Aiming to evaluate the effect of irrigation depths on fiber quality of upland cotton, an experiment was conducted from July to December 2010 in Barbalha-CE, Brazil. The treatments consisted of a factorial combination of two upland cotton cultivars (BRS Aroeira and BRS Araripe) and five irrigation depths (260.93, 418.93, 514.21, 711.81 and 894.68 mm), arranged in a split-plot design with four replicates. A line-source sprinkler irrigation system was used and irrigation depth in the control treatment was calculated according to the crop evapotranspiration. The analysed fiber quality variables were: fiber percentage, length, uniformity, short-fiber index, resistance, elongation at rupture, micronaire index, maturity, degree of yellowing, reflectance degree and count strength product (CSP) index. The irrigation depths influenced fiber length, short-fiber index, strength, micronaire index, maturity and reflectance degree. The cultivars influenced fiber percentage, length and color (degree of yellowing). The best results of fiber quality were found with irrigation depths of 514.21 and 418.93 mm for the upland cotton cultivars BRS Araripe and BRS Aroeira, respectively.

The objective of this study was to evaluate the effect of irrigation depths on seed cotton yield and water-use efficiency of cotton cultivars in the Brazilian semi-arid region. Field experiment was conducted during two consecutive years in the Apodi region, RN, using sprinkler irrigation. The experiment consisted of factorial combination in split-plots, composed of four irrigation depths (130; 100; 70 and 40% ETc and four cotton cultivars - FiberMax 993, BRS 286, BRS 336 and BRS 335), in randomized block design with 4 replicates. Data were evaluated by mean test (Tukey) and regression analysis. Considering the irrigation depths of 40% ETc, cotton yield was 48% lower compared to the higher irrigation depth (130% ETc). The higher water-use efficiency (0.69 kg m^-3) was obtained with 70% ETc irrigation depth. The highest seed cotton yield was achieved with the higher water depth for all evaluated cultivars. Yield response factor (Ky) was equal to 0.632, 0.711, 0.784 and 0.858, for FiberMax 993, BRS 286, BRS 335 and BRS 336 cultivars, respectively. FiberMax 993 and BRS 286 cultivars presented the best performance, showing that they are more suitable for irrigated farming in the semi-arid region.

Salt stress reduces the yield and quality of colored fiber cotton production, but this problem can be mitigated by the foliar application of hydrogen peroxide in adequate concentrations. In this context, the objective of the present study was to evaluate the production and characteristics of fibers of naturally colored cotton cultivares under irrigation with low- and high-salinity water and leaf application of hydrogen peroxide. The experiment was carried out in a greenhouse under a randomized block design, arranged in 4 × 3 × 2 factorial scheme, corresponding to four concentrations of hydrogen peroxide (0, 25, 50, and 75 μM), three cultivares of colored fiber cotton (‘BRS Rubi’, ‘BRS Topázio’, and ‘BRS Verde’), and two electrical conductivities of water (0.8 and 5.3 dS m⁻¹), with three replicates and one plant per plot. Irrigation with water of 0.8 dS m⁻¹ associated with a foliar application of 75 μM of hydrogen peroxide favored the lint and seed weight, strength, micronaire index, and maturity of ‘BRS Topázio’. The ‘BRS Rubi’ cotton cultivar showed higher tolerance to salinity, followed by the ‘BRS Topázio’ and ‘BRS Verde’ cultivares regarding the yield of seed cotton weight, with reduction below 20% under water of 5.3 dS m⁻¹.

