In Quest of Nitrogen Use-Efficient Rice Genotypes for Drought-Prone Rainfed Ecosystems

Biswajit Karmakar,Jatish Chandra Biswas,Aminul Islam,Stephan M Haefele,Amelia Henry,Md Humayun Kabir

doi:10.3389/fagro.2020.607792

Abstract

Nitrogen (N) use efficiency in rainfed agriculture is generally low because of poor management and unavailability of suitable rice genotypes. There is a need to select rice genotypes with high N use efficiency for these specific environments, which was investigated at the Bangladesh Rice Research Institute, Regional Station, Rajshahi, in two successive years. The performance of six rice genotypes, IR7437170-1-1, BR7873-5*(NIL)-51-HR6, IR83377-B-B-93-3, International Rice Research Institute (IRRI) 123, IR83381-B-B-6-1, and Binadhan-7, were tested under four N rates (0, 55, 83, and 110 kg N ha−1) in a strip-plot design. Grain yields generally increased up to 83 kg N ha−1 and declined thereafter. Depending on N rates, mean grain yields increased by 35–45% compared to the control (N0). However, the grain yields of IR83377-B-B-93-3, IRRI 123, and Binadhan-7 increased up to 110 kg N ha−1. N uptake and its use efficiencies were the highest in IR83377-B-B-93-3, which was at par with those in IRRI 123. Bangladesh Rice Research Institute (BRRI) dhan56 and Binadhan-7 showed intermediate performance, while BRRI dhan57 and IR83381-B-B-6-1 showed lower N uptake and N efficiencies. Between 16.5 and 19.2 kg N uptake was required to produce 1 ton of paddy. The genotypes IR83381-B-B-93-3 and IRRI 123 were the most N use efficient irrespective of N rates, but BRRI dhan57 and IR87781-B-B-6-1 were observed to be inefficient genotypes, while BRRI dhan56 and Binadhan-7 were intermediate. Thus, this study indicates the need to test existing and new germplasm for optimal N rates and their NUE, especially in rainfed environments where optimized resource use is essential for higher yields and increased farmers' income.

Highlights

More than 50% of rice fields (5.1 m ha) in Bangladesh are rainfed (Karmakar et al, 2015), which may experience early, intermittent, or terminal drought, hampering yields and contributing to inefficient use of added inputs
The mean grain yield increased by 35–45% depending on the N rate compared to the control (N0)
There was a significant difference in harvest index among the treatments in that the harvest index increased with greater N rates up to N83 and declined

Summary

Introduction

More than 50% of rice fields (5.1 m ha) in Bangladesh are rainfed (Karmakar et al, 2015), which may experience early, intermittent, or terminal drought, hampering yields and contributing to inefficient use of added inputs. N is the most yield limiting in different agroecological zones of the world (Fageria and Baligar, 2005), and the utilization efficiency of applied N in rainfed systems is lower than in irrigated lowland rice ecosystems (Haefele et al, 2008). Uptake of applied N is typically less than 40% in cereal crops (Raun et al, 2002); Nitrogen Use Efficient Rice Genotypes this low uptake is associated with N losses from the soil through leaching, denitrification, and volatilization (Fageria and Baligar, 2005). Many studies worldwide have been accomplished on nitrogen use efficiencies of rice genotypes under water stress (Haefele et al, 2008; Wu et al, 2016); limited research has been conducted on genotype selection for increased NUE under rainfed environments in Bangladesh. It could be an important step to improve rice yield through better use of applied and indigenous soil N

Results

Discussion

Conclusion