Estresse hídrico e adubação fosfatada no desenvolvimento inicial e na qualidade da forragem da gliricídia (Gliricidia sepium (Jacq.) Steud.) e do sorgo (Sorghum bicolor (L.) Moench.).

Abstract

The Gliricidia sepium is a characteristic species of tropical areas, tolerant to the drought, and comes being explored as forage plant by its high nutritious value and also as producing of live stakes. The sorghum is a very important grass for the Brazilian Northeast, for possessing potential forage and, due to its tolerance to the deficit hydric, the interest for its cultivation has been increasing in a significant way. Two experiments were driven in the Forest Nursery of the Centre of Health and Rural Technology of UFCG with the objectives of verifying the effects of the phosphate fertilization in the development, in the accumulation of macro and micronutrients and in the quality of the forage of Gliricidia sepium plants and of sorghum, submitted or not to the hydric stress. The experiments were driven in vases with nine kilos of soil, with the arranged treatments in blocks to the maybe, in scheme factorial 4x2, with 4 reapplications where the first factor consisted of doses of P (0, 50, 100 e 150 mg dm-³ and P) applied to the soil, and the second factor, of two humidity regimes (with and without stress). Verified the increase in the dry matter of the aerial part of the Gliricidia sepium plants not submitted to the hydric stress, not having significant differences for the sorghum. The fibre texts in neutral detergent and fibre in acid detergent were only significant for Gliricidia sepium without stress, not happening significant difference for interaction gross protein and humidity regimes. The increase in the concentration of P in the soil promoted increments in the production of dry matter of the aerial part to the dose of 109 mg dm-³ of P for the sorghum, and of 119 mg dm-³ of P for Gliricidia sepium. In the roosters, there was reduction in the dry matter accumulation with increase of the dose of P in both species. Happened increase in the text of gross protein with increase in the doses of P up to 137 mg dm-³ for Gliricidia sepium and 121 mg dm-³ for the sorghum. The height of plants and the diameter of the stem presented lineal increase in relation to the doses of P. The hydric stress increased the dry matter of the aerial part, reduced the fibre texts in neutral detergent and fibre in acid detergent and P provided larger accumulation of dry matter of the aerial part, gross protein and height and diameter of the stem of both species. The largest accumulation of N, P, Ca, S, Mn and Fe for Gliricidia sepium was reached with the doses of 137; 146; 150; 116; 134; and 123 mg dm-³ of P and, 4 in the sorghum plants, in the doses of 121; 126; 125; 126; 104 and 122 mg dm-³ of P, respectively. The accumulation of zinc in the dry matter of the Gliricidia sepium and of the sorghum decreased in a quadratic way with increase of the doses of P, with minimum point of 120 mg dm-³ of P for the Gliricidia sepium and of 129 mg dm-³ of P for the sorghum