Dry, pasture feed levels are declining and livestock are increasingly chasing declining feed supplies.
A common scenario and one that frequently leads to pastures grazed to the ground.
Unfortunately overgrazed pastures commonly recover far slower when rain does eventually occur with many associated adverse outcomes.
These include more water runoff (with less available for pasture growth), often greater plant number loss (especially with perennials) and much slower growth as well as less total pasture growth.
Other aspects of pasture grazing management are important, but nothing is more critical than retaining groundcover and not grazing the pasture into the dirt.
A good example was illustrated at the autumn field days held on Boggabri property “Towri” owned by George and Maree Avandano and attended by many farmers and agronomists
A week before the March field day 20 millimetres had fallen following a long dry period.
Dry pasture bulk was around two tonnes a hectare or more and the perennial grass pasture had not been grazed below five centimetres.
Pasture recovery was spectacular, around 1t/ha green-matter (measured on a dry matter basis) adding dramatically to quality as well as quantity of available feed.
Pasture plants are like miniature “solar panels” and if not allowed to develop reasonable leaf area they fail to grow anywhere near their maximum potential.
The same applies to dual purpose or forage only crops such as oats winter wheat or brassicas.
Plants ability to grow at their maximum rate is a balance between not being too high and thick when bottom leaves begin to be smothered and die off (which generally doesn’t occur until dry matter levels are about 4t/ha) and too low with insufficient leaf area.
As it was pointed out at the field days, while it is tempting to use all available feed in dry times, if it affects total annual pasture productivity so dramatically it is not wise management.
Plus having good paddock feed availability means better animal performance compared to those grazing overgrazed pastures.
Different plants respond best to different grazing management aspects like degree of rotational grazing. For example many perennial plants persist and grow best if allowed to rebuild root reserves after a grazing period. Combined with not grazing them to the ground is good management.
Lucerne, for example, can rebuild root reserves in about 42 days in the warmer part of the year if given rest after grazing.
Some perennial grasses can go from grazed to 5cm back to flowering in about 30 days in late spring summer and mid autumn.
Annual legumes respond more to ground cover and density levels (a balance between being too short and too tall and over dense) for growth rates.
It is especially important to allow aerial flowering and seeding legume species to set good levels of seed reasonably often.
Probably the most important aspect for many soils and terrains in maintaining good pasture ground cover levels is the ability to effectively capture rain when it does occur.
Low ground cover levels lead to big water losses should the rain event be other than slow and prolonged. Water is like good soil fertility critical to effective pasture growth.
On-farm feedlots, more use of dual purpose crops as opposed to straight grain ones, at least part of the business focused on flexible stock numbers (e.g. a trading arm) are all aspects to help match stocking levels to available pasture to ensure minimal ground cover.
Being able to use simple feed utilisation budgeting rules and roughly being able to measure dry matter levels also helps anticipate grazing management needs to protect ground cover.
- Next week: Science underpins definition of sustainable agriculture.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
