Economics of lime

Press, 2 November 1984, Page 25

Economics of lime

The ability to predict and quantify the size of lime responses on pasture was a world first, and together with the ability to examine the economics of liming, made New Zealand a worldleader in the efficient use of lime on pastures, according to the S.A.L.T. team. The team said the most important result to come from project S.A.L.T. was the finding that pasture production responses in liming were related to soil pH and that these relationships were the same for all soils in New Zealand, except peats. Project S.A.L.T. found that if soil pH was 5.0, then it could be expected that a single application of lime at 1.25 tonnes a hectare would increase annual pasture production by 8 per cent. If 2.5 tonnes a hectare were applied, the increase would be 10 per cent and a 12 per cent increase could be ex■MMMMMWnnK

pected from an application of five tonnes a hectare.

At pH 5.4 for example, the responses were 4 per cent for an application of 1.25 tonnes a hectare, 5 per cent for 2.5 tonnes a hectare and 7 per cent for five tonnes a hectare.

The team said that at soil pH, 5.9, no further increases in production would occur through liming.

“For the first time then, we in New Zealand can predict and quantify the effects of lime on pasture production. Our inability to do so in the past has been the cause for the large amount of confusion and controversy over the use of lime in agriculture.”

The team said that lime responses were small, relative to those obtained from correcting nutrient deficiencies. This has made the scientists job of quantifying its effects more difficult.

“It also means that results from many, many trials are required to clearly establish a relationship,” the team said. “Fortunately, the M.A.F. has conducted,many trials: over the years and it is only now with computer technology that we can bring all of these results together and analyse them. This was the mission of project S.A.L.T.” The team put together a computer package which advisors could use to look at the investment return from liming. The team said that the soil pH needed to be determined to tell how much extra feed could be grown and also need to know the area to be limed, stocking rate, gross margin and the cost of lime and cartage.

All of this information, fed into the computer, could calculate the economic return on liming for an individual farm.