Lorelle Lightfoot, managing director of Aglime Australia in Perth, has been funded by the GRDC to answer some of those "awkward questions" growers pose about the practical application of lime. People like to know how long lime will last, what its effect is on the subsoil. How best to cultivate with lime and so on. Dr Lightfoot has been looking at the long-term field responses "under farmer conditions" to lime application in wheat\lupin and wheat\pasture rotations. Of 19 sites with initial topsoil pH ranging from 4.4 to 4.9. 17 sites have shown significant wheat yield increases in one or more years. Two sites have not shown yield increases. possibly due to other nutrient deficiencies.
Yield responses vary
She found yield response can be variable. Yield responses get better with time and are better immediately following a legume rather than a cereal.
Other findings: Optimum pH following liming appears 10 be 5.5 to 7.0; lupins are not as responsive to liming as wheat, subclover or medic: liming measured to increase the uptake of N. P. K. Mg. Ca. and Cu and decrease uptake of Zn and Mn. Dr Lightfoot also looked at the effects on the subsoil of topsoil-applied lime. She has good news: the lime is leaching down as far as 40 cm (maximum measured) in deep sands and to 25 cm in duplex soils over four to seven years. Most soils had lowest pH at 10 to 20 cm level.
Best results for subsoils should be achieved under long-term timing to mainlain topsoil pH at least around 5 .5.
She now has a study underway on the best methods of cultivation with lime - looking at disk versus tine and one versus two cultivations. "We're looking for improvements to firstyear responses to lime' She said.
Sold on lime
Grower Robert Bradley of 'Gloriana' , Kellerberrin in the WA central wheat belt started liming in 1989. He not only realised immediate improvements in wheat and barley yields, but also a dramatic (2 per cent) rise in wheat protein levels. The pasture legumes improved and even ihe stubble, he said, appears to be far more attractive to the sheep.
"Quite simply we're sold on it," he said of his lime program. He started out with soil tests which indicated that his soils were "a bit acid". In 1989 he put 25 tons on two paddocks and started doing the whole farm the next year.
The strategy is 10 use a 1/2 ton of lime sand to the acre in the year that paddock is to be cropped. The cost is $20 per ton to the acre, spread. Mr Bradley thinks it's a good long-term investment which shoulld last at least 5-7 years.