Nitrogen balance and gap of a high yield tropical soybean crop under irrigation.

Nitrogen (N) is the most extracted and exported element by the soybean crop. In high yield tropical environments with irrigation, little is known about N accumulation in different soybean plant organs as well as the N balance. The objective of this study was to characterize soybean growth, N accumulation in plant organs, N balance, and N gap in a high yield tropical environment. This study was performed in a homogeneous field, in a soil with low organic matter, with 20 kg ha-1 of N, under furrow fertilization. Evaluations were performed ten times, temporally distributed from emergence to senescence. The soybean cultivar used was 'RK7518 IPRO' and was sown with row spacing of 0.45 m and a seeding rate of 300,000 plants ha-1. Plant N partition, N from the biological N fixation (BNF), grain yield, crop harvest index (HI), N harvest index (NHI) with and without root contribution were evaluated. Also, at the grain filling stage the N gap was evaluated from the soil by difference between whole plant accumulated N and the amount of N from BNF. The average grain yield was 6,470 kg ha-1 and leads to a negative partial balance of N of -33.4 and -42.8 kg[N] ha-1 with and without roots, respectively. The N gap from the soil was 231.7 kg[N] ha-1. It is recommended to adopt techniques that increase the efficiency of BNF and the soil N accumulation to balance these production systems in the medium to long term.

Changes in soybean cultivars released over the past 50 years in southern Brazil.

On-farm soybean yield has increased considerably in the last 50 years in southern Brazil, but there is still little information about how selection and breeding for yield increase has changed the agronomic attributes of cultivars. The objectives of this study were to evaluate the changes in soybean yield, seed oil and protein concentration, and changes in plant attributes that might be associated with yield improvement of 26 soybean cultivars released over the past 50 years in southern Brazil, sown simultaneously in a common field environment for two growing seasons. The average rate of yield gain was 45.9 kg ha-1 yr-1 (2.1% ha-1 yr-1), mainly due increased seed number per area and harvest index. Over year of cultivar release, cultivars became less susceptible to lodging, as well as plant mortality reduced. Meanwhile, the seed oil concentration increased, and seed protein concentration decreased, which could have negative consequences for soybeans use and requires further attention for breeding of future cultivars. Breeders have successfully contributed to the annual rate of soybean yield increase in southern Brazil. By our results, as well as the official on-farm production data, there is no evidence of soybean yield reaching a plateau in the near future in southern Brazil.

Novel Tools for Adjusting Spatial Variability in the Early Sugarcane Breeding Stage.

The detection of spatial variability in field trials has great potential for accelerating plant breeding progress due to the possibility of better controlling non-genetic variation. Therefore, we aimed to evaluate a digital soil mapping approach and a high-density soil sampling procedure for identifying and adjusting spatial dependence in the early sugarcane breeding stage. Two experiments were conducted in regions with different soil classifications. High-density sampling of soil physical and chemical properties was performed in a regular grid to investigate the structure of spatial variability. Soil apparent electrical conductivity (ECa) was measured in both experimental areas with an EM38-MK2® sensor. In addition, principal component analysis (PCA) was employed to reduce the dimensionality of the physical and chemical soil data sets. After conducting the PCA and obtaining different thematic maps, we determined each experimental plot's exact position within the field. Tons of cane per hectare (TCH) data for each experiment were obtained and analyzed using mixed linear models. When environmental covariates were considered, a previous forward model selection step was applied to incorporate the variables. The PCA based on high-density soil sampling data captured part of the total variability in the data for Experimental Area 1 and was suggested to be an efficient index to be incorporated as a covariate in the statistical model, reducing the experimental error (residual variation coefficient, CVe). When incorporated into the different statistical models, the ECa information increased the selection accuracy of the experimental genotypes. Therefore, we demonstrate that the genetic parameter increased when both approaches (spatial analysis and environmental covariates) were employed.

Endophytic Fungi: Biological Control and Induced Resistance to Phytopathogens and Abiotic Stresses.

