Conservation tillage effects on European crop yields: A meta-analysis

Abstract

Across Europe, many studies have investigated conservation tillage techniques, which are generally implemented as means of erosion control. Farmers are reluctant in shifting from their traditional tillage/conventional tillage (CT) methods to conservation tillage, their motive being driven by economic reasons stemming from higher crop yields under CT. While, no-till (NT), reduced tillage and minimum tillage have been widely covered by studies across Europe, little is done on ridge (RT) and strip tillage (ST) which might be a compromise between CT and NT. Thus, this study was set out to assess the impact of RT and ST on crop yields within Europe in comparison with NT and CT. The hypothesis tested was that unlike NT, RT and ST significantly increases European crop yields. This was tested by conducting a meta-analysis of 128 studies, based on 624 crop yield observations from 21 European countries. We analysed the influence of crop rotation, crop type, texture, climate, tillage depth, residue retention, and duration of experimentation on the relative yield (response ratio), i.e., yield under NT/RT/ST over yield under CT. In assessing RT and ST, ridge height and strip tilled depth were added. The results show that, on average, NT within Europe resulted in 5.1% reduction in crop yields while RT and ST each led to a 5% increase in crop yield over CT. The major moderator responsible for the increase in yields are ridge heights of at least 20 cm and, loam soil texture on ridges, and strips with tillage depth of 8 cm and a loamy sand texture on strips. Grain maize was the most negatively affected crop type under all conservation tillage techniques with yield reductions of 8% under NT and 18% under RT, except under ST where it showed a 7% increase.