| Previous researches indicated that, intercropping, an important agricultural system for meeting local food demands and ensuring food security in china can enhance crop yield and also increase utilization of resources due to below-ground root interactions between intercropped species. Selecting the appropriate nitrogen and phosphorus fertilizer rate can reduce the waste of resources and environmental pollution, which make for the sustainable agriculture production in china. A field experiment with different treatments of nitrogen(N) application rates (0,120,180,240 kg ha-1) and phosphorus (P) application rates (0,35,70,105 kg ha-1) and a root barrier pot experiment with no barrier were conducted in 2013 and 2014 year to study the effects of different N application rates and P application rates on dry matter accumulation and translocation, yield and N, P nutrition and use efficiency of maize in maize-soybean relay strip intercropping systems along with their interspecific promotion and mechanism. The research purpose of this article is to improve the use efficiency of N、 P nutrition and provide theoretical basis for rational application of fertilizer in maize-soybean relay strip intercropping system. The main results were as follows:1 Effects of interspecific interactions and nitrogen and phosphorus fertilization on maize yield in maize-soybean relay strip intercropping systemThere was significant yield advantage of the maize-soybean relay strip intercropping system, yield advantage of intercropping were mainly the results of interspecific and nitrogen and phosphorus application. Nitrogen fertilizer has a greater advantage of maize yield in particular the P application rate of 70 kg ha-1. Inter-specific interactions promoted yield by 14%(NO) and 5%(N2) when P application amount was 0 kg ha-1; when P application amount was 70 kg ha-1, the yield increased by 18.59%(NO) and 20.43%(N2).Appropriate N and P application can obvious ameliorate maize ear traits, increase 1000-kernel weight, promote intercropping maize high yield formation. Maize yield was also significantly influenced by fertilizer in field experiment, maize yield increased with increasing N application rates up to 180 kg N ha-1 under the same rate of P application,then decreased when N application rate was 240 kg N ha-1, the effect of P application rates on maize yield were:P2>P3>P1>P0, the N application rate of 180 kg N ha-1 and P application rate of 70 kg ha-1 reached to the highest yield in field experiment.Compared with the treatment of no N and P application, yield significantly improved by 14.71%.2 Effects of interspecific interactions and nitrogen and phosphorus fertilization on N and P accumulation and translocation and use efficiency of maize in maize-soybean relay strip intercropping systemInterspecific interactions significantly influence maize N and P accumulation. N accumulation in maize increased when growing without root barrier with an increase of 9.95%(N0P0),3.66%(N0P2),23.04%(N0P0) and 10.54%(N0P0); P accumulation increased by 25.58%(N0P0),28.85%(N0P2),18.75%(N2P0) and 14.75%(N2P2). The interaction between N and P application rates was significant on nutrient accumulation, increasing nitrogen application rate can promote N accumulation of maize, relieve the interspecific competition absorption of P.The accumulation, translocation and use efficiency of N and P were impacted by nitrogen and phosphorus fertilizer. N and P accumulation respectively reached to the highest with N application rate of 180 kg N ha-1 and P application of 70 kg ha-1, at the same treatment, N and P accumulation and translocation in stem and leafs were higher than other treatments, the harvest index of grain were more than 0.5. N and P agronomy efficiency were obvious higher than other fertilizer treatments, which respectively reached to 3.36 kg kg-1 and 8.79 kg kg-1. N and P absorption efficiency and production efficiency decreased significantly with the increasing of P application rates.3 Effects of N and P fertilization on dry matter accumulation and translocation of maize in maize-soybean relay strip intercropping systemThe variation trend of dry matter accumulation of maize in different periods were coincident which were significantly influenced by N application rates under the same P application rates, dry matter accumulation of maize increased with increasing N application rates up to 180 kg N ha-1, and then decreased when N application rates was 240 kg N ha-1. Dry matter accumulation of maize was the highest with the N application rate of 180 kg N ha-1,compared with the NO, N application rates was beneficial to improve dry matter accumulation and translocation to grain,promote harvest index. Compared with P0, P1-P3 treatments had a greater maize dry matter accumulation of 7.41%,13.52% and 10.47% in harvest stage.4 Effects of N and P fertilization on soil nutrition and enzyme activity in maize-soybean relay strip intercropping systemThe fertilization was significantly affected the soil layer nitrogen of maize strip in maize-soybean relay strip intercropping system.Further increasing N application rates further increase the total N in soil layer at the same rate of P application. Where 240kg N hm-2 was applied, the soil layer has the highest total N. Increasing the N application appropriately enhanced the content of available nitrogen, and the trend was similar in all growth stage, showed that:N2>N1>N3>NO. Furthermore, it was effected by the phosphorus fertilization; increasing P application rate induced the content of soil available nitrogen, PO treatment was higher than the other phosphorus fertilization treatments. Increasing nitrogen and phosphorus application appropriately can be attributed to the improve the content of total P, whereas excessively N application due to the decreasing of total P of soil layer. The rapidly-available phosphorus was significantly effected by the P application, with the phosphorus fertilization increasing, the rapidly-available phosphorus increased, and P3 treatment was 6.04 mg kg-1 which has the highest content.The soil acid phosphates activity was influenced significantly by the fertilization. Compared with PO treatment, the calcium superphosphate application significantly suppress the soil acid phosphates activity, the trend showed that:P0>P1>P2>P3. The soil acid phosphates activity has significant difference in N application at the same P application rate, while it was increased with the increasing N application. When it was over the 180 kg N hm-2, the soil acid phosphates activity was reduced. As the maize growth, the trend of soil urease activity was "low-high-low", and it was highest in the filling stage. The urease activity of soli layer increased with the increasing of P application rates at each growing stage, and reached to the top with P application rate at 105 kg ha-1, which was higher than other treatments under the same N application rates. The urease activity increased mostly with the increasing of N fertilizer when N application rate was 0-180 kg N ha-1,when N application amount was more than 180 kg N ha-1,the urease activity was decreased. |
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