Atributos Microbiológicos do solo em diferentes Rotações de Culturas sob Sistema Plantio Direto nos Campos Gerais-PR

Abstract

Crop rotation is an essential practice for a sustainable agricultural system, since it adds residues and organic matter to the soil, and this process is intensified by the use of cover crops. This organic matter is a source of energy for the microbiota, providing its activation and improving soil fertility. The rotations need to be planned to suit the objectives of the producers, but also aiming at the quality and sustainability of the environment in which it is inserted. There are several soil quality indicators that evaluate the production environment, verifying its conduction at the moment, those related to the soil microbiota have been reported as of great importance and a positive correlation between management changes and soil microbiological indicators. The objective of this work was to evaluate the behavior of soil microbiological indicators linked to the carbon (C) and nitrogen (N) cycle in different crop rotation systems in a no-tillage system (DPT). The experiment was conducted at the Experimental Station of IDR-Paraná in Ponta Grossa-PR since 2017. The experimental design is randomized blocks, where 6 rotations are compared, with different levels of crop diversification, with 4 replications. The treatments had different proposals, each with a sequence of species to meet the proposal, one of them being succession (Rotation I), the most used in the region, considered a witness The other 5 rotations proposed in the research were the Producer Rotation (Rotation II) , Grains (Rotation III), Grains/Phytomass (Rotation IV), Winter Forages (Rotation V), Phytomass Winter (Rotation VI), each one composed of a sequence of different crops in order to meet proposals related to the presence of green manures (including intercropping), increased diversity of productive crops and intercalation of vegetative and cultivated groups in order to obtain data. A sample composed of soil per plot was collected in the 0-0.10 m layer in the summers of the 2018/2019, 2019/ 2020 and 2020/2021. The activity of five soil enzymes (Arylsulfatase, B-Glucosidase, Acid Phosphatase and Fluorescein Diacetate Hydrolase, Urease) was evaluated, and the C and N of microbial biomass, basal soil respiration (RBS), soil microbial quotient and metabolic quotient. The content and stock of total organic C and the labile and non-labile fractions (> and < 53 μm) were also determined, and nitrate and ammonium were quantified, in addition to the elements included in routine soil fertility analyses. The productivity of summer crops was evaluated and the dry mass of all crops in the winter and summer crops was determined. The results were submitted to analysis of variance, applying the F test and when there was significance, the means were compared by Tukey's test at 5% error probability. A multivariate principal components and regression analysis of the 3-year evaluation data was also performed. The treatments with greater diversity of cover species showed higher values of activity of the enzymes arylsultase, fluorescein diacetate hydrolase, B-Glucosidase, Acid Phosphatase and in the amount of C and N in the microbial biomass and in the RBS in the 3 years evaluated. Over the years of analysis, it was possible to verify that most of the indicators maintained their values, but the activity of arylsulfatase, diacetate hydrolase, B-glucosidase, acid phosphatase, and the amount of C and N in the microbial biomass, RBS, ammonium, nitrate and total organic C had an increase. Thus, it is concluded that crop rotations with the use

of green manures induce an increase in soil quality, especially when legumes are included.