Philosophiae Doctor - PhD / Water availability and climate related issues are some of the greatest crop production risks to irrigated agriculture in arid regions. In South Africa, for example, the increasing frequency and severity of droughts related to climate change and the growing competition for limited water resources among different users threaten the sustainability and growth of irrigated agriculture, especially the water-intensive fruit industry. Major fruit such as apples (Malus domestica Borkh) are produced entirely under irrigation in South Africa. As a result, there has been considerable research to accurately quantify the water requirements of fruit tree orchards in order to maximize water productivity.

By using the Soil Conservation Service (SCS) “polynomial” method for corn in the Mississippi Irrigation Scheduling Tool (MIST), the total number of irrigations required during the growing season can be reduced depending on the variety, growing degree days required to reach maturity, and the length of the growing season. Results showed that even though the SCS method called for irrigations earlier in the season, the method did not trigger irrigation events after the crop reached physiological maturity. In addition, although changing the timing of model initiation (planting vs emergence) was not important on the total crop water use, it may have other benefits. Lastly, Watermark 200SS sensors generally did not trigger similar irrigation events, especially around the mid-season, but shallower sensors somewhat matched and showed similar trends with the MIST modeled results and irrigation records. Therefore, using MIST with sensors may be beneficial when making precise irrigation scheduling decisions.

Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Shiraz/110R grapevines, growing in a fine sandy loam soil in the Breede River Valley, were subjected to ten different drip irrigation strategies during the 2006/07, 2007/08 and 2008/09 seasons. Grapevines of the control treatment (T1) were irrigated at 30% to 40% plant available water (PAW) depletion throughout the growing season. Grapevines of three treatments were irrigated at 70% to 80% PAW depletion from bud break until véraison (i.e. when ca. 95% of grape berries have changed colour), followed by either irrigation at 30% to 40% PAW depletion (T2) or a continuous deficit irrigation (CDI) strategy (T3) or irrigation at 70% to 80% PAW depletion (T4) during ripening. The CDI strategy was obtained by applying ca. half the volume of water that was applied to the control. This allowed the soil to dry out gradually between physiological stages (i.e. bud break and véraison or véraison and harvest). Grapevines of three further treatments were irrigated at ca. 90% PAW depletion from bud break until véraison, followed by irrigation at 30% to 40% PAW depletion (T5) or a CDI strategy (T6) or irrigation at ca. 90% PAW depletion (T7) during ripening. Grapevines of two treatments were irrigated by means of a CDI strategy from bud break until véraison. For both treatments, the soil water content (SWC) was allowed to dry out gradually until ca. 90% PAW depletion was reached. After véraison, the SWC of the one treatment was maintained at ca. 90% PAW depletion by applying only four small irrigations of three hours each during ripening (T8). The soil of the other treatment, received an irrigation at véraison to refill the SWC to field capacity (T9) followed by the CDI strategy during ripening. Grapevines of the tenth treatment were irrigated at ca. 90% PAW depletion between bud break and véraison followed by a partial profile refill (PPR) strategy during ripening (T10). In order to obtain the PPR strategy, SWC was only maintained between 40% and 