Intensive Tillage Effects on Wheat Production on a Steep Hillslope in the Sichuan Basin, China

Two treatments (5- and 15-tillage operations) were conducted to assess intensive tillage effects on wheat production in the Sichuan Basin, China. After intensive tillage, wheat grain yields were 55% and 41% in areas of soil loss lower than those in areas of soil accumulation by 5- and 15-tillage operations, respectively. The redistribution pattern in soil depth affected wheat production with a logarithmic correlation between them, resulting in wheat aboveground biomass and grain yield increased along the downslope transect. A much larger decline in production with loss of soil depth than the increase in production with increase in depth was found. Therefore, fields subject to these patterns of soil redistribution could be expected to be subject to decline in average yield. The variations suggest that over time crop production reduction would gradually become serious in areas of soil loss by tillage.

Introduction

Tillage erosion has been proved to be one of the major soil erosion processes on steep hillslopes in the Sichuan Basin[1], [2]. Variations in soil properties and soil degradation induced by tillage erosion have also been reported in different agricultural sloping landscapes [3]–[11]. In these studies, variations in parameters including soil depth, water content, nutrients (N, P, and K), pH, CaCO₃, organic matter content, rock fragment, and particle size fraction have been reported to be affected by tillage erosion. Thereinto, soil depth is regarded as one of the most sensitive parameters which may be affected by erosion [12]. In the hilly areas, long-term soil erosion creates a limited soil depth ranging from less than 0.2 m at the top of hillslopes and at convex slope positions to 0.5–1 m in the valley bottoms. At the top of hillslopes, crops always become yellow earlier than those growing at the bottom of hillslopes, resulting in lower crop production. Crop yields (e.g. wheat, corn and sweet potato) on the hilltop positions were half of that at the bottom positions, or even less [2]. Case studies have also demonstrated that there were higher grain yields or biomass production in areas of soil accumulation by tillage compared with areas of soil removal by tillage [3], [9], [11], [14]. For example, an investigation conducted in hilly areas in west central Minnesota reported that wheat yields in areas of soil loss by tillage were 50% lower than those in areas of soil deposition[11]. In spite of more concerns to variations in crop production under tillage erosion, there is a particular shortage of data concerning Regosols in subtropical environments such as the Sichuan Basin which is also known as China's bread basket. It is, therefore, the main objective of this study to determine the impact of soil erosion by intensive tillage on crop production in the Sichuan Basin.