Question

Critical limit approach was developed by _______

• A. Waugh and Fitts
• B. Cate and Nelson
• C. Collwell
• D. Truog

Hint:

The Cate-Nelson graphical and statistical methods are standard procedures used to determine the critical limit of nutrients in soils, dividing soil test results into responsive and non-responsive categories.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Soil test calibration translates chemical soil test values into crop yield responses.
The "critical limit" is the nutrient concentration in soil or plant tissue below which a crop is likely to respond to fertilizer application, and above which a response is unlikely.

Step 2: Detailed Explanation:
The critical limit approach for soil test calibration was developed by Robert B. Cate Jr. and Larry A. Nelson in 1965.
They introduced two widely used methods to determine these threshold values:
1. Cate-Nelson Graphical Method: This method uses a scatter plot of soil test nutrient values (x-axis) against relative crop yields (y-axis).
A transparent overlay with two intersecting lines divides the plot into four quadrants to maximize the data points in the positive-response (low soil test, low yield) and no-response (high soil test, high yield) quadrants, minimizing the error points.
The vertical line represents the critical limit of the nutrient in the soil.
2. Cate-Nelson Statistical Method: This is an iterative statistical approach that uses analysis of variance (ANOVA) or sum of squares to find the split point that maximizes the coefficient of determination ($R^2$) between the two groups.
This approach is widely used in soil testing laboratories to categorize soils into "low" and "high" nutrient classes for fertilizer recommendations.

Step 3: Final Answer:
The critical limit approach was developed by Cate and Nelson, which corresponds to Option (B).