Some considerations about the safety of organic fertilizers

In agrotecnia we have been socializing agroecological alternatives for the management of crops in agroecosystems, within these alternatives for fertilization are organic fertilizers that are made with local vegetable and animal waste, which can be found within the production units, the intention is that through some methods this organic matter is transformed to obtain essential elements that improve certain characteristics of the soil, in addition to improving the biological characteristics with the presence of microorganisms found in these products.

Logically what we want when incorporating these products into the soil is to improve the aforementioned characteristics and that they do not negatively affect the yield of crops, the health of animals when we fertilize pastures and of course human beings when we consume some item with the presence of some toxic substance or pathogens. We mention this because some organic waste used may contain some pathogens, therefore, it should be considered that in the process of making fertilizers, the pathogens and toxic substances present in the organic elements used must be eradicated or significantly reduced.

In this same vein, when talking about the transformation of organic matter, we automatically think of microorganisms who are the ones who carry out this decomposition process, of course pathogenic microorganisms can proliferate in these processes, but the method used must ensure that said microbiota decreases considerably, for example, in the composting process there is an increase in temperature between 40 and 65 °C and the bokashi between 45 and 50 °C, this variable within the process plays a fundamental role for the safety of the fertilizer that you want to obtain. According to Atlas and Bartha (2002), in the composting process the transformation begins with the presence of mesophilic bacteria that adapt to temperatures between 20 and 40 °C and as decomposition begins the temperature increases causing changes in the population of microorganisms and thermophilic microorganisms begin to proliferate at temperatures around or above 60 °C.

When the compost reaches the aforementioned temperature, the ideal is that it is maintained at that temperature to favor the decomposition process of the organic matter and reduce the pathogenic microorganisms that are present. In this sense, Coiné (2000) mentions that Escherichia coli, a bacterium that may be present in bovine manure, can be eradicated from compost because the maximum temperature for its growth is 42°C and compost can reach 60 °C, other researchers have pointed out that pathogens can decrease when they are exposed to high temperatures for one or several days.

There are also other types of methods for obtaining organic fertilizers such as vermiculture where Californian red worms are used for the decomposition of organic matter, in this case the worms transform the organic matter used and when passing through the digestive tract of the same according to Fuentes (1997), a pH change occurs and the addition of new microorganisms that can cause the reduction of pathogens. On the other hand, there are fertilizers that are obtained through anaerobic fermentation, in these processes lactic acid bacteria produce a decrease in pH, which can cause, as mentioned above, a decrease in pathogens.

Dear readers, as it could be evidenced within the different methods that can be implemented for the decomposition of organic matter there are variables such as temperature, pH or the absence of oxygen that considerably decrease the pathogenic microorganisms of organic fertilizers. After making an organic fertilizer, germination tests can be implemented to determine if the product is toxic and also a microbiological analysis where it will be possible to observe what type of microorganisms are present and whether they can affect the yield and quality of agricultural items.