Effects Of Drip Irrigation Frequency And Nitrogen Application On The Growth And Development Of Squash

?Object?In high latitudes and cold regions,squash were used as test material in the energy-saving sol-ar greenhouse.This experiment was conducted by setting different irrigation frequency and nitrog-en application rates.The effects of different treatments on growth and development were investig-ated during the period of squash growth.The purpose is to determine the amount of scientific irri-gation and fertilizer indicators,select the appropriate irrigation system and optimize the amount of nitrogen applied.These provides a theoretical basis for high quality and high yield cultivation in water and nitrogen management.?Methods?Squash varieties"green superior"for the test material.In 2016 and 2017,the irrigation quota was 269.87mm in the cultivation of summer cucurbit in solar greenhouses.Two drip irrigation frequencies?low frequency W1:7 days,high frequency W2:2 days 1?and 2 nitrogen levels(nitrogen N1:375 kg·hm^-2,high nitrogen N2:565 kg·hm^-2).Sampling and determination of plant height,stem diameter,leaf number,leaf area,dry fresh weight of shoots,total nitrogen accumulation in aboveground parts,dry matter accumulation above ground and total nitrogen accumulation,leaf nitrogen metabolism key enzyme activity of squash,Photosynthetic characteristics and fluorescence parameters,yield,while taking soil to determine 0-20cm,20-40cm,40-60cm,60-80cm soil moisture content,nitrate nitrogen content,ammonium nitrogen content,water use efficiency and water consumption.Variance analysis was used to analyze the test data.?Results?1 When the level of nitrogen supply is fixed under fixed irrigation quantity,the increase of irrigation frequency can promote the plant height,stem diameter,leaf number and leaf area of the summer squash,and thus significantly increase the fresh weight of the squash;the high frequency drip irrigation promotes the nutrient of the squash.Absorption significantly increased nitrogen accumulation in leaves,stems,and melons of squash,and increased nitrogen accumulation and dry matter accumulation in the shoots of squash.Under nitrogen-tolerant?N1?level,the yield of squash was sensitive to drip irrigation frequency,while for high nitrogen?N2?level,the drip irrigation frequency was increased and the yield increase was not significant.2 When the level of nitrogen supply is fixed under the fixed amount of irrigation,the high-frequency drip irrigation can maintain a high soil moisture content in the 0-40 cm soil layer,reduce the deep infiltration,reduce the water consumption of squash,and promote the absorption of water by roots,thus increasing the water content.usage efficiency.The effect of drip frequency on water use efficiency of squash was greater than that of nitrogen fertilizer.Under this experimental condition,high nitrate treatment resulted in high nitrate content in all soil layers,increasing the risk of nitrogen leaching.The nitrification treatment combined with high-frequency drip irrigation can maintain the nitrate nitrogen content in the root zone at a relatively appropriate level,and reduce the risk of nitrogen leaching into the deep layer.3 When the level of nitrogen supply is fixed under the fixed amount of irrigation,the frequency of drip irrigation is increased to make the enzymes of nitrate reductase?NR?,nitrite reductase?NiR?,glutamine synthetase?GS?,and glutamic acid dehydrogenase?GDH?Live at a high level.The net photosynthetic rate,stomatal conductance,and transpiration rate of the leaves of squash were decreased along with the progress of the growth period,and the intercellular CO₂concentration showed an upward trend.At the level of suitable nitrogen?N1?,the frequency of drip irrigation was increased.The net photosynthetic rate,stomatal conductance,and transpiration rate of the leaves maintained at a high level.Compared with the low-frequency drip irrigation,the high-frequency drip irrigation treatment significantly increased the maximum photochemical efficiency and actual chemical efficiency of the leaves of the squash growth period.?Conclusion?High-frequency drip irrigation combined with suitable nitrogen supply?W2N1 treatment?effectively promoted the growth of the squash on the shoot and yielded the highest yield;it also increased the soil moisture content of the upper soil layer and reduced the risk of leaching of nitrogen into deep soil layers.Combining the results of the two-year experiment,the changes in appearance growth indicators and intrinsic physiological indexes of summer squash were consistent with the yield of squash.Considering the consumption of squash and the cost of input costs,it was recommended that the nitrogen application rate of squash in the solar greenhouse in northern cold regions should be 375kg·hm^-2,irrigation frequency is 1 time in 2 days.