The Penman-Monteith (PM) equation is a state-of-the-art modelling approach to simulate evapotranspiration (ET) at site and local scale. However, its practical application is often restricted by the availability and quality of required parameters. One of these parameters is the canopy conductance. Long term measurements of evapotranspiration by the eddy-covariance method provide an improved data basis to determine this parameter by inverse modelling. Because this approach may also include evaporation from the soil, not only the ‘actual’ canopy conductance but the whole surface conductance (gc) is addressed. Two full cycles of crop rotation with five different crop types (winter barley, winter rape seed, winter wheat, silage maize, and spring barley) have been continuously monitored for 10 years. These data form the basis for this study. As estimates of gc are obtained on basis of measurements, we investigated the impact of measurements uncertainties on obtained values of gc. Here, two different foci were inspected more in detail. Firstly, the effect of the energy balance closure gap (EBCG) on obtained values of gc was analysed. Secondly, the common hydrological practice to use vegetation height (hc) to determine the period of highest plant activity (i.e., times with maximum gc concerning CO2-exchange and transpiration) was critically reviewed. The results showed that hc and gc do only agree at the beginning of the growing season but increasingly differ during the rest of the growing season. Thus, the utilisation of hc as a proxy to assess maximum gc (gc,max) can lead to inaccurate estimates of gc,max which in turn can cause serious shortcomings in simulated ET. The light use efficiency (LUE) is superior to hc as a proxy to determine periods with maximum gc. Based on this proxy, crop specific estimates of gc,maxcould be determined for the first (and the second) cycle of crop rotation: winter barley, 19.2 mm s−1 (16.0 mm s−1); winter rape seed, 12.3 mm s−1 (13.1 mm s−1); winter wheat, 16.5 mm s−1 (11.2 mm s−1); silage maize, 7.4 mm s−1 (8.5 mm s−1); and spring barley, 7.0 mm s−1 (6.2 mm s−1).

The Penman-Monteith (PM) equation is a state-of-the-art modelling approach to simulate evapotranspiration (ET) at site and local scale. However, its practical application is often restricted by the availability and quality of required parameters. One of these parameters is the canopy conductance. Long term measurements of evapotranspiration by the eddy-covariance method provide an improved data basis to determine this parameter by inverse modelling. Because this approach may also include evaporation from the soil, not only the ‘actual’ canopy conductance but the whole surface conductance (gc) is addressed. Two full cycles of crop rotation with five different crop types (winter barley, winter rape seed, winter wheat, silage maize, and spring barley) have been continuously monitored for 10 years. These data form the basis for this study. As estimates of gc are obtained on basis of measurements, we investigated the impact of measurements uncertainties on obtained values of gc. Here, two different foci were inspected more in detail. Firstly, the effect of the energy balance closure gap (EBCG) on obtained values of gc was analysed. Secondly, the common hydrological practice to use vegetation height (hc) to determine the period of highest plant activity (i.e., times with maximum gc concerning CO2-exchange and transpiration) was critically reviewed. The results showed that hc and gc do only agree at the beginning of the growing season but increasingly differ during the rest of the growing season. Thus, the utilisation of hc as a proxy to assess maximum gc (gc,max) can lead to inaccurate estimates of gc,max which in turn can cause serious shortcomings in simulated ET. The light use efficiency (LUE) is superior to hc as a proxy to determine periods with maximum gc. Based on this proxy, crop specific estimates of gc,maxcould be determined for the first (and the second) cycle of crop rotation: winter barley, 19.2 mm s−1 (16.0 mm s−1); winter rape seed, 12.3 mm s−1 (13.1 mm s−1); winter wheat, 16.5 mm s−1 (11.2 mm s−1); silage maize, 7.4 mm s−1 (8.5 mm s−1); and spring barley, 7.0 mm s−1 (6.2 mm s−1).

