Resumen Considerando la importancia económica de los pastos, existe una necesidad de investigar los parámetros que afectan los coeficientes de cultivo utilizados para el manejo del riego. En este experimento, nuestro objetivo fue determinar el coeficiente de cultivo del pasto ‘Marandu’ en función de la acumulación de grados-días y estimar el consumo de agua del cultivo puro (pasto ‘Marandu’) y del cultivo mixto (pasto ‘Marandu’ + avena negra + raigrás italiano) regí menes de cultivo. La investigación se llevó a cabo en la Escuela de Agricultura Luiz de Queiroz en Piracicaba/SP, Brasil, entre 2016 y 2017, en este periodo se registró la evapotranspiración utilizando lisímetros de pesaje. La evapotranspiración del cultivo se calculó utilizando la variación de peso promedio registrada por lisímetros. Los datos de una estación meteoro lógica automatizada se utilizaron para estimar la evapotranspiración de referencia y calcular los grados-días. Se generaron ecuaciones y modelos de regresión con relación al coeficiente de cultivo y los grados-días acumulados durante dos períodos estacionales (primavera/verano y otoño/invierno). Los modelos matemáticos se probaron durante dos ciclos anuales, de 2015 a 2018 y mostraron mejores resultados, en términos de precisión y exactitud, en el sistema de cultivo único en primavera/verano en los años 2017/18.

Abstract Considering profitability in pasture-based systems, investigating parameters affecting crop coefficients for irrigation management becomes important. In this experiment, we determined the crop coefficient of ‘Marandu’ palisadegrass based on accumulated degree-days and estimated plant water consumption under single (‘Marandu’ palisade grass) and mixed (‘Marandu’ palisadegrass + black oats + Italian ryegrass) cropping regimes. The research was conducted at the Luiz de Queiroz College of Agriculture in Piracicaba, São Paulo, Brazil, between 2016 and 2017. Evapotranspiration was assessed using weighing lysimeters while crop evapotranspiration was calculated using mean weight variation. Reference evapotranspiration and degree-days were estimated. Data were obtained from an automated weather station. Equations and regression models relating crop coefficient with accumulated degree-days were generated for two seasons (spring/summer and autumn/ winter) and evaluated for two year-cycles, from 2015 to 2018. The results showed better prediction accuracy for the single cropping system in spring/summer 2017-18.

ABSTRACT This study aimed to evaluate the production characteristics of pastures in integrated livestock production systems. For that, an experiment was carried out in São Carlos, SP, Brazil, from 2013 to 2015. Forage development, production and nutritive value were evaluated in five beef cattle production systems: extensive continuous stocking (Urochloa decumbens) = EXT; intensive = INT; crop-livestock = iCL; livestock-forest = iLF and crop-livestock-forest = iCLF. Rotational stocking pastures in INT, iCL, iLF and iCLF systems were established with Urochloa brizantha cv. BRS Piatã. In iCL and iCLF, pastures were renovated by resowing the grass simultaneously with corn. In iLF and iCLF, eucalyptus (Eucalyptus urograndis clone GG100) was planted in Apr 2011 in single rows with 15 × 2 m spacing. In the 2013/2014 crop season, INT, iCL, and iCLF pastures were more productive than in iLF and EXT. Shading increase in the 2014/2015 season reduced pasture production in iLF and iCLF, compared with INT and iCL, but increased crude protein content and digestibility. In the shaded systems, pasture production was affected by proximity to trees, mainly due to reductions in solar radiation transmission. The principal component analyses showed that forage accumulation and leaf area index were associated with the position in the middle of the inter-row, and nutritive value was associated with the position at 1.5 m from the trees. In iCLF, solar radiation transmission greater than 60 % maintained forage accumulation similar to iCL, while in iLF, it reduced forage accumulation, evidencing that pasture renovation minimized shading effects in these systems.

Resumo: O objetivo deste trabalho foi caracterizar a variabilidade espacial da resistividade elétrica do solo devido a diferentes umidades do solo, em sistema agropecuário integrado. A resistividade elétrica (RE) do solo foi medida com o sensor de contato “Automatic Resistivity Profiling” (ARP) em duas datas, em 2016, em área de 9,7 ha com diferentes umidades do solo. Os mapas obtidos indicaram que a RE permitiu delimitar as regiões dentro da área de estudo e indicar diferenças do movimento e da acumulação de água nos horizontes do solo. Apesar da tendência de redução dos valores da RE com o aumento da umidade do solo, a estrutura de correlação espacial da RE é similar.

