Soil Structure Compaction and Erosion

There are many examples of the ways in which soil characteristics function towards ecosystem health and stability. Organic management strategies such as incorporating plant residues in soil maintain and improve soil structure of the soil in long term compared with conventional agriculture (Bailey and Lazarovits 2003). Gerhardt (1997) reported that an organic farm had a significantly ameliorated soil structure, with an increased A-horizon depth, organic matter content, porosity, earthworm abundance and activity and more developed aggregates than a conventional farm. Pulleman et al. (2003) found that organic management increased total organic matter content, earthworm activity, water-stable macro-aggregation and N mineralization, which are important indicators of soil quality. Improving other soil characteristics such as cation exchange capacity (CEC) in organically managed fields demonstrates a clear on-site sustainability advantage over the conventional systems (Wells et al. 2000). There are many reports that applying organic matter improves soil structure. Moreover, Forge et al. (2003) reported that the use of organic materials such as mulches can have profound effects on the structure of the soil food web, which is relevant to turnover of the microbial biomass and macronutrients. In organic agriculture application of green manures and catch crops are highly recommended. Green manure catch crops promote the sustainability of agricultural systems by reducing soil erodibility and by nutrient uptake and transfer to the following main crops. This effect efficiently reduces the risk of nitrate leaching. Biological nitrogen fixation by legume catch crops is an additional benefit, mainly in organic farming (Rinnofner et al. 2008). Depending on soil type and climate, farmers must be very cautious not to destroy the soil structure by tillage, vehicular traffic or grazing under wet conditions. Adverse soil structural conditions due to soil compaction or poor drainage greatly increase the chances of serious infection with many plant pathogens (Davies et al. 1997).

One of the costs that is rarely considered in evaluation of agricultural production efficiency, but could be significant, is productivity losses due to the soil and nutrient erosion in top soils, and loss of biodiversity, which are much higher in conventional than organic systems (Jordahl and Karlen 1993). Brown et al. (2000) reported that conventional farms showed the lowest values for aggregate stability and CEC while organic farms had the highest mean humic acid content and available water and air capacity. As the soil resource becomes degraded, the environment becomes less favourable for crop growth but better for plant pest and disease incidences: therefore, over the long-term productivity and profitability will be decreased (Wells et al. 2000).

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Organic Gardeners Composting

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