Soil experts say deficient Marlborough soil biology means vital microorganisms aren’t thriving
An expert’s view
Geoff Warmouth, soil health expert from a leading New Zealand bio-technology company active in the viticulture sector, believes some vineyards are very low in organic matter. He says this leads to deficient soil biology, as microorganisms rely on an organic carbon source to thrive.
Warmouth describes the ecosystem of a successful vineyard as a delicately-balanced environment of soil, air, sunlight, water and fertiliser. He says the application of compost supplies organic matter which alters the carbon to nitrogen ratio and breaks down to humus. A correct balance allows the soil to more quickly and effectively utilise fertiliser and, most importantly, the organic matter in compost promotes soil reaggregation. This enables it to hold moisture and air, preventing air gaps being filled which causes compaction and panning.
Warmouth notes that good compost, with the correct balance of fungal and bacterial microorganisms is hard to find.
“Viticulturists’ paramount aim is consistency, growth and flowering… which all comes back to consistent soil activity, consistent water-holding capacity and a consistent amount of organic matter.”
Warmouth recommends application of compost to a depth of1.5 inches, following soil ripping either side of the vine to break through any soil crusting. In terms of timing, compost application, Warmouth suggests, can occur after harvest and before bud break. He notes winter application is sometimes problematic given wet soils can produce anaerobic action in compost.
Elements of quality compost
Composts are created through the controlled microbiological transformation of organic materials under aerobic and thermophilic, or high temperature, conditions. Most compost contains a wide range of macro and micronutrients, including nitrogen, phosphorous, potassium, calcium, magnesium, boron, iron, copper, and manganese.
It is important to note that organic material that has not undergone a thorough composting process may contain weed seeds, plant pathogens and unpleasant odours. Raw manure provides unpredictable nutrient availability and its application risks nutrient leaching and excess salts in soils.
Correctly-finished compost should be a uniform colour and texture, smell neutral or earthy and have a carbon to nitrogen ratio of less than 20:1. This ratio ensures there is ample nitrogen for microbial decomposition to release into the soil. When the carbon to nitrogen ratio exceeds 30:1, microbes out-compete plants for nitrogen, resulting in plants becoming starved.
The importance of organic nitrogen
Nitrogen absorbed by plants from the breakdown of organic matter, or biological nitrogen fixation, is important because it is difficult and expensive to satisfy vineyard nitrogen requirements through industrial fertilisers alone, which are produced using fossil fuels. These ammonium-based fertilisers, such as urea, tend to acidify vineyard soils and potentially lead to groundwater pollution. The long-term protection of our environment and legacy for future generations makes compost the resourceful and sustainable choice for sourcing nitrogen.
Compost as a soil conditioner
The provision of essential nutrients is not the only beneficial impact composts have on vineyard soil. The soil-conditioning effects from the application of compost include the reduction of soil compaction, through increased organic matter, which in turn improves water retention and infiltration. This can aid vines’ resilience through dry periods. Increased organic matter also improves the buffering capacity of the soil leading to stability in pH levels.
Soil structure is altered by the application of quality compost, which can help with erosion control and improve and stabilise soil porosity. This, in turn, promotes root growth and stimulates biological activity.
Microbial activity is crucial
The application of compost boosts positive microbial activity in the soil, with increased organic matter creating a nutrient-rich habitat. A top-quality compost, importantly, is itself composed of beneficial microorganisms, which are key to its positive impact in soil management. The activities of these microorganisms stimulate plant growth and, crucially, compete with disease organisms in the soil. Studies investigating compost treatments show that these are effective at suppressing specific root and foliar pathogens to which grapes are susceptible. This reduces the need for pesticides in the vineyard.
Compost’s proven results
Studies show compost-treated vines grow well, have greener foliage, show fewer nutrient deficiencies in the leaves and suffer less from drought. They resist disease better and have a longer productive life. Some studies have documented crop yield increases from 15 to 50% and Brix and flavour improvements. Beneficially, the effects of compost are long-lasting and will remain in the soil and be evident in the vine for 5 to 7 years after the compost has been applied.
Compost- a vineyard must
Viticulturists know that the health and sustainability of the soil in their vineyards is vital for maintaining vine health and increasing grape yield. Giving back to the soil ensures productivity and longevity of vines. Both growers and researchers in the field agree that the application of compost to soil is an indispensable aspect of current vineyard management.
Soil fertility management requires balancing nutrient supply, including soil pH, with nutrient demand, from vine vigour and crop load, alongside uptake, from root growth. As well as carbon, hydrogen and oxygen, grapevines require essential mineral elements to grow and produce fruit.
Studies show that the optimum method for supplying soil, and ultimately, vines with these essential elements is the application of organic matter in the form of compost.
The resourceful and sustainable choice in composts
Here, at Wholesale Landscapes we operate under a set of core values, one of which is resourcefulness. We believe in being resourceful and making the most of what we’ve been given. That is why we utilise sustainable forestry residue and other waste bio-products to create composts that will enhance the productivity of your viticultural enterprise and protect our environment.
Wholesale Landscapes are also proud to produce quality organic matter composts that come highly recommended by viticulturalists, vineyard managers, contract growers and soil health experts alike.
Warmouth recommends Wholesale Landscapes as having ”… a very nice compost” which he has seen applied to vineyards, …”and it works’’.
Wholesale Landscapes has a wide range of composts available to incorporate into your vineyard management scheme.
Wholesale Landscapes would like to thank Geoff Warmouth of BioStart Limited for providing technical information.