Abstract:

Legume-grass mixed pastures were established on slightly alkaline soil in central Inner Mongolia， China. Three different grass species （Psathyrostachys juncea， Bromus ciliatus and Elytrigia elongata） were each sown with the alfalfa cultivar Caoyuan No.3 （Medicago varia） in legume∶grass ratios of 1∶1， 1∶2 or 1∶3. These 4 species were chosen because trial plantings in the area had confirmed they are suited to the local climate. Three years after the mixtures were established， the forage yield， land equivalent ratio （LER）， relative forage yield （RY）， relative density （RD）， relative total yield （RYT）， and inter-species competition rate （CR） were evaluated for three different growth periods during the summer. It was found that the forage yield of all mixed sowing combinations was much higher than single species stands at all three harvest dates. Hence the LER of all mixed sowing combinations was greater than 1. RY， RD and RYT also exceeded 1 in most combinations， with the exception of two of the mixtures sown at the 1∶3 ratio. The competition relationship within the different mixtures was also analyzed. When alfalfa mixtures with the three grass species were established at 1∶1 and 1∶2 ratios， there was stable coexistence with benefits distributed to both species in the mixture， and the CR between legume and grass was predominantly greater than 1 （except for the alfalfa-B. ciliatus combination sown at 1∶1） and tended to increase as the proportion of grass in the mixture was increased. Considering both the productivity and stability of the pasture mixtures， an alfalfa-B. ciliatus mixture sown at a 1∶1 or 1∶3 ratio， or alfalfa-E. elongata or alfalfa-P. juncea mixtures established at 1∶1 or 1∶2 ratios were most conducive to the establishment of high-productivity and stable artificial grassland in this area.

Key words: legume-grass mixture, land equivalent ratio, relative total yield, inter-species competition rate