Mitigating Osmotic Stress and Enhancing Developmental Productivity Processes in Cotton through Integrative Use of Vermicompost and Cyanobacteria

Abstract

There is an urgent demand for biostimulant amendments that can sustainably alleviate osmotic stress. However, limited information is available about the integrated application of vermicompost and a cyanobacteria extract on cotton plants. In 2020 and 2021, two field experiments were carried out in which twelve combinations of three irrigation intervals were employed every 14 days (Irrig.14), 21 days (Irrig.21), and 28 days (Irrig.28) along with four amendment treatments (a control, vermicompost, cyanobacteria extract, and combination of vermicompost + cyanobacteria extract) in salt-affected soil. The integrative use of vermicompost and a cyanobacteria extract resulted in an observed improvement in the physicochemical attributes; non-enzymatic antioxidants (free amino acids, proline, total soluble sugars, and phenolics); and antioxidant enzyme activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) and a decrease in the levels of oxidative damage indicators (H₂O₂ and MDA). Significant augmentation in the content of chlorophyll a and b, carotenoid concentration, relative water content, stomatal conductance, and K⁺ was also observed. In conjunction with these findings, noticeable decreases in the content of Na⁺ and hydrogen peroxide (H₂O₂) and the degree of lipid peroxidation (MDA) proved the efficacy of this technique. Consequently, the highest cotton yield and productivity as well as fiber quality were achieved when vermicompost and a cyanobacteria extract were used together under increasing irrigation intervals in salt-affected soil. In conclusion, the integrated application of vermicompost and a cyanobacteria extract can be helpful for obtaining higher cotton productivity and fiber quality compared with the studied control and the individual applications of the vermicompost or the cyanobacteria extract under increasing irrigation intervals within salt-affected soil. Additionally, it can also help alleviate the harmful impact of these abiotic stresses.

Keywords: Spirulina; blue-green algae; cotton; cyanobacteria; deficit irrigation; drought; salt-affected soil; vermicompost.

Figure 1

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on (A) exchangeable Na percentage (ESP) in the soil and the content of (B) sodium (Na) and (C) potassium (K) and (D) the K/Na ratio in the leaves of cotton plants grown in salt-affected soil and at three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 2

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on the concentration of (A) chlorophyll a, (B) chlorophyll b, (C) ratio between chlorophyll b/a, and (D) carotenoid content in the leaves of cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 3

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on (A) relative water content (RWC) and (B) stomatal conductance (gs) in the leaves of cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 4

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on the stress indicators (A) hydrogen peroxide (H₂O₂) and (B) malondialdehyde (MDA) in the leaves of cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 5

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on non-enzymatic antioxidants (A), free amino acids, (B) proline, (C) total soluble sugars, and (D) total phenolics in the leaves of cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 6

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on enzymatic antioxidants, namely, (A) superoxide dismutase, (B) peroxidase, and (C) catalase, in the leaves of cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 7

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on (A) plant height, and (B) total leaf area in cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.

Figure 8

Influence of applying vermicompost (VC) and cyanobacteria extract (CB) on fiber quality parameters—(A) Pressley index and (B) Micronaire reading—on cotton plants grown in salt-affected soil and under three irrigation intervals (14, 21, and 28 days) during the 2020 and 2021 growing seasons. The data of both seasons are presented as means ± SD, and the significance levels of *, **, and *** indicate p-values of less than 0.05, 0.01, and 0.001, respectively.