A Greener Approach to Spinach Farming: Drip Nutrigation with Biogas Slurry Digestate

To achieve higher crop yields and maintain environmental conservation, it is imperative to adopt novel agricultural methods that improve both the quantity and quality of produce. The following study focused on investigating the effectiveness of integrated use of biogas slurry and inorganic nutrigation on spinach growth and nutrient uptake through drip irrigation. A field experiment was conducted using a split-plot design; spinach was cultivated with seven different treatments: biogas slurry nutrigation (BSN) (T1), integrated inorganic + organic nutrigation: 40% Recommended dose of fertilizer (RDF) + BSN (T2), 60% RDF + BSN (T3), 80% RDF + BSN (T4), 100% RDF (T5), slurry broadcasting (SB) (T6), and control (T7). The results showed that spinach grown with (T4) 80% RDF + BSN exhibited optimum plant height and leaf count compared to spinach under other treatments and was at par with T5 100% RDF for crop parameters. T5 treated plants demonstrated the longest roots, followed by T4 treated plants. The highest recorded yield of 5.72 tons ha−1 was achieved in treatment T5 with 100% RDF, followed closely by T4 with 80% RDF + BSN at 5.52 tons ha−1 and T3 with 60% RDF + BSN at 5.36 tons ha−1. These three treatments exhibited comparable yields, showcasing the effectiveness of incorporating biogas slurry nutrigation in conjunction with inorganic fertilizer for achieving high spinach yields. In terms of macronutrient content in spinach leaves, significant differences were found for nitrogen (N), phosphorus (P), and potassium (K) contents. Incorporating biogas slurry into the soil modified microbial enzyme activities, specifically dehydrogenase and phosphatase. Normally, alkaline phosphatase shows greater activity than acidic phosphatase, but the addition of biogas slurry equalized the enzymatic activity of both, establishing a harmonized enzymatic profile. Our results suggest that fertilizing spinach with integrated biogas slurry nutrigation (if properly filtered) + inorganic nutrigation through drip nutrigation is a viable strategy for improving the morphological parameters and productivity of spinach while also contributing to environmental preservation and a reduction in production costs.