Effect Of Alternative Irrigation On Yield And Water Use Efficiency Of Wheat Corn Intercropping Systems In Oasis Area

In oasis irrigation area of Hexi Corridor,the development of strip intercropping is facing the serious obstacle of using too much water resources but along with low crop water utilization efficiency(WUE),which is mainly caused by the undeveloped irrigation technology.In this study,a field experiment was carried out in order to integrate ridge planting and alternative furrow irrigation technologies into wheat corn intercropping production system,and to investigate the differences of the yield,WUE,production value, and production value per cubic water between flood irrigated intercropping systems and alternative irrigated intercropping systems.The main result are:1.Intercropping can increase the land utilization efficiency,WUE,the value of production and the production value per cubic water,the alternative irrigation is prior to flood irrigation in enhancing yield,WUE and production value per cubic water of intercropping system.At the irrigation rates of 2550m³/hm²(low),3000m³/hm²(medium) and 3450m³/hm²(high),the Land Equivalent Ratio(LER) of intercropping systems is varied from 1.218 to 1.522,and the LER of alternative irrigated intercropping system is 12.31%,17.98%,12.81%higher than that of the flood irrigated ones at the irrigation rate of low,medium and high respectively.Compared with the average WUE of mono-cropping wheat and corn at the irrigation rate of low,medium,high,the WUE of flood irrigated and alternative irrigated wheat corn intercropping system is increased by 19.93%and 43.64%, 9.18%and 40.62%,17.58%and 47.74%respectively,and the WUE of alternative irrigated intercropping system is 12.32%,17.29%,12.25%higher than that of the flood irrigated intercropping system at the three irrigation rate respectively.With a production value equivalent ratio of 1.218～1.513 and production value equivalent ratio per cubic water of 1.241～1.592,the intercropping showed obvious priority in improving the economic production of land and water resources.In general,the scheme of alternative irrigation with amount of 3000m³/hm² can be regarded as a reference irrigation scheme for wheat corn intercropping system in oasis irrigation area.2.Along with the increase of irrigation amount,the total water consumption of crop is increasing,and total water consumption of intercropping system is nearly equal to the average of the corresponding mono-cropping wheat's and corn's at same irrigation rate. Compared to sole wheat and corn,the average Leaf Area Index(LAI) and the LAI Accumulation over Time(LAID) of intercropping system and the effective rainfall in the whole growth period were improved,and this is main causes of higher yield of intercropping.In treatments with high rate irrigation amount,the total water consumption of wheat,corn,flood irrigated intercropping,alternative irrigated intercropping systems are 16.11%and 5.07%,15.63%and 10.84%,16.23%and 8.79%,16.55%and 8.81%higher than that of the four cropping systems with low and medium rates irrigation amount respectively.Compared with the average water consumption amount of sole wheat and sole corn at same irrigation rate,the total water consumption of flood irrigated intercropping system is increased by 0.1%,-0.1%,0.5%at low,medium,high irrigation rate respectively, and in alternative irrigated intercropping that is increased by 0.3%,0.3%,0.9% respectively.The average LAI of flood irrigated and alternative irrigated intercropping systems in the whole growth period is increased by 13.35%and 14.46%compared with sole wheat,by 6.22%and 7.26%compared with sole corn,and the LAID of the two intercropping systems is increased by 104.03%and 106.02%,6.22%and 7.26%compared with sole wheat,sole corn.In the whole growth period,the effective rainfall of intercropping is 87.1%higher than that of the sole wheat.3.There is a obviously compensate effect of biomass accumulation in intercropping corn in the later part of the growth period,and alternative irrigation can promote the compensate effect compared with flood irrigation;intercropping is beneficial to accumulate photosynthetic product in leaf of wheat in the former growth period and to promote the photosynthetic product transferred from other organs into ear in the later growth period,and alternative irrigation has advantage in transferring biomass into ear of wheat compared with the flood irrigated intercropping wheat;intercropping can prolong the effective photosynthetic period of corn and promote the photosynthetic product in sheath and stem transferred into economic product.It shows that,the biomass accumulation rates of intercropping corns are significantly higher than that of the sole ones 20 days after wheat harvest,and in the latest three measure periods the population growth rate of alternative irrigated intercropping corn is 25.71%,20.55%,77.93%higher than that of the flood irrigated ones respectively.In the two measuring periods of 10^th April to 20^th May and 20^th May to 10^th June,the leaf growth rate of alternatively irrigated intercropping wheat is increased by 87.62%and 121.67%compared with that of the sole wheat,in flood irrigated intercropping system it is increased by 61.51%and 38.09%respectively;after 30^th June,the output rates of sheath and leaf are increased by 25.68%and 11.35%in flood irrigated intercropping wheat,and 24.04%and 24.01%in alternatively irrigated intercropping wheat compared with sole treatment,but the growth rates of wheat ear in flood irrigated system and alternatively irrigated system is improved by 51.77%and 60.22%respectively.Before harvesting wheat,the growth rate of leaf,sheath and stem of intercropping corn is improved by 4.76%～61.4%,24.32%～71.63%and 23.04%～68.2% compared with that of the sole corn,and in this period the growth rate of flood irrigated intercropping corn is higher than that of the alternatively irrigated corn;after 30^th August, the output of sheath and stem of intercropping con in flood irrigated treatment is improved by 90.57%and 82.78%compared with that of the sole corn,in alternatively irrigated intercropping it is improved by 69.47%and 71.48%,the ear growth rates of flood irrigated and alternatively irrigated intercropping corn is 83.35%and 72.35%higher than that of the sole cropping corn.4.In sole cropping wheat,the marginal effect is positive,but in intercropping,the marginal effect of wheat is negative,and the negative marginal effect of intercropping wheat in alternative irrigation system is more serious than that in flood irrigation system; compared with the sole cropping wheat,the yield of intercropping wheat is significantly improved in different cropping rows.The effect of irrigation amount on the average competition of intercropping wheat and corn in the whole co-growth stage is weak,but high rate irrigation amount can significantly improve the competitive ability of intercropping corn in the late co-growth stage of wheat and corn,and in the last 20 days of co-growth,the competitive ability of wheat is weaker than that of corn.