Plant diseases cause losses of approximately 16% globally. Thus, management measures must be implemented to mitigate losses and guarantee food production. In addition to traditional management measures, induced resistance and biological control have gained ground in agriculture due to their enormous potential. Endophytic fungi internally colonize plant tissues and have the potential to act as control agents, such as biological agents or elicitors in the process of induced resistance and in attenuating abiotic stresses. In this review, we list the mode of action of this group of microorganisms which can act in controlling plant diseases and describe several examples in which endophytes were able to reduce the damage caused by pathogens and adverse conditions. This is due to their arsenal of molecules generated during the interaction by which they form a kind of biological shield in the plant. Furthermore, considering that endophytic fungi can be an important tool in managing for biotic and abiotic stresses due to the large amount of biologically active substances produced, bioprospecting this class of microorganisms is tending to increase and generate valuable products for agriculture.

Soybean seed treatment: how do fungicides translocate in plants?

BACKGROUND: Soybean seed treatment with fungicides is a well-established disease management strategy. However, the movement of these fungicides within seedlings is not always well characterized. Thus, the objectives of this study were to determine the pattern of translocation of three fungicides with different modes of action applied as a seed treatment, and the effect of soil type on translocation. RESULTS: Most of the absorbed radioactivity was concentrated in the cotyledons and the maximum sum of the rates of absorption by roots, stems, and leaves of the plants was 15%. In most cases, absorption by roots, stems, and leaves were lower than 5% for 14 C-pyraclostrobin and 14 C-metalaxyl, and 1.6% for 14 C-carbendazim. Fungicides absorbed by the roots and the whole seedlings were higher when plants were grown in soil with lower organic matter content. Fungicides in the cotyledons are unlikely to be redistributed and are lost when cotyledons fall off the plants. CONCLUSION: Cotyledons are the part of the plant where fungicides are most absorbed, regardless of the fungicide. Soil type affects the absorption of fungicides, and in this study it was most likely caused by soil organic matter. These data improve knowledge of the movement of seed treatment fungicides in soybean seedlings and may help the development of seed treatment chemistry to manage seed and soilborne pathogens.

Preliminary Studies to Characterize the Temporal Variation of Micronutrient Composition of the Above Ground Organs of Maize and Correlated Uptake Rates.

The improvement of agronomic practices and the use of high technology in field crops contributes for significant increases in maize productivity, and may have altered the dynamics of nutrient uptake and partition by the plant. Official recommendations for fertilizer applications to the maize crop in Brazil and in many countries are based on critical soil nutrient contents and are relatively outdated. Since the factors that interact in an agricultural production system are dynamic, mathematical modeling of the growth process turns out to be an appropriate tool for these studies. Agricultural modeling can expand our knowledge about the interactions prevailing in the soil-plant-atmosphere system. The objective of this study is to propose a methodology for characterizing the micronutrient composition of different organs and their extraction, and export during maize crop development, based on modeling nutrient uptake, crop potential evapotranspiration and micronutrient partitioning in the plant, considering the production environment. This preliminary characterization study (experimental growth analysis) considers the temporal variation of the micronutrient uptake rate in the aboveground organs, which defines crop needs and the critical nutrient content of the soil solution. The methodology allowed verifying that, initially, the highest fraction of dry matter, among aboveground organs, was assigned to the leaves. After the R1 growth stage, the largest part of dry matter was partitioned to the stalk, which in this growth stage is the main storage organ of the maize plant. During the reproductive phase, the highest fraction of dry matter was conferred to the reproductive organs, due to the high demand for carbohydrates for grain filling. The micronutrient (B, Cu, Fe, Mn, and Zn) content follows a power model, with higher values for the initial growth stages of development and leveling off to minimum values at the R6 growth stage. The proposed model allows to verify that fertilizer recommendations should be related to the temporal variability of micronutrient absorption rates, in contrast to the classic recommendation based on the critical soil micronutrient content. The maximum micronutrient absorption rates occur between the reproductive R4 and R5 growth stages. These evaluations allowed to predict the maximum micronutrient requirements, considered equal to respective stalk sap concentrations.

Maize dry matter production and macronutrient extraction model as a new approach for fertilizer rate estimation.

