The effects of the lengths of rice-crawfish rotations on the soil physicochemical properties of paddy fields

An integrated agricultural system of rice ( Oryza sativa L.) planting and crawfish ( Procambarus clarkia ) breeding has been widely practiced in southern China due to its important economic benefits. Evaluating effects of this new agricultural model on the soil physicochemical properties of paddy fields is vital for sustainable rice production. Consequently, a field experiment was carried out to examine the impacts of the durations of rice-crawfish (RC) rotations on soil pH, bulk density, porosity, soil organic carbon, total nitrogen (N), available nutrients, cation exchange capacity (CEC), and the total quantity of reducing substances at soil depths of 0–20 cm, 20–40 cm, and 40–60 cm.The rice yield and its components were also determined. The mid-season rice monoculture was set as CK. The durations of the RC rotations were 1, 7, 13, 18 and 23 years, designated RC1, RC7, RC13, RC18 and RC23, respectively. The results showed that the soil organic carbon, total N, available nutrients (N, phosphorus and potassium), porosity, and CEC in the 0–20 soil depths all increased with an increase in the time of the RC rotation. This suggests that a long-term RC rotation could improve the soil carbon and nutrients. However, the soil bulk density, and total amount of reducing substance decreased with the continuation of RC rotations. The RC rotations of 7–23 years significantly increased effective panicle number, spikelet number and grain filling percentage, and consequently produced greater grain yield. However, the long-term of RC rotations increased total amount of soil reducing substance below 20 cm depth. Therefore, rice-crawfish rotation for more than 7 years could improve soil physicochemical properties in the plough layer (0–20 cm soil depth) of paddy fields and grain yield of rice, but increase the risk of soil gleying below 20 cm depth. • Rice-crawfish (RC) rotations (up to 23 years) impacts on the soil physicochemical properties of paddy fields were investigated. • The available nutrients (N, phosphorus and potassium) contents in the 0–20 soil depths increased with the RC rotation. • The RC rotation enhanced rice yield by improving effective panicle number, spikelet number and grain filling percentage.