Aspectos técnico, econômico e ambiental do uso de fontes orgânicas de nutrientes, associadas a sistemas de preparo do solo

Abstract

The manures have been used as organic nutrient sources in many soil and climatic conditions, and their effects on technical, economic and environmental aspects are dependent on their characteristics and it can be changed by soil tillage. Many studies have been performed to analyse these aspects, however a few of them have analysed the interactions of these three aspects. The analyse of long-term use of manure can contribute to understand of their impact on the agricultural system. Furthermore, it also can contribute to make decision about their use as fertilizer with aim the rational use. The objectives of this study were to quantify and analyse the technical, economical and environmental aspects of organic nutrient sources, do a combine analyse of these three aspects, and to compare the different nutrient sources. The study was carried out at Epagri Experimental Station of Campos Novos, in a Haplorthox, using a long-term experiment. The treatments were a combination of five tillage systems (no-till, chisel plow, conventional tillage, conventional tillage with crop residues burned, and conventional tillage with crop residues removed from the field) with five nutrient sources (TES = control, no fertilizer; AM = mineral fertilizer according with technical recommendation for each crop; EA = 5 Mg ha-1 of moisture poultry litter; ELB = 60 m3 ha-1 of liquid cattle manure; and ELS = 40 m3 ha-1 of liquid pig manure). A model was used to quantify and analyse the effect of nutrient sources in the technical, economic, and environmental aspects, for each nutrient source within each soil tillage. The model had attributes from soil, plant, economic, as well as personal opinion. The outputs were triangular pictures and theirs areas with 90% confidence limits. The attributes in the technical aspect were soil pH in water, potential acidity at soil pH, available P and K, organic matter, exchangeable Al, Ca and Mg, macroporosity, bulk density, available water content, water stability of aggregates, dry-matter of winter cover crops, and root length and distribution in the soil profile. In the economical aspect, the attributes were variable costs of production, total income, and the cost of the necessity of lime and fertilizers application to improve soil chemical condition after nine years of applying treatments. For the environmental aspect, the attributes were available Cu and Zn, moderately and labile P compounds, diversity index of soil mesofauna, and questioner with technical opinion about nutrient sources and soil tillage impacts. Nutrient sources promoted improvement in the majority of analised aspects, but the effect was variable among tillage systems. Organic sources did not differ in technical aspect after nine years of applying treatments. However, there was difference in the economical aspect, when the EA and ELS sources showed better performance. Regarding to environmental aspect, the ELS had the worst performance. In the combine analysis of the three aspects, the EA and ELS sources had better performance than ELB source. The better overall performance of nutrient sources was found in the conservation tillages, and the worse in the tillage systems with greater soil mobilization and burning or remotion of crop residues.