Effects Of Water And Nitrogen Supply And Its Impacts On Grwth Of Watermelon Under Alternate Partial Rootzone Drip Irrigation With Different Nitrogen Substitute Ratio Of Organic Fertilizer To Chemical Fertilizer

Alternate partialrootzone drip irrigation is an efficient water-saving and fertilizer-saving irrigation mode.The role of organic fertilizers in replacing fertilizers to improve soil fertility and increase yield has been paid more and more attention.In order to explore aeffective coupling of water and nitrogen in the alternate partial rootzone drip irrigation under different replacement of organic fertilizer nitrogen with high yield and quality of facility crops,this experiment carried out detecting the effects of irrigation methods on the growth of watermelon under different organic fertilizer nitrogen substitutions in plastic greenhouses.The experiment set three organic fertilizer level(0% organic fertilizer nitrogen,40% organic fertilizer nitrogen and 70% organic fertilizer nitrogen)and two irrigation methods(alternate irrigation and conventional irrigation)were used to determine the effects these treatments on the soil physicochemical factors,enzyme activities,plant biomass,chlorophyll content,fruit yield and water use efficiency,and fruit quality.In order to explore the difference between drip irrigation on both sides of the root system and the effect of irrigation water amount on the soil properities and watermelon growth,different water volume(1/2 W,W and 2W)were set under the conventional drip irrigation condition with40% organic fertilizer nitrogen application.(1)Under conventional drip irrigation conditions,the water amount of irrigation had no effect on soil enzyme activity and watermelon yield compared with C40 1/2W and C40 W irrigation,but improved the quality of watermelon,i.e.vitamin C content,soluble solids,the sugar/acid ratio was 7.62%,5.49%,and 5.74% higher than that ofC40 W,respectively.Under double water amount treatment,the soil enzyme activity,yield,vitamin C content,chlorophyll content of watermelon significantlyincreased;however,the water use efficiency significantly decreased with the increase of irrigation amount.(2)There is no significant difference between total nitrogen,total phosphorus and total potassium in alternate drip irrigation and conventional drip irrigation under the same irrigation water amount and organic fertilizer.With 100%inorganic fertilizer appilcation,the alternate irrigation significantly increases the soil available nutrient.Under the replacement ratio of 40% organic fertilizer,the irrigation method had no significant effect on the alkaline nitrogen and available potassium.The available phosphorus content in the soil showed that the alternate drip irrigation was 8.76%higher than the conventional drip irrigation,while the organic matter and active organic matter content were lower than the conventional irrigation.Under the replacement ratio of 70% organic fertilizer,the irrigation method had no significant difference to available phosphorus and available potassium.The content of alkali nitrogen in conventional drip irrigation soil was higher than that of alternate drip irrigation.With the increase of organic manure,alternate drip irrigation increased soil enzyme activity,watermelon biomass and yield,chlorophyll content and water use efficiency.The vitamin C,soluble solids and sugar to acid in watermelon was higher than that of conventional drip irrigation.50.3%,5.95%,5.58% in alternate drip irrigation treatments.(3)Under the same irrigation water amount,following the replacement ratio of organic fertilizer increasing,the alternate drip irrigation has no significant effect on soil total nitrogen and total phosphorus.The organic fertilizer input increased the content of soil available phosphorus and active organic matter,but not influence the organic matter.Under conventional drip irrigation conditions,the ratio of organic fertilizer added significantly affected the available nutrientts and total phosphorus in the soil,but did not affect the total nitrogen and total potassium in the soil.The organic matter and active organic matter in the soil were consistent with alternate drip irrigation.Under the replacement of organic fertilizer nitrogen,alternate dripirrigation promoted the growth of watermelon,increased soil enzyme activity,and increased with the organic fertilizer replacement ratio increasing.Following the increase of organic fertilizer nitrogen substitution ratio,the stem weight increased with organic fertilizer nitrogen amendment.The aboveground part also increased with the increase of organic fertilizer nitrogen substitution ratio,yet,without affecting the weight of plant leaves.Fruit yield and water use efficiency were highest in 70%organic fertilizer nitrogen addition treatment.The content of vitamin C and soluble solids,and sugar/acid ratio increase with the increase of organic fertilizer nitrogen substitution rate,but there was no effect on organic acid.Organic fertilizer replacement ratio significantly affects chlorophyll content.Under alternate irrigation conditions,the chlorophyll was the highest in 70% organic fertilizer nitrogen addition treatment;The results of conventional drip irrigation were consistent with the results of alternate drip irrigation.In summary,water affects soil properities and watermelon growth.Under water-limited conditions,alternate drip irrigation can better improve soil properities,and promote plant growth,yield and quality,compared with conventional drip irrigation.The increase of organic fertilizer nitrogen substitution ratio is of great significance for improving soil characters and promoting watermelon growth.70%organic fertilizer nitrogen substitution ratio is most suitable to watermelon.