The correct option is (a) 1 only.
Explanation
Continuous cultivation of crops can deplete soil nutrients, necessitating methods to replenish soil fertility. These methods include natural practices like field fallowing and crop rotation, as well as the application of external supplements such as manures and fertilizers.
Statement-wise Analysis
- Statement 1 is Correct: Leaving a field fallow (uncultivated) for one or more seasons allows the soil to naturally regain nutrients. During this period, the decomposition of dead plants, animals, and other organic matter by soil microbes replenishes the nutrient content of the soil.
- Statement 2 is Incorrect: Manuring refers to the addition of organic matter (manure) obtained from the decomposition of plant or animal wastes. In contrast, the addition of chemical substances produced in factories is referred to as the application of fertilizers (e.g., Urea, Ammonium Sulphate).
- Statement 3 is Incorrect: Crop rotation is the practice of growing different crops alternately on the same land. This method is primarily used to replenish the soil with nitrogen, not deplete it. For example, leguminous crops are often rotated with non-leguminous crops because Rhizobium bacteria in the root nodules of legumes fix atmospheric nitrogen, thereby enriching the soil.
Key Takeaway
Fallowing and crop rotation are natural methods of soil nutrient replenishment, whereas manure is an organic supplement. Fertilizers are inorganic chemical substances produced industrially.