Study On Yield Formation And Water Use In Winter Wheat Cultivar Intercropping And Mixture Cropping Under Limited Irrigation

It is very important for the sustainable development of wheat in North China to improve yield and water use efficiency under limited irrigation.We hypothesized that the optimization and regulation of population structure by the intercropping,and mixture cropping with different cultivars,making full use of biodiversity,is very helpful to further increase yield and water use efficiency in wheat under water-saving cultivation.To test these hypotheses,three-year field experiments(including two cultivars intercropping,and two cultivars mixture cropping experiment)was conducted under limited irrigation(no irrigation during the whole growth stage,75 mm applied at stem elongation),with different plant height cultivars(B13 with approximately 110 cm plant height,Weimai8 with approximately 85 cm plant height,Jimai22 and Shimail5 with approximately 75 cm plant height,and Nongda399 approximately 68 cm plant height).A meta-analysis was carried out to evaluate dry matter production,yield,water consumption characteristics,and water use efficiency in the intercropping,and mixture cropping as compared to pure stands,by using data obtained from three-year field experiments(88 paired observations from 14 planting patterns in intercropping experiment,104 paired observations from 16 planting patterns in mixture cropping experiment).Three-year main results were as follows.1.Cultivar intercropping experimentA concave-convex canopy structure was produced under fourteen two-cultivar intercropping with different plant height cultivars and various inter-ratios.A significant difference was detected in yield and water use efficiency among different treatments.The synergistic increase in grain number per ear and population photosynthetic potential,resulted in the enhancement of source and sink,and a consequent increase yield and water use efficiency,by choosing suitable cultivar combination with inter-ratio of 3 rows:3 rows.(1)There were two intercropping patterns increased yield,two intercropping patterns increased water use efficiency,and two intercropping patterns increased both yield and water use efficiency,compared to mean value of pure stands,among fourteen planting patterns under no irrigation during the whole growth stage.The most significant increase in yield and water use efficiency occcurred in Weimai8 and Jimai22 intercropping treatment with inter-ratio of 3 rows:3 rows;its grain number per ear and yield were increased by 17.7-22.6%and 3.7-8.8%as compared to mean value of pure stands;it enhanced leaf area index at anthesis,delayed the decrease in leaf area index after anthesis,evidently raised population photosynthetic potential,and increased dry matter after anthesis by 6.0-17.6%;its water consumption was 4.2-8.2%less than mean value of pure stands,whereas its water use efficiency was increased by 2.4-16.3%as compared to mean value of pure stands.(2)The increase in yield,and water use efficiency was found in one,and two planting patterns as compared to mean value of pure stands,among fourteen planting patterns,when 75 mm irrigation water applied at stem elongation.The Weimai8 and Jimai22 intercropping with inter-ratio of 3 rows:3 rows evidently raised net assimilation rate before anthesis,increased dry matter after anthesis by 17.5-27.8%,enhanced dry matter at maturity by 2.1-4.7%,raised yield by 3.6-6.9%as compared to mean value of pure stands.(3)The intercropping with high plant height cultivar and low plant height cultivar decreased rust incidence,and lengthened leaf area duration after anthesis,under the two irrigated patterns.2.Cultivar mixture cropping experimentA heterogeneous canopy structure was created under sixteen two-cultivar mixtures with different plant height cultivar and various mixture ratios.There were significant differences in yield and water use efficacy among different treatments.The enhancement of source and sink by the synergistic increase in grain number per ear and population photosynthetic potential,simultaneously increased yield and water use efficiency,through choosing reasonable cultivar combination with mixture ratio of 1:2.(1)The yield improvement occurred under twelve planting patterns,the increase in water use efficiency was found in five planting patterns,and no yield advantage was detected in four planting pattern,and three planting patterns simultaneously increased yield and water use efficiency as compared to mean value of pure stands,among sixteen planting patterns under no irrigation during the whole growth stage.The B13 and Nongda399 mixture cropping with mixture ratio of 1:2 increased leaf area index at anthesis,dry matter after anthesis,and yield by 10.4-18.0%,15.1-27.6%,6.3-12.5%,respectively,compared to mean value of pure stands;the Weimai8 and Jimai22 mixture cropping with mixture ratio of 1:2 enhanced leaf area index at anthesis,delayed the drop of leaf area index after anthesis,and significantly raised population photosynthetic potential during grain-filling stage,and resulted in the significant improvement of yield and water use efficiency.(2)The four planting patterns increased yield,two ones enhanced water use efficiency,and two ones simultaneously raised yield and water use efficiency as compared to mean value of pure stands,among sixteen planting patterns under 75 mm irrigation water applied at stem elongation.The Weimai8 and Nongda399 mixture cropping with mixture ratio of 1:2 enhanced leaf area index by 6.3-16.3%at antheis,increased population photosynthetic potential by 6.2-7.8%during grain-filling stage,raised grain number per ear,yield and water use efficiency by 6.0-11.2%,9.2-15.8%,and 8.9-16.1%,respectively,compared to mean value of pure stands.(3)The mixture cropping with high plant height cultivar and low plant height cultivar decreased rust incidence,and lengthened leaf area duration after anthesis,under the two irrigated patterns.In sum,intercropping and mixture cropping with high plant height cultivar and low plant height,changed from homogeneous crop population structure of conventional pure stands,to a heterogeneous canopy structure with inhomogeneous spatial distribution of plant height,leaf and ear,resulted in the alteration in the internal environment of crop population,and the optimization of resources interception and utilization.Selecting suitable cultivars,inter-ratio or mixture ratio to intercropping or mixture cropping,improved canopy photosynthesis,increased grain number,resulting in the synergy increase in the source and sink,and a consequent improvement of the yield and water use efficiency under limited irrigation.It is necessary to further study the coordination mechanism and biological interaction characteristics of root-crown in cultivar intercropping or mixture cropping.