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Aug 18, 2016

Managing Grassland in areas of High Rainfall

Parts of the UK and especially Scotland and Ireland are traditionally areas of high rainfall, however other parts of the UK are now experiencing higher rainfall than before and farms are losing quality grazing ground at an alarming rate, with rushes and buttercups taking over meadows and clover, particularly red, being lost to the sward.

Waterlogging of soils produces anaerobic conditions which result in substantial leaching of nutrients, particularly nitrates, and phosphates if the concentration is high enough. Well drained soils that repeatedly flood are most at risk and heavily grazed soils will suffer compaction and poaching, exacerbating grass loss and onset of weeds. Declining production and grass yields affect stocking levels and most importantly, income. It is important to note that Environment Agencies take the leaching of nutrients to the rivers seriously (rightly so, as high levels of nitrate and phosphate in the water are hazardous to all forms of life) and legislation is in place to ensure that nitrates are not over-used. In Ireland there is now legislation curbing the use of phosphate fertilisers.

Soils should be tested regularly to monitor changes in pH, all major nutrients (P, K, Mg, Ca) and key trace elements (Cu, Zn, Mn, B, Co etc.). Unfortunately, it is often the case that this is not done until a problem is evident – an acidic soil is easily identified by the proliferation of rushes and buttercups.

From a physical point of view ditches should always be kept clear. Drainage will help, where possible, but is not always financially viable and the cessation of river dredging has led to problems for low-lying farms. Sub-soiling may be necessary to break up any hard pans, or “spiking” to improve surface aeration and reduce the effects of poaching. While harrowing is desirable to pull up old grass, rolling should be regulated to avoid further compaction.

The effects of poor quality grassland are reflected, most crucially, in livestock health, welfare and reduced stocking levels. Where there are problems in fields, herbage analysis will show low levels of macronutrients and trace elements, which are essential for quality grass and crops as well as stock health. Copper, in particular, is a key trace element for animal health and fertility and it is far better for animals to take up these nutrients in their main diet rather than by supplementing with expensive mineral blocks. Research shows that sodium, when added to fertiliser, is critical in the management of grassland. Despite being required, it is rarely a constituent of fertiliser because it is fed as a supplement.

Sodium improves grass growth and improves leaf palatability; it also increases the availability of phosphates from the soil (growth of plants is restricted at all stages if phosphate is deficient) with a beneficial effect on livestock fertility. Sodium is essential for the function of rumen bacteria, maintaining the pH in the saliva and thereby increasing live weight gain. The condition and health of the coat is improved and milk yields are increased, milk quality improved and veterinary costs are reduced, while it is an inexpensive addition to fertiliser. Liming may be required, but farmers should always look to re-balancing the nutrient status of the soil by tailor-making any fertiliser application to suit both plant and livestock needs. Generic applications are not always cost-effective and frequently result in an imbalance in important plant nutrients.

Unfortunately, we are now seeing soils that have negligible amounts of some, if not all major nutrients, and this is being reflected in reduced fertility, poor livestock health, poor yields and sadly, some farmers who are in a precarious financial position. It does not need to be this way: a small an annual investment in fertiliser will have significant benefits. There is no easy answer to managing grassland in these tough environmental conditions, but with careful supervision problems can be alleviated. Essential to this is regular monitoring of nutrient status and correcting deficiencies before difficulties set in and substantial cost incurred in rectifying the depleted land.

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