More clover in sward, more N costs saved
RECENT developments in clover and grass breeding mean pastures require less fertiliser and are more persistent, according to IGER researchers.
Speaking at the Practice into Profit open day, IGER researcher Ian Rhodes told producers that there are opportunities to make substantial savings on nitrogen fertiliser by increasing the proportion of clover in swards.
"When 30% of a pastures annual yield comes from clover nitrogen contribution is substantial and can be equivalent to 150-200kg N/ha a year. Clover is also better for pasture quality, being more digestible and supplying higher levels of protein and minerals."
But producers often remain reluctant to increase clover in swards, perceiving it as being unreliable, intolerant of hard grazing and a bloat risk, said Dr Rhodes. "New varieties are addressing these issues. At IGER Aberystwyth we have a nine year ley where 25% of yield still comes from clover and 40% where no nitrogen fertiliser has been used."
Modern varieties such as AberHerald also over winter well and tolerate high applications of nitrogen fertiliser, he added. "Even with a nitrogen application of 350kg/ha clover persists at levels of 25% of the sward."
But a producer in the group expressed concern about clovers susceptibility to herbicides. "Can we breed clovers which are more resistant to sprays: Nothing kills clover as well as Doxstar."
Although possible, breeding this type of clover is fraught with political problems, said Dr Rhodes. "Although we could breed a clover resistant to herbicides, it would transfer its genes to the wild population. Developing sprays which dont kill clover is the best way forward."
Tetraploid hybrid ryegrasses complement clover well and are ideal for medium term leys, said IGER grass breeder Llinos Jones. "While Italian ryegrasses will only persist for two years, hybrids will last up to five years.
"They are particularly suitable in cutting and grazing situations, producing high quality second and third cuts, unlike Italian ryegrasses where second cuts tend to be stemmy with low digestiblity.
"Hybrids also allow extended grazing in spring and autumn and are particularly reliable in dry summers, although that hasnt been an issue this year," said Dr Jones.
Breeding in herbicide resistance would be too political, says Ian Rhodes.