Aspects of the productivity of forage legumes in Northern Europe

A database on the productivity of red clover (Trifolium pratense), white clover (Trifolium repens), lucerne (Medicago sativa), lotus (Lotus corniculatus) and galega (Galega orientalis) was compiled. It contains 1852 observations for 330 trials at fifty-three sites in eight north European countries for the period from 1977 to 1997. The database includes information on climatic and site characteristics, as well as agronomic data, collated into four smaller data sets. This has permitted four key agronomic issues to be examined, namely: (i) how yield for a given variety varies under different environmental conditions; (ii) how the relative performance of different species varies between sites; (iii) how persistence varies between species and sites; and (iv) what the nature of the relationship is between varieties, yield and sites within a species? Cluster analysis revealed that geographical location had a fairly strong influence on yield. Across sites for an individual variety, the cumulative day-degrees during the regrowth period had the highest correlation with total yield. In terms of the relative performance of different forage legume species across sites, red clover and lucerne were estimated to yield about 2.5 t DM ha(-1) more than white clover and there was a significant impact of cumulative day-degrees during regrowth and the age of ley on the total yield. It was found that red clover had the lowest persistence index and lucerne the highest. As regards the interaction between yield, varieties and sites, the length of growth period and the age of the ley explained two-thirds of the variation in total yield in red clover varieties of contrasting maturity types.