The negative results involving absence of root development in plants under artificial lighting (20 W lamp) instigated the children to elaborate a hypothesis to be tested explaining this. The positive experimental results showed how the light source and the nutritional richness of the soil are important determinants of plant survival and growth. This experiment was attended by 21 children with ages ranging from 10 incomplete years to 10 years old. The objective of present study was to describe the results of the experiment performed on cuttings of Boldo Mirim raised in two types of soil, two types of light source (20 W lamp or sunshine) at four intensity (10%, 30%, 50%, or 100%). 'Is it possible to promote the construction of knowledge about phenotypic plasticity expressed by plants among elementary school students?” To answer this question, it was proposed to carry out experiments together with second year students of elementary school using the plant popularly known as Boldo Mirim (Plectranthus neochilus Schlechter). Hence, earthworm casts are significant natural sources of plant nutrients, also in soils with high dominance of geophagous earthworm species. Field-collected geophagous earthworm casts had considerably higher concentrations of plant nutrients than bulk soil (28% higher concentration of Tot-N, 36-53% for P AL, 40-59% for K AL).

With earthworm densities such as those found in farming systems with ley and animal manure, an estimated amount of 221 tonne of topsoil per hectare passes through the earthworm digestion system within one year. However, the earthworm density and biomass was not lower with shallow as compared to deep ploughing (25 cm depth). Because geophagous species prefer the upper soil layer, shallow ploughing (15 cm depth) was expected to be detrimental. Application of animal manure increased earthworm density and biomass. Even short-term leys for green manure had a positive effect, likely due to high clover content. One year of ley in the crop rotation increased earthworm burrow density, earthworm density and biomass. Earthworm density, recorded in autumn varied between 30 and 350 individuals m-2 in different studies, with the lowest values found in conventional all-arable farming systems. Lumbricus terrestris is also present in our studies even frequently found in an all-arable crop rotation with annual ploughing. rosea dominate the earthworm fauna in Norwegian arable soil.

Geophagous (soil eating) species such as Aporrectodea caliginosa and A. The effects of crop rotations, fertilization, soil tillage and compaction on earthworms are presented, based on various field experiments. This paper presents Norwegian studies of earthworms (density, biomass, burrows density, species, juvenile to adult ratios) in arable soil in Norway conducted during the last 20 years.

Microcosm manual