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The elemental concentration of K, Na, P, Ca, Fe, Mg, Cu, Zn, and Mn was determined in seeds of three cultivars of cowpeas [Vigna unguiculata (L.) Walp.] treated with 0, 2000, and 4000 ppm simazine as a foliar spray and side dressed with 0, 30, and 60 kg/ha ammonium nitrate fertilizer. The element Ca was increased by the simazine treatment in‘Pinkeye Purple Hull’and Mn was increased by the ammonium nitrate fertilizer treatment in‘Mississippi Silver’. Significant fertilizer by simazine interactions were found with the remaining elements. Similar treatment responses in the elemental concentration were found among the three cultivars. The percentage recommended dietary allowances based on the individual elemental concentrations that a 100s raw edible portion of cowpeas would supply were not significantly affected by the treatments.

In the Piedmont of the Southern Appalachian region, soil degradation is most often expressed by crop water deficit that limits crop yield in the warm season. To evaluate the nature of variability on these cropped lands, soybean [Glycine max (L.) Merr.] yield and associated soil characteristics were measured across the range of surface soil conditions in 40 farm fields. Factor analysis of the data permitted identification of variables responsible for most of the yield variability. Carbon in the surface soil was identified as the manageable soil variable that could significantly influence crop water availability and curtail soil erosion. Subsequently, selected crop cultures that supplied a range in quality and quantity of crop biomass to the soil surface were applied on three soil erosion classes for 5 yr. Large increases in rainfall infiltration and reduced soil erodibility were associated with no-till planting of grain sorghum [Sorghum bicolor (L.) Moench] into crimson clover (Trifolium incarnatum L. Tibbee) in comparison to conventional tillage of grain sorghum and soybean. The maintenance of a decomposing mulch by crop residue additions of about 12 Mg ha -1 yr -1 generated high soil C levels in the 0- to 15-mm depth and a high water stability of aggregates in the 0- to 80-mm depth in comparison to incorporated crop residues. In the 6th yr, grain yield of conventionally tilled soybean was 30 to 100% greater on the previously no-till crop culture than on the conventionally tilled. The restoration and maintenance of soil productivity commensurate with inherent site resources was associated with maintenance of a decomposing mulch on the soil surface derived from an appropriate quantity and quality of crop residue produced in situ.

Soil loss from and rainfall retention on cropland during individual seasons vary from year to year. To quantify this variability for evaluation of soil and water related risks for different seasons and crops, probability distributions of soil loss and rain water retention are needed. In this study, probability distributions of soil loss and rainfall retention rates were computed using rainfall, runoff, and soil loss data from three field watersheds with Cecil-Pacolet soil (Typic Hapludults) in the Southern Piedmont of the United States. Long-term (34-year) rainfall records from a nearby gage were included in the computations. Resulting probability distributions were compared to evaluate risks of soil loss and low rainfall retention for different seasons and crops. Risks due to watershed differences in slope and in terrace and waterway conservation practices were also compared. These comparisons showed that soil loss risks are greater for the summer than for the winter crop season and greater for soybean (Glycine max. L. Merr.) than for corn (Zea mays L.). Considerable soil loss risk reduction was also observed for watersheds with less land slope and with terrace and grassed waterway installation. Risk of low rainfall retention was found to be less for the winter crop season than for the summer season. Rainfall retention risks for the winter crop season appeared to be unaffected by crop and watershed differences. For the summer crop season, however, risk of low rainfall retention was observed to be slightly higher for soybean than for corn and slightly lower for fields with terraces, grassed waterways, and lesser slopes. Soil loss and rainfall retention risks computed in this study can be coupled with economic costs for crop production and conservation planning.

Southern pea seeds were grown 2 yrs with treatments of ammonium nitrate fertilizer 0, 30, and 60 kg/ha and simazine 0, 2,000, and 4,000 ppm applied as a foliar spray. Yield, proximate analysis, amino acid content, and protein quality were determined. No differences were found in yield, crude fat, and crude fiber. Ash, protein, and several of the amino acids increased with the 30 and 60 kg/ha nitrogen fertilizer treatments. Treatments with simazine had no effect on the essential amino acid content. In the Southern pea seeds, protein quality was decreased by the treatments with nitrogen fertilizer, simazine, and combinations of these treatments.

