Intercropping potatoes in early spring in a temperate climate. 3. The influence of planting date, row width and temperature change on the potential for intercropping

The effects of planting date and row width on canopy development, intercepted radiation and yield were studied in two experiments, with the variety Wilja in 1988 and Cara in 1989. Planting dates were between mid March and early May and were combined with row widths of 0.75 and 1.25 m. Increasing the row width decreased intercepted radiation and yields in both years. Delayed planting reduced the yield of Cara, but not of Wilja. Early planting increased radiation use efficiency of Cara. It is argued that intercropping in spring without potentially reducing tuber yield might be favoured by delaying the planting of a determinate variety such as Wilja but by increasing the row width for an indeterminate variety such as Cara. Trends in mean monthly and soil 10 cm temperatures however suggest that opportunities for intercropping potatoes in the spring in a temperate climate may become more restricted.