Herbage production, persistence, nutritive characteristics and water use of perennial forages grown over 6 years on a Wakanui silt loam

Abstract

Herbage production, persistence, nutritive characteristics and utilisation of chicory, lucerne, and red clover swards grown under irrigated and dryland conditions were compared over a 6‐year period on a Wakanui silt loam soil in Canterbury, New Zealand. Under irrigated conditions, annual yields of lucerne (16–28 t DM/ha) were 30% greater than chicory or red clover. Lucerne yielded 17.5–21 t DM/ha under dryland conditions, which was also 30–50% greater than chicory or red clover. The yield advantage of irrigated lucerne came from greater cool season growth, with 15 kg DM/ha per day higher growth rates in September and 10–30 kg DM/ha per day higher growth rates from March to May. The yield advantage of dryland lucerne was due to higher growth rates during September (non‐limiting soil moisture) and during periods of high soil water deficit in summer. Lucerne also had superior persistence, being 94% (dryland) and 55% (irrigated) of the botanical composition of swards in the sixth year, compared with 61% (dryland) and 55% (irrigated) for chicory and 0% for red clover. All three forages had similar metabolisable energy (ME) content in utilised herbage (10.9–11.6 MJ/kg), but red clover and lucerne had higher crude protein (CP) content (25–29%) than chicory (18%). The combination of herbage nutritive characteristics with production and utilisation data showed that grazing stock consumed 30% more CP and ME annually from Lucerne than either chicory or red clover swards. Water use (WU) was measured to investigate the production differences in dryland swards. Chicory and red clover extracted water to a maximum depth of 1.9 m whereas lucerne extracted at least 50 mm per annum of water between 1.9 and 2.3 m depth (maximum depth measured), and evidence is presented to show it also extracted water below this. Comparisons of WU showed no differences in water use efficiency but revealed greater dryland production from lucerne due solely to greater soil water extraction.