Abstract: The objective of this work was to characterize the spatial variability of soil electrical resistivity due to different soil moisture contents, in an integrated agricultural system. Soil electrical resistivity (ER) was measured with the Automatic Resistivity Profiling (ARP) contact sensor in two dates, in 2016, in a 9.7-ha area with different soil moisture contents. The obtained maps indicated that ER allowed delimiting the regions within the study area and pointing out differences in the movement and accumulation of water in the soil horizons. Although there is a trend of reduction in ER values with increasing soil moisture, the spatial correlation structure of ER is similar.

ABSTRACT: Climate, soil and management are the main drives for growth and production of tropical pastures. Thus, a better understanding of the effects of these factors and their interactions under climate conditions is required to obtain effective management options. Here, we used data from two field trials to research on climate and management interactions on the production seasonality of Panicum maximum Jacq. Treatments included four sampling times (250, 500, 750, and 1000 °C accumulated) during eight regrowth period, under irrigated and rainfed conditions and, cuts were made to simulate grazing intensity. All treatments were arranged in a completely randomized block design with four replications. At each sampling time, basal tillers were sampled to observe meristematic differentiation and were linked with the respective daylength. Soil moisture was determined, and the water availability index (WAI) was calculated. The dry matter production (DMP) was taken and relative productivity was calculated. Soil moisture was the key seasonal drive in spring-summer and the WAI could be used to adjust the maximum production for that season. The major drive for DMP in fall was the daylength, which was found at 11.81 h. For all seasons, DMP correlated better with the residues in early regrowth phase (r = 0.82 and p < 0.0001) and with degree-days at final regrowth phase (r = 0.73 p < 0.01). Applying these critical values to management guidelines should make Guinea grass DMP more efficient on tropical farms.

RESUMO O objetivo desse trabalho foi delimitar áreas aptas e o requerimento hídrico de irrigação para cultivo do capim Tanzânia no estado do Ceará. A produtividade do capim Tanzânia foi obtida a partir de um modelo matemático que assume os valores da evapotranspiração real, resultante do balanço hídrico climatológico da cultura. A necessidade hídrica para reposição de água ao longo do ano para solos com capacidade de água disponível de 20 (solos rasos), 40 (solos arenosos), 60 (solos de textura média) e 100 mm (solos argilosos). A partir da TAMS obteve-se a frequência relativa de ocorrência de produtividade mensal em diferentes municípios Cearense. Os valores de produtividade do capim Tanzânia no estado do Ceará predominaram entre 20.000 e 30.000 kg MS ha-1 ano-1. Durante os meses chuvosos o potencial produtivo varia em função da mesorregião econômica, as quais apresentam condições climáticas distintas. Portanto, o estado do Ceará possui aptidão para produção do capim Tanzânia, sob regime de sequeiro, durante apenas quatro meses, predominantemente, de fevereiro a maio, sendo que as condições climáticas não favorecem o desenvolvimento do capim nos demais meses.

ABSTRACT This study aimed to define areas suitable, and the irrigation water requirement for, cultivation of Tanzania guineagrass in the state of Ceará, Brazil. Tanzania guineagrass yield was estimated by a mathematical model, which considers the crop actual evapotranspiration, resulting from the crop climatological water balance. The water requirement throughout the year was estimated for soils with a water holding capacity of 20 (shallow soils), 40 (sandy soils), 60 (soils with medium texture) and 100 mm (clay soils). The relative frequency of occurrence of monthly productions greater than 2,750 kg DM ha-1 month-1 was obtained for different areas in Ceará, representative of most of the state's economic mesoregions. Tanzania guineagrass annual yields in the state of Ceará were between 20,000-30,000 kg DM ha-1 year-1. During the rainy season, the productive potential varies with the economic mesoregion, which presents different climatic conditions. The state of Ceará is only suitable for the rainfed production of Tanzania guineagrass for 4 months each year, predominantly from February to May, while weather conditions do not favor the development of this grass in the remaining months.

