Cyanobacteria as a nutri-fertigation option for stimulating fruit quality and yield in Capsicum annuum

Abstract

The multifaceted roles of cyanobacterium-based preparations as biostimulatory and nutrient-enriching options for soil and produce were evaluated as a new facet of circular economy in Chilli, grown under protected cultivation. Tapping into their potential to fix nitrogen from the atmosphere, photosynthetically sequester C, secrete diverse metabolites, the comparative performance of four different aqueous fertigation options, as either soil drench or foliar was undertaken. The treatments included T1: Water (as Control), T2–T3: carrier-based formulations amended with cyanobacterium Anabaena laxa (A. laxa) or cyanobacterial biofilm Anabaena torulosa–Trichoderma sp. (An–Tr) respectively, and T4: 100 µM Fe-EDTA. These treatments were initiated at the pre-flowering stage and continued at weekly intervals up to 2 months. Soil drench application enhanced leaf enzymatic activities; nitrate reductase activity by 13%, carbonic anhydrase activity by 40%, and soil microbiological attributes such as soil dehydrogenase and urease activity by 11 and 19%, respectively, over control. Foliar application of treatments led to 11–12% increments in leaf pigments, 8–9% increase in ascorbic acid, and 38% increase in capsaicin content in fruits. Among treatments soil drench of An–Tr led to 1.3-fold increase in nitrate reductase activity, and number of fruits, whereas A. laxa reported 1.5-fold increase in leaf carbonic anhydrase activity, over control. PCA illustrated significant correlations among the stimulated soil microbiological activities, nutrient availability, fruit yield and quality, with soil available N, total pigments influencing yield and quality attributes positively. Cost–benefit analyses revealed that cyanobacterial treatments as nutri-fertigation options for enhancing plant growth and fruit quality led to significantly higher gross income and twofold greater benefit–cost ratio, highlighting their promise as economically viable biostimulants for chilli in sustainable horticulture.