Relationships between dry matter yield and height of rotationally grazed dryland lucerne

Abstract

Between 2009/2010 and 2014/2015 a total of 711 destructive paired samples of total dry matter yield (kg DM/ha) and lucerne height were taken from a grazed dryland lucerne monoculture experiment at Ashley Dene, Canterbury, New Zealand. These were used to develop relationships suitable for on-farm estimates of lucerne. For pre-graze yields, the variation accounted for increased from 59%, based on lucerne height alone, to 84% for the 14 Year/Season combinations. For postgrazing residual DM yields, inclusion of Year as a factor increased the R2 from 0.39 to 0.65. Pre-graze data were also grouped into spring, summer and autumn. These relationships accounted for 54-60% of the observed variation in dryland lucerne. In spring the multiplier was ~95 kg DM/cm and this dropped to ~75 kg DM/ cm for heights measured in the summer. In autumn the multiplier was ~55 kg DM/cm. Lack of stability in the relationships over time could reflect environmental conditions and changes in stand density which height measurements alone cannot account for. Keywords: alfalfa, dry matter yield estimates, height, Medicago sativa L., regression analysis