Influence of Phosphatic Fertilizers (PROM and DAP) on Soil Microbial Diversity Across Different Plant Growth Stages of Watermelon

Phosphatic fertilizers significantly influence soil microbial communities, playing a vital role in nutrient cycling and plant growth. This study investigates the impact of Phosphate Rich Organic Manure (PROM) and Diammonium Phosphate (DAP) in different combinations on soil microflora across four growth stages (vegetative, flowering, fruiting, and harvesting) in watermelon (Citrullus lanatus) cultivation. Soil microbial populations (bacteria and fungi) were analyzed under six treatments (T0–T5) with varying PROM and DAP ratios. Results revealed that PROM application significantly (p < 0.05) enhanced microbial diversity and abundance, with the highest bacterial and fungal counts observed in T2 (75% PROM + 25% DAP) at the flowering stage: 21 ± 3 × 10⁸ CFU/g and 11 ± 2 × 10⁸ CFU/g, respectively. In contrast, T5 (100% DAP) exhibited the lowest microbial counts among treated groups at all stages. Treatments with mixed PROM and DAP displayed intermediate effects, balancing phosphorus availability and microbial sustainability. The study highlights the pivotal role of organic phosphorus sources in maintaining soil microbial health and long-term fertility. Findings support integrated phosphorus management strategies that combine PROM and DAP to optimize microbial ecology and agricultural productivity while promoting sustainable farming practices.