I doubt it comes as much of a surprise that, as with our arable crops, the severe weather of late has significantly delayed nitrogen applications to grassland too. While we did have a bit of a break from the constant rainfall, unfortunately the sun didn't get chance to offer much solace before the heavens opened again.
While the weather is still having a detrimental impact on fields up and down the country, forecasters are hopeful for some much-improved conditions in the coming weeks. These predicted (and highly-anticipated) warmer temperatures will provide the opportunity to get on with some much-needed field work. As we work to adapt to these conditions, which are quite out of the ordinary for this time of year, I've outlined the below application strategies for both silage and grazing grass.
First things first – hopefully some nitrogen has already been applied but remember now that the window between application and your planned cutting date will be a lot smaller and because of that it would be wise to review the latter. However, heading dates – thus digestibility – change little year-by-year so the total nitrogen for first cut may need reducing and the balance added to your applications for the second or third cut. To maintain total dry matter production for the year, any unused nitrogen must be reallocated to later cuts.
In many cases, it's likely now that the cutting interval will be below six weeks which can increase the risk of high nitrogen levels in the cut grass. To mitigate your risk, I would encourage you to have your pre-cut grass tested. Grass with over 3% nitrogen ensiles poorly, necessitating a slight delay in cutting and also the use of effective silage additives.
The table below is taken from section 3 of the Nutrient Management Guide (RB209) and gives recommendations for nitrogen to silage to target dry matter requirements.
In many situations, especially in instances where slurry or manures have not been applied, sulphur requirements need to be supplied via the fertilisers. I'm sure there will be situations where planned slurry applications have not been possible and have therefore jeopardised total sulphur availability. Silage crops respond well to sulphur, increasing dry matter yields and silage quality so it is recommended that you use a fertiliser including sulphur for the first and second cut if you can.
Grass which is to be grazed should receive nitrogen as soon as possible. If it is delayed, there is a very high risk that the limited growth to date will be consumed before swards bulk up enough to support grazing demands. Second applications should not be delayed until all fields have been grazed and to maintain grass growth, it's advisable that you start second top dressings 10-14 days before all fields have been grazed for the first time.
In cold, wet conditions such as those we've been experiencing, the dry matter intakes of dairy cows in particular can be severely reduced – even on a day-by-day basis. Should this be the case on your farm, you must make sure that adequate magnesium is available to help avoid the onset of hypomagnesaemia. You can actually reduce the risk even further by delaying potash applications to mid season on good potash-status soils.
Below are the RB209 recommendations for nitrogen grazed swards opposite target dry matter yields:
While grass does have a tremendous ability to compensate for limited early growth, this is only really the case if adequate fertilisers are applied throughout the rest of the season so it's important to be proactive.
For more information on any of the above or other grassland-related issues, please get in touch with Frontier.