Identification of drought-tolerant corn genotypes by multivariate analysis

The identification of genotypes that are tolerant to water deficit is crucial for the maintenance of the agricultural production. This study aimed to evaluate the genotypic variation for drought tolerance among corn genotypes by means of multivariate analysis, as well as to identify hybrids with high grain yield under conditions of water deficit and full irrigation. For this purpose, an experiment was conducted in a randomized block design, with 36 corn hybrids, being 34 experimental elite and two commercial (controls) hybrids, under water deficit and full irrigation, during the reproductive stage, with four replications. The irrigation levels, added to the rainfall, totaled 691.6 mm under full irrigation and 490.8 mm under water deficit. The evaluation encompassed the leaf area index, leaf chlorophyll content, interval between male and female flowering, number of rows per ear, number of grains per ear, ear length, 100-grain weight, ear yield, ear index, total number of grains, number of ears per m2, grain yield at 13 % of moisture and water-use efficiency. The evaluated hybrids showed useful genetic diversity for drought tolerance. Four experimental elite hybrids (3G7395, 3G7415, 1G7034 and 3G7335) stood out under water deficit, showing a high grain yield performance, if compared to the average of the control hybrids

Irrigation Management in Real Time for Arugula Crop in Sergipe

The management of the irrigation is fundamental for success of leaves vegetables production. The work was carried out aiming to evaluate the production response of the arugula (Eruca sativa Mill.) under different irrigation levels at 25, 31, 37 and 43 days after sowing. The treatments were distributed in randomized blocks design with four replication, and evaluated in split-plot scheme of 4 4, with the plots constituted by four irrigation levels equivalent to reference evapotranspiration (ET0) at 50%, 75%, 100% and 125% estimated by Penman-Monteith equation; and the split-plot constituted by days after sowing. The arugula planting was established in November of 2008 with direct sowing in nursery with 0.1 m 0.2 m per plant, using the cv. “Folha Larga”. After the germination phase was carried out crop management necessary to the crop production. It was analyzed: plant height (cm), leaf number, fresh weight (g m-2) and dry weight (g m-2). The results showed the significant differences at level of 5% of probability for the Scott-Knott test for all variables analyzed after 37 days of planting. The results permit to infer that the irrigation levels exert influence under the studied variables with the higher efficiency of water use found for levels of 75% and 100% of the reference evapotranspiration

Optimal irrigation strategies for watermelon crop

O trabalho teve como objetivo determinar estratégias ótimas de irrigação para a cultura da melancia (Citrullus lanatus Thumb. Mansf.), considerando a água como fator limitante da produção e diferentes valores para o preço do produto e custos da energia elétrica. Utilizou-se uma função de produção quadrática e função de custo linear obtidas para as condições edafoclimáticas dos Tabuleiros Costeiros do Piauí. A irrigação com déficit proporcionou as maiores rendas líquidas, com significativa economia de água, no intervalo de variação de preços do produto de US$0,05 kg-1 a US$ 0,35 kg-1, nas três formas de tarifação da energia elétrica. Acima desse intervalo, deve-se utilizar a lâmina que maximiza a produção de frutos.This paper aimed to determine optimal strategies for irrigation management watermelon crop (Citrullus lanatus Thumb. Mansf.), when water is limiting resource under different values of the crop and electrical energy price. The analysis involved quadratic production function and linear cost function developed to the soil and climate characteristics of the Coastal Tablelands, at Piauí State, Brazil. The highest net incomes were achieved with deficit irrigation, in the range crop prices of the US$0.05 kg-1 to US$ 0.35 kg-1, independently of electrical energy price. Up this range, irrigation depth that maximizes fruits yield must be used

Effect of water regimes and plant densities on cowpea production

Cowpea has been cultivated in a rudimentary form in the main producing regions of Brazil, resulting in lower grain yields, when compared to the crop potential. The use of technologies such as water regimes, adequate plant density and soil management are alternatives to increase this crop yield. This study aimed at evaluating the effects of different water regimes and plant densities on the yield components of cowpea cultivated under conventional and no-tillage systems. A randomized block design in a split-plot factorial, with four replications, was used. The treatments consisted of five water regimes in the plots (157.00 mm, 189.00 mm, 234.00 mm, 274.00 mm and 320.00 mm) and five plant densities as subplots (12 plants m-2, 16 plants m-2, 20 plants m-2, 24 plants m-2 and 28 plants m-2). The evaluated variables were: number of pods per plant, number of pods per area, pod length and grain yield. The combination between 270 mm of irrigation water depth with a density of 280,000 plants ha-1 resulted in higher grain yield using the no-tillage system, while the combination between the density of 280,000 plants ha-1 and 320 mm of water depth favored the highest grain yields in the conventional growing system

