| The scientific and reasonable intercropping patterns can make full use of environmental resources by the complementary effects of crops.The cereal/legume intercropping with high and low ecological position compound population is an efficient planting practice.Due to the difference in plant type,the canopy structure is formed,which significantly improves the ventilation and light transmittance.At the same time,the complementary utilization of environmental resources enhanced the nutrient absorption and crops transformation,increased the grain yield,and improved the land-use efficiency.However,the light environment and growth of mung bean were affected by intercropping.In the early stage of growth stage,the root nodule development has not been fully completed,and the nitrogen fixed by nodules cannot satisfy the crop growth without additional soil nitrogen inputs.Therefore,the application of nitrogen fertilizer is the main measure to meet the mung bean nitrogen demand.The growth characteristics were analyzed to explore the regulation of nitrogen（N）fertilizer of low-lying crops under the intercropping mode.Therefore,it is of great significance to explore the productive capacity of cultivated land,improve N use efficiency by analying the efficient combination of planting system and N fertilizer.The field experiments were conducted in 2018 and 2019 using split-plot design with two cropping patterns[proso millet-mung bean intercropping（PM）and soled mung bean（SM）]and four total N fertilizer application rates[0（N0）,45（N1）,90（N2）,and 135 kg hm-2（N3）].The dry matter accumulation and yield components of mung bean in the intercropping system were studied as well as the growth characteristics such as photosynthetic characteristics of leaves.N accumulation of organs and the effects of N fertilizer on its absorption,and the utilization of intercropping mung bean and rhizosphere soil microenvironment were analyzed.The main conclusions are as follows:（1）Compared with monoculture,intercropping increased plant height,decreased stem diameter and significantly reduced pod number of mung bean.Suitable N application improved the agronomic traits and significantly increased the number of pods per plant.N application remarkably increased aboveground dry matter accumulation,100-grain weight and yield of mung bean at the maturity,which was 11.8%–29.8%,1.2%–5.5%and 10.6%–18.6%higher than N0 treatment,respectively.The yield of intercropped mung bean was significantly and positively correlated with plant height,stem diameter and pod number per plant.The average land equivalent ratio was 1.74–1.98 over the three years,which was greater than 1,showing the superiority of intercropping and be used as the extension planting pattern in the northwest arid area.The highest land-use efficiency and grain yield were observed at 90kg·hm-2,and the intercropping advantage under high fertilization was restrained.（2）Compared with N0 treatment,the net photosynthetic rate and transpiration rate increased by 7.6%–17.8%and 12.6%–27.5%in the intercropping system,respectively.Similarly,the actual photochemical efficiency of PSⅡincreased by 9.7%–26.2%,and the non-photochemical quenching coefficient decreased by 7.4%–16.6%,which enhanced the activity of PSⅡreaction center and effectively regulated the adaptive response of the photosynthetic system to shading.Nitrogen application influenced its distribution in leaves,increased the proportion in light-harvesting system,delayed leaf senescence,and further enhanced the ability of light energy capture and weak light utilization.The response of photosynthetic performances of intercropping leaves to N fertilizer was greater than that of monoculture.However,the photosynthetic characteristics of intercropping leaves were decreased when the N application rate was 135 kg·hm-2,and the alleviation effect of shading stress was weakened.（3）The N accumulation in the aboveground parts of mung bean was significantly increased by 46.9%,66.3%and 12.5%under N1,N2 and N3 treatments compared to the control.The N use efficiency and N harvest index decreased by 1.0%–28.0%and 1.8%–27.0%respectively.Nitrogen application significantly increased the contents of N,available phosphorus,total potassium,and the activities of catalase and urease.N accumulation and yield were significantly positively correlated with ammonium,total potassium content,catalase,urease and sucrase activities in rhizosphere soil at the maturity stage.Suitable N application improved the soil microenvironment of mung bean under the intercropping system,promoted soil N transformation,enhanced the nutrient availability of mung bean rhizosphere soil,and alleviated the negative effect of intercropping on mung bean rhizosphere soil environment Therefore,the combination of reasonable intercropping and N application rate could be an important strategy to improve land-use efficiency and yield. |
PDF Full Text Request