Fruit productivity and carbon gain of Opuntia ficus-indica (L.) Mill. trees

Opuntia ficus-indica (OFI) tree and orchards efficiency has been poorly studied, in terms of relation between orchard lay out, light interception, and cropping efficiency. Apparently, there is no other way to increase orchard production than increasing the number either of trees ha-1 or fertile shoots tree-1, considering that a fruit count higher than 6-7 cladode-1 reduces fruit harvest size. The first option requires a reduction of unit tree size and canopy volume. The second option implies the use of large trees that often reduce their efficiency 12-15 years after planting. In 15-year-old OFI trees spaced 6 5 m apart trained to a globe and 2.5-3.0 m high, stem area index (SAI) calculated on the ground surface area covered by the tree was 2.9 and 6.5, respectively, for most active 1- and 2-year-old cladodes and whole canopy surface area. SAI orchard (cladode surface area/ground surface area allotted to the tree) values were slightly lower: 1.8 and 3.9. The proportion of annual dry matter allocated to the fruit component (harvest index = HI) was 34% and 46%, respectively, for the spring flush and for the summer flush that results from the removal of the spring flush of flowers and cladodes (SFR). However, for 8-year-old OFI trees grown at a density of 333 trees ha-1 the calculated HI was about 25%