Morfofisiologia do milho irrigado com e sem déficit hídrico sob diferentes arranjos de plantas na região meio-norte do Piauí

Alterações no arranjo de plantas pode influenciar diretamente as características morfosiológicas e a produtividade das culturas, sobretudo em condições de déficit hídrico. O trabalho teve como objetivo analisar os efeitos de diferentes espaçamentos entre linhas e densidades de plantio na morfofisiologia do hibrido de milho AG-1051 submetido a diferentes regimes hídricos na região Meio-Norte do Piauí, Brasil. Foram implantados dois experimentos, em ambos se adotou o delineamento experimental de blocos casualizados em fatorial 5 x 2, combinando-se cinco densidades de plantio (20.000; 40.000; 60.000; 80.000 e 100.000 plantas ha-1), dois espaçamentos entre fileiras (0,5 e 1,0 m), com quatro repetições. Foi utilizado o sistema de irrigação por aspersão e as lâminas calculadas com base na evapotranspiração da cultura (ETc). Em irrigação plena utilizou-se 100% da ETc e em déficit hídrico 50% da ETc. Avaliaram-se altura de planta, altura de espiga, diâmetro do colmo, índice de área foliar, matéria seca, taxa de assimilação líquida de CO2, transpiração e condutância estomática. Em irrigação plena observa-se incremento linear na altura de planta e altura da espiga, enquanto sob condições de déficit hídrico, observa-se ajuste quadrático com altura máxima de 192,4 e 118,6 cm atingida na densidade de 85.000 e 80.000 plantas ha-1. Há ajuste linear negativo no diâmetro do colmo e na matéria seca em ambos os regimes hídricos adotados. O aumento da densidade de plantas aumenta a altura de planta, altura de espiga e diminui o diâmetro de colmo. Além disso promove redução da taxa de transpiração, da condutância estomática e da taxa de assimilação líquida de CO2. A redução do espaçamento entre plantas na linha em maiores densidades promove aumento do índice de área foliar e redução da matéria seca. Em condições de estresse hídrico os componentes fisiológicos apresentam as mesmas tendências em condições de irrigação plena, porém com redução expressiva dos índices

Irrigation, nitrogen and potassium levels under subsurface drip on sugarcane

O objetivo deste trabalho foi definir os níveis ótimos de irrigação, nitrogênio e potássio em cana‑de‑açúcar, cultivar RB867515, aplicados por gotejamento subsuperficial, em ciclo de primeira soca, para máxima produção de colmos, açúcar e álcool. O experimento foi realizado em Plintossolo do Município de União, no Estado do Piauí, durante o ano agrícola 2008/2009. Os tratamentos consistiram de: níveis de irrigação mais precipitação (W1, 767,5; W2, 898,5; W3, 971,0; W4, 1.053,0; e W5, 1.154,0 mm) e níveis de adubação nitrogenada e potássica (N1, 44,0; N2, 78,0; N3, 111,0; N4, 144,0; N5, 178,0; K1, 44,0; K2, 67,0; K3, 89,0; K4, 111,0; e K5, 133,0 kg ha-1). Utilizou-se o delineamento experimental de blocos ao acaso, com duas repetições, em arranjo fatorial fracionário 1/5 de 5x5x5 (W x N x K). A produtividade máxima de colmos (207,4 Mg ha-1) é alcançada com a aplicação de 1.154,0 mm de água, associada a 114,2 kg ha-1 de N e 60,1 kg ha-1 de K2O. A máxima produtividade de açúcar (25,3 Mg ha-1) e de álcool (20,0 m3 ha-1) é obtida com 1.154,0 mm, associada à aplicação dos níveis de 90,0 kg ha-1 de N e de 60,0 kg ha-1 de K2O.The objective of this work was to define the optimal irrigation, nitrogen and potassium levels insugarcane, cultivar RB867515, applied by subsurface drip, in the first ratoon, to maximize stem, sugar andalcohol yield. The experiment was carried out on Plinthaquox soil in the county União, Piauí State, Brazil,during the 2008/2009 agricultural season. The treatments consisted of: irrigation levels including rainfall (W1,767.5; W2, 898.5; W3, 971.0; W4, 1,053.0; and W5, 1,154.0 mm) and nitrogen and potassium levels (N1, 44.0;N2, 78.0; N3, 111.0; N4, 144.0; N5, 178.0; K1, 44.0; K2, 67.0; K3, 89.0; K4, 111.0; and K5, 133.0 kg ha-1).The experimental design used was a randomized complete block with two replicates, in a 5x5x5 (W x N x K)1/5 fractional factorial arrangement. Maximum stem yield (207.4 Mg ha-1) is reached with 1,154.0 mm of waterassociated with 114.2 kg ha-1 of N and 60.1 kg ha-1 of K2O. Maximum sugar (25.3 Mg ha-1) and alcohol (20.0 m3ha-1) yield is achieved with 1,154.0 mm associated with levels of 90.0 kg ha-1 of N and 60.0 kg ha-1 of K2O

