Reduced Nitrogen Rate with Increased Planting Density Facilitated Grain Yield and Nitrogen Use Efficiency in Modern Conventional Japonica Rice

Tianyao Meng,Guisheng Zhou,Qigen Dai,Xi Chen,Huanhe Wei,Jialin Ge,Xubin Zhang

doi:10.3390/agriculture11121188

Abstract

The past three decades have seen a pronounced development of conventional japonica rice from the 1990s, although little information is available on changes regarding grain yield and nutrient use efficiency during this process. Nine conventional japonica rice released during the 1990s, 2000s, and 2010s were grown under a reduced nitrogen rate, with increased planting density (RNID) and local cultivation practice (LCP) in 2017 and 2018. The rice from the 2010s had 3.6–5.5% and 7.0–10.1% higher (p < 0.05) grain yield than the 2000s and the 1990s, respectively, under RNID and LCP. The harvest index contributed more to genetic yield gain from the 1990s to the 2000s; whereas from the 2000s to 2010s, yield increase contributed through shoot biomass. Genetic improvement increased total nitrogen (N), phosphorus (P), and potassium (K) accumulation, and their use efficiencies. The rice from the 2010s showed a similar grain yield, whereas the 1990s and 2000s’ rice exhibited a lower (p < 0.05) grain yield under RNID relative to LCP. RNID increased N, P, and K use efficiencies, particularly the N use efficiency for the grain yield (NUEg) of the 2010s’ rice, compared with LCP. For three varietal types, RNID increased the panicles per m2, the filled-grain percentage, and the grain weight (p < 0.05) while decreasing spikelets per panicle of the 2010s’ rice. Compared with LCP, RNID reduced non-structural carbohydrate (NSC) content and shoot biomass, at heading and maturity, while increasing the remobilization of NSC and the harvest index, especially for the 2010s’ rice. Our results suggested the impressive progressive increase in grain yield and nutrient use efficiency of conventional japonica rice since the 1990s in east China. RNID could facilitate grain yield and NUEg for modern conventional japonica rice.

Highlights

Rice is a staple crop worldwide, so increasing its productivity is a principal strategy for ensuring food security [1]
The 2010s’ rice had 7.0% and 10.1% higher (p < 0.05) grain yield than the 1990s’ rice under local cultivation practice (LCP) and RNID across two years, respectively
Our results indicated that the genetic yield gain from the 1990s to 2000s was mainly attributed to harvest index, shoot biomass created the best yield for the 2000s to 2010s

Summary

Introduction

Rice is a staple crop worldwide, so increasing its productivity is a principal strategy for ensuring food security [1]. Genetic improvement is recognized as a key driver in enhancing rice yields [2]. A modeling study estimated that variety improvement contributed 74% to the total increased rice production after the 1980s in China [3]. Genetic yield gain has been extensively studied across rice-growing countries [4,5,6]. Most existing literature suggests a pronounced yield increase over years; for example, Anzoua et al [6] estimated a 2.55 g m−2 year−1 yield gain of rice varieties released from 1905 to 1988 in Northern Japan. Improvements for high yield were associated with an enlarged sink size potential [6,7], an increased biomass accumulation and/or harvest index [8], an optimized plant morphology [4,9], and a coordinated source-sink balance [10,11]

Methods

Results

Discussion

Conclusion