RESUMO Existem poucos estudos sobre arborização de café conilon com seringueira. Objetivou-se avaliar o microclima, desenvolvimento e produtividade do cafeeiro conilon cultivado a pleno sol e sob sombreamento proporcionado pela seringueira. O experimento foi composto por uma lavoura de café conilon (Coffea canephora), cultivada a pleno sol e outra lavoura de café consorciada com seringueira (Hevea brasiliensis). A seringueira e o cafeeiro foram plantados no sentido Leste/Oeste, em Jaguaré, Espírito Santo, Brasil. Avaliou-se a luminosidade, temperatura e umidade relativa do ar, concentração foliar de nutrientes, medição dos internódios dos ramos plagiotrópicos e ortotrópicos, área foliar, índice relativo de clorofila, e a produtividade do cafeeiro. O sombreamento influenciou diretamente no microclima, reduzindo a temperatura do ar no verão e no inverno e aumentando a umidade relativa. A luminosidade no verão teve uma redução media de 905 lumens ft-2 ao longo de todo dia, equivalente a 72,49%, e no inverno de 1665 lumens ft-2, equivalente a 88,04%. O sombreamento proporcionou maior estiolamento dos ramos plagiotrópicos e ortotrópicos, bem como maior expansão foliar. A concentração foliar de Fe e Mn foram maiores no cafeeiro arborizado. A clorofila b e total estimada foram maior no cafeeiro cultivado a pleno sol. O denso sombreamento oferecido pela seringueira nas condições estudadas proporcionou perdas na produtividade do cafeeiro, contudo, ocorre a formação da seringueira.

ABSTRACT There are few studies about the shading of Robusta coffee with rubber trees. The aim of this study was evaluate the microclimate, development and yield of Coffea canephora grown at full sun and shaded by rubber trees. The experiment consisted of a Robusta coffee crop (Coffea canephora) grown at under full sun and another coffee crop intercropped with rubber trees (Hevea brasiliensis). The rubber trees and coffee crop were planted in the East/West direction, in Jaguaré, Espírito Santo, Brazil. Was evaluated the luminosity, temperature and relative humidity, leaf nutrient concentrations; internodes of the plagiotropic and orthotropic branches, leaf area; relative chlorophyll index, and tree yield of the coffee crops. The shading directly influenced the microclimate by reducing the air temperature in the summer and winter, as well as by increasing relative humidity. Luminosity in the summer had an average decrease of 905 lumens ft-2 throughout the day, which was equivalent to 72.49%, and luminosity in the winter had an average decrease of 1665 lumens ft-2, which was equivalent to 88.04%. The shading provided greater etiolation of the plagiotropic and orthotropic branches as well as greater leaf expansion as compared to the full sun. The leaf concentration of Fe and Mn were higher in the shaded coffee. Estimated chlorophyll b and total chlorophyll were greater in the coffee crop grown at under full sun. The dense shading produced by rubber trees provided losses in the coffee crop yield, however, there is the formation of the rubber tree.

RESUMO Sistemas de produção arborizados com eucalipto predominam no Centro e Sudeste do Brasil, com poucos dados sobre o desempenho de espécies florestais nativas nesses sistemas. O objetivo deste trabalho foi avaliar o desenvolvimento de sete espécies florestais nativas em dois tipos de sistemas de consórcio agroflorestal. O experimento foi implantado em 2007 em uma área de 12 ha, no município de São Carlos - SP. Foram plantados: capixingui (Croton floribundus) e mutambo (Guazuma ulmifolia) (tutoras); jequitibá-branco (Cariniana estrellensis), canafistula (Peltophorum dubium) e ipê-felpudo (Zeyheria tuberculosa) (madeireiras); e angico-branco (Anadenanthera colubrina) e pau-jacaré (Piptadenia gonoacantha) (fixadoras de nitrogênio) em dois tipos de sistemas de consórcio, representados por um sistema silvipastoril e um sistema silviagrícola. Os dados foram coletados durante o período de 48 meses. Houve diferença no desenvolvimento das árvores, avaliados por altura, diâmetro de coleto, danos por insetos e por doenças. O sistema silviagrícola propiciou maior desenvolvimento das árvores. As espécies que se destacaram, nos dois sistemas, foram capixingui, mutambo e canafístula. O ipê-felpudo e o jequitibá-branco apresentaram os piores desempenhos. A grande variabilidade apresentada entre os indivíduos indica a possibilidade de ganhos produtivos significativos com trabalhos de melhoramento e seleção dessas espécies.

