Climate models have projected that arid and semiarid lands will experience warmer and drier conditions for the next 100 years. For the last twenty years, the Southwestern US has been experiencing one of the worst droughts over the last century, not only threatening ecological systems but also the water security of its population. Understanding the environmental processes that affect arid and semiarid forests are essential to better understand the water and carbon cycles, and tree-ring research has contributed valuable knowledge in this regard. There is a common understanding that moisture-stress has significant impacts on forested ecosystems and thereby on the global carbon and water cycles. Under persistent moisture deficit, a decline in growth, an increased proportion of wildfires, insect outbreaks, and mass-tree-mortality are often observed in arid and semi-arid forests, having large impacts on their carbon budgets and their capacity to act as a carbon sink. This study addresses the seasonal and regional climatic influences on the water-carbon relations in the ponderosa pine forests of the southwestern US (SW). This region is characterized by a complex climatology related to the North American Monsoon system (NAMS). A topic of interest in this dissertation is the role of the summer rainfall after the early-summer hyper-arid period in the region, providing a unique seasonal condition for these ecosystems to thrive. While these forests clearly rely on winter snowpack to drive much of their annual net primary productivity, the temporal and regional extent to which they supplement winter moisture with summer monsoon moisture needs to be clarified. The core of this dissertation is a study of the spatial and temporal variability of the stable carbon and oxygen isotopes in the cellulose of subsections of the tree rings (e.g., earlywood and latewood) collected from a network of thirteen sites along a latitudinal gradient extending from southern Arizona and New Mexico, through southwest Colorado, and up to northern Utah. The analysis is based on biological and physical processes and their close relationships with isotope effects to infer eco-physiological responses to climate variations over the last century. The stable carbon isotopes are used to derive intrinsic Water-Use Efficiency (iWUE) defined by the molar ratio of carbon gain to water loss. The stable oxygen isotope ratio is used to infer the variations on evaporative flux at the leaf level, which depend on stomatal conductance, atmospheric vapour pressure deficit at the leaf surface, and variations in the isotopic ratio of the source water. Both isotopic ratios are used to document variations in tree productivity and hydrologic vulnerability within the context of climate change impacts on this region. During the study, it was found that climate change in the SW has impacted the carbon and water cycles of these forests for at least the past twenty years. Additionally, seasonality influence the eco-physiology of ponderosa pine change along the latitudinal gradient, as shown by significant differences between EW and LW. These differences are explained by the large shifts in seasonal VPD, which are more evident in the southern part of our study region due to the mid-summer arrival of monsoon rains. These findings will be useful for regional natural resource managers and improves our understanding of seasonal influences on forest water–carbon relationships. This approach will also be useful to develop seasonally resolved paleoclimate and paleo-ecophysiological reconstructions to characterize the long-term influence of winter versus summer moisture on carbon-water relations in forested ecosystems.

Afforestation and reforestation programs utilizing available fields for biofuel production, carbon sequestration, and other uses linked to climate change are looking to tree physiologists to identify species and genotypes best-suited to their purposes. The ideal poplar genotype for use in Canadian programs would be drought-resistant, cold-climate adapted, and fast-growing, thus requiring an understanding of links between a variety of physiological traits linked to growth and productivity. This study examined the basis for variations in water-use efficiency within four selected populations of Populus trichocarpa and Populus balsamifera (2 provenances each). Each species included both a northern and a southern provenance. Correlations between water-use efficiency, nitrogen-use efficiency, ¹³C/¹²C isotope ratio, stomatal conductance, and overall productivity were evaluated. Gas exchange variables measured included net photosynthesis, transpiration rate, stomatal conductance, and intercellular CO₂ content. Water-use efficiency and ¹³C content across all genotypes were highly correlated. Results suggested that variation in water-use efficiency was primarily related