Which one of the soil types of India are rendered infertile by the presence of excess iron?
A. Desert Soil
B. Alluvial
C. Black soil
D. Laterite

Hint: Iron is the fourth most abundant element found in the soil. Iron, in small amounts, is essential for healthy plant growth and is considered a vital nutrient. However, too much iron can prevent the absorption of other nutrients that give the soil infertility.

Complete Answer:
Option A: Desert soil is mostly sandy soil found in areas with low rainfall, India has desert soil in Rajasthan. Desert soil accounts for about 4% of the total area, including Punjab and Haryana, the coastal areas of Gujarat, Tamil Nadu and Kerala.
Option B: Alluvial soil is found in places adjacent to river and river valleys. It is the result of deposition of silt and alluvium from the mountains and hills along the rivers. This type of soil is very fertile in nature and best suited for crop cultivation.
Option C: Black soil is a type of soil that is rich in metals such as iron, magnesium and aluminum. This kind of soil is rich in humus and is found in and around volcanic mountains and plateaus.
Option D: Laterite soil is a type of soil that is rich in iron and aluminum and is commonly found in the hot and wet tropical areas. This soil type is made weaker due to the high iron content. This results in very low humus content in the soil. Therefore this soil is not fertile soil and is not suitable for cultivation.
Therefore the correct answer is Option D: Laterite.

Note: Plants, like animals and humans, need a certain amount of iron to survive, but too much iron can have a toxic effect on plants and weaken and eventually kill them. Only ferrous iron particles are absorbed through plants, other types of iron particles do not affect plants.