The effect of deep-tillage depths on crop yield: A global meta-analysis

Abstract

Global soil compaction is occurring at an unprecedented rate (Eswaran 2004). Worldwide compaction has degraded an estimated 427 000 km 2 of soil (Sonderegger and Pfister 2021), particularly because of the development of heavy-agricultural machinery and intensification of the cropping system (Stoessel et al. 2018). As one of the main soil degradation types in the world, soil compaction causes high bulk density, poor aeration, low water conductivity, strong strength, and consequently reduces crop growth and yield (Tracy et al. 2011).Deep tillage is the most effective way to release compacted soil at a global scale, which can decline soil bulk density and increase its pore space by mechanical modification. Therefore, soil water storage, saturated hydraulic conductivity, and air permeability are improved under deep tillage (Drewry et al. 2000).

Variable Depth Tillage: Importance, Applicability, and Impact—An Overview

“…However, there have been a number of studies on different types of deep tillage. Huang et al [18] carried out a meta-analysis based on over 200 studies conducted worldwide, which showed that crop yield increases with deep tillage at 25-35 cm depth and then decreases with increasing tillage depth. According to the authors [18], the optimal depth of tillage for wheat, maize and soybean worldwide is 35 cm; and this depends on different climatic regions.…”

“…The analysis showed that a depth of 30 cm was more suitable for temperate zones such as the western United States, northern Europe, southern Russia and eastern China, which could increase crop yields. In general, 35 cm was suitable for most tropical regions and parts of temperate zones such as North and South America, Europe, Africa, South Asia, and southern Australia [18].…”

“…Rationalization of tillage practices to replace conventional tillage with variable depth tillage may be a suitable alternative to achieve economic crop production and reduce damage to agroecosystems [5]. However, variable depth tillage (VDT) has so far been rarely used, and there is a general lack of experimental research results on tillage depth [18]. Although VDT has been known theoretically for many years, it can be considered a relatively new practice in terms of its practical applicability in the farmer's field.…”