On the pH scale, what number is neutral?
Answer7
A pH of 7 is neutral; lower values are acidic and higher values are alkaline.
Nature · Facts & stats
Fertility facts & stats
7 fact-checked facts about soil fertility, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which burrowing animals mix soil and leave nutrient-rich castings behind?
AnswerEarthworms
Earthworms tunnel through soil, improving drainage and air flow, and their castings are rich in nutrients.
Going deeper
In N-P-K, the K stands for which nutrient?
AnswerPotassium
K is the chemical symbol for potassium, from its Latin name 'kalium'.
The 'Fertile Crescent', where early farming began, is in which region?
AnswerThe Middle East
The Fertile Crescent arcs through the Middle East, including river valleys where early agriculture developed.
Roughly what percentage of Earth's air is nitrogen?
Answer78%
Air is about 78% nitrogen and 21% oxygen, yet most plants cannot use nitrogen gas directly.
Expert level
The Haber-Bosch process, key to making modern fertilizer, produces which compound?
AnswerAmmonia
Haber-Bosch combines nitrogen from the air with hydrogen to make ammonia, used to produce nitrogen fertilizers.
Gardeners add lime (ground limestone) to soil mainly to do what?
AnswerMake acidic soil less acidic
Lime is mostly calcium carbonate, which neutralizes acidity and raises soil pH.
Know these cold?Today's round is five questions like these, 20 seconds each. Your streak and level follow you to every arena.Play today's round