Efeito da época, do mulching e do cultivo de grãos na semeadura direta para restauração ecológica de florestas na Encosta da Serra do Sudeste, Rio Grande do Sul

Abstract

The search for ways to restore forests, especially on family farms in a sustainable and productive manner, is the main driver of this study. Thus, the objective was to study the best time to carry out direct sowing, also evaluating the use of mulching and assessing the feasibility of conducting direct sowing concurrently with grain production. For this, an experiment was carried out, with 4 completely randomized blocks and three treatments, being: time of year (summer and winter), mulching (with and without mulching) and agricultural crops (with and without agricultural crops). Each treatment had 20 plots of 1m (5 in each block), where 12 forest species were sown, among shrubs, trees and tree-like, with 10 seeds of each species being deposited in the plot. The forest species were selected according to the availability of seeds on the market, in addition to their potential use in agroforestry systems in the context of family farming. Emergence, survival and establishment had better results in summer and in the treatment with mulching. The emergence rate in the summer was 16.47% (±1.18%), survival was 29.36% (±3.88%) and establishment was 7.12% (±4.44%). In winter, the emergence rate was 9.32% (±0.97%), survival was 4.94% (±2.13%) and establishment was 1.87%(±1.68%). After twelve months of sowing, in the summer 316 established themselves in 80 linear meters, obtaining between 3.05 and 5.05 individuals per linear meter in different treatments. Extrapolating these values to a hectare, we would have between 10156.5 and 16816.5 individuals/ha, surpassing the plantings of seedlings in total area. In winter, 29 individuals established themselves in 80 linear meters, obtaining between 0.8 and 0.25 individuals per linear meter in different treatments, values that would reach between 660 and 2640 individuals/ha. The treatment with mulching proved superior when compared to without mulching, proving that its use is indicated for the direct sowing technique. Agricultural crops did not show significant differences for the survival and establishment of tree species, a result that brings the possibility of restoring agricultural areas and producing food concurrently in agroforestry systems. In winter, Pioneer plants showed higher emergence rates compared to Secondary plants. In summer, there was a significant difference only for secondary plants in the treatment Without crops and Without mulching, which presented the lowest averages. In summer, the survival and establishment of Secondary plants exceeded the rates of Pioneer plants. In winter, Secondary plants in the treatment With crops + mulching achieved the highest averages of survival and establishment. In winter the height and diameter of the Pioneer plants exceeded the Secondary ones, and in summer there was no significant difference between the groups.