Estimativa da área foliar do pepino em ambiente protegido por medidas lineares sob salinidade e enxertia

The measurement of leaf area by linear parameters is a useful tool when plants cannot be destroyed for direct measurement. The objectives of this study were to establish equations to estimate the leaf area of greenhouse-cucumber and to evaluate the effects of salinity and grafting on this estimative. Non-grafted cucumber seedlings, cv. 'Hokushin', were transplanted in a greenhouse and were irrigated with water of different salinities (1.0, 3.2 and 5.0 dS m-1). In the second growing period, the same cultivar was grafted on Cucurbita spp. and the plants were irrigated with water of 1.4, 3.0 and 5.3 dS m-1. Leaves of different sizes were collected from both experiments and leaf area was determined by an integrating area meter. Leaf length (L) and width (W) were also recorded. An equation for estimating the leaf area from L and W was developed for a given salinity level or grafting condition and estimated well the area of leaves collected in the other treatments. The leaf area (LA) of cucumber 'Hokushin' could be estimated using the equation LA = 0.88LW - 4.27, for any grafting and salinity conditions.A determinação da área foliar por medidas lineares é uma ferramenta útil quando as plantas não podem ser destruídas para que a medição direta seja realizada. Os objetivos desse trabalho foram definir equações para a estimativa da área foliar do pepino em ambiente protegido e avaliar os efeitos da salinidade e da a enxertia nessa estimativa. Mudas de pepino, cv. 'Hokushin', não enxertadas, foram transplantadas em um ambiente protegido e irrigadas com água de diferentes salinidades (1,0, 3,2 e 5,0 dS m-1). No segundo período de cultivo, a mesma cultivar foi enxertada sobre Cucurbita spp., sendo as plantas irrigadas com água de 1,4, 3,0 e 5,3 dS m-1. Foram coletadas folhas de diferentes tamanhos dos dois cultivos e dos três tratamentos e a área foliar foi determinada por um medidor de área foliar. O comprimento (C) e a largura (L) da folha também foram registrados. Desenvolveram-se equações pelas quais a área foliar pôde ser estimada a partir de medidas de C e L. A equação desenvolvida para um dado nível de salinidade ou condição de enxertia estimou bem a área das folhas coletadas nos demais tratamentos. A área foliar (AF) do pepino 'Hokushin' pode ser estimada pela função AF = 0,88CL - 4,27, para qualquer condição de enxertia e salinidade

Water relations and photosynthesis as criteria for adequate irrigation management in 'Tahiti' lime trees

Irrigation scheduling based on soil moisture status is one of the most useful methods because of its practicality and low cost. The effects of available soil water depletion on evapotranspiration (ETc), transpiration (E), leaf water potential at predawn (psiP) and midday (psiM), stomatal conductance (gs) and net CO2 assimilation (A) in lime 'Tahiti' trees (Citrus latifolia) were evaluated to improve irrigation schedule and minimize water use without causing water stress. The trees were spaced 7 <FONT FACE=Symbol>&acute;</FONT> 4 m and drip-irrigated by four drippers with the available soil water content (AWC) depleted by suspension of irrigation (40 days). Leaf water potential was measured on a pressure chamber (psiP and psiM) and leaf gas exchange was measured by infrared gas analyzer (E, gs and A). Evapotranspiration was determined with the aid of weighing lysimeter. Water soil content and potential (psiS) were monitored with TDR probes and tensiometers, respectively, installed at 0.3, 0.6 and 0.9 m depths. Meteorological variables were monitored with an automatic weather station in the experimental area. The threshold AWC level for the onset of ETc decline was 43%, and 60% for gs, A, E and Y P. Also, psiP was more sensitive to AWC than psiM, and is therefore a better tool for irrigation. When AWC was around 60%, values of psiP and psis were -0.62 MPa and -48.8 kPa, respectively

Efeito da variabilidade do armazenamento de agua no solo na qualidade da irrigacao por aspersao.

