2015 Annual Report for FNE15-816
Wet rice organic weed control trials
Summary
Our project assesses organic weed control methods and combinations of methods for temperate wet rice. The initial phase of this project was to establish prior use field conditions as these bear considerably on the presence of weeds, and to assess the importance of crop rotation in an overall weed control strategy.
Three plots were set aside for the field trials to take place during the 2016 growing season. These plots were treated three different ways, to establish three different prior-year conditions upon which to conduct an identical array of field trials.
Objectives/Performance Targets
Our array of rice paddies at Boundbrook farm consists of 5.5 acres of growing area leveled for irrigation and surrounded by berms. Over the course of the 2015 growing season the trial plots were set up in three separate but adjacent paddies known to be largely uniform in their soil properties. All have clay soils with about 10-12% organic matter. We labeled them A, B, and C.
Since the integration of fallowing or rotation seems so significant in that it can deplete weed seed reserves and/or disrupt weed life cycles by providing an unpredictable alternating dry and wet environment, we designed this as a two year trial. The objective for the 2015 season was to establish three different prior-year regimens for the three plots.
Accomplishments/Milestones
In 2015, rice was grown in our normal way (flooded, with ducks and azolla) in Paddy A, while Paddy B and Paddy C were subjected to a wet and a dry fallow respectively.
Throughout the 2015 growing season, Paddy B was maintained in a wet bare fallow state. No crops were be planted, but the paddy was flooded with over 4 inches of water and puddled at regular intervals throughout the season to destroy emerging weeds. The strategy is to promote the germination of weeds and to subsequently destroy them in order to deplete the weed seed reserves.
Paddy C was maintained in a dry state. We planted consecutive crops of winter rye as a green manure and till them in at 6-week intervals beginning in June 2015 with the last planting in September.
Impacts and Contributions/Outcomes
In plot A, where our normal method of growing wet rice and azolla was used, we obtained some of the best weed control and crop health we have seen thus far. We also had an average yield of 2500 lbs of saleable rice to the acre in the area designated as plot A. We did general assessments of performance this year since the goal was the establishment of prior-year practices rather than measured trials. However this does suggest that weed populations in this plot will not be unusually heavy as a result of weed seed bank accumulation.
Our wet-fallowing method in plot B went according to plan. We introduced some azolla into this plot but it did not really flourish. Weeds were adequately suppressed by the frequent tillage passes for the duration of the season.
The 2015 season had a very wet start which made it difficult to maintain plot C in a dry state. We planted rye at the earliest opportunity, in late June, and replanted once mid-August.
Plots A, B, and C now have their respective prior-uses established and are ready for the field trials to take place in the 2016 growing season.