Effects of Tree-Stripes on Crop Growth in Agroforestry Systems using UAS-based Analysis

Agroforestry systems (AFS) are an effective solution for addressing environmental challenges while meeting rising food demands. However, the complex interplay of factors makes research challenging, particularly in understanding the impact on crop yields. This study uses multispectral unmanned aerial system (UAS) data to investigate a maize-cultivated alley cropping system in eastern Germany. We derived the growth parameters NDVI and plant height as yield proxies and analysed them as a function of distance to the trees. Furthermore, we examined whether fluctuations in the field could be attributed to the trees using a direction-dependent regression analysis. The results showed to separate between two effects: First, a clear increase in NDVI appeared at a close distance from the trees, which is dependent on tree height. This is schematically shown for two tree-stripes. Second, at greater distances, fluctuations in the NDVI appear to be caused by the trees, but without any discernible systematic trends. There also seems to be considerable inconsistency in the variations in plant height. The discussion addresses the potential reasons for the close-range NDVI increase and the suitability of UASs to investigate AFS. The relationship between NDVI and maize yield is also addressed. It is concluded that the effects of the trees on crop growth and vitality are present, but rather marginal to clearly affect maize yields in the given location.