Stoichiometric characteristics of soil carbon, nitrogen and phosphorus in mango orchard in karst area of Guangxi

【Objective】 This paper explored the spatial differentiation law of soil nutrient ecological stoichiometry characteristics in karst area and the influence of the geological background of rich calcium and alkali on soil organic carbon, total nitrogen, and total phosphorus ecological stoichiometry characteristics in karst area, providing scientific reference for revealing the soil nutrient cycling law and scientific fertilization in karst area.【Method】 Typical karst samples were selected from the mango planting base in Tianyang County, Baise City, and surface soil samples were collected from different geomorphic sites including depression, transition zone between depression and slope, slope and saddle. Soil organic carbon, total nitrogen, total phosphorusand related soil elements were measured. The stoichiometric characteristics of soil carbon(C), nitrogen(N) and phosphorus(P) and their influencing factors were analyzed using statistical method.【Result】 The average contents of organic carbon, total nitrogen and total phosphorus in the study area were 17.24, 2.31 and 0.70 g/kg respectively. The average values of C:N, C:P and N:P in soil were 7.43, 26.11 and 3.44, respectively. In the study area, soil organic carbon and total nitrogen contents were the highest in slope, the lowest in depression, total phosphorus content was the highest in saddle, and showed a decreasing trend from depression land, transition zone and slope land. C:N, C:P and N:P showed the order of slope > depression-slope transition zone > depression > saddle. The results of statistical analysis showed that cation exchange capacity(CEC), pH, water content, bulk density and total calcium content had a good explanation for the stoichiometric characteristics of soil organic carbon, total nitrogen and total phosphorus in karst area. Partial correlation analysis showed that calcium was an important factor affecting organic carbon and total nitrogen. The correlation of soil organic carbon, total nitrogen and total phosphorus stoichiometry with CEC and total cadmium was controlled by calcium. The correlation between available state elements and soil organic carbon, total nitrogen and total phosphorus stoichiometry was less restricted by pH and calcium.【Conclusion】 Soil C, N and P stoichiometry in the study area is affected by geomorphic location, and soil total calcium content is an important influencing factor for soil C, N and P stoichiometry. In agricultural production in the study area, fertilizer with high element availability, especially P, should be applied, and targeted supplement should be made according to the characteristics of fertilizer demand in the growth stage of fruit trees.