Yield And Water Use Efficiency In The Wheat/Maize Intercropping System Under Different Nitrogen

Intercropping is an effective technique to enhance productivity under arable land reduction and water shortage and land degradation conditions.The existing research mainly focused on intercropping under sufficient or supplementary irrigation,however less study has been conducted for rain-fed condition.Additionally,the impact of different nitrogen application rates on the yield and water use efficiency of intercropping system under rain-fed conditions are unknown.In this study,a two-year field experiment was conducted to check the effectiveness of wheat/maize intercropping system under rainfed condition,and to explore the growth,photosynthetic activities,soil water contect,yield and yield components of wheat/maize intercropping under three nitrogen application rates(N0,N1,and N2represent 0,120,and 240 kg N ha^-1for wheat and 0,180,and 360 kg N ha^-1for maize,respectively).The purpose of this study was to explore the yield and water use efficiency of wheat/maize intercropping system under different nitrogen application,and to provide a theoretical basis for the development of wheat/maize intercropping in rain-fed areas.The conclusions are as follows.（1）Our results showed that,in intercropped wheat,the leaf area index（LAI）,aboveground dry matter accumulation,net photosynthetic rate（Pn）and relative chlorophyll content（SPAD）were recorded for border rows which were significantly higher than those of inner rows and sole wheat,except for plant height.In intercropped maize,the growth varied greatly in different periods,The results showed that the LAI,dry matter accumulation,Pn and SPAD of border rows were decreased significantly than those of sole maize and inner rows after 60 days of maize sowing.However,after co-growth stages,the dry matter accumulation of intercropped maize was higher than that of sole maize at the level of N2.Also,intercropping reduced the Pn and SPAD of maize,and the difference lasted for a while,after wheat harvesting,the growth of border rows significantly recovered after 75 days or 90days of maize sowing.However,the border rows always showed a growth disadvantage until maturity,and the dry matter accumulation of intercropped maize was higher than that of sole maize at N2 level.The aggressivity to measure the intercropping competition of wheat with maize at co-growth stages showed(A_WM)>0,and the competitiveness of wheat in intercropping system was stronger than that of maize,and nitrogen application could alleviate the competitiveness between them.（2）During the both years of experiment,the wheat/maize intercropping system from wheat sowing to maize harvest showedΔWU<0 andΔWUE>0 under three nitrogen levels,which indicated that the water consumption of wheat/maize intercropping system was less than that of sole crops with same yield,andΔWU was ranged from-4.95%to-0.04%.The maximum reduction in water consumption was observed for N1 rate,and the average water consumption of the intercropping system was 47.30 mm less than that of the sole crops during both years of experiment.TheΔWUE was ranged from 2.77%to 6.46%,the wheat/maize intercropping system had the advantages of water saving and water use under three nitrogen application levels.（3）The yield of intercropped wheat was significantly increased by 21.3%-27.8%than that of sole wheat during both years,and the yield advantage of intercropped wheat mainly came from the yield increase of border-1-row and border-2-row.The yield advantage of border-1-row came from the common increase of all yield components,while the yield advantage of border-2-row came from the increase of effective panicles and grains per panicle.However,the yield disadvantage of intercropped maize was mainly through the decrease of grain number per ear and 100 grain weight.Compared with sole maize,the grain yield of inner maize was increased by 6.27%-12.68%.The total yield of intercropped maize was affected by nitrogen rates,where maximum reduction（3.0%-11.4%）for N0 and N1levels during both years,only higher than that of sole maize under N2 level.Nitrogen application increased the yield and yield components of wheat and maize.In the two-year experiment period,the LER of wheat/maize intercropping was between 1.04-1.16,which had the advantage of land use.The wheat/maize intercropping system has the advantages of land use and water saving,and the yield and land use advantages of the intercropping system gradually increase with the increase of nitrogen application level.These results suggest that wheat/maize intercropping systems are feasible to develop under rain fed condition in semi humid area.