Improving the Nutrient Management of an Apple Orchard by Using Organic-Based Composites Derived from Agricultural Waste

Extreme weather and the declining organic matter content of soils cause serious sustainability problems in agriculture. Therefore, soil conditioner composites (chicken manure, bentonite and super absorbent polymer) were developed and tested in an integrated apple orchard characterized by poor nutrient and water management to study their effects on soil, leaf and fruit attributes. Composites with higher doses of additives increased soil organic carbon by 4–9 g/kg, and organic nitrogen by 1.8–2.8 g/kg compared to the control (p < 0.05). Similarly, soil nitrate content steadily increased from 8–10 mg/kg to 30–38 mg/kg by composites. Composites effectively elevated leaf N, K, Ca, and Mg while not affecting the leaf P (p < 0.05). Treatments significantly enhanced the yields by 14–63% on average compared to the control. Treatments with bentonite improved the fruit weight by 2% and 24% compared to the chicken manure. On average, composite treatments increased the titratable acidity of fruits by 26–43% compared to the control and 0.5–10% compared to the treatment containing solely chicken manure. Overall, the developed organic-based composites are able to cope with changing circumstances that could help mitigate the negative effects of climate change, especially in arid areas, thus contributing to sustainable nutrient management.