Landscaping License Practice Test

In cooler weather, which fertilizer acts the quickest?

1. Urea

2. Ammonium sulfate

3. Compost

4. Triple super phosphate

The correct answer is: Ammonium sulfate

Ammonium sulfate is known for its effectiveness in cooler weather due to its solubility and the rapid availability of nitrogen it provides to plants. This fertilizer contains both nitrogen in a readily usable form and sulfur, which can enhance plant growth and nutrient uptake. In cooler temperatures, the biological activity in the soil generally slows down, but ammonium sulfate is less dependent on microbial activity for the release of nitrogen compared to other fertilizers. Urea, while a common nitrogen source, requires conversion to ammonium by soil micro-organisms, which happens more slowly in cool conditions. Compost, on the other hand, releases nutrients gradually as it continues to decompose, making it less effective for immediate nutrient needs during colder weather. Triple super phosphate primarily provides phosphorus over a longer term and doesn't react as quickly, especially in cooler soils. Thus, in the context of quick action in cooler weather, ammonium sulfate is the best choice because it provides readily available nutrients to plants when they need them most, supporting their growth despite the slower soil microbial activity.