to variation in stomatal conductance across all genotypes. Whereas differences in net photosynthesis in this study were not significant between species, P. balsamifera did reveal a higher average stem volume overall. Although variation in stomatal conductance was the major determinant of differences in water-use efficiency, positive correlations were found between ¹³C isotope abundance and net photosynthesis in both P. balsamifera provenances. In this regard, results for the northern P. balsamifera provenance are the most consistent across all gas-exchange and growth trait correlations, in terms of meeting expectations for sink-driven water-use efficiency. The findings in this study suggest the possibility of identifying poplar genotypes with an absence of trade-off between water-use efficiency and nitrogen-use efficiency, notably among genotypes from the northern P. balsamifera provenance, near Gillam. / Forestry, Faculty of / Graduate

Irrigation with saline waters is an agricultural practicethat is becoming increasingly common as competition for freshwater increases. In this thesis the mechanisms behind salinityand drought stress has been studied using data from fieldexperiments in combination with a modelling tool, theCoupModel. Measurements from field experiments on salinity,boron toxicity and drought stressed tomatoes grown during twoclimatically different seasons in the Arava desert, Israel,showed a linear relationship between relative growth andevapotranspiration, for all treatments and seasons. Data fromthe spring was used to concurrently simulate growth andtranspiration, hence accounting for feedback mechanisms betweenthe plant and the environment. Salinity stress was modelled asan osmotic effect (reduction of water uptake at high soilsalinities, W approach) or a toxicity effect (direct reductionof photosynthesis with soil salinity, G approach). Goodagreement between simulated growth and transpiration wasachieved with both salinity stress approaches, with twoexceptions. When growth and transpiration were simulated withthe W approach at different salinity levels, transpiration wasunderestimated at high stress. The G approach resulted in anunderestimation of growth at high water stress under moderatesalinity. A direct decrease of photosynthesis leads to adecreasing water-use efficiency with salinity while water-useefficiency remains constant with salinity when the salinitystress is modelled as a reduction in water uptake. Measurementsshowed decreasing water-use efficiency for the salinitygradient, explaining why the W approach was not applicable. Itwas not possible to detect any considerable differences betweenthree different approaches for water uptake tested in thestudy. <b>Keywords:</b>Water-use efficiency; osmotic effect; iontoxicity; semi-arid. / NR 20140805

Species in the genus Populus (poplars) have shown the potential to be utilized as short rotation woody crops for bioenergy production in the Southeast. A lack of knowledge on which poplar taxa perform best on marginal sites throughout the Southeast exists. Through measurement of relationships between growth metrics, water usage and physiological parameters of 2400 poplar trees, I was able to assess: 1) early rotation suitability of numerous poplar varietals to be grown as bioenergy feedstocks in northeast Mississippi, and 2) the effectiveness of early rotation physiological parameters in predicting future productivity and water usage. Overall findings from this study suggest that trees with D x M parentage may be best fit for large-scale plantation growth in the Southeast. They demonstrated low mortality and collectively grew the tallest of all taxa. Early-rotation physiology demonstrated mixed results in predicting future growth and water usage. Findings from this study will be used in future bioenergy feedstock selection.

Submitted by Patrícia Costa Silva (patypcs@yahoo.com.br) on 2018-07-30T19:35:52Z No. of bitstreams: 1 Tese_Patricia_Costa_Silva_2018_final.pdf: 1846241 bytes, checksum: b3112d63566f4acc8bf90ba51cfb28d2 (MD5) / Approved for entry into archive by Ana Lucia de Grava Kempinas (algkempinas@fca.unesp.br) on 2018-07-30T20:54:23Z (GMT) No. of bitstreams: 1 silva_pc_dr_botfca.pdf: 1846241 bytes, checksum: b3112d63566f4acc8bf90ba51cfb28d2 (MD5) / Made available in DSpace on 2018-07-30T20:54:23Z (GMT). No. of bitstreams: 1 silva_pc_dr_botfca.pdf: 1846241 bytes, checksum: b3112d63566f4acc8bf90ba51cfb28d2 (MD5) Previous issue date: 2018-05-14 / O cultivo de sorgo sacarino surgiu como alternativa para produção de massa destinada à fabricação de etanol, na entressafra, e em áreas de reforma do canavial e em áreas de rotação à outras culturas. Ainda são escassos estudos sobre a irrigação em sorgo sacarino, bem como os estudos que correlacionam lâminas de irrigação e a dinâmica dos nutrientes no solo e propriedades físicas. Este