Agronomy L.4

Solar Energy in Agriculture

• 1 hectare of land receives approximately 1.4 × 10^10 kcal/year of solar energy.

• On average, only 0.2% of this energy is converted into plant biomass.

Light in Photosynthesis

• Source of Energy: Light is essential for photosynthesis; plants utilize a specific part of solar radiation.

• Photosynthetically Active Radiation (PAR): Wavelengths between 400-760 nm are utilized.

  • Primarily used wavelengths include violet-blue and orange-red light.

  • Chlorophyll reflects most green light, which is why it appears green.

Efficiency of Solar Energy Conversion

• The conversion efficiency of solar energy into biomass is very low:

  • Natural vegetation: 0.1%

  • Annual crops: 0.2% - 0.5%

  • Forage grasses: 3%

  • Sugar cane: 5%

• Due to this inefficiency, a significant amount of agricultural land is necessary to support the growing populations of humans and livestock.

• The sun also plays a crucial role in warming plants and facilitating the hydrological cycle.

Adjusting Crops to Light Conditions

• To optimize light conditions, several strategies can be implemented:

  • Green Cover: Maintain green cover in fields during the growing season through the use of cover crops.

  • Weed Control: Manage weeds that compete for light with crops.

  • Plant Density: Use optimum plant density per unit area for grain production. Increased density of grain crops is suggested for green fodder/silage (by 10%-15%).

Example of Cropping Strategies

• Producing green forage for grazing animals can involve growing cover crops such as spring barley.

• Illustration of growing periods and management:

  • Spring Barley Growth Timeline:

    • January - March: Unused period, sowing time, and harvest of grain.

    • Growing green forage in the areas during spring.

Temperature's Role in Agriculture

• Temperature has major effects:

  • Accelerates biochemical reactions and influences the distribution of crop species globally.

  • It is a critical factor affecting crop productivity.

  • Supports the activity of soil organisms.

  • In winter, negative temperatures can lead to soil clods freezing, which eases seedbed preparation in the spring.

Winter Crop Resistance to Frost

• Different crops have varying frost resistance:

  • Rye: Survives -30°C

  • Wheat: Survives -21°C

  • Barley: Survives -15°C

  • Rapeseed: Survives -15°C

• Recommended growth stage for frost resistance:

  • All crops listed should be in tillering or similar growth phases during winter.

Importance of Winter Conditions

• Components necessary for winter survival:

  • Living tillering node below soil surface, located at 3-4 cm depth.

  • Snow cover significantly protects plants from severe frost conditions.

Adjusting Crops to Thermal Conditions

• Key strategies for managing thermal conditions include:

  • Select appropriate species and cultivars for regional winter temperatures.

  • Avoid planting frost-sensitive crops in valleys where cold air accumulates.

  • Optimal sowing date and planting depth are crucial.

  • Do not apply nitrogen fertilizers in autumn for winter crops.

  • Plant hedgerows to provide wind protection.

Seasonal Activities in Agriculture

• Understanding what happens in the agricultural fields during autumn:

  • Maize: Harvested in October.

  • Sugar Beet: Harvested from September to November.

  • Sunflower: Harvested in late September.

• Sowing sequences and preparation for crops includes:

  • Fields prepared for winter wheat and winter barley seeding in early fall.