Rice in the Mid-South

Specialists Speaking- ANNA SMYLY

Rice in the Mid-South is typically grown using the direct-seeded, delayed flood production method where a continuous flood is maintained from the four-to-five leaf growth stage until a couple of weeks before harvest. Maintaining a flood throughout the growing season agronomically benefits rice by supporting healthy plant growth, suppressing weeds and diseases, improving nitrogen uptake, and maximizing rice grain yield.

Due to declining aquifer levels in the Mid-South, alternative irrigation strategies have become increasingly popular to aid water conservation and improve irrigation efficiency. Alternate wetting and drying (AWD), furrow-irrigated rice (FIR), and a tailwater recovery recirculating pump are three popular alternative rice irrigation strategies. Irrigation water in an AWD rice field is allowed to recede until soil surface is visible before the rice field is reflooded. An AWD study showed no rice grain yield differences between water level depths 4 inches above soil surface, water levels held at soil surface and water levels dropping 4 inches below soil surface. In another AWD study, rice grain yields and water usage were both comparable between an AWD and continuous flooded irrigation system.

Furrow-irrigated rice is grown where rice is sown into raised beds and irrigation water is applied down the furrows, allowing the crop to be irrigated without maintaining a continuous flood. A recent study done in FIR evaluated the overall and spatial effect of irrigating every day, every three, five, and seven days on agronomic characteristics, water level depths, and rice grain yield. Treatment plots irrigated every day had the greatest average yield of 163 bu ac^-1 but used the greatest amount of irrigation water (35 acre-inches). There was a correlation between rice grain yield and irrigation water level depths. Overall, rice grain yield was negatively impacted anytime water level depths dropped 1 or 2 inches below ground level.

In a tailwater recovery recirculating pump rice field, irrigation water runoff and rainfall are captured and pumped back on to the field to reuse the irrigation water. This irrigation method improves irrigation efficiency, while conserving water and maintaining yield. A current study comparing a continuous flooded environment, FIR, and recirculating furrow irrigated rice had no difference in rice grain yield amongst the three irrigation strategies. However, the tailwater recovery system used only 20.34 acre-inches of water compared to AWD (29.78 acre-inches) and continuous flood (30.89 acre-inches) irrigation methods.

These three irrigation systems each come with advantages and disadvantages and have circumstances where one is more preferred than the other. However, if the irrigation systems are used correctly and in the appropriate field situation, the systems have potential to utilize irrigation water more efficiently and still maintain rice grain yield.   ∆

ANNA SMYLY

MISSISSIPPI