11. Soursop
(Annona muricata L.)
Alberto Carlos de Queiroz Pinto1


11.1.
Introduction
Soursop (Annona muricata L.) is grown in many tropical countries, for example
Angola, Brazil, Columbia, Costa Rica, Cuba, Jamaica, India, Mexico, Panama,
Peru, Porto Rico and Venezuela (Pinto and Silva, 1994). The generic name
Annona means “annual harvest” in Latin (Lizana and Reginato, 1990). Annona
species have many characteristics in common with many other tropical fruit
species, especially the height of the plant, root system, flower biology, and type
of fruit type (Ochse et al., 1974).
Soursop is considered a bush plant, the height varying from 4 to 8 m, depending
on factors like climate, soil and crop management. It tends to have an extended
growth. The flowers are hermaphrodite and emerge from the branches and trunk
in groups of two to four flowers with three green sepals and six petals arranged
in two whorls. The fruit is a spiny berry with many carpels commonly called
“spines” or “barbs” with a weight varying from 0.9 to 10 kg (León, 1987).
The root system consists of a main (or tap) root, 1.5 to 1.8 m long, and abundant
lateral roots (Pinto and Silva, 1994). The tap root is not as vigorous and does not
grow as deep as that in other tropical fruit trees, like the mango (Mangifera
indica L.). These characteristics are very important when planning fertilization
and making decisions about managing this crop.

11.2.
World production and trends
There is very little literature about this crop with the exception of information
from Mexico, Brazil and Venezuela. In the Americas, Mexico is the most
important producer of soursop and in 1997 it was grown on approximately
5,900 ha and produced about 35,000 mt of fruit. In 1987, in Venezuela, there
were about 3,500 ha and total production was about 10,000 mt (Hernández and
Nieto Angel, 1997).
Brazil grows approximately 2,000 ha with an estimated production of about
8,000 mt, almost completely for sale in the internal market. Owing to the

1 Embrapa Cerrados, BR 020 kam 18 Rodovia Brasilia/Fortaleza, Caixa Postal
403, CEP 73301-970, Planaltina-DF, Brazil, E-mail: alcapi@terra.com.br.

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favorable climate, about 90% of the total Brazilian production comes from the
north-eastern region of Brazil. In the state of Ceará, located in the Brazilian
north-east, there is an estimated 500 ha of soursop, and the fruit goes mainly to
produce juice (Bandeira and Braga Sobrinho, 1997).
Soursop is rich in mineral salts, principally calcium (Ca) and potassium (K), and
its flavor is enjoyed as juice and jam. It is considered to be a commercial fruit
mainly grown for the internal market and selling in the local in Brazilian
currency for about R$ 2.50 kg/fruit. Very little of the fruit is exported and there
is little growth in exports which rely on the actions of a few pulp and juice
manufacturers in the north-east of Brazil.

11.3.
Climate and soil
11.3.1. Climate
The genus Annona includes, for the most part, tropical and subtropical plants,
although a few species develop in temperate climates. Many species grow at low
altitudes and those with a wide adaptation to altitude are also the species most
adapted to variations in latitude. The optimal range of latitude is between 27ºN
and 22.5ºS (Nakasone and Paull, 1998).
Soursop is the most tropical of the Annona species and is considered a plant of
low altitudes and a hot and humid climate. It is grown primarily at altitudes
lower than 900 m above sea level (Zayas, 1966). However, good productive
orchards are found at altitudes of up to 1100 m (Pinto and Silva, 1994). Soursop
adapts well to Savanas and tropical humid regions, i.e. A and Aw type climates,
where the annual precipitation generally exceeds evapo-transpiration (Ayoade,
1991).
Two important climatic factors are rain, principally when out of season, and
strong winds. Both, when they occur in great intensity and during flowering,
greatly reduce pollination (Nakasone and Paull, 1998).
Although the photoperiod is not an important physiological factor for the
annonas, excessive shading induces poor setting of the fruit. Therefore, pruning,
plant spacing and fertilization are some of the very important practices in
orchard management. Soursop is very demanding of light and shading the plants
greatly reduces the production of fruit (Villachica et al., 1996). Soursop grows
and produces well at 21 to 30ºC, being very sensitive to severe changes in
temperature, especially if the limit of 12ºC is reached (Pinto and Silva, 1994).
Nakasone and Paull (1998) considered that the best temperature range was
between 15 and 25ºC.


