Rice productivity and profitability with slow-release urea containing organic-inorganic matrix materials

Applying slow-release fertilizers is possible means for reducing nitrogen (N) loss in rice production. Matrix-based fertilizers represent novel slow-release fertilizers. To date, there is little consensus about the effect of combined addition of organic and inorganic matrix materials on rice production. We developed a slow-release urea fertilizer with selected organic and inorganic matrix materials. The study aimed to:i) determine the effect of the slow-release urea on rice yield, profit, and agronomic efficiency and ii) elucidate its possible mechanisms. A two-year field experiment was conducted during 2015-2016. Besides, laboratory experiments were conducted to determine the potential N loss risk. Three treatments were set up:control without N application (CK), regular urea treatment (RU, 150 kg N ha^-1), and slow-release urea treatment (SU, 150 kg N ha^-1). The results showed that rice biomass and grain yield were significantly higher in SU than in RU (P < 0.05). The higher panicle density in SU was largely responsible for the greater grain yield. Net profit in SU was > US$450 ha^-1, higher than in RU. Agronomic efficiency was significantly greater in SU than in RU (P < 0.05). Rice height, root area, leaf chlorophyll, leaf nitrate reductase activity, and leaf glutamine synthetase activity were larger in SU than in RU. Less N loss and greater soil N availability were partly responsible for the improvements in rice growth traits and physiological parameters in SU. Overall, the slow-release urea is a promising fertilizer for rice production.