Relative elevation, as one of the decisive factors to the redistribution of soil water, nutrients, sunshine, and temperature in a region influences apple yield and quality by adjusting soil water and nutrients. To explore the impact of relative elevation on apple quality, this research investigated the conditions of soil moisture and nutrients at different elevations of terrace apple orchards in the hilly-gully region of the Loess Plateau. The results showed that soil water content decreases when the elevation increased, whereas soil nutrients fluctuated significantly at different elevations of terrace orchards and the contents were lower than the standard level of the Loess Plateau, especially soil organic matter, but total potassium was higher. The apple firmness increased when the elevation increased and had a good linear relationship with elevation. Apple vitamin C content in weed-covered orchards was higher than in the ploughing and weeding management orchards. The impact of soil nutrients, including soil water, nitrogen, phosphorus, and potassium on apple quality were concentrated in soluble solid and total acid. Irrational irrigation or partial use of nutrients, such as more use of nitrogen and less use of phosphorus and potassium, may deteriorate the apple quality. Therefore, we suggested that the amount of irrigation be increased appropriately with the raising of elevation. Moreover, part of the weed should be kept to cover the orchard, as well as mowing regularly and covering the surface. This would not only improve water use efficiency and increase soil organic matter content, it would also maintain apple quality and ensure sustainable development of the apple orchards.
Effects of revegetation on soil moisture under different precipitation gradients in the Loess Plateau, China