60% PAW depletion. Evapotranspiration varied between 3.5 mm/day and 0.1 mm/day for driest and wettest treatments, respectively, during the period between December and February. This was substantially less than the volumes required for full surface irrigation. For irrigations applied at 30% to 40% PAW depletion (T1), 70% to 80% PAW depletion (T4) and ca. 90% PAW depletion (T7) levels throughout the season, crop coefficients for the Penman-Monteith reference evapotranspiration (ETo) were 0.4, 0.2 and 0.1, respectively. Under the given conditions, the different irrigation strategies did not have any effect on root distribution and density. Shoot growth of grapevines exposed to high to severe water deficits in the pre-véraison period stopped before mid December. Shoots of grapevines that were exposed to high or severe water deficits before véraison followed by more frequent irrigation during ripening showed active re-growth. These trends occurred during all the seasons. The level of PAW depletion reflected strongly in the plant water potential in the grapevines. Leaf water potential was influenced by the prevailing atmospheric conditions, whereas stem water potential was less sensitive to atmospheric conditions, but responded more directly to soil water availability. Due to the good relationships between pre-dawn leaf, mid-day leaf, mid-day stem and total diurnal water potential, it was possible to re-classify the water status in terms of previous classifications for these water potentials based on pre-dawn measurements. Water constraints in T1, T2 and T5 grapevines were classed as experiencing no stress, whereas the T7 and T8 ones experienced strong to severe water constraints before harvest. High frequency irrigation strategies during ripening delayed sugar accumulation due to dilution of sugar in the larger berries. Except for the wettest strategy, and where grapevines were subjected to the CDI strategy throughout the season, berry mass increased during ripening, i.e. from véraison to harvest. Water deficits had a negative effect on berry mass, bunch size and yield. Where higher soil water depletion levels were allowed, irrigation strategies had a positive effect on the irrigation water productivity of grapevines compared to the frequently irrigated or CDI strategies. Higher water constraints in grapevines, particularly during ripening, improved sensorial wine colour and enhanced some of the more prominent wine aromas, e.g. spicy and berry. Grapevines that were irrigated at a high frequency during ripening produced wines with diluted character flavours and aromas and inferior overall quality. Under the given conditions, sensorial wine colour and spicy character were the dominant factors in determining overall sensorial wine quality. / AFRIKAANSE OPSOMMING: Shiraz/110R wingerdstokke in ‘n fyn sandleem grond in die Breede Rivier vallei is gedurende die 2006/07, 2007/08 en 2008/09 seisoene met tien verskillende drupbesproeiingstrategieë besproei. Wingerdstokke van die kontrole (B1) is deur die seisoen by 30% to 40% plant beskikbare water (PBW) onttrekking besproei. Drie behandelings is tussen bot en deurslaan (wanneer ca. 95% van die korrels verkleur het) by 70% tot 80% PBW onttrekking besproei, gevolg deur besproeiing by 30% tot 40% PBW onttrekking (B2), ‘n deurlopende tekort besproeiing (DTB) strategie (B3) of besproeiing by 70% tot 80% PBW onttrekking (B4) gedurende rypwording. In die geval van die DTB strategie is ongeveer die helfte van die volume water toegedien wat by die kontrole toegedien is. Laasgenoemde strategie het die grond toegelaat om geleidelik tussen fisiologiese fases (i.e. tussen bot en deurslaan of tussen deurslaan en oes) uit te droog. Drie ander behandelings is