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Because of serious soil erosion on the Loess Plateau, land degradation results in a serious impact not only on the sustainable development of the social economy of the Loess Plateau, but also on the loss of local soil nutrients and the reduction of soil fertility, thus limiting the restoration of vegetation on the Loess Plateau. Soil nutrients are important signs of soil fertility. Supplying and coordinating the nutrient conditions and environmental conditions of plant growth plays an important role in the sustainable use of land.
Soil nutrient analyzer sampling method: The understory soil was collected, the sampling depth was 60cm, a total of 3 layers were taken, each layer was separated by 20cm; the soil profile of the same layer was sampled at different heights and different parts for 5 times, and the soil samples were taken. Mix and bring it back to the lab. Before the experiment, the plant roots, visible plant residues and other impurities in the soil were removed, mixed and air-ground, and sieved through 1 mm and 0.25 mm for the determination of soil nutrient analyzer. The soil nutrient content in the soil profile of the study area collected by the sample was obvious. The gradation. The soil nutrient content was highest in 0-20 cm soil surface, and gradually decreased with the increase of soil depth. The nutrient indices of total nitrogen, available nitrogen, available potassium, and available phosphorus were highly significant among all levels. The contents of total nitrogen in the soil surface at 0-20 cm are 1.28 and 1.72 times that of 20-40 and 40-60 cm soil layers respectively; the contents of available nitrogen in the soil surface at 0-20 cm are respectively 20-40, and 40-40 cm in the soil 1.40 , 1.49 times;
The content of available nitrogen and available phosphorus which can be used directly by plant growth in the study area is very small. However, available nitrogen and quick-acting phosphorus are also one of the main indicators for determining soil fertility. Overall, the soil fertility in the study area is overall at a low level. . Soil nutrient analysis showed that there was no significant difference in nutrient content between soil layers, and there was no significant difference in nutrient index content. This was consistent with Xu Mingxiang et al.'s conclusions on soil nutrient characteristics and evolution of Robinia pseudoacacia plantation in the Loess Hilly Region.
In a lot of research, the use of modern scientific and technological instruments soil nutrient analyzer to explore the different types of vegetation on the returning farmland in the Loess Hilly Region and its effect on soil nutrient efficiency under different growth conditions, to provide for the vegetation in the construction of the abandoned vegetation in the loess hilly region in the future. Theoretical basis. The main afforestation tree species (Hippophae rhamnoides, Mixed forest of Seabuckthorn, Seabuckthorn and Hippophae rhamnoides mixed forest land) on the reclaimed farmland in the loess hilly region were taken as the research object, and three different vegetation types and soil nutrient characteristics under different growth conditions were analyzed and studied.