Biofumigation is the practice of growing and incorporating selected brassica green manure crops which contain biologically active compounds for use in the management of soil borne pests and diseases in various agricultural and horticultural crops. Biofumigation also offers the opportunity to improve soil health through the addition of organic matter and readily available nutrients, which collectively help to achieve sustainable or improved crop production outcomes.
Biofumigant plants contain specific chemical compounds which are grown, pulverised and incorporated into the soil where they ultimately produce a natural biocidal effect, similar to chemical fumigation. Brassica plants are the most common choice for biofumigation, as they have been bred to contain high levels of glucosinolate compounds, along with many beneficial agronomic traits, such as rapid growth rate, good biomass production, nutrient scavenging and rapid breakdown. Researchers now state that there are over 200 different types of glucosinolates, such as sinigrin, glucobrassicin and gluconapin, with each plant variety containing differing types and quanities of glucosinolates within the stems, leaves and roots of plants.
The biofumigation process is initiated when the plants are pulverised during the mulching process. Thorough mulching effectively ruptures the plant cells, allowing the glucosinolate compounds to contact with the enzyme myrosinase. The products of this enzymatic reaction are sugars, nitrogenous compounds and various volatile biocidal compounds, most commonly known as isothiocyanates (ITC’s).
Therefore, when freshly pulverised biofumigant crops are incorporated into soil, the biocidal ITC’s released ultimately help to naturally suppress various soil borne pathogens. The ITC’s that are produced act in a similar way to metam sodium, the active ingredient in synthetic nematicides. This production and trapping of ITC’s within the root system of soils, helps to suppress a suite of soilborne diseases, nematodes and other pests and weeds.
For biofumigation to be successful, careful planning and management is required throughout every step. Selection of high quality varieties and good nutrition is essential to ensure maximum glucosinolate levels. Maceration and incorporation must also be performed correctly and within specific time frames to ensure maximum ITC release, and certain soil conditions must also be met to enhance beneficial outcomes. The following provides some key steps towards achieving a successful biofumigation crop.
- Test your soils to understand disease, nematode risk and baseline nutrition.
- With support from your agronomist, select the right biofumigant to suit your conditions and crop rotation.
- Stick to recommended sowing rates to maximise weed suppression, prevent the production of stalky plants and increase the production of glucosinolates.
- Ensure you establish your biofumigant crop within a suitable time frame to enable sufficient growth prior to maceration and incorporation, and allowing for two to three weeks post incorporation before your scheduled cash crop planting date.
- Ensure nutrition and sufficient soil moisture is available for optimum plant growth and glucosinolate production.
- Incorporate immediately following maceration, ideally within 20 minutes, in order to trap gaseous ITC’s within your soil profile.
- Avoid maceration and incorporation when soils are wet to minimise compaction.
- Where possible, time maceration and incorporation prior to forecast rainfall, or irrigate lightly, to help seal the ITC’s within the soil profile.
- Do not plant your subsequent crop within two to three weeks following incorporation.
The incorporation of biofumigants into your crop rotation also broadly supports healthy soil management, providing the same suite of benefits as do other green manure cover crops. Organic matter and soil carbon input, nutrient scavenging, surface and subsoil conditioning through diverse yet complimentary root systems, enhanced soil microbiology, improved soil structure and aggregate stability, improved nutrient and soil moisture holding capacity, reduced erosion and runoff, enhanced weed suppression, and readily available return of nutrients to the following crop. Longer term benefits through continued use can also reduce irrigation requirements, reduced reliance on synthetic herbicides, fertilisers and fumigants and ultimately improve crop vigour and yields.
Darren Long of MG Produce, fresh market potato grower located in Sheffield Tasmania, is an advocate for biofumigation, having successfully implemented a range of biofumigant crops into his cropping business. Over many years, Darren has successfully improved the health of his soil, has significantly reduced fungicide and insecticide inputs, and lowered fertiliser inputs with a measured 100% nitrogen use efficiency. Importantly, Darren has perfected the maceration of his biofumigants, producing a finely pulverised product that maximises the potential for ITC generation, and ensures incorporation is completed timely when soil conditions permit.
Through careful selection of superior seed varieties, matched with experienced agronomic advice, Serve-Ag is the leading agricultural company to provide all your biofumigation needs.