Modeling carbon assimilation and morphogenesis responses of Mulato II Brachiariagrass under contrasting growth rates and in response to canopy height maintained by continuous stocking

Abstract

In Brazil, although forage production is key management is conducted, in most cases, based on broad, non-specific guidelines, which hinders the competitiveness of the livestock industry. This is result, in part of the low availability of technical and scientific information, especially for newly released forage genotypes, which are adopted by producers without adjustments in grazing management. The objectives of this research are to describe and explain the carbon assimilation and morphogenesis responses of Brachiaria hybrid Convert HD 364 (cv. Mulato II) in response to two growth rates and canopy heights maintained by continuous stocking. An experiment will be conducted in Piracicaba, SP, during two summer grazing seasons. The experimental design is a randomized complete block, with a 3 x 2 factorial arrangement, corresponding to three sward heights (10, 25 and 40 cm) maintained by continuous stocking and two growth rates imposed by two N rates (50 and 250 kg N ha-1 yr-1), with three replications, totaling 18 experimental units. Responses studied include morphogenenic characteristics, development and senescence, biomass production, leaf area index, light interception by sward, leaf angle, forage losses and grazing efficiency, photosynthetic indices, as well as modeling canopy CO2. Data will be analyzed using PROC MIXED of SAS, and treatment means will be compared by student's t-test at the 5% level of probability. It is expected that the results will allow better understanding of the morphological and physiological adaptations of this new grass to management variables.