Armazenamento de água em Plintossolo Argilúvico cultivado com cana-de-açúcar sob níveis de palhada

The objective of this work was to evaluate water storage in a Plinthaqualf under different straw levels during the fourth ratoon season of a sugarcane (Saccharum officinarum) crop. The study was conducted in the 2013/2014 crop season, with the cultivar SP-813250, at two soil depths (0.0–0.3 and 0.3–0.6 m), in a randomized complete block design, with five straw levels (0.0, 4.2, 9.5, 13.0, and 18.4 Mg ha-1) and four replicates. Soil moisture content was monitored with a time-domain reflectometer. The straw provided gains of up to 20 Mg ha-1 stems and kept increased water storage in the soil, in comparison with the soil without straw, in all evaluated periods. Maintenance of up to 50% (9.5 Mg ha-1) of sugarcane straw on soil surface promotes better water retention in the soil per Mg of straw added and delays the reach of critical water storage in the soil by up to 11 days, when compared with soil without straw cover.O objetivo deste trabalho foi avaliar o armazenamento de água em um Plintossolo Argilúvico sob diferentes níveis de palhada durante o ciclo de quarta soca da cana-de-açúcar (Saccharum officinarum). O estudo foi conduzido na safra 2013/2014, com a cultivar SP-813250, em duas profundidades (0,0‒0,3 e 0,3‒0,6 m), em delineamento de blocos ao acaso, com cinco níveis de palhada (0,0, 4,2, 9,5, 13,0, e 18,4 Mg ha-1) e quatro repetições. A umidade do solo foi monitorada com reflectômetro de domínio de tempo. A palhada proporcionou ganho de até 20 Mg ha-1 de colmos e manteve o solo com maior armazenamento de água do que o sem palhada, em todos os períodos avaliados. A manutenção de até 50% (9,5 Mg ha-1) de palhada de cana-de-açúcar sobre a superfície do solo promove melhor conservação de água no solo por Mg de palha adicionada e retarda em até 11 dias o alcance do armazenamento crítico de água no solo, em comparação ao solo sem cobertura de palha

Ischemic stroke caused by large-artery atherosclerosis: a red flag for subclinical coronary artery disease

BackgroundThe coronary calcium score (CAC) measured on chest computerized tomography is a risk marker of cardiac events and mortality. We compared CAC scores in two multiethnic groups without symptomatic coronary artery disease: subjects in the chronic phase after stroke or transient ischemic attack and at least one symptomatic stenosis ≥50% in the carotid or vertebrobasilar territories (Groupathero) and a control group (Groupcontrol).MethodsIn this cross-sectional study, Groupathero included two subgroups: GroupExtraorIntra, with stenoses in either cervical or intracranial arteries, and GroupExtra&Intra, with stenoses in at least one cervical and one intracranial artery. Groupcontrol had no history of prior stroke/transient ischemic attacks and no stenoses ≥50% in cervical or intracranial arteries. Age and sex were comparable in all groups. Frequencies of CAC ≥100 and CAC > 0 were compared between Groupathero and Groupcontrol, as well as between GroupExtraorIntr, GroupExtra&Intra, and Groupcontrol, with bivariate logistic regressions. Multivariate analyses were also performed.ResultsA total of 120 patients were included: 80 in Groupathero and 40 in Groupcontrol. CAC >0 was significantly more frequent in Groupathero (85%) than Groupcontrol (OR, 4.19; 1.74–10.07; p = 0.001). Rates of CAC ≥100 were not significantly different between Groupathero and Groupcontrol but were significantly greater in GroupExtra&Intra (n = 13) when compared to Groupcontrol (OR 4.67; 1.21–18.04; p = 0.025). In multivariate-adjusted analyses, “Groupathero” and “GroupExtra&Intra” were significantly associated with CAC.ConclusionThe frequency of coronary calcification was higher in subjects with stroke caused by large-artery atherosclerosis than in controls