Effects of raising chicken on soil fertility and fruit quality in Citrus orchard

Abstract:【Objective】Soil structure and fertility improvement are important for high yield and quality of fruits in orchard. Manures contain many nutrients necessary for plant growth and fruit development mand are commonly used for increasing soil fertility. Chicken manure is one of the widely used organic fertilizers. The objective of this study was to evaluate the effect of raising chicken in citrus orchard on soil amendment and enrichment efficiency, fruit yield and quality to select suitable chicken raising density and model through 5 years experiment.【Methods】The experiment included four treatments:(1) CK, raising 0 chicken per hm²;(2) T600, raising 600 chickens per hm²;(3) T1200, raising 1 200 chickens per hm²;(4)T2400, raising 2 400 chickens per hm². Chickens were raised every year from January to April and September to December, while no chicken was raised from May to August to ensure herb plants growth and grass could cover the orchard ground and prevent soil and water losses. Composite soil samples(0-20 cm and20-40 cm soil layers) for each plot were prepared by mixing 5 soil cores using serpentine five-spot sampling method for soil nutrients content, enzyme activities, microbe counts and soil natural water content determination. Soil cores were collected at depth of 0-20 cm and 20-40 cm to evaluate soil bulk density,soil pore composition and water- holding capacity. Representative fruits were collected for single fruit weight and fruit quality determination. Membership function was used to transform the soil fertility index-es(including soil bulk density, natural water content, maximum water-holding capacity, capillary waterholding capacity and field water-holding capacity, capillary porosity and non-capillary porosity, bacteria,fungi and actynomycete counts, invertase, urease and phosphatase acitivities, soil organic carbon, total-N,hydrolysis- N, available- P and available- K contents) and fruit quality indexes(including single fruit weight, titratable acid, soluble sugar and vitamin C content in fruit, and ratio of soluble sugar to titratable acid), and to calculate the comprehensive value of soil fertility(CVSF) and fruit quality(CVFQ). Statistical analysis was completed using the SPSS19.0 software package for Windows. Statistically significant differences were identified using analysis of variance ANOVA and Duncan's multiple range test. Relationships among single fruit weight, yield, CVSF and CVFQ were examined by calculating the Pearson correlation coefficient.【Results】Soil bulk density decreased by 2.0%-9.1%, natural water content increased by4.0%-16.6%, maximum water-holding capacity increased by 6.6%-23.0%, capillary water-holding capacity increased by 4.1%-14.8%, field water-holding capacity increased by 5.1%-18.5%, non-capillary porosity increased by 13.7%-39.8% capillary porosity increased by 2.0%-4.2%, total porosity increased by 4.5%- 11.9%; bacteria counts increased by 57.2%- 167.8%, fungi counts increased by 42.4%-200.6%, actynomycete counts increased by 71.3%-155.3%, total microbe counts increased by 57.5%-167.6%, invertase activity increased by 87.3%-214.6%, urease activity increased by 32.0%-102.7%,phosphatase activity increased by 165.9%-421.5%; soil organic carbon content increased by 20.0%-62.8%, total-N content increased by 10.8%-31.0%, hydrolysis-N content increased by 46.7%-108.1%,available- P content increased by 1 480.6%- 2 914.3%, available- K content increased by 120.1%-292.4%; single fruit weight increased by 17.8%-37.4%, fruit yield increased by 10.6%-32.3%, soluble sugar content increased by 7.6%-69.4%, titratable acid content decreased by 6.5%-18.3%, ratio of soluble sugar to titratable acid increased by 15.2%-107.4%, vitamin C content increased by 12.1%-40.5%under raising chicken treatments( including T600, T1200 and T2400) compared with the CK. The CVSF and CVFQ significantly increased by raising chicken treatments, and the values of both were ranked as T2400>T1200>T600>CK. The CVSF was significantly related to single fruit weight(r = 0.941, P<0.01), fruit yield(r = 0.941, P<0.01) and CVFQ(r = 0.978, P<0.01).【Conclusion】Raising chicken in citrus orchard is valuable for improving soil porosity, water-holding capacity, microbe number, nutrients content, enzymes activity, fruit yield and quality, and the effects of the improvement were increased as the increase of the density of chicken raised.