Continued depletion of plant nutrients and organic matter in the soil and inadequate availability of soil moisture for crop growth, especially under dryland conditions, are major problems affecting sustainable crop production in many countries. The use of organic fertilizers and water-retaining products, if economically viable, may contribute to overcome these constraints and improve land productivity.
Even though organic fertilizers and other organic materials are likely to be used in the same area where they are produced, because of their bulky nature and high transportation cost, they may have to be imported from elsewhere if not available locally. Water retaining products are, at present, mainly produced in developed countries, and if economically viable, they may be used to improve water-holding capacity and prevent loss of moisture and nutrients, especially in light soils and in drylands. They may be of particular interest for commercial crops.
It appears useful to make available to farmers, extension services, agricultural research centres, educational institutes, decision makers and others, a data set on such commercially available products. Accordingly, a first attempt has been made to compile such a database.
It is intended to expand the present database with additional information from producers and also with additional products, as and when received. This can be submitted by filling and sending the following submission form.
The information sheets containing data provided by the producers have been organised into several product types: Organic fertilizers, Organo-mineral fertilizers, Organic amendments and Water-retaining products.
Each information sheet is expected to contain the following information:
- Type of product
- Product name
- Manufacturer's contact information
- Country of production
- Product description (content of N-P2O5-K2O and other nutrients, if any)
- Statement of uses and benefits, rates of application, etc.
- Product assessment (field results, experimental data with agro-economic interpretation)
- Price information
- Package size, availability for export, etc.
However, at present, in many cases one or the other information is missing and efforts will be continued to fill these gaps.
Terminology and definitions
The term organic fertilizer is used here to describe nutrient sources of organic origin either natural or processed, containing at least 5% of one or a combination of the three primary nutrients (N; P2O5; K2O). In this sense organic materials of animal origin such as guano, bone meal, fish meal, leather meal, are true organic fertilizers, but commonly used organic sources of nutrients such as manure, slurry, compost and sewage sludge, sometimes are not. If the nutrient content is below 5% they are considered as organic amendments.
Other definitions [from the International Organisation for Standardisation (ISO) and the Soil Science Society of America (SSSA)] are available, but they do not specify minimum nutrient content.
Carbonaceous material mainly of vegetable and/or animal origin added to the soil specifically for the nutrition of plants (ISO definition).
By product from the processing of animals or vegetable substances that contains sufficient plant nutrients to be of value as fertilizers (SSSA definition).
Important quality criteria include nutrient content and test of established critical limits for heavy metals and pathogens.
2. Organo-mineral fertilizers
Organo-mineral fertilizers are obtained through blending or processing one or more organic materials with one or more mineral fertilizers to enhance their nutrient content and fertilizing value. In this type of fertilizer the mineral nutrients are protected by the binding and absorption of the organic component, leading to a gradual release of nutrients in the soil and to a reduction of nutrient losses.
3. Organic amendments
Soil amendments are materials that are applied to the soil to correct a major constraint other than low nutrient content.
The SSSA definition:
Any material such as lime, gypsum, sawdust, compost, animal manures, crop residue or synthetic soil conditioners that is worked into the soil or applied on the surface to enhance plant growth. Amendments may contain important fertilizer elements but the term commonly refers to added materials other than those used primarily as fertilizers.
Organic amendments are used with the objective to improve physical soil properties, either directly or by activating living organisms in the soil. They include organic materials of widely varying compositions (for example, farmyard manure, liquid or semi-liquid manure, straw, compost and green manure produced on the farm itself, peat and humic acids).
Organic amendments are important primarily because of their organic matter content. All soils require the supply of organic matter as carrier of utilisable energy and nutrients for the soil organisms, as well as for:
- improvement of soil structure and porosity
- increase in water-holding capacity of soils
- improvement of aeration
- reducing soil temperature fluctuations
- storage of nutrients in exchangeable form
- provision of nutrients
4. Water retaining products (superabsorbents)
Water retaining products are natural or synthetic materials, that can absorb large amounts of water, as much as hundreds of times of their own mass, and gradually release it to plant roots.
In the case of potted plants for sale, superabsorbents may be used to increase the interval between waterings or to reduce pot size for a given plant size, and thus lower labour costs in the period before sale. In the case of irrigated horticulture or agriculture, they may help to increase the irrigation intervals, and help decrease the proportion of water lost by leaching out of the root zone. In the case of rainfed cultivation, they may help bridge longer intervals without rain.
So far, their use in horticulture and agriculture has been largely limited to highly capital-intensive conditions: mainly in industrial countries and in some oil-producing countries. Their cost has essentially precluded their use in developing country agriculture, whether rainfed or irrigated.