Agricultural Science 3 Nov/Dec. 2013

Agricultural Science Paper 3, Nov/Dec2013

Questions:		1	2	3	4		Main

General Comments
Weakness/Remedies
Strength

Question 3

A group of students investigated the effect of urea fertilizer on the growth of Amaranthus sp. The diagram below shows how two plots of Amaranthus sp. were treated by the students.

Urea fertilizer solution sprayed on to Amarantus sp. On Wednesday of each week

Plain water sprayed on to Amaranthussp on Wednesday of each week

The students harvested all Amaranthus sp. over 5 centimeters high from each week, for six weeks. The Amaranthus sp. Were dried in an oven at 105oC and weighed. The drying and weighing were repeated until a constant mass for each sample was obtained.
The results are as shown below.

	*Dry mass of harvested* *Amaranthus sp. In grains.*
*Week*	*Plot A*	*Plot B*
1st	15.3	16.1
2nd	17.8	15.2
3rd	23.0	14.7
4th	24.7	13.1
5th	25.5	12.7
6th	25.1	11.4
Total	131.4
Mean dry mass per week	21.9

Calculate the mean dry mass per week for Plot B .[1 mark]
State one conclusion each about the effects of urea and plain water on the

growth of Amaranthus sp. [ 4 marks]

3.Give one reason for including Plot B in the investigation. [ 2 marks]

4.State two benefits of inorganic fertilizers in crop production. [ 2 marks]

5.Mention two ways in which water is important to crops [ 2 marks ]

Complete the table below.

Deficiency symptoms of nutrients in crops	Deficient crop nutrient
(i) Purple colouration of leaves
(ii)	Nitrogen
(iii) Marginal browning of leaves and scorching leaves
(iv) Bleaching of young leaves

[ 4 marks ]

_____________________________________________________________________________________________________

OBSERVATION

This question was poorly attempted by the candidates. In 3(a), most of the candidates were able to calculate the mean dry mass per week for plot B. But in 3(b-c), majority of the candidates were could neither state the conclusion about the effects of urea and plain water on the growth of Amaranthus sp. nor give a reason for including plot B in the investigation.
However, in 3 (d-e), most of the candidates were able to state the benefits of inorganic fertilizers in crop production and mention the ways in which water is important to crops. But in 3(f), majority of the candidates were unable to complete the table.

The expected answers include:
(b)     Conclusion about the effects of urea fertilizer and plain water on Amaranthus sp.
         Urea
          There was continuous increase in the dry mass of Amaranthus sp. every week
          suggesting that

Urea fertilizer promotes the growth of Amaranthus sp.

        Plain water
There was a steady decrease in the dry mass of Amaranthus sp every week, suggesting that plain water does not promote the growth of Amaranthus sp as the urea fertilizer did.
(c)    Reason for including plot B in the investigation
        -   To serve as a control/control experiment.
(f)   Completion of the table

Deficiency symptoms of nutrient in crops	Deficient crop nutrient
Purple colouration in Leaves	Phosphorus
Yellowing of leaves and stunted growth	Nitrogen
Marginal browning of leaves and scorching leaves	Potassium
Bleaching of young leaves	Zinc