No-tillage: Long-term Benefits for Yield Stability in a More Variable Climate?

Abstract

No-tillage (NT) with residue retention is often suggested as an option to adapt cropping systems to drier conditions because yield in rain fed systems could benefit from increased soil water. But under wetter conditions, NT may lower yields, depending on soil and crop characteristics. In a future climate, inter-annual variability in wet and dry conditions is projected to increase in central Europe, in spite of drier mean conditions. Thus, long-term benefits of NT for yield stability remain uncertain. We addressed this question by analyzing the variability of absolute and relative yield in relation to the atmospheric water balance (P-ET0) using data from a long-term experiment near Bern (Switzerland) comparing NT and conventional plough tillage (CT) on slightly humic sandy loam soil. There was no significant difference between CT and NT in mean yield for any of the crops, but for peas and beans, c.v. (%) was clearly higher under CT. In contrast, differences in c.v. between CT and NT for winter barley, winter wheat and maize were marginal. Relative yield (Yrel=YNT/YCT) varied across years for all crops. For peas, beans and winter wheat Yrel varied in relation to P-ET0 during the period March to May. For peas and bean, Yrel was >1 when P-ET0 was negative, but showed no trend when positive, thus indicating yield improvements under NT after drier springs. In contrast, Yrel for winter wheat increased with increasing P-ET0 indicating positive effects of NT under wetter springtime conditions. During the duration of the experiment (1994-2013), inter-annual variability of P-ET0 for March-May was larger than during periods of equal length since 1900. Thus, in a future climate with more variable springtime conditions, the yield-effect of NT for each crop may be negative, positive or neutral, and in the long run NT appears to have only a marginal adaptation potential.