This study is aimed to evaluate the influence of nitrogen and potassium fertilization in the development of custard apple tree floral buds in two growing cycles, one at the spring-summer period, with rainfall and high temperatures, and another at the autumn-winter period without rain and lower temperatures.
In the experiment, (useful plants), 144 custard apple tree plants were used, with the age of four years old, originating from un-grafted seedlings with an average of 1.50 m in height; 0.90 m crown (capony) diameter and 0.21 m trunk diameter from 0.10 m above the ground, being planted in a spacing of 5.0 x 2.5 m, making up a total of 800 plants per hectare, daily irrigated by micro-sprinkling with an micro spraying per plant, where the quantity of water used was 30L per plant [h.sup.-1], with irrigation time of three hours.
This defoliation is common practice among producers of custard apple tree that aims to force and to uniform the sprouting of new branches and flowers.
Probably, the soil was already with high contents of N due to rain and that the extrinsic application of this element did not contribute to greater absorption thereof by the custard apple tree in order to positively affect the vigor of the buds, on the contrary, the probable excess reduced the development of the flower buds, possibly by a nutritional imbalance.
It was found as it shows in table 3, that the values obtained in mass and length of the first blossoming (December / 2013) were superior to those of the second blossoming (May / 2014), both for doses of N and for K rates, probably influenced by the higher temperature period and rainfall which stimulates the custard apple tree development (Figures 1 and 2).
In the conditions of how the work was performed, it can be concluded that the vigor of the custard apple tree floral buds tend to increase with increase of the amount of nitrogen applied in autumn-winter periods (no rain and low temperatures).
Other studies deal with the numbers of fruits sold (Fagundes & Yamanishi, 2001), price seasonality (Morgado et al., 2004), and losses observed during trade (Silva et al., 2003), including those verified for custard apple trees.
However, there is no available information about the useful lifetime of custard apple trees (Sao Jose et al., 1997).
It is possible that the intercropping of custard apple trees with other annual crops, especially in the initial years, will contribute to reduce losses resulting from the exploitation of this fruit tree during those years.
It is important to point out that the technified system has proved to be the most profitable in custard apple trees, despite its higher cost when compared with the conventional system (Pelinson et al., 2005).
Few studies (Carvalho et al., 2000) were found in the consulted literature dealing with custard apple tree genotype assessment, so that the comparison of results obtained in the present study with those from other authors is limited.
The increased demand for custard apple trees has encouraged the collection, characterization and evaluation of germplasm, aimed at obtaining cultivars (Sousa et al., 2001).
The differences between fruit characteristics observed in the present work (Tables 4, 5 and 6) and those obtained by other authors are obviously due to the different custard apple trees evaluated, as well as to the edaphic-climatic and management conditions to which the plants were exposed.