Tillage practices affect soil fertility of a long-term winter wheat–fallow rotation

The contribution of tillage practices to enhancing soil fertility levels is a major subject of research among agricultural scholars. The objective of this study was to assess the effect of several decades of tillage under winter wheat (Triticum aestivum L.)–fallow on soil fertility. The experiment was established in 1970 as a randomized complete block design with three replications. Treatments included moldboard plow (MP), stubble mulch (SM), no-till (NT), and native sod. Soil samples were collected from 0–10 and 10–20 cm in 2010 and 2011 and analyzed for several variables including soil organic matter (SOM), total nitrogen (TN), and soil pH. Benchmarks for these variables used to evaluate temporal changes for each treatment were obtained from previous documents containing data that were sampled in 1982 and 1984 from the same site. In 2010–2011, SOM, TN, and pH were all influenced by the tillage practices at 0–10 cm (p ≤ 0.05). For SOM, the magnitude of the difference between native sod and NT in 1986 was 28% (10.1 g·kg⁻¹) and this increased to 30.6% (18.5 g·kg⁻¹) in 2010–2011 with native sod storing more SOM. Over time, NT sustained a high level of SOM with 7.7 g·kg⁻¹ more SOM than the initial 38.3 g·kg⁻¹ reported in 1986. TN with NT was greater than SM and MP by 56%, but 53% lower than TN with native sods. In general, soil fertility and nutrient availability at this site supported crop production for over 50 years without fertilizer application.