Moderate shading did not affect barley yield in temperate silvoarable agroforestry systems

Abstract

With climate change and an increasing global human population, the concept of agroforestry is gaining economic and environmental interest. The practice of growing trees and crops on the same land is mainly applied in (sub)tropical climate and rarer in temperate areas where farmers fear decreased understorey crop yields due to competition with trees. However, whether competition is stronger below- (soil moisture, nutrients) or aboveground (light) in a temperate silvoarable agroforestry system (AFS) is not clear. The effects of different treatments of light, water and nutrient availability on crop production in two temperate AFS in Central Switzerland were investigated, where summer barley (Hordeum vulgare L.) was grown as understorey crop under 90%, 40% and 0% shade nets, with and without irrigation and/or fertilisation in a fully factorial design. Yield was reduced by 26% under heavy shade; yield reductions under moderate shade were not significant. Fertilisation and irrigation increased crop yield by 13% and 6–9%, respectively, independent from shade. Individual seed mass was significantly increased by fertilisation from an average of 0.041 g (± 0.008 SD) in unfertilised treatments to an average of 0.048 g (± 0.010) in fertilised treatments. Fertilisation had the biggest impact on total seed number (p < 0.001) with on average 36 (± 26) seeds per individual in unfertilised plots and 61 (± 33) in fertilised plots. This study demonstrates that moderate shade (as can be expected in modern AFS) was not a major limiting factor for barley yield in these two AFS in Switzerland, indicating that AFS with appropriate management combined with suitable selection of understorey crops are an option for agricultural production in temperate regions without significant yield losses.