Starter Nitrogen Fertilizer Affects Rice Growth And Nitrogen Uptake But Not Grain Yield

Seedling rice (Oryza sativa L.) growth can be slow on high cationexchange-capacity clay soils, which represent the majority of rice acreage in Mississippi and elsewhere in the Mid-South US rice-growing region. Strategies to increase vigor and growth of seedling rice may be beneficial to increase yields of drill-seeded, delayed-flood rice. Studies were established during the 2007 and 2008 growing seasons in Stoneville, MS to evaluate the use of starter N fertilizer to improve growth and yield of rice conventional cultivar Cocodrie and the hybrid cultivar XL 723. Ammonium sulfate (AMS) was applied at 20 lb N/ac as starter N fertilizer at the two-leaf stage. Recovery of starter N was also determined at multiple sampling times using 15 N-labeled ammonium sulfate. Hybrid XL 723 had greater tissue N concentration when measured at VS (five-leaf stage) than Cocodrie, but Cocodrie had greater total dry matter (TDM) and total N uptake (TN U) compared with XL 723 likely due to the higher seeding rate for Cocodrie. XL 723 produced 27 and 25% greater grain yield than Cocodrie in 2007 and 2008, respectively. Recovery of 15 N was greater in XL723 compared with Cocodrie at the R1 and R3 stages but similar at V5 stage in 2007. Starter N did not increase plant height or grain yield in either variety in both years, but it increased TDM and TNU in 2008. The use of starter fertilizer does not appear to be a viable option to increase seedling vigor or grain yield of rice cultivars Cocodrie and XL 723 in Mississippi.