Enhancing Soybean Productivity in Saline Soil Conditions: Synergistic Effects of Organic Fertilizer and Proline Co-Application

Efficiently optimizing strategic crop production in Egypt's degraded soils is imperative to address the nutritional gap and ensure food security. Consequently, a field trial was conducted over two consecutive summer seasons (2022 and 2023) to evaluate the potential impact of various organic fertilization sources as the main plots on soybean plant cultivated in soil with an EC value of 6.45 dsm-1. The organic treatments included a control group without organic fertilizers (I0), farmyard manure (FYM) compost (I1), plant residues (PR) compost (I2) and chicken manure (ChM) compost (I3). Additionally, the subplots were designated for foliar applications of proline amino acid, with three groups: F0 (without foliar application, serving as the control), F1 (proline at a rate of 60 mg L-1), and F2 (proline at a rate of 100 mg L-1). The study assessed various parameters at two stages: 80 days from sowing, focusing on growth indicators such as plant height, foliage fresh and dry leaf weights, and chlorophyll content and antioxidant indicators. At the harvest stage, yield-related parameters and quality aspects like the number of pods per plant, seed yield, oil, protein, carbohydrates, along with the analysis of soil nutrient availability. The results obtained illustrated that ChM compost (I3) proved to be the most effective organic source in promoting optimal performance under salinity conditions, as evidenced by superior growth indicators, yield-related parameters, and quality. Following closely was PR compost (I2), with FYM compost (I1) ranking third, while the control group (without organic fertilizers) exhibited the lowest performance. In addition, the findings highlight the positive impact of proline amino acid on enhancing plant tolerance to salinity stress, with performance improvements correlating with increased proline levels. The sequence of proline treatments, ranked from most effective to least, was F2, followed by F1, then F0 (without proline). Analyzing soil fertility at the harvest stage, all organic sources positively influenced the availability of N, P, and K, with ChM compost (I3) demonstrating superior effects. The influence of proline was nearly negligible in this aspect. Overall, the combined treatment of I3 x F2 emerged as the most distinguished among the various interactions studied. Therefore, integrated approaches that combine optimal organic fertilization practices with proline applications, such as the studied combination of ChM compost and proline, should be promoted for enhanced soybean production. Ongoing research is essential to refine and expand these recommended practices for a comprehensive and sustainable approach to soybean cultivation in challenging soil conditions.