Decision support for nutrient application remains an enigma if based on soil nutrient analysis. If the crop could be used as an auxiliary indicator, the plant nutrient status during different growth stages could complement the soil test, improving the fertilizer recommendation. Nutrient absorption and partitioning in the plant are here studied and described with mathematical models. The objective of this study considers the temporal variation of the nutrient uptake rate, which should define crop needs as compared to the critical content in soil solution. A uniform maize crop was grown to observe dry matter accumulation and nutrient content in the plant. The dry matter accumulation followed a sigmoidal model and the macronutrient content a power model. The maximum nutrient absorption occurred at the R4 growth stage, for which the sap concentration was successfully calculated. It is hoped that this new approach of evaluating nutrient sap concentration will help to develop more rational ways to estimate crop fertilizer needs. This new approach has great potential for on-the-go crop sensor-based nutrient application methods and its sensitivity to soil tillage and management systems need to be examined in following studies. If mathematical model reflects management impact adequately, resources for experiments can be saved.

Maize dry matter production and macronutrient extraction model as a new approach for fertilizer rate estimation

ABSTRACT Decision support for nutrient application remains an enigma if based on soil nutrient analysis. If the crop could be used as an auxiliary indicator, the plant nutrient status during different growth stages could complement the soil test, improving the fertilizer recommendation. Nutrient absorption and partitioning in the plant are here studied and described with mathematical models. The objective of this study considers the temporal variation of the nutrient uptake rate, which should define crop needs as compared to the critical content in soil solution. A uniform maize crop was grown to observe dry matter accumulation and nutrient content in the plant. The dry matter accumulation followed a sigmoidal model and the macronutrient content a power model. The maximum nutrient absorption occurred at the R4 growth stage, for which the sap concentration was successfully calculated. It is hoped that this new approach of evaluating nutrient sap concentration will help to develop more rational ways to estimate crop fertilizer needs. This new approach has great potential for on-the-go crop sensor-based nutrient application methods and its sensitivity to soil tillage and management systems need to be examined in following studies. If mathematical model reflects management impact adequately, resources for experiments can be saved.

Ação de bioestimulante no desempenho agronômico de milho e feijão / Biostimulant action on agronomic efficiency of corn and common beans

Os biorreguladores têm sido amplamente aplicados na produção agrícola, e desempenham um papel importante, no crescimento e desenvolvimento das plantas, principalmente em culturas de alto nível tecnológico. Dessa forma, objetivou-se com o presente trabalho avaliar o desempenho agronômico das plantas e o seu rendimento com uso de bioestimulante nas culturas do milho e do feijão. Foram realizados dois experimentos independentes, com a cultura do milho e do feijão, em que os tratamentos utilizados constituíram-se de diferentes doses e formas de aplicação (tratamento de sementes, pulverização na fileira de semeadura e pulverização foliar). O produto utilizado é composto de 0,5 g L-1 ácido indol butírico, 0,9 g L-1 de cinetina e 0,5 g L-1 de ácido giberélico. Avaliaram-se as características: número médio de plantas por metro; diâmetro dos colmos; número de fileiras de grãos por espiga; número de grãos por fileira; número de grãos por espiga; massa de mil grãos e produção de grãos na cultura do milho e número médio de plantas por metro; número de vagens por planta; número de grãos por planta; massa de mil grãos e produção de grãos na cultura do feijão. Conclui-se que o uso de bioestimulante, em milho, proporciona aumento do diâmetro do colmo das plantas de milho, número de grãos por fileira e número de grãos por espiga, porém não interfere o rendimento da cultura. Em feijão, o uso de bioestimulantes, nas diferentes doses e formas de aplicação aumenta o número de grãos por planta e a produção de grãos.

The plant growth regulators have been intense and largely applied in agricultural production, and play an important role in the growth and development of plants, especially in cultures with high level of technology. Thus, the aim of the present study was to evaluate the agronomic performance of plants and their yield with the use of biostimulant in corn and beans. There were two independent experiments with corn and beans, in which the treatments consisted of three doses and three forms of application (seed treatment, spray in row sowing and foliar spray). The product used is composed of 0,5 g L-1 indole butyric acid, 0,9 g L-1 kinetin and 0,5 g L-1 gibberellic acid. Evaluated the characteristics: the average number of plants per meter, stem diameter, number of kernel rows per ear, number of kernels per row, number of grains per spike, thousand grain weight and grain yield in maize and average number of plants per meter, number of pods per plant, number of grains per plant, thousand grain weight and yield in bean plants. Conclude that the use of bio-stimulant in corn, provides increased stem diameter of maize plants, number of kernels per row, number of grains per spike, but does not interfere crop yield. In beans, using biostimulants in different doses and forms of application increases the number of grains per plant and grain yield.

