GROWERS who do whole orchard recycling may need to apply nitrogen as a fertiliser at greater rates than what is normally recommended for trees in their first leaf.
Returning 26 tonnes of wood chips to the soil per hectare provides 180kg of nitrogen, 348kg of calcium, 116kg of potassium – as well as almost 30,000kg of carbon.
These nutrients will not be immediately available to the next-generation orchard, but as the woody material decomposes and soil organic matter increases, the stored nutrients will be released gradually and naturally.
While the large amounts of organic material added to the soil by WOR have many benefits, they can create an imbalance in the ratio of carbon to nitrogen in the soil, which can lower the availability of nitrogen from fertilisers in the newly planted orchard.
Brent Holtz, the University of California UCCE county director and farm adviser – and architect of the WOR concept – recommends:
· Growers apply at least 170-225mg of actual nitrogen per tree 9-20kg per hectare in the first year of tree growth following whole orchard recycling. After the first year of tree growth, growers can return to typically recommended rates of fertiliser nitrogen application.
· Nitrogen should be applied early in the season.
· Nitrogen applications should be spread out so that no more than 28 grams of actual nitrogen is applied per tree per application in the first year of tree growth.
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