Mulch and no-till impacts on nitrogen and phosphorus leaching in a maize field under sub-tropic monsoon climate

Abstract Mulching and no-till are recommended practices to conserve soil water and soil health, but their effects on nutrient leaching in maize fields under monsoon rainfall need to be assessed. Soil water, soil temperature, and root and shoot growth of maize under plastic mulch, straw mulch, and no-till treatments were observed. Nitrogen (N) and phosphorus (P) leaching below a 110-cm deep lysimeter after heavy rainfall events were determined. The mulching and no-till treatments increased soil water content by 0.022–0.025 cm3/cm3 and reduced daytime soil temperature by 0.5–2.6 °C. Average leaching concentrations of total N and available P at 63 and 93 DAS (days after sowing) were 2.4 and 4.9 mg N/L and 0.12 and 0.08 mg P/L, respectively. For the control condition, the leaching concentrations of N and P decreased between 63 and 93 DAS. The mulching treatments did not influence nutrient leaching load at 63 DAS, but at 93 DAS the N leaching load increased by 181–248 g/ha and P load by 3.1–4.9 g/ha compared with the control treatment. The mulch treatments had taller shoots (5.1–18.3 cm) and a higher root-shoot ratio. The higher soil water content in the mulched treatments facilitated nutrient redistribution, plant growth, nutrient transport, and leaching. No-till increased N leaching by 103 g N/ha per leaching event but not P leaching. The no-till treatment had shorter shoots but longer roots than the conventional tillage treatment due to poor nutrient redistribution in the no-till soil. A modification in the nutrient management plan is needed to better control nutrient redistribution and minimize leaching.