Banca de DEFESA: DANILO DA SILVA MARINHO

DEVELOPMENT OF FORAGE SPECIES IN RESPONSE TO DIFFERENT LEVELS OF SHADE, IN THE FOREST AREA OF RONDONIENSE

Sustainable agriculture; Agrosilvopastoral; Sustainable development; Integrated Agricultural Production Systems.

The objective of this research was to evaluate the effect of different levels of artificial shading on the morphological development of six forage species used in pastures in the northern region, in order to observe their aptitude for cultivation in integrated agricultural production systems. The study was conducted on a rural property located in the municipality of Rolim de Moura – RO. The forage grasses evaluated were Brachiaria brizantha cv. marandu, piatã and xaraés, Panicum maximum cv. mombaça and zuri, and Brachiaria ruziziensis cv. ruziziensis.

The plants were subjected to development in full sun (control) and different levels of artificial shading, these being 70%, 50% and 30% of solar restriction. Four cuts of the aerial part were made every 40 days, and the wet and dry mass of the aerial parts and roots, plant height, stem diameter, leaf width and length, tiller density and leaf:stem ratio were evaluated, with assessments involving the roots being carried out only after the last cut of the aerial part. The design was in randomized blocks, with four treatments, six forage cultivars and four replications per cultivar (4x6x4), totaling 96 plots.

An analysis of variance and comparison of treatment means were performed using the Tukey test at 5% probability (P = 0.05) for each of the cultivars evaluated under different levels of shading. It was observed that the cultivars evaluated showed an inversely proportional correlation between the variables height and leaf length with the reduction in illuminance. Also observed for the variables tiller density, stem diameter and root dry mass, where the reduction in illuminance also reduced the means of these variables. The shading levels used in this research did not influence the production of wet mass and dry mass of the aerial part for all forages studied. Considering the dry mass productivity of the evaluated cultivars, all of them could be recommended for cultivation in integrated agricultural production systems.

However, the Mombaça cultivar stands out as the most suitable for shaded environments, as it demonstrated a smaller percentage reduction in root production, in addition to greater growth in height, leaf length and stem diameter compared to Brachiarias when exposed to shade. It is worth highlighting that further studies with the objective of evaluating the bromatological properties and palatability of forage crops subjected to development under restricted sunlight are extremely important to consolidate information about the suitability of forage grasses for cultivation in integrated agricultural production systems.