Francisco das Chagas Oliveira

Soil organic carbon and biological indicators in an Acrisol under tillage systems and organic management in north-eastern Brazil.

No-tillage and organic farming are important strategies to improve soil quality. This study aimed to quantify the effects of the tillage systems and organic management on total organic carbon (TOC), labile C (CL), and biological indicators in an Acrisol in north-eastern Brazil. Five systems were studied: NV, native vegetation; NT/ORG, no-tillage plus organic fertiliser; NT/CHE, no-tillage plus chemical fertiliser; NT/CHE/ORG, no-tillage plus organic and chemical fertiliser; CT/CHE, conventional tillage plus chemical fertiliser. Soil samples were collected in the 0–0.10 and 0.10–0.20 m depths. TOC stocks were higher in NT/CHE/ORG (0–0.10 m, 14.0 Mg/ha; 0.10–0.20 m, 13.0 Mg/ha) and NT/ORG (0–0.10 m, 12.6 Mg/ha; 0.10–0.20 m, 11.6 Mg/ha) than in CT/CHE and NV systems. CL stocks were higher in NT/ORG (3.61 Mg/ha) at 0–0.10 m and in NT/ORG, NT/CHE, and NT/CHE/ORG at 0.10–0.20 m. At 0–0.10 m, microbial biomass C content was higher in the NT/CHE/ORG (190 mg/kg) and NT/ORG (155 mg/kg). Soil microbial respiration rate was similar in all systems. However, qCO2 was higher in the NT/CHE and CT/CHE systems, suggesting a stress in the soil microbial biomass. No-tillage and organic management promoted positive changes in soil organic carbon and soil microbial properties and improved soil quality.

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.

Peasant Innovations and the Search for Sustainability: The Case of Carnaubais Territory in Piauí State, Brazil

This article pursues two aims. The first is to assess the degree of sustainability in peasant agroecosystems through the application of the systemic approach, allowing an integrated understanding of technical, environmental, economic, and social impacts to support the agroecological transition process; the second is to comprehend the basis farmers have and the strategies they use in locally favoring the emergence of the innovations that constitute the object of analysis. The conceptual framework used ia that of the MESMIS method, which is based on a set of system attributes for agroecosystem assessment. Results indicate that innovations made by family farmers favored improvements in essential elements of system sustainability, making possible sustainable land use, assuring an increase in income, and maintenance of family employment and farm structuring. These factors cast light on the relevance of local knowledge as a key factor in policies that promote the sustainability of family systems, and as a basis for an agroecological transition process.This article pursues two aims. The first is to assess the degree of sustainability in peasant agroecosystems through the application of the systemic approach, allowing an integrated understanding of technical, environmental, economic, and social impacts to support the agroecological transition process; the second is to comprehend the basis farmers have and the strategies they use in locally favoring the emergence of the innovations that constitute the object of analysis. The conceptual framework used ia that of the MESMIS method, which is based on a set of system attributes for agroecosystem assessment. Results indicate that innovations made by family farmers favored improvements in essential elements of system sustainability, making possible sustainable land use, assuring an increase in income, and maintenance of family employment and farm structuring. These factors cast light on the relevance of local knowledge as a key factor in policies that promote the sustainability of family systems, and as a basis...

A cultura da manga sob diferentes regimes de profundidades do lençol freático em condições subúmidas

O conhecimento dos criterios agronomicos de drenagem para a cultura da manga e fundamental na elaboracao de sistemas de drenagem para areas com essa cultura e permite antecipar o seu comportamento sob diferentes niveis de drenagem do solo . O trabalho teve por objetivo avaliar as condicoes de aeracao e umidade do perfil de um solo arenoso (areia franca) sob diferentes regimes de profundidades do lencol freatico, para determinacao de criterios de drenagem para a cultura da manga, cultivar Keitt. O experimento seguiu um delineamento inteiramente casualizado, com quatro tratamentos (regimes de profundidades do lencol freatico as distâncias do dreno de 3,5 m; 10,5 m; 17,5 m e sem presenca de lencol freatico) e cinco repeticoes. As profundidades do lencol freatico e os teores de agua no perfil do solo em cada tratamento foram monitorados durante os periodos chuvosos, em tres anos consecutivos (1997-1999). Nao houve diferenca significativa entre as produtividades da cultura nos tratamentos. As diferencas nas profundidades do lencol freatico, nos tratamentos com drenagem, nao foram suficientes para diferenciar o estado da agua no solo nesses tratamentos. O lencol freatico, na profundidade media de 1,0 m, durante os cinco ou seis meses de periodo chuvoso, com recargas temporarias atingindo profundidades proximas da superficie do solo, seguidas de rebaixamento imediato do lencol freatico, nao foi suficiente para afetar o desenvolvimento e a produtividade da manga.