Waec Model Questions Vol1 2023 Agricultural Science Question 2

Practice practical question 2 from the 2023 Waec Model Questions Vol1 Agricultural Science examination. This question covers Soil nutrient analysis, Spectrophotometry, Nutrient management, Error analysis .

Waec Model Questions Vol1 2023 Agricultural Science Practical
Topics: Soil nutrient analysis Spectrophotometry Nutrient management Error analysis
Question 2 WAEC_MODEL_QUESTIONS_VOL1 • 2023 • AGRICULTURAL_SCIENCE • practical

A soil scientist is determining the nitrate (NO₃⁻) and phosphate (PO₄³⁻) contents of a field soil intended for maize production. A 50 g air‑dried soil sample is extracted with 250 mL of distilled water. The extract is filtered and its absorbance is measured with a calibrated spectrophotometer. - Absorbance for nitrate = 0.45 (λ = 220 nm) - Absorbance for phosphate = 0.30 (λ = 880 nm) The calibration equations supplied by the laboratory are: - Nitrate: Concentration (mg L⁻¹) = 20 × Absorbance - Phosphate: Concentration (mg L⁻¹) = 15 × Absorbance Using the data above, answer the following questions:

Question Parts

( a )
Calculate the concentration of nitrate and phosphate in the soil sample expressed as mg kg⁻¹.
( b )
Determine the soil N : P ratio on a mg kg⁻¹ basis.
( c )
Given that the recommended N : P ratio for optimum maize growth is 3 : 1, state which nutrient is limiting in this soil and justify your answer.
( d )
List two agronomic measures that could be adopted to correct the identified nutrient limitation.
( e )
Identify one possible source of error in the analytical procedure and suggest a way to minimise it.

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About This Question

This is Waec Model Questions Vol1 2023 Agricultural Science Question 2. It is one of the practical questions from the 2023 Waec Model Questions Vol1 Agricultural Science examination.

The question covers Soil nutrient analysis, Spectrophotometry, Nutrient management, Error analysis .

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