Attention to detail bumps up second crop potential
Several factors are critical to successful ratoon crop production. The earlier the ratoon crop matures, the higher its potential yield. Therefore, rapid stimulation of regrowth is an important factor. Apply the planned preflood nitrogen rate immediately after harvesting the main crop and flood it into the soil to stimulate regrowth. Keep soils moist with a shallow flood until regrowth has advanced and retillering has occurred. After retillering, maintain a flood sufficient to control weeds.
1. Don’t flush fields after harvest.
Flushing permits the germination of rice grain residue from harvesting. Germinated rice seeds become weeds that compete for nutrients and light. Time does not permit them to produce panicles. Flooding immediately after harvest prevents the germination of these seeds through the formation of an anaerobic layer near the soil surface.
2. Consider main crop cutting height.
Traditionally, the main crop has been cut at about 18 inches above the ground (depending on variety). Ratoon tillers may be generated at any node below this height. Panicles from aerial nodes tend to be smaller with smaller grain compared to tillers originating from the crown. Panicles from different nodes may increase variability in maturity and decrease milling yield. Plot research and field verification tests have shown that reducing the cutting height will increase ratoon crop yield and uniformity.
In small plots, yields increased as main crop cutting height decreased to four inches. Yields did not increase below eight to 10 inches in field verification tests. Reducing main crop cutting height will delay ratoon crop maturity by six to 10 days. This delay can be offset by making a nitrogen application about seven days before main crop drain and flooding immediately after harvest. The reduced cutting height can be achieved during combining or by using a flail shredder. Note: If your ratoon crop is late, you may not want to reduce cutting height.
3. Fertilization tied to anticipated yield potential.
The recommended nitrogen rate for ratoon crop production is dependent on the anticipated yield potential. That is, if all or most of the following conditions can be met, rates as high as 70 pounds of nitrogen per acre for conventional varieties and 100 pounds of nitrogen per acre for semidwarf varieties can be recommended. These conditions include: 1) harvest before Aug. 15, 2) absence of disease in the main crop, 3) limited field rutting by equipment, 4) good weed control in the main crop and 5) yield of the main crop lower than anticipated but good growth potential. Decrease or eliminate nitrogen if the main crop harvest is delayed; ratoon tillers are few; disease is present; fields are rutted; or weed pressure is significant. Any delay in nitrogen and water application reduces the yield potential of ratoon rice.
4. Control broadleaf weeds.
Herbicide use for broadleaf weeds, particularly dayflower, is the biggest concern in ratoon crop rice. Several herbicides are currently labeled for use in ratoon crop rice. These include 2,4-D, Grandstand R and Basagran. Be sure to check the label for rates, timing and weeds controlled.
5. Be proactive toward narrow brown leaf spot (NBLS):
Drs. Mo Way and Shane Zhou discuss this topic on page 17. For more information on ratoon crop production, please refer to 2012 Rice Production Guidelines.
Garry McCauley, Lee Tarpley, Fugen Dou and X.G. “Shane” Zhou with the Texas A&M AgriLife Research & Extension Center at Beaumont contributed information for this article.