Climate and Soil 55
necessary for the growth of papaya plants, although dry climate at the time of ripen-
ing is good for the fruit quality. Continuous cropping in the same field may result
in poor growth and cause disease problems for papaya trees. The ideal soil texture
for papaya cultivation under irrigation is a sandy loam or loam soil, but soils with a
clay content of up to 50% are also suitable. In very sandy soils, temporary over-satu-
rated conditions may occur if soil compaction or impermeable layers limit drainage.
Sandy soils normally have a very low water-holding capacity and poor nutrient status
due to low organic matter and clay content (<10%). A mulch and organic material
application can increase the potential of such type of soils. The ideal soil has a fairly
loose, brittle and crumbly structure. A compact or strongly developed soil structure
adversely affects water infiltration and root penetration. These soils are normally
associated with very high clay content in the sub-soil (>50%). While doing best in
light, porous soils rich in organic matter, the plant will grow in scarified limestone
or various other soils only with adequate care. It is preferred to plant a cover crop
(legume) as a source of organic matter. In such cases, the crop must be planted about
6 months before the transplanting (DAIS 2009). Calcium and phosphorous are ele-
ments that move very slowly downwards in soils. If there is a shortage of one of these
elements, especially in the sub-soil, it should be incorporated during soil prepara-
tion. If lime needs to be applied, it should be incorporated into the soil 6 months to
a year before planting. Papayas grow best in soils with pH values of 6.0–6.5. If the
soil exchangeable aluminium (Al) is not more than 30 ppm, soils with a pH of 5.5
or higher may be used (Rex and Rivera 2005). Decreased yields of papaya due to
nutritional deficiency of nitrogen, phosphorus, potassium, calcium and magnesium
in acidic soils (pH values below 5.5) have been reported. To overcome this problem,
either calcium carbonate or lime is added to the soil. On the other hand, if pH of the
soil is above 8.0 (alkali), deficiencies of magnesium, manganese, iron, zinc, copper
and boron have been reported. In this case, addition of sulphur is very effective
(Medina et al. 2003).