From an agricultural point of view, a fertile soil is one that can provide adequate amounts of nutrients for plant growth. This results in better crop yields and quality.
There are various factors that define and contribute to soil fertility.
Mineral composition – knowing the mineral composition of the soil, we can predict its ability to retain plant nutrients. This is determined by the source rock, the climate, biological and chemical processes.<
When referring to the soil mineral nutrients, there’s a wide gap between the total amount of mineral nutrients in the soil and their availability to the plant. In fact, only a small fraction of the minerals composing the soil will be available for the plant.
Applying fertilizers and soil amendments, is a key element in enhancing and preserving the mineral content of the soil and therefore, a proper fertilizing program is one of the most influencing factor on the soil fertility.
Soil pH – Soil pH is important in maintaining proper soil fertility. It affects the nutrient availability in the soil. A pH range of 5.5-7 is considered to be adequate for most plants.
Soil Texture – Different sized minerals particles give the soil its structure - sand, silt a clay. In comparison to sandy soils, clay soils are capable to retain more nutrients and so act as a bigger nutrient reservoir.
The CEC (Cation Exchange Capacity) of the soil can be used as an indication to the soil fertility. Higher CEC means higher capacity of the soil to hold nutrients. Clayey soils will have a higher CEC than sandy soils and therefore, will usually be more fertile.(A – Clay. B – Sand):
Organic Matter – The organic matter is considered to be a source of nitrogen and phosphorus. Nitrogen and phosphorous can be mineralized and become available for plant uptake. The organic matter also increases soil fertility, as it improves the soil structure while increasing the CEC.
Inadequate use of fertilizershas negative effects on soil fertility. Over-using fertilizers is not only costly, but also creates soil health problems. Mineral salts that are not used by the crop, accumulate and affect future crops grown on that soil.
On the other hand, without using sufficient amounts of fertilizers, originally fertile soils will gradually deplete of nutrients. This way, the crop would not reach its potential yield and the grower’s profits will decrease.
Applying fertilizers should be correlated to the target yield and preferably be split according to the growing stage of the crop.
Soil and plant tissue analysis, are an important tool to keep track of the fertility status of the soil. In order to achieve high yields and to maintain soil fertility for the following years, an appropriate fertilizing program should be established.