Produção e composição química de hortaliças folhosas em hidroponia / Production and chemical composition of vegetables hardwood in hydroponics

O cultivo hidropônico de hortaliças folhosas vem crescendo acentuadamente nos últimos anos, no entanto, pouco se sabe sobre sua composição química, o que é de extrema importância, tendo em vista a mudança de hábito alimentar de uma fração considerável da população brasileira que busca alimentos de qualidade. Por essa razão, as culturas de agrião, chicória, rúcula e alfaces americana (cv. Lucy Brown) e lisa (cv. Regina) foram produzidas em hidroponia, sistema NFT, buscando-se avaliar o rendimento, teor de nitrato e composição centesimal. O experimento foi conduzido em casa de vegetação, na Universidade Federal de Santa Catarina, Florianópolis (SC), no período de maio a julho de 2004, sob delineamento inteiramente casualizado com 4 repetições. O espaçamento utilizado foi de 25 cm x 25 cm para as culturas do agrião, chicória e alface (cv. Lucy Brown e cv. Regina) e de 5 cm x 5 cm para a rúcula. A alface cv. Regina e a chicória apresentaram maior número de folhas por planta. O agrião apresentou menor teor de água e maior fitomassa seca da parte aérea. Maior incremento de fitomassa fresca foi obtido na chicória, alface cv. Lucy Brown" e cv. Regina. Maiores teores de lipídios, proteína, resíduo mineral, carboidratos, valor calórico, nitrato e de fibra foram obtidos no agrião. A rúcula apresentou menores valores para as variáveis fitomassa fresca e seca da planta inteira, da parte aérea e da raiz, e número de folhas por planta. Todas as culturas apresentaram boa aparência visual, baixo valor calórico e teores de nitrato adequados ao consumo humano.

The hydroponic cultivation of vegetables has increased markedly in recent years, however, little is known about its chemical composition, which is of extreme importance in view of changing food habits of a considerable fraction of the population seeking food quality. For this reason, cultivation of watercress, chicory, rocket and lettuce American (Lucy Brown) and smooth (cv. Regina) were grown in hydroponics, NFT system, aiming to evaluate the yield, nitrate content and chemical composition. The experiment was conducted in a greenhouse at the Universidade Federal de Santa Catarina, Florianopolis city in the Santa Catarina State (Brazil), from may to july 2004 under a completely randomized design with four replications. The spacing used was 25 x 25 cm for the crops of watercress, chicory and lettuce (cv. Lucy Brown and cv. Regina) and 5 x 5 cm to the rocket. The traits were: number of leaves, nitrate content and chemical composition of vegetables. The lettuce cv. Regina and chicory had higher number of leaves per plant. The watercress had lower water content and higher dry mass of shoots. The largest increase in fresh weight was obtained in chicory, lettuce, cv. Regina. Higher levels of lipids, protein, ash, carbohydrates, calories, fiber and nitrate were obtained from the watercress. The rocket had lower values for the variables fresh and dries the whole plant, shoot and root and leaf number per plant. All cultures showed good visual appearance, low calorie and nitrate levels suitable for human consumption.

Balanço hídrico climatológico, armazenamento efetivo da água no solo e transpiração na cultura de café / Climatological hydric balance, effective soil water storage and transpiration in coffee culture

O balanço hídrico climatológico é uma das ferramentas mais usadas para se avaliar, indiretamente, se a quantidade de água presente no solo é capaz de suprir as necessidades hídricas da planta. Este trabalho teve como objetivos analisar o balanço hídrico climatológico, o armazenamento efetivo da água no solo e a transpiração de plantas de café cultivadas em regime de sequeiro. Para tanto, foi calculado o balanço hídrico climatológico diário do cafeeiro cultivado em região de cerrado no município de Uberlândia-MG, no período de janeiro de 2003 a maio de 2006. Concluiu-se que mesmo nos meses mais chuvosos do ano, há a existência de déficit hídrico em plantas de café conduzidas sob regime de sequeiro; o armazenamento efetivo da água do solo sofreu muita variação ao longo dos anos avaliados, sendo setembro, o mês onde esse valor é mais crítico, permanecendo abaixo de 30%; a transpiração relativa não pode ser tomada como único método de avaliação da queda de produtividade de plantas de café, conduzidas sob regime de sequeiro.

