Atributos de qualidade de solos sob dois diferentes tipos de manejo no município de Ibiúna/SP, Brazil

Agricultural activity has direct consequences on the soil and water quality. Thus, assessing environmental impacts of this vital economic activity, through soil attribute analysis, is essential to the proposal of alternatives. The aim of this study was to analyze soil quality under different land management practices, conventional and organic. The study was carried out in a watershed of the Ibiuna municipality, SP, Brazil, an important supplier of agricultural products for the São Paulo metropolitan area. A hundred samples were collected, 20 in each type of land use: reforested areas, native vegetation, pasture, conventional cultivation and organic cultivation. The soil resistance to penetration, its pH (in water and KO), electrical conductivity, bulk density, particle density, porosity, soil color, soil texture and the percentages of carbon and nitrogen were analyzed. The data were statistically analyzed, searching for significant differences. The results of soil analysis showed great similarity between the organic and conventional culture, with no statistical differences. However, organic cultivation showed greater similarity to the soil of native vegetation in the percentage of carbon and nitrogen in soils compared to conventional culture. Thus, the discussion begins on a topic very little explored so far, and the results obtained should be further studied.

ECONOMIC ANALYSIS of AMAZON RIVER PRAWN FARMING TO THE MARKETS FOR LIVE BAIT and JUVENILES IN PANTANAL, BRAZIL

The implementation of a hypothetical aquaculture facility with hatchery, nursery and grow-out earthen ponds for raising the Amazon River Prawn Macrobrachium amazonicum in the Pantanal was considered. Eight larviculture cycles per year were projected: four to produce post-larvae for stocking in grow-out bait ponds, and four to stock nursery tanks to sell juveniles as seed to grow-out farms, which produce prawns for human consumption. Annual production would be 146,880 dozen bait prawns and 2,938 thousand juveniles. The assumed sale prices were US$ 1.38 per dozen baits and US$ 15.39 per thousand juveniles. The net present value was US$ 555,890.79, internal rate of return was 48% per year, payback period was 2.4 years and benefit-cost ratio was 3.90. The breakeven price to cover total costs per dozen baits was US$ 0.70 and per thousand juveniles was US$ 17.00, indicating that the selling price assumed for juveniles in base scenario is not realistic. Net return was US$ 84,773.80. The results indicate that this activity would be a lucrative and attractive investment in the Pantanal.