ABSTRACT Agroforestry systems with eucalyptus prevail in Central and Southeast Brazil, and little information is available about systems using native trees. The aim of the present study was to evaluate the development of seven native tree species grown under two agroforestry systems. The experiment was conducted starting in 2007 in 12-hectare area in the municipality of São Carlos, São Paulo state, Brazil. The tree species planted in the two systems (a silvopastoral system and an agrisilvicultural system) were: 'capixingui' (Croton floribundus) and 'mutambo' (Guazuma ulmifolia) (tutors), 'jequitibá-branco' (Cariniana estrellensis), 'canafistula' (Peltophorum dubium) and 'ipê felpudo' (Zeyheria tuberculosa) (timber trees), and 'angico-branco' (Anadenanthera colubrina) and 'pau-jacaré' (Piptadenia gonoacantha) (N-fixing trees). Data were collected for 48 months. The results show differences among tree development, which was evaluated as growth in height and diameter, as well as sensitivity to insect and disease damage. The overall results show that the agrisilvicultural system allowed better tree development. The species with best performance in the two systems were capixingui, mutambo and canafístula. Ipê-felpudo and jequitibá-branco showed the worst results. The high variability among individuals of the same species indicates the possibility of high production advances with selective breeding of these species.

RESUMO Estudou-se o efeito da desrama no restabelecimento do equilíbrio em sistema silviagrícola, implantado em São Carlos, SP em 2008. Sete espécies de árvores nativas, na densidade de 600 arvores/ha, foram plantadas em cinco faixas de três linhas, associadas a cultivos agrícolas anuais semeados nos 17 m entre essas faixas. A competição se estabeleceu aos 35 meses, reduzindo a produção de biomassa aérea do milho plantado próximo às árvores. Avaliação do cultivo de aveia-preta na estação seca subsequente a desrama mostrou que as árvores provocaram redução na densidade de plantas e de panículas, na produção de biomassa aérea, na quantidade de grãos por panícula e no peso dos grãos. A desrama das árvores não foi suficiente para controlar a queda da produção agrícola, justificando a indicação de desbaste para manutenção da produtividade do cultivo agrícola.

ABSTRACT The degree to which pruning helps reestablish balance in agroforestry was assessed in a system established in São Carlos, São Paulo, Brazil, in 2008. Seven native tree species were planted at a density of 600 trees/ha in five strips of three rows each, and annual crops were cultivated in the 17-m crop strips between the tree strips. Competition was established after 35 months, decreasing the aboveground biomass production of corn planted close to the trees. An assessment of black oats in the dry season following tree pruning showed that the proximity of trees caused reductions in plant and panicle density, aboveground biomass production, number of grains per panicle and grain weight. Because pruning was not sufficient to maintain crop yields, tree thinning is recommended in order to minimize competition and restore conditions for adequate crop production.

Foram avaliados métodos de estabelecimento de um coquetel de leguminosas forrageiras herbáceas (Centrosema acutifolium, Clitoria ternatea, Pueraria phaseoloides, Estilosantes Campo Grande (Stylosanthes capitata+ S. macrocephala), Calopogonium mucunoides, Lablab purpureus, Arachis pintoi e Aeschynomene vilosae) sob a sombra promovida por um bosque de Eucalyptus grandis submetido a corte de raleamento (40%) oito anos após haver sido plantado em Anhembi, SP (22°40'S, 48°10'W, 455 m de altitude). O experimento foi implantado em dezembro de 2008, sendo comparadas quatro formas de enterrio das sementes por meio de gradagem leve, quais sejam: semeadura superficial a lanço não seguida de incorporação (1), gradagem antes (2) ou depois (3) da semeadura e gradagem antes e depois da semeadura (4). Noventa dias após a semeadura, o número de plantas de leguminosa/m2 e a porcentagem de cobertura do solo pelas plantas variaram entre os tratamentos testados, os quais, entretanto, não tiveram efeito sobre o acúmulo de matéria seca das plantas de leguminosas. A gradagem antes do plantio proporcionou resultados superiores aos tratamentos sem gradagem e com gradagem após o plantio. Ao final do período experimental, as parcelas eram compostas por arachis, centrosema, estilosantes e pueraria. A matéria seca oriunda da centrosema correspondeu a 73% do total das parcelas. A participação de arachis, centrosema e de estilosantes na composição final da matéria seca das parcelas variou com o método de implantação. Foram também discutidas as vantagens do uso de coquetel de espécies em relação ao plantio puro no sub-bosque de plantação florestal.

