When the soil contains the necessary quantity of macro- and micronutrients, high-quality okra pods can be produced. By mixing chemical fertilizers with organic biofertilizer, the integrated nutrition management (INM) system addresses the latent demand for micronutrients in addition to N, P, and K. This method promotes sustained agricultural production in addition to restoring soil fertility. The current study's results confirmed that the INM-50% (RDCF + FB-BW) treatment enhanced the nutritional status of the soil and, as a result, the vegetative characteristics of Abelmoschus esculentus (okra).
Well-ripened banana fruits were combined with cow dung and cow urine to prepare fermented banana waste biofertilizer. The nutrients contained in fruit, cow dung and cow’s urine were thus recovered. According to Muniappan et al. [9], the biofertilizer made from fermented banana waste has a pH of 6.72 ± 0.05. There were nutrients such as N, P, K, Ca, Mg, S, Fe, Zn, Cu, Pb, and Mn, and phosphate solubilizers dominated the bacterial population. In the current study, comparatively little difference was observed in soil pH between the various treatments. The slightly lower pH of the soil in Group 3 was due to the addition of fermented banana waste fertilizer, which was slightly acidic in nature. The microbial population in FB-BW produces organic acids, which chelate and mobilize minerals, especially phosphorus, and make them available to plants.
When FB-BW is combined with N-P-K, Group 4's soil organic carbon content increases. This was due to the interactive effects between chemical fertilizer and organic biofertilizer. In the current study, FB-BW when mixed with 50% chemical fertilizer, has improved the soil's nutrient content. The urease, phosphatase, and dehydrogenase activities of soil microbes, which mobilize nutrients, increase their solubility, and enable their uptake by roots and plants, may also be responsible for the improvement in nutritional status of soil. Following the addition of organic manure with chemical fertilizer, Saha et al. [13] and Chaudhry et al. [14] have noted improvements in soil properties such as moisture retention capacity, organic carbon, particle density, porosity, pH, organic matter, soil microbial biomass, total nitrogen, and available P and K status.
The soil organic carbon gained after integrated nutrient management practices is retained for a longer time, thereby withstanding the temperature-induced organic matter breakdown that happens in tropical countries like India [15]. Therefore, the combination of inorganic fertilizer and FB-BW creates an environment that is conducive to increased soil microbial biomass and enzymatic activity. The root architecture and root aeration are also improved in organic manure/INM practice [16]. Thus, the observed improvement in soil quality parameters will improve the growth of lady finger and also retain nutrients in the soil for a longer time.
The physiological traits of plants, like root length and root morphology, play a vital role in determining their health and yield potential of okra. In the current study, okra plants treated with INM- 50% (RDCF + FB-BW) had a longer primary tap root with more lateral roots and root surface area than the other treatments. The maximum absorption of nutrients and water from the soil and their transfer to the shoot system by the lateral roots will increase photosynthesis and plant growth as observed in INM-50% (RDCF + FB-BW) treatment [17, 18]. The current study's observation of better root architecture can be attributed to the interaction between plant growth-promoting rhizobacteria and FB-BW biofertilizer, which provides nutrients and phytohormones to shape the roots. When organic manure loaded with rhizobacteria that promote plant growth was applied to okra, a similar alteration in root architecture was seen [19].The Group 4 okra plants' larger stem girth was caused by an adequate supply of potassium, which makes the stem of the plant robust and larger and prevents the plant from withering too quickly. Because there was less potassium present in Group 1 (water-control) okra plants' the meristematic growth, leaf area expansion, chlorophyll-promoting activity, and protein synthesis were reduced [20].
The major macronutrient that supports the vegetative growth of plants is nitrogen. The increase in okra plant height in the INM-50% (RDCF + FB-BW) treatment was due to the sufficient amount of nitrogen in the soil that promotes cell division, enlargement of new cells, increases the level of cytokinin, and also aids in the absorption of phosphorus and potassium. As nitrogen moves throughout the plant tissue and gets attracted to the younger tissue, the continuous cell division has led to an increase in plant height and a greater number of leaves [21]. The enlarged stem girth observed in Group 4 okra plants was contributed by a sufficient amount of potassium that makes the plant stem sturdy and bigger, so the plant will not wither easily.
The adequate translocation of iron and magnesium as well as the increased activity of the enzymes involved in chlorophyll biosynthesis may also be contributing factors to the increase in chlorophyll concentration in Group 4 [22, 23]. Mishra et al. [24] found that the chlorophyll content of okra exhibited the favorable effects of chemical fertilizer when mixed with organic manures (neem oil cake, poultry manure, vermicompost, FYM, biofertilizer, and sea weed extract). The integrated nutrient management approach of combining chemical fertilizer with vermicompost and farmyard manure has improved the vegetative, reproductive, and yield aspects of okra, according to identical findings published by Ruby et al. [25].
The observed higher content of protein in okra leaves treated with INM (50%) (RDCF + FB-BW) was due to the optimal availability of nitrogen, phosphorus, and potassium provided by inorganic fertilizer. Mirudkar et al. [26] have also reported similar findings in okra when chemical fertilizer was combined with farmyard manure. Many studies have reported that the combination of organic manure and chemical fertilizer outnumbers the effects of chemical fertilizers or organic manure when added individually. The results of the present study confirmed that the efficacy of 50% chemical fertilizer was pronounced when combined with 50% FB-BW. Improvements in soil nutritional status and consequently vegetative features have been brought about by the micronutrients and microbial population in FB-BW, which have conditioned the soil to support PGPR.