by ca. 90% PBW onttrekking tussen bot en deurslaan besproei, gevolg deur besproeiing by 30% tot 40% PBW onttrekking (B5) of ‘n DTB strategie (B6) of besproeiing by ca. 90% PBW onttrekking (B7) gedurende rypwording. Wingerdstokke van twee ander behandelings is d.m.v. ‘n DTB strategie vanaf bot tot deurslaan besproei. Beide behandelings se grondwaterinhoud (GWI) was toegelaat om geleidelik uit te droog tot ca. 90% PBW onttrekking bereik was. Na deurslaan was die GWI van die een behandeling naby ca. 90% PBW onttrekking gehandhaaf deur slegs vier klein besproeiings van drie uur elk gedurende rypwording toe te pas (B8). Die grond van die ander behandeling het tydens deurslaan ‘n besproeiing ontvang om die GWI tot by veldkapasiteit te hervul (B9) en is tydens rypwording weer d.m.v. ‘n DTB strategie besproei. Stokke van die tiende behandeling is tussen bot en deurslaan by ca. 90% PBW onttrekking besproei, gevolg deur besproeiing d.m.v. ‘n gedeeltelike profiel hervul (GPH) strategie tydens rypwording (B10). Om ‘n GPH strategie toe te kon pas, is tussen 40% en 60% PBW ontrekking gehandhaaf. Evapotranspirasie het tussen 3.5 mm/dag en 0.1 mm/dag vir onderskeidelik die natste en droogste behandelings tussen Desember en Februarie gevarieer. Dit was aansienlik laer as volumes wat vir voloppervlak besproeide wingerde benodig word. In die geval van besproeiing by 30% tot 40% PBW onttrekking (B1), 70% tot 80% PBW onttrekking (B4) en ca. 90% PBW onttrekking (B7) deur die loop van die seisoen was die gewasfaktore vir die verwysingverdamping (ETo) 0.4, 0.2 en 0.1 onderskeidelik. Onder die gegewe toestande het die verskillende besproeiingstrategië geen effek op die worteldigtheid en –verspreiding gehad nie. Lootgroei van wingerdstokke wat aan hoë tot baie hoë watertekorte blootgestel was voor deurslaan, het voor middel Desember gestop. Lote van wingerdstokke wat aan hoë tot baie hoë watertekorte voor deurslaan blootgestel is, gevolg deur besproeiing teen ’n hoë frekwensie tydens rypwording, het aktiewe hergroei getoon. Die PBW ontrekkingspeil het sterk in die plantwaterpotensiale van wingerdstokke weerspieël. Blaarwaterpotensiaal is deur heersende klimaatstoestande beïnvloed, terwyl stamwaterpotensiaal minder sensitief teenoor die klimaat was, maar meer direk deur die beskikbaarheid van grondwater beïnvloed is. Vanweë die goeie verband tussen voordagbreek blaar-, mid-dag blaar-, mid-dag stam- en totale daaglikse waterpotensiaal, was dit moontlik om water status van die stokke te her-klassifiseer in terme van vorige vir waterpotensiaalklassifikasies wat op voordagbreek waardes gebasseer is. Waterspanning in B1, B2 en B5 stokke is as geen spanning geklassifiseer, terwyl dié van B7 en B8 voor oes in die hoë tot baie hoë klasse geval het. Hoë frekwensie besproeiing strategieë gedurende rypwording kan suikertoename a.g.v. die groter korrels vertraag. Met die uitsondering van die natste strategie, asook waar stokke volgens die DTB strategie deur die seisoen besproei is, het korrelmassa gedurende rypwording toegeneem. Watertekorte het ’n negatiewe effek op korrelmassa, trosgrootte en produksie gehad. Besproeiingstrategieë waar ’n hoë mate van grondwateronttrekking voor besproeiings toegelaat is, het ’n positiewe effek op die besproeiingwaterproduktiwiteit van wingerd in vergelyking met gereelde besproeiings of ‘n DTB strategie gehad. Watertekorte, veral gedurende rypwording, het ’n verbetering in sensoriese wynkleur en meer prominente wyn aromas, tot gevolg gehad. Besproeiing teen hoë frekwensies gedurende rypwording, het wyne met ’n afgewaterde smaak en aroma karakters asook ’n swak algehele gehalte produseer. Sensoriese wynkleur en spesery karakter die dominante faktore in die bepaling van algehele kwaliteit.

