The leaf area determination are extremely important in agronomic and physiological studies, as they provide valuable information in vegetable metabolism, methods used for this purpose should be accurate. This study aimed to develop polynomial models to estimate leaf area (LA). The methods used were leaf discs and ImageJ^(r) software, with measures of length (L), width (W), and relationship between length times width (LW) in leaves of the bell pepper crop in two field trials with two hybrids: Arcade and Impacto, as well as, the correlation of values found when using the two methods. Through a random sampling, 560 leaves from each hybrid were selected, at different stages of crop growth. Regression analysis of LA versus measures L, W and LW were performed by linear and quadratic models. The variable that best estimated LA was the relationship between LW with linear model (r²=0.98). Measurements of length and width of leaves presented adjustment to quadratic model r²=0.93 and r²=0.91, respectively. The integrator model for all samples and both hybrids was: LA=0.57×LW. The destructive method of leaf discs showed high correlation (r²=0.99) with the non-destructive method of ImageJ^(r) software.

Uma topossequência apresenta solos com características estruturais e morfológicas distintas que podem alterar a susceptibilidade à deformação estrutural em curtas distâncias espaciais. Os objetivos deste estudo foram avaliar a capacidade de suporte de carga e a suscetibilidade à compactação e mensurar o efeito que cargas acima e abaixo da pressão de preconsolidação causam na permeabilidade ao ar de solos numa topossequência da Depressão Central do Rio Grande do Sul, Brasil. Amostras indeformadas foram coletadas nos horizontes de três perfis de Argissolos (Ap, A1, AB, BA, Bt1 e Bt2; Ap, A1, A2, AB, BA, Bt1 e Bt2; e Ap, A1, BA, Bt1 e Bt2) e dois de Gleissolos (A1, A2, Bg; A, Bg e Cg), no longo de uma topossequência. Essas amostras foram submetidas ao teste de compressão uniaxial, sendo avaliada a permeabilidade ao ar antes e após compressão. Na condição de capacidade de campo, os Gleissolos apresentaram menor suscetibilidade à compactação e maior capacidade de suporte de carga que os Argissolos. O teor de argila esteve diretamente correlacionado com a capacidade de suporte de carga. Portanto, foi inversamente proporcional à suscetibilidade à compactação, exceto em condições de elevada umidade do solo quando a água lubrificou as superfícies aumentando a susceptibilidade à compactação de quaisquer solos. Até 25 kPa de carga ao solo não resultou degradação física do solo, mas quando foram aplicadas cargas de 200 kPa, mesmo na condição de capacidade de campo, houve redução significativa do volume de macroporos e porosidade total em níveis inferiores ao limite crítico (0,10 m³ m^-3).

This study aims to evaluate the effects of supplemental irrigation in bell pepper crop under shade mesh and in open-field to improve management of water resources. The experimental design was a randomized complete block with four replications and ten treatments in factorial arrangement (five irrigation levels combined with two shade levels). Irrigation treatments were 0.25, 0.50, 0.75 and 1.0 rate of crop evapotranspiration and the control (no supplemental irrigation). Shading treatments were 0 and 50% reduction of photosynthetically active radiation, compared to open field conditions. Crop coefficient was influenced by rainfall, especially during initial growth stage period when it was high and Kc values were 0.71, 1.17, and 0.92. Treatments under shade and open-field had no significant interaction effect, alike between the years of study. The yield in open-field and under shade mesh showed better performance in 0.75 and 0.50 of ETc, respectively. Maximum water productivity and irrigation water productivity was obtained in open-field and deficit irrigation plots. Under shade, highest fruit quality was obtained; heavier fruits, less dry matter, no sunscald and increasing value added to production. Comparing water consumption in open-field and shading, it can be obtained up to 14 to 25% water saving, significantly improving yield and fruit quality. Key words: Capsicum annuum, dual crop coefficient, drip irrigation, strategies for efficient irrigation.

This study aims to evaluate the effect of supplemental irrigation levels on vegetative parameters of bell pepper grown in open field and under shade mesh. The experimental design was a randomized complete block with four replications and ten treatments in factorial scheme (four irrigation levels combined with shade). Irrigation treatments consisted in 0.25, 0.50, 0.75 and 1.0 rate of crop evapotranspiration and the control (no-irrigation).Shading treatment was of 50% reduction of the photosynthetically active radiation compared to open field conditions. Vegetative parameters were influenced by irrigation. The growth rate of plants present no significant difference. The growth rate of stem diameter present difference, being treatments 0.50 and 0.75 the highest.Significant interaction was present in the rate of chlorophyll, dry matter, leaf area index and number of leaves per plant. Plots under shade mesh showed the highest growth rate in plant height and stem diameter and leaf area index, number of leaves per plant, dry matter and lower chlorophyll index. As irrigation strategy, considering the water use efficient and vegetative characteristics of bell pepper, the most favorable irrigation levels were 0.5 and 0.75 of ETc, under shade and in open field, respectively, without affecting the vegetative parameters and yield. Key words: Capsicum annuum, water stress, water use efficiency, drip irrigation.