Precise delivery of nitrogen at tillering stage enhances grain yield and nitrogen use efficiency in double rice cropping systems of South China

Nitrogen fertilizer management substantially affects the growth, productivity, and nitrogen use efficiency (NUE) of rice production systems. To assess the effects of precise application of nitrogen fertilizer at tillering stage as 'tillering-fertilizer' on grain yield and nitrogen use efficiency, field trials were conducted in the late season of 2019 and 2020, in addition to a radioisotope 15N tracer experiment. The experiment was comprised of four N fertilizer treatments i.e., no fertilizer application as a control (T1), traditional surface broadcast fertilization (90 kg N/ha as basal fertilizer and 60 kg N/ha as tillering fertilizer, T2), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 45 kg N/ha as tillering fertilizer at 10 cm depth, T3), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 30 kg N/ha as tillering fertilizer at 10 cm depth, T4) and two rice cultivars i.e., Wufengyou 615 and Yuxiangyouzhan. Results showed that grain yield remained 18.8% and 12.4% higher owing to increase in productive panicles and grain filling, 42.2% and 38.9% higher nitrogen agronomic efficiency, 4.6% and 10.4% higher nitrogen recovery efficiency, and 10.2% and 7.8% higher nitrogen physiological efficiency in T3 than T2 for Wufengyou 615 and Yuxiangyouzhan, respectively. Moreover, nitrogen derived from fertilizer in T3 was increased by 8.0% and 4.4% compared to T2 for Wufengyou 615 and Yuxiangyouzhan, respectively whereas the residual rate of T3 was increased by 31.5%. In addition, the T3 treatment substantially enhanced the leaf area index and leaf chlorophyll content that led to improved photosynthesis and the activities of enzymes related to nitrogen metabolism. Overall, 45 kg N/ha as tillering fertilizer at 10 cm depth and surface broadcast at 90 kg N/ha as basal fertilizer can improve grain yield as well as nitrogen use efficiency in late season rice production system of South China.

Automated summary

This study investigated the effects of precise application of nitrogen fertilizer at the tillering stage on grain yield and nitrogen use efficiency in rice production. The results showed that deep placement of tillering fertilizer at a depth of 10 cm, with a basal fertilizer application of 90 kg N/ha and a tillering fertilizer application of 45 kg N/ha, significantly increased grain yield and nitrogen use efficiency.