Although there have been small commercial plantings of cherimoya (Annona cherimola) in New Zealand in the past, little is recorded about its fertiliser requirements under local conditions. All of the information included in this section comes from Queensland and California. It seems that cherimoya will tolerate a wide range of soil types provided they are moderately fertile and free draining. It is also essential that uniform soil moisture is maintained from flowering to harvest.

PLANT ANALYSIS
Leaf samples should be collected towards the end of February or early March. The youngest mature leaf (fourth or fifth leaf back from the growing point) should be selected from actively growing non-bearing shoots.

Critical leaf concentrations for macronutrients and micronutrients have not been determined for cherimoya. The values listed in Table 1 are tentative ranges for healthy plants growin in Queensland and as such should only be used as a guide.

SOIL TESTING
Experience in Queensland indicates that soil analysis is generally less useful than plant analysis for formulating a fertiliser programme for cherimoya. Under their conditions a soil pH within the range of 5.7 to 6.3 is considered to be optimum for maximum production.

FERTILISER REQUIREMENTS
During the first four years, the tree is encouraged to produce a large potential bearing area on a strong symmetrically spaced framework. Fertilisers used should have a high proportion of N and be coupled with irrigation to promote vigorous vegetative growth. A tree of moderate to good vigour is usually the best producer; low or excessive vigour is usually associated with low yields. During the first year on n is required where an application rate of 15 to 20 g urea/tree every month from leaf emergence until March is recommended. Fertiliser requirements for trees two years and older are listed in Table 2.

Nitrogen and K should be applied in split applications, half of the recommended quantities in Table 2 to be applied in October and half in January. Phosphorus and S can be applied in a single application in October.

NUTRIENT DISORDERS
Up to the present time there have been no reports of any nutritional disorders of plants grown in New Zealand. However, it appears that cherimoya have a high requirement for Zn. Zinc deficiency is a common and widespread problem in Queensland. Symptoms of Zn deficiency include restricted terminal growth, small leaves, and interveinal yellowing of leaves. Zinc deficiency has been corrected by applying zinc sulphate (ZNSO₄5H₂0) at a rate of 25 to 30 g/m² of soil surface under each tree in a 30 cm wide band just inside the drop line. Foliar sprays have also been used but these have been less effective. Zinc sulphate at a rate of 100 g/100 l is sprayed onto mature leaves in spring. Low levels of Zn are known to occur in soils at Kerikeri.

Boron deficiency is thought to cause a condition in plants in Queensland where hard brown lumps form in fruit, particularly around the seeds. This condition has been corrected by applying 2 g borax/m² of soil surface beneath each tree. Even application and sufficient watering is essential to avoid tree damage. Foliar applications or borax are not as eficient as soil applications but are safer. A mixture of 300 g borax/100 l can be applied to mature spring growth. Although there are a number of soils in New Zealand which are naturally low in B, they are not found in areas where cherimoya are likely to be planted.

FURTHER READING
Dawes, S.N. (1985). Cherimoya - a subtropical fruit with potential. Growing Today, August: 18-20, 29.