Summary of nitrogen soil test for rice (N-STaR) nitrogen recommendations in Arkansas during 2020

ABSTRACT

Seeking to fine-tune nitrogen (N) application, increase economic returns, and decrease environmental N loss, some Arkansas rice (Oryza sativa L.) producers are turning away from blanket N recommendations based on soil texture and cultivar and using N-STaR (Nitrogen Soil Test for Rice) to determine their field-specific N rates. In 2010, Roberts et al. correlated several years of direct steam distillation (DSD) results obtained from 0 to 18-in. soil samples to plot-scale N response trials across the state to develop a field-specific, soil-based N test for Arkansas rice. After extensive small-plot and field-scale validation, N-STaR is available to Arkansas farmers for both silt loam and clay soils (using 0 to 12-in. soil samples). To summarize the samples submitted to the N-STaR Soil Testing Lab in 2020, samples were categorized by county and soil texture. Samples were received from 24 fields across 11 Arkansas counties. Total samples received were from 9 clay and 15 silt loam fields. Sample submission was depressed this season due to COVID-19, but expectations are that sample numbers will increase for the 2021 growing season. The N-STaR N-rate recommendations for these samples were compared to the producer's estimated N rate, the 2020 Recommended Nitrogen Rates and Distribution for Rice Cultivars in Arkansas, and the standard Arkansas N-rate recommendation of 150 lb N/ac for silt loam soils and 180 lb N/ac for clay soils. Each comparison was divided into 3 categories based on a decrease in the recommendation, no change in recommended N rate, or an increase in the N rate recommendation. Neither county nor soil texture was found to be significant factors in any of the comparisons made in this year's data, yet the same general trends seen in previous years were observed.