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11.3.2. Soil
Soursop will grow in a wide variety of soils, from sandy to clay loams, but it
prefers deep soils with good aeration (Melo et al., 1993; Ledo, 1992). Good
drainage is necessary for good root development, and, especially, to avoid
problems of root diseases. Soil pH should be between 6.0 and 6.5 (Pinto and
Silva, 1994).

11.4.
Soil and crop management
Soil preparation for a soursop orchard includes land clearing, aeration,
ploughing, application of lime, if necessary, and appropriate fertilization.
Soil sampling and analysis are precede aeration and ploughing. The amounts of
lime and fertilizer to apply are decided on the basis of the analytical data. Where
the soil is acidic, which is very common in Brazil, liming is extremely important
not only to adjust the pH to 6.0 to 6.5, the best range for soursop, but also to
achieve a base saturation of between 60 and 70% (Pinto et al., 2001). Liming is
also recommended when the subsoil to a depth of 60 cm is acidic, i.e. Al
saturation >20% and/or Ca <0.5 cmolc/dm3 (Andrade, 2002).
Fertilization is generally recommended for soils deficient in phosphorus (P) and
potassium (K), and the fertilizers are broadcast onto the soil around the plant,
followed by incorporation into the soil (Andrade, 2004). The recommendation
for P fertilizer is based on the amount of clay and the quantity of plant-available
P determined by soil analysis (Table 11.1).

Table 11.1. Phosphorus fertilizer application according to percent clay in the
soil and level of plant-available phosphorus in the soil.
Clay concentration
Phosphorus availability in the soil (mg/kg)
0-10
10-20
>20
g/kg
---------- P application, P2O5 (kg/ha) ----------
≤150 60
30
0
160-350 100
50 0
300-600 200
100 0
>600 280
140
0
Source: Sousa and Lobato, 2004.

Correcting soil fertility where an orchard is to be planted has a cost, which must
be considered. If fertilizer is broadcast over the whole area of the orchard annual
plants should be grown between the rows of soursop to provide some economic

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return to the grower before the soursop starts to produce harvestable fruits three
years after planting the trees.
Soursop can be propagated from seed (“loam tree”) and by budding. The height
of the plant is not greatly affected by budding and the majority of producers
prefer using grafted seedlings rather than seeded seedlings. Propagation by seed
or graft is done in plastic bags in a growth medium that varies from region to
region. The constituents in the growth medium in the nursery phase are very
important. Depending on the material and quantity used, there is the possibility
of interfering with seed germination and of phytotoxicity burning the young
leaves and causing the death of the seedlings (Pinto and Silva, 1994).
Although there is variation in the recommended use of nutrients in different
regions, Pinto (1996) recommends the following constituents for each m3 of
growth medium (about 700 kg): 300-350 kg of local soil, 300-350 kg cured
bovine manure, 300-500 g lime and 400-600 g of single superphosphate. After
preparing the mixture it should be exposed to sunlight to eliminate diseases.
Rego (1992) studied the effect of cured bovine manure applied at 0, 5, 10, 15,
and 20% of the growth medium on the growth of seedlings over a period of four
months. The author concluded that 15% manure was the most effective.
After germination and during seedling growth, nitrogen (N) should be applied
every 21 days as a solution of ammonium sulphate at 5 g/L water. After the
fourth month the seedlings should receive micro-nutrients as a foliar spray
bimonthly using a commercial product in a 1-2% solution (Pinto and Silva,
1994).

11.5.
Mineral nutrition
11.5.1. Uptake and export of nutrients
When the plants are producing fruit, the amount of fertilizers required should be
based not only on soil and leaf analysis, but also the nutrients removed in the
harvested fruits. In fact the nutrients removed in the fruit are an excellent guide
to establish a fertilization programme for any fruit tree in is production phase
(Mengel and Kirkby, 1987; Torres and Sánchez López, 1992; Hermoso and
Farré, 1997). The quantity of each nutrient removed in the fruit varies between
varities but, on average 10 mt fruits remove 27 kg N (Table 11.2).
The amount of nutrients in soursop fruits produced in Venezuela and in Brazil
differs greatly in K and Ca but is similar for the other macro-nutrients
(Table 11.3). In Paraiba state, Brazil, the quantity of micro-nutrients per tonne
of soursop fruit is: Fe, 8.03 g; Cu, 1.65 g; Mn, 2.71 g; Zn, 3.71 g; and B, 2.75 g
(Silva et al., 1984), with Fe being the largest amount.


