The Planter
A hand and foot operated precision planter, with no moving parts, designed for women farmers practising Conservation Agriculture.
The hand-fed planter is able to plant maize (corn) and pulses (beans), as well as other seeds, together with a precise amount of fertiliser as a nutrient for each seed, through a surface mulch under a range of soil conditions.
The design of the tool uses body weight to operate a foot pedal, supplying the energy used to create two slots 50mm apart through the surface layer, in a gradual manner combined with a forward/backward rocking motion. The shape of the spear makes gradual penetration easier while the sides compact the soil, conserving its integrity.
After the two holes have been made, the planter — with the spears still in the ground — is pushed away from the operator in order to open up the holes. A single seed is dropped by hand into the slot through one funnel, while a precise amount of fertiliser is dropped into the other funnel. The seed and nutrients are covered by stamping a heel over the holes. This not only closes the holes but also leaves a shallow indentation that is useful for water harvesting during rains.
The arrangement of the seed is intended to give each its own space, to ensure minimum competition for light and soil moisture. The spacing for maize and beans should give the optimum plant population for the agro-climatic conditions of that area — information usually available from local agricultural extension officers, drawn from experimental work carried out by research stations.
The amount and type of fertiliser applied to each seed depends on the results of soil testing, where it has been carried out, or on advice from the extension officer. A typical target plant population for maize is 50,000 plants per hectare: a spacing of 25cm between seeds in a row, with a row width of 75cm, gives the required number of plants.
The seed and fertiliser are carried by the operator in pouches suspended around the chest. It's easy to drop one seed at a time, but harder to judge a precise amount of fertiliser. A pinch between fingers and thumb gives a fairly constant amount, but small, easily available containers give a more precise measure — in trials, a soda water bottle-top was used for its wide availability. A full bottle-top of fertiliser weighs around 3g.
The varying sizes of medium and large grains of maize make it difficult to design a singulating mechanism without very close seed grading, which isn't always available. Any such mechanism would also increase cost and complexity — both often sensitive issues for purchasers. Evaluation of mechanisms designed to plant single seeds with accuracy hasn't found a reliably suitable solution: some may plant two or three seeds, and results show this can mean smaller cobs, longer harvest time, and reduced stem/stover weight, which matters for dry-season animal feed.