Fertilizer handling and safety
Apples
Nitrogen form is important for yields. Calcium nitrate forms are readily available and can produce higher yields. Compared to ammonium nitrate, calcium nitrate also has an effect on maintaining soil pH, improving tree growth and ensuring other nutrients are more available.
Calcium activates enzymes and is essential for cell division, elongation, and fruit growth.
Phosphorus has a direct effect on yield. As the season develops, leaf phosphorus concentration decreases, with phosphorus being transferred to the fruit. As fruit weight increases, so does the amount of phosphorus in the fruit. Thus, it is important to ensure supplies are not limiting throughout the season to maintain good growth and steady accumulation of phosphorus in the fruit.
Where supplies are inadequate, potassium yield responses have been recorded following applications of up to 600-700 g/K/tree in low density orchards. Some of this yield increase comes from an increase in fruit weight. However, applications need to be adjusted according to soil potassium levels: where levels are high, high K fertilizer rates may lead to a yield reduction, mainly due to a reduced uptake of other cations (Mg and Ca).
Asia and Oceania
