Effects of straw compost retting on runoff, sediment and phosphorus loss from sloping farmland

Objective  To seek more effective agronomic measures to reduce runoff, sediment and phosphorus loss emissions under the combination of different stacking methods and straw returning densities.

Method  Under the conditions of natural rainfall, different straw returning densities (0.75, 1.5 kg·m⁻²), different straw crushing particle sizes (1, 5 cm), adding water or urea were designed to study the effects on runoff and sediment amount, and phosphorus loss of slope farmland in the middle of Yunnan.

Result  The straw density of 1.5 kg·m⁻², straw particle size of 5 cm, and water retting could effectively reduce the runoff and sediment yield of tobacco slope farmland by 18.59%–38.60%, 12.50%–38.60%, 10.6%–38.60%. Compared with the treatments of 1.5 kg·m⁻² straw density, 1 cm straw particle size, and water and urea retting, 0.75 kg·m⁻² straw density, 5 cm straw particle size, and water-added could decrease runoff and sediment total phosphorus and runoff PO₄⁻-P concentration by 2.82%–66.67%, 0.38%–57.53% and 1.97%–64.73% respectively. The ratio of PO₄⁻-P in runoff was 35.30%–77.59% of the total phosphorus concentration. Straw density of 0.75 kg·m⁻², straw particle size of 5 cm, and water retting could effectively reduce the risk of phosphorus loss in tobacco sloping farmland in Erlongtan small watershed. The total phosphorus loss in runoff and sediment respectively highestly reduced 63.64% and 64.74%, 63.89% and 57.87%, 63.89% and 64.74%.

Conclusion  The use of 0.75 kg·m⁻² straw density, 5 cm straw particle size and water retting treatment can control phosphorus loss in central Yunnan watershed and reduce the risk of runoff, sediment and phosphorus loss on slope farmland.