NITROGEN AVAILABILITY AND FRUIT YIELD GENERATION IN CACTUS PEAR (OPUNTIA FICUS-INDICA): I. EFFECTS ON CLADODE AREA AND CROP SOLAR RADIATION INTERCEPTION
The effect of nitrogen (N) availability on cactus pear growth and its components is not well known. The objectives of this work were to determine the effects of N shortage and excess on cladode number and area and on crop solar radiation interception (IRFA) by the crop. The trial was carried out using 'Amarilla sin Espinas' cactus pear under irrigation in Santiago del Estero, Argentina, during the 1998-1999 and 1999-2000 growing seasons. Treatments were: Nlow (16 t ha-1 sucrose to immobilize N), Nmedium (100 and 150 kg ha-1 N in 1998-99 and 1999-2000) and Nhigh (200 and 300 kg ha-1 N in 1998-99 and 1999-2000). N content of soil, cladodes and fruit, plant phenology, number of vegetative and reproductive buds, cladode area and IRFA by the crop were determined. N fertilization increased cladode number only during the first year, with no effect on the area of each cladode. Then, higher N availability increased cladode area index (CAI) and absolute crop solar radiation interception by 5 to 6% and up to 20% as relative values. During the second year, N fertilization did not modify cladode number, CAI or IRFA. The differences generated during the first year were maintained. Irrigation and fertilization increased the rate of soil organic matter mineralized in all N treatments. This variable partially explains CAI and IRFA responses during the second year. The results may help manage N fertilization in cactus pear and improve models that can predict the effects of N on cladode number, CAI and IRFA.
Ochoa, M.J. and Uhart, S. (2006). NITROGEN AVAILABILITY AND FRUIT YIELD GENERATION IN CACTUS PEAR (OPUNTIA FICUS-INDICA): I. EFFECTS ON CLADODE AREA AND CROP SOLAR RADIATION INTERCEPTION. Acta Hortic. 728, 117-124
fertilization, growth, solar radiation, vegetative buds, extinction coefficient