Quality up but volumes down in 2023
Zespri says the challenging weather events that have dominated the 2023 growing season have contributed to a lower-than-expected crop this season.
We have also noticed increasing incidences of vine decline syndrome, which requires attention from orchard managers.
While the industry undertakes formal investigations, we suggest some immediate steps growers can take to improve fruit quality and vine health, increase fruit value and reduce production costs.
We have tracked the use of fertilisers in kiwifruit orchards and noticed widespread excessive fertiliser application. In particular, we have noticed the excessive use of potassium, nitrogen, boron and copper.
While copper is valuable when applied judiciously, overuse is of particular concern because:
1. Copper is highly toxic to plants
2. PSA is resistant to copper
3. Copper has not controlled PSA disease manifestation
Highl levels of boron can result in premature softening of fruit. High rates of potassium and nitrogen may increase kiwifruit yield but can also decrease flesh firmness. Excessive potassium locks up magnesium in the soil resulting in magnesium deficiency and potassium-induced leaf breakdown syndrome.
Unbalaned fertiliser treatments and excessive fertiliser can harm yield quality.
Our advice to manage fruit quality issues in the shrt to medium term is as follows:
- Apply fertilisers only if test results indicate a deficiency - do not aim for "high fertility" (toxic levels).
- Carry out leaf tests. Do not apply foliar feeds unless the test shows a deficiency. Check the contents of foliar feeds; some products may contain high levels of micro and macronutrients.
- Stop using copper after bud burst. Instead, apply humates to lock up copper in the soil.
- Foliar nitrogen application should be stopped unless you have evidence of need/benefit.
- Stop using potassium until soil levels drop into the desired range.
- Use the Agrizest/Primazest programme. In orchards with high soil potassium levels, combine magnesium sulphate with the Agrizest/Primazest programme. This will improve fruit quality and reduce stress from salinity, the severity of leaf breakdown and premature leaf fall.
- Bear in mind that nutrients interact. By applying too much of one nutrient, other nutrients may become less available, causing a deficiency (see Mulder's Chart).
The Primazest/Agrizest programme will assist in reducing abiotic and biotic stress and allow the vines to be healthier and more productive.
In the long term, standard fertiliser levels may need to be investigated and adjusted to suit current varieties, industry practices and soil health. If you are unsure, please seek independent advice.
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