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Table 11.2. Amount of macro-nutrients in some tropical and subtropical fruits
(kg/mt fruit).
Nutrient Avocado(1) Pineapple(1) Orange(1) Banana(1) Soursop(2)
Macro-nutrient
----------------------------------- kg/mt -------------------------------------
N
2.80
0.90
1.20
1.70
2.70
P
0.35 0.12 0.27 0.22 0.54
K
4.53 2.00 2.60 5.50 3.60
Ca
0.13 0.10 1.05 0.21 0.26
Mg
0.20 0.16 0.20 0.27 0.24
Source: (1)Marchal and Bertin, 1980; (2)Silva et al., 1984.

Table 11.3. Amount of macro-nutrients in harvested soursop (kg/mt fruit)
grown in Venezuela and in Brazil.
Nutrient Venezuela(1)
Brazil(2)
Macro-nutrient
----------------------- kg/mt -----------------------
N 2.97
2.70
P
0.53
0.54
K 2.53 3.60
Ca 0.99 0.26
Mg 0.15 0.24
Source: (1)Avilan et al., 1980 ; (2)Silva et al., 1984.

11.5.2. Functions and importance of macro-nutrients
Nitrogen (N): Deficiency of N causes an intense yellowing in the oldest leaves
because if the supply of N is limited it is mobilised and transported to the
youngest tissues, principally for growth. Symptoms of deficiency in young
plants (seedlings) appear in the first 30-40 days after germination. Generally,
plants of the genus Annona when N is deficient show a visual progression in the
symptoms to intense yellowing and loss of leaves. Other than yellowing of the
leaves, young plants are markedly smaller in height and have a very premature
loss of leaves.

Phosphorus (P): Deficiency of P is seen by an irregular chlorosis of the basal
leaves with many showing a dark green coloring. With increasing deficiency,
the leaves become small and take on irregular shapes. Deficient plants grow
very slowly and have brown spots on the leaves with necrosis on the lamina
margins, followed by the leaves falling off the plant.


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Potassium (K): In general, K deficient plants do not have the ability to transport
sugars produced by photosynthesis in the leaves to the other organs, principally
the fruit. Potassium can move from the oldest organs, primarily the leaves, to
the youngest or to growth. Brownish spots start at the apex and the basal portion
of the leaf lamina and gradually merge. In seedlings these symptoms first appear
eight months after sowing the seed when the size of the leaves is reduced and
they become yellow and fall off. Deficient plants produce fewer flowers but
there is no loss of yield.

Calcium (Ca): Symptoms of Ca deficiency are manifest 30 days after sowing
and appear first at the points of growth, like buds and the young leaves because
Ca is not mobile within the plant. About 70 days after sowing, the leaves show
interveinal chlorosis, stop growing and become curled.

Magnesium (Mg): Unlike Ca, Mg is mobile in plants so that initially deficiency
symptoms occur in the oldest leaves. In nursery conditions, an interveinal
chlorosis starts in the leaves about 50 days after sowing and progressively the
leaves become totally necrotic. The adequate ratio of Ca: Mg is 3: 1 because a
greater proportion than this of Ca induces Mg deficiency. In the same way,
elevated ratios of K induce deficiencies of Mg and Zn.

Sulphur (S): Like calcium, the first symptoms of S deficiency occur in the
youngest leaves because S is largely immobile in the plant. In nursery
conditions, young S deficient plants are intensely yellow and atrophied after
about 75 days.

11.5.3. Functions and importance of micro-nutrients
Boron (B): Like Ca, B is immobile in phloem and for this reason the first
symptoms of its deficiency occur in the young leaves. In seedlings still in the
nursery, deficiency symptoms appear around 70 days after sowing, when the
seedling leaves have an intense green color with chlorosis of the lamina. By 140
days after sowing the plants have atrophied. Maintaining adequate amounts of
plant-available B and Ca during flowering and the first stages of fruit production
reduces the possibility of internal darkening of the pulp, which is common in
annonas.

