Effects Of Water-calcium Coupling On Yield And Quality Of Pepper In Substrate Culture

As a common vegetable crop in China,pepper（Capsicum annuum L.）has high nutritional value.With the demand for pepper is increasing accordingly.Water and fertilizer are two key factors affecting the yield and quality of facility peppers.Calcium is an essential nutrient element for plant growth and development,especially for Solanaceous crops including pepper.However,there are few studies on the effect of water-calcium coupling on the yield and quality of pepper.Therefore,in this study,chosen’Bolon（37-94）Bolon RZ F1’as the experimental material to carry out two parts of experiment:（1）Screening the optimal water and calcium treatment solution during pepper substrate cultivation:the trial of three irrigation levels（the relative water content of substrate was controlled at W1:40%-50%,W2:55%-65%and W3:70%-80%）,four calcium supplies(calcium nitrate was used for supply,and other elements were supplied according to the special formula of Yamazaki pepper nutrient solution.Setting C1:1.0 mmol/L,C2:1.5 mmol/L,C3:2.0 mmol/L and C4:2.5mmol/L Ca²⁺concentration),a total of 12 treatment levels.（2）Optimal treatment validation and regulatory mechanism study:the best treatment chosen by experiment（1）was used as the control（CK）,the optimal treatment screened in 2021was recorded as T1,adding Ca²⁺（T2）equal to T1 on the basis of CK,on the basis of CK,NO₃^-equal to T1 was added（T3）were performed and a total of 4.The quality,yield and water use efficiency（WUE）were comprehensively evaluated by using principal component analysis（PCA）,TOPSIS model analysis based on combination weighting（TOPSIS-CW）,grey correlation analysis model（GRA）and fuzzy membership function analysis（MFA）.The optimal treatment level to achieve the highest yield and quality of pepper was determined,and verification tests were conducted in 2022 to verify the effect of the optimal treatment and the effects of Ca²⁺and NO₃^-on pepper,in order to provide a theoretical basis for high-quality production of pepper.The main research results are as follows:（1）Irrigation rate and calcium application rate had significant effects on leaf chlorophyll content,photosynthetic gas exchange parameters,dry matter accumulation,yield,water use efficiency（WUE）,fertilizer partial productivity（PFP）and matrix enzyme activity of pepper in substrate bag culture.Under the same calcium level,the yield and WUE of pepper first increased and then decreased with the increasing of irrigation amount,and reached the peak value in W2 irrigation level.Under W2 irrigation level,the photosynthetic gas exchange parameters,the contents of soluble sugar,reducing sugar,total soluble sugar and vitamin C of pepper fruit increased with the increasing of calcium application.（2）PCA,TOPSIS-CW,GRA and MFA were used to comprehensively evaluate the yield,quality and WUE index of pepper.The optimal treatment of the four algorithms was W2C4,that is,maintaining the standard irrigation with the matrix water content of 55%-65%and Ca²⁺concentration in the nutrient solution of 2.5mmol/L.It can make the matrix bag culture pepper yield reach the highest,and the fruit comprehensive evaluation value ranks the first.（3）The verification test results showed that compared with W2C2 treatment,W2C4 treatment significantly enhanced the photosynthetic capacity and carbon and nitrogen metabolism capacity of pepper,which in turn promoted the growth and development of pepper.Meanwhile the water use efficiency and fertilizer partial productivity of N,P,K,and Ca of the plants were significantly increased,which finally achieved high quality and high yield.Under this treatment,the yield of pepper was 65438.2 kg/hm²and the WUE was 38.47 kg/m³.At the same time,the fruit quality,yield,WUE and enzyme activities related to carbon and nitrogen metabolism of pepper were analyzed using principal component analysis,and three principal components with eigenvalues greater than 1 were extracted:vitamin C,capsaicin and glutamate dehydrogenase（GDH）,and it was calculated that Ca²⁺played a greater role than NO₃^-in the applied calcium fertilizer with the contribution of different components as weights.