Agricultural Production Systems and Soil Fertility in the Pinhal River Sub-basin

The practice of fertilization carried out wrong, based on empirical guidelines, without knowledge of the soil conditions and needs of nutrients to plants, causing the imbalance in plant nutrition and contamination of the agroecosystem. The aim of this study was to evaluate the conditions of soil fertility in the riparian zone of Pinhal watershed. Soil samples were collected in the both sides of the river. The soil sampled on the riparian zone was classified as Cambisol (57%) and Alfisol (43%). Samples were separated in riparian forest and agriculture, and have been characterized chemically. Agriculture in the sampled area contained pasture, corn, reforestation and tea-grass, in proportions of 49%, 21%, 20% and 10%. The soil of the riparian forest had low P and K. It infers that this area can provide important reservoir of nutrients that can be transported by runoff, in this way they won't reach the river. Soils in pasture are degraded. They presented high acidity and low P and K, which denotes the wrong use of this land by farmers. Agricultural activities that showed concern for contamination of water bodies were corn and tea-grass. Phosphorus index to corn was high (67%) and very high (33%) and to tea-grass 50% was high. Potassium showed very high levels to corn (67%) and to tea-grass (50%). All samples had high levels of Cu and Zn. It can be explained because these soils are naturally rich in micronutrients. The high concentrations of phosphorus and potassium in the corn areas show that those receiving high amounts of fertilizers, jeopardizing the quality of surface and groundwater. This justifies the importance of maintaining the riparian zones.