Research On The Combination Pattern Of Organic-Chemical Fertilizers And Water Consumption Modeling Of Greenhouse Cucumber

Excessive application of chemical fertilizers not only resulted in the degradation of agricul-tural products quality,but also aggravated agricultural non-point source pollution and resource constraint.The development of ecological organic agriculture is an important promoter of reducing the application of chemical fertilizers and improving the soil ecological environment.It is of great significance to explore the effects of nitrogen reduction combined with organic fertilizer applica-tion on soil environment and crop growth to put forward the fertilization management mode of cost saving,quality improvement and efficiency enhancement,promote the green development of ecological agriculture and the sustainable utilization of soil.In this study,the cucumber in a Venlo-type greenhouse was treated with organic fertilizer at different rates of nitrogen reduction:conventional level of application(N1,270 kg ha^–1),20%nitrogen reduction(N2,216 kg ha^–1)and 40%nitrogen reduction(N3,162 kg ha^–1)and combined with three organic fertilizer levels（nine treatments in total）:high organic application(O1,9 t ha^–1),medium organic application(O2,6 t ha^–1)and low organic application(O3,3 t ha^–1).Meteoro-logical data,soil volumetric water content（SWC）,soil nitrate-Nitrogen content（NO₃^–N）,cucum-ber growth and physiological indicators（plant height,stem diameter,LAI,photosynthetic rate,stomatal conductance and stem flow rate）,yield and water use efficiency（WUE）were observed in the greenhouse during the autumn-winter and spring-summer planting seasons.Analyze the vari-ations and differences of soil NO₃^–N content,cucumber plant height,stem diameter and LAI under different nitrogen reduction and organic fertilizer treatments.Investigate the response of the cu-cumber photosynthetic rate,stomatal conductance,stem flow rate,yields and WUE to different organic fertilizer treatments with reduced nitrogen.The dynamics of evapotranspiration（ET_c）dur-ing spring-summer and autumn-winter planting seasons of greenhouse cucumber under O2N2treatment were simulated by pan evaporation method（K_p model）,Penman-monteith model（r_cmodel）,dual crop coefficient model（K_c model）and Priestley-Taylor model(α_PT model)based on key parameters modified.The accuracy of the different models was evaluated with the measured values by lysimeter.The main findings are as follows:（1）At N2 level,the variation of SWC decreased with the reduction of organic fertilizer application,and the variations of SWC in spring-summer planting season under the treatments of O1N2,O2N2 and O3N2 were 20.4-43.9%,18.8-39.9%and 18.1-35.5%,and 24.3-37.6%,23.5-35.3%and 17.8-34.3%in autumn-winter planting season which indicated that the application of organic fertilizer can improve the water retention capacity of the soil.At the same level of organic fertilizer application,the NO₃^–N content of soil in the 0-30cm soil layer increased with the increas-ing in nitrogen application（N1>N2>N3）,and the NO₃^–N content of soil decreased with the increasing in soil depth.Meanwhile,the NO₃^–N content of soil increased with increasing organic fertilizer application at the same level of nitrogen fertilizer application（O1>O2>O3）.At differ-ent levels of organic fertilizer application,the soil NO₃^–N content increased by 1.8%（O1）,3.6%（O2）and 9.6%（O3）at the N1 level compared to the N2 level,and at different levels of nitrogen reduction,the soil NO₃^–N content increased by 1.2%（N1）,1.9%（N2）and 6.8%（N3）at the O1level compared to the O2 level which indicated that medium amount of organic fertilizer with a20%nitrogen reduction（O2N2）did not significantly reduce soil NO₃^–N content.（2）Nitrogen reduction combined with organic fertilizer treatment had significant effects on cucumber plant height,stem diameter and LAI.Under the treatment of N2 and N3,the low amount of organic application fertilizer（O3）resulted in short plant height of cucumber,while the applica-tion of medium amount of organic fertilizer（O2）could not timely supply nutrient under N3 caus-ing the loss of soil nutrients,which resulted in slow growth of cucumber.There was little difference in stem diameter of cucumber under different nitrogen fertilizer levels,and the stem diameter in-creased gradually with the increasing in organic fertilizer application under the same nitrogen fer-tilizer level.The variations of LAI presented a single-peak curve,which reached the maximum value in the Mid-season stage and showed a slightly decreased in the Late-season stage.The LAI decreased with the decreasing in the application of organic fertilizer and nitrogen fertilizer.（3）The leaf photosynthetic rate and stomatal conductance of cucumber under different treat-ments showed a double-peaked curve change in the Mid-season stage,and in the Late-season stage,the photosynthetic rate and stomatal conductance of cucumber leaves showed a double-peaked curve in spring-summer planting season,and a single-peaked curve in autumn-winter planting sea-son.The cucumber stem flow rate showed a single-peaked curve during the spring-summer and autumn-winter planting seasons;at the N2 level,cucumber stem flow rate increased with the in-creasing organic fertilizer application.There was no significant difference between O1N2 and O2N2;the cucumber stem flow rate was significantly lower under the medium organic fertilizer application and 40%N reduction treatment（O2N3）.At the same level of organic fertilizer appli-cation,the cucumber yield,soluble solids and WUE decreased with increasing nitrogen reduction（N1>N2>N3）.In addition,the cucumber yield,soluble solids and WUE increasing with in-creasing organic fertilizer application（O1>O2>O3）under the same nitrogen reduction treatment.The results of the comprehensive analysis with the effect of different rates of nitrogen reduction with organic fertilizer on the yield,soluble solids and WUE of greenhouse cucumber,recom-mended the medium level organic fertilizer(O2:6t ha^–1)with 20%nitrogen reduction(216 kg ha^–1)as the best fertilizer application ratio for greenhouse cucumber.（4）By comparing the estimation results of different ET_c models,it was found that the r_c model performed better in estimating the daily ET_c of greenhouse cucumber during spring-sum-mer planting season,the K_c model performed best in estimating ET_c in autumn-winter planting season.Theα_PT and K_p models significantly overestimated and underestimated the measured ET_cby 12%and 19%,respectively.The MAE between of the modified K_p,r_c,K_c andα_PT models and simulated ET_c during the spring-summer planting season were 0.62,0.27,0.41 and 0.40 mm d^–1,with R²of 0.94,0.91,0.98 and 0.93,respectively.The MAE were 0.26,0.38,0.24 and 0.40 mm d^–1,with R² of 0.94,0.82,0.91 and 0.96 in autumn-winter planting season.The E_g/ET_c values calculated using the modified K_c andα_PT models of cucumber in spring-summer planting season were 22.2%and 24.0%,and 26.5%and 26.1%in autumn-winter planting season,respectively.Which indicating that E_g/ET_c values in autumn-winter planting season were higher than those in spring-summer planting season.The K_c model has better performance thanα_PT model in estimat-ing daily ET_c and T_r.