Importance of the Fallow Period
There is restoration of fertility lost during the cropping period. If the cropping period had not been too long, the fallow period may be enough to restore the fertility. If it is otherwise, it may be necessary to apply chemical fertilizer, close cycle is established under a forest canopy, and nutrients pass from soil to vegetation and back to the soil.
Suppression of weeds. The land may be abandoned due to invasion of weeds. The emerging vegetation and trees during fallow help to suppress weeds in addition to recycling nutrients from deep in the profile.
High level of organic matter is maintained by the large returns from the vegetation in form of litter and timer fall. The roots help to bind the soils, thus increasing infiltration, minimizing run off and erosion.
Diseases and pests are controlled by fallow. Fallow may deprive insect pests their host plants thus starving them and reducing their population.
Read Also: Appraisal of Shifting and Continuous Cultivation
What Happens When Vegetation is Removed or During Burning?
Clearing of vegetation causes the close nutrient cycle to be broken. There is an initial flush of nutrients due to increase mineralization of organic matter especially under tropical conditions.
Burning provides ashes to raise the soil pH. But there is loss of nitrogen, sulphur, CO2 and other harmful products which add to the global warming process.
Apart from N and S which escape to the atmosphere during burning, other nutrients remain in the ash and are present as carbonates and phosphates such as K2CO3, K3PO4, Ca CO2, and Mg CO3 which react with soil acids (alkaline effect) to raise soil pH.
Read Also: Soil Temperature and Plant Growth