| Nitrogen fertilizer overused and low use efficiency in agricultural system leads to wasting of resources and environment pollution, which bad for the sustainable agricultural production. In order to improve the N use efficiency in maize-soybean intercropping system, a two-year field experiment was conducted to investigate the effect of different N application rate and distance on dry matter accumulation and translocation, characteristics of grain filling, N-fertilizer utilization efficiency of maize and soybean, soybean nodule nitrogenase and crop yields in maize-soybean relay strip intercropping system, establish the relationship of each index and find out the optimal fertilization distance and best nitrogen fertilizer for the Maize-Soybean Relay Strip Intercropping system. The experiment included three N application rates (210,270 and 330 N kg ha-1, which represent reduced 36%(RN36%),18% (RN18%), and conventional N application amount (CN), respectively) and four fertilize locations (the N fertilizer were applied in the area between the maize and soybean plant rows, the distance from the fertilize locations to maize rows were 0 cm (D1),15 cm (D2),30 cm (D3) and 45 cm (D4), respectively). The main results showed as follows:1> Collaboration fertilization (RN2 and D2 or D3) in the maize-soybean relay strip intercropping system could promote the dry matter accumulation and translocation, increase the grain filling rate, grain number per spike and 100-kernel weight of maize and soybean. With the advance of growth stage, the dry matter accumulation of maize and soybean follow the crop growth curve. With the reducing of nitrogen application rates, the dry matter translocation and its rate, rate of contribution to grain of maize and soybean increased at first and decreased subsequently. The maximum values of the indices occurred at the treatment of RN2. Compared with the conventional rate of N application (CN), the dry matter translocation and rate, rate of contribution to grain of maize and soybean at the reduced 18%N application rate (RN2) were increased by 22.65%,18.75%,15.90% and 47.83%,34.04%,27.07%, respectively. The fertilization effect is optimal when the distance is between 15 and 30 cm. Compared with the conventional rate of N application (CN), the average filling rate and the maximal filling rate of maize at the reduced 18%N application treatment (RN2) were significantly increased by 9.79% and 10.76%. At the same time, the average filling rate and the maximal filling rate of soybean were increased by 32.59% and 32.44%.2、Collaboration fertilization (RN2 and D2 or D3) in the maize-soybean relay strip intercropping system could promote absorption and accumulation of nitrogen, reduces the use of soil nitrogen, improve N utilization efficiency (NUE) and maintain soil fertility. The amount of nitrogen accumulation (NA) in vegetative organs of maize and soybean declined as a single apex curve with the incensement of the plant age. With the reducing of nitrogen application rates, the amount of Nitrogen uptake, the N agronomy efficiency (NAE), the N uptake and N use efficiency (NUE) of maize and soybean increased at first and decreased subsequently. The maximum values of the indices occurred at the treatment of RN2. Compared with the treatment of CN, the amount nitrogen of seed in maize and soybean, the plant nitrogen uptake of intercropping system at the treatment of RN2 were increased by 4.65%,6.91% and 5.10%, respectively. At the same time, the N agronomy efficiency (NAE) of maize, soybean and the intercropping system were increased by 58.03%,56.11% and 59.79%, the N utilization efficiency (NUE) were increased by 35.13%, 55.37% and 43.62%, respectively. The fertilization applied distance affects significantly the N uptake and utilization of maize and soybean. The fertilization effect is optimal when the distance is between 15 and 30 cm. As the amount of N fertilizer decreased by 18%(RN2), the N uptake of plants, N utilization efficiency and the total nitrogen content of maize, soybean and the intercropping system improved significantly at the treatments of D2, comparing with the treatment of CK1, but N contribution rate of soil reduced notably.3、Collaboration fertilization (RN2 and D2 or D3) in the maize-soybean relay strip intercropping system could promote the root growth and improve nodule nitrogen potential of soybean. During V5-R5 period, the fertilization applied distance affects significantly the number and weight of nodule, the dry weight and volume of root, the number of first-order lateral root and the length of main root. The fertilization effect is optimal when the distance is 15 cm between the fertilization dot and the narrow row corn. With the advance of growth stage, the content of leghemoglobin per plant tended to increase, the maximum appeared at the R5 stage, the nitrogenase activity per plant increased at first and decreased subsequently, the maximum appeared at the R2 stage. The fertilization applied distance affects significantly the content of ureide in different organ of soybean, the content of leghemoglobin and the nitrogenase activity per plant, the treatment of D2 was the highest, compared with the control group (CK1), the content of leghemoglobin per plant in different growth stages (V5, R2, R5) was respectively higher by 87.50%,72.22% and 51.23%, and the nitrogenase activity per plant was respectively higher by 87.88%,18.68% and 72.8%.4、Collaboration fertilization (RN2 and D2 or D3) in the maize-soybean relay strip intercropping system could improve the grain yield of maize, soybean and the intercropping system. Compared with the conventional rate of N application (CN), the grain yield of maize, soybean and the intercropping system of RN2 were increased by 4.95%, 7.74% and 5.47%, respectively. The fertilization effect is optimal when the distance is between 15 and 30 cm. With the reduced 18% N application rate, the grain number per spike and 100-kernel weight of maize at the treatment of D2 were higher than D1 by 9.08% and 4.75%, the grain number per plant and 100-kernel weight of soybean at the treatment of D2 were higher than D4 by 24.75% and 2.37%. |
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