Analysis and evaluation of soil fertility of main peach orchards in Guanzhong area of Shaanxi province

Abstract: 【Objective】Peach is an important cash crop in Shaanxi province, which plays an important role in increasing farmers' income and rural revitalization. According to the statistics of Shaanxi Yearbook in 2021, peach producing areas in Shaanxi are mainly concentrated in the Guanzhong Plain, with an output of about 640 000 t, accounting for about 84% of the peach output in the province. Among them, Xianyang area (XYA) ranks the first, and the main producing areas are distributed in Liquan, Jingyang and Qian county, followed by Dali county in Weinan area (WNA). Although Shaanxi is a suitable ecological cultivation area for peach, the overall fruit quality is not satisfactory. Peasant household’s lack of scientific soil management for peach orchards is a major reason, and growers mainly rely on experience to fertilize and conduct daily soil operations. Therefore, in this study, soil samples from the main peach producing areas in Guanzhong, Shaanxi province were collected to quantitatively determine their nutrient elements, so as to understand the soil conditions of peach orchards in Guanzhong area of Shaanxi province, explore their physical properties and nutritional abundance, and provide scientific basis for soil management and fertilization in peach orchards.【Methods】Soil samples at 0-20 cm and ＞20- 40 cm soil layers were collected from 24 peach orchards in Xianyang area (XYA), Baoji area (BJA), Tongchuan area (TCA) and Weinan area (WNA) in Guanzhong region of Shaanxi province. Based onthe nutrient classification standard of the second national soil survey and previous studies, the soil nutrient status in major peach orchards in Guanzhong region of Shaanxi province was evaluated and analyzed. The surveyed indexes included soil bulk density, porosity, pH value, organic matter, total nitrogen, effective phosphorus, effective potassium, nitrate nitrogen and ammonium nitrogen contents.【Results】The soil bulk density and porosity at 0-20 cm soil layer of peach orchards in Guanzhong area of Shaanxi province were found in a suitable range. However, at the ＞20-40 cm soil layer, the soil volume density was high in XYA and high with low porosity in BJA, which were beyond the suitable range. The soil was relatively tight, which was not conducive to soil nitrogen permeability and water retention. The average pH value in peach orchards soil in Guanzhong region was 8.1, except for the pH value in BJA between 6.4 and 6.9, which in other areas were alkaline soil, with pH values between 8.2 and 9.0. The overall level of soil fertility in Guanzhong region was not high, and especially the soil organic matter was in the most lacking status. At 0-40 cm soil layer, the soil organic matter and total nitrogen contents of more than 66.7% peach orchards were at deficient levels. The content of organic matter and total nitrogen decreased with the increase of soil depth. The average content of 0~20 cm soil in Guanzhong area was 12.38 g·kg-1 , and at ＞20-40 cm soil layer it was 10.5 g·kg-1 . In addition, the average total nitrogen content at 0-20 cm soil layer was 0.81 mg · kg-1 , and at ＞20-40 cm soil layer it was 0.58 mg·kg-1 . The effective phosphorus and effective potassium contents at 0-20 cm soil layer in the investigated area were basically not in shortage state, but with the increase of soil depth, some of the soil at ＞20-40 cm soil layer was in lacking state, especially in TCA. In the soil of 0-20 cm soil, the proportion of effective phosphorus content at the deficiency level was 16.7% and in ＞20-40 cm soil it was 58.3%. In terms of effective potassium content, the orchards with 0-20 cm soil at abundant or suitable level accounted for 37.5%, and in ＞20-40 cm soil, they were at a deficient level. The average content of active nitrogen (active nitrogen=nitrate nitrogen + nitrate nitrogen) in peach orchard soil in Guanzhong region was 10.8 mg · kg-1 , which was in a lacking state. Among them, the highest nitrate nitrogen and ammonia nitrogen contents were found in WNA, followed by XYA and TCA, and the lowest was found in BJA.【Conclusion】According to this survey, the results of the soil fertility status of the main peach orchards in Guanzhong region, Shaanxi province showed that the nutrient resource management in this region should focus on increasing the soil organic matter content, fertilizing the soil and promoting the conversion of total nitrogen to mineral nitrogen. Among them, XYA and BJA areas should strengthen the deep loosening and soil preparation to increase the air permeability and water retention at ＞20-40 cm soil layer. Mainly affected by the geographical location, the soil pH of peach orchards in XYA, TCA and WNA except BJA was in a weak alkaline or strongly alkaline state, so the technology can be used by applying more acidic fertilizer or orchard grass to adjust the soil pH value. The contents of total nitrogen and organic matter, mineral nitrogen, namely nitrate nitrogen and ammonia nitrogen, were lacking. The main source of soil nitrogen is the provision of organic matter after mineralization and decomposition, so it is very important to fertilize the soil by increasing the content of soil organic matter.