Climate

Microclimate: Microclimate refers to the climate of a small area. It may differ from the surrounding climate as a result of aspect, tree cover (or the absence of tree cover), or exposure to winds.

Climate: Climate is the average weather, usually taken over a 30-year period, for a particular region and time period. Climate is not the same as the weather but is the average pattern of weather for a particular region. Climatic elements include precipitation, temperature, humidity, sunshine, wind velocity, phenomena such as fog, frost, hailstorms, and other measures of the weather.

Weather: Weather is the specific condition of the atmosphere at a particular place and time. It is measured in terms of factors such as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. In most places, weather changes from hour to hour, day to day, and season to season.

Climate is an integral part of the climate-soil-culture complex and the factor that mostly determines the yield in food production. It is also the overriding factor influencing the type and quality of produce that can be grown in a particular area.

Different plants require different climatic conditions in order to produce the right quality and quantity of produce for the farmer to sell for a profit. Extreme climate conditions make farming more challenging.

Factors limiting farming enterprises in some areas are:

• High spring/summer temperatures
• Low relative humidity
• Water stress during critical growth periods due to poor availability
• Hail
• Wind, which causes damage to produce
• Climatic Conditions

Climate Conditions

Climatic conditions that should be taken into account are wind, rainfall, heat, frost and cold and hail.

Wind

Extremely windy conditions can affect growth, plant development and yield. Windy conditions hamper applications of liquids, such as spraying and irrigation. It also evaporates soil moisture rapidly, in particular in uncovered soils.

In the establishment of any production unit, prevailing winds and the possible effects thereof on plant development and subsequent income has to be considered carefully.

Rainfall

Sufficient rain to ensure enough water for irrigation purposes is one of the main requirements for successful plant production. The effect of too much or too little rain can, depending on the intensity, vary from negligible to catastrophic.

Prolonged dry periods, which occur in most parts of South Africa, can have a severe effect on yield and product size, and subsequently profitability.

Prolonged rainy spells in the summer rainfall areas during the spring and summer hampers spray programs and can result in heavy pest or disease infestations. Late summer or autumn rains can also have a negative effect on the quality of harvests, which in turn will influence how much can be marketed in specific ways (e.g. exports), with a subsequent reduction in income.

Rain during the harvest season, can affect the quality of harvests and increases the potential for post-harvest decay.

Heat

Extreme heat can have an impact on flowering events, which will have a direct effect on the crop yield. For example, in citrus production, during the November drop period, severe heat can cause a moisture deficit in the tree which also leads to an excessive drop of fruit lets.

Cold and Frost

Not all plants are impacted by frost in the same way; it is important to know first what the frost occurrence is in an area in order to select plants that can withstand local conditions.

Hail

Hail damage is a real threat in the northern production areas. Hail causes extensive damage to corpses.

It is prudent to examine the incidence of hail in any of the northern areas before developing a new production unit. The information on the incidence in the various areas is available from the crop insurance companies, who can also provide information on costs of insurance against hail damage.

Analysing Local Climatic Conditions

The Institute for Soil, Climate and Water have a central website for the weather station network in South Africa, where the climatic information collected throughout the country can be accessed. The web address is www.155.240.219.9/agric/ver1 and the e-mail address is opsroom@arc.agric.za.

To establish which weather station is the closest to the farm, the exact geographical position of the farm should be known.

The type of information which is required for enterprise selection and planning for as long a period as possible is the following:

• Average rainfall
• Relative humidity
• Average, maximum and minimum vapour-transpiration.
• Average, maximum and minimum wind speed and direction
• Average, maximum and minimum temperatures

All the above are available on an hourly, daily, monthly and yearly basis and the information can be accessed at all times.