Factors Affecting Crop Production

Internal factors are classified as genetic or hereditary
External factors are classified as environmental
These include climatic, edaphic, biotic, physiographic, and socio-economic factors.

Increased yield and desirable characters are related to the genetic makeup of the plant.
Key areas for improvement through genetics and plant breeding include:
- High yields under given environmental conditions
- Early/late maturity
- Resistance to lodging
- Tolerance to drought, floods, and salinity
- Tolerance to insects and diseases
- Chemical composition of grains (high oil content, increased protein, etc.)
- Quality of grains (fineness, coarseness, etc.)
- Quality of straw (sweetness, juiciness, etc.)

The life cycle of a crop is intimately connected to environmental factors.
Environmental factors interact with one another. 
Climatic factors affect crop plants. These include precipitation, temperature, atmospheric humidity, solar radiation, and wind velocity.

Plants experience injury from very low temperatures (cold injury).
- Chilling injury: Plants growing in hot climates can be harmed by exposure to low temperatures. Common in sugarcane, sorghum and maize.
- Freezing injury: Ice crystals form inside plant cells and the protoplasm of the cell dehydrates, potentially killing cells. Typical in potato, tea in cold areas.
- Suffocation: Ice or snow cover of ground prevents oxygen diffusion, causing cell harm.
- Heaving: Plant roots lift from the ground with frost causing damage.
High temperature effects: Cells are killed at temperatures between 50-60°C (thermal death point), with different points for various plants. This effect is related to higher temperatures hindering growth, causing starvation and causing leaf drop, ultimately potentially killing the plant.

Plants grow within temperature limits, with optimal limits for each species and variety, in specific stages, and functions.
Biochemical processes in photosynthesis are affected by temperature. Without proper light levels, temperature doesn't substantially affect photosynthesis. Higher temperatures generally speed up growth.
Excessive temperatures, in the absence of enough water, can harm the plant.

Latitude: Maximum and minimum monthly temperatures fluctuate with the location's latitude, relevant to the seasons.
Altitude: As the altitude increases, surface air temperature decreases, owing to decreased air density affecting absorption capacity.
Distribution of land and water: Land temperatures change more dramatically than water temperatures; ocean currents transfer heat from warmer to cooler areas.

Water vapor in the air, or humidity, affects several aspects of plant growth, such as transpiration rates, which are crucial to the plant.
Humidity is relative, with higher percentages related to higher water vapor levels in the air relative to the saturation point, which is reliant on the temperature.
There is a direct relation among humidity, temperature and rainfall in determining suitability for vegetative growth.

Red and blue light are most essential for plant growth.
Shorter wavelengths of light may damage bacteria, whereas other light types encourage flowering.

The rate of photosynthesis and other processes involved in photosynthesis are affected by relative light intensity since light affects the rate of transpiration, regulating the opening and closure of stomata.
The low intensity of light and high light intensity leads to reduced photosynthesis; this is crucial to the plant's processes (such as respiration) because of the high energy loss in high intensity light causing photooxidation.
Plants are sorted into classifications which describe their tolerance of light levels. Sciophytes (shade-loving plants) thrive better in low-light conditions, while Heliophytes (sun-loving plants) perform best under full sunlight.

Soil is comprised of minerals, water, air, and organic matter.
The mineral composition varies dependent upon the origin and weathering of the rock formation.

Important aspects of soil include the shape, arrangement of soil particles and the relative proportion or distribution of space for air, water and solid particles.
Various factors determine the structure, including the original parent material, biological activity, minerals and the presence of organic matter.

Soil texture refers to the proportion of sand, silt, and clay in the soil. 
Soil texture classes are based on the specific percentages of sand, silt, and clay found in a sample.

Hygroscopic water: strongly absorbed, unavailable. The water molecules are attracted to the soil particles in the soil.
Capillary water: held by cohesive forces, readily available to plants. The water molecules are cohesive and attracted each other.
Gravitational water: Moves freely through the soil and is not often usable to plants. It is the water that moves under the influence of gravity.