Crops respond quickly, growing taller, greener and more lush. From the '70s to the early '90s, many farmers fed their fields with more nitrogen than was removed in harvested crops. And, in the last few years, the upward trend in the use of nitrogen fertilizer has resumed.
Phosphate use reveals a similar story but potash tells a different tale.
On a global scale, far less potash is applied by farmers than is removed by their harvested crops. Even the recent, slight increase in potash consumption is far too low to compensate for steadily increasing K removal. In view of the growing demand for more and better food, it is difficult to imagine that the goal to nearly double cereal production by 2020 can be achieved while the gap in the K balance is still widening. Global trends are interesting and may be informative, but nutrient need and, more particularly, fertilizer use, depend on factors that have more relevance at a regional level. Whether farmers apply fertilizers or not, and whether they have the necessary knowledge, money, credit or, indeed, whether fertilizers are locally available, depends as much upon political and economic history as in the inherent fertility of their soils or the nutrient demands of their crops.