A avaliação de doses de zinco e boro no algodoeiro herbáceo sob condições de sequeiro.

Abstract

cotton growing is one of the most important crops to Semi-arid Northeast. As in any semi-arid zone, soils have their deficiencies, that might affect yield and fiber quality. Aiming these aspects, a trial was conducted to study, under field conditions, the effect of some leveis of zinc and boron fertilization, on growth, development, yield and some fiber characteristics of annual cotton (Gossypium hirsutum L. - cv. BRS-2001).It was conducted at Embrapa Algodão Experimental Field, located at Missão Velha Municipality, Cariri Region, Ceará State, in the period February-June/2003, in a franc-sandy soil. It was composed of 17 treatments in a randomly complete block design, distributed in a 4 x 4 + 1 factorial arrangement, involving four leveis of boron (0; 2; 4 and 6 kg.ha"1) as boric acid (17% of B) combined with four leveis of zinc (0,0; 0,4; 0,8 and 1,2 kg.ha_1) as zinc sulphate (20% of Zn), in addition to testimony that received only NPK fertilization. Four repetitions were used, totalizing 68 plots. Plot area was 20,0 m2 (4 x 5 m), with four crop lines, but only two central lines were evaluated, composing a test area of 8 m2 (2 x 4 m). The following crop parameters were evaluated: Plant Height (PH), Canopy Diameter (CD) and Leaf Area Index (LAI) at 30, 60, 90 and 120 days after emergency (dae), Cotton Productivity (CP), 100 seeds weight (W/100), Lint yield (LY), Fiber percent (fiber %) and Boll Weight (BW). Some technological characteristics of fiber were also studied such as: Fcnp.lh (FF) and Length Uniformity (LU), Short Fiber Index (SFI), Resistance to Rupture (FRR) and Elongation (FE), Micronaire Index (MI), Refiectance (Rd), Yellowness Degree (+ b) and Spinning Ability (SA). Data showed that for PH, there was significam effect (P<0.05) of B leveis at 30 and 60 dae, of Zn leveis at Prof Dr. Napoleão Esberard de Macedo Beltrão ABSTRACT Brazilian Northeast is in second place in cotton production in Brazil. In addition, 120 dae, and of the interaction of B and Zn at 90 dae. For CD, there was quadratic and linear effect (P<0.01) of B leveis at 60 and 120 dae respectively, and linear effect (P<0.05) of Zn leveis at 90 and 120 dae. There was signifícant quadratic and linear eíTccl of 13 and Zn leveis on I.AI ut 60 and 90 dac. Ilowcvci, 11 and Zn fertilization liad no signifícant (P -0.05) cllccl on CP, W/100, LY and BW, but a linear effect was detected of Zn leveis on fiber %. Regarding technological characteristic of fiber parameters, there was linear effect of B leveis on Ml, + b and SA. Zn leveis had linear effect on LU and FE. Regarding paramclcr MAT, Ihcie was signifícant cflccls ainong cresceu! leveis of I) (P- 0.05) and Zn (P<0.01), respectively.