Because grass remains leafy, rotation length can be extended from the 2nd week in August. The focus of this period is to gradually build pre-grazing covers, targeting covers of 3,500kg to 3,700kg DM/ha in mid-September. Be careful not allow covers build beyond 4,000kg DM/ha for grazing, as utilisation is poorer. We want to avoid taking paddocks out for silage after the start of September, as these paddocks won’t have enough time to re-grow to make a significant contribution to the last rotation.

If Autumn nitrogen is going to be spread, it should be spread in August and September. As you can see from the graph, the growth response to October applications is likely to be significantly lower and may not be economical. Our Calcium Ammonium Nitrate based fertiliser YaraBela Nutri Booster with sulphur and selenium at 120kg/ha is an appropriate rate for applications during August and into the first half of September. If P & K needs topping up, then a quality NPKS such as YaraMila EXTRA GRASS at 110 kg/ha should be used.

Drier or ‘earlier’ paddocks should be grazed from mid-September and then closed off from October onwards. Regrowth on these parts can be carried over the winter months for grazing first in the spring.

P & K top-up

Now is a good time to review fertiliser and slurry applications this season. With a particular emphasis on potash (K). Where K inputs don’t cover K offtakes, aim to top up to maintain soil K fertility. For those trying to build their soil K index on fields or paddocks, autumn is the time to apply build-up rates. For intensive grazing on soils with a K index of 2, we recommend 20kg/ha of K2O, while at index 1 we recommend 30-50kg/ha but take account of any bales removed from these paddocks during the season. You can calculate the K2O offtake per ha from bales by multiplying the number of bales taken from a paddock by 8kg (the amount of K2O in a bale weighing 900-1,000kg at 25% DM), and then dividing this figure by the size of the paddock in ha’s. This is where it can be useful to use a silage grade fertiliser like YaraMila Silage Booster with its higher potash content in this scenario.

Example: How much extra K would a 2 ha grazing paddock need above maintenance if 9 round bales of silage was removed.

Answer: 9 bales x 8kg divided by 2 = 36 kg/ha K2O

Research confirms sulphur benefits on grassland

New sulphur (S) research from Teagasc in Ireland highlights some interesting findings on S applications on grassland. Using lysimeters and a sandy loam soil they found N + S applications increased grass yields by 30%, compared to N only plots over the course of 7 cuts. Treatments received 250kg N/ha, divided over 7 splits. For the two slurry treatments, there was a 24% yield increase by using a N + S fertiliser with slurry compared to N only fertiliser with slurry.

Apparent Fertiliser Nitrogen Recovery (AFNR) which is a measure of how much of the applied N was taken up by the crop was also increased with sulphur applications. N only plots had a AFNR of 39%, compared to 49% for the N + S treatments. For the slurry treatments the addition of mineral S in the fertiliser increased the AFNR by 13%.

The leachate from the treatments amounted to 68% of total rainfall over the 12-month study. Nitrate leaching loses per ha for the N only plots was 48.2kg NO3-N, whilst the N + S treatment was 26 kg NO3-N which was only 2kg greater than the Zero N control treatment. The nitrate leaching losses for the slurry treatments were very surprising. The N + slurry treatment had losses of 82.8kg NO3-N, in contrast to the N + S + slurry treatment which had losses of 33kg NO3-N.

The study concluded that S fertilisation is potentially important for increasing grass yield, N use efficiency and reducing nitrate leaching losses on certain soils.