Effects Of Different Winter Cover Crops On Soil Nutrients And Growth Characteristics Of Rainfed Maize

In recent years,a large area of farmlands were bare with the gradual reduction of winter wheat planting area in winter in the North China Plain,which not only caused heavy losses of light and heat,and a waste of land and other natural resources,but also made the further ecological environment deterioration.Therefore,to plant winter cover crops is expected to fill the bare farmland and reduce the environmental impact due to the lack of winter wheat that is an important part of agricultural sustainable development in the North China Plain,and also is key to improve soil fertilities,to optimize the ecology of environment,and to promote the energy saving and emission reduction.The pot experiment was used to investigate the effects of 3 kinds of winter cover crops including hairy vetch（Vr）,orychophragmus violaceus（Ov）and winter rape（Bc）on soil properties,microbial biomass and enzyme activities,and the growth of following crop（spring maize）.The effects of 5 cover types including straw cover（T1）,wheat cover（T2）,weed cover（T3）,February Orchid cover（T4）and winter rapeseed cover（T5）on soil physicochemical properties,microbial characteristics and soil inorganic nitrogen content of plough layer were also compared by the field investigation,sampling and lab analyses.The aim of the research is to provide theoretical and practical basis for the extension of winter cover crop planting in the north China plain.The results were as follow:1)The biomass of winter cover crops were as the order of Vr>Bc>Ov.Compared with CK,all 3 kinds of winter cover crops could increase soil moisture,available phosphorus,soil microbial biomass carbon,nitrogen and phosphorus content significantly（P<0.05）.Additionally,soil alkaline phosphatase,invertase and urease activities were also increased.Soil available phosphorus content under Ov treatment was promoted by 33.3%（P<0.05）.Soil moisture on Bc treatment was significantly increased by 16.9%,while soil bulk density was reduced by 16.8%（P<0.05）;in addition,microbial biomass carbon,microbial biomass nitrogen,microbial biomass phosphorus,soil alkaline phosphatase,invertase and urease activities were increased by 30.5%,32.3%,85.4%,11.4%,17.7%and 21.7%,respectively.Considering winter cover crop biomass,and its influence on soil properties,soil microbial biomass and enzyme activities comprehensively,winter rape is the best winter cover crop that followed by Orychophragmus violaceus and hairy vetch in the North China Plain.2)Incorporation of winter cover crop into soil could increase the following maize yields and nutrient uptake.Compared with the WFM,maize height,straw yield and grain yield of OvM were the highest,which increased by 10.6%,33.3%and 35.5%（P<0.05）respectively.The aboveground uptake of nitrogen,phosphorus and potassium,and the underground uptake of phosphorus in BcM were significantly increased by 30.7%,74.7%,57.6%and 171.4%（P<0.05）,respectively.The soil organic matter,alkaline nitrogen,available phosphorus,available potassium,total nitrogen and total potassium content were all significantly improved in 0-10cm and 10-20cm soil layers under all treatments of incorporation of cover crop into soil（P<0.05）.In 0-10cm soil layer,compared with WFM,soil pH and bulk density of BcM were decreased most as 21.3%and 0.35%respectively;soil organic matter,available phosphorus,available potassium,total nitrogen and total potassium in BcM were the highest with the increase of 5.6%,39.0%,8.5%,10.7%and 7.6%,respectively（P<0.05）.In 10-20cm soil layers,compared with WFM,soil organic matter,dissolved nitrogen and total nitrogen of BcM treatment（P<0.05）were significantly increased by 9.8%,8.9%,and 8.8%,respectively.While soil available phosphorus,available potassium and total potassium of OvM treatment were increased most by 62.9%,11.7%and 2.6%,respectively（P<0.05）.In addition,NH₄⁺-N and NO₃^--N contents in rhizospheric soil on seedling stage of young maize could be significantly reduced（P<0.05）.The soil microbial biomass C（SMBC）,soil microbial biomass N（SMBN）and soil microbial biomass P（SMBP）were all significantly higher than that of fallow in winter on different stage of maize（P<0.05）.Compared with the WFM treatment,SMBC,SMBN and SMBP of VrM,OvM and BcM at the seedling stage of maize were increasedby58.0%-73.8%,95.5%-117.0%and 202.6%-267.3%,respectively.Comprehensively considering the effects of the incorporation of winter cover crops into soil on soil properties and microbial biomass,winter canola-maize and orychophragmus violaceus-maize are better crop rotaions to be recommended on Fluvo-aquic soil in North China Plain.3)Compared with other mulching methods,T1 treatment was the best to improve soil water content.Compared with CK,T1 treatment increased the soil nutrient content to a certain extent,and helped increase SMBP,but had a little effect on SMBC.Compared with T4and T5,T1 increased the soil N leaching.Compared with other mulching methods,T2 was detrimental to the improvement of soil nutrients,and significantly increased soil NO₃^--N losses.T4 and T5 treatments were beneficial to increase available nutrients in the subsurface layer of soil,to increase SMBC and SMBN significantly,and to reduce the losses of soil inorganic nitrogen.Comprehensively considering the effects of different mulching ways on soil nutrient content,microbial properties and soil NO₃^--N and NH₄⁺-N,planting orychophragmus violaceus and winter canola in winter were better in the soil fertility improvement and the ecological environmental protection.Winter crops are recommended for orychophragmus violaceus and winter canola in suburban areas of Beijing.