This study evaluated establishment methods for a mixture of herbaceous forage legumes [Centrosema acutifolium, Clitoria ternatea, Pueraria phaseoloides, Stylosanthes Campo Grande (Stylosanthes capitata + S. macrocephala), Calopogonium mucunoides, Lablab purpureus, Arachis pintoi, and Aeschynomene villosa] under the shade of an Eucalyptus grandis plantation submitted to thinning (40%) 8 years after planting in Anhembi, São Paulo (22°40'S, 48°10'W, altitude of 455 m). The experiment started in December 2008 and consisted of the comparison of the following four types of seed incorporation by light disc harrowing: (1) broadcast sowing without seed incorporation; disc harrowing before (2) or after (3) planting, and (4) disc harrowing before and after planting. Ninety days after planting, the number of legume plants/m2 and the percentage of ground cover by the plants varied between the treatments tested; however, the treatments had no effect on the dry matter accumulation of forage legumes. Disc harrowing before planting yielded superior results compared to the treatments without disc harrowing and disc harrowing after planting. At the end of the experimental period, the plots contained Arachis, Centrosema, Stylosanthes, and Pueraria. The dry matter accumulated by Centrosema corresponded to 73% of total dry matter yield of the plots. The participation of Arachis, Centrosema and Stylosanthes in final dry matter composition of the plots varied according to establishment method. The advantages of the use of species mixtures rather than monocultures in the understory of forest plantations were discussed.

In this study, the microclimate changes in silvopastoral systems are quantified at different time and spatial scales and compared with single-pasture systems. The study was conducted in a silvopastoral system in São Carlos, Brazil (22°01' South and 47°53' West). The silvopastoral system consisted of grass pastures [Urochloa (sin. Brachiaria) decumbens cv. Basilik] lined with strips of native trees spaced at 17 m. Continuous microclimate measurements (air temperature, relative humidity, wind speed, and incident photosynthetically active radiation) were carried out from September 2010 to September 2012 at two positions of the silvopastoral system (2.0 and 8.5 m from the rows of trees) and at a pasture under full sunlight, located in an adjacent area. The soil moisture was monitored weekly from 24 March 2010 to 1 April 2012 at distances of 0.0, 2.0, 4.75, and 8.5 m from the rows of trees. The rows of native trees reduced wind speeds (46% reduction) and changed the photosynthetically active radiation incidence pattern on the pasture (up to 40% reduction of incidence at the point nearest to the trees). The combined action of these factors promoted thermal and air humidity changes on the pasture at the different points measured. With respect to soil moisture, there was greater soil moisture removal at the sampling points near the rows of native trees under the silvopastoral system, mainly due to enhanced exploration by tree roots at greater depths in dry spells or early dry periods, when compared with the midpoints between the rows.

O objetivo deste trabalho foi analisar cenários futuros da produção de forragem de capim-marandu, submetido às mudanças climáticas, no Estado de São Paulo. Utilizou-se um modelo de cultivo empírico para estimar a produção, de acordo com os graus-dia de desenvolvimento ajustados pelo fator de penalização hídrica. Dados climáticos de 23 estações meteorológicas, observados de 1963 a 2009, foram utilizados para caracterizar as condições climáticas atuais. Projeções regionalizadas de dois modelos de circulação global foram utilizadas para projetar o clima futuro, para os períodos de 2013-2040 e 2043-2070, considerando-se dois níveis contrastantes de aumento de temperatura e concentração atmosférica de CO2 (alto e baixo). A produção anual de matéria seca poderá ser de 14 a 42% superior ao acúmulo atual, a depender do cenário avaliado. A variação do acúmulo deverá aumentar entre estações (sazonalidade) e entre anos. O aumento da taxa de acúmulo de forragem será maior na estação chuvosa do que na seca, e este resultado é mais evidente para solos com baixa capacidade de armazenamento de água. Os resultados variaram significativamente entre as regiões (<10% a >60%). Apesar de seu maior potencial climático, as regiões mais quentes provavelmente terão menor incremento na futura produção de forragem.

