Any returns from broadleaf control?
From the April 2009 edition of Agriculture Today.
Rarely do herbicide trials analyse economic return to the farming system as a result of herbicide use.
Traditionally, they have been run to look at the ability of herbicides to control weeds.
NSW DPI established a two-year trial at Tooma to measure the impact on pasture dry matter (DM) production of four herbicides commonly used on Paterson’s curse – considering the fodder value it can offer.
“In some grazing systems to lose a large proportion of total dry matter including Paterson’s curse may lead to a feed gap at a critical time,” said Tumut district agronomist, Nathan Ferguson.
“Pasture measurement in September showed that herbicides were an effective method of controlling Paterson’s curse, but it came with a sting in the tail.”
“All herbicide treatments reduced dry matter production between 32 and 42 per cent – however, the reduction in dry matter was solely of Paterson’s curse, with no significant drop in pasture production by other species.”
Careful fodder budgeting would allow a grazing system to manage this potential feed gap created by herbicides.
While pasture cuts taken again in mid October showed little difference in pasture production, the level of useful pasture species increased to 60pc as a result of herbicide application, compared to the unsprayed control.
“For an investment of about $30 a hectare, we increased the useful component of the pasture by up to two tonnes of dry matter per hectare,” Mr Ferguson said.
“The ability to capture this additional feed through a grazing system at this time of year can be difficult.
“One way to capture the maximum possible amount is to make hay or silage and with herbicide costing $15 per tonne of dry matter, it’s a cheap source of quality feed.
“Having spent money on herbicide treatments in the first year we want to see what impact they have on pasture quantity and quality in subsequent years.”
Mr Ferguson said dry matter may be lost in the year of application but there may be productivity gains in subsequent years after removing competitive weeds.
“We’ll measure the number of Paterson’s curse plants growing again this year and look at their impact on pasture production,” he said.
Contact Nathan Ferguson, Tumut, (02) 6947 4188, or Nigel Phillips, Wagga Wagga, 02) 6938 1981.
