A non-destructive method for estimating lucerne shoot weights

Estimates of leaf and internode weight, leaf appearance rate and shoot number are not appropriate for non-destructive determinations of lucerne ( Medicago sativa ) growth rates as they are too variable. In an experiment involving four cultivars of lucerne harvested on two dates, a good relationship was found between linear measurements and the dry weight of shoots. An equation of the form W^1/3= a.(dl*d2*length)^1/3, where W = dry weight; dl, d2 = two diameters of the basal end of the shoot; length = maximum length of the shoot; and a = constant, gave a good fit to the data. The value of a varied between cultivars and sampling dates, and in the proportion of shoot harvested. The product of estimated shoot weight and shoot number can be used to give an estimate of plot yield.