Visando avaliar o crescimento e a capacidade produtiva de diferentes genótipos de gergelim em função de lâminas de irrigação, foi realizado um experimento na Estação Experimental da Embrapa, em Barbalha, CE, onde foram estudados cinco lâminas de irrigação e seus efeitos em três genótipos de gergelim. Esses fatores combinados resultaram em 15 tratamentos. O delineamento experimental foi em faixas, com quatro repetições, resultando em 60 unidades experimentais. Foi realizada análise de crescimento destrutiva com amostragens de 15 em 15 dias para avaliação de área foliar e fitomassa. As variáveis de crescimento foram estudadas em 10 plantas da área útil das parcelas. Ao final do ciclo foram avaliados a produção e seus componentes. Os maiores valores dos componentes de produção foram obtidos com a lâmina de 1026,50 mm. Com maior disponibilidade de água deve ser cultivada a cultivar BRS Seda e com menos água a linhagem ELAG09-27561. As lâminas de irrigação não afetam a acumulação de fitomassa nos órgãos das plantas. Os maiores teores de óleo são obtidos em plantas com baixa disponibilidade hídrica.

Desarrollo agronómico de algodón colorido influenciado por riego con aguas residuales domésticas y fertilización de potasio en la región semiárida de Brasil

CANOPY TEMPERATURES AND ACCUMULATED DEGREE DAYS ON COTTON PLANTS UNDER WATER DEFICIT JOÃO HENRIQUE ZONTA1; RUDAH MARQUES MANIÇOBA2; ZIANY NEIVA BRANDÃO3; MARIO ANASTASIO CARRILLO4 E JOSÉ RENATO CORTEZ BEZERRA5 1Embrapa Algodão, Rua Osvaldo Cruz, 1173, Centenário, Campina Grande – PB, CEP: 58428-095, e-mail: joao-henrique.zonta@embrapa.br 2Engenharia Agrícola, Universidade Federal Rural do Semiárido, Av. Francisco Mota, 572 - Bairro Costa e Silva, Mossoró - RN, CEP: 59625-900, e-mail: rudahmanicoba@gmail.com 3Embrapa Algodão, Rua Osvaldo Cruz, 1173, Centenário, Campina Grande – PB, CEP: 58428-095, e-mail: ziany.brandao@embrapa.br 4SmartFieldTM, Inc, n. 4617, 50th Street, Lubbock, Texas, 79414, e-mail: mario.carrillo@smartfield.com 5Embrapa Algodão, Rua Osvaldo Cruz, 1173, Centenário, Campina Grande – PB, CEP: 58428-095, e-mail: jose.cortez-bezerra@embrapa.br 1 ABSTRACT Canopy temperature is one of the best integrators of plant health and has been successfully used for irrigation scheduling. Therefore, the objective of this study was to evaluate the canopy temperature of cotton plants under water stress at different stages of the crop cycle and to determine the accumulated degree days based on canopy temperature. It was applied water deficit periods of 15 days at the following phenological stages: First Square, First Flower, Peak Bloom and Opening Bolls and control treatment. Canopy temperature was obtained using SmartCrop® wireless infrared temperature sensors. The results showed higher canopy temperatures during water deficit periods. For water deficit periods, canopy temperature values were always above the optimum temperature for cotton metabolism. As a result of the stress caused by water deficit, cotton yield was significantly reduced, with the higher yield loses recorded when applied deficit occurred during flowering stages (beginning and peak). Accumulated degree days also varied according to water stress, with a shortened phenological cycle for treatments with water deficit in comparison to the control without stress. The period for fiber thickening was also influenced by the variation in canopy temperature due to water stress, which may reflect decline in fiber quality. Keywords: Irrigation; Phenological cycle; Stress; Environmental conditions; Infrared thermometry. ZONTA, J. H.; MANIÇOBA, R. M.; BRANDÃO, Z. N.; CARRILLO, M. A. E BEZERRA, J. R. C. TEMPERATURA DO DOSSEL E GRAUS DIA ACUMULADOS EM ALGODOEIRO SOB DÉFICIT HÍDRICO 2 RESUMO A temperatura do dossel é um dos melhores assimiladores da saúde das plantas e tem sido usada com sucesso para manejo da irrigação. O objetivo deste estudo foi avaliar a temperatura do dossel do algodoeiro sob déficit hídrico em diferentes estágios fenológicos e determinar os graus dia acumulados a partir da temperatura do dossel. Foram aplicados períodos de déficit hídrico de 15 dias nos seguintes estádios fenológicos: Botão floral, Início do florescimento, Pico do...