| At present,China’s agriculture is facing problems such as the gradual reduction of cultivated land resources and the decline of soil quality caused by excessive fertilization.Therefore,it is necessary to explore clean and efficient production technology models to improve soil quality and increase crop yield per unit area.Planting leguminous green manure is an important technical approach to improve soil nutrient use efficiency and crop yield in traditional agriculture in China,which has been re-emphasized in recent years.It is very important to establish a green and sustainable crop production technology model of grass-legume intercropping in the areas with wheat-maize double cropping system in China.Based on this,a field experiment was carried out in Yangling,Shaanxi Province from 2020to 2022,and four planting treatments were set up:summer maize monoculture（CK）,summer maize intercropping with small crown flower（MC）,intercropping with hairy vetch（MH）and intercropping with small black bean（MS）.Under the same planting density of summer maize,the effects of intercropping with different leguminous green manures on soil moisture and available nutrients,as well as the regulatory effects on root traits,aboveground growth,photosynthetic characteristics,yield and aboveground nutrient accumulation and distribution of maize were investigated.The main results are as follows:（1）Compared with monoculture,intercropping treatments increased the water consumption of 0-60 cm soil layer during maize growth period,and the soil water content decreased by 1.84%-2.82%in two years,with the largest water consumption in MS treatment.However,due to the shading effect of green manure in the late growth stage,the water content of 0-10 cm soil layer will increase.Due to the nitrogen fixation ability of leguminous green manure roots,it can increase the soil available nitrogen content.The nitrate nitrogen content of 0-60 cm in MC,MH and MS treatments increased by 9.80%,18.36%,8.94%and 10.55%,18.00%,9.20%in 2021 and 2022,respectively,compared with CK treatment,and the MH treatment increased most significantly in both years.The roots of leguminous green manure activated the insoluble phosphorus in the soil and promoted the release of available phosphorus.The content of available phosphorus in the0-60 cm soil layer of the intercropping green manure treatment was 16.54%-37.46%higher than that of the monoculture in two years.（2）Intercropping leguminous green manure affected the growth of maize aboveground and underground.The two-year data showed that MC and MH treatments significantly promoted the growth of maize shoots.At the silking stage,the plant height increased by 3.11%-4.08%（P<0.05）,the stem diameter and leaf area index increased by 8.45%-15.08%（P<0.05）and 3.51%-5.23%（P<0.05）,respectively.There was no significant difference between MS treatment and CK treatment.The intercropping of leguminous green manure significantly promoted the growth of maize roots.The root dry weight,root length density,root surface area density and root volume of maize treated with MC,MH and MS were higher than those of CK treatment.In the 0-60 cm soil layer,the root dry weight of the monoculture treatment increased by 9.31%-22.29%,the root length density increased by 8.65%-20.50%,the root surface area density increased by 10.65%-21.82%,and the root volume increased by 7.25%-14.46%compared with the monoculture treatment.（3）Intercropping different leguminous green manures had different regulatory effects on photosynthetic performance and canopy light transmittance of maize.The results of two-year experiment showed that the net photosynthetic rate（Pn）,stomatal conductance（Cond）and transpiration rate（Tr）of single leaf of maize under MC and MH treatments were higher than those of monoculture treatment,and the increase of MH treatment was the most significant.The average Pn,Cond and Tr of two years at the silking stage of maize increased by 17.37%,16.13%and 15.85%,respectively（P<0.05）.The Pn of MC treatment increased by 6.65%and 10.57%（P<0.05）compared with CK at silking stage and filling stage,respectively.There was no significant difference between MS treatment and CK,and the Pn of each treatment reached the maximum at filling stage.The results of two years showed that intercropping leguminous green manure reduced the light transmittance of the middle and lower canopy of maize compared with CK.The light transmittance of the middle canopy of MH treatment was the lowest,while the light transmittance of the lower canopy of MS treatment was the lowest.At the maturity stage of maize,the dry matter accumulation of MC and MH treatments increased by 1.81%-3.64%（P<0.05）on average compared with CK treatment in two years,and there was no significant difference between MS treatment and CK treatment.（4）In the intercropping system of three different leguminous green manures,intercropping with MC and MH increased maize yield by increasing the number of grains per ear and 100-grain weight（P<0.05）.Compared with CK treatment,MH treatment increased maize yield by 9.65%and 7.71%in two years（P<0.05）.The average yield of MC treatment was 4.97%higher than that of CK treatment,and there was no significant difference between MS treatment and CK.（5）The intercropping of three leguminous green manures will increase the nutrient accumulation in the aboveground part of maize and promote the accumulation of nitrogen and phosphorus nutrients in the aboveground part of the intercropping system.The average accumulation of nitrogen and phosphorus in the two years was 5.26%-12.42%and14.02%-27.29%higher than that of monoculture maize,respectively.Intercropping treatments optimized the distribution ratio of nitrogen and phosphorus nutrients in maize plants,and promoted more nitrogen and phosphorus nutrients in maize leaves and stems to be transported to grains.The proportion of nitrogen in maize grains under intercropping treatment increased by 2.27%-4.71%compared with CK treatment,and the proportion of phosphorus increased by 2.18%-5.35%.From the perspective of the overall intercropping system,due to the addition of leguminous green manure,the nitrogen and phosphorus accumulation of aboveground plants（maize and leguminous green manure）treated with MC,MH and MS increased significantly by 62.51-168.58 kg hm-2and 16.09-24.09 kg hm-2compared with monoculture maize treatment.In summary,in the intercropping mode of maize and leguminous green manure,intercropping hairy vetch,small crown flower and small black bean can increase soil available nutrient content and optimize maize root distribution,improve nutrient absorption efficiency;the treatment of intercropping hairy vetch and small crown flower can regulate the photosynthetic production capacity and growth and development of maize,promote dry matter accumulation and increase maize yield.Intercropping treatment can optimize the distribution ratio of plant nutrients,promote the accumulation of nitrogen and phosphorus nutrients in the aboveground intercropping system,and improve the utilization efficiency of farmland soil nutrients.It provides a certain research basis for exploring new ways to achieve green yield increase in wheat-maize double cropping area.. |
PDF Full Text Request