Injecting Flowable Composts

The common problem of improving compacted and degraded soil in the mid-row of long established vineyards is being investigated as part of the 'Compost for Soils' project by John Crocker, Senior Research Officer at SARDI's Nuriootpa Research Centre. 'Ground-breaking' research on the injection of flowable compost to depth during deep-ripping operations will provide valuable information on this process as a potential tool for improving degraded or compacted vineyard soils.

The project is using an innovative prototype ripper developed by Dr Chris Saunders from the Agricultural Machinery Research and Design Centre at the University of South Australia. The new ripper differs significantly from conventional ripping equipment by having two oscillating tines which require less horsepower than conventional rippers to penetrate deeper into the soil profile, even under dry conditions.

Compost injection using the prototype ripper requires a two-pass operation. In the first pass, the soil profile is fractured to a depth of 550-600mm with the ripper's tines oscillating. This opens the soil, creates a loosened zone for compost injection and provides potential pathways for later root growth and moisture infiltration. On the second pass the ripper tines are fixed and a delivery tube down the back of the ripper tine allows soil injection of compost or other powdered material in a powerful air stream.

At the current 'proof of concept' stage, compost is pushed to the ripper through flexible pipes from a separate storage truck and air-blower unit. Tests conducted in November 2007 at the University of South Australia's, Mawson Lakes campus, demonstrated that the new ripper effectively created a column of organic matter from the soil surface to depth in the soil profile using a finely textured commercial organic compost product.

A vineyard trial site has now been established for the Compost for Soils project at SARDI's Nuriootpa Research Centre. Initial work at the site during December 2007 suggests that continuous, vertical bands of organic matter approximately 50mm wide could be created by the ripper system at 800mm out from the vine row, to depths of 500 to 600mm in dry, compacted vineyard soils. Ongoing performance of vines at the Nuriootpa trial site will be measured until the end of 2009. Annual yield, juice quality and growth of vines receiving soil-injected compost will be compared with vines growing in undisturbed soil, or vines that have been deep-ripped only. Persistence of organic matter within the soil profile, changes in vine root distribution and effect on soil microbial activity will be assessed towards the end of the trial period.

The prototype ripper and compost delivery system offers a powerful tool to investigate the practicality of a variety of injectable soil amendment treatments under small-scale experimental conditions, however, the compost delivery range of the prototype system is currently limited to 40m and considerable development would be required before the system could be used on a larger scale.

We'll update the website with results as they become available. For more information contact John Crocker, Senior Research Officer at SARDI  - crocker.john@saugov.sa.gov.au, or Compost for Soils Industry Development Officer Katie Webster - ecorsrch@bigpond.net.au, or Chris Saunders, Research Fellow - University of SA for information on the ripping technology, chris.saunders@unisa.edu.au.