This combination is sublime

FORTY-FIVE AND LIME might just be the magic formula when ameliorating soil compaction and acidity.

Research undertaken by a team of DPIRD soil scientists confirmed that in soils with compacted and acidic subsoil, loosening the high-strength soil to 45 cm, and then incorporating lime at that depth, effectively reduced compaction, raised soil pH and improved root access to soil water and nutrients.

This was the result of work undertaken by the scientists who conducted a trial on a sandy loam soil at Kalannie (low rainfall), with the combination of loosening and liming clearly the most effective treatment.

Loosening the soil through tillage proved a critical step in addressing subsoil constraints, as compacted soils force plant roots to grow laterally in search for water and nutrients. This increases the energy plants allocate to growing root biomass to allow for greater exploration for nutrients, such as nitrogen (N), phosphorus (P) and potassium (K), a shortage of which can limit above-ground growth and grain development.

Root growth in compacted soils is severely restricted at soil strengths above 2.5 MPa. This trial site had a soil strength of 3.5 MPa.

Loosening the soil to 45 cm without liming provided some yield benefit. However, the subsoil remained acidic, restricting the plants’ ability to effectively utilise nutrients.

To gain a stronger yield benefit, both constraints of compaction and acidity need to be addressed.

“Being able to incorporate lime to 45 cm after loosening made a huge difference,” DPIRD Principal Research Scientist Dr Gaus Azam said.

“We saw an increase in the uptake of N, P, and K by these plants that we wouldn’t have seen with loosening alone.”