Effects Of Nitrogen Supply Level On Plant Plasticity And Soil Physical And Chemical Properties In Soybean/Maize Intercropping Mode

Soybean/corn intercropping is a common intercropping mode.By rationally configuring the spatial distribution of crop groups,the utilization rate of light energy is improved,so that soybean/corn intercropping can improve the efficiency of nutrient utilization,so as to achieve the effect of increasing yield.However,there have been few reports on the plasticity of the root system caused by the root interaction between soybean/corn intercropping and the spatial heterogeneity of the root system to the soil profile of the intercropping system.In this experiment,four nitrogen supply levels were set:NO(no nitrogen fertilizer),N1(180 kg·hm-2),N2(240 kg·hm-2)and N3(300 kg·hm-2).Three cropping modes:corn monocropping(MM),soybean monocropping(MS),soybean and corn intercropping(corn intercropping-IM,soybean intercropping-IS),through two-year field trials to study soybean/corn intercropping under different nitrogen levels Model aboveground and root morphology plasticity,and spatial distribution characteristics of nutrients in soil profiles.In order to further reveal the mechanism of efficient utilization of crop nutrient resources under different nitrogen supply levels,intercropping provides a theoretical basis.The main results are as follows:(1)Different nitrogen supply levels have different effects on the plant type plasticity of corn/soybean intercropping.The intercropping mode increased the leaf area index(LAI)of the maize.At the NO level,the plant height of the intercropping maize increased significantly.There was no significant difference in the other nitrogen supply levels between the treatments.The intercropping mode increased the plant height of the intercropping soybean.At N1 and N3 levels,the intercropping mode increased the intercropping soybean LAI.(2)The application of nitrogen fertilizer increased the SPAD value of corn leaves,but had no significant effect on the SPAD value of soybean leaves.Intercropping significantly increased the SPAD value of corn leaves at NO,N1,N2,and N3 levels,resulting in an increase in corn net photosynthetic rate(Pn),stomatal conductance(Cond),intercellular carbon dioxide concentration(Ci),and transpiration rate(Tr),of which At the levels of NO,N1,and N3,Pn increased by 67.28%,39.92%,and 30.17%respectively compared to single-cropped corn;the intercropping mode increased the SPAD value of soybean leaves at the levels of NO,N1,and N2,by 3.83%,12.92%,and 4.02,respectively%.(3)Under NO and N2 nitrogen supply levels,the root length density reaches the maximum at 0-20cm,and the root length density of intercropping corn at soil depths of 0-60cm is higher than that of corresponding single crops,indicating that the intercropping mode can increase the soil depth by 0-60cm Medium corn root density,0-60cm soil depth with soybean intercropping area,corn root length density is significantly greater than the corresponding interrow area of single cropping,indicating that the corn root system expands to the adjacent soybean area after intercropping,increasing the lateral absorption area of the intercropping corn root system;In the NO level 0-80cm soil layer,the root density of single-cropping soybeans is significantly greater than that of intercropping soybeans,indicating that the intereropping with corn reduces the root density of soybeans.At the level of NO and N2,the single-cropping soybean inter-row area has a depth of 0-60cm The long density is greater than the intercropping area.The law of root dry weight of each soil layer is consistent with the law of root length density.Nitrogen application increased the rate of nitrogen uptake per unit root length of soybean and corn.The rate of nitrogen uptake per unit root length of soybean and corn in intercropping mode was lower than that of single cropping,indicating that intercropping led to changes in the root plasticity of corn and soybean.(4)At the NO level,the total nitrogen content of the M/S area in each level of soil is less than the MMG and MSG positions,while at the N2 level,the total nitrogen content of the M/S soil at all depths is not significantly different,indicating that the intercropping mode can be used in nutrients Promotes crops to absorb nitrogen in the M/S area when deficits occur;at a NO level of 0-80 cm soil depth,M/S soil alkaline nitrogen content is higher than other areas,N2 level 0-60 cm soil depth,M/S area alkaline hydrolysis The nitrogen content is higher than that of MMG and MSG.The root plasticity causes the soybean and corn roots to interact,thereby improving soil nutrients in the intercropping area and increasing the alkaline nitrogen content in the M/S area for crop absorption;the NO level M/S area soil quick-acting The content of phosphorus and available potassium is significantly higher than that of N0MMG,the available phosphorus content of N2 level 0-20cm soil depth M/S is significantly higher than that of N2MMG,the N2 level 0-60cm soil depth M/S position,the soil available potassium content is significantly higher than N2MMG Location,the difference in root distribution of soybean and maize in the NO level M/S area affects the nutrient content of the intercropping area,and the soil available phosphorus and available potassium content in the intercropping area increase.At the N2 level,the available phosphorus content in the 0-20 cm soil and the available potassium content in the 0-60 cm soil increased in the intercropping area.The soil available phosphorus content in the M/S area of NO and N2 levels was significantly higher than that of N0MSG and N2MSG,indicating that the soil available phosphorus content in the intercropping area had a greater relationship with the distribution of crop roots.The root length density of maize and soybean in the NO and N2 horizontal intercropping area was positively and significantly related to the content of soil alkaline nitrogen.(5)The water content of the 0-0cm soil intercropping area at the NO level during the corn tasseling period is less than the N0MMT,N0MMG position,greater than the N0MST,N0MSG position,and the soil water content of the M/S area at the N2 level is significantly less than the N2MMG,N2MMT position,N2MSG and N2MST position The soil water content of each treatment in the corn filling stage is basically consistent with the tasseling period.