Productivity of olive orchards in response to tree density.

摘要

Tree density in newly planted olive orchards has been increasing steadily as part of the intensification of olive oil production. Because of the importance that harvest costs have on the profitability of this crop, the mechanization of harvesting operations has been an important goal. Hedgerow plantations at very high densities have been proposed as a means of reducing harvest costs by using an over-the-tree harvester. We conducted an 8-year experiment in Cordoba, Southern Spain, to evaluate the performance of olive orchards at four planting densities that included: (a) the conventional density under irrigated conditions of 204 trees ha-1 (7 m x 7 m; D1); (b) 408 trees ha-1 (7 m x 3.5 m; D2); 816 trees ha-1 (3.5 m x 3.5 m; D3); and, almost 1,904 trees ha-1 (3.5 m x 1.5 m; D4), the recommended density for the hedgerow system. Yields for the first 3 years of production were highest in D4, reaching almost 20 t fruit ha-1 in year-3. Thereafter, the need for topping the D4 canopy to 2.5 m, to adapt it to the harvester, reduced D4 yields drastically. The relationships between intercepted radiation, vegetative growth, and reproductive development at the branch level, were explored in D4 canopies in 2005 to understand the effect of shading on yield-determining processes. At the end of the sixth producing year, the cumulative fruit production of D4 was 60 096 kg ha-1, while the yields of D1, D2, and D3 were 32 513; 60 125 and 76 149 kg ha-1, respectively. Fruit oil content in D4 was less than in all the other densities, and cumulative oil yields for the first six producing years were 6,829; 12 853; 14 973 and 10 113 kg ha-1 for D1, D2, D3 and D4, respectively. It is concluded that the hedgerow system, in its current form and management, is less productive and probably less sustainable than orchards planted at densities such as that of D2..