Efeito do calcário em atributos biológicos do solo

Abstract

The soil is a complex system composed by live organisms, organic matter, gases, water and minerals parts that interact. In this sense, the soil organisms, besides inhabitants, are part of its composition. In the soil, the agricultural activity normally begin in a natural area, with several species of plants and animals living in equilibrium, may pass to a reduction of biodiversity, in function of agricultural practices. The present study was carried out in phases, aiming to evaluate and characterize the faunal composition, the population of nitrifying bacteria, and to develop a protocol to extract earthworms DNA. The faunal composition and nitrifying bacteria, population was done in an experiment with five years of no-till with the following treatments: a) witness (without lime); b) amount indicated by SMP method to pH 6.0 (100%), incorporated to soil in 20 cm depth; c) amount indicated by SMP method to pH 6.0 (100%), distributed in soil surface; d) half of the amount indicated by SMP method to pH 6.0 (50%), distributed in soil surface; and e) one quart of the amount indicated by SMP method to pH 6.0 (25%), distributed in soil surface. To evaluate the population of soil meso and macrofauna were collected samples in July (winter) and December (summer) of 2001. For epiedafic meso and macro organisms were installed traps for capture, and for euedafic macro organisms, were collected soil monoliths. The samples collected individually were placed in plastic bags, packed in thermo boxes and taken to Soil Biology Laboratory of UFSM Soils Department. Later, were performed separation, counting and classification of taxonomic groups in level of classes and order of the organisms? Were utilized the Shanon Diversity Index (H) to evaluate the population among the treatments and theTukey test (P=0.05) to compare the means of population in the different doses and mode of lime application. The doses and mode of lime application in no-till after 5 years were not a significant factor to affect the abundance and richness of soil fauna. The most representative population of organisms was Collembola. The quantitative determination of bacteria nitrifying population was performed with seeding of dispersed soil over a layer of silica gel and later addition of a mix composed of lime, alkaline silicates and an acid mixture, that became neutral forming a second layer of silica gel that contains the nutrients specific to the growth of the bacteria group studied. The experiment was performed in triplicates with 25 mg of soil samples per plaque. After 10 days of incubation in 28-30oC were done observations and counting of the colonies developed in each plaque, presuming that each bacteria formed one colony. The counting was done every 5 days for a period of 60 days. The application of 100% lime, incorporated or on soil surface, and 50% of lime on soil surface did not were significantly different in the number of colonies of nitrifying bacteria. The pH under 4.3 in the treatments witness and 25% of lime on soil surface affected negatively the bacteria population in depths 0-5 and 5-10 cm. To develop a protocol to extract DNA of earthworms, earthworms were collected in the experiment of doses and mode of lime application in the no-till system, in the experimental area of UFSM Soils Department. After visual characterization of identical groups, 10 individuals of each specie of Eisenia foetida and Pheretima spp were placed in alcohol 70% for later characterization after morphological patterns of each specie. Other 10 individuals were open and taken all materials from its interior. Before DNA extraction, the material stayed in sterilized water for 24 hours in refrigerator to eliminate any substances that may be stayed glued to the material. Later, the material was macerated and the DNA extracted. The DNA extracted was visualized in agarose gel 1.2%. The protocol developed was efficient to extract the DNA of Eisenia foetida and Pheretima spp.