Agroecological soil amendment in watermelon systems: synergistic effects of rock dust and poultry manure on nematode suppression and yield improvement

Watermelon is a globally important fruit threatened by plant-parasitic nematodes (PPNs). Effective soil health management through agroecological amendments is crucial for sustainable watermelon production in nematode-infested fields. This study investigated the synergistic effectiveness of rock dust (RD) and poultry manure (PM) as sustainable soil amendments for suppressing PPNs and enhancing watermelon yield. A two-trial field experiment was conducted using a randomized complete block design with three replications. The experimental treatments included 2.5 t/ha of RD and PM applied alone or in combination, 5 t/ha of RD and PM applied alone or in combination, and 0 t/ha (unamended control). Observations were made regarding growth and yield characteristics, and nematode communities were assessed at both planting and harvest stages. The collected data were subjected to analysis of variance using SAS 2002 software, and means were differentiated using Fisher's LSD at p < 0.05. Nine genera of PPNs were identified in the watermelon fields, including Meloidogyne, Pratylenchus, Hemicycliophora, Helicotylenchus, Rotylenchus, Scutellonema, Longidorus, Aphelenchus, and Tylenchus. The results indicated significant (p < 0.05) reductions in the populations of the nine PPN genera under amended treatments, with population declines ranging from 73% to 100%. Moreover, the combined RD and PM treatment at 5 t/ha yielded the highest productivity per hectare (36,250 and 36,916 in Trials 1 and 2, respectively), significantly exceeding the control (12,500). This study demonstrates that the synergistic integration of RD and PM as soil amendments effectively suppresses PPNs and enhances yields by leveraging rock dust's mineral enrichment and PM's organic nutrient release, offering dual benefits for soil health and nematode suppression. These findings highlight RD+PM amendment as a sustainable approach to mitigate nematode damage, improve yields, and reduce reliance on synthetic nematicides, ensuring food security and enhancing farmer profitability in watermelon production systems.