Answer the following questions in about 150 words each: (a) Discuss the response of crop plants to rising temperature and carbon…

Crop Responses to Climate Change

Rising atmospheric carbon dioxide (CO₂) and ambient temperatures exert contrasting yet interacting physiological effects on crops. Elevated CO₂ enhances the photosynthetic rate of C3 crops (such as wheat, rice, and pulses) via the CO₂ fertilization effect by suppressing RuBisCO oxygenation (photorespiration) and improving water-use efficiency through partial stomatal closure. Conversely, C4 crops like maize, sorghum, and pearl millet derive negligible photosynthetic benefit from elevated CO₂ because their internal CO₂-concentrating mechanism operates near saturation at ambient levels. Elevated temperatures largely offset potential CO₂ gains by accelerating crop phenology. This accelerates thermal time accumulation, truncating vegetative and grain-filling durations and causing terminal heat stress in rabi wheat. Extreme temperatures during anthesis cause severe reproductive failure, such as spikelet sterility in rice at temperatures exceeding 35°C due to pollen desiccation. Adapting to these climate dynamics necessitates breeding heat-resilient cultivars and developing microclimate-modifying agronomic practices.

Speciality Corn for Cropping Intensity and Profitability

Incorporating speciality corn—such as sweet corn, baby corn, popcorn, and Quality Protein Maize (QPM)—into existing cropping systems significantly intensifies land use and maximizes farm returns. Baby corn and sweet corn have short growth durations (60–75 days), which allows the inclusion of three to four crops per year in intensive systems (e.g., baby corn–potato–mungbean), thereby increasing cropping intensity beyond 250%. These varieties are suited for intercropping and relay cropping with short-duration grain legumes (such as cowpea and greengram), enhancing land-equivalent ratios and maintaining soil fertility. Economically, speciality corns yield three to four times higher net returns than field maize due to growing urban consumer and processing demand. Popcorn and QPM support value-added industrial supply chains and provide nutritional security. Furthermore, harvesting green baby corn and sweet corn generates green stover for dairy feed, lowering livestock rearing costs and diversifying income streams.

Non-Wood Forest Products (NWFPs) and Local Development

Non-Wood Forest Products (NWFPs) comprise biological goods other than timber harvested from natural forests, plantations, and wooded lands. They encompass bamboo, cane, tendu leaves, natural gums, oleo-resins, lac, wild honey, medicinal and aromatic plants, mushrooms, and tree-borne oilseeds. NWFPs provide an economic safety net for tribal and forest-dwelling communities across central and northeastern India, contributing 20 to 40 percent of their annual household income. They generate sustained rural employment during lean agricultural seasons, with collection, grading, and cleaning predominantly carried out by forest-dependent women. Programs like the Van Dhan Vikas Yojana under TRIFED have organized primary gatherers into Self-Help Groups for local processing and value addition, minimizing intermediary exploitation. By combining Minimum Support Price (MSP) mechanisms with decentralized cottage processing, NWFPs reduce distress migration, promote gender empowerment, and support sustainable forest conservation.

Cultural and Chemical Weed Control in Soybean and Wheat

Effective weed management in soybean and wheat combines cultural techniques with selective chemical applications to limit weed competition.

In soybean (Glycine max), cultural control involves stale seedbed preparation, maintaining a 45 cm × 5 cm plant spacing to accelerate canopy closure, and intercropping with maize or pigeonpea to shade out weeds such as Echinochloa colona and Trianthema portulacastrum. Chemical control includes a pre-emergence application of Pendimethalin at 1.0 kg a.i./ha within 48 hours of sowing, followed by a post-emergence application of Imazethapyr at 75–100 g a.i./ha at 15–20 days after sowing to control both grassy and broad-leaved weeds.

In wheat (Triticum aestivum), cultural measures include closer row spacing (18–20 cm), zero-tillage with surface residue mulching using a Happy Seeder, and crop rotation with mustard or chickpea to break Phalaris minor cycles. Chemically, grassy weeds are controlled post-emergence at 30–35 days after sowing with Sulfosulfuron at 25 g a.i./ha or Clodinafop-propargyl at 60 g a.i./ha. Broadleaf weeds (Chenopodium album, Rumex dentatus) are managed using Metsulfuron-methyl at 4 g a.i./ha or 2,4-D ethyl ester at 0.5 kg a.i./ha.

Genesis and Agricultural Significance of Soil Structure

Soil structure develops through the spatial aggregation of primary particles (sand, silt, clay) into distinct peds. Its genesis is driven by physical, chemical, and biological mechanisms:

• Physical forces: Alternate wetting-drying and freezing-thawing cycles cause differential expansion and shrinkage, creating natural structural fissures.
• Chemical mechanisms: Flocculation of colloidal clays by polyvalent cations (such as Ca²⁺ and Mg²⁺) and subsequent cementation by iron and aluminum sesquioxides stabilize peds.
• Biological processes: Penetrating crop roots exert lateral pressure, while fungal hyphae (secreting glomalin) and soil microbes (producing polysaccharide gums) bind micro-aggregates into water-stable macro-aggregates.
• Tillage: Conservation tillage and organic matter incorporation help maintain these structural bonds.

A well-developed, crumb or granular soil structure is central to crop productivity. It creates a balanced distribution of macropores for root aeration and water drainage, alongside micropores for plant-available water storage. It reduces bulk density, lowers soil resistance to root elongation, improves nutrient diffusion, enhances water infiltration, and resists surface crusting and erosion.