The two methods for determining N-fertilizer recommendations for rice (Oryza sativa L.) in Arkansas are the standard N recommendation (SR) based on soil texture, previous crop, and rice cultivar, and the Nitrogen-Soil Test for Rice (N-STaR) which quantifies the potentially mineralizable-N of the soil and provides a site-specific N recommendation. The N-STaR program has recently been developed, and the validation of N-STaR for clay soils is an important step in ensuring that N-STaR predicts correct N-fertilizer rates for rice under a delayed-flood production system. Small-plot trials located across Arkansas compared the N-STaR 95 and 100% relative grain yield (RGY) N rates applied as a single preflood (SPF) and a 2-way split (2-WS) application to the SR. The N-STaR N-fertilizer rate recommendations were equal to or less than the SR at all locations with differences ranging from -224 to 0 kg N ha-1. At all 13 sites, rice receiving the N-STaR 100% RGY N-fertilizer treatments yielded equal to or greater than the SR. Similar results were seen for the N-STaR 95% RGY fertilizer-N treatments, although rice receiving the 95% RGY SPF fertilizer-N rate yielded lower than the SR at three locations. The second objective was to examine potential sampling tools for their accuracy in collecting N-STaR soil samples while having the greatest ease-of-use. Alkaline hydrolyzable-N (AH-N) from soil samples collected by the N-STaR bucket and drill (BD), Kleen Hole Spade dry (KHS-D), Kleen Hole Spade lubricated with water (KHS-W), and Kleen Hole Spade lubricated with WD-40 (KHS-40) were compared against the dutch auger (DA) control. The alternative sampling methods were not statistically different in AH-N concentration from the DA, although all alternative methods had a tendency to overestimate AH-N compared to the DA and a correction value should be considered. The KHS-D showed the greatest utility in sampling clay soils and would be the best alternative method for encouraging the use of N-STaR in rice production on clay soils. In conclusion, this research validates the N-STaR N rate recommendations for rice on clay soils in Arkansas and highlights alternative sampling methods that may be employed in N-STaR soil sampling.

The Alfalfa Management Guide is designed especially for busy growers, with to-the-point recommendations, useful images of diseased plants and pests, and quick-reference tables and charts. Revised in 2011, this edition of Alfalfa Management Guide covers the latest strategies for alfalfa establishment, production, and harvest-soil testing, fertilizing, integrated pest management, rotation, and more.

Growth and development of the rice plant. Climatic environments and its influence. Mineral nutrition of rice. Nutritional disorders. Photosynthesis and respiration. Rice plant characters in relation to yielding ability. Physiological analysis of rice yield.