estudo teve como objetivos analisar o efeito da aplicação de lâminas de irrigação sob características tecnológicas e agronômicas de variedades de sorgo sacarino e nas propriedades do solo, e avaliar a eficiência do uso da água. O experimento foi conduzido em campo na área experimental da Universidade Estadual de Goiás, Câmpus de Santa Helena de Goiás. O delineamento adotado foi o de blocos casualizados com esquema fatorial 5x3, com 5 tratamentos, 3 cultivares de sorgo sacarino e 4 repetições. Os tratamentos foram constituídos por 5 lâminas de irrigação: 25, 50, 75, 100 e 125 % da evapotranspiração de cultura (ETc) e as variedades avaliadas foram BRS 511, CVSW 80007 e Silotec 20. O sistema de irrigação empregado foi o localizado por gotejamento. Os dados foram submetidos à análise de variância pelo teste F a 5% de significância. As médias para o fator variedades e propriedades do solo foram comparadas pelo teste de Tukey e para o fator lâminas de irrigação empregou-se a análise de regressão. Verificou-se que as lâminas de irrigação exerceram influência significativa nas características agronômicas e tecnológicas. A variedade BRS 511 adaptou-se melhor às condições edafoclimáticas locais com reflexo em maior altura de plantas, diâmetro de colmo, número de folhas e internódios, porcentagem de folhas, produtividade de colmos, massa verde da parte aérea, rendimento de caldo, produtividade de etanol e sólidos solúveis totais; e menor peso do bagaço úmido e teor de fibra industrial. Comparando-se as variedades em cada lâmina verificou-se variação a partir da lâmina 75% de reposição da evapotranspiração de cultura com ajustes linear e quadrático. A eficiência do uso da água (EUA) em todas as variedades e lâminas estudadas apresentou resposta linear decrescente, com maior EUA na lâmina de 25% da ETc. A variedade BRS 511 foi a mais recomendada para as condições edafoclimáticas da região avaliada e a lâmina mais indicada foi a equivalente a 100% da ETc. As lâminas de irrigação exerceram influência sobre a dinâmica das propriedades químicas no solo. Os maiores teores dos nutrientes foram encontrados na camada de 0-0,10 m, à medida que aumentou a disponibilidade hídrica; para as lâminas de 100 e 125 % da ETc houve aumento dos teores de nutrientes e de matéria orgânica do solo; entre as variedades e as camadas de solo houve variação somente para o potássio e o alumínio. As propriedades físicas não foram afetadas pelo cultivo das variedades e lâminas de irrigação, apenas pelas camadas amostradas. / Cultivation of sorghum emerged as an alternative for the production of mass destined to the manufacture of ethanol, in the off season, and in areas of reforestation of cane fields and in areas of rotation to other crops. There are still few studies on irrigation in sorghum, as well as studies that correlate irrigation slides and the dynamics of soil nutrients and physical properties. The objective of this study was to analyze the effect of the application of irrigation slides under the technological and agronomic characteristics of sorghum varieties and soil properties, and to evaluate the efficiency of water use. The experiment was conducted in the experimental area of the State University of Goiás, Campus of Santa Helena de Goiás. The experiment was a randomized complete block design with 5x3 factorial, with 5 treatments, 3 sorghum cultivars and 4 replicates. The treatments consisted of 5 irrigation slides: 25, 50, 75, 100 and 125% of crop evapotranspiration (ETc) and the varieties evaluated were BRS 511, CVSW 80007 and Silotec 20. The irrigation system was located by drip. The data were submitted to analysis of variance by the F test at 5% of significance. The averages for the factor varieties and soil properties were compared by the Tukey test and for the irrigation lamina factor the regression analysis was used. It was verified that the irrigation slides exerted significant influence on the agronomic and technological characteristics. The BRS 511 variety was better adapted to local edaphoclimatic conditions with higher plant height, stem diameter, number of leaves and internodes, leaf percentage, shoot yield, shoot shoot mass, broth yield, seed yield ethanol and total soluble solids; and lower weight of the wet cake and industrial fiber content. Comparing the varieties on each slide, a variation was observed from the 75% replacement blade of the crop evapotranspiration with linear and quadratic adjustments. Efficiency of water use in all varieties and slides studied presented a linear decreasing response, with a higher USA in the 25% ETc blade. The BRS 511 was the most recommended for the soil and climatic conditions of the evaluated region and the most indicated blade was the equivalent to 100% of the ETc. Irrigation slides influenced the dynamics of soil chemical properties. The highest levels of nutrients were found in the 0-0.10 m layer, as water availability increased; for the slides of 100 and 125% of the ETc there was an increase in nutrient and soil organic matter contents; between varieties and soil layers there was variation only for potassium and aluminum. The physical properties were not affected by cultivation of the irrigation varieties and slides, only by the sampled layers.