Which of the following choices shows a fertilizer mass, a fertilizer grade, and an area that, when uniformly applied, delivers approximately 1.5 lbs of K per 1000 ft² (M)?

a) 309 lbs, 0-0-60, 2.2 acres of turfgrass
b) 320 lbs, 0-0-50, 1.75 acres of turfgrass
c) 520 lbs, 0-0-22, 1.75 acres of turfgrass
d) 312 lbs, 13-0-44, 1.75 acres of turfgrass
e) 400 lbs, 0-0-50, 1.75 acres of turfgrass

To find the correct fertilizer application, calculate the total mass of potassium based on the fertilizer grade and area, then compare it to the desired per thousand square feet rate of 1.5 lbs of K. Fertilizer grade, such as '0-0-60', indicates the proportion of potassium in the product.

Explanation:

To determine which fertilizer application will deliver approximately 1.5 lbs of K (potassium) per 1000 square feet, we need to calculate the amount of potassium in the given mass of fertilizer, considering the fertilizer's grade and the area it covers. Fertilizer grades are represented by a three-number series such as '0-0-50', where the last number represents the percentage of potassium K2O in the fertilizer. To find the total amount of potassium, we multiply the mass of the fertilizer by the potassium percentage (converted to a decimal).

For option a), with a 0-0-60 grade fertilizer, the calculation would be 309 lbs imes 0.60 = 185.4 lbs of K. The area covered is 2.2 acres, which is 2.2 imes 43,560 square feet per acre = 95,832 square feet. Then, we can calculate the amount of K per 1000 sq ft by dividing the total K by the total area in thousands of square feet: 185.4 lbs / 95.832 (x1000) \\[approx\\] 1.93 lbs of K per 1000 sq ft.

Thus, going through each option with a similar approach, we can see which combination meets the requirement of delivering approximately 1.5 lbs of K per 1000 sq ft.