Answer the following questions in about 150 words each: (a) Briefly discuss the principles of agro-ecology. 10 marks (b) What are…

(a) Principles of Agro-ecology

Agro-ecology applies ecological concepts to design and manage sustainable, resilient agricultural systems. As articulated by Miguel Altieri and the FAO’s Ten Elements of Agroecology, its core principles integrate biological and socio-economic dimensions:

Biodiversity and Ecosystem Services: It promotes genetic, species, and structural diversity across temporal and spatial scales—such as polycultures, agroforestry, and crop-livestock integration—to enhance beneficial biological interactions and natural pest regulation.

Nutrient Cycling and Soil Health: It optimizes closed-loop nutrient cycling and biological nitrogen fixation, enhancing soil organic matter and soil microbial activity while minimizing external synthetic inputs.

Energy and Resource Efficiency: It harnesses natural flows, maximizing solar radiation capture, water-use efficiency, and biomass recycling to sustain farm productivity.

Socio-Economic Integration: It fosters co-creation of knowledge, combining traditional agronomic wisdom with modern science, while supporting equitable local food systems, resilience, and circular economies.

In India, agro-ecological principles underpin initiatives like Bharatiya Prakritik Krishi Paddhati, transforming resource-intensive farming into self-sustaining, climate-resilient production landscapes.

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(b) Factors for Low Pulse Productivity and Enhancement Strategies

Pulse cultivation in India faces several structural, biotic, and abiotic constraints:

Abiotic Factors: Over 80% of pulses are grown under rainfed conditions in marginal, degraded soils prone to moisture stress, terminal drought, and extreme heat during pod development.

Biotic Factors: Susceptibility to severe pests such as the pod borer (Helicoverpa armigera) and destructive diseases like vascular wilt (Fusarium oxysporum), sterility mosaic disease, and dry root rot.

Agronomic and Market Constraints: Low seed replacement rates, suboptimal fertilizer application, and inadequate institutional procurement compared to cereals.

Enhancement Strategies: The government has scaled targeted interventions under the National Food Security Mission (NFSM-Pulses) and Cluster Frontline Demonstrations (CFLDs). Breeding programmes have released high-yielding, short-duration, and disease-resistant varieties such as JG-11 (chickpea), Pusa-16 (pigeonpea), and Samrat. Agronomic expansion focuses on utilizing rice fallows in eastern India and promoting intercropping. Market stability is driven through enhanced Minimum Support Price (MSP) operations, buffer stocking via NAFED, and risk mitigation under the Pradhan Mantri Fasal Bima Yojana (PMFBY).

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(c) Objectives and Species for Social Forestry

Social forestry, formally recognized by the National Commission on Agriculture (1976), aims to manage and protect forests and afforest barren lands to aid rural environmental and social development.

Key Objectives: The primary objective is meeting the basic rural demands for fuelwood, fodder, small timber, and non-timber forest produce, thereby reducing anthropogenic pressure on natural forest reserves. It provides rural employment and income generation on degraded community lands, village common lands, and roadsides. Environmentally, it aids in soil conservation, microclimate stabilization, and windbreak creation while fostering community participation through Joint Forest Management.

Suitable Plant Species: Species selection prioritizes fast growth, multi-purpose utility, coppicing ability, and tolerance to stress:

• Acacia nilotica (Babul) – highly adapted to arid, saline soils; provides fuelwood and fodder.
• Dalbergia sissoo (Shisham) – excellent nitrogen-fixing timber and shade tree.
• Eucalyptus tereticornis (Safeda) – fast-growing pole timber and pulpwood for farm forestry.
• Leucaena leucocephala (Subabul) – rich source of palatable green fodder and fuel.
• Azadirachta indica (Neem) – hardy, pest-resistant tree offering medicine, oil, and shade.
• Prosopis cineraria (Khejri) – vital silvopastoral tree for arid zones.

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(d) Cultural Methods of Weed Control

Cultural weed management involves manipulating cropping practices to give the crop an ecological and competitive advantage over weeds, minimizing reliance on chemical herbicides.

Preventive and Field Hygiene Practices: Utilizing certified, weed-free seed lots, cleaning farm machinery between plots, and managing irrigation channels prevent weed seed dissemination.

Tillage and Land Preparation: Summer deep ploughing exposes underground propagules of perennial weeds to solar desiccation. The stale seedbed technique encourages weed emergence prior to final shallow tillage and sowing. In lowland rice, continuous shallow flooding suppresses broadleaf and grassy weeds.

Crop Husbandry and Spatial Manipulation: Adjusting planting dates to avoid peaks of weed emergence, employing higher seed rates, and narrowing row spacing achieve rapid canopy closure, depriving weeds of light.

Biological Suppression and Rotation: Diversified crop rotations break weed life cycles adapted to mono-cropping. Intercropping with competitive smother crops (e.g., cowpea, green gram) and utilizing allelopathic crops (e.g., sorghum, rye) naturally suppress weed germination and establishment.

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(e) Nitrification Steps, Micro-organisms, and Importance

Nitrification is the two-step biological oxidation of reduced nitrogen (ammonium) to oxidized nitrogen (nitrate) carried out by specialized chemoautotrophic aerobic micro-organisms:

Step 1: Ammonia Oxidation Ammonium (NH₄⁺) is converted into nitrite (NO₂⁻): 2NH₄⁺ + 3O₂ → 2NO₂⁻ + 4H⁺ + 2H_2O + Energy This conversion is primarily mediated by obligate autotrophs such as Nitrosomonas, Nitrosococcus, and Nitrosospira.

Step 2: Nitrite Oxidation Nitrite (NO₂⁻), which is toxic to plants, is oxidized into nitrate (NO₃⁻): 2NO₂⁻ + O₂ → 2NO₃⁻ + Energy This reaction is facilitated by nitrifying bacteria such as Nitrobacter and Nitrococcus.

Agronomic and Soil Importance: Nitrification transforms immobile ammonium into nitrate (NO₃⁻), the predominant form of inorganic nitrogen absorbed by most non-wetland upland crops. However, nitrate is highly mobile and prone to leaching into groundwater or loss via denitrification in anaerobic conditions. The reaction generates H⁺ ions, contributing over time to soil acidification. Managing nitrification rates using nitrification inhibitors (e.g., Neem-coated urea) is critical for enhancing nitrogen-use efficiency in crop production.