As water demand increases it will become more imperative for golf course superintendents, landscape managers, and other industry professionals to improve water use efficiency in the management of recreational turfgrass. Scheduling irrigation according to actual turfgrass evapotranspiration rates (ETT) is an integral component of efficient irrigation practices. Impracticality of field derived ETT for industry use, however, directs the need of weather station derived reference (predicted) evapotranspiration (ET0). To accurately predict (estimate) ETT of turf and other crops, scientifically derived landscape (crop) coefficients (Kc values) are used in conjunction with mathematical models that incorporate local meteorological data. Research is limited, however, in identifying Kc values and subsequent ET0 for turfgrass species selected and maintained under high intensity recreational practices congruent of golf courses and sports fields in the cool-humid northeast climate. Therefore, objectives of this study were to (i) observe and record ETT of three commonly selected recreational turfgrass species; 'Exacta' Perennial ryegrass (Lollium perenne L.), 'Touchdown' Kentucky bluegrass (Poa pratensis L.), and 'Memorial' Creeping bentgrass (Agrostis stolinifera L.) maintained as golf and sports turf, (ii) analyze the impact various management practices (nitrogen fertility and height of cut) have on ETT, (iii) develop accurate Kc values appropriate for use with the recommended FAO 56 Penman-Monteith mathematical model for accurate ET0 of recreational turf maintained in the cool-humid northeast. Four heights of cut (HOC) and two nitrogen fertility rates (N) were evaluated to determine their impact on turfgrass growth and subsequent water use and ETT of three recreational turfgrass species. Golf turf (creeping bentgrass) maintained at a lower height of cut than sports turf exhibited a smaller leaf area component and a significantly lower (20%) ETT. N applied as slow release (82%) throughout the growing season increased ETT by 5%, particularly with perennial ryegrass sports turf. Taller HOC also increased ETT by 10% due to increased leaf area indices and subsequent decreased resistance to ET. Predicted ET0 according to FAO 56 for all three years of the study (79 observations) captured 71% of ETT. Yearly and monthly calculations suggest less variable (cloudy) weather yielded more accurate ET0. Crop coefficient (Kc) values established in conjunction with FAO 56 ET0 ranged from 0.90 to 1.00 for shorter golf course turf (creeping bentgrass), and 1.15 to 1.25 for taller sports turf (Kentucky bluegrass and perennial ryegrass). Results indicate shorter grass exhibits a lower ETT than taller grass due to various factors, and in the case of industry application, FAO 56 ET0 can accurately estimate ETT of recreational turf in the cool-humid northeast when fitted with appropriate Kc values.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The availability and proper management of water represent fundamental aspects of the development of sustainable agricultural production systems, since it has direct impact on crop productivity. Maintaining crop residues on the soil surface reduces soil water loss by evaporation and soil temperature changes. Irrigation may be an efficient and safe tool to increase and support crop yields. The accuracy of crop evapotranspiration calculation is important for obtaining satisfactory results, in this context the use of dual crop coefficient allows for the accurate estimation considering separately evaporation soil and crop transpiration. Thus, the objective was to evaluate the influence of plant residues on the surface on the dynamics of water evaporation and soil temperature in the early stages of development of soybean plants. Moreover: (i) quantify plant residues effects on water evaporation, (ii) determine the effect of coverage on soil temperature and (iii) to compare the results obtained under field conditions with simulations performed with the dual crop coefficient methodology. A trial was done on a set of drainage lysimeters installed in a rain-out shelter, located in Las Brujas Experimental Station (34 ° 40 '19''S, 56 ° 20'24''W., altitude 45 m) of the National Research Institute of Agriculture (INIA), Uruguay. Design experimental was completely randomized, factorial with three replications. The factor A was composed of two levels of ground cover (0 and 4 Mg ha-1 of oat straw) and the factor B