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Describe laboratory or field experiments for any two of the following: (a) To investigate the effect of structure on total pore space in a soil - Leaving Cert Agricultural Science - Question 4 - 2013
Question 4
Describe laboratory or field experiments for any two of the following: (a) To investigate the effect of structure on total pore space in a soil. (b) To grow a cult... show full transcript
Worked Solution & Example Answer:Describe laboratory or field experiments for any two of the following: (a) To investigate the effect of structure on total pore space in a soil - Leaving Cert Agricultural Science - Question 4 - 2013
Step 1
(a) To investigate the effect of structure on total pore space in a soil.
Answer
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Sample Collection: Collect two samples of dry soil from different locations or two named soil types to compare.
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Preparation: Crush one soil sample to pass through a graduated cylinder, measuring its bulk density. For the other sample, leave it in its original form.
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Add Water: Measure the same amount or mass of water for each sample. Add this water to each of the soil samples in their respective cylinders.
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Observation: Allow both samples to settle for one hour.
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Record Results: After settling, record the total volume of water in the cylinder and calculate the percentage of pore space in each type by using the formula:
ext{Pore Space ( ext{V})} = rac{ ext{Total Volume of Water (mL)}}{ ext{Volume of Soil Sample (mL)} + ext{Total Volume of Water (mL)}} imes 100
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Conclusion: Analyze which structure has a greater pore space and discuss the implications of soil structure on drainage and aeration.
Step 2
(b) To grow a culture of bacteria from the root nodules of clover.
Answer
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Sample Preparation: Collect root nodules from clover plants, ensuring they are fresh and healthy.
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Cleaning: Rinse the root nodules to remove soil particles, then thoroughly disinfect them using an appropriate sterilizing solution.
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Crushing Nodes: Once clean, crush the root nodules to release the bacteria contained within them.
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Transfer to Medium: Use an sterilized inoculating loop to transfer the crushed root tissue to a prepared Petri dish containing nutrient agar. This agar should be optimal for the growth of the desired bacterial culture.
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Incubation: Incubate the Petri dish at room temperature (ideally between 18-30°C) for a period of 2-7 days, allowing the bacteria to grow.
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Observation: After incubation, observe the colonies formed and specifically look for colonies that represent the bacteria typically associated with Rhizobium. Document the growth characteristics.