Avaliação emergética da cultura do algodão colorido irrigado com água residuária em ambiente semiárido.

Abstract

In the arid semi-arid regions of the world, the water become a limited factor to the urban, agricultural and industrial development. In this way the water reuse is indicated as an economical alternative for the human activity in aid of the environment. Therefore this work has as objective to show a proposal with reuse of urban residual water originating from the municipality of Campina Grande/PB - Brazil in the production of Colorful cotton, BRS-200 variety, being evaluated through the Emergy Methodology proposed by Odum, where the social-economical and environmental factors are examined and identified to alleviate the impact of residual water in the environment represented by renewing the product. The research was developed in the field, in Paraíba Water and Sewer Company Effluent Treatment Station - STE, being and experimental area of 4.200m2, 350 m away from the Stabilization Pond (STE Catingueira) with a level difference of 5m, na incline of 1,5%, the soil of the area is a Neosoil, with a medium Franc-day-sandy texture, with a natural pasture, previously cultivated with cotton, corn and other varieties. The water used on the research was originating from both the local supply net and Treatment Station (STE-Catingueira). According to the research we could notice that the residual water originating from home sewers realizes a great contribution to the environment due to the high number of organic material. According to the Emergetic Analysis the basic differences between the Supply Water and the Residual one are: the supply water didn't present a good production rate per hectare, being 500kg/ha with a Renewal rate of only 22%R on an average that goes to 70%R; the residual water presented a production of 1.500kg/ha, regarding a renewal rate of 37,00. For the colorful cotton irrigated with supply water and sold t US$ 0,46/kg, it presented only US$ 200/ha presenting the energy product at 3,52E+03J(ha/year) and an emergy in dollars of 1.72E + 13sej/(ha/year). The cotton irrigated with residual water solda the same price of US$ 0,46/kg presented rate of US$600 (ha/year) what results in a product energy of 2,78E+10J/(ha/year) representing more than twice of the production on the same area irrigated with supply water. We can notice that the sanitary sewers can cantain the nutrients necessary to full fil the plants nutritional demand. However, they will not necessianly be available in the ways and moment demanded. For instance, the nitrogen forms more easily assimilated are the nitrate (N03", -N) and the amonio (NH+4,-N), but the sewers effluents treated can contain considerable tenors of ammonia (NH+3, -N) and organic nitrogen. Besides the demands of water and nutrients don't happen in parallel what requires an apropriate equation. Therefore the Colorful Cotton is ecologically correct, non pullutant with an aggregated valve for the producer and has a strong appeal on the international market. It is also an excellent alternative for home agriculture in the semiarid region of Brazilian northeast. Besides being adapted to the modern spinning, the colorful cotton plantations reduce the production costs for the textile industry and the introduction of chemical and toxic effluents because they aroid the use of colorings.