Effect of soil amendments on grain yield, yield components, and milling qualities in organic rice production

Abstract Nitrogen (N) management has been identified as a major challenge for producers to maintain a profitable crop yield under an organic rice (Oryza sativa L.) production system compared to the conventional production system. Field experiments were conducted in 2010, 2015, and 2017 to evaluate the impact of different types and rates of organic soil amendments on grain yield and milling qualities. A Texas rice variety, Presidio, was arranged in a randomized complete block (RCB) design with three replications in the 2010 study, while another variety, Tesanai‐2, was arranged in an RCB design with four replications in the 2015 and 2017 studies. Of the six organic N fertilizers (AgriRecycle, Maxim Compost, Nature Safe, Rhizogen, True, and Top Organic Fertilizer) tested in the 2010 study, five fertilizers showed a linear increase in grain yield with increasing N supply, and two of them, Nature Safe and Rhizogen, demonstrated a numerically higher fold increase in grain yield per unit N application (10‐ and 7‐fold, respectively) compared to other soil amendments. Additional field studies conducted in 2015 and 2017 using a selected organic fertilizer, Nature Safe, showed a significant increase in grain yield (p < 0.001) and plant height (p < 0.001) by the N rates. Similarly, milling quality parameters, including whole grain percentage and whole grain yield, were also significantly enhanced (p < 0.001) by the application of Nature Safe organic fertilizer. Nevertheless, yield plateaus were not observed even at higher N doses in all three studies, indicating that agronomically high N application is recommended to achieve the cultivar yield potential.