Effects of carbon to nitrogen ratio on mango tree pruning compost

【Objective】 To explore the influence of initial materialdifferent carbon to nitrogen(C/N) ratios on the humification degree of mango tree pruning during composting, and provide a reference for cleaner production and waste recycling in mango orchards.【Method】In the Mango Industrial Park Base of Renhe District, Panzhihuan City, Sichuan Province, the pruned mango branches and leaves containing high C/N and hardly biodegradable lignocellulose were used as raw materials. T20(C/N=20), T25(C/N=25), T30(C/N=30) were treated, and C/N=63.63 was used as the control (CK) to determine the dynamic changes of the physicochemical properties of compost.【Result】 The physical and chemical properties of compost did not change linearly with the increase of C/N. The pH and EC of compost were within the normal range of compost maturity standard. The pH of CK was lower than that of the other three treatments, and the conductivity(EC) of T25 was lower than that of the other three treatments. The cellulose degradation rates were 7.54%, 32.21%, 12.87% and 8.75%, respectively. The content of humic acid decreased as a whole, and the overall change rule of fulvic acid content was from down to up to down. The duration of high temperature period(5 and 8 d) and the index of seed germination index(GI) (0.89 and 0.93) of T20 and T25 treatments met the requirements of composting maturity. According to the ratio(T value) of terminal C/N to initial C/N and humification index, only T25 treatment met the requirements of humification. The duration of high temperature period of T30 treatment and CK was 4 d, and T values were 0.84 and 0.73, which did not meet the humification standard of T ≤ 0.60. GI were 0.75 and 0.76, failing to meet the requirements of GI>0.85. The humification indexes were 0.85 and 1.25 respectively, and T30 treatment did not meet the humification standard that the humification index was no less than 1.00.【Conclusion】 When the initial material C/N=25, it can promote the the degradation of organic matter and cellulose, the accumulation of high temperature in the pile and the increase of seed GI, and the composting cycle is shortened, and the comprehensive effect of composting is the best.