Certified Crop Advisor Practice Exam

If a manure contains 1.9% phosphorus on a dry basis and is 60% solids, what is the phosphorus concentration on a wet basis?

1. 0.9%

2. 1.1%

3. 1.5%

4. 2.0%

The correct answer is: 1.1%

To determine the phosphorus concentration on a wet basis from the manure sample, it's important first to understand the values given. The manure contains 1.9% phosphorus on a dry basis, meaning that in every 100 grams of the dry manure, there are 1.9 grams of phosphorus. Since the manure is 60% solids, this means that in a total weight of wet manure, 60% of it is solid material, while 40% is liquid. To find the total wet weight of the sample, consider 100 grams of manure as a reference. In that amount, there would be 60 grams of solids and 40 grams of liquid. The phosphorus in the solids would still be 1.9% of the dry matter. Calculating the wet phosphorus concentration involves determining how much phosphorus is present in the wet sample: - The phosphorus in the dry matter is 1.9 grams (from the 1.9%). - Since the total weight of the wet sample is 100 grams, the concentration of phosphorus on a wet basis would be calculated as: \[ \text{Wet Phosphorus Concentration} = \frac{\text{Phosphorus in solids}}{\text{Total wet weight