Impactos da dinâmica do estoque de carbono e nitrogênio no solo em área cultivada com cana-de-açúcar.

Abstract

The progress of research contributes to the improvement of management techniques adopted and, consequently, to a cultivation system with lower environmental impact and greater sustainability. Accordingly, this research aims to evaluate the impact of the stock of the temporal dynamics of carbon and nitrogen in a Ultisol cohesive with sugarcane cultivation with previous straw burning for harvesting on soil properties. The experimental area is located in the North Forest Zone in Goiana-PE municipality. Soil samples were performed in area chronosequence cultivated with sugarcane, it is composed of eight plots with different deployment times: zero time (Mata, strictly speaking), one, two, three, four, five, six and seven years. 5 samples per field were performed in seven 0-5, 5-10, 10-20, 20-40, 40-60, 60-80 and 80-100 cm. To characterize the quality of soil physical properties were analyzed (particle size and density), water (hydraulic conductivity, moisture, macro and microporosity) and chemical (stock of carbon and nitrogen, and fertility). The attributes in the study were initially analyzed by classical statistics to determine anomalous data and pattern of distribution of knowledge subsequently applied multivariate analysis of hierarchical clustering and principal component, allowing the evaluation of similarities and/or differences of the areas studied in addition to the reduction of dependent variables on the variation of the data. The replacement of forest by agricultural cultivation system of sugarcane with straw burning for manual harvesting promoted decrease of about 50% in organic carbon stocks and total soil nitrogen. The largest carbon and nitrogen stocks in all evaluated layers were statistically pronounced in forest area. The use of multivariate techniques proved effective in environments of distinction about different times of deployment of crop cycles of sugarcane in chronosequence, grouping the different times of management as to the physical water and soil chemical attributes, which refers the importance of long-term soil sustainability studies. From the sugarcane plant cultivation cycle was found to change as water physical and chemical attributes of the soil, especially in the surface layers 0-40 cm. After seven years of evaluation of crops observed that soil characteristics tended gradually to return the initial conditions of forest through lack of mobilization and soil disturbance as can be seen in soca 5th and 4th year, mainly in layers 60-100 cm deep, to the chemical and physical water, respectively.