Abstract
Soil quality deterioration, especially in intensive cropping systems, has become a serious problem for crop productivity; consequently, strategies for sustainable crop production and soil health are urgently required. Experiments on fields were organized to investigate the impact of organic manures on crop productivity, soil physiochemical properties and soil water availability in a maize-based cropping system. The experiment consisted of five treatments, including organic manures (OM) and inorganic nitrogen, phosphorus and potassium (NPK) fertilizers applied separately and in combinations: NPK = 250-150-125 Kg/ha (recommended rate), farmyard manure (FYM) = 16 t/ha, poultry manure (PM) = 13 t/ha, NPK + FYM = 150-85-50 Kg/ha + 8.5 t/ha and NPK + PM = 150-85-50 Kg/ha + 7.0 t/ha. The results showed that the combination of OM with mineral fertilizers increased crop productivity, fertilizer use efficiency and yield sustainability indices over the treatments amended with sole application of mineral fertilizers and OM. The analysis of undisturbed soil samples during different crop growth stages revealed that the addition of OM decreased the bulk density and increased the pore volume of soil at the beds of 0-20 and 20-40 cm. The application of OM to the soil not only increased saturated hydraulic conductivity of the soil but also improved total available and readily available water contents to the plants, especially when FYM was included at 16 t ha(-1). Soil-water retention properties recorded over the entire seven-day monitoring period following irrigation in the OM-amended treatments were consistently higher than the sole mineral NPK application treatments. When testing the soil nutrient status during different crop growth stages, it was noted that by adding OM into the soil not only the status of the organic carbon of soil, extractable N and K and available P contents is increased, but the duration of their availability to the plants are also enhanced. The results of the study show that organic manures addition is of major significance for maintaining soil quality and crop production sustainably, and should be advocated in the nutrient management strategies of intensive water- and nutrient-demanding cropping systems.