Little research has been done in the humid mid-Atlantic region to develop full-season N fertilizer recommendations for dryland no-tillage grain sorghum (Sorghum bicolor L. Moench) production. The objectives of this study were: (i) to determine the optimum rate of band-placed starter N fertilizer needed in combination with side-dress N applications to achieve economic grain yields, (ii) to investigate if pre-plant broadcast N applications are as efficient as band-placed plus side-dress N applications, (iii) to evaluate the response of grain sorghum yield to partitioned side-dress N applications, and (iv) to study the influence of residual soil profile mineral-N (nitrate and ammonium) on sorghum response to applied N fertilization. Multi-location field studies were conducted over three years. A range of N treatments of various starter-band and side-dress N rates were applied. The experimental data indicate that an optimum rate of N fertilization depends on residual soil mineral-N. Little or zero starter-band-N in conjunction with side-dress-N applications of 130 kg of N ha-1 for soils testing high in mineral-N ( 50 kg N ha-1 in the top 0.3m of surface soil) at planting, and a starter-band-N supplement of 40 kg N ha-1 in conjunction with 130 kg N ha-1 side-dress N for soils testing low in mineral-N at planting, optimized the grain sorghum yields in these experiments. Broadcast N applications were observed to be as efficient as band placed N applications when followed by rainfall soon after application. Grain sorghum yields did respond to the partitioned side-dress N applications. However, partitioning of side-dress N application again depends on the residual mineral-N level present in the soil. In order to consider residual soil mineral-N in making N fertilizer recommendations "Associated Nitrogen Fertilizer Equivalency" (ANFE) values were calculated. ANFE is the amount of applied N that has potential to produce the same yield as that produced by the residual soil mineral-N. The N fertilizer recommendations based on ANFE values were quite close for two out of four sites as compared to the N rates at which the maximum yields were obtained in this study. / Ph. D.

This research was focused on increasing the efficiency of upland cotton production in the northern cotton belt through the use of new fertilizer formulations, placement, and timings. The objectives of the experiments reported in this thesis were to: 1) evaluate the effects of side-dress potassium (K), sulfur (S), and boron (B) formulation and application timing on tissue nutrient levels during the bloom period; 2) evaluate lint yield response of cotton to different formulations of nitrogen (N), K, S and B applied at side-dress; and 3) compare 5x5 banding (5 cm beside and 5cm below the seed) and deep placement of complete N-P-K-S blends to current nutrient management strategies on early season plant growth, nodes above white flower, total nodes, petiole nutrient concentrations during bloom, and lint yield. Tissue S and B concentrations were increased more often than K concentrations when the nutrients were applied with side-dress N. When evaluating P and K placement, petiole P levels were found to be significantly higher in unfertilized plots when no side-dress N was applied. Phosphorus and K placement and/or rate had no effect on lint yield when N was applied at side-dress during the study. Environmental conditions potentially influenced the response to P and K placement as 5x5 placement produced yields significantly higher during 2013 growing season at location 1, while deep placement produced significantly higher yields in 2014 at location 3. As a result, Virginia nutrient management recommendations for cotton have been updated to incorporate management strategies to maximize lint yields. / Master of Science