Nutrient Management Research Database

Modified N application to GOLD kiwifruit alters not only the fruit and leaf N concentrations throughout the season and at final harvest but also alters the concentration of other macronutrients in fruit and leaves. Fruit concentrations of N were most significantly reduced in fruit when compared to leaves under the Zero and Control treatments when compared to high N vines. Similarly fruit Ca levels were more elevated than leaf Ca in fruit from the Zero vines although both fruit and Ca concentrations tended to be enhanced under reduced N application in both years. IN contrast fruit K levels were not modified depending on N application. K is an important macronutrient in kiwifruit and is accumulated in large amounts in the fruit. Potassium is readily available within the soil profile and uptake is not limited by high N applications as may be the case for other applications. No difference between treatments in the incidence of low temperature breakdown of fruit in storage in year 2 was recorded. This may be related to the over lower levels of fruit N recorded in all treatment in year 2 and corresponds to slight more mature fruit. It may be that fruit N content above some predetermined levels will induce low temperature breakdown but that this level of fruit N was not recorded in any treatments in year 2. 

The observed changes in fruit mineral content under modified N application may indicate a better storage potential for fruit produced under a low N regime on fruit storage quality is not only due to changes in fruit N content. However, we expect that the Zero N treatment will result in yield reduction if continued long term. This study does not indicate potential to reduce N application to GOLD kiwifruit growing in the Te Puke region and that this may enhance fruit mineral accumulation of other important macronutrients.

This two year study investigated the sustainable use of nitrogen on kiwifruit (Hort16A) yield and fruit quality.

Three N treatments were tested: 0, 130, and 260 lbs N/ac.

The potential effects of varying N rates on uptake of calcium, potassium, phosphorus, sulfur, and magnesium.

In year 1, K, Mg, Ca, S, and P were applied in early August. Nitrogen was applied at bud break in late August in both years.

 Fruit Quality and Yield

While fruit size was not reduced by the no N rate in year 1, but by year 2 fruit size was reduced without N application. Fruit in the higher N treatment show more breakdown at lower temperature storage in year 1, though that difference did not repeat in year 2.

Fruit Nutrient Content

The 0 N fruits had higher levels of Ca and Mg. N levels were higher for fruits from trees in both of the N fertilized treatments. The high N fruits accumulated more P than the other two treatments. No differences in fruit K were found.

Leaf Nutrient Content

Vines that did not receive N fertilization showed a marked reduction in leaf N content. Leaf K content did not different between treatments, though leaf Mg, Ca, and S were generally lower under 0 N fertilization.