represented the area of soybean cultivation (with and without plants). Water losses were determined in soil drying cycles based on reference evapotranspiration (ETo). It was estimated by the Penman-Monteith equation.The soil water content was determined with TDR sensors installed at 0-10 cm and 10-30 cm depth. Soil temperature was measured with thermometers installed at 5 and 10 cm depths, records every 30 minutes. The evaporation rate of soil water was reduced 50% by plant residues on the soil surface. The soil cover resulted in maximum temperature 6 º C lower, minimum temperature 2 ° C higher and temperature range 40% lower. The soil water simulations using dual crop coefficient methodology resulted in good agreement with values measured in soil lysimeters without cover and on the ground covered by crop residues. / A disponibilidade e o manejo apropriado da água representam aspectos fundamentais para o desenvolvimento de sistemas de produção agrícola sustentáveis, visto que esta tem impacto direto na produtividade das culturas. A manutenção de resíduos vegetais na superfície do solo diminui as perdas de água do solo por evaporação e altera a temperatura do solo. A irrigação se apresenta como uma ferramenta eficiênte e segura de aumentar e estabilizar os rendimentos das culturas. A exatidão no cálculo da evapotranspiração das culturas é importante para a obtenção de resultados satisfatórios, nesse contexto o uso de coeficientes culturais duais permite realizar estimativas precisas considerando separadamente a evaporação do solo e a transpiração da cultura. Dessa forma, o objetivo deste trabalho foi avaliar a influência dos resíduos vegetais na superfície sobre a dinâmica de evaporação de água e temperatura do solo nas fases iniciais de desenvolvimento de plantas de soja. Alem disso: (i) quantificar o efeito dos resíduos vegetais na evaporação de água; (ii) determinar o efeito da cobertura na temperatura do solo e; (iii) comparar os resultados obtidos em nivel de campo com simulações realizadas com a metodologia de coeficientes culturais duais. Foi realizado um experimento num conjunto de lisimetros de drenagem instalados em uma casa de vegetação móvel (rainout shelter), localizado na Estação Experimental Las Brujas (34°40´ 19´´ S., 56°20´24´´ W., altitude 45 m) do Instituto Nacional de Investigación Agropecuaria (INIA), Uruguai. O delineamento experimental utilizado foi o inteiramente casualizado, bifatorial com três repetições. O fator A foi constituido de dois níveis de cobertura do solo (0 e 4 Mg ha-1 de palha de aveia) e o fator B representou o cultivo da área com soja (com e sem cultivo). As perdas de água foram determinadas em ciclos de secagem do solo baseados na evapotranspiração de referência (ETo), estimada pela equação Penman Monteith-FAO. O conteúdo volumétrico de água foi determinado com sensores TDR instalados nas camadas de 0-10 cm e de 10-30 cm de profundidade. A temperatura do solo foi medida com termômetros instalados nas profundidades de 5 e 10 cm, com leituras a cada 30 minutos. A taxa de evaporação de água do solo foi diminuída em 50% pelos resíduos vegetais na superfície do solo. A cobertura do solo resultou em temperatura máxima 6 ºC menor, temperatura mínima 2 ºC maior e amplitude térmica 40% menor. As estimativas de água disponível no solo efetuadas com a metodologia dos Kc duais apresentaram boa concordância com valores medidos nos lisímetros tanto no solo sem cobertura como no solo coberto por residuos vegetais.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In order to overcome periods of drought and low water availability, deficit irrigation becomes an important tool as long as it is applied on the least sensitive periods of the crops development to reduce the impacts on the productivity. Furthermore, deficit irrigation can be most efficient when there is an understanding of the way plants lose water. Crop evapotranspiration (ETc) is divided into soil evaporation (Es) and crop transpiration (Tc). The objectives of this paper were, beside measuring the soil water balance for different crops (bean, soybean and maize), was to determine adequate crop base coefficients (Kcb) for southern Brazil conditions, partition ETc into Es and Tc to better evaluate and understand soil water dynamics along the crops development cycle, determine water productivity (WP) considering different levels of deficit irrigation, to compare scenarios of water consumption on main and secondary crop schedules. The