ResumoMétodos de fácil execução, rápidos e não destrutivos, que possibilitem estimar a área foliar com precisão, são importantes para avaliar o crescimento das plantas nas condições de campo. Objetivou-se no presente trabalho, ajustar equações para estimar a área do limbo foliar e a área das folhas do girassol, em função das medidas lineares do limbo e do número de folhas por planta, incluindo a verificação da possibilidade de modelos comuns para as cultivares BR-122 e M-734. Seis plantas de cada cultivar nos estádios de início de florescimento e de florescimento pleno foram coletadas. As áreas dos limbos foliares foram determinadas por método direto. Foram medidos o comprimento ao longo da nervura principal e a largura de forma perpendicular à inserção do limbo no pecíolo. Foram ajustados os modelos linear, quadrático, cúbico, exponencial e potencial. Os modelos potenciais Ŷ i = 1,6329X i 1,7164 e Ŷ i = 0,5405X i 1,0212 com a utilização, respectivamente, das medidas da largura e do produto largura e comprimento são os mais adequados para estimar a área do limbo foliar do girassol. O modelo Ŷ i = 5,1014X i 2,4383 permite estimar com precisão a área foliar total do girassol em função do número de folhas por planta. A precisão das equações ajustadas para as estimativas da área do limbo foliar ou de folhas por planta não é reduzida quando se ajustam modelos comuns às cultivares BR-122 e M-734.Palavras-chave: Helianthus annuus L., crescimento de planta, alometria.Estimates of sunflower leaf area by a non-destructive method Abstract Simple, rapid, and non-destructive methods that help to estimate leaf area accurately are very important to assess plant growth under field conditions. The objective of this study was to adjust equations to estimate the area of a single sunflower leaf and also the area of total leaves per plant as a function of linear measurements of them. It was also verified the possibility of using common models for the sunflower cultivars BR-122 and M-734. Six plants of each cultivar in the early stage of flowering and full flowering were harvested. The area of each leaf was determined by the direct method. The length along the midrib and the width perpendicular to leaf insertion in the petiole were determined. Linear, quadratic, cubic, exponential, and potential models were adjusted. The potential models Ŷ i = 1.6329X i 1,7164 and Ŷ i = 0.5405X i 1,0212 using the width measurements and width x length, respectively, were the most adequate to estimate the leaf area. The model Ŷ i = 5.1014X i 2,4383 allowed to precisely estimate the total leaf area according to the number of leaves per plant. The accuracy of the adjusted equations to estimate each leaf are and total leaves area was not reduced when common models were adjusted to the two cultivars used.Key words: Helianthus annuus L., plant growth, allometry.O girassol (Helianthus annuus L.) é uma planta caracterizada por sua versatilidade industrial e adaptabilidade climática. Considerada uma das principais oleaginosas do mundo, responde por aproximadam...

-The objective of this work was to evaluate the agronomic performance of elite-strains of cowpea cultivars under the conditions of the north of Minas Gerais (MG), Brazil. Fifteen elite-strains and five erect and semi-erect cultivars of cowpea were evaluated in the 2014 and 2015 summer-fall crop seasons in Janaúba MG. A randomized block experimental design was used with four replications. Plant size, lodging and value of cultivation, pod length and grain yield were evaluated. The data of the two crops were subjected to individual and joint analysis of variance. The genotype-crop interactions significantly affected all studied variables. The strains MNC04-792F-146 and MNC04-792F-144 stood out as the most productive genotypes in both crops. The cultivars BRS Itaim and BRS Novaera presented adequate size and lodging characteristics for cultivation, and values of cultivation that meet commercial standards, thus representing good alternatives for the genotypes cultivated in the north of Minas Gerais.Keywords: Vigna unguiculata. Value of cultivation. Yield. PERFORMANCE AGRONÔMICA DE GENÓTIPOS DE FEIJÃO-CAUPI ERETOS E SEMIERETOS NO NORTE DE MINAS GERAIS

The objective was to identify the species and quantify the importance value index of weeds in the cultivation of arabica coffee in two irrigation systems, at different times of the year, in the northern region of Minas Gerais. A phytosociological survey was carried out in each season of the year (spring, summer, autumn and winter) in an area cultivated with the species Coffea arabica, subjected to two irrigation systems (sprinkling and dripping). The coffee crop was implanted at a spacing of 3.5 m between rows and 0.7 meters between plants. The collection of weeds was performed using the standard method of the square inventory, which was launched between the lines of the crop. The identification of the species was carried out, the number of individuals was quantified, the dry mass, frequency, density, abundance, importance value index and coverage, and the similarity index. 33 weed species were identified, being the species with the highest IVI Euphorbia hirta, Brachiaria plantaginea, Digitaria horizontalis, Cyperus rotundus and Amaranthus spp. It was observed a higher occurrence of weeds from the monocot group in the sprinkler irrigation system while in the drip there were predominance of dicot plants.

Introdução: O levantamento dos atributos físicos do solo e do relevo é primordial para o monitoramento das modificações ambientais decorrentes das ações antrópicas. Objetivos: Objetivou-se caracterizar os atributos físicos do solo em uma microbacia do rio Pandeiros, Várzea Bonita, distrito de Januária-MG, determinando a variabilidade espacial das estimativas desses atributos e analisar de forma multivariada quais atributos refletem a variância na área considerada. Métodos: Foram amostrados vinte e cinco pontos georreferenciados de solo, sendo caracterizados os atributos físicos e o relevo. Resultados: O mapeamento do solo na microbacia em estudo indicou dependência espacial para a maioria dos atributos físicos do solo, com exceção da condutividade hidráulica do solo saturado. A análise multivariada dos atributos físicos do solo baseada nos componentes principais explicou 95,72% da variabilidade dos dados na microbacia, possibilitando delimitar os atributos mais sensíveis no monitoramento das modificações ocorridas no solo. Conclusão: Os teores de areia média, areia fina e areia muito fina são os atributos que mais refletem as modificações ocorridas no solo.

The objective of this work was to evaluate the agronomic performance and water use efficiency of crop rotations under conventional system (CTS) and no-tillage system (NTS) through two experiments conducted in the Semiarid region of the northern state of Minas Gerais, Brazil. Experiment 1 consisted of a grain corn-common bean rotation, and experiment 2 consisted of a sorghum-sweet corn rotation. The treatments, in both experiments, consisted of two tillage systems (CTS and NTS) arranged in strip-plots, in two crop years, with ten replications. Yield and production components of all crops and water use efficiency (WUE) of crops grown in the autumn-winter seasons were evaluated within each crop rotation. The data obtained were subjected to analysis of variance and, when significant, the means were subjected to the F test at 5% significance level. The results obtained showed that the NTS increases corn yield in 21.45% in the grain corn-common bean rotation; however, the common bean yield present no difference between tillage systems. NTS increases the sorghum fresh and dry matter yields in 39.65% and 84.26%, respectively, in the sorghum- sweet corn rotation, and the sweet corn total and commercial ear yield in 11.99% and 21.80%, respectively. The NTS increases the WUE of crops grown in the autumn-winter season, in both crop rotations.