PASTURE HEALTH CHECK SHOULD PRECEDE SPRING RESEEDING DECISIONS - 8/2/2010
Winter may be the period when grassland is largely free from stock, but with a reseeding opportunity just a few months away and recent weeks hitting swards harder than for some time now is as good a time as any for farmers to assess the value of swards on the farm.
So advises Helen Mathieu of British Seed Houses, who says that the relative performances of different leys over the last season, in terms of yield and forage quality, will be key indicators, as will the impact of more recent events such as poaching damage in the autumn and/or winter kill during the recent freeze.
In order to maximise milk and meat production from home grown forage, the aim should be to continually upgrade the productivity of grassland on the farm with the introduction of the best modern varieties, she stresses, and most advantage will be gained by replacing the poorest leys first.
“There are telltale signs that can help in the ranking of different fields,” points out Helen Mathieu.
“It is not always possible to pick up steadily declining stocking rates or falling silage yields, as the trend may be gradual, but the increasing presence of weeds – such as chickweed, cleavers, docks and thistles – or the presence of unproductive grass species, for example, provide a clear indication of a sward’s deterioration. There will be evidence of weed ingress even in winter, so visual checks can be made.
“In particular, check for the red stem base of perennial ryegrass, because most weed grasses do not have this characteristic.
“Other possible signs include sluggish regrowth after a silage cut or grazing rotation, poor response to applied fertiliser, declining milk yields when cows are moved, or an intermittent growth profile through the season. Declining D-value in silage is another sign of a deteriorating sward. It is worth consulting records or recalling relative performances of fields if possible, as it will be too late to remedy by the time it happens again.”
Factors that accelerate the deterioration of leys include over-grazing (and under grazing), poaching, and winterkill.
The relatively mild autumn may have led to a lot of farms going into the winter with extensive grass cover, thereby increasing the risk of winterkill.
“This winter has been one of the coldest for several decades, so the risk of frost damage to pastures has been greater than for some time,” she continues.
“Swards with a cover of 1500 kgDM/ha (roughly 5cm growth) or more can suffer from winter damage caused by low light levels and disease in the bottom of the sward. When temperatures fall below zero for a period of time, grass tillers (and stolons in the case of clover) will die away. Whether it is caused by swards being left too long or cold winter weather, sward death in winter will lead to the ingress of weed grasses, which will impair the performance of the ley in the following spring with slower growth followed by lower yields of poor quality forage.
“In both the case of poaching damage and potential winterkill, swards should be assessed on the basis of events over the autumn and winter. Damage from these sources may be as important as an indicator of deterioration as past performance and other visible evidence.”
|
