Wheat can be produced under varied climatic and soil conditions. The reason is the diverse genetic material available in the form of different cultivars.
Production regions (in South Africa) can be divided into 3 broad areas:
• the southern, winter rainfall; dryland area;
• the northern, summer rainfall; dryland area; and
• irrigated areas.
The southern winter rainfall area has a moderate climate (usually, no frost) and wheat is grown in the rainy season from May to November. Moderate temperatures mean that spring wheat is also planted. Soils are very stony and have limited water storage capacity, so the wheat crop depends on rainfall throughout the growing season.
The northern summer rainfall dryland area receives very little rain from planting time (May to June) until ears emerge in September. In this area, cultivation practices focus on soil water storage during the rainy season (summer) to ensure adequate soil moisture until the spring rains come. Early frost is a real threat, so planting dates are chosen to minimise the risk of cold damage during flowering. Intermediate types of wheat are produced in this area.
Irrigation wheat is produced on deep, well-drained soils to ensure optimum root development and so sustain the high potential of cultivars grown under such intensive conditions. Two crops are often produced in a year to ensure acceptable cash flow, because high financial inputs are needed. Spring wheat is produced in irrigated areas.
WHAT DETERMINES WHEAT YIELD?
Under all these production conditions, good yields and profitability can only be achieved by careful planning and management. Higher yields mean higher profits, as production costs per ton of grain decline proportionately as yields increase.
Avoid being inflexible about crop management. Learn to adapt and revise management strategies as the cropping environment, yield potential, commodity prices and input costs change.
Total grain yield per hectare results from:
- The number of plants per hectare.
- The number of ears per plant.
- The number of grains per ear.
- Individual grain weight.
These plant components (and eventually grain yield) are determined during the 3 main developmental phases and relevant growth stages. It is possible for a yield component determined later to partially compensate for reductions in one established at an earlier developmental stage. Stages for the different components overlap to some degree in their effect on potential grain yield, and they are determined in a specified sequence.
ESTABLISH TARGET YIELDS
Set a realistic target yield for your cropping programme, taking into consideration all the available resources. Target yields form the foundation for crop management decisions.
Cultivar selection, fertiliser rates, herbicide and insecticide applications and, in particular, financial planning and other management decisions can only be made with the aid of target yield objectives.
There are a number of ways to set a target yield:
- Experience (historical average yield over the past 5 years).
- Water available at planting (the sum of stored soil water at planting, plus the average effective growing season rainfall).
- Using long-term climate projections.
The risk associated with your selected yield target should be carefully considered. Profit is the compensation for taking risks, but be realistic. Certain management practices and target yields have a higher risk component.
ACHIEVING TARGET YIELDS
The key management decisions needed to achieve target yields and maximise profits include:
- Planning for the entire farm, including soil selection.
- A healthy, well-planned crop rotation system.
- Effective management of soil water available to plants.
- Soil analysis to decide on a relevant fertilisation and liming programme.
- Applying effective soil cultivation practices.
- Informed cultivar selection.
- Planting good-quality seed.
- Correct planting dates and seeding densities for selected cultivars.
- Using suitable planter speed and planting depth.
- Monitoring the crop and noting observations.
- Making decisions about weed, insect and disease control timeously.
- Harvesting the crop at the right time.
- Applying agronomic management principles.
- Developing a financially sound marketing strategy.
- This article was written by Willem Kilian and Annelie Barnard and first appeared in Farming SA.