Before I articulate my comments in the following paragraphs, I like to commend FAO for undertaking the development of Code of Conduct on the management of Fertilizers (CoCoFe) and seeking stakeholder inputs. My comments are summarized below.
Fertilizer is a derived demand and its use is determined by several factors including profitability, marketability of produce etc. So COCoFe should be considered in the context of the entire value chain consisting of fertilizer supply, use and output markets. In the management of agricultural system all sources of nutrients (inorganic fertilizers, organic sources, manure and recycle materials) should be considered. So instead of Code of Conduct on the management of Fertilizers the title should be Code of Conduct on the management of Plant Nutrient. This change in title certainly makes the exercise more complex but the outcome would be more useful to the countries and practitioners since there is an upsurge in the use of organic materials and recycle products as a complement to and in some cases substitute for inorganic fertilizers.
In developing the recommendations for nutrient management one should consider the source, rate, placement and time of application based on soil and crop. The soil analyses is vital in determining the nutrient composition of the material and the rate of application not only of primary nutrients but also secondary and micronutrients. Both secondary and micronutrients are becoming more limiting to crop productivity particularly in Africa.
The heavy metal contents in fertilizers, recycled materials and manure need to be addressed from the environment and human health stand point as a part of the Code of Conduct exercise. I have recently done some analyses about the cadmium limits in fertilizers in countries and states. These limits vary widely. The most stringent limits under consideration is in the EU countries. The EU regulation proposes to set a limit of 20 mg Cd/kg of P2O5 in phosphate fertilizers over a time horizon on 12-15 years from current level of ~80 mg Cd/kg P2O5 . This limit is vastly lower than in other areas (Please see the diagram below). The sources cadmium in soils are several including geology of the region, rate of manure application, fertilizer etc. The uptake of cadmium by plants depends on its availability which is influenced by several factors including pH of the soil, the rate and source of organic matter, the available Zinc in the soils. Hence setting the limits for cadmium (and heavy metals) in fertilizers is quite complex and would need analysed in the Code of Conduct exercise.
While the Code of Conduct exercise is very useful and timely, it should lead to the establishment of a permanent structure to act as a clearing house of information for the management of plant nutrients. Such an information system should be 'open source' and the inclusion of information in the database should be peer reviewed.
Hope my comments are useful. Thank you for giving me the opportunity to share my thoughts.
Regards
Amit Roy
Amit Roy