Residual Effects of Long-Term Application of Rice Straw and Cow-Dung Compost on Soil Fertility and Growth of Rice (Oryza sativa) Plants

Abstract

Organic amendments are recognized for enhancing soil fertility and crop productivity by improving nutrient availability and yield while reducing reliance on costly chemical fertilizers. Despite their benefits, limited research exists on the long-term effects of rice straw (RS) and cow-dung compost (CP) on soil fertility and rice yields, particularly in regions like Zambia where rice production remains below demand. This study evaluated the residual effects of long-term combined application of rice straw and cow-dung compost with chemical fertilizers on soil fertility and rice growth dynamics. A two-year (2021–2022) pot experiment was conducted using Gley Lowland soil from Yamagata University, Japan, subjected to four treatments: chemical fertilizer only (CT), RS + chemical fertilizer, CP + chemical fertilizer, and RS+CP + chemical fertilizer. Soil chemical properties (pH, total C, N, available P, K) and rice growth parameters (tiller count, plant height, dry weight, yield components) were analyzed. Statistical comparisons were performed using ANOVA and Tukey’s HSD test (p < 0.05). The RS+CP treatment significantly enhanced soil fertility, increasing available N (25.7–31.1%), P (22.8–36.7%), and K (133.4–225.1%) over CT, alongside higher organic matter content. Rice growth and yield improved, with RS+CP increasing tiller count (22.5%), plant height (6.7%), and grain yield (30.7%) in 2021, with consistent trends in 2022. CP alone also showed notable benefits, while RS had variable effects. The synergistic effects of RS and CP improved nutrient retention and soil structure, leading to sustained productivity. The slower nutrient release from organic materials delayed early growth but ultimately enhanced yield. These findings align with integrated nutrient management strategies, offering cost-effective solutions for smallholder farmers. Long-term combined application of rice straw and cow-dung compost with chemical fertilizers significantly enhances soil fertility and rice yields. This approach supports sustainable rice production by balancing immediate nutrient availability with long-term soil health, advocating for wider adoption in resource-limited agricultural systems.