Sandra Santana de Lima

Atributos químicos e estoques de carbono e nitrogênio em argissolo vermelho-amarelo sob sistemas agroflorestais e agricultura de corte e queima no norte do Piauí

Slash and burn farming practices have caused land degradation in the state of Piaui. This problem has stimulated the adoption of land use sustainable alternatives such as agroforestry systems. This work aimed to evaluate changes in the chemical characteristics and carbon and nitrogen stocks in Acrisol under six (SAF6) and ten year (SAF10) old agroforestry systems, agriculture with a three year (SE3) ecological basis, slash and burning practices (ACQ), and native forest (FN) in the northern state of Piaui. Soil samples, in the dry and humid periods, were collected in the 0-10 cm depth. Chemical soil properties, total organic carbon (TOC) and total nitrogen (TN) were evaluated. SAF10 showed lower Al +3 content (0.02 cmolc dm-3) in relation to the other systems. In the dry season, P content in SAF10 (12.27 mg dm-3) was six to seven times larger than ACQ and FN, respectively. The highest values of TOC and TN were observed, in the dry season, respectively, in the SAF10 (48.54 Mg ha-1 and 4.43 Mg ha-1) and SAF6 (43.30 Mg ha-1 and3.45 Mg ha-1). Agroforestry systems improved soil quality and can be considered conservation strategy for northern Piaui.

Serapilheira e teores de nutrientes em argissolo sob diferentes manejos no norte do Piauí

This work aimed to evaluate litter deposition and quantify contents of N, P, K, Ca and Mg in agroforest systems six (AFS6) and ten (AFS10) years after implantation, in three-year old ecological based systems (ES3), slash-and-burn agriculture (SBA) and native forest (NF), all located in Esperantina, northern region of Piaui, Brazil. Collections were carried out in the wet and dry seasons of 2007. The litter was separated into leaves and branches and weighted to estimate the deposition on the soil. The highest leaf depositions were found in NF (3.8 Mg ha-1), in the dry season, whereas for branches, in the AFS10 (2.2 Mg ha-1), in the wet season. AFS showed the highest nutrient contents in the litter fractions, and, among them the N concentration was higher than the others, in both seasons. The estimate transfer of nutrients by the litter followed the sequence N>Ca>K>P>Mg. The values for litter deposition and contents and input of nutrients in the AFS systems show the contribution of the agroforest management to soil quality and the economic sustainability of the system.

Fauna edáfica sob diferentes níveis de palhada em cultivo de cana-de-açúcar

The organisms that constitute the soil fauna are highly relevant to the litter-soil compartments, because they act in important processes, such as fragmentation of the plant material, decomposition and nutrients cycling. This study aimed to evaluate the invertebrate fauna community in soil cultivated with sugarcane harvested without burning, considering the maintenance of different straw levels on the soil surface. Treatments consisted of different amounts of sugarcane straw: T0% (0 Mg ha -1 ); T ? 25% (2.2 Mg ha -1 ); T ? 50% (5.1 Mg ha -1 ); T ? 75% (7.8 Mg ha -1 ); and T ? 100% (12.0 Mg ha -1 ). Samples were collected in the dry season and late wet season, with “Pitfall” traps. The number of individuals per trap per day during the dry period ranged from 11.1 (T0%) to 14.7 (T ? 25%) and, in the rainy season, from 15.11 (T0%) to 33.15 (T ? 75%). The highest Shannon values were observed during the rainy season, and the lowest values ??for diversity and equitability resulted in a higher incidence of Araneae and Formicidae groups. The amount of straw on soil showed no significant influence on ecological indices and total and average wealth. The harvest time affected the number of individuals, species wealth and Shannon and Pielou’s indices. The maintenance of straw on the soil surface benefitted the soil fauna, concerning the conventional crop management.

LANDFORM CURVATURE AND ITS EFFECT ON THE SPATIAL VARIABILITY OF SOIL ATTRIBUTES, PINHEIRAL-RJ/BR

Understanding the spatial variability of soil chemical and physical attributes is important for improving management practices and soil conservation. In turn, the spatial variability of soil properties results from variation in morphological relief characteristics. Thus, the purpose of this study was to evaluate the influence of landform curvature on the spatial variability of soil chemical and physical attributes in the Mar de Morros region (Pinheiral-Rio de Janeiro State, Brazil). Two adjacent landforms were selected with convex and concave curvature and sampled in a regularly spaced grid of 10 meters. A total of 56 soil samples (0-5 cm depth) from the two landforms were collected and analyzed for physical and chemical attributes. The data were analyzed using descriptive statistics and geostatistics. All chemical attributes showed random patterns of spatial variability in both landforms. The concave landform had higher values of pH and potassium and lower values of aluminum than the convex landform. In contrast, silt content showed spatial dependence in both the concave and convex landforms. Bulk density and clay showed spatial dependence in the convex landform. Bulk density and silt content increased from the shoulder to the footslope of both landforms. The results show that, for this study area, landform curvature has more influence on the spatial dependence of soil physical attributes than of soil chemical properties.