晋西南褐土上小麦苜蓿套作对土壤氮素及植物吸氮的影响

Effects of alfalfa-wheat intercropping systems on soil nitrogen and plant nitrogen uptake in cinnamon soil of Southwest Shanxi province

研究冬小麦和苜蓿不同种植模式在不同生长期内土壤氮素的变化特征,以期为粮草混播种植模式提供参考依据。依托2014年在晋西南开展的田间试验,于2017和2018年研究了小麦单播、苜蓿单播和小麦苜蓿混播的作物产量以及土壤剖面氮素特征。结果表明:(1)两个试验年份内小麦苜蓿混播增加了作物生物量且小麦植株茎叶和籽粒氮含量均高于小麦单播;相比任一单作,小麦苜蓿混播显著提高了作物植株氮积累总量。(2)种植方式影响表层(0~30 cm)土壤硝态氮含量,3月春季返青时苜蓿单播高于小麦单播和混播处理,6月麦收时小麦单播和混播均高于苜蓿单播;苜蓿单独生长期(10月)200 cm深土壤剖面硝态氮含量依次为小麦单播>混播>苜蓿单播。不同生长时期小麦单播硝态氮随土壤剖面垂直淋失并于土壤深层大量累积,而小麦苜蓿混播后缓解了硝态氮的垂直淋失现象。(3)小麦返青时0~30 cm土层苜蓿单播土壤铵态氮含量略高于小麦单播和混播,小麦地休耕苜蓿单独生长期200 cm深小麦单播铵态氮含量低于苜蓿单播和混播。(4)越冬期(前一年10月~3月)小麦苜蓿混播土壤无机氮得到了累积,小麦苜蓿共生期(3~6月)土壤无机氮处于消耗阶段,麦收后苜蓿单独生长期(6~10月)无机氮又得到了补充。

The variation characteristics of soil nitrogen in different planting patterns of winter wheat and alfalfa were studied in order to provide reference for different planting patterns of grain and grass.Based on field experiments started in Southwest Shanxi in 2014,crop yield and soil profile nitrogen characteristic of wheat,alfalfa monoculture and wheatalfalfa intercropping were studied in 2017 and 2018.The results showed that:(1)In the two experimental years,the biomass of wheat-alfalfa intercropping increased,and the nitrogen contents of stem,leaf and grain of wheat were higher than those of wheat monoculture.Compared with any monoculture system,the nitrogen accumulation of wheat-alfalfa intercropping system was increased significantly.(2)Nitrogen content in surface soil(0~30 cm)was affected by planting pattern.In spring,the nitrogen content in alfalfa monoculture was higher than those of wheat monoculture and wheat-alfalfa intercropping;At wheat harvest,the nitrogen contents in wheat monoculture and wheat-alfalfa intercropping was higher than that of alfalfa monoculture.Nitrate nitrogen content in soil profile of 200 cm depth during the growth period of fallow alfalfa in wheat field was as follows:wheat monoculture>wheat-alfalfa intercropping>alfalfa monoculture.At different growth stages,nitrate nitrogen in wheat monoculture was leached vertically in soil profile and accumulated in deep soil,however,wheat-alfalfa intercropping alleviated the vertical leaching of nitrate nitrogen.(3)Ammonium nitrogen of alfalfa monoculture in 0~30 cm soil layer was slightly higher than that of wheat monoculture and wheatalfalfa intercropping in the next spring.The content of ammonium nitrogen in wheat monoculture system in different sections of fallow alfalfa growing period at 200 cm soil depth was lower than that of alfalfa monoculture and wheatalfalfa intercropping.(4)The soil inorganic nitrogen of wheat-alfalfa intercropping accumulated in the winter period(October of the previous year-March of the next year).During the symbiosis period of wheat and alfalfa(March-June),soil inorganic nitrogen was in the consumption stage;After wheat harvest(June-October),the inorganic nitrogen of single alfalfa was supplemented.In conclusion,compared with any monoculture,wheat-alfalfa intercropping system improved the soil and crop nitrogen levels,and reflected the advantages of wheat-alfalfa intercropping system.