Determination of critical nitrogen dilution curve based on stem dry matter in rice.

Syed Tahir Ata-Ul-Karim,Xia Yao,Xiaojun Liu,Yan Zhu,Weixing Cao,Guoping Zhang

doi:10.1371/journal.pone.0104540

Abstract

Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N) requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (Nc) dilution curve based on stem dry matter (SDM) and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L.) in east China. Three field experiments with varied N rates (0–360 kg N ha−1) using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. SDM and stem N concentration (SNC) were determined during vegetative stage for growth analysis. A Nc dilution curve based on SDM was described by the equation (Nc = 2.17W−0.27with W being SDM in t ha−1), when SDM ranged from 0.88 to 7.94 t ha−1. However, for SDM < 0.88 t ha−1, the constant critical value Nc = 1.76% SDM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI) and accumulated N deficit (Nand) of stem ranged from 0.57 to 1.06 and 51.1 to −7.07 kg N ha−1, respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or Nand could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The SDM based Nc dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China.

Highlights

Estimating nitrogen (N) nutritional status is a key to investigating, monitoring, and managing cropping systems [1]
Stem dry matter and nitrogen concentration The stem dry matter (SDM) production was significantly affected by N fertilization during the growth period of rice
The increase in SDM followed a continuous increasing trend along with sampling dates for both the varieties during each year with increasing N rates from N0 to N4; there was no significant difference between N3 and N4 in all the cases (Table 1)

Summary

Introduction

Estimating nitrogen (N) nutritional status is a key to investigating, monitoring, and managing cropping systems [1]. A reliable diagnosis of crop N requirement and nutritional status give insight into optimization of qualitative and quantitative aspects of crop production It improve N use efficiency and add to environmental protection [2]. Soil and plant-based strategies are two principle approaches, extensively used to derive information about the N nutrition status of crops, for satisfying their demand for N and to minimize N losses [3]. The former rarely describes the intensity of N release over a longer period, so the latter are widely accepted and adopted. The present study investigates a plant-based strategy for an in-season assessment of N nutrition status for rice crop

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