How to Determine Soil Fertility: A Few Tips

Several methods can be used to determine the fertility status of a region's soil. Only the most important ones are presented here: visual diagnosis, plant analysis, biological tests, soil testing, and field trials, for better soil fertility management.

Visual diagnosis

A plant shows characteristic symptoms if a nutrient is present in the soil in insufficient quantity for its normal growth and development. These symptoms make it possible to diagnose the missing nutrient and decide on solutions. This method is quick and requires no special equipment; however, it has certain drawbacks:

• deficiency symptoms must be fairly advanced to be identifiable, by which point it may already be too late for the plant;
• symptoms of certain deficiencies are not very obvious and only appear once the deficiency is severe;
• deficiency symptoms can be complicated or masked by other factors such as weather, insects, and disease.

Plant analysis

Elemental concentrations are determined using generally complex laboratory methods. The main drawback of these methods is that they're costly. Plant analysis is only useful for perennial (long-lived) plants.

Biological tests

These laboratory tests are based on the principle that the general mineral nutrient needs of microorganisms are similar to those of certain plants. The advantage of these tests is that, unlike field trials, they can be carried out quickly (in 3-4 days).

Soil testing

Soil testing is a better method than observing deficiency symptoms or plant analysis, since it allows a plant's nutrient needs to be determined before planting. It's simpler and less time-consuming than the biological method. Soil analysis itself is fairly complex laboratory work. One of the most critical steps in the analysis is the sampling procedure.

Field trials

The most reliable and satisfactory method for determining the optimal amount of fertilizer or manure to use is based on several series of field trials carried out on experimental farms and on farmers' fields. Although these trials give reliable results, these are generally only obtained after several years of testing. Their main drawback is that they require time and money. The average farmer usually cannot afford such costs.