With budburst upon us, it is now time to consider fertiliser inputs.
Applying nutrients to trees now will help set them up for the season ahead.
Given that some orchard regions have had considerable rainfall over the last couple of years, and that we’ve had a big crop across Australia, there is a good case for applying fertiliser to help overcome any leaching effects of the rains, and to meet the trees’ demands for sustaining good yields and meeting market specifications.
In the initial stages of budburst to early flowering, trees draw on their own nutritional reserves from last season. There is a high demand for nutrients around fruit set. (See Table 1 for a general fertiliser program.)
Budburst
At budburst the recommendation is for a complete fertiliser that has all the nutrients that a tree requires for growing the crop.
Campbells Rustica (12-5-14) is a complete compound fertiliser. For orchardists who prefer lower nitrogen and higher phosphorous fertilisers, Platnium Plus (10-11-10) is an option.
Fruit Set
Trees undergo great nutritional stress during fruit set. To meet the needs of young fruitlets, a readily available and fast–uptake form of nitrogen—such as nitrate—is preferred.
Calcium is another critical nutrient to feed trees at this growth stage. The benefits of calcium on fruit quality are well documented.
An application of calcium nitrate within the first few weeks after fruit set is the best time to affect the calcium content of apples.
Fruit development
Fruit and leaf tests are generally conducted during this period to monitor the nutritional status of trees.
Any nutritional deficiency can be identified and addressed at this stage, before it is too late.
Fertigating with a soluble complete fertiliser such as Diamond White could help meet the demands of a big crop load.
Fruit ripening
Fertiliser applied within eight weeks leading up to harvest can still help to finish off the crop—especially an application of potassium–based fertilisers.
Potassium is a macro nutrient and trees use large amounts of potassium not only for new vegetative growth but also in the fruit.
The fruit quality aspects for which potassium is involved include sugar levels, colour and fruit size. Applying potassium thio-sulphate (KTS) could assist orchardists to get the crop up to specification.
Post harvest
Applying fertiliser as soon as possible after harvest is desirable to replenish the trees nutrients.
Post harvest fertiliser can help reduce the risk of biennial bearing. It is also the best time to apply nitrogen–based fertilisers and get the benefits that nitrogen nutrition provides to the trees without any of the perceived negative impacts that are sometimes associated with nitrogen fertilisers being applied during the season.
For the table and information, see the September 2012 issue of Tree Fruit
