There is, however, a continuing tendency to be unaware of the specific role of, and therefore need for, potash. This is because low-yielding, subsistence crops can obtain sufficient quantities from weathered minerals and plant residues, provided that the latter are put back on the land and not used for fuel or thatching, purposes for which they are much valued. Furthermore, potassium acts on quality and it acts discreetly. This means that unless farmers can earn a premium for higher quality produce there is little incentive to pay for a nutrient whose omission does not immediately become apparent. Crops that are stressed through lack of potassium are more susceptible to drought, diseases and pests, not least because the yellowing of leaves positively attracts aphids.
Lack of awareness leads to lack of demand and lack of availability.
Input suppliers target commercial growers and do not waste their marketing resources targeting farmers who cannot afford to buy the product. The logistical problems associated with purchasing fertilizer, when there are no suppliers in the immediate neighbourhood, and the only means of travel available to smallholder farmers is by foot or by bicycle, highlights another problem - accessibility. They need a local supplier who, in turn, needs to be confident that the purchased stock will be sold. Here, perhaps, is the pivotal point at which accessibility, availability and affordability come together. Fertilizer in sub-Saharan Africa is disproportionately expensive.