The figure below shows the effects of soil pH on nutrient availability. Thicker bars indicate higher nutrient availability.

[Source: diagram drawn from Emil Truog, 1947, The Liming of Soils, USDA Yearbook of Agriculture 1943–1947,
and N.A. Pettinger, 1935, A Useful Chart for Teaching the Relation of Soil Reaction to the Availability of Plant
Nutrients to Crops, Virginia Cooperative Extension, Virginia Tech, and Virginia State University]

Identify which element is more available in strongly acid conditions.

Outline the roles of Rhizobium bacteria in the nitrogen cycle.

Describe the major characteristics of a eutrophic lake.

iron/Fe ✔

a. «Rhizobium» forms mutualistic/symbiotic relationship with roots/legumes ✔

b. «Rhizobium» fixes «atmospheric» nitrogen ✔

c. converts it into ammonia «to be used by plants» ✔

a. normally shallow ✔

b. low water visibility
OR
high levels of nutrients/phosphates/potassium
OR
low oxygen concentration
OR
high BOD ✔

c. high net primary productivity
OR
algal bloom
OR
low biodiversity ✔