soil water balance model SIMDualKc was used, after due calibration and validation, using the dual crop coefficient methodology (Kc dual). A series of experiments were done (drybeans in 2010/11; maize in secondary schedule in 2010/11; maize in 2011/12; and soybean in 2014/15), with the imposition of different irrigation deficits as treatments, using drip irrigation and mulching. The results of SIMDualKc simulations show good agreement between the observed and simulated available soil water (ASW) content, values of regression coefficients (b0) were in average 0,98 for drybeans, 0,97 for soybean, 1,0 for secondary schedule maize and 1,05 for regular maize. The adjusted Kcb values for local conditions were respectively to bean, soybean and maize, 0,15; 0,15; 0,2 for the initial period (Kcb ini), 1,03; 1,0; 1,12 for the middle season (Kcb mid); and 0,2 for the end season for all crops (Kcb end). The results of water balance for each crop show that the less water is given to the plants, the better the water use, keeping in mind that ETc have not reduced in the same proportion. Regarding main and secondary schedules for maize the results for soil water balance show that main schedule maize had an increased water consumption (higher ETc) when compared to secondary schedule. The Es component was lower than 26% of ETc, for bean and soybean, and lower than 9% of ETc for maize, indicating the positive effect of mulching. / Para contornar períodos de secas e de baixa disponibilidade hídrica, a irrigação deficitária constitui-se em uma ferramenta importante, desde que aplicada nos períodos menos sensíveis das culturas, a fim de reduzir os impactos sobre a produtividade das culturas. Além disso, a irrigação deficitária pode ser mais eficiente quando se compreende o modo como ocorre a perda de água pelas plantas, a evapotranspiração das culturas (ETc), que se divide em evaporação do solo (Es) e transpiração da cultura (Tc). Os objetivos deste trabalho consistiram em (a) realizar o balanço hídrico do solo cultivado com diferentes culturas (feijão, soja e milho) e determinar os coeficientes de cultura basal (Kcb) mais adequados para as condições do Sul do Brasil; (b) particionar a ETc em Es e Tc para melhor avaliação e entendimento da dinâmica da água no solo ao longo do ciclo das culturas; (c) avaliação da produtividade da água (WP) considerando diferentes níveis de irrigação deficitária; (d) comparação de cenários entre cultivo de safra e safrinha no que se refere ao consumo de água pelas plantas. Para isso, utilizou-se o modelo de balanço hídrico SIMDualKc, o qual foi devidamente calibrado e validado, e que utiliza a metodologia dos coeficientes culturais duais (Kc dual). Experimentos foram conduzidos (feijão em 2010/11; milho safrinha em 2010/11; milho safra em 2011/12; e soja em 2014/15), com a imposição de diferentes níveis de déficit hídrico, utilizando a irrigação por gotejamento e com presença de resíduos vegetais na superfície do solo. Os resultados obtidos com as simulações do modelo SIMDualKc apresentaram boa concordância entre os valores de água disponível no solo (ASW) observados e simulados, com valores de coeficiente de regressão (b0) de, em média, 0,98 para feijão, 0,97 para soja, 1,0 para milho safrinha e 1,05 para milho safra. Os valores de Kcb ajustados para as condições locais foram, respectivamente para feijão, soja, milho, para o período inicial (Kcb ini) 0,15; 0,15; 0,2; para o período intermediário (Kcb mid) 1,03; 1,0; 1,12; e para o período final (Kcb end) 0,2 para todas as culturas. Os resultados do balanço hídrico do solo para cada uma das culturas demonstraram que quanto menor a quantidade de água aplicada nas plantas, melhor uso foi feito desta água pelas plantas, tendo em vista que a ETc não reduziu-se na mesma proporção. No que se refere a comparação de cenários entre milho safra e safrinha, os resultados do balanço hídrico do solo também demonstraram que o milho cultivado durante a época de safra teve um maior consumo de água (maior ETc) quando comparado ao milho cultivado no período de safrinha. O componente Es foi inferior a 26% da ETc, para feijão e soja, e inferior a 9% da ETc para milho safra e safrinha, indicando assim o efeito positivo da utilização de resíduos vegetais sobre a superfície do solo.

