Get to know your soils ahead of next season

From the extreme wet of 2023/24, to this year’s hot and dry conditions, the past two seasons have again highlighted the need to build resilience into production systems.

A healthy, well-balanced soil is central to this, as it can better cope with extremes of rainfall – wet and dry – cycle nutrients more efficiently, absorb carbon, and ultimately, support productive crops that are potentially at less  risk from stress, pests, or disease.

Find your baseline

What constitutes a ‘healthy soil’ varies for individual situations, so start by assessing your soil’s physical, chemical, and biological properties, as these determine optimum management practices, says Hutchinsons agronomist, Rob Saunders.

“Soil testing is a valuable tool for establishing a baseline of soil health and nutrition, which will also help tailor next season’s nutritional programmes. It’s particularly important for growers planning to establish a new site next spring, as any structural, pH, or nutritional issues should be addressed before planting.

“Autumn and winter are an ideal time to assess soils, as there is usually good moisture and time for remedial work and/or tailoring of fertiliser recommendations before the growing season begins, or new vines are planted.”

Rob recommends targeting any areas of poor growth for closer inspection, to see if it is due to an underlying soil issue, and also examine any parts of the vineyard or orchard that have suffered waterlogging or flooding in recent wet seasons, as this may have been exacerbated by compaction or underlying drainage issues. Look for obvious ‘quick fixes’, such as blocked ditches or outflow pipes.

While a simple visual evaluation of soil structure (VESS) and a standard phosphorus, potassium, magnesium, and pH test are starting points for soil testing, far more detailed services are available, such as Hutchinsons Healthy Soils Gold analysis, or TerraMap high-definition mapping, offering greater detail to inform more accurate decision making.

 “Comprehensive soil analysis will report on both macro and micro nutrient levels which, although used in much smaller quantities, are still vital for plant growth,” Rob says.

Other criteria, such as buffer (resting) pH, cation exchange capacity, organic matter content, and plant available water are all useful pieces of information too.

Act on results

Once baseline soil health has been established, next identify any issues that need addressing and how best to tackle them.

Soil pH, for example, influences the availability of nutrients, such as phosphorus and magnesium, which can become less available in acidic soils, while others, such as iron, zinc and manganese, may be less available in alkaline soil.

 Acidic soils can be neutralised by adding lime – which is feasible pre-planting, but in an established vineyard, contractor lime spreading kit will not fit down rows, so granulated lime – ‘Calcifert’ – is a better option, as it can be applied using a normal fertiliser spreader, Rob says. “Calcifert is best viewed as a ‘little and often’ approach; it is quicker-acting, but less sustained in its effect.”

On high-pH chalky soils, most growers apply an iron sulphate or iron chelate type product, such as solufeed Fe 6 EDDHA (5.3% o-o), in spring to address potential deficiencies, supported with foliar applications of key nutrients where required  through the growing period.

It is also important to understand the ratio of certain nutrients, something TerraMap can tell you, notes Rob. For example, the K:Mg ratio should not exceed 3:1 as excess K can inhibit Mg availability.

“Understanding your soils is key to targeting management practices and nutrient applications for the season ahead,” Rob concludes. 

Improving soil biology

Soil biology is a harder parameter to measure, but is equally important to healthy soil. Lab-based PLFA testing is one option, measuring levels of soil bacteria, fungi and protozoa, plus the quantity of microbial biomass. This should only be done when soils are warm enough, typically above 12ºC.

Five steps to help boost soil biology:

1. Minimise soil disturbance
2. Increase plant diversity
3. Maintain soil coverage, especially over winter
4. Keep living roots e.g. with overwinter cover crops, or allowing winter weed growth
5. Increase organic matter.

Biochar soil conditioner

Hutchinsons has been involved with a recent Innovate UK project looking at using biochar (silt-sized charcoal) in orchards as a stable, long-term carbon store, and effective soil conditioner.

Biochar is made by heating woody waste, such as prunings or grubbed trees, in a low oxygen atmosphere (a process known as pyrolysis).

This converts the carbon to a stable form of charcoal that is resistant to microbial degradation, locking it away for the long-term rather than losing it to the atmosphere, as would otherwise happen rapidly, when wood is burned, or slowly, when wood rots.

“This resistance to breakdown offers a route to carbon sequestration that contributes positively to the sustainability credentials of orchard production, while producing a substrate that can improve soil fertility, especially in poorer quality or degraded soils,” says Rob Saunders.

“This is not a new idea; in fact, the oldest known deposits of ‘Anthropogenic Dark Earths’ can be found in the Amazon and date as far back as 5,000 years – but it is an idea that has come around again,” he concludes.

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