Competition and yield advantage in mixtures of pea (Pisum sativum L.) and oats (Avena sativa L.)

In field trials on a fertile fluvisol in 1995 and 1996 near Gottingen, Germ any, pea (Pisum sativum; cv. Messire/conventional leafed, cv, Profi/semilea fless) and oats (Avena sativa; cv. Alf) were grown as sole crops and in sub stitutive mixtures. The sole crops were established at 80 pea seeds m(-2) a nd 300 oat seeds m(-2). The mixtures consisted of 67% (pea) and 33% (oats) of the monoculture densities, respectively. Interactions of cv. Messire or cv. Profi and oats were similar in 1995 and 1996. The mixtures outyielded t he monocultures with respect to total above ground dry matter (RYT = 1.15) and grain yield (RYT = 1.09). Grain yield of pea and oats averaged 4.9 t ha (-1) in monocultures and 5.5 t ha(-1) in mixtures. Oats was relatively the stronger of the two competitors. Decreasing number of pods per plant could be highlighted as the factor for a lower pea seed frequency in the yield of the mixtures. For oats the number of panicles per plant and kernels per pa nicle were higher in the mixtures compared with the oat monocultures. The a verage amount of the harvest index (HI) was 0.52 for pea and 0.46 for oats. Favourable growth conditions increased HI values however, prolific vegetat ive growth in the mixtures resulted in lower HI values. The predicted RYT-v alues estimate the maximum combined grain yield of 6.3 t ha(-1) in the mixt ure of 87% pea (70 seeds m(-2)) and 13% oats (39 kernels m(-2)).