Water seeding rice requires more seed than drill seeding in order to establish an optimum stand. The increased seeding rate is used to overcome reduced germination and seedling survival as compared to the more efficient drill seeding system recommended for Clearfield and Provisia varieties.
Another potential stand establishment hazard of water-seeded rice is the potential for rice seed to move in the water prior to germination and pegging due to high winds and wave action. This seed movement can cause areas of high- and low-plant populations.
Water-seeded rice will mature approximately 10 days faster than drill-seeded rice. There is nothing wrong with planning for water seeding, but consider holding off until we get later in the optimum drill-seeded window. In other words, if wet weather persists after April 15, then you can make a firm decision on water seeding rather than drill seeding.
There are many ways to water-seed rice. For the Clearfield Production System and the Provisia Rice System, we recommend the water-seeded, delayed-flood cultural practice.
In this system, rice is flown into a shallow flood and allowed to germinate. The water is then drained to allow for the rice to peg into the soil. After draining, rice is managed similarly to drill-seeded, delayed-flood rice.
Water seeding with pre germinated seed is rarely practiced since most rice is treated with insecticide and fungicide seed treatments, which are not labeled for pre germination.
Regardless of the method, water seeding typically requires at least 30% more seed per acre. Higher seeding rates are used when unfavorable planting conditions exist.
The targeted plant population of an established stand is still approximately 15 plants per square foot. Reduced seeding rates may be possible to achieve this target plant population, but due to the stand establishment issues for water seeding mentioned above, higher seeding rates are often used to make sure the optimum plant population is reached.
Rice water weevils (RWW) can be a severe problem in water-seeded rice. The adult weevils are attracted to open areas of water during early seedling development. RWW larvae cause damage to rice seedlings by pruning the root system. Root pruning occurs much earlier in water-seeded rice than in drill-seeded rice. The RWW are attracted to the field earlier than in drill-seeded rice.
Because the younger rice is flooded, more generations of RWW larvae are likely, leading to longer time for feeding pressure compared to drill-seeded rice. In water seeded rice, the larvae feed on less-developed roots of 2- to 3-leaf rice causing more severe injury early compared to tillering rice in drill seeded culture. Preventative treatments are generally required to control RWW in water seeded rice.