Integration of mixed-cropping and rice-duck co-culture has advantage on alleviating the nonpoint source pollution from rice (Oryza sativa l.) production

Abstract

With the rapid development of agricultural industrialization, agricultural nonpoint source pollution, which occurs when synthetic chemical additives (e.g. fertilizer, pesticides, and herbicides) runoff into rivers or lakes, has become a major concern. To explore the approaches of reducing the application of chemical additives, we conducted a field experiment to test whether the integrated farming systems would alleviate the nonpoint source pollution. Specifically, we tested whether mixed-cropping or mixed-cropping plus duck co-culture (MCDC) systems with optimized rice (Oryza sativa L.) cultivars could reduce nutrients runoff or leaching from paddy field. We found that compared to the mono-cropping systems, the electrical conductance (EC), oxidation-reduction potential (ORP), the contents of dissolved oxygen (DO), nitrates (NO3-), ammonium (NH4+), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) of paddy water in MCDC systems all increased during the rice-growing stages. The contents of the TN, TP, and TK of paddy water in MCDC systems were 45.35%, 52.43% and 40.47% higher than those in the mono-cropping systems, respectively. Compared to the conventional mono-cropping, the mixed-cropping systems could alleviate nonpoint source pollution by decreasing the application of synthetic chemicals to rice paddies, the rice-duck co-culture system had significantly lower additions of agro-chemicals to paddy fields, which decreased the loss/runoff/leaching rates of nitrogen, phosphorus and potassium from paddy fields into the surrounding water areas by 32.73%, 8.72% and 31.88%, respectively. Considering that the MCDC systems exerted similar/even better performances as/than the rice-duck co-culture system and the rice mixed-cropping system, we deduced that the MCDC systems could also could alleviate nonpoint source pollution to a certain extent.