The climatic water balance is one of the most used tools to assess, indirectly the amount of water present in the soil is capable of meeting the water needs of the plant. This study analyzed the climatologic hydric balance, the effective soil water storage and coffee plant transpiration in dry regimen cultivation. Daily climatologic hydric balance was calculated for coffee from January 2003 to May 2006. It was concluded that even in the most rainy months of the year, there is a hydric deficit in coffee plants grown in a dry regimen; effective soil water storage varied greatly through the years evaluated, and September was the most critical month, when this value remained below 30%; relative transpiration can not be taken as the single evaluation method for yield losses of coffee, grown in a dry regimen

Expolinear model on soybean growth in Argentina and Brazil / Modelo expolinear na cultura da soja cultivada na Argentina e no Brasil

Predicting crop growth and yield with precision are one of the main concerns of the agricultural science. For these purpose mechanistic models of crop growth have been developed and tested worldwide. The feasibility of an expolinear model for crop growth was evaluated on predicting growth modification on soybean (Glycine max L. Merrill) of determined and undetermined growth cultivars, submitted to water restrictions imposed on different phenological stages. An experiment was carried out in Azul/Argentina and in Viçosa/Brazil during the growing seasons (1997/1998, 1998/1999 and 2002/2003). The expolinear model was adjusted to the dry-matter data obtained from each treatment. The model showed sensibility of Rm (maximum relative growth rate of the culture - g g-1 day-1) to variation in air temperature; of Cm (maximum growth rate of the culture - g m-2 day-1) to solar radiation and of Tb (lost time -day) to water stress. Cm values were higher without water restriction presenting, in both countries, a direct correlation with solar radiation. Without water restrictions, Rm values were lower when the average air temperature during the cycle was lower. It was observed that under water stress the culture had a bias to present higher Rm values. Tb was lower in the irrigated treatments than in those with water deficits. The analysis of the outputs clearly shows the feasibility of the expolinear model to explain the differential growth rates of soybean as a consequence of climatic conditions.

Prever o crescimento e a produtividade das culturas com precisão é uma das principais preocupações das ciências agrícolas. Com esse propósito, modelos mecanísticos de crescimento de culturas têm sido desenvolvidos e testados. A adequação do modelo expolinear de crescimento de culturas foi avaliada para prever as modificações de crescimento de cultivares de soja (Glycine max L. Merrill) de crescimento determinado e indeterminado, submetidas a déficit hídrico em diferentes estádios fenológicos. Um experimento foi conduzido em Azul/Argentina e outro em Viçosa/Brasil durante as estações de cultivo (1997/1998, 1998/1999 e 2002/2003). O modelo expolinear foi ajustado aos dados de fitomassa seca obtidos de cada tratamento. O modelo apresentou sensibilidade do parâmetro Rm (taxa máxima de crescimento relativo da cultura - g g-1 day-1) à variação na temperatura do ar; do parâmetro Cm (taxa máxima de crescimento da cultura - g m-2 day-1) à radiação solar; e do parâmetro Tb (perda em tempo - dias) ao estresse hídrico. Os valores de Cm foram maiores sem restrições hídricas, apresentando, em ambos os países, uma correlação direta com a radiação solar. Sem restrições hídricas, os valores de Rm foram menores quando a temperatura média do ar durante o ciclo foi menor. Sob estresse hídrico, a cultura mostrou uma tendência a apresentar valores de Rm maiores. Os valores de Tb foram menores nos tratamentos irrigados e maiores nos tratamentos com deficiência hídrica. A análise dos resultados mostrou claramente a capacidade do modelo expolinear para simular as diferentes taxas de crescimento da cultura da soja como uma consequência das condições climáticas.