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Soil amelioration and conditioning is desirable and in many cases essential, due to increasing food demand and the deterioration and exhaustion of soils. A new soil ameliorant, consisting of orange oil as a base and a mixture of surfactants, is on the global agricultural market. Use of this soil ameliorant by farmers has made an impact on crop production and plant growth on many farms. The effects of this soil ameliorant on selected soil properties as well as plant traits were evaluated by a field trial, a pot trial and a Water Characteristic Curve experiment. A field trial was performed in the Firgrove area near Somerset West, Western Cape (South Africa). It entailed the evaluation of the water content and lateral movement of water in a sandy soil after the application of the soil ameliorant. The field was already planted with Capsicum annuum crop at the initiation of the trial. The trial was performed in a drip irrigated field by taking soil water measurements using a Diviner 2000 probe over a nine week period. The trial showed significant increases in water content on the plots treated with the soil ameliorant. These increases are indicative of an increase in the lateral movement of the soil water, as the measurements were taken between two drippers. On average, the ameliorant treated soil had 17% higher water content than that of the control. A Water Characteristic Curve (WCC) experiment was conducted, which entailed establishing the WCC for a sandy soil treated with the soil ameliorant. The Sandbox apparatus, from Eijkelkamp Agrisearch Equipment, was used to perform the experiment and provides suction values of 0.1 to 10.1 KPa. The WCC showed that the ameliorant application increased water retention over all suctions, especially for the 10 l/ha ameliorant application. This substantiated the Field trial where water retention was increase in a sandy soil. A pot trial was performed in a greenhouse to evaluate the effect of the soil ameliorant on selected soil properties and certain plant traits. This experiment consisted of an ameliorant treatment and a control with a combination of four different Plant Available Water Depletion (PAWD) regimes namely, 10% depletion, 50% depletion, 80% depletion and 50%C depletion, where “C” refers to covered. The trial layout, with five single pot replicates per treatment combination, was according to a randomized block design. The surface covering of one of the 50% PAWDs was a plastic sheet which to prevent evaporation from the soil surface. The ameliorant treatment resulted in significant improvements in overall plant growth, total biomass production, especially dry root biomass. Leaf Area Index and plant height were also improved. The Biomass Water Use Efficiency was improved with the ameliorant application, especially for the 50%C PAWD illustrating the beneficial use of a mulch. Bulk density was decreased with application of the ameliorant but this difference was not statistically significant. Aggregate stability for the moist soils (10% and 50%C PAWD) was significantly improved with the ameliorant application. The application of this soil ameliorant made significant improvements in various facets of plant growth and certain soil physical properties. Especially water holding capacity in sandy soils and the overall improvement in plant growth. There is still much opportunity for research in this field and many questions remain, especially those pertaining to the mechanisms involved in the workings of a soil ameliorant containing a mixture of ingredients. / AFRIKAANSE OPSOMMING: Die bestuur van besproeingswater en die optimisasie van gewasproduksie is `n studieveld wat baie aandag verg, aangesien varswater bronne bedreig word. As gevolg van die stygende vraag na voedsel en die agteruitgang en uitputting van die grond, is grondverbetering en-kondisionering aanbeveelbaar en in sommige gevalle noodsaaklik. `n Nuwe grond verbeteraar, bestaande uit lemoen olie as `n basis en ‘n mengsel van benattingsmiddels, is beskikbaar op die wêreld landbou mark. Die gebruik van die grondverbeteraar deur boere het ‘n impak gemaak op gewasproduksie en plantegroei op baie plase. Die effek van die grondverbeteraar op geselekteerde grond-eienskappe sowel as plantkenmerke is geevalueer deur ‘n veld proef, ‘n pot proef en ‘n Water Karakeristieke Kurwe eksperiment. `n Veldproef is uitgevoer in die Firgrove omgewing naby Somerset Wes in die Wes-Kaap Provinsie, Suid