by both isolines at later growth stages increased as fertilizer rate increased, contrary to N utilization patterns of cereal crops. “A ” value increases with increased N fertilizer rates suggested a soil N priming and/or root extension effect. Less plant N came from the soil with delayed N fertilizer application. Fertilizer applied at planting at rates above 45 kg N/ha reduced the symbiotically fixed N fraction, whereas delaying fertilizer application had no such influence at any rate of N employed.

The objective of this experiment was to evaluate the effects of irrigation sequence and of time and rate of nitrogen application on the dry matter production and fertilizer use efficiency of irrigated corn (Zea mays L.), grown on a representative fine‐textured soil of eastern Nebraska, and to monitor the movement of fertilizer N in this soil. During 1974–1976, 15N‐depleted ammonium sulfate was banded at rates of 112, 168, or 224 kg N/ha at planting or sidedressed at the eight‐leaf growth stage. No N was applied in 1977–1979. In 1974–1977, irrigation applications of 5, 7.5, or 10 cm of water were made at 2‐, 3‐, or 4‐week intervals, respectively, until a total of 30 cm had been applied. The plots were uniformly irrigated in 1978–1979.Grain yield and N uptake in 1974–1976 were not influenced by time of N application, and were highest with light, frequent irrigation. From 1977–1978, yield increased with previous N rate in response to residual mineral N in the soil. During both treatment and residual years, fertilizer N recovery in the grain was greater with sidedressing and increased with N rate. Heavier, infrequent irrigation decreased tracer N recovery in 1974–1976. Maximum fertilizer use efficiency was obtained with the low N rate, applied as a sidedressing, and with light, frequent irrigation.

Fertilizer N has become a major cost input in the production of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) with uncertainties remaining as to rates required for effecting optimum grain and protein yields without environmental pollution implications. For this reason investigations were conducted with the two crops to determine optimum rate of fertilizer N for grain and protein yields with varied levels of residual mineral N in the rooting profile of soil to 180 cm depth at planting. Fertilizer rates employed for wheat in 118 farmers' fields ranged from 0 to 67 kg N/ha by 22.5 kg increments broadcast in the spring and for corn in 17 farmers' fields from 0 to 225 kg/ha by 45 kg increments sidedressed at 30 to 45 cm growth stage. Residual mineral N was found to exert major influence on grain protein percentage and protein yield of both crops within nominal rates of N fertilizer application. The magnitude of residuals varies with the soil environment and amount of prior fertilizer use on the soil. The data reveal that grain yield response of wheat to applied N is unlikely when soil residual mineral N exceeds 120 kg/ha and for irrigated corn around 240 kg/ha at the yield levels of approximately 25 to 30 quintals/ha of wheat and 85 to 90 quintals of corn obtained in these experiments. Maximum protein yield for wheat required an additional 50 to 60 kg N/ha and for corn 60 kg, economics of which can be ascertained only with knowledge of the unit nutritional value of the produce in relation to the unit cost of N applied.

Interactions between environmental conditions and management practices can significantly affect soil function. Soil quality assessments may improve our understanding of how soils interact with the hydrosphere and atmosphere. This information can then be used to develop management practices that improve the capacity of the soil to perform its various functions and help identify physical, chemical, and biological soil attributes to quantify the present state of a soil and detect changes resulting from management. In protocols established by the Great Plains cropping system network, sampling and testing procedures were selected to identify physical, chemical, and biological soil attributes responsive to management that may serve as useful indicators in assessing the effects of management on the soil resource. Eight existing long-term studies from throughout the Great Plains in the central USA were used to make these assessments because, (1) many years are required for certain soil properties to change measurably; (2) annual weather causes variation in system performance; and (3) the soil pools of interest are spatially variable. This paper includes detailed descriptions of the treatments and sites, and both long-term and short-term (1999–2002) data on precipitation, temperature, and yields for each location.

Wind erosion is a serious problem in the Red River Valley of North Dakota. Wind erosion sediments were characterized to evaluate their potential as nonpoint source pollutants for surface water and shallow groundwater. Thirty‐four sites from the South Dakota border to the Canadian border were sampled to measure physical and chemical characteristics of displaced sediment and field soils. Collected sediments originated from fields with soils having silt loam, silty clay loam or silty clay textures. Sediments had >98% water‐stable aggregates and average NO−3‐N levels of 105 mg kg−1. Calcareous sediments (22 samples) were significantly higher in pH, NO−3‐N and electrical conductivity (EC), while noncalcareous sediments (12 samples) were higher in P and K. Soils from sugar beet (Beta vulgaris L.) and small grain fields tended to have higher NO−3‐N levels than fields with other crops or cropping practices. Agricultural chemical residues were detected and identified at two sample sites. A comparison of displaced sediments with field soils showed significant increases in NO−3‐N, P, K and EC in the sediments and a significant reduction in pH. Nearly 96% of the NO−3‐N could be leached out of the sediments in an initial leaching. Wind erosion sediments have the potential to be nonpoint sources of NO−3‐N and salinity for surface and groundwater.

The air seeder unit has developed rapidly as a method of applying fertilizer and seed in a one‐pass operation. Research was conducted with an air seeder unit over 2‐yr to determine the influence of four seed spreader patterns and deep band fertilizer placement of five fertilizer forms on hard red spring wheat (HRSW) (Triticum aestivum L.) growth and nutrient uptake. Seed spreader patterns included single row, 3‐in. wide paired spread, 5‐in. wide spread, and 12‐in. wide spread. Fertilizer materials from various sources were combined to form liquid urea ammonium nitrate plus ammonium polyphosphate (UANAPP), liquid ammonium nitrate phosphate (UANP), dry granular urea plus diammonium phosphate (UDAP), dry granular urea nitric phosphate (UNP), and dry granular urea phosphate (UUP). Single row seed pattern delayed HRSW heading 1 to 3 d compared with the wide spread seed distribution patterns. Plant dry matter at the soft dough stage was significantly reduced with single row seed placement compared with wide 12‐in. seed spread and 3‐in. paired spread patterns. Grain yield was increased by only one fertilizer form (UANP) in one year. The wide 12‐in. spread and 3‐in. paired spread seeding patterns produced the highest HRSW yield in both years. Seed weight was not influenced by deep band fertilizer or seeding patterns. Harvested seed moisture varied between years but was generally lower where the seed was spread at planting. Uptake of NPK in the wheat plant at the soft dough stage was not influenced by fertilizer form or seed spreading pattern. Nutrient uptake by the seed was highest in 3‐in. paired and wide 12‐in. spread seeding patterns. Our results showed that HRSW response to deep band fertilizer placement was similar, irrespective of seed spreader pattern at planting, when adequate nutrients were supplied. Results further suggest that maximum HRSW growth and yield can be achieved when the seed is planted, without rows, in the widest spreading pattern. Research Question Increased emphasis on reduced tillage has expanded the use of the air seeder to apply fertilizer and seed in a one‐pass operation. This study evaluates the air seeder for deep band placement of several fertilizer forms with different seed distribution patterns of spring wheat. Literature Summary The switch to reduced tillage and planting in high residue situations has advanced the design of fertilizer placement and seeding equipment. Efficient fertilizer placement and narrow seed row spacing, essential for obtaining maximum production, are difficult to achieve with disc drill implements in high residue situations. Modern machines like the air seeder unit have provided the capability to apply fertilizer by either spreading or banding and seeding by various distribution patterns. These operations can be achieved under high residue situations in a one‐pass operation. Significant germination damage will occur with high application rates of fertilizer with the seed in drill rows. However, damage can be alleviated by spreading the seed and fertilizer over a w...

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