Iron (Fe): Like Ca and B, the redistribution of Fe in the plant is practically zero.
Thus the initial symptoms of Fe deficiency occur in the young leaves and are
characterized by partial chlorosis with yellowish-green coloration of the lamina,
which with time becomes totally yellow except in the region around the veins.

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Zinc (Zn): Plants with Zn deficiency frequently show interveinal chlorosis in the
leaf lamina area and appear pale-green in color. Deficient plants have irregularly
distributed, small, branched and hardened leaves at the apex of new branches,
and this is known as leaf rosette.
The observation and identification of the nutrient deficiency symptoms in the
field can be done quickly but it requires very experienced people. Therefore, not
only field observation, but also soil, fruit and leaf analysis are very important to
determine the nutritional state of the plant. To aid the determination of macro-
and micro-nutrient deficiencies in plants, including the annonas, the symptoms
have been described by many authors (Avilan, 1975; Navia and Valenzuela,
1978; Mengel and Kirkby, 1987; Torres and Sánchez, 1992; Silva and Silva,
1997). Finally, there is evidence that well nourished plants are more resistant to
pests and diseases, producing a larger yield of good quality fruits.

11.6.
Fertilization
At planting: Adequate fertilization of the planting pit is a basic condition for
excellent seedling growth that will result in a productive adult plant producing
good quality fruit. The amount of fertilizer to apply is based on soil analysis and
on the volume of pit, which is usually 60 x 60 x 60 cm.
In Venezuela it is recommended to mix 250 g of a 10-10-15 or 10-15-15
fertilizer with 5 kg of corral manure (Araque, 1971). For the acidic soils of the
Cerrados, Andrade (2004) suggests the following quantities of manure, lime and
fertilizer per pit: 21.6 L of cured bovine manure or 5.4 L poultry manure; 216 g
lime (PRNT 100%); 151 g P2O5 (367 g of triple superphosphate); 1.0 g B; 0.5 g
Cu; 1.0 g Mn; 0.05 g Mo and 5.0 g Zn. Nitrogen and K, at 20 g/plant, should be
applied around the plant in three portions at intervals of 30 days between each
application (Andrade, 2004). In pit fertilization with micro-nutrients it has been
quite common to use 100 g/pit of F.T.E. formula BR-12. For virgin soil, when
soil analysis results are not available, the following quantities (kg/ha) of micro-
nutrients should be applied broadcast: B, 2 kg; Cu, 2 kg; 6 kg Mn; 6 kg Zn
(Galrão, 2004).

During growth: After planting the seedlings, the amounts of fertilizer applied
during the next three years should be based on chemical analysis of the soil
(Table 11.4) as recommended by Silva and Silva (1997).


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Table 11.4. Nitrogen, phosphorus and potassium for soursop according to the
age of the plant and the availability of soil phosphorus and potassium.
Age N
P-resin
(g/dm3) K-exchangeable
(g/dm3)


0-10 11-20 >20 0-45 46-90 >90
Yr g/plant
P2O5 (g/plant)
K2O (g/plant)
0-1
40 0 0 0 60 40 30
1-2
80 80 60 40 80 60 40
3-4
120 120 80 60 120 80 60
>4
180 120 80 40 180 120 60
Source: Silva and Silva, 1997.

Fertilizer should be applied around the plant but only lightly incorporated into
the soil to avoid damaging the developing root system whilst putting the
fertilizer near them. In a dryland plantation, the annual fertilization with P
should be done in a single application at the beginning of the rainy season. The
required quantity of N and K fertilizer should be divided into three and one third
applied at the beginning, in the middle and at the end of the rainy season. The
amount of fertilizer applied can be changed from one year to another. At the end
of the first year after planting, the fertilizer given in the second year should be
based on soil analysis and for the third year on the basis of leaf analysis.

During production: Torres and Sánchez López (1992) recommend different
quantities of nutrients depending on the region, i.e. the InterAndean Valley, the
Atlantic Coast and Eastern Plains of Columbia. These authors suggest that the
amount of N fertilizer for plants between three and six years old should be based
on the amount of soil organic matter, whilst for P and K they should be based on
the level of plant available P and K in the soil. Because N and K are the
nutrients in greatest demand by soursop, the amounts should increase
proportionally with the age of the plant and its level of production. However,
care should be taken to give excess N because this causes the plants to grow too
quickly and produce less fruit. Soursop’s large demand for K means that the
concentration of K in the leaf should not be less than 10 g/kg to ensure that K is
not limiting growth. On sandy soils and others where there is a risk of N and K
being lost by leaching, N and K fertilizers should be applied six times during the
growing season. For adult plants fertilizers should be applied beneath the crown
in an area including two thirds of the radius beneath the crown and extending
one more quarter from the edge of the crown’s projection (Fig. 11.1).



