Lime vs gypsum on the coast

Calcium trial boosts soybean yield but more work to be done on subsoil

Cropping
Paul and Joe Fleming, in a paddock of early season soybeans at Codrington, before the big wet, Recent trials have found placing lime at depth is essential for raising crop yield in complex coastal soils.

Paul and Joe Fleming, in a paddock of early season soybeans at Codrington, before the big wet, Recent trials have found placing lime at depth is essential for raising crop yield in complex coastal soils.

Aa

A NSW DPI trial is investigating ways to improve crop production in the Richmond Valley, where magnesium rich topsoil and sodic subsoils tie up nutrients in both the wet and the dry

Aa

Heavy clay soils have provided many challenges for grain growers in the high rainfall zone of north east NSW. These soils have a high clay content and typically have a very high bulk density and a low soil permeability to water.

This creates an environment where plant roots struggle to penetrate the soil and rainfall tends not to infiltrate but rather runoff.

NSW DPI researchers identified a troublesome soil at Joe and Paul Fleming's property at Codrington near Casino. Initial soil tests indicated that the surface soil was highly magnesic explaining the poor soil structure.

Subsequent soil tests taken deeper in the soil profile indicated elevated sodium levels. Gypsum and lime were assessed in a trial to evaluate the efficacy of calcium amendments.

NSW DPI technical officer Nathan Ensbey set up a trial aiming to identify a surface-incorporated soil amendment that can ameliorate this difficult to manage soil type and thereby increase crop productivity.

The Fleming property is naturally acidic, sitting at 5.5pH, exacerbated by a history of cropping so responded very well to the liming trial which looked at 5t/ha after one application and on other plots 5t/ha every year. Treatments with lime had increased grain yields of up 0.63t/ha.

With the gypsum, applied the same way, there was no response - and mirrored the control plot.

Mr Ensbey said the yield response to lime cannot be due to a calcium effect, because there was no yield increase with the application of gypsum alone, which is also a source of calcium.

Trial plots at the Fleming brothers' farm at Codrington, via Casino.

Trial plots at the Fleming brothers' farm at Codrington, via Casino.

Therefore, the lime response is a response to increased soil pH. Sodic soils are responsive to gypsum, so hopefully in time the gypsum will move through the soil and ameliorate the sub-soil, said Mr Ensbey.

"This is a three year trial so we will might start seeing some results by then," he said.

Mr Ensbey believes future work will include options of delivering soil ameliorants into the subsoil without the need for deep cultivation.

The Fleming brothers use controlled traffic and strip-tillage techniques in their farming system. Conventional cultivation is not part of their system, so the challenge is to incorporate amendments at depth without violently disturbing the soil.

"There is research being carried out around the country on sub-surface application techniques," he said. "So we will not be trying to re-invent the wheel rather adopting what works in our environment."

Aa

From the front page

Sponsored by