Cambridge Secondary (7-9). Stage 9. Science. Learner's Book - Unit 1: Photosynthesis and the carbon cycle - Question 94

A farmer carried out an experiment to find out how adding different quantities of nitrate-containing fertiliser affected the quantity of grain that she harvested from her wheat crop. The graph shows the results.

Name one mineral, other than nitrate, that plants need for healthy growth. Explain why they need this mineral.