Question 3
Table 1 below illustrates a poor crop rotation plan in Year 1. Study it and answer the questions that follow.
Table 1
Year |
Plot 1 |
Plot 2 |
Plot 3 |
Plot 4 |
1 |
Cowpea |
Maize |
Yam |
Cassava |
(a) Give three reasons why Table 1 is regarded as a poor crop rotation plan. (3 marks)
(b) Using the crops in Table 1, complete Table 2 with a good crop rotation plan starting with cassava in Plot 1.
Year |
Plot 1 |
Plot 2 |
Plot 3 |
Plot 4 |
1 |
|
|
|
|
2 |
|
|
|
|
3 |
|
|
|
|
4 |
|
|
|
|
(8 marks)
(c) Why is cowpea included in the crop rotation plan? (1 mark)
(d) State three advantages of a good crop rotation system to the soil. (3 marks)
Observation
Many candidates displayed inadequate knowledge of crop rotation system because
they could not give reasons why the crop rotation plan in Table 1 is regarded as poor
as well as state the advantages of a good crop rotation system to the soil. Furthermore,
some candidates were substituting other crops not listed for the ones listed in the table.
The expected answers include:
3. (a) Reasons why the crop rotation plan in Table 1 is regarded as poor
- Yam and cassava are attacked by the same pests and should not follow each other
- Yam and cassava are attacked by the same diseases and should not follow each other
- Cowpea and maize are shallow rooted crops and should not follow each other
- Yam and cassava are deep rooted crops and should not follow each other
- Yam and cassava have the same nutrient requirement and should not follow each other
(b) Completion of a good crop rotation plan starting with cassava
(c)Reason why cowpea is included in the crop rotation plan
- The bacteria in the root nodules of cowpea fix atmospheric nitrogen in the soil; thus
reduces the need for nitrogenous fertilizers
(d) Advantages of a good crop rotation system to the soil
- Improves soil structure
- Increases soil microbial activities
- Increases soil nitrogen through nitrogen fixation by leguminous crops
- Maintains nutrient balance in the soil
- Improves soil water retention
- Reduces soil erosion
- Reduces leaching of nutrients