Variety, row spacing and soil type all play roles in determining the seeding rate needed to reap the highest yields possible from your rice crop.
Seeding rate guidelines in the Mid-South have generally recommended planting 40 seeds per square foot to get 15 to 20 rice plants to emerge. However, with better seed placement, especially on good seedbeds, rice researchers are discovering that seeding rates can be reduced to about 30 seeds per square foot for most conventional rice varieties.
With the introduction of new drills with more precise seed placement, it is time to try reducing seeding rates, according to Joe Street, Extension rice specialist at Delta Research and Extension Center in Stoneville, Miss.
Before you begin calibrating your planter accordingly, rice specialists recommend using your desired number of seed per foot to calculate a seeding rate for conventional varieties. Because seed size often varies greatly between varieties, the number of seed per square foot can greatly affect the number of pounds of seed planted per acre.
“We don't need to simply be planting 90 pounds of seed per acre,” Street says. “If you are planting 90 pounds of Cocodrie, you're planting close to 30 seeds per square foot. If you're planting 90 pounds of Priscilla, you're pretty close to 40 seeds per square foot.”
In general, 40 seeds per square foot will equal 20 seeds per foot of row for 6-inch row spacings, 23 seeds per foot for 7-inch rows, 27 seeds for 8-inch rows, and 33 seeds per foot for 10-inch rows. Calibrating your drill for a target seeding rate of 30 seeds per square foot equates to 15 seeds per foot of row for 6-inch row spacings, 18 seeds per foot for 7-inch rows, 20 seeds per foot for 8-inch rows, and 25 seeds per foot for 10-inch rows.
Seeding rates differ somewhat for hybrid rice varieties, which Street says should be planted at 30 pounds per acre — about 14 seeds per square foot. A seeding rate of 14 seeds per square foot usually results in a stand of eight to 10 plants per square foot.
“Rolling the field with a flat roller will increase seed-to-soil contact and increase emergence,” Street advises. “Several growers are using wider drill spacings so they can drill soybeans and rice with the same drill. With 10-inch row spacings, 40 seeds per square foot are too many.”
In Mississippi rice research plots, seeding rates as low as 20 seeds per square foot produced the same yield as 40 seeds per square foot. “I am not yet ready to recommend planting 20 seeds per square foot for conventional varieties, but I am confident that in a relatively good seedbed, planting 30 seeds per square foot will work well.”
If you plan to reduce seeding rates, Street suggests applying gibberellic acid and a good fungicide seed treatment.
“If you are planting early, it's good insurance. If you are planting late, it's probably worth the money. It will get you about two to three nights of extra sleep,” he says.