Indicadores de qualidade do solo sob sistema de produção agrícola convencional em conversão para agroecológico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Microbial and biochemical indicators of soil quality, mainly those related to carbon and nitrogen cycling, are useful to access the effect of soil management and its effects on the sustainability of the agroecosystems. The aim of this work was to access changes occurring in the soil due to the transition from conventional to agroecological agricultural systems, by means of microbial and biochemical indicators of soil quality. The study sites are located on smallholder farms at the southern region of Paraná State, Brazil. Soil samples were taken (0-10 cm) from areas with different times since the adoption of the agroecological system, being cropped with common-bean and maize (1 to 5 years), areas under conventional cropping of soybean, maize and tobacco, in addition to an area under secondary forest, used as reference. Assessments comprised some cultivable functional microbial groups, hyphae length, density of endomycorrhizal spores, ammonification and nitrification rates, C and N microbial biomasses, CO2 evolution, water-dispersed clay, enzyme activities (dehydrogenase, cellulose, amylase, urease, asparaginase, glutaminase, acidic and alkaline phosphatases), and hot-water soluble carbohydrates. In general, the functional microbial groups prevailed in the cropped soils in relation to the forest soil. The microbial C and N biomasses and ammonification rates were higher in the forest soil, the lowest in the tobacco soil and intermediary in the other sites. The nitrification rates were the lowest in the forest and tobacco soils. In general, the soil enzyme activities and hot-water soluble carbohydrates were greater in the forest soil, followed by the common-bean soils under agroecological management for longer time, while the tobacco soil had the lower records. Some variables assessed in the soils under agroecological system showed a tendency towards the soil characteristics under forest, but others were similar to the characteristics found in the conventional systems. Comparisons based on multivariate analysis showed that the most contrasting systems were conventional tobacco and forest, while the other sites remained as intermediate between them. In general, the soil under forest showed the best indexes of soil quality, followed by the agroecological systems and, at the end, the tobacco-cropped soil. Some of the microbial and biochemical indicators of soil quality were capable to distinguish between soils differentially managed and point out to the tendency of the agroecosystem, whether to sustainability or to degradation.

ASSUNTO(S)

microorganismos do solo ecologia agrícola soil microbiology agricultural ecology solos - qualidade soils - quality

ACESSO AO ARTIGO

Documentos Relacionados