Page 20 - Agriculture Form Two

Agriculture for Secondary Schools

Conservation of soil moisture

Conservation of soil moisture is essential for maintaining soil water for
agricultural production. It is mainly targeted to minimise the water lost from
soils through evapotranspiration, percolation, and run-off. Run-off occurs when
the rainfall intensity exceeds the soil’s infiltration capacity, which measures the
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soil’s ability to absorb and transmit rainwater down the soil profile. Conservation
of soil moisture also helps to minimise the irrigation needs of crops. Various
methods can be used to conserve soil moisture. Most methods rely on providing
covers for the soil or other means to minimise water loss through evaporation,
percolation, and run-off. It is worth noting that most methods used for conserving
and improving soil fertility also apply here. These include:

(a) application of well-decomposed compost, farmyard manure, or crop
residue over the soil;
(b) placing mulches on the soil;
(c) crop rotation;
(d) practising mixed cropping and inter-planting; and
(e) terracing.

Management of deficit of soil moisture levels
When soil moisture levels are low, water must be applied to the soil to supply
sufficient moisture essential for crop growth. This is referred to as irrigation.
There are four main types of irrigation: surface, subsurface, drip, and overhead.

Management of excessive water levels in the soil
During rain or irrigation, the fields become wet. Rain/irrigation water penetrates
the soil and is stored in its spaces. When all the pore spaces are filled with water,
the soil is said to be saturated, and no more water can be added. Except for
some crops, such as paddy and taro, which withstand saturated soil for long
periods, a prolonged saturation state in the soil compromises the plant’s health.
To address the challenge of excess water in the field, the crop fields must have
drainage systems installed, making those soils even more productive. Drainage
of wet fields overcomes water-logged conditions and allows for a longer growing
season. Several mechanisms can help dikes and soil bunds can help protect fields
from unexpected floods and enable farmers to drain or retain water as needed;
drainage ditches can channel away excess floodwaters.

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04/10/2024 18:07
Agriculture form 2.indd 12 04/10/2024 18:07
Agriculture form 2.indd 12