Analysis and evaluation of nutrient contents of different layers of virginal and cultivated soils in navel orange orchards of Southern Jiangxi province

Abstract:【Objectives】This study aimed to understand the available nutrient content of soils in navel orange orchards and provide basis for rational fertilization in Southern Jiangxi province.【Methods】Virginal and cultivated soil samples collected from 105 representative orchards in main producing area were analyzed in 2018.【Results】The results showed that, soil pH showed a downward trend in cultivated soil samples, compared with virginal soil samples, and the pH in the soil layer of 20-40 cm was sig- nificantly lower than that in the virginal soil samples. The content of soil organic matter (SOM) in navel orange orchards ranged from 3.1 to 45.0 g · kg-1. The proportion of SOM over the suitable value in the virginal and the cultivated soil samples accounted for 51% and 69%, respectively. The content of SOM in the cultivated soils was significantly higher than that in the virginal soils. The contents of soil available nitrogen (N), phosphorus (P), potassium (K) were 7.3-343.3, 0-175.5 and 0-739.9 mg·kg-1, respectively. The contents of soil available N, P and K in the cultivated soils were significantly higher than those in the virginal soils, and the proportion of high and excess amounts in the cultivated soils was as high as 64%, 91% and 92%, respectively. The contents of soil available Calcium (Ca) and Magnesium (Mg) were 0.5-7 540.7 and 0.4-387.0 mg · kg- 1, respectively. The orchards with deficient and low con- tents of soil available Ca and Mg in the virginal soils accounted for 84% and 99%, respectively. The contents of soil available Ca and Mg in the cultivated soils were significantly higher than that in the virginal soils, but 59% of the soils still had insufficient content of available Ca. The contents of available Iron (Fe), Manganese (Mn), Zinc (Zn) and Copper (Cu) in the soil samples were 0.2-305.7, 0.4-135.3, 0.01-20.07 and 0.01-82.41 mg · kg- 1, respectively. The contents of available Fe, Mn, Zn and Cu in the cultivated soils were significantly higher than those in the virginal soils. The proportion of available Fe, Mn, Zn and Cu exceeding the suitable range in the cultivated soils, which are significantly higher than those in virgin soils accounted for 78.0%, 62.0%, 69.0% and 76.0% in the cultivated soils, respectively.【Conclusion】Compared with the virginal soils, the soil pH decreased obviously, while the contents of SOM and available nutrients such as N, P and K increased in the cultivated soils, and the significant in- crease was mainly found in the 0-20 cm soil layer. Both the virginal and the cultivated soils in navel or- ange orchards of Southern Jiangxi province were found to be highly acidic and severely deficient in the soil available Ca and Mg. Meanwhile, excess of the available soil N, P, K, Fe, Mn, Zn and Cu in South- ern Jiangxi province should also be paid attention in practice.