Afrika. Die veldproef het die evaluasie van die grondwater inhoud en die laterale beweging van water in `n sanderige grond behels. Die gewas Capsicum annuum was alreeds in die veld aangeplant voor die begin van die proef. Die proef was uitgevoer in `n drup besproeide veld deur grondwater metings wat geneem is met `n Diviner 2000 peilstif oor `n periode van nege weke. Die proewe het `n beduidende verhoging in die groundwater-inhoud getoon waar die grond met die grondverbeteraar behandel is. Die verhogings was `n aanduiding van `n toename in die laterale vloei van grond water, aangesien die lesings tussen twee druppers geneem is. Die grond, wat met die grondverbeteraar behandel is, het gemiddeld 17% hoёr groundwater-inhoud gehad as die kontrole. `n Water Karakteristieke Kurwe (WKK) eksperiment is uitgevoer, wat bestaan het uit die opstel van die WKK vir `n sanderige grond behandel met die grondverbeteraar. Die “Sandbox” apparaat van Eijkelkamp, Agrisearch Equipment is gebruik wat negatiewe druk waardes van 0.1 tot 10.1 KPa toon. Die WKK het getoon dat die toediening van die grondverbeteraar die water retensie verhoog het oor al die drukke, veral in die 10 l/ha toediening. Dit staaf die resultate van die Veld eksperiment waar water retensie verhoog is in die sanderige grond. Die pot-eksperiment is uitgevoer in `n tonnel om die effek van die grondverbeteraar op geselekteerde grond eienskappe en verskeie plant eienskappe te evalueer. Die eksperiment het bestaan uit ‘n grondverbeteraar behandeling en ‘n kontrole met ‘n kombinasie van vier verskillende plantbeskikbare wateronttrekkings naamlik, 10%, 50%, 80% onttrekking, en ‘n 50%C onttrekking, waar “C” verwys na “covered”. Die proef uiteensetting, met vyf enkel pot herhalings per behandeling kombinasie was volgens ‘n ewekansig blok uitleg. Die oppervlakte dekking van 50%C plantbeskikbare waterottrekking was `n 60 μm plastiek-vel wat verdamping vanaf die grondoppervlak verhoed het. Die grondverbeteraar behandeling het `n beduidende verbetering in algehele plantgroei, totale biomassa produksie en spesifiek droё wortel biomassa getoon. Die blaararea indeks en planthoogte het ook `n verbetering getoon. Die biomassa-watergebruiksdoeltreffendheid het verbeter met die toediening van die grondverbeteraar, spesifiek vir die 50%C plantbeskikbarewaterottrekking wat die voordele van die gebruik van oppervlakdekking illustreer. Die brutodigtheid is verminder deur die toediening van die grondverbeteraar, maar die verskil was statisties nie wesenlik nie. Agregaat-stabiliteit vir die grond met `n hoёr vogregime (10% en 50%C plantbeskikbare waterottrekking) is wesenlik verbeter met die toediening van die grondverbeteraar. Die toediening van die grondverbeteraar het wesenlike verbeteringe in verskeie plantegroei- en grondfisiese-eienskappe getoon. Spesifiek laterale beweging in sanderige grond en die verbettering van algehele plantegroei. Daar is nog baie geleenthede vir navorsing in die veld en baie vrae bly onbeantwoord, veral in verband met die meganismes met bretrekking tot die werking van die grondverbeteraar wat uit `n mengsel van bestandele bestaan.

The arrival of the North American Monsoon System (NAMS) terminates a presummer hyperarid period in the southwestern United States (U.S.), providing summer moisture that is favorable for forest growth. Montane forests in this region rely on winter snowpack to drive much of their growth; the extent to which they use NAMS moisture is uncertain. We addressed this by studying stable carbon and oxygen isotopes in earlywood and latewood from 11 sites along a latitudinal gradient extending from Arizona and New Mexico to Utah. This study provides the first regional perspective on the relative roles of winter versus summer precipitation as an ecophysiological resource. Here we present evidence that Ponderosa pine uses NAMS moisture differentially across this gradient. C-13/C-12 ratios suggest that photosynthetic water use efficiency during latewood formation is more sensitive to summer precipitation at the northern than at the southern sites. This is likely due to the fact that NAMS moisture provides sufficiently favorable conditions for tree photosynthesis and growth during most years in the southern sites, whereas the northern sites experience larger summer moisture variability, which in some years is limiting growth. Cellulose O-18 and C-13 values revealed that photoassimilates in the southern sites were produced under higher vapor pressure deficit conditions during spring compared to summer, demonstrating a previously underappreciated effect of seasonal differences in atmospheric humidity on tree ring isotope ratios. Our findings suggest that future changes in NAMS will potentially alter productivity and photosynthetic water use dynamics differentially along latitudinal gradients in southwestern U.S. montane forests.

