Manejo mecânico de plantas de cobertura e seus efeitos nas propriedades quimícas do solo e na produtividade da soja em sucessão

Abstract

The present work had as objectives: to evaluate the decomposition of the cultural residues coming from autumn / winter cover plants managed with two equipments, the productivity of the soybean cultivated in succession and; to evaluate changes in soil quality from chemical fractions of organic matter and total organic carbon content in the soil in two periods. The experiment was carried out in randomized blocks in a factorial arrangement (5x2), subdivided in time, with four replications, with five coverages (black oats, forage turnip, consortium of turnip + oats, common vetch and fallow), two managements (roller- knife and plant crusher). The collection times of the litter bags (0, 20, 40, 60, 80 and 110 days after handling-DAM) as well as the soil collection periods (Post-PC and Post-Soy) were the subplots. For the agronomic and productivity components of soybean, the same experimental design and number of repetitions mentioned above were used, in a 5x2 factorial arrangement (five coverages and two managements). The soybean was sown in succession to the cover crops. The factors evaluated in this work were: decomposition of the cover plant phytomass through the litter bags method; components of soybean production and productivity; Total organic carbon content of the humic fractions of the soil organic matter. At 110 DAM, the coverings that showed the greatest decomposition were vetch and fallow (91 and 90%) as well as the shortest half-life-T½ (31 and 33). The plants that most remained with their residues on the soil were black oats and intercropping (35 and 25%). In the first 60 DAM, the shredder provided a loss of phytomass of 40% more than the knife-roll and was also the equipment that presented the lowest T½ (45). The handling with the shredder resulted in greater daily decomposition in the period of 60 days. Decomposition was less with the roll-knife management. When analyzing the height of soybean plants (AP), the highest values of this variable were found in the plots that previously had vetch (69.56 cm), oats (68.9 cm) and fallow (68.07 cm), with vetch also stood out for AIPV (12.62 cm). For NVP and NGP, the soybean grown in the plots that were composed of oats, presented the highest average values (62.00 and 144.00 cm, respectively). The productivity of the soybean crop in succession to the cover crops showed no difference. Variations in the TOC contents, humidified fractions and their relationships were identified in the two evaluation periods, indicating that the cover crops used in the research directly influenced the chemical properties of the soil, in the different layers evaluated, reaffirming the tested hypothesis. In general, considering all the evaluated layers, the Post-PC period was highlighted in terms of TOC values, humidified fractions and their relationships, showing that soon after handling the coverings with the equipment, changes in these variables can already be seen in different layers, thus showing the great capacity that cover species have to influence soil characteristics.