Temperatura base inferior e estacionalidade de produção de genótipos diplóides e tetraplóides de azevém / Lower base temperature and seasonal production of diploid and tetraploid ryegrass genotypes

O trabalho tem por objetivo estimar a temperatura base (Tb) para três genótipos diplóides (Comum, Fepagro São Gabriel e LE 284) e dois tetraplóides (Avance e INIA Titán) de azevém. Com os valores de Tb, o trabalho também permitiu investigar se esses genótipos podem apresentar estacionalidade de produção, auxiliando no planejamento alimentar dos rebanhos. Foram realizadas cinco datas de semeadura (11/05, 07/06, 05/07, 09/08 e 01/09/2007) em Santa Maria, Rio Grande do Sul (RS). Os métodos utilizados para cálculo de Tb foram o da menor variabilidade ou desvio padrão e do desenvolvimento relativo ou equação de regressão. Os valores de Tb, para os genótipos diplóides, variam entre 7,0 e 8,5°C, já os valores para os tetraplóides variam de 9,0 a 10,6°C, dependendo do método de estimativa da Tb. As pastagens de azevém com germoplasma diplóide não possuem risco de estacionalidade de produção, mas os tetraplóides, com destaque para o Avance, poderão ter seu crescimento e desenvolvimento reduzidos nos meses de junho a agosto, em Santa Maria, em função das temperaturas mínimas do ar.

The objective of this study was to estimate lower base temperature Tb of three diploid (Comum, Fepagro São Gabriel, and LE 284 and two tetraploid (Avance and INIA Titán) ryegrass genotypes. With the estimated Tb, it was also possible to investigate if these genotypes may have seasonal production, which helps in programming herds feeding schedules. Five sowing dates (11/05, 07/06, 05/07, 09/08 e 01/09/2007) were performed in Santa Maria, RS, Brazil. Two methods were used to estimate Tb: least deviation method and relative development method. Tb values varied from 7.0 to 8.5°C for diploid genotypes and from 9.0 to 10.6°C for tetraploid genotypes, depending upon the method. Diploid ryegrass germoplasm have no risk of seasonal decrease in forage production, whereas tetraploids, mainly Avance, may have their growth and development decreased from June to August in Santa Maria because of minimum air temperature.

Previsões meteorológicas do Modelo Eta para subsidiar o uso de modelos de previsão agrícola no Centro-Sul do Brasil / Eta model forecasts as input to crop models for the Mid-Southern region of Brazil

Este trabalho tem por objetivo avaliar a precipitação pluvial e as temperaturas máximas e mínimas previstas pelo Modelo Eta para até 120 dias de previsão em 24 localidades distribuídas na região Centro-Sul do Brasil. A avaliação se baseia na comparação de séries históricas de chuva e temperaturas de 1997 a 2002, com as previsões de 30, 60 e 120 dias de antecedência do Modelo Eta para as 24 localidades. Foram utilizados valores de média, mediana e desvio padrão nesta avaliação. Os resultados indicam que estas previsões geralmente subestimam as chuvas e a amplitude térmica nestas localidades. Os menores erros de precipitação pluvial se localizam mais destacadamente em Itumbiara e Rio Verde, enquanto que os maiores, em Porangatu e Manduri. Por outro lado, os menores erros de temperatura máxima se localizam destacadamente em Brasília, Manduri e Piracicaba, enquanto que os maiores ocorrem em Barreiras e Porangatu. Apesar de o modelo apresentar erros sistemáticos nas previsões de temperaturas, estes erros podem ser removidos para que os valores corrigidos possam ser introduzidos nos modelos de culturas.

The objective of this study was to evaluate the 120-day precipitation and maximum and minimum temperature forecasts by Eta Model over 24 locations around the Mid-Southern of Brazil. The evaluation was based on comparing observed time series of precipitation and temperatures from 1997 to 2002 to 30, 60 and 120-day forecasts of Eta Model over these 24 locations. Mean, median and standard deviation were used in the evaluation. The results show that these forecasts generally underestimate rain and temperature range. The smallest precipitation errors occurred in Itumbiara and Rio Verde, whereas the largest errors occurred in Porangatu and Manduri. The smallest maximum temperature errors occurred in Brasília, Manduri and Piracicaba whereas the largest errors in Barreiras and Porangatu. Despite the systematic errors exhibited by the precipitation and temperature forecasts, these errors can be removed and the corrected values input into the crop models.

