Growth and gas exchange in cowpea plants under different managements and saline
            conditions

Joana Gomes de Moura,Alexandre Bosco de Oliveira,Weslley Costa Silva,Leonardo Elias Ferreira,Tatiana Maria da Silva

doi:10.5935/1806-6690.20170088

Abstract

The cowpea is one of the main crops of economic and social importance in the northeast of Brazil. However, the growing need to increase crop yield has prompted the use of irrigation water with high levels of salts. The aim of this study therefore, was to evaluate the effects of different irrigation depths and rates of liquid biofertilizer on growth and gas exchange in cowpea plants under saline conditions. The experiment was conducted in a randomized block design, using a scheme of split lots consisting of four irrigation depths with saline water (75, 100, 125 and 150% of crop evapotranspiration - ETc) and sub-lots of four different doses of biofertilizer (0; 5,000; 10,000 and 15,000 L ha-1). At 75 days after sowing (DAS), readings were taken of gas exchange in the plants (photosynthesis, stomatal conductance, internal CO2 concentration and transpiration), and growth analyses were carried out (plant height, leaf area and total dry matter). An increase in irrigation depth gives an increase in total dry weight and leaf area. Increasing irrigation depth causes a significant increase in gas exchange, with quadratic behavior noted for photosynthesis and stomatal conductance, and linear behavior for internal CO2 concentration and transpiration. The application of high doses of biofertilizer gives increased stomatal opening of the cowpea leaves.

Highlights

The cowpea [Vigna unguiculata (L.) Walp] is one of the main subsistence crops in the north and northeast of Brazil, especially in the semi-arid region of the northeast (ANDRADE JUNIOR et al, 2014)
At 75 days after sowing (DAS), readings were taken of gas exchange in the plants, and growth analyses were carried out
Increasing irrigation depth causes a significant increase in gas exchange, with quadratic behavior noted for photosynthesis and stomatal conductance, and linear behavior for internal CO2 concentration and transpiration

Summary

INTRODUCTION

The cowpea [Vigna unguiculata (L.) Walp] is one of the main subsistence crops in the north and northeast of Brazil, especially in the semi-arid region of the northeast (ANDRADE JUNIOR et al, 2014). When used unwisely, especially under the conditions of a semi-arid climate (high temperatures and low rainfall), it can cause serious problems with salinization, reducing crop productivity and soil use capacity (RHOADES; KANDIAH; MASHALI, 2000). Sousa et al (2013), evaluating the effect of saline water in the cowpea, saw a reduction in plant growth for an increase in the electrical conductivity of the irrigation water. The application of irrigation depths greater than the needs of the plant efficiently reduces the accumulation of salts in the soil, as the applied water fraction percolates below the root zone, leaching a part of the accumulated salts (ASSIS JÚNIOR et al, 2007). The aim of this work was to evaluate the effects of different irrigation depths and doses of liquid biofertilizer on growth and gas exchange in cowpea plants under saline conditions

MATERIAL AND METHODS

RESULTS AND DISCUSSION

CONCLUSIONS