Nitrogen Fixing Bacteria in Viticulture – Now a Real Option
Nitrogen Fixing Bacteria Explained
Nitrogen fixing bacteria are single celled organisms that are essentially miniature urea factories,
turning N2 gas from the atmosphere into plant available amines and ammonium via a specific and
unique enzyme they possess called nitrogenase. Although there are many bacteria in the soil that ‘cycle’ nitrogen from organic material, it is only this small group of specialized nitrogen fixing
bacteria that can ‘fix’ atmospheric nitrogen in the soil.
Most growers are familiar with legume nitrogen fixing bacteria called Rhizobium and the
colonies they form inside nodules, visible white lumps on the roots of legumes. It is well
established that specifically selected, high performance strains of these symbiotic legume bacteria can fix between 50 to 200 units of nitrogen per season, depending on soil moisture. To do this job, these specific strains need to be inoculated into the legume seed to ensure their numbers are high enough to colonize each plant and to bring about a significant influence on the total nitrogen production.
The Plant – Bacteria Communication / Feedback System
N fixing bacteria use plant carbon as a high calorie energy source to fuel the biological reaction
that converts N2 gas into plant available N compounds. Whether it be the soil dwelling species or
the endophyte N fixing species, the plant is controlling the amount of energy (plant carbon) the N
fixing bacteria receive to perform their N fixation function. As such the quantity of nitrogen
being fixed for plant use is controlled by the plant itself. For example, when there is limited soil moisture nitrogen fixation slows down, dictated by the plants diminishing nitrogen requirements and subsequent frugal supply of carbon to the bacteria. When soil conditions are optimum, nitrogen fixation is maximized by the plant’s increasing supply of carbon to the bacterial colony, in turn increasing N fixation to meet the increasing nitrogen requirements. It works like a feedback system and assures the plant receives just the right amount of nitrogen it requires based on the growing conditions at the time.
Twin N™ Inoculum – Species Selection and Freeze Drying
To date, the Twin N™ product is the only commercial N fixing Inoculum that can claim high
viability and high numbers to achieve reliability. This particular Inoculum has been developed
and manufactured to a pharmaceutical standard that guarantees a very high and very stable CFU count. Added to this, the Twin N Inoculum contains some of the world’s most researched and most highly productive nitrogen fixing bacteria species. The species selection criteria is based on quantity of nitrogen able to be fixed by the organism, the suitability to a wide variety of soil types and climates and ability to colonize all plant types.
Twin N™ in Vines – Greatly reduced requirement for liquid Nitrogen
Over the past 10 years one of South Australia’s major wine producers located in the Riverland, had trialled and now incorporated Twin N into their vineyard programmes, with tremendous success. The area applied being over 300ha.
Angoves ‘Nanya’ vineyard applies TwinN™ to both their conventional and organic blocks with no loss of yield on the conventional blocks and basically the same yields (variety to variety) organic vs conventional. The conventional vineyard has had a reduction of applied liquid nitrogen (UAN) of 40 units, down from 50 units of N to just 10. This is a reduction of 80% and contributes huge savings to production, not to mention the reduction of their carbon footprint and benefits to the environment. The organic block receives just Twin N. Both blocks receive similar amounts of compost.
Vineyard Manager Nick Bakkum says he is a ‘real fan of Twin N’, having witnessed the results for himself over the last four seasons, after a small trial in 2008/09 proved successful. “The product is very easy to apply and we have not seen any loss of yield where we have used it. We have reduced nitrogen applications considerably and both yield and quality is on par with what we are looking for. I’m very happy with Twin N’. We are using the product on a large scale now and not just a small area’, says Nick. In fact, if anyone is considering TwinN for their vineyard he would be only to happy to talk to them about the benefits Angoves has achieved with this product.
Correct application is critical to the inoculation of Twin N through plant root systems, and soil moisture is vital to the proliferation of the organisms via fertigation. Angoves applies adequate irrigation to wet the soil profile a couple of days prior to applying Twin N, where it is then washed down into the root zone upon application. Only 2 CFUs/m2 is required to inoculate the vines. The organism then gradually builds within the vascular system where complete inoculation occurs after 8-10 days. Twin N is applied only once on vines, anywhere between bud-burst and pre-flowering. Ideally, application could be made when vines are actively growing.
Considering its ease of use, reduced carbon footprint (zero, compared to synthetic applied nitrogen), the production of only ammonium nitrogen (no nitrate) and the cost (from $28-$45 /ha), Twin N is a game-changer when it comes to nitrogen application in vineyards.