Regiões homogêneas e tamanho de amostra para atributos do clima no Estado de São Paulo, Brasil / Homogeneous regions and sample size for attributes of the climate in São Paulo State, Brazil

Os objetivos deste trabalho foram demarcar regiões homogêneas e estimar o número de anos de avaliações para as variáveis insolação, radiação solar global e radiação fotossinteticamente ativa para o Estado de São Paulo. Utilizaram-se dados da média mensal de insolação, radiação solar e radiação fotossinteticamente ativa de 18 locais do Estado de São Paulo. A homogeneidade das variâncias entre os meses do ano para os 18 locais (variabilidade temporal) e a homogeneidade das variâncias entre os locais em cada mês (variabilidade espacial) foram testadas pelo teste de homogeneidade de Bartlett. Estimou-se o tamanho de amostra para cada local durante o ano. Como resultados há variabilidade temporal e espacial para as estimativas de insolação, radiação solar e radiação fotossinteticamente ativa para os 18 municípios avaliados. Além disso, a variabilidade do tamanho de amostra para a insolação, radiação solar e radiação fotossinteticamente ativa depende do local e da época do ano no Estado de São Paulo.

The purpose of this study was to separate homogeneous regions and to estimate the numbers of years necessary to evaluate the variables: sunshine, global solar radiation and photossintetically active radiation in Sao Paulo State. Monthly data of sunshine, solar radiation and photossintetically active radiation for 18 places in Sao Paulo State were used in the analysis. The homogeneity of the variances among the months for the 18 places (seasonal variability) and the homogeneity of variances among places in each month (spatial variability) were tested by the test of homogeneity of Bartlett. In addition, the sample size for each place was calculated during the year. The results show the existence of seasonal and spatial variability in the estimates of sunshine, solar radiation and photossintetically active radiation for the 18 cities evaluated in Sao Paulo State. Moreover, the variability of the sample size for sunshine, solar radiation and photossintetically active radiation depend on the site and season of the year in Sao Paulo State.

The 15N isotope to evaluate fertilizer nitrogen absorption efficiency by the coffee plant.

The use of the 15N label for agronomic research involving nitrogen (N) cycling and the fate of fertilizer-N is well established, however, in the case of long term experimentation with perennial crops like citrus, coffee and rubber tree, there are still shortcomings mainly due to large plant size, sampling procedures, detection levels and interferences on the system. This report tries to contribute methodologically to the design and development of 15N labeled fertilizer experiments, using as an example a coffee crop fertilized with 15N labeled ammonium sulfate, which was followed for two years. The N of the plant derived from the fertilizer was studied in the different parts of the coffee plant in order to evaluate its distribution within the plant and the agronomic efficiency of the fertilizer application practice. An enrichment of the fertilizer-N of the order of 2% 15N abundance was sufficient to study N absorption rates and to establish fertilizer-N balances after one and two years of coffee cropping. The main source of errors in the estimated values lies in the inherent variability among field replicates and not in the measurements of N contents and 15N enrichments of plant material by mass-spectrometry.

The 15N isotope to evaluate fertilizer nitrogen absorption efficiency by the coffee plant

The use of the 15N label for agronomic research involving nitrogen (N) cycling and the fate of fertilizer-N is well established, however, in the case of long term experimentation with perennial crops like citrus, coffee and rubber tree, there are still shortcomings mainly due to large plant size, sampling procedures, detection levels and interferences on the system. This report tries to contribute methodologically to the design and development of 15N labeled fertilizer experiments, using as an example a coffee crop fertilized with 15N labeled ammonium sulfate, which was followed for two years. The N of the plant derived from the fertilizer was studied in the different parts of the coffee plant in order to evaluate its distribution within the plant and the agronomic efficiency of the fertilizer application practice. An enrichment of the fertilizer-N of the order of 2 percent 15N abundance was sufficient to study N absorption rates and to establish fertilizer-N balances after one and two years of coffee cropping. The main source of errors in the estimated values lies in the inherent variability among field replicates and not in the measurements of N contents and 15N enrichments of plant material by mass-spectrometry.

