Orkney Soil & Nutrient Network: Final meeting – event summary

Improving grassland yields to increase profitability was the theme for the final event at Midgarth.

The event began with a recap of the two-year project at Midgarth, highlighting the importance of an effective liming schedule with regular soil testing, knowing your soil structure and giving full consideration to what exactly is expected from a grass ley before choosing a seed mix to ensure that you can get the maximum benefit from the investment.

The importance of soil organic matter (SOM) was the next topic to be discussed.  The ‘Loss on Ignition’ (LoI) test is often used by the soil analysis labs to determine the organic matter within a soil sample.  It consists of the sample being heated to a set temperature for a set amount of time, after which the resulting mass loss can be equated to a measure of soil organic matter.  The results of the tests carried out on samples from Midgarth were discussed within the group.  Managing and improving soil organic matter can have multiple benefits for the farm, not least because it ensures that the soil is more biologically active which can aid soil structure resilience.  This, in turn, can improve the water carrying capacity of the soil, preventing flooding and waterlogging in periods of high rainfall, whilst ensuring there is a buffer for crops during periods of prolonged dry weather.

The table below shows that the soil organic matter in the sampled fields at Midgarth were all within the target range.

Midgarth Soil Organic Matter

Maintaining a healthy soil organic matter involves replenishing the soils with slurry and/or farmyard manures or composts, reducing the amount of disturbance through reduced tillage where possible and considering the amount of chemical applied to crops – the chemical residues left on the soil surface can alter the way in which soil microbes can break down any applied organic matter.   At Midgarth, the results showed that understandably, the permanent grazing field which endured the lowest offtakes; pesticide applications and cultivations had the highest organic matter level. The spring barley field with its exposure to annual ploughing, power harrowing and pesticides had the lowest SOM.  We have more information about SOM in the SRUC Technical Note TN650 available to download from the links at the bottom of this page.

Sulphur was the next topic of discussion during the event.  Sulphur is an important component of all plants as it is a constituent of some amino acids which are the building blocks of protein.  Sulphur deficiency in agriculture has increased in recent years with the demise of heavy industry and the resultant drop in atmospheric pollution.  Deficiency symptoms are very similar to those associated with lack of Nitrogen i.e. yellowing of foliage, however, sulphur tends to affect young leaves as opposed to old.
Sulphur can be measured in both the soil and in fresh plant material.  Samples of herbage should ideally be taken 10 days before the grass is cut.  The grass tissue analysis result from Midgarth measured 0.15% total S in the dry matter which was less than the recommended 0.25%.  After consideration of the amount of organic manure applied to the farm in the form of FYM, slurry and bagged fertiliser, it is unlikely that Sulphur deficiency should be a problem at Midgarth.  Find out more about Sulphur recommendations for crops in Technical Note TN685 available to download from the links at the bottom of this page.

Our guest speaker during this event was Poppy Frater, a grassland specialist with SAC Consulting, St. Boswell office.  Poppy’s session during the meeting focused on the merits of paddock grazing systems and how they can lead to enhanced grass crop productivity and savings in feed costs.  Managing livestock’s intakes is more easily achieved within a paddock grazing system as opposed to set stocking, and once the infrastructure is in place, grass management can easily allow for changes to rotation speed to match grass growth patterns.  A key message from Poppy was to ensure that grass is not eaten too short.  This ensures that the plant has adequate reserves to regrow.  Grazing grass at its 6-8 cm (2.5 – 3″) sweet spot to ensure optimal utilisation of its energy and protein was also highlighted.