• Improving grassland by taking a ‘bottom-up’ integrated approach

A series of free talks on improving grassland productivity were held in January and February 2013, with speakers from the Grassright Group.

The events, entitled ‘Bottom Up Grass Production’ were at locations in Cheshire, Cumbria, North Yorkshire and Devon, and covered the benefits of removing soil compaction to improve soil structure, ensuring optimal use of nutrients from all sources to benefit grass growth, and the factors to consider when selecting an appropriate grass seed mixture.

Hosted by local machinery dealers, with advice provided by grass-seed breeder Limagrain, fertiliser supplier GrowHow and machinery distributor OPICO, livestock farmers learnt how to maximise yields and achieve more from their grassland by taking an integrated ‘bottom-up’ approach.

Soil testing

Elaine Jewkes from GrowHow explained the importance of working from the ‘bottom-up’ when managing grassland: “Up-to-date soil tests are vital – a quarter of the farm should be tested annually. Checking soil pH and nutrient indices means that slurry spreading can be tailored accordingly and fertiliser purchases adjusted to satisfy nutrient requirements.

“Before spreading, it’s vital to work out the dry matter content of the slurry – this is where the nutrients are.”

She added: “Most slurry is still spread by splash-plate. Although an easy way of spreading, it isn’t especially accurate and has high ammonia losses. Band spreaders, trailing shoes and shallow injectors place the slurry on, or in the soil, reducing losses and improving both accuracy and the efficiency of nitrogen utilisation.”

Soil compaction

OPICO’s Neil Robinson explained: “It’s pointless spending money on fertiliser if the soil structure isn’t right. Last year’s ADAS survey of 300 fields found that 60% were suffering from compaction. Good soil structure has many benefits, encouraging good early spring growth so livestock can be turned out earlier, and allowing higher stocking rates.

“Compaction can be caused by drought, continuous rain, livestock grazing in wet conditions, overloading trailers when silage-making, and muck-spreading in wet conditions.

“Poor soil structure reduces yields and quality, and increases weed ingression, resulting in reduced grazing days and harvesting problems. In compacted ground, grass has a shallower rooting depth, reducing drought tolerance and depressing nutrient uptake. Furthermore, compaction leads to poor nutrient cycling, de-nitrification, run-off, soil erosion and water-logging.”

Neil said: “Compaction depth is best checked by digging a hole around 50cm wide and 40cm deep. Drop the resultant clod of earth onto the ground and vertical fissures should appear. In compacted ground, only horizontal fissures will be seen.

“Also look out for areas of rusty-coloured soil, smelling of iron and sulphur. This denotes iron oxidation, where compaction has starved the soil of oxygen.

“Shallow compaction caused by livestock is best remedied with a sward slitter. This works by slicing through the soil and allowing air interchange which promotes better grass growth. If slurry is applied at the same time then the nutrients can get right down to the roots.

“For compaction deeper than 25cm, as typically caused by heavy machinery, then a sward lifter will be needed. This breaks up the mineral ‘pan’ and improves drainage. It’s best carried out when the subsoil is dry enough to crack and fissure.

“But don’t be tempted to buy a sward-slitter to tackle compaction if the problem is actually deeper than 12.5cm. It might be cheaper than a sward lifter, but it won’t solve the problem and so will cost more in the long term.”

Selecting grass seed

Limagrain’s John Spence added: “The best time to assess grassland is during spring growth. First, walk all the fields and assess how much ryegrass is in the sward. As grass leys get older, the original ryegrasses sown become replaced by less productive weed grasses, and broadleaved weeds can also take hold.

“The feeding value and yield of a sward declines over time. A one-year old ley has an average metabolisable energy (ME) content of 11.5MJ/kg DM. By the time the ley is 9 years old the ME content will have dropped to around 10.1 MJ/kg DM. The cost of buying in wheat to top up the low energy levels in grass would be seven times the cost of reseeding the grass ley.

“When deciding which fields to reseed, consider where the best return on investment will be, based on soil type, past productivity and the location on farm. It won’t necessarily be the oldest ley that needs reseeding first.

“Grass seed mixtures should be chosen based on the intended length of ley and its use – grazing, cutting or both. It’s generally better to have separate silaging and grazing mixtures.

“Silage mixtures tend to be based on short-term high yielding perennial ryegrasses selected for their close heading dates. This allows prediction of when the sward will reach its maximum energy content and hence the best time to cut it. In comparison, grazing mixtures tend to contain intermediate and late heading ryegrasses which keep the sward leafy for longer.”

OPICO’s Neil Robinson concluded: “A lot of damage was done to grassland last year. Farmers should take a ‘bottom up’ approach to improving their fields by reducing compaction issues, replacing nutrient deficiencies, selecting appropriate grass-seed mixtures and keeping weeds under control.”