Grassland Blog February 2023

As the daylight hours are now quickly increasing and with little rain in the last two weeks as well as a few frosts in Southern England, there is a temptation to apply nitrogen fertiliser as soil conditions are favourable for machinery travel.

However, AHDB states that grass growth starts when soil at a depth of 10cm reaches 5 degrees Celsius for 5 consecutive days. Therefore, N fertiliser should be applied when the soil has reached these temperatures, as until this point the organic matter hasn’t started to mineralise consequently releasing N into the soil solution and soil microbes within the N cycle are yet to become active.

Take precautions when applying N fertiliser onto cold soils. For example, monitor the weather forecast, as if rain falls onto a hard frozen surface, the N fertiliser granules can be washed straight out of the field, posing an environmental risk, and reducing the amount of N available for grass uptake.

RB209 section 2, estimates on average 6%DM cattle slurry contains 0.7kg SO₃/m3. When applied in the spring, 45% of the 0.7kg SO₃/m³ is available for grass uptake. When applying slurry at 34 m³/ha, 10.6kg/ha SO₃ is available for grass uptake.

For grazing grass, RB209 recommends an application of 20-30kg SO₃/ha when applying 100kg N/ha and 40kg/ha for each silage cut. Therefore, often in grassland nutrient management, there is a shortfall in supply of sulphur.

Polysulphate – a unique, multi-nutrient fertiliser containing 48% sulphur,14% potassium, 17% calcium and 6% magnesium, can provide a slow release of SO₃ for 50 days. Polysulphate can be applied as a straight or combined into a Nutri-Match prescription blend.

It is also important to consider the inclusion of sodium (Na) within an early application of N and SO₃, as most of it within the soil will have been leached due to rain over the winter.

Origin’s Sweetgrass range contains sodium, which increases grass palatability, causing an increased DM uptake and tighter grazing.

Want to know more about improving grass nutrition? Get in touch with your local Origin Nutrition Agronomist: Meet the Team – Origin Fertilisers