Points of info & thoughts from my side, mainly based on rice-cropping in Tanzania, Mali, Rwanda, Ethiopia: 1) Propanil .http://de.wikipedia.org/wiki/Propanil....was and is probably a major herbicide, but the successful application was so delicate / complicated due to the time-precise instructions to be followed; however: perfect application in rainfed rice gave some good results. The commercial product Stam-F34? was common during the 80ies. 2) Observations in review of 40 years guide me to the recommendation to avoid chemicals out of environmental and health reasons. 3) The non-chemical treatments in rainfed rice to be applied with great success are: a. Using pre-germinated seed and giving the plants a big lead over the emerging weeds. b. Using fine tine-tillers / interrow-weeders at very early stages and repeatedly.Can be on hand-labour level and on mechanized level. c. Not forgetting the big potential of intermittend soil-preparation, leaving enough time between ploughing / and-or harrowing and-or second harrowing so that weeds can emerge. 4) Be aware and conscious that rainfed rice has globally big environmental advantages compared to swamp-rice with all its GHG-emissions. Therefore rain-fed rice with perfect agronomy should receive much more attention.

Thanks  Dr Bernhard. It is really good to know the non-chemical treatments in rainfed rice systems. It is true but as said perfect agronomy should be developed. Regards

You've hit on the most important reason why commercial aerobic rice production is practices to only a limited degree worldwide. Small scale rice producers might be able to stay on top of their weeds by weeding. However, the high amount of time (and drudgery) required for weeding takes away from other economic enterprises that otherwise could improve a families economic well being.

Many of the herbicides that are used to control weeds in flood system rice should provide effective weed control for aerobic rice production systems. However, timing and rate of application may be different for aerobic rice production. Fertilizer and insect, weed, and disease management inputs need to be used judiciously to help insure that the costs do not get out of hand and potentially exceed the economic returns.

Bernhard's recommendation of growing cultivars that shade out emerging weeds is a good one. The idea of planting pre-germinated (pipped) rice seed is also a very good approach. I might add that cultivars that have higher node production rates during early seedling development and that produce tillers whose tiller and leaf angles are less erect will help to suppress weed germination and growth. However, some cultivars that are less erect may have a greater tendency to lodge. Aerobic rice should also benefit from seeding (or transplanting) at a higher rate, thereby increase the competitiveness of the rice with weeds. 

If you pursue comprehensive aerobic rice weed management field experiments, I would be interested in hearing about your results.

Thanks Dr Lloyd, for such an interesting answer. Actually I worked on Aerobic rice during my stay in IARI, New Delhi. I worked on farmers fields of Western U.P. in India under CPWF project in partnership of IRRI. I am still in touch with quite a lot farmers from villages where we worked and demonstrated aerobic rice cultivation. Of course we use chemical way,i.e. pre emergence application of pendimethalin and it was successful. But now the farmers are asking if some thing sure to control weeds which is as you said major problem in enhancing adaptability of aerobic rice available than only they will go for it. They have water problems and due to climate change we have very erratic and less rains too. They well convinced about water saving in this method of rice cultivation but only problem is the weed control which is limiting its wider spread in worldwide. 

Definitely if  I will conduct any experimentation on farmers field or any other team member/ friend scientist will conduct I will share those results with you.

Sarwan: Best of wishes for your aerobic rice research. When Drs. Prabodh Illukpitiya and Omar Samonte worked at the Beaumont Center, we wrote a review-paper comparing the benefits and costs associated with aerobic and flooded rice production, as part of an analysis to determine whether aerobic rice can be economically produced in the U.S. I've attached a pdf copy for you.

Dr. Dante Tabien, who is the flood production system inbred rice breeder at the Beaumont Center, is interested in developing cultivars that can be grown economically under aerobic production.  He feels that genotypes could exist that are more efficient at extracting water from deeper in the soil than what occurs with cultivars grown under a flood production system. 

Thanks Dr Lloyd, for such a wonderful review paper. Please also inform me if some specific varieties/cultivars for aerobic conditions developed and can be used in our conditions. With all regards Dr Dubey

Sir, as per my recent knowledge, a novel formulation with the name of Bis-pyribac-sodium (trade name Nominee Gold) is very popular now to control post emergent weeds in upland or aerobic paddy culture. Start your weed control measures with pre-emergence application of pendemethalin (1.5kg a.i./ha)  followed by post emergent application of bispyribac sodium at 20-30 days after sowing, it will give satisfactory weed control in paddy.

Sarwan: Some of the Nerica varieties developed by WARDA might be appropriate due to having relatively high tillering rates and higher than average yield. The challenge will be finding a rice cultivar that has an appropriate mix of high growth rate, strong culm strength to resist lodging, tolerance/resistance to the most common plant diseases in your area, relatively high yield, and acceptable grain quality attributes. 

Dear Dr Raman: Thanks for suggesting Nominee Gold. I will ask my farmers to try the combination of Pendi and Nominee Gold.

Regards

Thanks Dr Lloyd once again for informing about Nerica varieties. Of Course it is true that in our area of cultivation lodging is a big problem. Hence strong culm strength is required. If the traits you mentioned could be puted in one variety then what else aerobic rice cultivating farmer's need. Thanks and regards Dr Dubey

In Kerala, India we are recommending the pre emergence application of oxyfluorfen@ 0.15 kgai/ha 2-3 days after sowing in dry seeded rice. This can effectively manage all types of weeds in the crop stand for 15 days. Care should be taken to see that most of the pre emergence herbicides work effectively in moist soil rather than dry soil. But, if the soil is flooded after the application there can be chances for phytotoxicity to seeds sown below. Pre sowing application of the same chemical @0.2 kg/ha has also been tried 2-3 days before sowing.  

Thanks Nimmy ji, Will you please elaborate the results of pre sowing application of oxyfluorfen @ 0.2 kg ai/ha. 2-3 days before sowing. As in our area (Western Uttar Pradesh we tried pendi just after dry sowing in dry field which works well if havey rains are not followed immediately after application.

Hello Dr. Dubey! In Southern Brazil, we are working in rice crop under sprinkler irrigation, and we are also using pre emergence application of clomazone (400 g ha-1) or higher rates of clomazone with safener seed (until 1,000 g ha-1). This option is good to grass control for 20-30 days in our situation. Additionally, post emergence application of cyhalofop-butyl or clefoxydim (ACCase inhibitors) are necessary to new grass emergence. In Technology Clearfield® (rice varieties with tolerance to Inhibitor of ALS herbicides) the option of Imazethapyr + imazapic or Imazapyr + imazapic (commercial formulation) is good option for all types of weeds over 60 days. Best regards.

respected sir

Please see this link and attachment you wil get more information about weed mangement in aerobic rice

Thank you

http://www.indianjournals.com/ijor.aspx?target=ijor:ijws&volume=42&issue=3and4&article=009

Thanks Dr Sunil, I appreciate your help. Regards