Soil moisture deficit (SMD) has increased by approximately 10mm nationwide over the last week.

Given that most places received some rain over the last seven days and that there is little or no rain forecast for the next seven days combined with a potential heatwave, I would expect that SMD will increase by a greater amount over the next seven days.

This by itself doesn’t mean much because there is a huge variation in SMD across the country. Parts of the west are still at less than 20mm while parts of the east are up over 60mm.

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An increasing SMD in the west will be a positive as it will mean more air in the soil and as a result more biological activity leading to more nutrient availability and mineralisation of nitrogen leading to higher grass growth.

Moving from west to east, SMD increases gradually with most of the country between 30mm and 40mm of a deficit.

Affected

At this level of SMD, grass growth rates should not be affected but I know there are areas within these regions that are beginning to see reductions in grass growth.

In the east, there is a large part of Carlow and Kilkenny region where SMD is up over 60mm and at that rate you would expect to see a reduction in grass growth.

The concerning thing is that given there is no rain forecast for the next 10 days and when this is combined with high temperatures we can expect to see SMD increase by 10mm to 15mm over the next week.

This would then push those dry parts of the east to almost 80mm of an SMD while the midlands and south would be over 50mm and at that rate you would expect to see a more pronounced impact on grass growth.

Average grass growth rates across most of the country are in or around 60kg/ha/day which is normal enough for the time of year.

However, grass growth rates in Carlow are down to 49kg/ha/day and based on the weather forecast, I think we can expect more and more counties to see reduced grass growth rates over the coming weeks.

In advance of this, I think the best thing farmers can do is to park up mowers and toppers as any form of mechanical cutting will slow down grass growth.

I don’t think farmers should put in supplement in advance of a dry spell because what tends to happen in a drought scenario is that grass starts to disappear.

Use it or lose it applies to grass during a dry spell, so keep grazing away as normal as opposed to trying to hold on to grass covers that are just going to wither away anyway.