With annual Grasscheck grass growth up 21% compared with the 2007 – 2015 long term average, 2016 at first glance appears to have been an excellent year for grass production. But a closer look at both grass growth and quality highlights an incredibly volatile season and shows what a challenging year it has been for managing grass across the Province.

 

As in previous years AgriSearch’s GrassCheck project, conducted by the Agri-Food and Biosciences Institute (AFBI) and supported by CAFRE and DAERA has been monitoring grass trends throughout the season. Grass growth rates and grass quality have been measured weekly at four sites across Hillsborough and Greenmount. Debbie McConnell and Scott Laidlaw from AFBI and Stephen Gilkinson from CAFRE discuss the 2016 season.

 

Grass growth

 

Average annual yield of grass dry matter production across the four GrassCheck sites was 13.6 tonnes dry matter per hectare (t DM/ha), an increase of 0.5t DM/ha from 2015 and 2.4t DM/ha greater than the long term GrassCheck average (2007 – 2015). However, 2016 certainly proved an atypical season with wide variability in grass growth rates (Figure 1).

 

Figure 1: Measured daily grass growth rates for 2016 and average daily grass growth rates 2007 - 2015 from plots at Greenmount and Hillsborough
Figure 1: Measured daily grass growth rates for 2016 and average daily grass growth rates 2007 - 2015 from plots at Greenmount and Hillsborough

Growing conditions in early spring were poor, with cold and particularly wet conditions experienced in February and April across Northern Ireland. By the end of April rainfall totals were 20% higher than average for this time of year. Soils failed to dry out through the short dry spell in March, and a total deficit of 1 t DM/ha was evident after the first 12 weeks of the season compared to the long term average.

 

Following this, grass growth conditions were volatile from mid-May to the end of July, making grass management extremely challenging. The late spring meant that although May was warmer than average, grasses entered their annual reproductive phase much later than normal. This delayed ear emergence by about 3 weeks resulting in a very high but delayed spring peak.

 

Daily growth rates peaked at 115kg DM/ha/day on 23 May before falling steeply to 67kg DM/ha/day, three weeks later. This made managing grass quality and covers extremely difficult with a glut of grass on the platform resulting in high farm covers.

 

Although volatile, grass growth rates remained very strong through the summer months averaging 80kg DM/ha/d at the Hillsborough and Greenmount sites. The typical check in soil moisture usually evident at this time of year did not appear in the east of the Province and grass growth was high over the summer months totalling 7.3t DM/ha from June to August (Figure 2).

 

Figure 2: Seasonal grass yields for 2016 and 2007 - 2015 measured at Greenmount and Hillsborough
Figure 2: Seasonal grass yields for 2016 and 2007 - 2015 measured at Greenmount and Hillsborough

However, it was a tale of two halves during the summer months with the west of the Province experiencing hugely challenging grass management conditions. Data from Omagh shows an extra 315 mm of rainfall fell during the period from June to September compared with the Hillsborough site (Figure 3). This is equivalent to an extra 3.15 million litres of water falling on each hectare of land during this time, driving soil moisture levels up significantly. This made both grazing and silage harvesting extremely difficult if not impossible for many farmers in the west of the Province.

 

Figure 3: Monthly rainfall totals measured during April to September 2016 at Omagh and Hillsborough (Omagh data courtesy of K Alcorn)
Figure 3: Monthly rainfall totals measured during April to September 2016 at Omagh and Hillsborough (Omagh data courtesy of K Alcorn)

Good grass conditions eventually returned to most of NI during autumn with growth rates averaging 42.9kg DM/ha/day for September and October, double that expected for this time of year. Following some difficult grazing conditions in September, October brought a welcome dry spell (monthly rainfall totals were only 43% of expected) providing excellent conditions to utilise any late season grass and reduce winter feed costs by extending the grazing season. Low soil moisture levels also provided a great opportunity to hit target final round residuals and to set up the grazing platform for next season.

 

Grass quality

 

Figure 4: Measured grass dry matter and metabolisable energy content for the 2016 growing season at Greenmount and Hillsborough compared with the 2007 – 2015 long term average
Figure 4: Measured grass dry matter and metabolisable energy content for the 2016 growing season at Greenmount and Hillsborough compared with the 2007 – 2015 long term average

Over the season grass metabolisable energy content, crude protein and acid digestible fibre remained on trend with previous years averaging 11.6 MJ/kg DM, 19.5% and 27.5%, respectively (Figure 4). Grass dry matter contents, however, presented much more of a challenge this summer, dropping below 14% throughout June, July and August, increasing the requirement for bought-in feeds to provide sufficient energy to livestock. On average, grass dry matter content was 1.5% lower throughout the season than the long term average (17.2%).