Non-invasive spectral detection of the beneficial effects of Bradyrhizobium spp. and plant growth-promoting rhizobacteria under different levels of nitrogen application on the biomass, nitrogen status, and yield of peanut cultivars

Salah Elsayed,Urs Schmidhalter,Mohamed Elhoweity,Salah El-Hendawy

doi:10.1590/1678-4499.076

Abstract

ABSTRACT High-throughput phenotyping using spectral reflectance measurements offers the potential to provide more information for making better-informed management decisions at the crop canopy level in real time. The aim of this study was to investigate the suitability of hyperspectral reflectance measurements of the crop canopy for the assessment of biomass, nitrogen concentration, nitrogen uptake, relative chlorophyll contents, and yield in 2 peanut cultivars, Giza 5 and Giza 6. Peanuts were grown under field conditions and subjected to 3 doses of nitrogen fertilizer with or without the application of 2 bio-fertilizers, Bradyrhizobium spp. or plant growth-promoting rhizobacteria. Simple linear regression of normalized difference spectral indices and partial least square regression (PLSR) were employed to develop predictive models to estimate the measured parameters. The tested spectral reflectance indices were significantly related to all measured parameters with R2 of up to 0.89. The spectral reflectance index values differed at the same level of nitrogen fertilizer, as well as among the 3 levels of nitrogen fertilizer application for inoculation with Bradyrhizobium and co-inoculation with Bradyrhizobium and plant growth-promoting rhizobacteria. The calibration models of PLSR data analysis further improved the results, with R2 values reaching 0.95. The overall results of this study indicate that hyperspectral reflectance measurements monitoring peanut plants enable rapid and non-destructive assessment of biomass, nitrogen status, and yield parameters of peanut cultivars subjected to various agronomic treatments.

Highlights

Nitrogen is an important element for proper plant development and reproduction because it is a component of chlorophyll, amino acids, proteins, and enzymes
The spectral reflectance index values differed at the same level of nitrogen fertilizer, as well as among the 3 levels of nitrogen fertilizer application for inoculation with Bradyrhizobium and co-inoculation with Bradyrhizobium and plant growth-promoting rhizobacteria
The overall results of this study indicate that hyperspectral reflectance measurements monitoring peanut plants enable rapid and non-destructive assessment of biomass, nitrogen status, and yield parameters of peanut cultivars subjected to various agronomic treatments

Summary

Introduction

Nitrogen is an important element for proper plant development and reproduction because it is a component of chlorophyll, amino acids, proteins, and enzymes. An efficient nitrogen supply is required for plant metabolism, and the addition of nitrogen will increase crop photosynthesis and final yields (Erisman et al 2010). (Br) and plant growth-promoting rhizobacteria (PGPR) in legume crop production has been suggested as a suitable alternative strategy to bypass the risk of chemical fertilizers (Badawi et al 2011). Enhancement of nodulation and biological nitrogen fixation of legumes by co-inoculation with PGPR microorganisms is becoming a practical way to improve nitrogen use efficiency in sustainable agricultural production systems (Bai et al 2002). PGPR can promote legume nodulation and nitrogen fixation by producing flavonoid-like compounds and/or stimulating the host plant to produce more flavonoid signal molecules (Bai et al 2002)

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