Changes in Nutrient Surpluses and Contents in Soils of Cereals and Kiwifruit Fields

Knowledge of nutrient surpluses in soils is critical to optimize nutrient management and minimize adverse environmental effects. We investigated the nutrient surpluses in soils in two regions over 25 years (1992 to 2017) in the south Loess Plateau, China. One region has cereals as the main crop, whereas in the other region, the main cereal crops was changed to kiwi orchards. The inputs of nitrogen (N), phosphorus (P), and potassium (K) increased rapidly (by 74%, 77%, and 103% from 1992 to 2017 in the cereal region; and by 91%, 204%, and 368% in the kiwifruit region), while the nutrient outputs were relatively stable, which resulted in increasing nutrient surpluses (the annual averaged surpluses of N, P, and K were 178, 62, and 12 kg ha−1 y−1 for the cereal region; and 486, 96, and 153 kg ha−1 y−1 for the kiwifruit region) and lower nutrient use efficiency (NUE). The higher N surplus in the orchard-dominated region caused high nitrate N accumulation (3071 kg N ha−1 of 0–5 m in 11–20 y in the kiwifruit orchard) in deeper soil profiles. Similarly, high P and K surpluses in the orchard-dominated region increased soil available P and K. This highlights that comprehensive measures should be taken to control nutrient surpluses, which will help balance nutrient inputs and outputs and minimize nutrient losses in intensive horticultural crop systems.