Response Of Grafting Bitter Gourd To Different N And K Fertilization And Screening Of Bitter Gourd Germplasm With Low Potassium Sensitivity

As the scale of bitter gourd grows year by year,the excessive application of fertilizers has caused problems such as soil nitrate leaching,environmental pollution,destruction of biodiversity,and farmers’increase in production but not income.Changing traditional blind fertilization methods and cultivating fertilizers with high-efficiency utilization types are the solutions.The important way of the problem.This study took grafted bitter gourd as the material,firstly explored the absorption and distribution of nitrogen,phosphorus and potassium in each growth period of grafted bitter gourd under the application of 6 kinds of nitrogen and potassium ratio,as well as the effects of different amounts of nitrogen and potassium on the growth physiological characteristics,yield and soil chemical properties of grafted bitter gourd;At the same time,the effects of six organic fertilizers partially replacing chemical fertilizers on the cumulative uptake of N,P and K,fruit quality,soil microbial content and yield of the grafted bitter pear were explored,so as to improve（maintain）crop yield and quality and protect the ecological environment on the basis of reducing chemical fertilizer application.Secondly,11 balsam pear germplasm were used as materials,and two treatments of low potassium(K⁺0.2mmol·L^-1)and normal potassium(K⁺4mmol·L^-1)were set to analyze the growth and physiological indexes of balsam pear germplasm under low potassium stress by multivariate statistical method,to determine the screening indexes most sensitive to stress response,and to explore the germplasm resources that are tolerant to low potassium.In order to provide germplasm resources for the production of recommended varieties with low potassium tolerance or the cultivation of varieties with low potassium tolerance and high yield of balsam pear.The results are as follows:（1）The dry matter accumulation of stem,leaf and fruit was significantly positively correlated with the nitrogen supply level under the same K application at seedling stage and primary stage.At full fruit stage,there was a significant positive correlation with nitrogen supply level.T2(N 260 kg·hm^-2,K₂O 430 kg·hm^-2)treatments had significantly higher dry matter accumulation in various organs at different growth stages than other treatments,and the total amount of dry matter accumulation and fruit dry matter in the full fruit stage The distribution rate reached the maximum,respectively 590.76g/plant and 43%;The nutrient accumulation of N,P and K increased with the extension of growth period,and the demand for K was higher,followed by N and P.Compared with other treatments,T2 treatment significantly enhanced the nutrient supply capacity of leaves（source）to fruits（sink）,The dry matter distribution rate of the fruit’s nitrogen,phosphorus,and potassium is as high as 59%,48%,48%in the mature period.At the same time,it significantly increases the growth of grafted bitter gourd,expands the average root diameter and root surface area,and enhances the activity of soil enzymes（urease,alkaline phosphatase,invertase,and catalase）.Reduce the change range of soil organic matter,available nitrogen,available potassium,and available phosphorus content,promote the transformation of soil nitrogen,phosphorus,and potassium into the plant body,improve the nutrient absorption and utilization efficiency of grafted bitter gourd,and increase the average weight and yield of grafted bitter gourd 37.1%,46.4%.（2）Dry weight of stems and leaves,dry weight of fruits,dry weight of plants and yield per plant all reached the maximum when the replacement ratio of organic nitrogen was 30%,which increased by 9.20%,5.62%,7.03%,3.91%respectively compared with N0 treatment;Grafted bitter gourd and self-rooted bitter gourd had similar trends in the cumulative uptake of nitrogen,phosphorus,and potassium.With the gradual increase in the replacement ratio of organic nitrogen,both increased first and then decreased,and reached the maximum when the replacement ratio of organic nitrogen was 30%;Grafting cultivation is significantly better than self-rooting seedling cultivation,and the utilization efficiency of nitrogen and potassium increases by 14.5%and 17.3%respectively;Compared with N0,the content of organic acid,soluble prorogen instead of chemical fertilizer nitrogen N2,N3,N4,N5,N7 increased significantly,and the combined application of organic fertilizer can increase Fruit quality;Organic fertilizer nitrogen fertilizer replaces chemical fertilizer nitrogen to increase the number of bacteria and actinomycetes in the soil,reduce the number of fungi,and the number of fungi.Compared with N0 treatment,N2～N7 decreased by 6.6%～19.7%.Through the principle component analysis and comprehensive scoring method,it is best to determine that the ratio of organic fertilizer to replace chemical fertilizer is 30%.（3）15 identification indexes of 11 balsam pear germplasms（plant height,stem thickness,internode length,leaf area,underground dry weight,above-ground dry weight,root length,root surface area,root volume,chlorophyll a,chlorophyll b,carotenoids,Total chlorophyll,malondialdehyde,potassium accumulation）have a large variation range,and the coefficient of variation is more than 10%;Using principal component analysis,the stress coefficients of 15 identification indicators were standardized（Z-score method）and then subjected to dimensionality reduction.All factors were divided into 4 principal components,which explained 83.690%of the total variation;The membership function value is calculated according to the scores of 4 principal components to finally determine the comprehensive index D value,and the cluster analysis method is used to classify 11germplasms to obtain:The first type 04-25,1717,KG01-2,03-8 are low potassium tolerant germplasm,the second type 1721,11-8,DD14-1,04-17-4,26-2 are medium low potassium tolerant Germplasm,the third category 06-16 is low potassium sensitive germplasm,and the fourth category 25-15 is low potassium sensitive germplasm.Multiple regression analysis obtained the optimal regression equation Y=0.768PH+0.443KA+0.390RS+0.595Ca-0.415,which can be used as a comprehensive evaluation model for the tolerance of bitter gourd to low potassium.In summary,T2 treatment(N 260 kg·hm^-2,K₂O 430 kg·hm^-2)has the most significant effect on increasing the yield of grafted bitter gourd,and the ratio of organic fertilizer to chemical fertilizer is 30%.The overall effect is the best（based on principal component analysis Comprehensive score）,which can be promoted and applied in production according to specific conditions;Under low potassium conditions,plant height,potassium accumulation,root surface area,and chlorophyll a can be used as evaluation indicators for low potassium tolerance of bitter gourd.04-25,1717,KG01-2,03-8 are low potassium tolerance germplasm.It can be used as a germplasm resource for cultivating balsam pear varieties with low potassium tolerance and high yield.