Crops can be grazed to fill the autumn–winter feed gap, improving animal performance and allowing pastures to be deferred.
Grazing crops can be considered a tool to manage frost and disease and therefore reduce the level of risk in a cropping system. Stock numbers and/or crop area can be increased on a farm, as there is less reliance on slow growing early pastures in a grazing crop system.
In the case of an early break, grazing can be used to retard development of early sown crops, reducing the impact of premature crop maturation. Both cereal and canola crops can be grazed before stem elongation without affecting yield.
A crop has an upright nature and substantial inter-row space prior to canopy closure. Hence, a crop with a low biomass will have much higher accessibility for grazing animals compared to pasture with a similar biomass. As a result, animals grazing crops early in the growing season are likely to achieve superior growth rates compared to those grazing pastures.
Grain yield is highly correlated with crop biomass at harvest, so if yield is key to your business, grazing strategies must allow sufficient biomass to be achieved by harvest.
This work indicates that simulated, early, hard grazing (during tillering, leaving plants at 0-5 centimetres high) has sufficient time for plant recovery generating a good total crop biomass and yield at harvest. Late, light grazing (during early jointing, leaving plants 10-15 centimetres high) will leave good residual biomass post grazing and can cope with less recovery time, still achieving good crop biomass/yield at harvest. It is important to note that any grazing that removes the developing head will affect yield dramatically.
The key actions for grazing crops are:
- ensure a weed free paddock to achieve best yield results from grazed crops
- use varieties that have good early growth rates and suit the area
- sow as early as possible with some nitrogen as well as phosphorus
- adhere to withholding periods for any crop treatments applied prior to grazing
- start grazing once the crop is anchored — use the twist and pull test to confirm anchoring
- graze at an appropriately high stocking rate to ensure even grazing, this may not always be possible
- grazing that allows the crop to grow away may result in uneven grazing, will not affect overall paddock yield
- do not graze past the white line in cereals — leaving some leaf will improve recovery
- to minimise yield loss, do not graze once the stem elongation process commences in cereals (growth stage 30) or after bud formation in canola, however seasonal circumstances may require or allow careful grazing after this time.
Graze crops with animals that have been vaccinated against pulpy kidney and ensure gut fill prior to introduction. Roughage should be provided as lush fast growing crops are low in fibre. Provide salt and calcium (and magnesium when grazing wheat) as supplements to sheep before and during grazing cereals to minimise hypocalcaemia and grass tetany. Above all, monitor the animals and act accordingly.
The key to grazing a cereal crop is to leave more biomass behind as the time for recovery reduces. An easy way to do this is to keep an eye on the position of the developing head. Once stem elongation has commenced, as a rule, make sure you leave more than twice the length of stem above the head as the length below.