Irrigation strategies with saline water and phosphate fertilization in cowpea culture

Abstract

The use of saline water negatively affects gas exchange and plant growth. However, fertilization with a mineral source has been used to mitigate salt stress on agricultural crops. The objective of this study was to evaluate the gas exchange and the initial growth of cowpea beans submitted to different irrigation strategies with saline water and phosphate fertilization. The experiment was conducted from October to December 2019, in full sun in the experimental area belonging to the Universidade da Integração Internacional da Lusofonia Afro-Brasileira (UNILAB), Redenção, CE, Brazil. The experimental design was entirely randomized in a 4 × 2 factorial scheme, referring to four irrigation strategies: E1 = irrigation with low-salinity water (0.3 dS m -1 ) at germination, initial growth, and preflowering stages; E2 = saline water (3.2 dS m -1 ) at preflowering only; E3 = saline water (3.2 dS m -1 ) on germination and initial growth; E4 = saline water (3.2 dS m -1 ) in the three phases, and two doses of phosphate fertilization (P1 = 50% of the recommended phosphorus dose and P2 = 100% of the recommended phosphorus dose), with four repetitions. Continuous salt stress in phenological phases negatively affects plant height, photosynthesis, transpiration, stomatal conductance, and leaf temperature of the cowpea crop. The dose of 100% phosphate fertilization mitigates the effects of continuous salt stress on chlorophyll pigment production.

Efficiency of Nitrogen Fertilization in Millet Irrigated with Brackish Water

“…In our study, it was found that increasing the dose of N intensified the effect of salt stress on CO 2 assimilation compared to control plants. This indicates that the increase in nitrogen concentration under conditions of salt stress may have caused a nutritional imbalance, impairing the absorption of other essential nutrients for photosynthesis such as Mg 2+, as well as leading to the accumulation of Na+ and/or Cl-ions in the chloroplasts, affecting the biochemical and photochemical processes involved in photosynthesis [29,30]. [31] showed that nitrogen fertilizations of 60 and 120 kg ha-1 provide greater photosynthesis, transpiration, stomatal conductance, and internal CO 2 concentration in millet plants using lower salinity water throughout the cycle or using brackish water from 30 and 45 days after sowing.…”

Efficiency of Nitrogen Fertilization in Millet Irrigated with Brackish Water

“…In our study, it was found that increasing the dose of N intensified the effect of salt stress on CO 2 assimilation compared to control plants. This indicates that the increase in nitrogen concentration under conditions of salt stress may have caused a nutritional imbalance, impairing the absorption of other essential nutrients for photosynthesis such as Mg 2+ , as well as leading to the accumulation of Na + and/or Cl − ions in the chloroplasts, affecting the biochemical and photochemical processes involved in photosynthesis [29,30]. Increasing the amount of N fertilizer applied tends to prolong the longevity of functional leaves and increases chlorophyll content, thus improving photosynthetic capacity [28].…”