| Date | November 2019 | Marks available | 1 | Reference code | 19N.3.HL.TZ0.17 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Identify | Question number | 17 | Adapted from | N/A |
Question
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.
Markscheme
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 ✔
