Alterações químicas e biológicas do solo e desenvolvimento de plantas decorrentes da adição de lodo da indústria de laticínios

Abstract

The dairy industry produces residues such sludge, in wastewater treatment. These materials, according to the type of disposal, can cause environmental impacts or, when applied to the soil, improve its properties and represent an economical and beneficial way of disposal. Sludge can also show a residual effect on successive crops and thus reduce costs in agricultural production. Three studies were carried out in order to evaluate changes in some chemical and microbiological attributes of a Albaqualf (Planosol), and in plants growth after application of sludge from the dairy industry. The first study evaluated the soil pH changes after application of increasing doses of sludge from the dairy industry. The incubation experiment was conducted out for 51 days, with the application of the dollowinf doses: 1- 0 g; 2- 8.19 g; 3- 16.38 g; 4- 32.76 g; 5- 49.14 g and 6- 65.52 g of sludge in 500 g of soil. It was concluded that the dairy sludge does not have potential to correct soil acidity to raise and maintain the pH at an ideal value, between 6 and 7. The second study determined the effects of the application of dairy sludge, on soil chemical and microbiological attributes, and on corn plants development. The experiment was conducted in a greenhouse, in polyethylene pots, with doses of: 1.65; 3.3; 4.95; 6.60 and 8.25 g kg-1 . Dairy sludge increased the organic carbon, the levels of phosphorus, potassium and mineral nitrogen in soil. In addition favoring increase dry matter of plants, it stimulated the activity of soil microorganisms. The third study evaluated the residual effect of the application of dairy sludge on the chemical and microbiological soil attributes, and on the development of black oats. The experiment was carried out in a greenhouse and the black oats were sown in pots previously grown with corn. The results indicate a residual effect of the application of dairy sludge, which favored the availability of nutrients to soil, the absorption by plants and the activity of soil microorganisms. The dose of 6.60 g kg-1 provided an accumulation of dry mass equivalent to NPK treatment.