The correct option is (a) 1 only.
Explanation
Fertilizers are chemical substances, typically inorganic, that are commercially manufactured to supply specific nutrients essential for plant growth. They are distinct from manures, which are natural substances obtained from the decomposition of organic wastes.
Statement-wise Analysis
- Statement 1 is Correct: Fertilizers are commercially produced plant nutrients. They are nutrient-specific and primarily supply nitrogen (N), phosphorus (P), and potassium (K), which are the macronutrients required for plant growth. Examples include Urea, Ammonium Sulphate, and Superphosphate.
- Statement 2 is Incorrect: Fertilizers do not provide any humus or organic matter to the soil. While they provide immediate nutrients, their continuous and excessive use can degrade soil health by killing soil microorganisms and altering soil chemistry (e.g., making it too acidic or alkaline). It is manure, not fertilizer, that replenishes organic matter and improves soil texture.
- Statement 3 is Incorrect: Synthetic fertilizers are not fully biodegradable in the ecological sense. Being water-soluble, excess fertilizers are often washed away by rain or irrigation into water bodies. This leaching leads to water pollution and phenomena such as eutrophication (algal blooms), which depletes oxygen in aquatic ecosystems.
Key Takeaway: Fertilizers are inorganic, nutrient-specific commercial products that do not add humus to the soil and can cause water pollution. In contrast, manures are organic, add humus, improve soil structure, and are environmentally sustainable.