Abstract
Nitrogen (N) management is of great importance in rice production, but most previous studies have focused on high N rates and there is a lack of research on management plans under a moderate N rate. This study aimed to explore the agronomic and physiological traits of N-efficient rice varieties (NEVs) and to optimize the management strategy at an N rate below the inflection point of the parabolic curve between N rate and grain yield. Two NEVs and two N-inefficient rice varieties (NIVs) were planted, and three treatments were designed according to the panicle N application method. A larger amount of N applied at panicle initiation (PI) led to higher rice yield and N-use efficiency (NUE). This was mainly due to increases in the total number of spikelets per unit area, root oxidation activity, leaf area duration, and leaf photosynthesis rate as well as to the increased carbon (C) and N utilization rates. Compared with NIVs, NEVs exhibited improved root and shoot functions and higher C and N transport characteristics at the moderate N rate. We suggest that increasing the application of N at PI and that planting of NEVs are important ways to increase rice yield and NUE when adopting moderate N rates.
Highlights
China is the world’s largest producer and consumer of N fertilizer [1,2]
52.4 de Nitrogen management is a key step in improving the N-use efficiency (NUE) of rice fields, and it is of great importance in rice production and environmental protection [23,24]
We observed that, at a moderate N rate, a higher amount of N applied at panicle initiation (PI) led to higher yield and NUE of N-efficient rice varieties (NEVs), and it was not necessary to apply further N fertilizer at the spikelet differentiation stage
Summary
China is the world’s largest producer and consumer of N fertilizer [1,2]. For a long time, increasing N application rate has been one of the most effective measures to increase the yield of rice (Oryza sativa L.) [3,4]. Since 2000, rice yields have increased slowly, with an average annual growth rate of less than 0.5% (Figure 1a). The N rates in China and Jiangsu province are 75% and 200% higher than the world average, respectively [5,6]. To stabilize and improve rice production at moderate N levels, N-fertilizer strategies must be improved by growing rice varieties with increase grain yields and N-use efficiency (NUE). This will aid in mitigating environmental costs while meeting the food demand of a growing population [10]
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