The objective of this work was to analyze future scenarios for palisade grass yield subjected to climate change for the state of São Paulo, Brazil. An empirical crop model was used to estimate yields, according to growing degree-days adjusted by one drought attenuation factor. Climate data from 1963 to 2009 of 23 meteorological stations were used for current climate conditions. Downscaled outputs of two general circulation models were used to project future climate for the 2013-2040 and 2043-2070 periods, considering two contrasting scenarios of temperature and atmospheric CO2 concentration increase (high and low). Annual dry matter yield should be from 14 to 42% higher than the current one, depending on the evaluated scenario. Yield variation between seasons (seasonality) and years is expected to increase. The increase of dry matter accumulation will be higher in the rainy season than in the dry season, and this result is more evident for soils with low-water storage capacity. The results varied significantly between regions (<10% to >60%). Despite their higher climate potential, warmer regions will probably have a lower increase in future forage production.

O objetivo deste trabalho foi avaliar a produtividade e as características biométricas do capim-braquiária (Urochloa decumbens) sob pastejo, em sistema silvipastoril. Avaliou-se um sistema com árvores nativas de interesse comercial, plantadas em renques, no sentido norte-sul, espaçados por 17 m. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repetições e parcelas subdivididas, tendo-se avaliado o ciclo de rebrota da forragem nas parcelas, e a distância desta em relação aos renques, nas subparcelas. Sete ciclos de rebrota foram avaliados, em quatro distâncias dos renques: a 2 e a 6 m do renque leste, e a 2 e a 6 m do renque oeste. Quantificou-se a produtividade de matéria seca, o índice de área foliar (IAF), a área foliar específica (AFE) e a altura das plantas. A produtividade de forragem, nos dois primeiros ciclos, e o IAF, no segundo e no terceiro ciclo, diminuiram com níveis de sombra acima de 39 e 40%, respectivamente. Já a altura de plantas aumentou com sombreamentos superiores a 53%, nos quatro primeiros ciclos; o que também ocorreu com a AFE, com sombreamento superior a 66%, nos três primeiros ciclos.

The objective of this work was to evaluate the productivity and biometric characteristics of signal grass (Urochloa decumbens) under grazing, in a silvopastural system. A system with native trees of commercial interest, planted in a set of rows with north-south orientation, with 17 m spacing was evaluated. A randomized complete block design with four replicates was carried out in a split-plot arrangement, with forage grass regrowth cycles evaluated in the plots and distances from trees in the subplots. Seven regrowth cycles were evaluated at four distances of the set of tree rows: at 2 and 6 m from trees at east, and at 2 and 6 m from trees at west. Dry matter productivity, leaf area index (LAI), specific leaf area (SLA), and plant height were measured. Forage productivity in the first two cycles and LAI in the second and third cycles reduced with shading levels higher than 39 and 40%, respectively. However, plant height increased with shadings greater than 53%, in the first four cycles, and SLA with shadings greater than 66%, in the first three cycles

Two cultivars of Brachiaria brizantha (Hochst ex. A. Rich) Stapf. (Syn. Urochloa) were evaluated for their adaptation to water deficit and the stress response mechanisms in a greenhouse experiment. The experimental design was in completely randomized blocks with a 2 × 2 × 4 factorial arrangement. The Marandu and BRS Piatã cultivars were evaluated under two water availability conditions, with or without water restriction. The harvests were carried out 0, 7, 14 and 28 days after the start of water restriction. For both cultivars, the water deficit stress caused a reduction in shoot biomass and leaf area and an increase in the percentage of roots in the deeper soil layers. The B. brizantha cv. Marandu reached critical levels of leaf water potential in a shorter period of water restriction than did the B. brizantha cv. BRS Piatã. The osmoregulation and deepening of the root system are mechanisms of adaptation to water stress observed in both Marandu and BRS Piatã cultivars. Besides that, the Marandu cultivar also increases its leaf senescence and, consequentially, decreases its leaf area, as a response to water deficit.

