A project undertaken at the LaTrobe University, and supervised by Dr Kim Johnson.
Soils are essential for life on Earth, supporting and feeding plants, home to billions of micro-organisms and storing huge amounts of organic carbon. Degradation of soils has direct impact on agricultural productivity and biodiversity, by limiting the ability of plants to get the nutrients they require to grow. Compaction is one of the most important issues associated with soil degradation and occurs when soil is pressed together reducing pore size, for example by heavy vehicles, continuous cropping and climatic effects. Affecting up to 30% of Australian cropping soils (Dang and Moody, 2013), compaction inhibits root penetration and water/nutrient uptake, reducing yields by approximately 25% ($850M pa), and up to 75% when combined with drought that dries and hardens soils (Gregory et al., 2007).
Deep tillage has been common practice to reduce soil compaction and uses machinery to penetrate the compacted soil and mechanically break up and shatter the soil. Although the effects are usually positive, they are often short lived and not easy to predict. Some rotation crops, such as lupins, can penetrate compacted soils and there is evidence that they can improve rooting depth, water use and yield of the following crops. This is thought to be due to the creation of ‘biopores’ by the plant roots. There have been reports of perennial grasses providing improved conditions for following crops (Elkins et al. 1977; Bell et al., 1997), potentially by having more time and opportunity to penetrate further into the soil.
Native perennial grasses are known to tolerate low nutrient, acid soils and low water conditions. There is a clear gap in knowledge of their responses to compacted soils. This project aims to determine how native grasses, including kangaroo grass, curly mitchell grass, evans wallaby grass and silky bluegrass, respond to compacted soils and investigate their use in restoration of compacted agricultural or marginal land. The expected outcomes are increased native grasses in the landscape and improved biodiversity.
The project will study the response of native grasses to a range of low to high soil strengths and measure the amount of root and shoot growth. Experiments will initially be done in controlled conditions in a glasshouse to allow better ranking of the native grasses in terms of root penetration in high strength soils. Native grasses with the best growth will then be tested in field studies and their potential in regeneration programs assessed.