Made available in DSpace on 2016-04-28T14:58:35Z (GMT). No. of bitstreams: 1 2006-Joao Batista Alves Pereira.pdf: 1832144 bytes, checksum: 36798c7d302cc3a5d500e230c9f5af03 (MD5) Previous issue date: 2006-02-21 / Evaluation of the vegetal growth, hydric necessity and water use efficiency by bell pepper crop (Capsicum annum. L.) under organic management in system of seeding with prepare soil and no till cropping system. This work was conducted in the experimental area of SIPA (Integrated system of agro ecological production), at the county of Serop?dica RJ, with the aim of valuate the growth , the water needs, and the efficiency of the use of the water by the bell pepper culture (Capsicum annuum. L ), at the conventional (PC) and the direct systems of soiling. The conventional system consisted of soil prepare with rotational hoe tied to a micro tractor, and the direct soiling, being done after the occupation of the area with a combination of Sorghum bicolor and Crotal?ria acroleura, that was grazed at the transplantation of the bell pepper s seedlings without previous soil preparation. The same fertilization and cultural practices permitted by the agro ecological handling, was used in both systems. The two systems tested, received sprinkler irrigation, and the determination of the water s blade, was made by monitoring with TDR (Time Domain Reflectometry), calibrated for the soil conditions of the experimental area. The splits were also monitorated by a tensiometer at a 50 cm. deep. Collects were made at intervals of 14 days, with the aim of foliar area evaluation, biomass accumulation by the parts of the plant, along the entire cycle, being also evaluated the crop production at the two systems of soiling. By the adjustment of the IAF (Foliar Area Indices ) and the biomass accumulated by the plant at the two systems of planting in function of accumulated day-degree (GDA), was verified that 1533 GDA was necessary to complete the productive cycle, reaching the top of accumulated biomass at 1059 and 1148 GDA, at PC and PD respectivement. There were no differences between the systems of planting, in respect of the growth rate and the productivity, however the PD system gave less competition between spontaneous vegetation and the bell pepper crop, reducing in 60% the necessity of hand labor at the firsts weddings. The PD system raise the efficiency of the use of water (EUA) by the crop reducing in 47,5 mm. the blade applied during its cycle, in relation of PC. The irrigation handling using TDR, provide an meaning EUA of 4,4 Kg.m-3, above the means of 1,5 to 3,0Kg.m-3, recommended by Doorenbos & Kassam (1994). The culture coefficients (Kc) recommended for the bell pepper crop, were evaluated together with the calculated coefficients using some methodologies proposed in this work, and was noted that the estimated Kc s values of the production cycles (ETc cycle) and by the Kc curve (graphic ETc) estimated during the culture cycle, were more appropriated for the calculation of the evapotranspiration of the crop. The estimation of reference evapotranspiration (ETo), by the pan class A method, made possible means close to those estimated by the Penman-Monteith model witch is recommended by FAO as standard. Therefore, the pan class A method, can be utilized in the estimated ETo, at same conditions of the experiment when there are no data of climate for the Penman-Monteith model use. Associated tensiometry and TDR for irrigation management, showed to be an essential practice when looking for raising the efficiency of the use of water. / Este trabalho foi realizado na ?rea experimental do SIPA (Sistema Integrado de produ??o Agroecol?gica), localizada no munic?pio de Serop?dica-RJ, com o objetivo de avaliar o crescimento, as necessidades h?dricas e a efici?ncia no uso da ?gua pela cultura do piment?o (Capsicum annuum. L), nos sistemas de plantio convencional (PC) e direto (PD). O sistema convencional consistiu de preparo de solo com enxada rotativa acoplada a micro-trator e o plantio direto, na ocupa??o da ?rea com pr?