Rice irrigation in the south has historically been achieved using levees or dikes, which are built new each year to hold a shallow flood across fields. Gates are installed in each levee to regulate the depth of the flood and allow irrigation water to cascade from one paddy to another in the field. This method is still used on most of the rice acres in the South. A few growers in the Mississippi Delta region began furrow irrigating rice as early as the 1990s. In the last three to five years, furrow-irrigated rice has been adopted by many growers throughout the rice growing area of the Mississippi Delta.
A Common Misconception
Rice can only be grown in standing water, right? Wrong! Rice does need moisture to grow, just like the rest of our crops. The big difference is that rice will grow in a flooded environment whereas corn, soybean, wheat and cotton will not. The main purpose of flooding rice is for the weed control it provides. If weeds are controlled prior to flood, most grass and broadleaf weeds will not be able to germinate and emerge through the flood water.
If you have ever driven through the Mississippi Delta in the summer, you’ve seen a rice field. The number of levees and whether they are straight or curved all depends on the slope of the field. Some will have levees so close together you can’t fit a combine header between them.
The time, labor, and equipment required to build and maintain levees each year makes furrow-irrigated rice an attractive option. Prior to planting, beds are constructed with the same equipment used for other furrow-irrigated crops. Rice is planted with a grain drill and pest management is conducted in much the same way as conventionally grown rice. Irrigation frequency is typically every two to five days depending on soil type, slope and irrigation pump output, among other factors. Most growers will build a levee at the lower end of the field, or they will use a road or other land structure to capture and hold the water on the bottom of the field. This results in the bottom third of the field being permanently flooded throughout the growing season.
Risks and Benefits
The clearest benefit of furrow-irrigated rice is increased efficiency in planting, irrigation and harvest. Rice can often be no-tilled on beds from the previous year’s crop. Fields left bedded will dry out quicker in the spring, allowing for more planting days between precipitation events. Less labor is required to irrigate furrow rice in a timely manner, allowing more land to be used for rice production. Arguably the greatest benefit of this production method is harvest efficiency. Furrow-irrigated rice harvests like a wheat field, compared to having to harvest each paddy individually. Also, the fields can be re-bedded and left until spring, with corn or soybean no-tilled into the old rice beds.
Generally, there is not appreciable water savings compared to permanent flood, although this is not the case in all fields. More support equipment would likely be needed to keep up at harvest. Nitrogen deficiency and reduced yields on the top third of fields can be an issue due to leaching where the soil is intermittently wet and dry but never flooded. Weed control can be a challenge without the permanent flood to aid suppression of weeds. Unfortunately, some crop insurance companies refuse or are hesitant to insure furrow-irrigated rice.
Future of Furrow-Irrigated Rice
Furrow irrigation is not the answer for all rice fields. There will always be fields where permanent flood will be the preferred irrigation method. Research is being conducted across the Mississippi Delta to determine which of our current varieties and hybrids are better suited to this production method. Other research includes fine tuning fertilizer and pesticide recommendations to address challenges faced as this production technique increases in adoption across the south.