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Area of projection
Area of projection
Área de projeção da copa
Área de pr
of ojeç
can ão da
opy copa
of canopy
Fertilized area
Área de adubação
2.00 m
2.00 m
0.50 m
1.50 m
1.50 m
0.50 m

Fig. 11.1. Fertilizer should be applied on both sides of adult plants and cover
two thirds of the radius of the crown and one more quarter beyond the edge of
the crown (Pinto, A.C. de Q., 2001).

In general, soursop is sensitive to Zn and B deficiency. To prevent deficiency,
2 g m-2 B can be incorporated monthly into the 10 cm of soil beneath the plant’s
crown before irrigation and a 0.1% solution of zinc sulphate applied as a foliar
spray. Galrão (2004) recommends the following quantities of micro-nutrients
during the production phase of the adult plant: 2.0 g B, 3.0 g Cu, 4.0 g Mn and
5.0 g Zn, all incorporated into the soil below the crown projection together with
other fertilizers, at the start of fruit production.
There has been little research on foliar applications of both macro- and micro-
nutrients for soursop. When the fruit is mature the absorption of nutrients
diminishes and foliar applications of nutrients are more effective at this time.
Today producing fruit by organic systems of production is an excellent method
for increasing the value of the fruit. However, there is serious lack of
information regarding appropriate methods of growing annonas, especially
soursop, by organic methods. One of the few exceptions is that of Bonaventure

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(1999) for cherimoya (Annona cherimola Mill.). He recommends using
microorganisms and algae, as well as a bio-activator, which accelerates the
metabolism and increases the production of this important annona.
Currently, the use of organic compost and mulching with organic material in
soursop plantations has been recommended because the plants respond both in
growth and yield. Organic compost and mulching facilitates not only the
development of vigorous and abundant roots, but also improves moisture
retention in the soil and minimises the risk of soil erosion.
As with other perennial fruit trees, chemical soil and plant tissue analysis are the
techniques most used to evaluate the nutritional state of the plants. In some
cases, for example, leaf analysis may indicate deficiency of Mg but the cause
may be in the soil where there may be too little Mg or an excess of Ca.
Currently, some researchers have also tested the analysis of fruit tissue (Stassen
1997) to complement soil and leaf analysis.
Soil sample collection in soursop orchards in the production phase is the same
as that recommended for other crops, but the soil should come from within the
crown projection.
The recommended method for leaf sampling for nutrient content depends on the
age of the plant, the position of the leaf within the crown, the variety and
whether the branches are with or without fruit and the period of sampling.
Laprode (1991) suggests that the leaves should be taken from the third and
fourth pairs of intermediate branches in the crown and of the four cardinal
points. Pinto and Silva (1994) recommend that the leaves should be 8 to 9
months old, taken from healthy plants free from residues from any foliar sprays.
In general, the sample should consist of 100 leaves for every five hectares by
taking four leaves per plant from a group of 25 plants randomly selected in the
orchard. For a more uniform sample it is recommended to divide the orchard
into sections of similar soil characteristics, and in each section separate the
plants by chronological age. Collect only healthy leaves from plants that have
not been recently fertilized, avoiding the period of flowering and periods of
intense rain.
Soil and leaf analysis data are interpreted using calibration curves for each
nutrient, based on the correlation between the composition of each nutrient and
the productivity of the fruit tree (Silva et al., 2002).
Isolated leaf analysis is not sufficient for precise interpretation and diagnosis of
the nutrient status of the plant because of the many factors that cause variation
in leaf nutrient status. In general, the composition of N is about ten times that of
P and twice that of K. Gazel Filho et al. (1994), analysed leaves from a range of
one-year-old soursop varieties growing in Cerrado do Amapá, Brazil. The
varieties were: Blanca, Lisa, Morada, Soursop A, Soursop B, FAO II and Matriz

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