PHOSPHORUS: A LIMITED RESOURCE

Soil is a living, breathing ecosystem. Just as you and I breathe, soil too re­spires, and we measure that respiration rate as an indicator of microbial activity in soil. While there are large, non-mi­croscopic organisms living in soil such as worms, insects, and small mammals, none of them exist by the billions in just a handful of soil except the microbes.

There are many scientific classifica­tions for microbes in soil, but from the farmer’s perspective, only two catego­ries are relevant. Goodmicrobes (major­ity) and bad microbes (small minority). Good microbes enhance plant growth, and bad microbes cause disease in plants. Of course, things are never quite so clear-cut in nature. Some things can be good under some circumstances and bad under other circumstances. So keep in mind this is a simplification of what are, in reality, very complex interactions.

Weak plants may also be susceptible to organisms in the envi­ronment that normally would not have much impact on them. For instance, a nutrient deficiency might weaken a plant and lead to susceptibility. The good news is, of the thousands of microorganisms identified in soil thus far, only a handful of those really falls into the bad category. The good far outweighs the bad, and with a little thoughtful management, you can keep it that way.

In the case of good microbes, we can take this a step further and narrow our focus to the most crucial organisms within this group, which are those that provide the macro and micronutrients plants require for growth. The most limiting of these nutrients is typically phosphorus

Phosphorus is an element, meaning there is a phosphorus atom. It can be nei­ther destroyed nor created. The amount that exists on this planet is all we have. When we remove crops from the field we remove the phosphorus those plants took up. It becomes part of the food we eat.

Nitrogen can play a close second in the nutrient race, but in most soils phosphorus is the most limiting nutrient, often occurring in quantities a thousand times lower than other minerals.

Phosphorus is a limited resource. Mining phosphate rock to produce fer­tilizers requires a significant amount of energy. Fuel is manufactured from oil, which is also a limited resource. As phosphate supplies dwindle we will try to tap less accessible deposits, increas­ing the energy required to reach those deposits. We will also begin processing lower-quality phosphate rock with more impurities, increasing processing costs.

THE SOLUTION

We need to increase our efficient use of resources such as phosphorus. We really can’t afford to waste it on saturating our soils and killing fish. This will extend our supply, help keep costs under control, and give us the time we need to re-establish the natural nutrient cycles agriculture once depended upon.