Neste trabalho, objetivou-se analisar a influência de níveis de deficit hídrico (DH), sobre o crescimento inicial de mudas de seis clones do híbrido Eucalyptus grandis x E. urophylla em duas épocas do ano. O experimento foi realizado na área experimental da UFES, no município de Jerônimo Monteiro, ES, em duas épocas: de 09/02/09 a 09/06/09 (época 1) e 11/07/09 a 07/11/09 (época 2). Em todos os tratamentos, os primeiros 30 dias de experimento foram o período de aclimatação das mudas ao solo e, portanto, ambos eram irrigados. Os níveis de DH foram: D0: sem deficit; D1): 90 dias de DH; D2: 60 dias de DH e retomada da irrigação por mais 30 dias e D3: 30 dias de irrigação e 60 dias de DH. O delineamento experimental utilizado foi o inteiramente ao acaso, em parcelas subdivididas 2x4, sendo os quatro (4) níveis de DH na parcela e as duas (2) épocas nas subparcelas, com três repetições. Os dados de matéria seca total, de folhas, de haste e ramos e raiz foram submetidos à análise de variância, e quando significativas, as médias foram comparadas pelo teste de média Tukey, a 5% de probabilidade. As condições ambientais da época 1 favoreceram a produção de matéria seca dos dois clones e a época 2 com condições climáticas mais amenas não proporcionou o crescimento potencial das mudas, nem mesmo em condições irrigadas satisfatoriamente. Os níveis dos deficit reduziram a produção de matéria seca de maneira gradativa, porém sem seguir um padrão de redução.

This study aimed to analyze the influence of different levels of water deficit (DH) on initial seedling development of six clonal stands of hybrid Eucalyptus grandis x E. urophylla in two seasons of the year. The experiment was conducted in the experimental site of UFES, in the municipality of Jerônimo Monteiro (ES), over two seasons: from February 9, 2009 to June 9, 2009 (season 1) and from July 11, 2009 to November 7, 2009 (season 2). In all experimental treatments, the first 30 days consisted of acclimating seedlings to the soils, which were thus irrigated. DH levels used in the experiment included: D0 - no water deficit; D1 - 90 days of water deficit; D2 - 60 days of water deficit followed by resumed irrigation for 30 days; D3 - 30 days of irrigation and 60 days of water deficit. The experiment was laid out in a completely randomized design, in subdivided plots (2x4), with four (4) levels of water deficit in the plot and two (2) seasons in the subplots, using three replications. Data on total dry matter of leaves, stem and branches, and root were subjected to analysis of variance and, if found significant, means were compared by the Tukey test at the 5% probability level. The environmental conditions of season 1 favored dry matter yield from both clonal stands, while season 2, having milder climate conditions, failed to favor potential growth of seedlings, even with irrigation conditions being satisfactory. Different levels of water deficit gradually reduced dry matter yield, yet without following a pattern of reduction.

O objetivo deste trabalho foi desenvolver e validar modelos de regressão linear para a estimativa de produção de matéria seca de capim‑tanzânia (Megathyrsus maximus, cultivar Tanzania) em função de variáveis agrometeorológicas. Para tanto, dados de períodos de crescimento da forragem entre 2000 e 2005, em condições de sequeiro em São Carlos, SP, foram correlacionados aos seguintes parâmetros climáticos: temperaturas mínima e média, graus‑dia, evapotranspiração potencial e atual. Foram realizadas regressões lineares simples entre as variáveis agrometeorológicas (independentes) e a taxa média de acúmulo (dependente). As estimativas foram validadas com dados independentes obtidos em São Carlos e Piracicaba, SP. Os melhores resultados estatísticos observados no desenvolvimento e na validação dos modelos foram obtidos para parâmetros agrometeorológicos que levem em consideração o efeito térmico e hídrico conjuntamente, como evapotranspiração real, acúmulo de graus‑dia corrigido pela disponibilidade hídrica e índice climático de crescimento, baseado na temperatura média, na radiação solar e na disponibilidade hídrica. Essas variáveis podem ser utilizadas em simulações e modelos para prever a produção do capim‑tanzânia.

The objective of this work was to develop and validate linear regression models to estimate the production of dry matter by Tanzania grass (Megathyrsus maximus, cultivar Tanzania) as a function of agrometeorological variables. For this purpose, data on the growth of this forage grass from 2000 to 2005, under dry‑field conditions in São Carlos, SP, Brazil, were correlated to the following climatic parameters: minimum and mean temperatures, degree‑days, and potential and actual evapotranspiration. Simple linear regressions were performed between agrometeorological variables (independent) and the dry matter accumulation rate (dependent). The estimates were validated with independent data obtained in São Carlos and Piracicaba, SP, Brazil. The best statistical results in the development and validation of the models were obtained with the agrometeorological parameters that consider thermal and water availability effects together, such as actual evapotranspiration, accumulation of degree‑days corrected by water availability, and the climatic growth index, based on average temperature, solar radiation, and water availability. These variables can be used in simulations and models to predict the production of Tanzania grass.