Relacion entre propiedades del suelo y el efecto de coberturas vegetales, en aguacate (Persea americana Mill.).

摘要

In 2007, Puerto Rico imported 64 percent of the avocado consumed, which could suggest the economic potential of increasing its production, although this must take into consideration several factors, among others, production costs. Avocado production in the island has been plagued by high incidence and severity of root rot disease associated with Phytophthora cinnamomi . This disease is exacerbated by the saturated soil conditions during the rainy season (July--October), high temperatures, and the soil cracking during the dry season which causes mechanical damage to the root system. Planting of leguminous cover crops around avocado trees has been suggested as a possible means of reducing the Phytophthora root rot problem. The objective of this study was to evaluate effects of cover crops on soil properties in two avocado orchards. In May 2006 two avocado orchards were established; one in Juana Diaz with avocado cultivar Semil 34/Semil 34 (rootstock/scion) and the other in Isabela with cultivar Gripina/Wilson Popenoe (rootstock/scion). In Juana Diaz, the dominant soil series was San Anton ( fine-loamy, mixed, superactive, isohyperthermic Cumulic Haplustolls) and the cover crops evaluated were Arachis pintoi Krapov. & W. C. Greg. 'Porvenir' and Arachis glabrata Benth. TARS 17095. At Isabela the soil series was Coto (very-fine, kaolinitic, isohyperthermic Typic Eutrustox) and the cover crops were Arachis pintoi Krapov. & W. C. Greg. 'Porvenir' and Desmodium heterophyllum (Willd) DC. CIAT 349. The cover crops were planted on May and June 2006 in Juana Diaz and Isabela, respectively; and were compared to a control (no cover crop coverage) in a completely randomized design with four replications. In Juana Diaz, after 21 months of cover crop establishment, the percentage of water stable soil aggregates was significantly different (p≤0.05) between the Arachis glabrata treatment (46.24%) and the control (22.36%). Significant differences in saturated soil hydraulic conductivity were found after 23 months, with greater conductivity (6.29 cm/hr) occurring in the A. pintoi treatment. Soil bulk density for the A. glabrata treatment (1.30 g/cm3 ) was significantly lower than in the control (1.51 g/cm3). Soil moisture retention curves performed at 12 months indicated greater water retention in the A. glabrata treatment than in the control, but differences were not statistically significant. Soil mechanical resistance, measured with a penetrometer, was not statistically different between treatments. Cover crops resulted in increased total nitrogen and decreased available phosphorus but no significant differences were found in soil organic matter, C:N ratio or pH. In Isabela, no significant differences were found in the percentage of water stable soil aggregates, bulk density, field infiltration, or soil moisture retention curves although a tendency toward improvement of these properties in cover crop treatments seemed evident. Mechanical resistance was significantly lower in A. pintoi treatment than the other two treatments. No significant differences were obtained in the soil chemical properties. The lack of influence of the cover crops in the Oxisol can be attributed to its natural state that presents good physical properties. Based on this study, A. glabrata TARS 17095 can be recommended as cover crop for avocado orchards in the Mollisol and A. pintoi 'Porvenir' as cover crop in the Oxisol.