ABSTRACT
Yield is obviously related to the number of leaves produced and the amount of growth added. Hence, water is required during the growing period for potential yield. Under low moisture conditions, floral sex shifts towards female sterility resulting in low productivity (Ram et al. 1985a, b). Responses to water stress include dehydration postponement through strict stomatal regulation, cavitation repair and intense osmotic adjustment (Mahouachi et al. 2006). At the same time, over-irrigation may cause root rot diseases. Thus, efficient water management is required. Number of irrigations depends upon soil type and weather conditions of the region. Protective irrigation is required in the first year of planting (Figure 7.1a). In general, irrigation to grown-up plants is given once in 7-10 days in winter and 4-5 days in summer. In the second year, when the plants are ladden with fruits, irrigation at fortnightly interval in winter and at 10 days interval in summer is needed from October to May. Excessive moisture is more detrimental to plant than moisture stress necessitating the effective drainage system, especially in heavy soils under high rainfall conditions, to avoid plant mortality. Studies conducted at Coimbatore have also indicated that papaya has high tolerance for heat and soil moisture for higher productivity; however, moisture stress at fruit development stage should be avoided. Total water requirement of CO-2 papaya under tropics is estimated to be 1800-1900 mm and excessive depletion of moisture causes reduced growth and yield. However, intermittent moisture stress induces deep root penetration. Depletion of soil moisture also causes increase in N and Mg content, while Ca content is reduced. Irrigation at 60% available soil moisture depletion is found to be the optimum for papaya. Regular irrigation is an important aspect in papaya cultivation, which helps in the growth, fruit development and high yield. Moisture stress inhibits the growth and also promotes male floral characters. The ring system of irrigation has been found very effective among different methods. This system helps in preventing the collar rot (Figure 7.1b) as there is no direct contact between the water and the stem portion. In low rainfall areas, where water is scarce, sprinkler or drip systems of irrigation can be adopted for higher production, saving water from 50 to 60%.
