Monitoramento do uso da terra e dos níveis de nutrientes do solo no Sistema Integrado de Produção Agroecológica utilizando geoprocessamento

Abstract

Agroecological production systems are more complex than conventional ones, since a series of crops follow in sequence or are intercropped to achieve high diversity and maximize soil nutrient recycling. The full understanding of these systems require systemic analyses and therefore, adequate tools. To understand soil fertility evolution, heterogeneity should also be considered. This thesis was performed at Integrated Agroecological Production System, located at Seropédica, Rio de Janeiro, an area that has been organically managed for 14 years. The first chapter consisted of studying land use from 2003 to 2005. Each land unit use was annotated every three months to generate 12 maps. The information gathered was processed to generate three maps: (i) cultivated species richness; (ii) fallow intensity and (iii) green manure use. High cultivated species richness was observed. In some land units up to 40 plant species were recorded. However, this diversity was not uniformly distributed throughout the terrain. A high intensity of land use, mostly with annuals was also observed in a large part of the area. In most cases, fallow periods were up to 3 months in 3 years. The use of legumes was less frequent on the land units used for annual crops. They were not uniformly distributed throughout the terrain. The objectives of the second chapter were: (i) to generate maps of spatial distribution of soil nutrients (Ca++, Mg++ K++ and P), pH and organic matter; at two soil depths 0-20 and 20-40 cm, in 2004 and 2005 (ii) evaluate the difference of those soil attributes in two years (iii) evaluate the difference of soil fertility between the layers of 20-40 cm and 0-20 cm, (iv) generate two maps of fertility potential , one for each year, for the 0-20 cm layer; (v) to combine maps of all attributes in order to generate maps of potential of gain/loss of nutrients . In general, soil nutrient levels were high and very high, indicating that the 14 years of organic management has built up soil fertility. There was a trend of decreasing soil fertility from 2004 to 2005. The area with higher loss potential coincided with a high intensively used portion of the system. However, on the area used as a control, losses also occurred, in lower intensity. From all nutrients studied, phosphorus was the most spatially and temporally variable.