Improving grain yield and reducing N loss using polymer-coated urea in southeast China

Abstract

The efficiency of classical mineral NPK fertilizers is usually low because a major part of these fertilizers does not reach plant roots and ends up polluting groundwaters with nitrates and phosphates. Recently, a novel polymer-coated urea made from recycled plastics was proposed to enhance N availability in cereal production. To evaluate the efficiency of this polymer for rice production, we set up field plots, microplots, and pot experiments with 15N tracing. We compared rice yield, N uptake, and N loss between conventional three split applications of urea and a single basal application of four derivatives from the polymer-coated urea. The four derivatives included a blend with 70 % of N from 6 % (w/w) coated urea and 30 % from urea and three coated urea fertilizers with 6, 8, and 12 % coating at an identical N application rate during two rice-growing seasons. Results show that 6 % coated urea improved 15N recovery, reduced 15N loss, and increased grain yield slightly due to an initial 15N burst occurring at high field temperatures after basal fertilization; 8 or 12 % coated urea better met plant N demand from transplanting to heading, greatly enhanced 15N recovery, and decreased 15N loss and NH3 volatilization. Nevertheless, unlike a significant increase of yield for 12 % coated urea, 8 % coated urea did not increase yield due to 15N release and excessive 15N uptake by plants at ripening. Overall, our findings show that a single basal polymer-coated urea application improves N use efficiency and reduces N loss in rice agroecosystem.