How to maximise grass growth after a slow spring

The graph below, from the AHDB Forage for Knowledge seasonal grass growth data, shows that average grass growth for May is behind both last year’s figures and the five-year average. This causes issues with grass availability for grazing and silage yields at a time when demand from livestock is high.

We may well see a dramatic spike in growth with temperatures rising, but more variable growth is becoming increasingly common. We must adapt our management to limit the impact this has on homegrown forage production.

AHDB Forage for Knowledge - seasonal grass growth data (Image: AHDB)

For optimum growth, grass plants need adequate:

• moisture
• sunlight
• temperatures between 5 and 25°C

These are three things we cannot influence.

However, there are three things we can influence in relation to grass swards:

• adequate nutrition
• rest from grazing
• good soil structure to maximise growth

Tiller leaf production (Image: Barenbrug Grassland Management Guide)

Given current high fertiliser prices, any expenditure must always be justified. Recommendations from a qualified adviser, based on recent soil samples, will help you buy only the fertiliser you need, reducing unnecessary costs while avoiding potential yield losses in the future through insufficient nutrient supply.

Soil pH, phosphate and potassium levels are the foundations of good grassland management, and any sub-optimal levels will impact a grass sward regardless of whether nitrogen is being applied.

Potassium levels will be particularly important this year, off the back of a challenging wet autumn and winter running into a cold spring. Potassium plays a key role in nutrient uptake, plant yield, crop quality and photosynthesis.

It is required by plants to regulate the opening and closing of stomata. Low levels of potassium will slow the rate at which a plant can photosynthesise and increase water vapour losses.

Plants under stress will reduce the rate at which they photosynthesise. Therefore, if soil potassium levels are already low and a plant becomes stressed, the impact will be multiplied.

We are already at the start of June and, for those with disappointing first cuts, it is essential that we provide the optimum conditions to maximise grass production for the rest of the season.

Reviewing recent soil results and preparing an updated nutrient budget that accounts for slurry and organic manures will ensure grass has the nutrients it needs. Of course, hand in hand with soil fertility levels is soil structure. After a long, wet winter, there will be fields suffering from compaction, exacerbating the slow growth caused by weather conditions.

When soils become compacted and particles bind together, there is little space for air or for the movement of water and nutrients, which impacts grass growth. Spending some time with a spade and digging holes to assess the structure of your soil can be invaluable, allowing a plan to be put in place to remedy any compaction.

Pushing a penknife into the side of soil pits at varying depths is a quick way to determine where compaction may exist and carry out further investigations. This damage will not be repaired immediately, but addressing it will benefit grass production in the long term.

Grass plants also need sufficient rest to replenish their energy reserves. Grazing perennial ryegrass swards before they have reached the three-leaf stage will slow recovery. Consequently, grass growth slows because there is insufficient leaf area available for photosynthesis.

During spring and summer, with good growing conditions and sufficient rest, it can take as little as five days to produce a new leaf and 15 days to reach the three-leaf stage. Supplementary feeding may still be required to provide adequate nutrition to livestock if grass is in short supply. Grazing swards too early will slow grass growth over the longer term.

Preparing a feed budget early will also allow you to identify any shortfalls in winter feed production and give you time to find options to fill the gap.

While waiting for grass to grow after a late spring can be frustrating, it is important to focus on the elements you can control and prepare alternative plans. There may be no quick fixes, but getting the foundations right now can improve production in the future.

For more information about SAC Consulting livestock and grassland support services, visit www.sac.co.uk/livestock or email livestock@sac.co.uk