Fertilizer recommendation to farmers in Nigeria often appears as straight N, P, or K e.g. urea, SSP and muriate of potash. Yet it is much more convenient for the farmers to apply fertilizer-nutrient needs in one single formulation. For this reason, the use of compound fertilizer 15-15-15 has also been very widely adopted by farmers. In fact over 70% of all fertilizer used in Nigeria today is in the form of 15-15-15. The problem with too much reliance on 15-15-15 is that this fertilizer has low N and P content, and it lacks Sulphur or zinc. Yet supplementary Sulphur and zinc appear to be necessary for optimum crop performance in many parts of the country, particularly, the savanna grasslands. There is indication that B may also be needed in some parts. The under listed crop and soil fertilizer formulations were developed from Soil Fertility Maps of Nigeria:
SOIL AND CROP SPECIFIC FERTILIZER FORMULATIONS BASED ON SOIL FERTILITY
| STATES | FERTILIZER FORMULATIONS |
| Anambra | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Abia | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Adamawa | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Akwa-Ibom | NPK: 20-5-5 + 1Zn + 2Ca for cereals and vegetables NPK: 15-5-10 + 1Zn + 2MgO + 2Ca for roots, tubers and tree crops. |
| Abuja | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Bauchi | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Benue | NPK: 20-10-5 + 1ca + 15 + 1Zn for cereals, cotton and vegetables NPK: 10-20-10 + 1S + 1Zn for legumes. NPK: 15-10-10 + 1Ca + 2MgO + 1Zn for roots, tubers and tree crops. |
| Borno | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Ebonyi | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Edo | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Ekiti | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Enugu | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Cross River | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Delta | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Bayelsa | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Gombe | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Imo | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Jigawa | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Kaduna | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
| Kebbi | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
| Kwara | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Kogi | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Kano | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
| Katsina | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
| Lagos | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Nasarawa | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Niger | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Ogun | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Ondo | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Osun | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Oyo | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Plateau | NPK: 20-10-5 + 1ca + 15 + 1Zn for cereals, cotton and vegetables NPK: 10-20-10 + 1S + 1Zn for legumes. NPK: 15-10-10 + 1Ca + 2MgO + 1Zn for roots, tubers and tree crops. |
| Rivers | NPK: 20-10-5 + 1Zn + 2Ca for cereals and vegetables. NPK: 15-10-10 + 2Ca + 2MgO + 1Zn for roots, tubers and tree crops. NPK: 10-20-10 + 1S + 1Zn + 2 Ca for legumes. |
| Sokoto | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
| Yobe | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Taraba | NPK: 20-10-10 + 1S + 1Zn for cereals. NPK: 10-20-10 + 1S + 1Zn for legumes |
| Zamfara | NPK: 20-5-10 + 1Zn + 1S for cereals and vegetables. NPK: 15-5-10 + 1Zn + 1S for roots, tubers and tree crops NPK: 20-5-10 + 1Zn + 1S + 1B for cotton NPK: 10 -20-10 + 1S + 1Zn for legumes |
Whichever of these is produced, there is need to conduct field studies to determine the optimum rates for different crops under different soil fertility conditions. Certain parts of the country may have specific needs that are different from the recommended formulations. Specific formulations may be recommended for such areas.
Fertilizer Blending Facilities
With further development of soil testing programme in Nigeria, and farmers’ acceptance of the idea of soil testing for fertilizer recommendation, there will be need for fertilizer-mix formulations that correspond accurately with soil test recommendations of individual fields (particularly for medium and large-scale farmers). Therefore, it will become necessary to use bulk blending plants for formulations of fertilizer compounds. It would be desirable to have fertilizer mixing plants in different parts of the country, such that it will be possible to have a blending facility in close proximity of the intended clients. Initially, one bulk – blending plant is suggested for each of the six main ecological zones of the country, which will later be increased to one per State at the minimum.
Specific Nutritional Problems
Information is required on some specific nutritional aspects in certain crops which have otherwise been fairly intensively studied. For example, studies on the micro-nutrient need of maize, groundnut and cotton need intensifying, especially, in the Savanna and Sudan zones. There is currently inadequate information on the effects of long-term, continuous application of the major nutrients on the soil properties, including the balance of minor elements.
Investigations are needed to test the effectiveness and economics of rock phosphate as a possible source of phosphorus for tree crops in place of single super-phosphate, especially in the southern parts of the country. There is also the need to evaluate the lime requirements of acid soils of Nigeria.
Nutrition in Crop Mixtures
Intensive work on the agronomy of crop mixtures within Nigeria is new and is concentrated on answering two questions: Whether or not mixtures yield more than equivalent sole crops, and the rationale behind mixtures. Only within the last few years have trials shown whether crops within mixtures respond to fertilizers in the same degree as sole crops. Most serious efforts should be directed towards determining the rate, timing and method of fertilizer application.
Fertilizers in Forest Production
Probably because of the administrative set up whereby forest management has always been separated from that of field and pasture crops, fertilizers are rarely used in commercial forest production. Accurate statistics about the total fertilizers used annually on forest production are hard to come by, but the amounts are likely to be much less than field crops. However, with the growing importance of forests and forest products in the national economy, it is imperative that attention be given to the role of fertilizers in commercial forest production. Some studies along this line have recently engaged the attention of researchers at the Forestry Research Institute., Ibadan. There is the need to encourage such studies.
Source of Nitrogen
The bulk of the nitrogen used in Nigeria should preferably be in form of urea, DAP and/or calcium ammonium nitrate. A substantial quantity of ammonium sulphate is however used in many parts of the country especially on crops like oil-palm. It is presently not clear whether its apparent preference is as a result of the sulphur content (23% S) or any other effect. Investigations are, therefore, necessary to determine the possibility of sustaining high yields of these crops using non-acidifying fertilizer sources.
Meanwhile, suitable sulphur containing sources e.g. single super-phosphate or any sulphur-bearing compound fertilizer formation should be used as sulphur sources for areas and crops needing sulphur.
