Experimental Study On Garlic Irrigated By Reclaimed Water In Lake Erhai Basin

Water is the source of life and the material basis for human survival and development.Reclaimed water is a unique and precious water resource.It not only has the characteristics of water,but it is also a rare source of fertilizer because it contains nitrogen,phosphorus and potassium fertilizers.It is of great significance to promote the sustainable development of water resources and agriculture,as well as environmental protection,to strengthen the use of reclaimed water for agriculture.Making rational use of the water and fertilizer resources of reclaimed water and reducing the pollution discharged into the environment while promoting agricultural production is helpful to protect the environment.The loss of nitrogen,phosphorus and other pollutants which is caused by unreasonable irrigation and fertilization,untreatment of livestock and poultry breeding wastewater,farmland drainage,domestic sewage and so on is making Erhai Lake face serious eutrophication problems.In order to achieve efficient recycling of water and fertilizers and reduce the harm caused by agricultural non-point source pollution to Erhai,this paper took garlic which is the main crop in the basin as the research object,studied the research and application of key technologies for the utilization of reclaimed water represented by aquaculture wastewater.It also analyzed the effects of reclaimed water irrigation on garlic growth indexes and yield,nitrogen utilization and nitrogen balance and put forward the irrigation technology and fertilizing suggestion of garlic irrigated by reclaimed water in the Lake Erhai Basin.The main conclusions were as follows:(1)Irrigated by reclaimed water can effectively increase the plant height and leaf area index of garlic;the effect on the dry weight of individual plants and pseudo-stem diameter is weaker than the previous two indicators,but it is still positive;there is no significant effect on the number of leaves.(2)Irrigated by reclaimed water can increase the yield of garlic,and the rate of increase in production depends on the amount of total nitrogen brought by reclaimed water.The growth and development indicators and yields of garlic irrigated with reclaimed water and supplemented with basal fertilizer were all optimal.Reclaimed water irrigation is beneficial to promote the absorption and utilization of nitrogen by garlic plants and improve the nitrogen fertilizer efficiency of garlic.However,the total nitrogen absorbed by plants does not contribute to the formation of bulb yield.(3)Relative to farmers' habitual fertilization mode,reclaimed water irrigation will not increase the soil inorganic nitrogen content in garlic,and will not increase the risk of nitrogen loss in farmland.Reclaimed water irrigation can make maximum use of the total nitrogen input into the garlic field and convert it into plant nitrogen,but long-term irrigation with reclaimed water may cause a risk of nitrogen deficiency in the crop-soil system.Therefore,it is recommended that a certain amount of fertilizer be applied under the conditions of reclaimed water irrigation.(4)Under the condition of reclaimed water irrigation,the water requirement of garlic was similar to that under the condition of fresh water irrigation.The water requirement at the seedling stage was the largest,followed by the garlic sprout elongation period and the bulb expansion period.Under the test conditions,the daily water consumption intensities of seedling stage,seedling stage,bud differentiation stage,garlic sprout elongation stage,and bulb expansion stage were 2.2 mm/d,3 mm/d,5.4 mm/d,and 5.0 mm/d,5.6 mm/d,respectively.(5)The crop coefficients of different stages of garlic growth in the Lake Erhai Basin(emergence stage,seedling stage,bud differentiation stage,garlic sprout elongation stage,and bulb expansion stage)are 0.96,1.66,2.01,1.62,and 1.62,respectively.(6)The irrigation system of garlic reclaimed water in the Lake Erhai Basin over a multi-year average:when the depth of groundwater is greater than 25cm,irrigation is performed twice at the seedling stage,and the irrigation volume is 41.4mm and 45mm,respectively,and the garlic sprouts extend or the bulb expansion stage is irrigated once,and the irrigation volume is 70mm.The number of times of reclaimed water irrigation can be appropriately increased to reduce the amount of secondary irrigation so as to reduce the risk of nitrogen fertilizer loss and environmental pollution caused by drainage.(7)Fertilizing measures for irrigation of reclaimed water with garlic:A certain amount of basal fertilizer is supplemented.The amount of nitrogen applied to the basal fertilizer in this paper is 150 kg/hm2.Supplementing chemical fertilizers can significantly increase garlic production.It can also reduce the risk of garlic production loss due to insufficient amount of fertilizer in the reclaimed water irrigation zone,and at the same time improve nitrogen deficiency caused by irrigation water.