Factors affecting soil fertility and productivity

Soil fertility is the ability of the soil to provide nutrients in proper quantities and in a balanced way for the growth of plants. A fertile soil should have the correct proportion of plants nutrients and optimum pH

Soil productivity is the capacity of the soil, in its normal environment to support plant growth

Soil fertile greatly affects soil productivity. A fertile soil always leads to high soil productivity

 However, soil productivity is affected or influenced y other factors other than the soil fertility. For example, presence of weeds in the farms may lower the level of productivity of the soil, even when the soil fertile. Other factors like farming methods used may also lower the productivity of the soil.

  In farming, soil fertility may lost through many ways, some of these  ways are as result of human activities while others are through natural process. 

The following are some ways through which soil fertility may be lost:

(1) Leaching

This is common with nutrients that are highly soluble such as nitrogen, these nutrients are carried to lower far from beyond the reach of many plants roots, soil with many leached nutrients are infertility.

(2) Soil capping

This is when the soil is covered (capped) with an impervious material which prevents the penetration of rainwater into the soil, this leads to surface run – off. This denies the soil adequate moisture and exposes the soil to erosion

(3) Soil erosion

This is the carrying away of the top fertile soil by moving water and wind. Erosion leads to loss of the fertile top soil and plant nutrients, this makes the soil infertility.

(4) Monocropping

Monocropping is the practice of growing one type of gropes on a piece of land for a long time. The gropes grown uses only those nutrients it needs while other nutrients remain unused, this leads to exhaustion of some nutrients and eventually to their deficiency in the following years

There is also likelihood of build up of pests and disease, the same pest and disease are passed on from the residue of previous crop, this leads to low yield

(5) Accumulation of salt

Soil water contains dissolved minerals salts from the parent rock; some of the salt comes from decomposition of organic matter.

Under normal condition, the salts are washed away by rain water, thereby keeping their concentration in the soil low. However in arid and semi-arid areas the rainfall is irregular and is not enough to remove the salt from the soil.

This together with the high evaporation rate and poor drainage, leads to accumulation of salt on or below of the soil surface. The salt cause deficiency of water in plants as water moves out of the root in the soil under the osmotic pressure of the salt solution.

(6) Change in the pH

Inappropriate use of fertilizers may change the soil pH, for example, the use of acidic fertilizer over a long period of time can make the soil acidic.

Change in pH affects the activity of the soil microorganisms and the availability of some nutrients. This, in run, affects the fertility of the soil.

(7) Burning of vegetation

When vegetation is burned, organic matter is destroyed; this affects the activities of microorganisms such as nitrogen fixation and decomposition of organic matter.

Accumulation of the resulting ash also causes imbalance of nutrients in the soil. Burning of vegetation also exposes the soil to agents of erosion such as wind and water