Long-Term Agronomic Practices in Reducing Nitrogen and Phosphorus Loss from Intensive Croplands

Eutrophication is increasing with intensive agricultural activities as a global environmental challenge, especially in developing countries. In order to establish the effects of long-term reducing fertilization and straw returning on nitrogen (N) and phosphorus (P) loss in surface runoff due to intensive cultivation in the Yangtze River basin, China, we conducted a 7-year field pilot experiment with rice-wheat rotation in the fifth largest fresh water lake basin. The treatments included no fertilization (CK), conventional fertilization (Conv. Fert.), optimized fertilization (Optim. Fert.), nitrogen reduction by 30% (70%N), P reduction by 50% (50%P), and N reduction by 30% and P reduction by 50% + straw returning (70%N50%P+Straw). Results showed that the average wheat yields in reducing fertilizer treatments (70%N, 50%P, and 70%N50%P+Straw) slightly decreased by 1.21%, 5.26%, and 1.17%, respectively, compared to those with the optimized fertilizer, whereas average rice yields slightly increased by 3.71%, 0.64%, and 1.23%, respectively. However, the reducing fertilizer treatments (70%N50%P+Straw) significantly reduced the loss of N and P in surface runoff compared with Conv. Fert. and Optim. Fert. Total P and dissolved P in surface runoff water in rice seasons was predictable and modeled. The annual average N, P, and K fertilizer efficiency for rice-wheat rotation ranged in 21%–42%, 12%–38%, and 35%–53%, respectively. Considering the yields of rice and wheat along with eco-environmental benefits of reducing N and P loss in surface water, 70%N50%P+Straw treatment was the best treatment for Chaohu region. This long-term field study recommends the employment of the reduced chemical fertilizer by 30% N and 50% P in Chaohu basin for rice and wheat crops with the maximum reduction of runoff N and P and the highest fertilizer (N and P) efficiency with reasonable high crop yields. This is especially important for farmers in developing countries in achieving economical, ecological, and environmental benefits in sustainable modern agriculture to feed the increasing global populations.