The spatial and temporal effects of paulownia intercropping - The case of northern China

We present a financial analysis and further statistical tests of the spatial and temporal effects of intercropped paulownia (Paulownia elongata) trees on crop yields. The results provide evidence that growing paulownia trees in farm fields can either increase or decrease crop production, depending on the manipulation of the tree density and rotation length. A 60-100% reduction of crop yields can result from a higher tree density and/or a later stage of the rotation, but the pattern of reduction is different for the first (wheat) and second crops (corn, bean or cotton). However, the reduction in crop yield is accompanied by gains of timber, fuel, fodder, and other goods and services. Thus, although the accumulated net returns from crops decline as tree density increases, the combined net returns of crops and trees are generally higher than those of the control, ranging from 50% to 100%.