Crescimento vegetativo e coeficiente de cultura do feijoeiro relacionados a graus-dia acumulados

Abstract

RESUMO -Estudou-se o crescimento vegetativo e o coeficiente de cultura (k c ) do feijoeiro (Phaseolus vulgaris L.), relacionando-os ao índice de graus-dia acumulados (ΣG). O delineamento experimental foi o inteiramente casualizado com três tratamentos e quatro repetições. Os tratamentos de densidade populacional de plantas foram: cultura semeada em evapotranspirômetros a uma densidade de 50 plantas m -2 , com redução para 25 plantas m -2, quando alcançada a cobertura completa do solo; cultura semeada com densidades populacionais de 14 e 28 plantas m -2 em campo irrigado. Os parâmetros de crescimento da cultura, como a matéria seca total, a porcentagem de cobertura vegetal e o índice de área foliar mostraram uma relação altamente significativa com ΣG, tendo sido afetada pelos tratamentos e pelas condições de suprimento de água. A relação entre o coeficiente de cultura basal (k cb ) e ΣG foi altamente significativa para a cultura semeada nos evapotranspirômetros. No campo, o molhamento da superfície do solo após a chuva ou irrigação e o déficit hídrico moderado afetaram as correlações (r 2 ) entre k c e ΣG. Os tratamentos não alteraram os estádios fenológicos da cultura, quando correlacionados com graus-dia acumulados.Termos para indexação: Phaseolus vulgaris, irrigação, população de plantas, características agronômi-cas, cobertura vegetal, área foliar, matéria seca. VEGETATIVE GROWTH AND BEAN CROP COEFFICIENT AS RELATED TO ACCUMULATED GROWING-DEGREE-DAYSABSTRACT -The vegetative growth and the crop coefficient (k c ) for irrigated beans (Phaseolus vulgaris L.) was studied in relation to accumulated growing-degree-days (ΣG). A completely randomized design was used with three treatments and four replicates. Population density treatments were: crop sowed in evapotranspirometers at a density of 50 plants m -2 reduced to 25 plants m -2 , when the canopy achieved full ground cover; and crop sowed with population densities of 14 and 28 plants m -2 in irrigated field. Crop growth was evaluated considering dry matter, vegetative ground cover and the leaf area index. All traits had a highly significant relationship to ΣG, even though plant density and water supply conditions affected them. The relationship between the basal crop coefficient (k cb ) and ΣG was highly significant in the evapotranspirometers. In the field, the surface wetting after the rain or irrigation and the mild water deficits affected the correlations (r 2 ) between k c and ΣG. The phenological events of the plants studied were not affected by the treatment, when related to accumulated growingdegree-days.

Initial growth and development of southern sandbur based on thermal units

“…In the literature, Bt values = 0 o C are usually considered for weeds and crops in temperate climate, such as barley (Hordeum vulgare) and wheat (Triticum aestivum) (Cao & Moss, 1989;Kirkby, 1995;Shirtliffe et al, 2000;Ball et al, 2004), while for sunflower (Helianthus annuus), Granier & Tardieu (1998) (Kish & Ogle, 1980;Medeiros et al,. 2000), for corn crops (Gadioli et al, 2000), and for forage Panicum virgatum (Sanderson & Wolf, 1995 The ability to predict phenological stages, such as flowering and development and dispersal of weed seeds, may aid the development of management practices (Ghersa & Holt, 1995).…”

“…It is known that changes or physiological events that occur during plant development can be defined by numerical scales (Medeiros et al, 2000;Shirtliffe et al, 2000;Gadioli et al, 2000). These scales, most often, are defined as a function of time (days).…”

“…In addition, it enables a linear relationship between temperature increase and plant development (Gadioli et al, 2000;Gramig & Stoltenberg, 2007). Thus, mathematical models and simulation routines based on the concept of degree days can be used (Medeiros et al, 2000). This concept is no different for weeds, but few studies have assessed the development of these species based on accumulated degree days.…”

Growth and development of honey weed based on days or thermal units

“…It also admits a linear relationship between the temperature increase and the vegetal development (Gadioli et al, 2000). Therefore, it is possible to use mathematical models and simulations that adopt the concept of accumulated growing degree days (Medeiros et al, 2000).…”

“…Base temperatures around 10 o C have been registered for bean plant (Medeiros et al, 2000), corn (Gadioli et al, 2000) and switch grass Panicum virgatum (Sanderson & Wolf, 1995 an experiment conducted with a decreasing photoperiod (January-July/2011). Therefore, considering the phenological development in the proposed scales and data consistency (Table 1), and considering the fact that honey weed is dicotyledonous with photosynthetic cycle type C 3 and it is classified as an annual or biannual weed plant, the adequate base temperature, for future studies, is Tb = 10 o C.…”