An approach and methodology for characterizing behavior of crop-soil systems as they may be modified by soil erosion were applied to a Cecil-Pacolet soil (clayey, kaolinitic, thermic Typic Hapludults) landscape cropped to soybeans [ Glycine max (L.) Merr.]. In each of two years crop and soil measurements along with determination of slope and landscape position were made on slightly, moderately and severely eroded sites in 24 farm fields of which 8 were common to both years. Daily rainfall was recorded during the crop season on each field. Among the 40 variables selected to characterize the system behavior were dynamic or within-season, among-season, and static variables. Search for and identification of variables which determine most of the soybean yield variability have been adopted as the primary objectives in determining behavior of the crop-soil system. Recognizing the strong functional dependencies among a number of the variables, we used multivariate statistical procedures that are based upon eigenvalue-eigenvector analysis of the matrix of correlation coefficients among all variates. Results of using factor analysis and components regression to identify variate contributions to yields of soybeans are reported. In linear, non-interactive analyses, variate contributions to yield were evaluated. The major contribution of clay and organic carbon contents in the surface 0.1 m of soil to soybean yield variations in both seasons identifies soil water as the regulating variable.

An understanding of N cycling in the soil-plant-atmosphere components of wheat (Triticum aestivum L.) production systems is necessary to maximize yield and quality. The objectives of this study were to examine N cycling and observe the effects of N surplus and deficit on N absorption/desorption in the soil and atmosphere and to evaluate translocation within the plant. Soil, plant, and microclimate measurements were taken concurrently, and soil, plant, and atmospheric ammonia (NH₃) transport determined. During the early vegetative phase, plant N concentration reached a maximum; however, during the remaining growth periods, N concentration decreased even though N uptake from the soil continued until plant maturity. More total N was translocated to grain from leaves than stems, and translocation from the leaves began earlier than that from stems. Isotope and total N studies showed that after anthesis about half of the grain N came from remobilization from leaves and stems and the other half directly from the soil. A progressively larger percentage of N came from mineralized organic matter as the season progressed. Nitrogen was lost as volatile NH₃ from the plant after fertilizer application and during the senescence period. Prior to anthesis, atmospheric NH₃ absorption was observed during a period when soil N was temporarily unavailable. About 21% equivalent of the applied fertilizer was lost as volatilized NH₃. During the period of soil unavailability an amount equivalent to about 1% equivalent of the applied fertilizer was gained from atmospheric NH₃ by plant absorption.

(…) Soybean growth and N uptake characteristics were similar in both tillage systems, except during a 14-d drought period, which caused water stress in the CT system, but not the NT system. Nitrogen fixation decreased in the CT system to less than half that of the NT system fixation rate, resulting in a seasonal reduction of 29% in the CT system (…)

Effects of three plant densities and two nitrogen rates on leaf areas and nitrogen uptake by tobacco plants were studied during 1961 and 1962. A study was also made on the economics of these treatments.Leaf area indices (LAI's) for both years increased with time until the reduction in total leaf area through loss of senescent lower leaves became greater than the gain in leaf area of the active upper leaves. The highest maximum LAI of 5 in 1961 was obtained for the high nitrogen rate and the 25-cm spacing. The lowest maximum LAI of 2.5 was obtained for the low nitrogen rate and the 76-cm spacing. LAI's increased with high nitrogen and at both levels of nitrogen the LAI's were in the order of 25 > 51 > 76-cm spacings in 122-cm beds.Relationships between leaf area and leaf weight per plant were very similar during 1961 and 1962. Correlation coefficients for leaf areas and weights varied from 0.95 to 0.99 in 1961 and from 0.92 to 0.99 in 1962. In both years, better correlation appeared between leaf areas and weights at the high nitrogen rate than at the low nitrogen rate, with spacing treatments having little effect on the relationships.Nitrogen uptake was much higher with the high nitrogen treatment than with the low nitrogen treatment.The yield of flue-cured tobacco increased with closer plant spacing and the higher nitrogen rate. However, leaf quality decreased with the high nitrogen rate and offset the higher yields in total dollar value per hectare. The quality of tobacco appeared to be influenced more by the nitrogen application than by the different plant spacings~ The most profitable treatment combination appeared to be the 76-cm spacing at the low nitrogen rate.

Sorghum and soybean were as summer crops in double-cropping systems with winter wheat on southern Piedmont soils. Wheat following sorghum had significantly less take-all than wheat following soybean over three growing seasons at two sites. Site one had no history of take-all and site two had a history of severe take-all. Sorghum also reduced take-all on wheat when grown as the summer crop in 2 of the last 3 yr compared with a continuous soybean summer crop at site one. (…)