Response of pawpaw (Carica apaya L.>/i>) to soil moisture stress at different developmental stages

Abstract

All year round demand for supply of pawpaw fruits in Nigeria necessitates irrigating pawpaw field during the dry spells. The moisture  sensitivity of developmental stages of pawpaw was investigated in a greenhouse study at the Department of Agronomy, University of Ibadan, Nigeria to design an irrigation schedule based on maintaining critical soil water potential at different developmental  stages.Three-month old seedlings of pawpaw cv. „Homestead Selection‟ potted in 80kg of loamy sand were irrigated whenever soil water potential fell below -0.02, -0.06, -0.20or -1.50 MPa at a depth of 15cm at the vegetative, flowering or fruiting stages. Moisture stress and developmental stage were combined in factorial and arranged following a completely randomised design replicated three times.At the vegetative stage, compared to -0.02MPa, soil water potential of -0.20 and -1.50MPa significantly decreased plant height, stem girth and leaf area, but not total dry matter accumulation. At the early flowering stage,compared to -0.02, -0.20 and -1.50MPa significantly decreased plant height and stem girth, -1.50 MPa significantly decreased flowering, while soil water potential had no consistent effects on leaf area.At the fruiting stage,soil water potential did not significantly influence plant height, stem girth or  number of flowers. Nonetheless, compared with -0.02 MPa, -0.06, -0.20 and -1.50MPa significantly decreased leaf area, while -1.50MPa halted fruit set and significantly decreased dry matter accumulation. The critical soil water potential for the vegetative is -0.06 MPa while for the flowering and fruiting stages it is -1.50MPa. These values should guide irrigation of pawpaw.

Key words: critical soil water potential, drought, hydro-periodicity, papaya