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Time Domain Reflectometry (tdr) Calibration For Estimating Soil Solution Concentration [calibração Da Reflectometria No Domínio Do Tempo (tdr) Para A Estimativa Da Concentração Da Solução No Solo]

Time Domain Reflectometry (TDR) is a reliable method for in-situ measurements of the humidity and the solution concentration at the same soil volume. Accurate interpretation of electrical conductivity (and soil humidity) measurements may require a specific calibration curve. The primary goal of this work was to establish a calibration procedure for using TDR to estimate potassium nitrate concentrations (KNO 3) in soil solution. An equation relating the electrical conductivity measured by TDR and KNO 3 concentration was established enabling the use of TDR technique to estimate soil water content and nitrate concentration for efficient fertigation management.261282291Bejat, L., Perfect, E., Quinsenberry, V.L., Coyne, M.S., Haszler, G.R., Solute transport as related to soil structure in unsaturated intact soil blocks (2000) Soil Science Society of America Journal, 64 (3), pp. 818-826. , MadisonCoelho, E.F., Or, D., Flow and uptake patterns affecting soil water sensor placement for drip irrigation management (1996) Transactions of the ASAE, 39 (6), pp. 2007-2016. , St. JosephGiese, K., Tiemann, R., Determination of the complex permittivity from thin-sample time domain reflectometry: Improved analysis of the step response waveform (1975) Advances in Molecular Relaxation Processes, 7 (1), pp. 45-59. , AmsterdamGupta, S.C., Hanks, R.J., Influence of water content on electrical conductivity of the soil (1972) Soil Science Society of America Journal, 36 (6), pp. 855-857. , MadisonMmolawa, K., Or, D., Root zone solute dynamics under drip irrigation: A review (2000) Plant and Soil, 222 (1-2), pp. 163-190. , DordrechtNadler, A., Estimating the soil water dependence on the electrical conductivity soil solution/electrical conductivity bulk soil ratio (1982) Soil Science Society of America Journal, 46 (4), pp. 722-726. , MadisonNadler, A., Field measurements of solute travel times using time domain reflectometry (1993) Soil Science Society of America Journal, 57 (3), pp. 878-879. , MadisonNadler, A., Discrepancies between soil solute concentration estimates obtained by TDR and aqueous extracts (1997) Australian Journal of Agricultural Research, 35 (3), pp. 527-537. , CollingwoodNadler, A., Gamliel, A., Peretz, I., Practical aspects of salinity effect on TDR-measurement water content: A field study (1999) Soil Science Society of America Journal, 63 (5), pp. 1070-1076. , MadisonRhoades, J.D., Raats, P.A., Prather, R.J., Effects of liquid phase electrical conductivity, water content and surface conductivity on bulk soil electrical conductivity (1976) Soil Science Society of America Journal, 40 (5), pp. 651-655. , MadisonRichards, L.A., Diagnosis and improvement of saline and alkali soils (1954) Agriculture Handbook, 60, 160p. , Washington: United Salinity LaboratorySilva, E.F.F., Duarte, S.N., Folegatti, M.V., Rojais, E.G., Utilização de testes rápidos e extratores de solução no solo na determinação de nitrato e potássio (2003) Engenharia Agrícola, 23 (3), pp. 460-467. , JaboticabalSouza, C.F., Or, D., Matsura, E.E., A variable-volume TDR probe for measuring water content in large soil volumes (2004) Soil Science Society of America Journal, 68, pp. 25-31. , MadisonTommaselli, J.T.G., Bacchi, O.O.S., Calibração de um equipamento de TDR para medida de umidade de solos (2001) Pesquisa Agropecuária Brasileira, 36 (9), pp. 1145-1154. , BrasíliaTopp, G.C., Davis, J.L., Annan, A.P., Electromagnetic determination of soil water content: Measurements in coaxial transmission lines (1980) Water Resources Research, 16 (3), pp. 574-582. , WashingtonWard, A.L., Kachanoski, R.G., Elrick, D.E., Analysis of water and solute transport away from a point source (1995) Soil Science Society of America Journal, 59 (3), pp. 699-706. , MadisonTime Domain Reflectometry Soil Sample Analysis Program, , http://soilphysics.usu.edu/wintd