Date of Graduation

5-2014

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Roberts, Trenton L.

Committee Member

Slaton, Nathan A.

Second Committee Member

Moldenhauer, Karen A.

Third Committee Member

Richardson, Michael D.

Abstract

Rice (Oryza sativa L.) is one of the most important global cereal crops and is grown on a substantial number of hectares in Arkansas each year. Consequently, Arkansas is the leading rice producing state in the United States accounting for almost half of domestic production. The development and release of N-STaR (Nitrogen-Soil Test for Rice) allows producers to predict site-specific N fertilizer needs for rice production in Arkansas, with N-STaR being a predictor of potentially mineralizable-N. Furthermore, poultry production is a thriving commodity in Arkansas, producing a substantial amount of poultry litter (PL) annually. Rice producers are applying PL to their land either as a fertilizer source or to restore productivity to precision leveled fields and using the N-STaR to determine N fertilizer recommendations. However, N-STaR has not been sufficiently researched on soils that have recently received an application of PL, potentially leading to an over or under recommendation in N fertilizer as a result of N contained in the PL. Therefore, the first research objective was to evaluate the ability of N-STaR to quantify N release from a pelletized PL application and identify how a PL application influences N-STaR recommendations over time in a field study. Results of this study indicated that the N-STaR method used in this study was very sensitive to slight changes in potentially mineralizable-N following PL applications resulting in small changes in alkaline hydrolyzable-N (AH-N) being statistically significant. Following typical PL application rates of 2240 and 4480 kg litter ha-1, the N-STaR N rate recommendation only decreased by 3 and 8 kg N ha-1, respectively. Alkaline hydrolyzable-N and N-STaR are reasonable predictors of potentially mineralizable-N from pelletized PL, indicated by the ability of N-STaR to quantify differences in potentially mineralizable-N from the addition of PL over a 45 cm deep soil sample. The second objective of this study was to quantify how different sources of PL, varying in moisture and composition, influence N-STaR soil test values and inorganic-N concentrations in a 60-d aerobic soil incubation study to determine guidelines for soil sampling protocols to determine N fertilizer recommendations. Significant fluctuations in AH-N, NH4-N, and NO3-N were observed within the first 15 d of the experiment. After the 15 d extraction time, changes in N were minimal and equilibrated for the further duration of the study. Information relating to the influence of PL on N-STaR soil test values allow us to ensure that the proper N recommendation is determined using N-STaR following a PL application. Our results show that the direct steam distillation method quantifies AH-N in the soil and PL indicating the importance of soil sampling time for N recommendations for rice using N-STaR following a PL application. This study demonstrates the ability to design soil sampling protocols, recommending that rice producers applying PL need to delay at least 15 d following a PL application before collecting soil samples for N recommendations using N-STaR.

Download

Share

COinS