We read an article in Appropriate Technology (Volume 28, No. 3; July/September 2001) about farmers in Niger who used bottle caps to distribute tiny amounts of fertilizer. Despite drought conditions, farmers who used this technique harvested 50 to 100 percent more millet than those who did not.
The caps hold 6 grams of fertilizer, and one capful was used for two or three plants. The amount of fertilizer used was only one-third or even less the amount usually used in Europe and North America
Niger is in the Sahel in the north of Sub-Saharan Africa. Soils in that area lack phosphorus (P) and are low in nitrogen (N) and organic matter. Plants respond dramatically to even small amounts of fertilizer.
The “Coca-Cola” technique (so called because coke bottle caps are most often used) was encouraged in the region by researchers working at the Sahelian Centre of the International Crops Research Institute for Semi-Arid Tropics (ICRISAT) in Niger.
We heard about a similar technique from Daniel Kropf, who sent us a paper done in conjunction with the Maradi Integrated Development Project (MIDP) in Maradi, Niger, and ICRISAT in Niger. The author describes the technique as the NPK hill placement method. A 15-15-15 formulation of NPK was mixed with 100 kg of planting seed. Two conditions seem necessary for increased yields: there has to be enough soil humidity (moisture in the ground should be at least 15 cm deep), and the minimum quantity of NPK that is applied should be 50 kg/ha. If the planting density is 10,000 pockets per hectare, each pocket should receive 1 teaspoonful or 5 ml of fertilizer.
In Niger, experiments were done by farmers who were willing to use one hectare of farmland for the experiment. Half of each plot was planted traditionally by two people (a hole was made approximately every meter by one person, and seed was dropped in and covered up by the other). On the other half of each plot, three people were involved. One made a hole, the next dropped fertilizer in, and the third planted the seed and covered it.
At the end of the experiment, 67 plots were analyzed. Overall, control plot yields averaged 234 kg/ha and NPK hill placement plot yields averaged 577 kg/ha—a more than 100% yield increase! Economically, farmers could make money if they sold the extra grain, even though they also had to buy a bag of NPK at the beginning of the season. Farmers found that fields with NPK applied had less witch weed (Striga hermonthica) because the nitrogen improved the soil fertility
The author commented that NPK placed in the planting hole gives the young plants a quicker start earlier in the season. “The nitrogen and soluble phosphorus help improve the establishment of a good root system which can better exploit soil resources. The nitrogen is exhausted early in the season but the phosphorus sustains a higher crop yield through harvest.” We read in the report that the Hausa name used by villagers to describe the NPK hill placement technique is “Gani Ya Kore Ji”, which means “Seeing is Believing.”
Berkelaar, D. 2004. Bottle-cap Fertilizer. ECHO Development Notes no. 84