Question

Soil fertility is reduced by
A. Crop rotation
B. Nitrogen fixing bacteria
C. Decaying organic matter
D. Intensive agriculture

Answer 1

Hint: Soil fertility is the ability of the soil to provide a proper habitat and supply essential nutrients to the plants to result in sustained and high yield of crops. Soil fertility is lost if the nutrients of the soil are used extensively without being replaced.

Complete answer: Soil fertility is defined as the capacity of the soil to help the plants grow in such a way that results in sustainable and high yield of crops. Soil fertility is affected by certain conditions like depth of soil, drainage of the soil, presence of organic matters, pH of the soil, presence of nutrients and microorganisms. Lack of one or more of these properties can lead to loss of fertility or reduced fertility of the soil.
The main reason for reduction of soil fertility is attributed to Intensive agriculture systems. Intensive agriculture or Industrial agriculture is the most common method of crop production at present. It is based on high input and output ratios. This form of agriculture came into being during the period of Industrial revolution when the use of agricultural techniques highly improved. Identification of the main nutrient providing substances of the soil like Nitrogen, Phosphorus and Potassium led to the development of artificial fertilizers increased the crop yield by 2 to 3 folds.
Intensive agriculture has led to multiple cropping, that is growing two or more crops in a season. This practice causes the loss of organic matter from soil. Organic matter is a key source of nitrogen and potassium in organic forms. These two substances are of utmost importance to plant growth. Decaying organic matter is a good source of ammonia in the soil which is later converted to nitrate and taken up by plants.
Nitrogen can be used by the plants only in the form of nitrates. The gaseous form of nitrogen can be converted to nitrate either by lightning or by nitrogen fixing bacteria present in root nodules of leguminous plants. Therefore, presence of Nitrogen fixing bacteria can improve soil fertility.
Crop rotation is the process of growing different types of crops throughout the year. The crops chosen for a particular region depend on how they contribute to the organic matter in the soil, help in pest control, regulates nutrients, controls soil erosion and influences the food web and ecosystem of the surroundings.

Hence, from the above discussion it can be concluded that the correct option is (D).

Note: Soil fertility is the ability of the soil to yield high quality crops in a sustainable manner. Soil fertility is an important factor in agriculture because it helps in growth of plants by providing proper nutrients. Reduction or loss of soil fertility occurs when uptake of nutrients is more than the rate of replacing them. Soil fertility can be increased by crop rotation, using biofertilizers that contain phosphorus and potassium, growing leguminous plants that harbor nitrogen fixing bacteria.