Growth, gas exchange and photochemical efficiency of the cowpea bean under salt stress and phosphorus fertilization

Abstract

Cowpea is widely cultivated in semiarid regions; however, these regions face serious problems with salinity of water and soil, thus constituting an abiotic stress that limits the development of this species. The objective of this study was to study the influence of phosphate fertilization on the morphophysiological components of cowpea plants irrigated with salinized water during the vegetative and reproductive phase. The research was carried out in a greenhouse from September to December 2015. A randomized complete block design with treatments arranged in a 5 x 3 factorial scheme with five replications was used. The factors consisted of the use of five levels of electrical conductivity of irrigation water: 0.5; 1.5; 2.5; 3.5 and 4.5 dS m-1 and three doses of phosphorus corresponding to 60%, 100% and 140% of the dose recommended for the culture that was 60 kg ha-1. The plants of cowpea cv. Paulistinha were cultivated in lysimeters with a capacity of 8 dm3. At 30 and 49 days after sowing, periods corresponding to the vegetative (V4) and reproductive (V8 / R1) phases of the culture were evaluated gas exchange, chlorophyll fluorescence and growth. The increase in the electrical conductivity of the water reduced the growth, the photochemical activity and the phytomass accumulation of the cowpea plants, independent of the phenological phase. The higher dose of simple superphosphate increased the growth and photosynthetic activity of cowpea, mainly in the reproductive phase; Independent of the salinity of irrigation water.

Mulch with sugarcane bagasse and bamboo straw attenuates salt stress in cowpea cultivation

“…The effect of increasing salts in irrigation water provided lower values due to stress-induced stomatal closure, besides reducing CO 2 assimilation (Melo Filho et al, 2017;Magalhães et al, 2020). Similar results to the present study were verified by Sá et al (2018) in bean plants in soil without mulch.…”

“…It should be noted that this result provided by the mulch coverings (sugarcane bagasse and bamboo straw) reduced the evaporation of water from the soil, providing greater water retention and consequently WUE. Lima et al (2018) describe similarity to the data in this study for water-use efficiency at high salinity levels in cotton crops.…”

“…The results obtained in the treatment without cover possibly show the effect of salts on the soil, especially Na + , reducing the rate of water infiltration, stimulating the formation of a layer with greater density, which hinders growth, respiration, and root expansion (Schossler et al, 2012;Sá et al, 2018). Sousa et al (2018a), when assessing the interaction between irrigation water salinity and mulch, found similar results in corn plants grown in soil without mulch.…”

“…Saline water use is one of the abiotic stresses that most limit plant growth and development, and consequently, agricultural production worldwide (Souza et al, 2019). Salt stress cause stomatal closure, reducing transpiration rate, internal CO 2 concentration, and photosynthetic rates (Sá et al, 2018). It should be noted that according to Ayers & Westcot (1999), the cowpea crop has a salinity threshold of 2.3 dS m -1 .…”

Phosphorus doses alter the ionic homeostasis of cowpea irrigated with saline water

“…Irrigation with saline water reduces growth, photosynthesis and biomass accumulation of cowpea (Oliveira et al, 2017;Sá et al, 2018). Such reduction may be related to phosphorus deficiency, since the decrease in P cycling between the cytoplasm and stroma, caused by nutrient deficiency, can lead to decreases in the consumption and production of ATP and NADPH, reducing plant photosynthesis (Sá et al, 2017).…”