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-06-19T20:20:01Z No. of bitstreams: 1 LIGIA SAMPAIO REIS - TESE PPGEA 2006..pdf: 39057759 bytes, checksum: b8a95f345aae5194c46d6f9979e44ece (MD5) / Made available in DSpace on 2018-06-19T20:20:01Z (GMT). No. of bitstreams: 1 LIGIA SAMPAIO REIS - TESE PPGEA 2006..pdf: 39057759 bytes, checksum: b8a95f345aae5194c46d6f9979e44ece (MD5) Previous issue date: 2006-12 / CNPq / O conhecimento sobre o crescimento das espécies cultivadas permite planejar e manejar de forma racional os cultivos, contribuindo para que as espécies consigam expressar todo seu potencial, além de fornecer dados para a construção de modelos matemáticos capazes de descrever a necessidade de água das culturas, através do conhecimento da evapotranspiração. O objetivo principal deste trabalho foi a caracterização energética e hídrica no desenvolvimento do tomate caqui em ambiente protegido, visando determinação da necessidade de água. Foram feitas as seguintes determinações: fluxos de calor sensível e latente pelos métodos do balanço de energia de Bowen e pelo método de Penman- Monteith; coeficiente da cultura através dos métodos de Linacre, Penman-Monteith e radiação; e evapotranspiração pelos métodos do balanço hídrico e Penman-Monteith. Durante o período experimental, foram tomadas medidas semanais de altura das plantas e comprimento e largura das folhas. Foram ajustados modelos para determinação do índice de área foliar, em função da largura e comprimento das folhas. Comparado ao modelo de Penman-Monteith, o modelo de Linacre subestimou os valores de ETo, quando o saldo de radiação (Rn) foi superior a 7,0 MJ m ; por outro lado, quando Rn ocorreu na faixa de 4 MJ m2 o método de Linacre superestimou a ETo. O saldo de radiação foi consumido em 71% para o fluxo de calor latente no interior do ambiente protegido, e em 15% para o fluxo de calor sensível. Apesar do comportamento dos dois métodos serem os mesmos, os valores encontrados pelo método do balanço hídrico foram maiores que os encontrados pelo método de Penman-Monteith. A relação Rgi e Rge permaneceu constante durante o ciclo com transmissividade de 89%, mostrando, portanto, redução de 18%, provocada pela cobertura de polietileno. A Rg apesar de mostrar uma concordância elevada, apresentou um maior erro quando comparada aos outros elementos, mostrando que existem diferenças significativas entre as mediadas obtidas dentro da estufa e as estimadas pelos dados externos. O valor médio de frutos por planta foi de 21,5, com uma produção de 3,04 kg planta e uma produtividade de 7,6 kg m" , totalizando uma produtividade de 76 t ha" , valor este maior que a média Nacional. Verificou-se, que o maior consumo de água ocorreu na fase reprodutiva. / The knowledge on growth of cultivated species allows to planning and to manage, in a rational way, the cultivations, contributing so that the species get to express ali its potential, besides supplying data for construction of mathematical models capable to describe the need of water by crops, through the knowledge of evapotranspiration. The main objective of this work was the energy and hydric characterization in the development of tomato kaki in greenhouse, seeking determination of the need of water. The following determinations were performed: sensitive and latent heat flows by the methods of energy balance of Bowen and by the method of Penman-Monteith; crop coefficient through the methods of Linacre, Penman-Monteith and radiation; and evapotranspiration by the methods of water balance and Penman-Monteith. During the experimental period, weekly measures of plants height and length and width of leaves were taken. Models were adjusted for determination of the foliar area index, in function of the width and length of the leaves. Compared to the model of Penman-Monteith, the model of Linacre underestimated the values of ETo, when the radiation balance (Rn) was superior to 7.0 MJ m" ; on the other hand, when Rn happened in the strip of 4 MJ m"2 the method of Linacre overestimated ETo. The radiation balance was consumed in 71% by the latent heat flow inside of the greenhouse, and in 15% by the sensitive heat flow. In spite of the behavior of the two methods be the same, the values found by the water balance method were larger than the ones found by the method of Penman- Monteith. The relationship Rgi and Rge stayed constant during the cycle with transmissivity of 89%, showing, therefore, reduction of 18%, provoked by the covering of polyethylene. The Rg, in spite of showing a high agreement, presented a larger error when compared to the other elements, showing that significant differences exist among the measures obtained inside of the greenhouse and the ones estimated by the externai data. The mean value of fruits per plant was of 21.5, with a production of 3.04 kg plant"1 and a productivity of 7.6 kg m"2, totaling a productivity of 76 t ha"1, which is a value larger than the National mean. It was verified that the largest water consumption happened in the reproductive phase.

