Growth rates and relationships between weather and growth rates for lucerne (Medicago sativa L.) in Canterbury and the Rotorua-Taupo region

Abstract

Two experiments were conducted to study the weekly and seasonal growth rates of lucerne in Canterbury (Winchmore) and the Rotorua- Taupo area (Wairakei). One of the, main objectives was to measure more accurately the weekly growth rates of lucerne, rather than the rates measured from final yields under a hay type regime, and relate them to weather factors over time. Weekly growth rates of lucerne were assessed from sequential cutting over S-week periods, followed by rapid grazing. After defoliation with sheep, the sequential cutting was repeated at a new site to avoid any interaction from repeat samplings of the previously measured areas. 'Wairau' lucerne was used but after the second year of the irrigated experiment at Winchmore 'Saranac' was used. Lucerne growth curves with and without irrigation in Canterbury and without irrigation in the Rotorua-Taupo area were constructed. During periods of rapid production lucerne growth rates were linear for up to 5 weeks. Daily growth rates of up to 185 kg DM/ha were recorded on both sites. These trials suggested that ceiling yields can reach 8500 kg DM/harvest. The main determinants of the amount of lucerne available at a particular time were the time of the year and length of regrowth period. Lucerne yields can be predicted from evaporation data and age of regrowth. Keywords: lucerne, growth curves, seasonal growth rates, weather, regressions