In light of the recent rainfall across the country, grass growth rates are expected to significantly improve in the coming days.
In light of this, dairy farmers are being advised to continue measuring grass covers every five to seven days and use that information to make decisions on how to optimise grass quality and levels of supplementary feeding on their farms, for both now and later in the season.
The College of Agriculture Food and Rural Enterprise’s (CAFRE’s) dairy technologist Robert Patterson has noted that the dry and hot weather conditions – experienced across the country during July – increased soil moisture deficits and had a significant impact on grass growth and supply on farms.
In some areas, growth rates as low as 20–30kg/dry matter (DM)/ha/day were recorded.
Patterson noted that steps now need to be taken to maximise the use of the resultant grass.
He outlined that if the average farm cover was able to be maintained at or above 2,100kg/DM/ha, with a rotation length of 25 – 30 days, the recovery time of the grazing platform should be quicker.
The correction of soil moisture levels should create a burst of grass growth. It will be important to manage this grass growth as on many farms, the grazing wedge will have flattened as a result of the drought conditions, with a lot of paddocks carrying similar lighter grass covers, according to CAFRE.
If the average cover is less than 2,100kg/DM/ha then it is important to maintain the rotation around 30 days until average cover increases.
Regardless of what the average cover is, Patterson emphasised it is critical that dairy farmers measure the grazing platform weekly, if not every five days, to allow for adjustment of the grazing rotation.
Grass growth: Forage
Feeding supplementary forage as a result of the dry spell may have had a negative impact on winter fodder supplies.
With the return of the rain it will be important to extract the additional forage in order to save it for the winter and also think about ways to replenish supplies for the winter.
Where supplementary feed was increased to compensate for grass supply, it is important to reduce and remove from the cow’s diet at the correct time.
Patterson warned that if the supplementary feed is removed from the diet too quickly, grass demand could outstrip supply and the average farm cover could drop further, meaning grass would not have a sufficient recovery time.
Patterson suggested that farmers should remove supplementary feed from the diet in a “gradual stepped approach” over the course of a week to allow cows time to transition back onto a grass diet and avoid an impact on milk production”.
Fertiliser application
Commenting on the fertiliser situation, Patterson said: “Most farms have not applied any nitrogen fertiliser now in over two weeks due to the dry weather conditions”.
He advised farmers who have applied nitrogen during the dry spell, not to apply any additional nitrogen.
“Extending the grazing season and keeping cows at grass for longer, will help to reduce the demand on potentially limited winter fodder stocks,” the CAFRE advisor explained.
“The planning to extend the grazing season and indeed, preparing the grazing platform for grazing in spring 2022 starts now,” he added.
August is a critical time for grazing management and many believe it is the beginning of the grass year.
Patterson advises that farms stocked at 3.5 LU/ha or above should build up autumn grass covers from the first week of August, and target an average cover of 2,350kg/DM/ha by mid-August and 2,600kg/DM/ha by early September.
This can be achieved through gradually increasing rotation length through August and September whereby cows entering their final rotation of the season will be on a 45-day rotation.
Grass quality may have been reduced through the dry spell and when grass supply exceeds grass demand, the opportunity should be taken to correct paddocks in the rotation.
He stressed the importance of having clean paddocks in August to start building up covers for the autumn.
Concluding, Patterson noted: “Pre-mowing and identifying poorer-quality paddocks to remove as bales if a grass surplus exists, will help to improve grass quality.”