Organic rice is cultivated on 14,000 hectares in the U.S., with California as the top producer, growing 6,000 hectares primarily in the Sacramento Valley. Here, high clay soils have historically limited cover crop growth, leading to nitrogen (N) application mainly via poultry litter (PL). However, recent PL shortages have prompted growers to explore alternative organic fertilizers, whose effectiveness under flooded conditions is uncertain.

This study aimed to assess four organic fertilizers, including PL, on (1) rice yields, (2) nitrogen recovery efficiency (NRE), (3) N mineralization rates under anaerobic conditions, and (4) economic viability. Field trials took place in two adjacent sites in 2009, one continuously flooded (CF) and the other drained for a month post-sowing to manage weeds. The drained field experienced delayed growth and harvest.

Using a nitrogen-responsive rice variety (S-102), the trials compared four fertilizers: PL (3% N), pelleted feather meal (12% N), a mix of PL and feather meal (6% N), and pelleted bone and blood meal (13% N), alongside an unfertilized control. Each treatment received 134 kg/ha of N, with organic phosphorus and potassium applied universally.

Results showed grain yields ranged from 7,055 to 10,072 kg/ha, with control yields averaging 7,166 kg/ha, significantly lower than fertilized treatments. Pelletized fertilizers generally yielded 25% more than controls, while PL yields were lower than those from pelletized options but higher than controls.

NRE for pelletized materials varied between 25-50% in the CF field versus 21-31% in the drained field, with N uptake increasing throughout the growing season. Anaerobic incubation revealed that N mineralization was initially rapid, slowing after 36 days. After 60 days, mineralization rates were 22% for 13-0-0, 33% for 12-0-0, 26% for 6-3-2, and only 14% for PL, indicating PL’s inadequacy for crop demands.

Returns on investment for CF fields ranged from 57% to 76%, with PL offering the lowest profit increase. In contrast, returns in the drained field were minimal (-18% to 19%), suggesting limited value in fertilization under prolonged drainage. Further research is needed to optimize fertilizer timing and rates for better economic outcomes in both field types.