The goal of this project was to determine the genetic architecture of water-use efficiency (WUE) for foxtail pine, which included genomic loci, and effect sizes of this trait. Foxtail pine is a subalpine endemic conifer that inhabits two distinct regional populations separated by 500 km in the mountains of California. In order to achieve this goal, a robust linkage map containing thousands of genetic markers was created using four megagametophyte arrays ranging in size from approximately 70 to 95 megagametophytes. Quantitative trait loci (QTL) discovered for WUE were mapped along the linkage map using linear mixed models and five half-sibling families grown in a common garden. Effect sizes of these QTL were tested for differences between the two regional populations of foxtail pine.

O tomate (Lycopersicum esculentum Mill) é um dos vegetais mais populares e amplamente consumidos e que faz parte importante na dieta diária. A maioria das áreas cultivadas com a cultura é usando irrigação por sulcos e com menor proporção irrigada por gotejamento. Além de baixa eficiência no uso da água, o sistema de irrigação por sulcos possui impacto ambiental negativo, tornando assim o gotejamento um sistema alternativo viável. O experimento foi conduzido com o objetivo de se avaliar o efeito de quatro lâminas de irrigação por gotejamento, três doses de potássio e a presença de cobertura plástica sobre as características agronômicas do tomateiro L. esculentum, cultivar Débora Plus. Foi utilizado um delineamento experimental inteiramente casualizado, em um esquema fatorial 4x3x2, com três repetições. Os tratamentos consistiram de lâminas de irrigação equivalentes a 125, 100, 75 e 50 % da necessidade hídrica da cultura, com doses de potássio de 208, 416 e 624 kg ha-1, com e sem cobertura do solo ("mulching"). A lâmina de irrigação foi aplicada mediante sistema de gotejamento quando a tensão da água no solo estava entre 10 e 15 kPa. As lâminas de irrigação afetaram significativamente os parâmetros de crescimento vegetativo e produtividade. O potássio, o mulching, as interações de irrigação e potássio, de irrigação e mulching, de irrigação, potássio e mulching influenciaram a altura das plantas aos 90 dias após o transplante (DAT), a massa de matéria fresca das plantas e a produção. A eficiência do uso da água (EUA) diminuiu com o aumento das lâminas de irrigação, sendo que a produtividade máxima foi obtida com a aplicação de 0,57 L.dia-1.planta-1. As maiores produtividades total e comercial foram de 86,20 e 79,73 Mg.ha-1, obtidas da combinação de 54,36 L.planta-1. ciclo-1 e dose de potássio de 416 kg.ha-1, sob condições de solo coberto com mulching. / Tomato is one of the most popular and widely consumed vegetable which forms a major part of daily diet. Most of the crop is irrigated by furrow irrigation system with fewer experiences with drip irrigation. Apart from low water use efficiency, the main irrigation system posses negative environmental impact thus making drip irrigation viable alternative. The objectives of the study was to evaluate the effect of four drip irrigation levels, three potassium doses and the presence of plastic mulching on water use efficiency and the agronomic characteristics of tomato, Lycopersicon esculentum Mill, variety, Débora Plus. The experimental design was a randomized complete design in a 4 x 3 x 2 factorial scheme with three replications. The treatments consisted of irrigation water levels equivalent to 125, 100, 75 and 50% of crop water requirement with potassium doses of 208, 416 and 624 kg ha-1. Irrigation was applied through drip irrigation system when soil water tension was between 10-15 kPa. Irrigation water levels significantly affected crop development parameters and production. Potassium, mulching, interactions of irrigation and potassium, irrigation and mulching, irrigation, potassium and mulching influenced plant height at 90 days after transplant , fresh plant mass and production. Water use efficiency decreased with increase in irrigation levels with daily recommended irrigation water of 0,57 L plant-1 cycle-1. The highest total and commercial yield were 86,20 and 79,73 t ha-1 both obtained with 54,36 L plant-1 cycle-1 and potassium dose 416 kg ha-1 with mulching.

