Grain Yields of Perennial Grain Crops in Pure and Mixed Stands

Perennial grain crops were examined in pure stands and in various mixtures for their grain yield potential in, and suitability for, low-input systems on marginal land. The investigation was based on field experiments conducted at two sites characterized by marginal environmental conditions in south-west Germany in 1999 and 2000. The experiments included perennial species of rye (Secale cereale x Secale montanum), intermediate wheatgrass (Thinopyrum intermedium), lupin (Lupinus polyphyllus) and linseed (Linum perenne). In some stands, white clover (Trifolium repens) was included as an undersown intercrop for improved N supply. It was found that maturation of the species differed by up to almost 6 weeks, and consequently the threshability of most mixed stands was not satisfactory. Nevertheless, mixtures of either of the grasses (rye or wheatgrass) with lupin or undersown clover proved to be more suitable than pure stands in most cases, for measures such as grain yield, weed suppression and stability of grain yield over years. The grain yield harvested in the experiments in 1999 was low, reaching about 2.7 t ha -1 with rye, and decreased for most species in 2000. If improved genotypes were available, perennial grain crops could provide an alternative for arable cropping and set-aside areas under marginal conditions.