Nearing the latter half of May, grass plants begin to increase their stem proportion as the seed head makes its way up the plant.
It is important that we monitor the proportion of stem in the sward as this will dictate how soon it needs to be grazed.
E.g. a cover of 1100kgs/ha that has a high level of stem (owing to stress/N or K deficiency) will need to be grazed before a paddock with a cover of 1500kgs/ha with little stem. Through early grazing, we can achieve low residuals and maintain sward quality.
Paddocks that are deficient in any of the major nutrients will express higher stem content, owing to stress. Apply Nitrogen soon after grazing, or just before grazing to maximise N availability post grazing, thereby reducing plant stress. If we calculate what rotation length we are on, (target 18-21 days) this will indicate the level of fert that needs to be applied. Typically 25-30 units of N max is required if paddocks are on a 21 day round – higher levels will result in nitrogen wastage.
To calculate rotation length, divide the cover/lu by demand per cow and then multiply by 2.
E.g. 180kgs / 17kg grass per cow = 10.5 (x 2) = 21 day rotation.
As night time temperatures are fairly consistent at 8-10 degrees and growth rates above 80kgs/ha/day, spraying off the poorest performing paddocks and reseeding now should be a priority. The area taken out will be determined by stocking rates on the grazing platform. The recommended grass variety list contains quality and tonnage information on each variety – Heavier type soils will require a higher diploid content. A maximum of three varieties should be used, although some companies have 10 varieties in some mixes!
Cow body condition is excellent on most farms with cows displaying strong heats, simplifying heat detection. Monitor late calvers/high production cows closely as they are more likely to have a silent heat initially – using a beef straw is advisable if you are doubtful – better to do this than risk missing a heat. As spring calving herds are now peaking production and autumn herds are trying to maintain yield, investing extra time in grass management now is key to maximising profits per hectare this year. Enjoy the sunshine!
Cathal McAleer is a grassland consultant working with individual farmers and facilitating discussion groups throughout Ireland.
087 160 2491 / 0044 7749 531679 [email protected]