O uso do traçador 15N em pesquisas agronômicas que envolvem o ciclo do nitrogênio (N) e o destino do N do fertilizante está bem estabelecido, entretanto, para o caso de experimentação com plantas perenes como citrus, café e seringueira, ainda existem limitações devidas ao porte das plantas, à amostragem, aos níveis de detecção e à interferência no sistema. Este estudo procura contribuir metodologicamente no delineamento experimental e no desenvolvimento desse tipo de experimentação, em condições de campo, fazendo uso, por dois anos, do experimento de uma cultura de café adubada com fertilizante marcado com 15N. O N da planta derivado do fertilizante foi estudado nas diferentes partes da planta de café para determinar sua distribuição dentro dela e a eficiência agronômica da prática de adubação. Um enriquecimento do N do fertilizante da ordem de 2 por cento em abundância de 15N foi suficiente para estudar taxas de absorção de N e estabelecer balanços do N do fertilizante depois de um e dois anos de cultivo. A principal fonte de erros dos valores estimados está na variabilidade agronômica das repetições e não na precisão das medidas de conteúdo de N e de enriquecimento em 15N por espectrometria de massa.

Equações de estimativa da fitomassa da parte aérea da alface / Equations to estimate shoot phytomass of lettuce

O objetivo deste trabalho foi identificar equações de regressão que expressem o acúmulo de fitomassa a partir de variáveis meteorológicas e índices de crescimento da cultura, com a finalidade de avaliar o crescimento da alface cultivada em estufa plástica e a campo, em diferentes épocas do ano. No estudo, foi utilizada a cultivar "Regina". As variáveis meteorológicas determinadas foram a temperatura, a umidade relativa média do ar e a radiação solar fotossinteticamente ativa acumulada. Os índices de crescimento da alface utilizados foram a fitomassa seca e o índice de área foliar. Independentemente da época do ano, os resultados evidenciaram que as equações de regressão simples, utilizando as variáveis índice de área foliar ou radiação solar fotossinteticamente ativa acumulada, apresentaram melhor desempenho na estimativa da fitomassa (R²>0,88) nos dois ambientes. As equações de regressão múltipla, apesar de englobarem mais variáveis, apresentaram pequeno acréscimo no valor do R².

The aim of this paper was to propose regression equations that express the dry matter accumulation in lettuce using meteorological parameters and growth index, to modeling the lettuce growth in greenhouse and in the field, in different growth season. The "Regina" cultivar was utilized. The meteorological variables determined were air temperature and relative humidity average and accumulated photosynthetically active radiation. The growth indexes of lettuce used were dry mass and leaf area index. Independent of the growth season, the results shown that linear regressions utilizing variables leaf area index and accumulated photosynthetically active radiation provided a good estimate of the dry mass (R²>0.88) for both seasons. The multiple regressions need more data, but shown a little increase in R² value.

Forragem hidropônica de milheto: produção e qualidade nutricional em diferentes densidades de semeadura e idades de colheita / Hydroponic millet forage: production and naurishing quality in different sowing densities and harvest ages

Com objetivo de avaliar a produtividade e a qualidade nutricional da forragem hidropônica de milheto, realizou-se um experimento no Departamento de Fitotecnia da Universidade Federal de Santa Maria (UFSM) - RS, identificando a densidade adequada de sementes e a idade ideal de colheita. Adotou-se o delineamento experimental inteiramente casualizado; os tratamentos foram distribuídos em esquema fatorial 4x2, constituídos por quatro densidades de semeadura (0,5, 1,0, 1,5 e 2,0kg m-2) e duas colheitas (10 e 20 dias). Não foi observada significância à interação densidade x idade de colheita para nenhuma das variáveis analisadas. A estatura, a fitomassa seca, a hemicelulose e a lignina não foram influenciadas pela densidade de semeadura. O aumento da densidade de semeadura promoveu incremento na fitomassa fresca e no teor de proteína bruta e redução nos teores de fibra em detergente neutro e ácido e em celulose. A colheita aos 10 dias permitiu maiores valores de fitomassa fresca e seca, de hemicelulose, de celulose e menores valores de fibra em detergente neutro e ácido, e de lignina. Em relação à proteína bruta, não foi observada diferença significativa para as colheitas aos 10 e 20 dias. Pode-se sugerir o cultivo da forragem hidropônica de milheto, com densidade de semeadura de 2kg m-2, e colheita aos 10 dias, para se obter boa produção com qualidade nutricional.