Desenvolvimento e acúmulo de nutrientes de palma forrageira (Nopalea) em diferentes sistemas de cultivo

Abstract

Cactus is a valuable forage resource for the Agreste and Sertão region of Pernambuco. Additional information addressing management practices and cropping systems using cactus IPA Sertânia (Nopalea cochenillifera Salm Dyck.) in the semiarid region are necessary. Two experiments evaluated the effect of different cropping systems and manure sources on morphological and productive characteristics of clone IPA Sertânia. Cactus nutrient accumulation and nutrient release from different manure types were also assessed. The experiments were established in March, 2011 in Caruaru – PE. In experiment 1, treatments were combination of cropping systems (cactus + leucanea, cactus + Gliricídia, and cactus in monoculture) and different manure sources (sheep, cattle, goat, and broiler litter). Manure was applied based on annual addition of 200 kg ha-1 N. Legume trees were planted in double rows (9 x 1 x 0.5 m) and the cactus planting space was 1 x 0.25 m. A split-plot arrangement in a complete randomized block design was used, with four replicates per treatment. Cropping system was the main plot and manure types the split-plot. Experiment 2 assessed nutrient accumulation by the cactus and nutrient release from different manure types on the cropping systems described for experiment 1. Manure types were incubated in nylon bags during different periods (0, 4, 8, 16, 32, 64, 128, and 256 d) and the cactus harvested at the same interval. In experiment 1, cactus was sampled in four sites 1-m apart in a transect perpendicular to the legume tree rows. Goat and sheep manure resulted in lower cactus DM production for all cropping systems, with average 16.4 t ha-1 yr-1 DM. Greater production (cactus+legume) occurred when cactus was planted in polyculture with Gliricídia and cattle manure was applied (21.7 t ha-1 yr-1 DM). Cladode number and cladode weight was greater when cactus was planted in monoculture (6.7 and 4.3 kg plant-1 in a fresh matter basis) and fertilized with cattle manure (6.4 and 4.2 kg plant-1 in a fresh matter basis). Cladode thickness was the only morphological characteristic affected by treatments. In general, cactus nutrient concentration was greater in polyculture and near the tree rows, with reducing nutrient concentration with increasing distance from the trees. Broiler litter presented greater decomposition after 256 d of incubation (34.1%). When planted with Gliricídia, cactus accumulated more N regardless the manure source, with averages of 977, 695, 672, and 629 g ha-1 d-1 N for broiler litter, sheep, goat, and cattle manures, respectively. Maximum cactus P accumulation was 40.9 kg ha-1 P during 256 d and 116 kg ha-1 P released from the manure during the same period. As a result, no P deficiency was observed. Maximum cactus K accumulation was 1487 g ha-1 d-1 K when cactus was planted in monoculture, followed by 1242 and 1106 g ha-1 d-1 K for the polyculture with Leucaena and Gliricídia, respectively. Cropping systems combining cactus and legume trees are a viable option for the region. Species diversity favours more efficient feeding strategies for livestock. Cattle manure resulted in greater productivity when cactus was planted combined with legume trees. Nutrient accumulation, mainly N, was influenced by the presence of the legume tree. Phosphorus was the least and K the most accumulated nutrient by cactus. broiler litter, in general, was the organic matter source presenting greater accumulation by the plant and released greater amounts of N, P, and K.