GONÇALVES, Fabrício Mota. Evapotranspiração e coeficientes de cultivo (KC) da cana-de-açúcar irrigada por gotejamento subsuperficial. 2010. 64 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola, Fortaleza-CE, 2010. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-06-28T16:59:16Z No. of bitstreams: 1 2010_dis_fmgonçalves.pdf: 3900094 bytes, checksum: 1ad79acf1432c0de09bcbdf52cb0f8c3 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-06-28T16:59:48Z (GMT) No. of bitstreams: 1 2010_dis_fmgonçalves.pdf: 3900094 bytes, checksum: 1ad79acf1432c0de09bcbdf52cb0f8c3 (MD5) / Made available in DSpace on 2016-06-28T16:59:48Z (GMT). No. of bitstreams: 1 2010_dis_fmgonçalves.pdf: 3900094 bytes, checksum: 1ad79acf1432c0de09bcbdf52cb0f8c3 (MD5) Previous issue date: 2010 / Sugar cane is one of the crops with the highest level of water consumption, with a high evapotranspiration demand throughout most of its cycle. Knowledge of the sugar cane water demand, the time that irrigation should be applied, and how to irrigate the crop are becoming increasingly important for the sustainable development of irrigated sugar cane cultivation, especially in areas of low water availability, as it is the case in northea stern Brazil. The experiment was carried out at the Curu Experimental Field (property of the Embrapa Tropical Agroindustry), located in the Curu-Paraipaba Irrig ation Project, city of Paraipaba-CE (3 ° 29 '20''S, 39 ° 9' 45''W and elevation 30m), in order to determine the evapotrans piration and crop coefficients (Kc) of sugarcane (Saccharum L. officinarium), subsurface drip-irrigated. It was used the SP 6949 sugar cane variety, planted in a spacing of 1.8 m between double rows and 0.4 m between rows within the double row. As to t he irrigation, we used one lateral water line for each double row, buried at a depth of 0.15 m, w ith self-compensating drip emitters, with a flow rate of 1 L h-1, spaced 0.5 m on the water line. The crop was irrigated daily and there were three fertigations per week. The irrigation de pth was periodically adjusted, keeping the soil water potential between -8 kPa to -20 kPa. The crop evapotranspiration (ETc) was determined using a wei ghing lysimeter with a surface area of 2.25 m 2. The reference evapotranspiration (ETo) was estimated by the FAO Penman-Monteith method. The durations of the phenological stages of cane sugar were estimated through analysis of soil cover, with the use of digital images. Durations of 31, 49, 237 and 118 days were observed, respectively for initial, crop development, mid-season and late season stages. The yields achieved within and outside the lysimeter were respectively 144.4 and 108.8 t ha -1 . The total ETc observed during the cycle of the sugar cane was 1074.1 m m, with maximum values of 6.6 mm d-1 during the mid-season stage. Observed Kc values for initial, mid-season and late season stages were respectively 0.23, 1 .03 and 0.50. In the crop development stage, the relationship between Kc and the (crop) soil cover was represented with good accuracy by a negative quadratic model. / A cana-de-açúcar é uma das culturas com maior consumo de água, apresentando uma alta demanda evapotranspirativa ao longo da maior parte do seu ciclo. O conhecimento das necessidades hídricas da cana-de-açúcar, do momento de aplicação da água requerida pela mesma e a forma de aplicação torna-se cada vez mais importante para o desenvolvimento sustentável da sua produção irrigada, principalmente em regiões de pouca disponibilidade hídrica, como é o caso da região Nordeste do Brasil. O experimento foi conduzido no Campo Experimental do Curu, pertencente à Embrapa Agroindústria Tropical localizado no Perímetro Irrigado Curu-Paraipaba, município de Paraipaba-CE (3° 29’ 20’’ S, 39° 9’ 45’’ W e altitude de 30 m), com o objetivo de determinar a evapotranspiração e os coeficientes de cultivo (Kc) da cana-de-açúcar (Saccharum officinarium L.), irrigada por gotejamento subsuperficial. Utilizou-se a variedade de cana SP 6949, plantada no espaçamento de 1,8 m entre fileiras duplas e 0,4 m entre linhas dentro da fileira dupla. Na irrigação utilizou-se uma linha lateral para cada fileira dupla, enterrada na profundidade de 0,15 m, com gotejadores autocompensantes, com vazão de 1 L h-1, espaçados de 0,5 m na linha. A cultura foi irrigada com freqüência diária e foram realizadas três fertirrigações por semana. A lâmina de irrigação foi ajustada periodicamente, mantendo-se o potencial de água no solo entre -8 kPa e -20 kPa. A evapotranspiração da cultura (ETc) foi determinada utilizando-se um lisímetro de pesagem com área superficial de 2,25 m2. A evapotranspiração de referência (ETo) foi estimada pelo método FAO Penman-Monteith. As durações das fases fenológicas da cana-de-açúcar foram estimadas por meio da análise da cobertura do solo pela cultura, determinada com o uso de imagens digitais. Foram observadas durações de 31, 49, 237 e 118 dias, para as fases inicial, de desenvolvimento, intermediária e final, respectivamente. A produtividade alcançada dentro e fora do lisímetro foi de 144,4 e 108,8 t ha-1, respectivamente. A ETc total observada durante o ciclo da cana-de-açúcar foi de 1.074,1 mm, com valores máximos da ordem de 6,6 mm d-1 durante a fase intermediária. Foram observados valores de Kc iguais a 0,23, 1,03 e 0,50, para as fases inicial, intermediária e final, respectivamente. Na fase de desenvolvimento vegetativo a relação entre o Kc e a cobertura do solo pela cultura foi representada com bastante exatidão por um modelo quadrático negativo.