You run a large farm that is considering using sludge from wastewater treatment plants as fertilizer. You have been told that the sludge can increase the growth rate of your crops, and you know that using the sludge will prevent it from making its way into landfills. However you have also heard that sludge can contain pollutants such as heavy metals and pathogens. What questions would you want to ask before deciding to use the sludge? Do you feel that the benefits outweigh the costs?

Explanation:

As shown in the question above, some farmers choose to use sludge as a fertilizer. It is true that the sludge brings some benefits such as the increase of organic matter in the soil and the promotion of nutrients, mainly nitrogen, which is essential for the growth of the plant and which is found in low concentrations in the soil.

However, the sludge can bring some problems, as it can contain nitrate, heavy metals and toxic elements and can contaminate the soil in a great way. Before deciding to use the sludge as a fertilizer, it is necessary to question the environmental impact that it will promote and if this impact will be very large, such as contaminating the water table, for example.

However, the pH of the soil can neutralize these toxic elements and heavy metals, however, the closer to neutrality the pH of the soil is, its neutralization capacity will be lower.

Sludge can also cause an increase in soil acidity as a result of nitrification reactions, which will increase the costs of liming and plastering.

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