R. G. Tonucci

Silvopasture and Carbon Sequestration with Special Reference to the Brazilian Savanna (Cerrado)

The Brazilian savanna, known as the Cerrado, extending over 200 million ha, is the largest neotropical savanna in the Americas. With its ongoing conversion to intensive agriculture since the 1960s, of which cultivated pastures for beef cattle production is a major form, this unique ecosystem is now considered threatened. Given the recognized role of trees in carbon (C) sequestration and greenhouse gas (GHG) mitigation, the silvopastoral system of tree plantation development on pasture lands is considered to be particularly relevant to this region. For the past two decades, eucalyptus-based silvopastoral systems have been established in the Cerrado region by growing agricultural crops (rice and soybean) in the first 2 years followed by Brachiaria forage and beef-cattle grazing from the third year of plantation establishment. Recent studies in a variety of situations indicate that agroforestry systems store higher amounts of C compared to single species cropping and grazing systems, both aboveground and belowground. The Brazilian savannas that have characteristically low aboveground C reserves hold considerable stocks of soil organic C, probably as a consequence of previous land use, the history of which is unknown. Most of this C is in a biodegradable form and is likely to be lost to the atmosphere when the soil is disturbed during land conversion to agriculture and pasture. Adoption of sustainable land use systems such as silvopasture could reduce this potential hazard. Given the role of the Cerrado in the global C cycle and climatic change, these issues deserve well coordinated investigations.

Uma abordagem para avaliar o potencial de agroecossistemas em prover serviços ambientais

The objective of this work was to present an approach to evaluate soil functions in agroecosystems and their impact on environmental services (ES). An approach with case studies was proposed to assess the relationship between the establishment and management of agroecosystems, in three Brazilian biomes (Atlantic Forest, Cerrado, and Caatinga), and their environmental services provision, considering the specificities of each area. A set of soil parameters that can be used as indicators to monitor changes in the agroecosystem was also proposed. The environmental services types most affected by the establishment and management of the agroecosystems were the supporting and provisioning services, showing the potential of agricultural management in providing multiple services, besides food, fiber, and energy. “No fire use” and “agricultural consortium” were the criteria for the establishment and management of agroecosystems with greater potential to increase environmental services provision, whereas biomass stock in soil and litter was the most appropriate soil parameter to be used as an indicator to monitor the impact of agroecosystems in environmental services provision.

Níveis críticos para atributos do solo pela distribuição normal reduzida em culturas anuais de subsistência

This study aimed to propose critical levels for soil chemical properties using the reduced normal distribution in areas of family subsistence farming under maize and cowpea crops in the Brazilian semiarid. Soil samples were collected on family farms in the region of Inhamuns-Crateus. To obtain the critical levels the reduced normal distribution was used which uses the productivity data and the relationship between productivity and soil chemical attributes and assigning the critical level for 90% of the maximum. Critical levels obtained for areas cultivated with maize and cowpea in the semiarid region are: OM (g kg-1): 7.3 and 7.5; pH: 6.6 and 6.5; P (mg dm-3): 8.6 and 8.2; K (mmolc dm-3): 2.8 and 2.7; Ca (mmolc dm-3): 33.3 and 22.4; Mg (mmolc dm-3): 11.2 and 9.9; and base saturation (%): 73 and 71, respectively. The critical level for reduced normal distribution can be used to obtain critical levels for soil chemical properties. The attributes most frequently for negative index over estimated critical level (NCRIz) are Ca > V > pH > Mg > K = OM > P and V > pH > P > OM > Mg > K > Ca areas for corn and cowpea, respectively.