Effect Of Bio-organic Combined With Reduced Fertilizer On Continuous Cropping Soil Physiochemical Properties And Nutrient Utilization Rate Of Cucumber

Aiming at the problems of poor growth and yield reduction of cucumber caused by continuous cropping obstacles,this study conducted field plot experiments to study the physical and chemical properties of the continuous cropping soil,the nutrient utilization rate and the yield of cucumber from two dimensions:the amount of bio-organic fertilizer addition and the reduced fertilizer.The study is expected to improve the continuous cropping obstacle soil and increase the nutrient utilization rate of cucumber by the bio-organic fertilizer combined with reduced fertilizer,and then achieve the purpose of increasing yield and efficiency.The results are significance for ensuring food security and agricultural sustainable development.A field plot experiment was conducted with cucumber as the test crop.There are nine treatments(T1-T9)divided into three treatment groups.They are CK treatment groups with0 t/hm~2bio-organic fertilizer addition(T1 0%,T2 10%and T3 20%),Y1 treatment group with10 t/hm~2bio-organic fertilizer addition(T4 0%,T5 10%and T6 20%)and Y2 treatment group with 20 t/hm~2bio-organic fertilizer addition(T7 0%,T8 10%and T9 20%).Through the continuous cropping process of the fifth,sixth and seventh seasons,the effects of bio-organic fertilizer and reduced fertilizer on the fertility characteristics of the continuous cropping soil,the nutrient utilization rate and yield of cucumber were studied.The mechanism of continuous cropping obstacles and the effect of improving continuous cropping obstacles were discussed.The cluster analysis of the fertilizer utilization rate of cucumber was used to select best amount of bio-organic fertilizer application and reduced fertilizer,the random forest model was used to find the key factors that have a significant impact on the fertilizer utilization rate,and finally the multivariate non-linear regression equations between the cucumber yield and the amount of bio-organic fertilizer and fertilizer was established to seek the theoretical maximum yield of cucumber.The results can provide scientific data for improving nutrient utilization rate and reducing crop continuous cropping obstacles.The main results were as follows:(1)With the increase of the amount of bio-organic fertilizer application,the soil p H showed an increase trend.In the fifth season,compared with the CK treatment group,the soil p H of the Y1 treatment group and Y2 treatment group increased by 0.08-0.12 and0.08-0.14,respectively.The soil bulk density and soil electrical conductivity showed a decline trend.In the fifth season,compared with the CK treatment group,the soil bulk density of the Y1 treatment group and Y2 treatment group reduced by 0.05-0.11 and0.15-0.22,respectively.The soil electrical conductivity of the Y1 treatment group and Y2treatment group reduced by 9.09%-11.90%and 17.97%-18.25%respectively.The content of soil available nutrients(nitrate nitrogen,ammonium nitrogen,available phosphorus and available potassium)showed an increased trend.The quality of soil hydraulic properties were improved.The nitrogen,phosphorus and potassium nutrient utilization rate and agronomic utilization rate of cucumber,the cucumber yield and fertilizer partial factor productivity all showed an upward trend.(2)Under the same amount of bio-organic fertilizer application,with the decrease of fertilizer application,the amount of soil available nutrient and electrical conductivity both show a decline trend.With the decrease of fertilizer application,the nutrient utilization rate of the nitrogen,phosphorus and potassium in both Y1 group(T4,T5 and T6)and Y2 group(T7,T8 and T9)showed a decreased trend.This result showed that the fertilizer utilization rate could be improved by reducing the amount of fertilizer application.Among the 9treatments in the 3 treatment groups,T9 from the Y2 group had the highest nutrient utilization rate of the nitrogen,phosphorus and potassium.(3)The cluster analysis was used to study the effect of bio-organic fertilizer and reduced fertilizer on the nutrient utilization rate of cucumber.The 9 treatments were finally divided into 3 categories:the first category included T1,T2 and T3.These treatments did not add bio-organic fertilizer,and the value of the measured index were generally low.The second category included T4,T5,T6 and T7,compared with CK treatment group.The nutrient utilization rate of the nitrogen,phosphorus and potassium of cucumber was improved significantly.The third category included T8 and T9,these two treatments had the most significant effect on improving the fertilizer utilization rate of cucumber.Compared with the CK treatment group,the nutrient utilization rate of cucumber were improved significantly.(4)The random forest analysis was used to study the relationship between various fertility indicators and nitrogen fertilizer utilization rate.The result showed that the content of the soil total salt was the most important factor for nitrogen fertilizer utilization rate.Other key factors that affected nitrogen fertilizer utilization rate significantly were field water holding capacity,the content of soil available water,wither coefficient and the average mass diameter of the aggregates.(5)The multivariate non-linear regression equations between the cucumber yield and the amount of bio-organic fertilizer and fertilizer was established to seek the theoretical maximum yield of cucumber.The result showed that when the amount of bio-organic fertilizer and fertilizer application were 20 t/hm~2and 0.92 t/hm~2respectively.The theoretical maximum yield of cucumber was 23.56 t/hm~2.This showed that excessive input of fertilizer will reduce the yield of cucumber,so the reasonable application of fertilizer should be used to obtain the highest yield of cucumber.