| Corn is one of the three major cereal crops in our country and also in Henan province.From 1950s to the 1980s,the extensive application of chemical fertilizers and pesticides greatly increased the yield per unit area and total yield of corn,but it also brought serious problems such as resource waste and environmental pollution.How to reduce the use of chemical fertilizers and pesticides,improve the utilization rate of chemical fertilizers and pesticides,reduce environmental pollution and ensure the safety of food production under the premise of ensuring the yield of corn has become a top priority for the sustainable development of agriculture in China.It is one of the important measures to reduce the amount of chemical fertilizers,ensure food production and improve soil fertility that Organic fertilizer partly replaces chemical fertilizers.With the founding of the national key research and development project"Huanghuaihai Summer Corn Chemical Fertilizer and Pesticide Reduction Technology Integrated Research and Demonstration",in order to explore the impact of summer corn chemical fertilizers on the ecological environment of farmland after organic replacement,in the experimental field of Xuchang Campus of Henan Agricultural University,the method of combing field investigation and laboratory analysis was used to study the effects of different levels of organic replacement of chemical fertilizers in summer corn on the arthropod community,growth and development of summer corn,nutrients and secondary metabolites,accumulation of main nutrient elements in summer corn and soil fertility.It is hoped to clarify the appropriate ratio of organic replacement of summer corn chemical fertilizers,and provide a basis for the implementation of summer corn chemical fertilizer organic replacement technology and scientific prevention and control of pests.After two years of research in 2019 and 2020,the following research results have been achieved.(1)The organic substitution of chemical fertilizer does not affect the number of species in the field arthropod community,and affects the dominant species of natural enemy groups and pest groups.In 2019,the uniformity and diversity index of arthropods of various organic alternative treatments were at a low level in each growth period of corn.The results of the 2020 survey showed that the uniformity and diversity index of arthropods of various organic alternative treatments were at a high level,and only the uniformity index at the harvest period was at a low level.This shows that the replacement of chemical fertilizers with organic fertilizers in two years and the treatment with a lower ratio of organic fertilizers can increase the stability of arthropod communities in summer corn fields.The level of organic replacement of chemical fertilizers affects the population of major Lepidoptera pests.In 2019,Lepidoptera larvae after corn filling stage was generally low in the area of lower organic replacement level(20%-40%),of which 20%replacement level(OF20)is similar to the contro,while the population density of Lepidoptera larvae in 2020 shows a high-low-high trend with the increase of the replacement ratio.Organic substitution of chemical fertilizers also affects the population density of underground arthropods.The population density of main arthropods in the treatment area increased,and the stability and diversity also increased.Based on the characteristics of the occurrence of arthropods in the two years,the appropriate organic replacement ratio of chemical fertilizers shoule be 20%-40%.(2)Organic substitution of chemical fertilizers can improve the nitrogen and phosphorus nutrition status of corn and increase the efficiency of nitrogen fertilizer use.In terms of nitrogen accumulation,the nitrogen accumulation in stems and leaves treated with 40%organic substitution(OF40)were the highest,in grains it was with 20%substitution(OF20),while organic substitution did not affect the nitrogen accumulation in bracts.Regarding the accumulation of phosphorus,only the grains were affected by the organic substitution of chemical fertilizers,which were the highest at 20%and 40%replacement treatments in two years.In terms of potassium accumulation,all maize tissues are not affected by the level of organic substitution of chemical fertilizers.From the perspective of corn nitrogen nutrition,the organic replacement ratio of chemical fertilizers 20%-40%(OF20,OF40 treatment)is relatively suitable for summer corn production.(3)Organic substitution of chemical fertilizers can improve the nutrient content of the soil and affect the activity of related enzymes.Soil pH is not affected by the organic substitution of chemical fertilizers;the soil organic matter content is highest in the organic substitution 100%(OF 100)treatment;the alkali-hydrolyzable nitrogen and available phosphorus content are both the highest in the 20%organic substitution(OF20)treatment,the content of available potassium is the highest with 60%organic substitution(OF60)treatment.Acid phosphatase activity is the highest in 20%organic substitution(OF20)treatment,β-cellobiase and urease activities are both the highest in organic substitution 100%(OF 100)treatment;the activities of leucine aminopeptidase and β-acetylglucosaminidase were highest in organic substitution 80%(OF80)treatment and organic substitution 40%(OF40)treatment respectively,while alkaline phosphatase and β-glucosidase changed irregularly;β-xylosidase activity is not affected by organic substitution.From the perspective of soil fertility,20%organic replacement of chemical fertilizers(OF20)is relatively suitable for the local summer corn soil.(4)Organic substitution of chemical fertilizers affects the growth of summer corn and the content of nutrients and secondary biomass.Wth the increase of the organic replacement ratio of chemical fertilizers,the growth indicators of summer corn at the seedling stage gradually decreased,indicating that the nutrient supply of organic fertilizers to the plants at the seedling stage is not as good as chemical fertilizers.There was no significant difference in the content of chlorophyll a,chlorophyll b,and carotenoids in the bell mouth stage and the early booting stage,but there were differences in the total chlorophyll content in different organic substitution treatments,among them,the higher content was at the treatment of organic substitution 40%-60%,which is similar to the control.The soluble sugar content in the bell mouth stage increased with the increase of the proportion of organic fertilizer replacement.The content in each treatment gradually tended to be the same as the groth of corn.In the bell mouth stage,the content of reducing sugars was higher at a medium substitution level(40%-60%).The total phenol content in each treatment did not change significantly from the bell mouth stage to the tassel stage and the filaments at the ear stage,however,the contents in 100%and 80%organic substitution treatment were the highest in the upper and lower leaves of the ear,respectively.The content of tannin only differed significantly between the treatments of the tassels and filaments at the leaf and ear stage at the small flared stage,and the general trend was that the content decreased with the increase of the replacement ratio.When summer corn is harvested,the ear length,ear thickness,thousand-grain weight and yield are all showed better in the treatment with 40%and 60%organic substitution.Considering the corn output in the current season,the appropriate ratio of organic fertilizer replacement is 40%60%.Comprehensive analysis and comparison of the effects of different levels of organic fertilizer substitution on farmland arthropods,summer corn growth and yield,summer corn nutrients and secondary biomass content and macroelement accumulation,soil fertility,etc.,combined with the current organic fertilizer production and application status,this study believes that the organic replacement ratio of chemical fertilizer for summer corn is 20%-40%. |
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