Nursery Fertilizer Application Increases Rice Growth and Yield in Rainfed Lowlands with or without Post-Transplanting Crop Stress

Abstract

In rainfed lowlands, the beneficial effects on rice (Oryza sativa) yield from fertilizing the seedling nursery may depend on the occurrence of water and nutrient stress after transplanting into the mainfield. The aim of the study was to test the effect of seedling age and nursery fertilisation on rice yield when plants experienced nutrient and water stress regimes after transplanting. The first experiment, conducted during the wet season in a low-fertility rainfed lowland field in south-east Cambodia, examined the effect of three levels of nitrogen (N), phosphorus (P) and cow manure (CM) application to the nursery and three ages of seedlings at transplanting (4, 6 and 9 weeks after sowing: WAS) on the growth of a traditional photoperiod-sensitive rice cultivar. Increasing fertilizer application to the nursery increased shoot dry weight and grain yield at each age of seedling transplanted. Shoot dry weight and grain yield from seedlings transplanted 6 WAS were 20% and 10% higher than those from the seedlings transplanted at the other ages. Seedlings transplanted at 4 WAS, which experienced a temporary submergence for 3 days after transplanting, recorded 5% greater seedling mortality from the unfertilized than fertilized nursery soil. The taller seedlings transplanted at 6 WAS experienced less mortality despite more severe submergence. The second experiment was conducted at seven rainfed lowland sites across Cambodia to test the benefit of N alone and N+P application to the nursery on rice yields in farmers’ fields. In four out of seven trials, grain yield increases averaged 13% with N+P applied to the nursery whereas N alone increased grain yield at two sites and depressed yield at two. Overall, fertilizer application in the nursery produced more vigorous seedlings with higher nutrient concentration which survived submergence and grew better with or without drought or nutrient stress after transplanting, leading to increased yields of rice. The beneficial effect of nursery fertilizer was additional to any obtained by fertilizer applied to the main field at or after transplanting.