Environmental Effects of Agriculture: Climate and Vegetation

Atmospheric Gases for Plant Growth

• CO2 is essential for photosynthesis, while O2 is vital for respiration and photosynthesis.
• Nitrogen is a significant plant nutrient, fixed in the soil by lightning, rainfall, and N-fixing microbes in pulse crops.
• Certain gases like SO2, CO, CH4, released to the atmosphere, are toxic to plants.
• Nitrogen is the most abundant gas in the atmosphere (78%), followed by oxygen (21%), and inert gas argon (0.96%).

Edaphic (Soil) Factor

• Human activities alter or influence the natural processes favorable for plant growth and development.
• Soil factors, including soil water, mineral nutrients, soil temperature, aeration, soil pH, organic matter, and soil biota, are the components of edaphic.

Soil Moisture

• The moisture range between field capacity and permanent wilting point is available to plants.
• Soil moisture affects the chemical and biological activities of soil, including mineralization, nutrient availability, and mobility.

Soil Texture

• Clay soil holds more water than sandy soil, and is essential for nutrient availability and mobility.
• Soil texture affects water holding capacity, with clay > silt > sand.

Soil Air

• Aeration of soil is essential for the absorption of water by roots, and O2 is required for respiration of roots, microbes, and nutrient mineralization.
• Different crops require varying levels of O2 in soil air, such as potato, tobacco, and legumes needing higher O2, while rice requires a low level of O2.

Soil Temperature

• Soil temperature influences the rate of absorption of water and solutes (nutrients), affects the germination of seeds, and growth rate.
• Cold soils are not conducive to the rapid growth of most agricultural crops.

Soil Minerals

• Soil minerals are derived from the weathering of rocks, and are sources of plant nutrients, such as Ca, Mg, S, Mn, Fe, and K.
• Soil pH affects the availability of plant nutrients, with acidic soil (pH < 7.0) making Fe and Al soluble, and interfering with the availability of other plant nutrients.

Soil Organic Matter

• Soil organic matter supplies all major, minor, and micronutrients to crops, improves soil texture, and increases soil water retention.
• Organic acids released during decomposition of organic matter enable mineralization.

Soil Organisms

• Soil organisms are essential in decomposition and nutrient cycling, with microbes fixing N to plant-usable form through symbiotic or non-symbiotic association.

Environmental Effects of Agriculture

• Climate factors, including precipitation, temperature, relative humidity, solar radiation, and wind velocity, affect plant growth and development.

Climate

• Precipitation includes all water that falls from the atmosphere, with rainfall being one of the most important factors influencing vegetation.
• Distribution of rainfall is more important than total rainfall for having a longer growing period, especially in drylands.
• Temperature influences crop plants and vegetation, with increasing global temperatures resulting in more hot and fewer cold extremes.
• Relative humidity affects the amount of moisture present in the air, with 40-60% being suitable for most crop plants.

Biotic Factor

• Plants compete for nutrients, and soil fauna and flora help with nutrient cycling, while insects are mainly involved in pollination.

Physiography

• Surface features of the land, such as topography, altitude, or land cover, affect plant growth and development.

Genetic Factor

• Genetically modified organisms (GMOs) can provide salinity and drought tolerance, resistance to lodging, and improved chemical composition of grains.

Economic Factor

• Prevailing farm conditions, availability and cost of planting materials, pest and disease resistance, availability of labor, cost of farming system, and security, as well as available technology, marketability, and profitability, all influence agricultural practices.