| [Objectives] Intercropping is one of the traditional agricultural practices in China, and has played an important role in the development of ecological and modern agriculture in China even the other parts of the world. Compared to monocropping systems, intercropping always has overyielding advantage which is due to interspeific interactions and spatiotemporal niche differentation and leads to a high nutrients removal from the soil, the soil fertility will be changed by it. However, little attention has been paid to soil fertility in intercropping compared to monocultures in a long-term experiment. Therefore, a long-term experiment was established in 2009 at Baiyun site, Wuwei city, Gansu province, northwestern China. In 2013(the 5th year) and 2014(the 6th year), the productivity of crops(crop grain yields and biomass) and soil fertility(physical, chemical and biological) properties were measured after harvesting to investigate the changes of these indicators in responses to P applications and 4 different intercropping systems and their corresponding monocroppings. The objective of research was to provide scientific basis for sustainable development of intercropping.[Method] The experiment was establised in 2009, and was a two factorial design with three replicates,where main factor was three P application rates(0, 40 and 80 kg P hm2. applied as triple superphosphate)and the second factor was cropping systems, including maize/faba bean, maize/soybean, maize/chickpea and maize/rapeseed 4 different intercropping systems, and monocropping of the corresponding crop species.There were 81 plots for the field experiment.[Result](1) Compared with the monocultures, continuous intercropping significantly enhanced grain yields of crops. Chickpea/maize, faba bean/maize, soybean/maize, and rapeseed/maize intercropping overyielded by38.2%, 32.6%, 34.0% and 38.4% than their respective monocultures; Grain yields did increase significantly with the increasing of P application in two years, and reached the maximizing at 80 kg/hm2.(2) Compared with the monocultures, continuous intercropping significantly enhanced above ground N, P, K accumulation, which also increased with the increasing of P application regardless of intercropping or monocropping.(3) Phosphorus application and intercropping did not significantly alter the soil bulk density but significantly increased the soil infiltration rate, expecially at 80 kg P hm2. Intercropping significantly increased the water stable large macro-aggregates(>2 mm) and decreased the free silt and clay particles(<0.106 mm).(4) Intercropping and P application significantly increased the content of soil organic matter in 2013,but not in 2014. P application significantly increased the content of soil organic matter in two years.Intercropping decreased soil Olsen P and available K. Neither P application nor cropping systems had any effect on soil total nitrogen concentration; There was no significant difference in soil p H under different P applications between cropping systems in both 2013 and 2014.(5) Compared with monoculture, continuous intercropping significantly enhanced soil acid phosphatase and soil urease activities. But they did not change by different P applications. While both the different P applications and cropping systems could not change the soil nitrate and sucrase activities in two years[Conclusion]We can conclude that intercropping can increased crop yields. After continuous intercropping, nutrient uptake was significantly higher than monoculture in all four intercropping systems, and also can maintain or improve soil physical and biological properties, even keep the basic soil chemical index steady state at the same time. Rational fertilization can alleviates the declines of some soil fertility indicators like Olsen-P and exchangable K. In summary, intercropping is a sustainable cropping system that can increase crop yields and maintain soil fertility in a long-term scale. |
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