Interrill erosion occurs by the particle breakdown caused by raindrop impact, by particle transport in surface runoff, by dragging and suspension of particles disaggregated from the soil surface, thus removing organic matter and nutrients that are essential for agricultural production. Crop residues on the soil surface modify the characteristics of the runoff generated by rainfall and the consequent particle breakdown and sediment transport resulting from erosion. The objective of this study was to determine the minimum amount of mulch that must be maintained on the soil surface of a sugarcane plantation to reduce the soil, water and nutrient losses by decreasing interrill erosion. The study was conducted in Pradópolis, São Paulo State, in 0.5 x 1.0 m plots of an Oxisol, testing five treatments in four replications. The application rates were based on the crop residue production of the area of 1.4 kg m-2 (T1- no cane trash; T2-25 % of the cane trash; T3- 50 % trash; T4-75 % trash; T5-100 % sugarcane residues on the surface), and simulated rainfall was applied at an intensity of 65 mm h-1 for 60 min. Runoff samples were collected in plastic containers and soon after taken to the laboratory to quantify the losses of soil, water and nutrients. To minimize soil loss by interrill erosion, 75 % of the cane mulch must be maintained on the soil, to control water loss 50 % must be maintained and 25 % trash controls organic matter and nutrient losses. This information can contribute to optimize the use of this resource for soil conservation on the one hand and the production of clean energy in sugar and alcohol industries on the other.
Com a adoção da colheita mecanizada no sistema de manejo da cana-de-açúcar, surge a preocupação da compactação do solo e seus efeitos danosos na disponibilidade de água às plantas. Uma recente técnica de manejo da mecanização agrícola denominada controle de tráfego representa uma alternativa para o cultivo de cana-de-açúcar, pois separa as zonas de tráfego das zonas em que há crescimento das plantas, concentrando a passagem de pneus em linhas delimitadas. O presente estudo teve por objetivo avaliar o efeito do controle de tráfego em áreas cultivadas com cana-de-açúcar, sobre a qualidade física do solo, no sistema de cana colhida mecanicamente sem queima (cana-crua). A pesquisa foi desenvolvida em área cultivada com cana-de-açúcar com os seguintes tratamentos: com colheita mecanizada tradicional; com controle de tráfego - aumento de bitola; com controle de tráfego - aumento de bitola e piloto automático. Foi avaliada a densidade do solo, a macro e a microporosidade do solo nas camadas de 0,00-0,10, 0,10-0,20 e 0,20-0,30m de profundidade, na linha de plantio, no entrerrodado e sob o rodado da cultura da cana-de-açúcar, bem como, o intervalo hídrico ótimo na camada de 0,00-0,20m de profundidade. O trabalho foi realizado dentro de um experimento trifatorial, com parcelas subsubdivididas no delineamento em blocos ao acaso. O intervalo hídrico ótimo permitiu verificar que os manejos com controle de tráfego apresentaram uma maior disponibilidade de água às culturas.
We hypothesised that cadmium exposure would hinder growth and secretion of carbon-degrading enzymes by mycorrhizal fungi, and that this would vary according to their tolerance to cadmium stress. The enzymes measured were β-Glucosidase, β-Xylosidase, β-D-cellubiosidase, N-acetyl-β-Glucosaminidase in three strains of ectomycorrhizal fungi
Hebeloma subsaponaceum
,
Scleroderma
sp.,
Hebeloma
sp. and a feremycorrhizal fungus
Austroboletus occidentalis
. Fungi were subjected to cadmium stress for 28 d (in modified Melin-Norkrans liquid medium). The results showed unanticipated differential response of enzyme activities among the fungal species, including potential hormesis effects.
Austroboletus occidentalis
showed an increase in enzyme activity under cadmium stress.
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