Observation

 

Many candidates were unable to state the effects of harrowing, flooding and overgrazing on soils as well as write correctly the botanical names of common pasture grasses.

The expected answers include:

2. (a)            (i)       Definition of bush fallowing
                                    Bush fallowing is a practice whereby a piece of land is left uncultivated for
                                  a period of time for it to regain lost nutrients.  
                                                         
                        (ii)       Benefits of bush fallowing in agriculture
-           It helps to break the cycle of some plant diseases
-           Helps to break the cycle of some plant pests
-           Leaves of plants that fall and decompose add nutrients to the soil
-           There is an increase in the population and activities of
soil microorganisms
-           Reduces the rate of run-off / erosion
-           Improves soil structure /
-           Improves the activities of soil flora and fauna
-           Improves soil porosity
-           Reduces leaching of soil nutrients
-           Lost nutrients are cheaply replenished                   

            (b)       Effects of farming practices on soils
(i)         Harrowing
-           Controls weeds                                              
-           Break soil clods to fine tilth                          
-           Promotes aeration
-           Makes the soil suitable for plant root penetration
-           Enhances water infiltration
-           Improves soil structure
-           Exposes soil to erosion

(ii)        Flooding
-           Makes the soil waterlogged                           
-           Could reduce soil salinity                              
-           Reduces the activities of soil microbes          
-           Increases soil acidity 
-           Causes leaching of soil nutrients
-           Reduces soil temperature
-           Causes erosion
-           Controls weeds                                                       

(iii)       Overgrazing
-           Exposes the soil to agents of erosion such as wind and water/enhances surface run-off.
-           Trampling by livestock leads to soil compaction
Reduces water percolation and infiltration
-           Leads to loss of soil fertility
-           Exposes the soil to the direct effects of solar radiation
-           Destroys soil structure.                                                                                                          
(c)        Common pasture grasses
-           Giant Star grass (Cynodon plectostachyum)
-           Guinea grass (Panicum maximum)
-           Northern gamba grass (Andropogon  gayanus )
-           Elephant grass (Pennisetum purpureum)
-           Bahama grass (Cynodon dactylon)
-           Southern gamba grass (Andropogon tectorum)