By Hugh Martin
OMAF, Organic Crop Production Lead
To obtain profitable yields farmers should plan to establish optimum plant populations for their crops. Low final plant populations reduce yield and allow weeds to grow into problems at harvest. Organic field crops (corn, oats, barley, wheat, rye, spelt, and beans) should be planted to achieve similar final plant populations as those for conventional corps. Suggested seeding rates are found in the COG Organic Field Crops Handbook. Typical seeding rates for conventional field crops are also found in the OMAF Agronomy Guide (also found on the web at http://www.gov.on.ca/OMAFRA/english/crops/pub811/11sdng.htm). In some cases, for example on drought-prone soils, or where other specific stresses are known, plant populations may need to be reduced. Open-pollinated corn is frequently planted at lower populations than hybrid corn but may vary with variety, check with you seed supplier.
Using rotary hoes and weeder harrows will reduce the plant population. Using multiple passes, or if the equipment in not properly adjusted, can reduce the plant population by up to 25 %. When planning to use this equipment, seeding rates should be increased to make sure that final populations will be adequate.
The actual seeding rate you plant will be higher than the desired final plant population. Good quality seed planted under ideal conditions will likely lose 5-10% of plants due to faulty germination or pests at germination. Seeding rates should be increased if seed is less than 90% germination, or if it is planted under less than ideal conditions. Cool soils, dry soils, cloddy conditions, or long wet periods after planting will all reduce the emergence potential of the crop and may necessitate higher seeding rates.
If seed has germination below 80%, it probably has low vigour, and usually will not produce a good crop. Always use good quality seed. Use commercially certified seed or when using saved seed, make sure it has been cleaned to remove chaff, weed seeds, and diseased seeds.
Some reports have suggested that plant populations on organics farms should be higher than conventional to obtain better competition with weeds and to allow for losses due to pests and mechanical weed control.
_SIMCOE COUNTY
