MP Board · Class 9 · Science · Improvement in Food ResourcesSolve the numerical problem in Part A and answer the theoretical question in Part B regarding Sustainable Nutrient Management and Organic Farming: Part A (Numerical):\nA farmer cultivates a leguminous chickpea (Cicer arietinum) crop on a $5\text{-hectare}$ agricultural field. Biological nitrogen fixation by root-nodule Rhizobium bacteria adds an average of $92\text{ kg}$ of atmospheric Nitrogen per hectare into the soil. Calculate the total mass of Nitrogen (in kg) fixed biologically across the entire $5\text{-hectare}$ field. Commercial Urea fertilizer $\text{CO(NH}2)2$ contains $46\%$ Nitrogen by mass. Calculate the total mass of Urea (in kg) that the farmer saves by utilizing this natural biological nitrogen fixation. Part B (Theoretical):\nWrite a detailed note on Organic Farming addressing the following points: Define Organic Farming and state its main philosophy. Describe the roles of Bio-fertilizers, Bio-pesticides, Green Manure, and Vermicompost in organic agriculture. State three key long-term ecological advantages of organic farming over conventional chemical farming.

Part A: Numerical Solution

1. Total Biological Nitrogen Fixed:

• Area of field = $5\text{ hectares}$
• Nitrogen fixed per hectare = $92\text{ kg/ha}$
• $\text{Total Nitrogen fixed} = 5\text{ ha} \times 92\text{ kg/ha} = 460\text{ kg}$

2. Mass of Urea Saved:

• Urea contains $46%$ Nitrogen by mass.
• This means $46\text{ kg}$ of Nitrogen is supplied by $100\text{ kg}$ of Urea.
• Therefore, mass of Urea equivalent to $1\text{ kg}$ Nitrogen = $\frac{100}{46}\text{ kg}$
• Mass of Urea required for $460\text{ kg}$ Nitrogen: $$\text{Mass of Urea} = 460 \times \left(\frac{100}{46}\right)$$ $$\text{Mass of Urea} = 10 \times 100 = 1000\text{ kg}$$
• Conclusion: The biological nitrogen fixation saves $1,000\text{ kg}$ ($1\text{ tonne}$) of commercial Urea fertilizer.

Part B: Theoretical Answer

1. Definition and Philosophy of Organic Farming\nOrganic farming is a holistic farming system that minimizes or completely avoids the use of synthetic chemical inputs (pesticides, synthetic fertilisers, weedicides, growth hormones) and relies on biological inputs, crop rotations, organic wastes, and natural pest control mechanisms to maintain soil health and food safety.

2. Key Biological Inputs in Organic Farming

• Bio-fertilizers: Organisms like Rhizobium, Azotobacter, and Blue-Green Algae (BGA) that enrich soil nutrient availability by fixing atmospheric nitrogen or solubilizing phosphorus naturally.
• Bio-pesticides: Plant-based extracts (such as Neem leaves/turmeric solutions) or biological agents (such as Bacillus thuringiensis / Trichoderma) used to control pests, pathogens, and fungi without toxic chemical residues.
• Green Manure: Fast-growing leguminous crops (e.g., Sunn hemp, Sesbania/Dhaincha) grown and ploughed back into the soil before sowing main crops to enrich soil organic matter and Nitrogen content.
• Vermicompost: High-grade organic manure produced by the degradation of crop residues and organic waste using earthworms (Eisenia fetida). It improves soil aeration, water retention, and microbial activity.

3. Ecological Advantages Over Chemical Farming

• Preservation of Soil Micro-ecology: Protects beneficial soil organisms (earthworms, mycorrhizae) destroyed by toxic agrochemicals.
• Prevention of Environmental Pollution: Eliminates chemical runoff into groundwater and water bodies, preventing biomagnification and eutrophication.
• Sustainable Soil Fertility: Enhances long-term soil structure, organic carbon content, and water-holding capacity.