-cultivo, utilizando o cons?rcio Sorghum bicolor e Crotal?ria acroleura, os quais foram ro?ados por ocasi?o do transplante das mudas de piment?o, sem o preparo pr?vio do solo. Em ambos os tratamentos a cultura recebeu a mesma aduba??o de cova e tratos culturais permitidos pelo manejo agroecol?gico. Nos dois sistemas de plantio a cultura foi irrigada por aspers?o, e a determina??o das l?minas aplicadas, foi realizada atrav?s do monitoramento com TDR (Reflectometria no dom?nio do tempo), calibrado para as condi??es de solo da ?rea experimental. As parcelas foram monitoradas tamb?m por tensi?metro no perfil de 50cm de profundidade. Foram realizadas coletas em intervalos de 14 dias com a finalidade de avaliar a ?rea foliar e acumulo de biomassa pelas partes da planta, durante todo o seu ciclo, sendo avaliado tamb?m a produ??o pela cultura nos dois sistemas de plantio. Por meio do ajuste do IAF e da biomassa acumulada pela planta nos dois sistemas de plantio em fun??o de graus-dia acumulado (GDA), constatou-se que s?o necess?rios 1533 GDA para que a planta complete o seu ciclo produtivo, atingindo o m?ximo de biomassa acumulada aos 1059 e 1148 GDA, no PC e PD, respectivamente. Os sistemas de plantio n?o diferiram significativamente entre si com rela??o ?s taxas de crescimento e produtividade, entretanto o plantio direto proporcionou menor competi??o da vegeta??o espont?nea com a cultura, reduzindo em 60 % a necessidade de m?o-de-obra nas primeiras capinas. O PD aumentou a efici?ncia no uso da ?gua (EUA), pela cultura, reduzindo em 47,5mm a l?mina aplicada durante o seu ciclo, em rela??o ao PC. O manejo da irriga??o utilizando o TDR, proporcionou a EUA m?dia de 4,4kg.m-3, acima dos valores 1,5 a 3,0kg.m-3 propostos por Doorenbos e Kassam (1994). Os Coeficientes de cultivo (Kc) recomendados para a cultura, foram avaliados juntamente com os calculados por v?rias metodologias propostas neste trabalho, verificando-se que os valores de Kc estimados em fun??o dos ciclos de produ??o (ETc ciclo) e pela curva de Kc (ETc gr?fico) estimados durante o ciclo da cultura, se mostraram mais adequados ao c?lculo da evapotranspira??o da cultura. A estimativa da evapotranspira??o refer?ncia (ETo), pelo m?todo do tanque classe A , possibilitou valores pr?ximos aos estimados pelo modelo de Penman-Monteith recomendado pela FAO como padr?o. Portanto o m?todo do tanque classe A poder? ser utilizado na estimativa da ETo, em condi??es semelhantes a do experimento, quando n?o houver disponibilidade de dados clim?ticos para o uso do modelo de Penman- Monteith. O uso da tensiometria associado ao TDR no manejo de irriga??o revelou ser uma pr?tica indispens?vel, quando se almeja aumentar a efici?ncia no uso da ?gua.

In der Wintersaison 2005-2006 wurde ein Split-Split Plot-Design Feldversuch mit drei Wiederholungen für jede Behandlung von Kartoffeln, als Indikatorpflanze, unter den ariden Bedingungen der Kharga Oasis in der Westlichen Wüste von Ägypten durchgeführt. Drei Bewässerungslevel (100 %, 80 %, und 60 % of ETc) mit Tröpfchenbewässerung, zwei Mulchvarianten (Zuckerrübenabfall ohne und mit 24 ton ha-1) und 4 Kompostraten (0, 12, 24, und 36 ton ha-1) wurden getestet. Generell und als Ergebnis einer Regressionsanalyse der Versuchsvarianten ohne Kompost war die beste Variante die Tröpfchenbewässerung bei 80% ETc unabhängig ob gemulcht oder nicht gemulcht wurde. Andererseits die Variante mit 36 t Kompost und mit 24 t Mulch ergab die besten Ergebnisse bei 60% of ETc sowohl beim Ertrag und den Ertragskomponenten, bei den hydrophysikalischen Eigenschaften, bei der Bodenwasserretention, beim Wasserverbrauch, bei den Pflanzenkoeffizienten, der Wassernutzungseffizienz, der Düngernutzungseffizienz sowie beim Nettogewinn. Wird die Rate der Kompostgabe aber auf 24 ton ha-1 reduziert, die höchsten Nettogewinne bei der lokalen Vermarktung als auch signifikant beim Kartoffelexport werden erreicht. / Under the arid condition of Kharga Oasis in the Western Desert of Egypt, split-split plot design field experiment with three replications for each treatment using potato as an indicator plant was carried out during the winter season 2005-2006. Three irrigation levels of water regime (100 %, 80 %, and 60 % of ETc) using drip irrigation system, two treatments of soil covering (sugar cane wastes at the rate of 0 and 24 ton /ha) and compost rates (0, 12, 24, and 36 ton ha-1) were tested. In general and as a result of the triple interaction among the studied treatments, using drip irrigation either with soil mulching or not, 80 % of ETc as a water regime was the best. On the other hand, reducing drip irrigation water level at 60% of ETc in mulched soil that was treated with 36 ton ha-1 of compost recorded the highest values yield and yield components, soil hydrophysical properties, soil water retention, water consumption, crop coefficients, water economy water use efficiency, fertilizer use efficiency, net profit. But reducing the compost rate to 24 ton ha-1 attained the highest net profit for local potato consumption and achieved the best significant net profit for exportation.