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.