Part one of a four-part series looking at the value of legumes in dryland farming systems. This first story looks at the importance of maximising stock performance from spring production.
Driving spring production
They are the most important 100 days in most dryland sheep and beef farming businesses. The 100 days in spring when farmers have the opportunity to capitalise on soil moisture and maximise dry matter and livestock production before summer dry conditions kick in.
Developing systems that drive this spring production have been the focus of on-going dryland forage trials on Lincoln University’s Ashley Dene farm.
High quality pasture species
Professor Derrick Moot, who has been running the Beef + Lamb New Zealand-funded trials, says 70% of annual dry matter production and 70-80% of liveweight gain on dryland farms occur within the 100 days of spring. It means that, for lambs to reach 35kg in 100 days, they need to be growing at 300gms/day, hence the importance of having high quality pasture species that perform at that critical time.
As spring turns to summer, lambs start competing with ewes for feed – compromising the performance of both – and dry matter quality and production also start to decline.
Importance of nitrogen
The trials have focused on early-season nitrogen-fixing legumes and legume-grass mixes, recognising that nitrogen (N) determines a pasture’s ability to use soil water efficiently.
Derrick says all grass-dominant dryland pasture is nitrogen deficient and farmers need to find ways of increasing their N component by using either urea or legumes – and legumes are the most economically, environmentally and socially sustainable option.
The advantage of lucerne
The soils on Ashley Dene are extremely light and stony, with limited water holding capacity. Despite this, lucerne has been the most productive species in the trials. But, on Ashley Dene’s soils, it only grows two to three weeks longer in spring, compared to grass.
“The real advantage with lucerne is where it is in deep soils; it can access soil moisture deep within the profile,” says Derrick.
Cocksfoot has been the most persistent grass in the trials and, when sown with an appropriate clover, the nitrogen-hungry cocksfoot is productive, persistent and palatable.
In long-term trials on deeper Templeton soils at the Lincoln University campus, lucerne was by far the best performer, followed by cocksfoot and subterranean clover. Ryegrass and clover plots were the poorest performing, with the ryegrass disappearing at a rate of 10% per year, possibly due to grass grub.