Impact of shade and tree root pruning on soil water content and crop yield of winter cereals in a Mediterranean alley cropping system

Pruning tree roots in alley cropping systems (ACS) could reduce underground competition and thus increase crop productivity. However, these management operations impose a stress on the trees, increase production costs and given the complexity of ACS; they may not lead to an increase in crop yield. Thus, the objective of this study was to measure the impact of root pruning in a Mediterranean ACS on soil water content and on the yield of two varieties each of barley and durum wheat. To achieve this, an experiment with three different treatments was conducted: monocrop (MC), and two 23-year-old hybrid walnut ACS, with (ACS_RP +) and without (ACS_RP-) root pruning. In each system, grain yield and yield components were measured and the microclimate and soil water content were recorded during the growing season. The ACS had lower incident radiation in the understory than MC and this radiation was unevenly distributed along the alley. Besides, ACS had lower air temperature during the day and higher at night in comparison with MC. Also, soil water content was higher in ACS than in MC. Within ACS, the soil water content was similar until the tree budburst but thereafter lower in ACS_RP-. The grain yield of both cereals was lower in ACS than in MC. Among the ACS there were no differences in grain yield or in any yield component for both cereals. From the above, it can be concluded that, under the conditions presented in the study, the root pruning increased the water available for the crops, but this did not increase crop yield. It is inferred that the main limiting factor for grain yield in the studied ACS was other than soil water.

Automated summary

Pruning tree roots in alley cropping systems can reduce underground competition and increase soil water content, but does not lead to an increase in crop yield.