RESUMOCrambe (Crambe abyssinica) has a cropping cycle of around 90 days, being suitable as an alternative to the second grain crop planted after soybean is harvested in the Center West region of Brazil. It is necessary to understand the growth and development dynamics of crambe plants in order to allow correct management of the production factors. This study aimed to describe the growth and development parameters of crambe plants under presence or absence of interspecific competition. The experiment was installed in the fall-winter 2011 in an Oxisoil, in completely randomized blocks design with three replications. Treatments comprised crambe plants growing either in presence or absence of interspecific simulated competition, throughout the cropping cycle. Plants were collected for the growth analysis every 15 days from harvest until 75 days after emergence. Growth parameters leaf area (AF), dry mass of stems/culms (MSC), leaves (MSF) and total (MST) dry mass, leaf area index (IAF), absolute (TCA) and relative (TCR) growth rates, net assimilation rate (TAL), specific leaf area (AFE), leaf area duration (DAF), leaf area ratio (RAF) and leaf mass ratio (RMF) were determined for the crop plants, subjected or not to competition, as well as for the simulated competitor. Crambe is a low competitive crop, being the competition more severe until 60-70 days after emergence. Besides, crop performance under field conditions was properly described by the net assimilation rate (TAL), which is also affected by the leaf area duration (DAF) and leaf mass ratio (RMF).
The objective of this work was to evaluate the potential of the stable isotope technique to characterize beef cattle production systems in tropical conditions. For this, carbon and nitrogen stable isotopes were identified in non-defatted and defatted bovine muscles. A total of 45 cattle were evaluated in three production systems: pasture, conventional feedlot, and young beef bull feedlot (n = 15 per system). Samples from the Trapezius cervicis, Longissimus dorsi, and Semitendinosus muscles were collected to determine the isotopic composition of δ13C and δ15N. The isotopic data of the δ13C and δ15N of non-defatted and defatted muscles were subjected to the principal component analysis (PCA) and to the discriminant analysis (DA). The PCA allowed separating the three production systems based on the results obtained for the non-defatted and defatted muscles. A correct global classification rate of 100% and a cross-validation rate of 100% were obtained with the DA. The carbon and nitrogen isotopic ratio of non-defatted and defatted muscles allows for the precise identification of beef cattle production systems in tropical conditions.
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