As mudanças climáticas globais e a expansão da cultura da cana-de-açúcar para regiões com menor suprimento hídrico elevaram a importância de estimativas consistentes das necessidades de água da cultura. Na tentativa de contribuir nesse campo, o presente trabalho buscou analisar o consumo hídrico da cana-de-açúcar em três diferentes escalas espaciais: folha, planta e dossel, além de uma ferramenta de simulação (DSSAT/CANEGRO) quanto ao seu desempenho na estimativa do consumo hídrico da cana-de-açúcar. Foram realizadas medidas de evapotranspiração do dossel pelo método do balanço de energia-razão de Bowen (MRB) e de transpiração das plantas por meio do balanço de calor nos colmos (BC) e das folhas com um analisador de gás à infravermelho (IRGA). Duas áreas experimentais foram utilizadas, sendo a primeira com a variedade CTC 12, na safra 2011/2012, irrigada por gotejamento subsuperficial; a segunda área com a variedade RB867515, irrigada por aspersão por meio de um pivô central, na safra 2012/2013. O acoplamento planta-atmosfera também foi avaliado. As análises do MRB indicaram um fluxo de calor latente médio de 70% da energia disponível no ambiente, com 25% de fluxo de calor sensível e 5% no fluxo de calor no solo. Com a mesma metodologia a evapotranspiração da cultura média (ETc) foi estimada em 3,92 e 3,25 mm dia-1 para as variedades CTC 12 e RB867515, respectivamente, resultando em um coeficiente de cultura (Kc) médio de 1,37, na fase de pleno desenvolvimento vegetativo. No período experimental, o canavial permaneceu mais acoplado à atmosfera (&Omega; médio=0,37) e a transpiração avaliada pelo BC chegou a 4,7 e 3,62 mm dia-1, respectivamente para CTC 12 e RB867515. A metodologia do IRGA resultou em perda de água ao nível foliar da faixa de até 1 mm h-1. Conforme a demanda atmosférica, o Kc da cultura apresentou-se variável em função da evapotranspiração de referência (ETo). O modelo DSSAT/CANEGRO mostrou-se eficiente na simulação da ETc e transpiração do canavial, com resultados mais satisfatórios (R2=0,59) quando utiliza-se a metodologia FAO 56 nas simulações. / Global climate change and the sugarcane crop expansion to regions with lower water supply became more important the real estimate of crop water requirements. This study aimed to contribute on this regard by analyzing the sugarcane water consumption at three different spatial scales: leaf, plant and canopy. The DSSAT/CANEGRO crop model was also evaluated with respect to sugarcane transpiration and evapotranspiration. Bowen ratio energy balance (BREB) method was performed to measure crop canopy evapotranspiration and the transpiration were measured with sap flow by stem heat balance for plant scale and infra-red gas analyzer (IRGA) for leaf scale. Two experimental sites were used: the first with CTC 12 cultivar and drip irrigation, on 2011/2012 season; in the second experiment the RB867515 variety was grown under sprinkler irrigation by a central pivot, on the 2012/2013 growing season. The plant-atmosphere decoupling factor was also evaluated. BREB method showed latent heat flux representing 70% of the available energy, 25% for sensible heat flux, and 5% for soil heat flux. BREB crop evapotranspiration (ETc) ranged from 3.92 to 3.25 mm day-1 for CTC 12 and RB867515, respectively, resulting in a mean crop coefficient (Kc) of 1.37 at the full vegetative growth stage. In the experimental period, sugarcane crop was coupled to the atmosphere (&Omega;=0.37) and transpiration assessed by HB reached 4.7 and 3.62 mm day-1 for CTC 12 and RB867515, respectively. IRGA method showed a leaf water loss up to 1 mm h-1. Kc varied with reference evapotranspiration (ETo) The DSSAT/CANEGRO crop model was efficient in the ETc and transpiration simulation, with better results (R2=0.59) when using FAO 56 ETo method in the simulations.