CCA Nutrient Management Planning 2 — Questions and Answers
Question 1: A soil test reports 45 ppm Bray P1 phosphorus. Using the Mehlich-3 extraction, what conversion factor is typically applied to compare results between the two methods?
- Divide Mehlich-3 by 1.1 to get Bray P1 equivalent
- Multiply Bray P1 by 1.1 to estimate Mehlich-3 (Correct answer)
- The two methods are directly interchangeable with no conversion
- Multiply Bray P1 by 2.0 to estimate Mehlich-3
Correct answer: Multiply Bray P1 by 1.1 to estimate Mehlich-3
Mehlich-3 P values are typically about 10% higher than Bray P1, so multiplying Bray P1 by approximately 1.1 gives a rough Mehlich-3 equivalent.
Question 2: Which of the following best describes the 'credit' given to legume nitrogen in a nutrient management plan when a non-legume crop follows in rotation?
- The full amount of N fixed by the legume is credited to the next crop
- A portion of legume-fixed N is credited based on legume stand quality and yield (Correct answer)
- No nitrogen credit is given because fixed N is entirely consumed by the legume
- Legume N credit is only applicable in organic production systems
Correct answer: A portion of legume-fixed N is credited based on legume stand quality and yield
Previous crop N credits are based on legume stand quality, yield, and decomposition rates, typically ranging from 40–200 lbs N/ac depending on crop type.
Question 3: A CCA is developing a nutrient management plan for a field with a CEC of 8 meq/100g. Which micronutrient deficiency is MOST likely to occur in this sandy, low-CEC soil?
- Molybdenum
- Boron
- Manganese
- Zinc (Correct answer)
Correct answer: Zinc
Zinc deficiency is most common in coarse-textured, low-organic-matter soils with low CEC, especially in the upper Midwest and Pacific Northwest.
Question 4: Under the 4R nutrient stewardship framework, 'Right Source' refers to:
- Applying nutrients from a certified supplier only
- Matching the fertilizer form and grade to crop and soil needs (Correct answer)
- Using only organic nutrient sources to minimize environmental impact
- Selecting the source with the lowest cost per unit of nutrient
Correct answer: Matching the fertilizer form and grade to crop and soil needs
Right Source means selecting the correct fertilizer product—form, grade, and nutrient ratio—that matches crop requirements and soil conditions.
Question 5: When calculating a phosphorus application rate using the sufficiency approach, the primary goal is to:
- Build soil P levels to the highest agronomic optimum over multiple years
- Apply P to achieve a specific soil test level considered adequate for maximum yield (Correct answer)
- Replace all P removed by the harvested crop in a single growing season
- Eliminate P applications when soil tests exceed the critical level
Correct answer: Apply P to achieve a specific soil test level considered adequate for maximum yield
The sufficiency approach targets maintaining soil test P at a level sufficient for maximum economic yield rather than building reserves above that threshold.
Question 6: A farmer applies 200 lbs/ac of 46-0-0 urea to a corn field one week before a heavy rainfall event. Which nitrogen loss pathway is the PRIMARY concern?
- Denitrification of ammonium in saturated soils
- Surface runoff of urea before hydrolysis can occur
- Leaching of nitrate formed rapidly after hydrolysis and nitrification
- Volatilization of ammonia from soil surface before incorporation (Correct answer)
Correct answer: Volatilization of ammonia from soil surface before incorporation
Surface-applied urea is highly susceptible to ammonia volatilization once hydrolyzed by urease, especially on high-pH or high-organic-matter soils if not incorporated by rainfall (>0.5 inch) or tillage.
Question 7: Which soil pH range generally maximizes the availability of most macronutrients and micronutrients for crops grown in mineral soils?
- 5.0–5.5
- 5.5–6.0
- 6.0–7.0 (Correct answer)
- 7.0–7.5
Correct answer: 6.0–7.0
The pH range of 6.0–7.0 optimizes availability of N, P, K, S, Ca, Mg, and most micronutrients while minimizing toxic element availability.
CCA Nutrient Management Planning 2
A soil test reports 45 ppm Bray P1 phosphorus.
Using the Mehlich-3 extraction, what conversion factor is typically applied to compare results between the two methods?