NITROGEN AVAILABILITY AND FRUIT YIELD GENERATION IN CACTUS PEAR (OPUNTIA FICUS-INDICA): II. EFFECTS ON SOLAR RADIATION USE EFFICIENCY AND DRY MATTER ACCUMULATION
The effect of N availability on crop growth, fruit yield and quality of cactus pear is not well known. The objectives of this work were to determine the effects of N deficiency or excess on aerial dry matter accumulation and its main components, cladodes and fruits, as well as on solar radiation use efficiency (RUE). The trial was carried out under irrigation at Santiago del Estero, Argentina, during 1998-1999 and 1999-2000 growing seasons, using Amarilla sin Espinas cactus pear. Treatments were: Nlow (16 t ha-1 sucrose to immobilize N), Nmedium (100 and 150 kg ha-1) and Nhigh (200 and 300 kg ha-1 N) the higher rates were applied in 1999-2000). N content of soil and plant, number of vegetative and reproductive buds, cladode area, solar radiation interception by the crop (IRFA), dry matter accumulation in cladodes, fruits and total aerial biomass, and the relative contribution of RUE to aerial dry weight were determined. N fertilization increased aerial dry matter (standardized by cladode number), increasing vegetative organs more than reproductive ones during the first year, and the inverse during the second year. High N availability increased IRFA more than RUE during the first year and produced similar increments in both components during the second year. Relative increases of IRFA and RUE were similar for Nlow, Nmedium and Nhigh during the second year, but absolute values were higher for N fertilization treatments. Irrigation and fertilization management of experimental site increased the rate of soil organic matter mineralized in all N treatments, variable that may partially explain the responses obtained during the second year. These results may help to optimize N fertilization in cactus pear and to improve models that simulate the effects of N on cladodes, fruits and total aerial dry mater accumulation as well as on RUE.
Ochoa, M.J. and Uhart, S. (2006). NITROGEN AVAILABILITY AND FRUIT YIELD GENERATION IN CACTUS PEAR (OPUNTIA FICUS-INDICA): II. EFFECTS ON SOLAR RADIATION USE EFFICIENCY AND DRY MATTER ACCUMULATION. Acta Hortic. 728, 125-130
fertilization, growth, biomass, yield, fruits