Currently, University Extension Services recommend a seeding rate of 30 to 40 seeds/ft² for conventional varieties in order to achieve an optimum final plant population ranging between 10 and 20 plants/ft². These are recent changes, as the former seeding rate recommendation was 40 seeds/ft² with a final plant density of 15 to 20 plants/ft². The recommendations assume that 50% or more of the planted seed will not emerge. With today's drill-seeding technology and fungicide seed treatments, we hypothesize that on average, emergence is better than 50%, and that seeding rates can be lowered even further while not sacrificing yield or milling quality.

Rice has the innate ability to compensate for voids in the canopy by producing more reproductive tillers. Since the introduction of hybrid rice, producers who have grown it have become accustomed to sparse stands after emergence, and then watched as the canopy was filled and excellent yields were obtained. In a recent 3-year study on a silt loam soil it was determined that seeding rates ranging from 5 to 40 seed per square foot did not affect yield of Wells, CL161, or XL8, indicating that seeding rates for these varieties can be reduced while not sacrificing yield. Based on these results, we are not suggesting that growers set their drills to plant 5 seed per square foot; however, we are suggesting that growers evaluate their current seeding rates and consider lower rates, especially on well-prepared silt loam soils. When planting early in cool conditions or on heavy clay soils, seeding rates may need to be increased to compensate for reduced germination and poor seed to soil contact.

Studies were initiated in 2005 evaluating the interaction of seeding rate, variety, and nitrogen rate and their effects on yield and milling quality. The varieties being evaluated include Cheniere, a new semidwarf long-grain, Wells, a popular conventional variety, and CL131, the latest CLEARFIELD* semidwarf variety. Seeding rates ranging from 7.5 to 60 seeds/ft² are being evaluated with total nitrogen rates ranging from 60 to 180 lbs N/Acre. We have also initiated an experiment evaluating an early-season application of ammonium sulfate at low seeding rates to determine if such an application can be used to recover yield at low plant densities. This is a regional project being conducted in Arkansas, Louisiana, Mississippi, and Texas.

In 2006, two studies were initiated at the Lee Farm and at the Rice Farm near Glennonville to evaluate the effects of seeding rate, nitrogen rate, and variety on the incidence and severity of sheath blight disease. When scouting for sheath blight, the first lesions usually appear where rice was double-planted on the edges or where fertilizer overlap occurred. Sheath blight forms in these areas first because of the lush canopy as a result of dense plant stands and over-fertilization. Although some rice varieties are more susceptible to sheath blight than others, we hypothesize that by reducing the seeding rate to allow more air flow through the canopy, we can reduce the incidence and severity of sheath blight, possibly eliminating a costly fungicide application.

2006 Field Day Report