Yesterday I met with Dr. Mark Williams at the University of Kentucky Horticulture Research Farm, also known as the UK South Farm. This farm has a rich history and is adjacent to the Waveland State Historic Site. About twelve years ago, Dr. Williams established half an acre of organic vegetables. Through a lot of hard work, this has developed into a twelve acre certified organic CSA, with an additional eight acres of certified organic research ground. Students in UK’s Sustainable Agriculture Program complete a summer-long apprenticeship program on the farm, applying concepts they learn in coursework during the academic year and getting hands-on experience with many different aspects of organic farming. One of Dr. Williams’s goals on the farm is to increase mechanization and efficiency in production and processing thereby decreasing the labor commitment which can be a large barrier to overcome for farmers who wish to transition to organic production. There are many innovative ways this goal is accomplished, including having standardized bed width and layout within fields and grassed alleyways between fields that accommodate harvest wagons. One important component, and one I was really interested in learning about, is their highly effective weed management program. Weeds are managed on the farm through a variety of physical, biological, and cultural means.
Cover crops play a large role in the farm’s weed management. As soon as a crop is harvested, residues are flail mowed and a cover crop is drilled using a no-till drill. Depending when crop harvest occurs and what crop will be in that field next, the cover crop might be sorghum-sudangrass; a mixture of oats, crimson clover, and field peas; or a mixture of rye and vetch and/or clovers. Some of these covers will not survive the winter (sorghum-sudangrass, and sometimes oats)—these fields can be planted earlier the following spring. Other cover crops like buckwheat are used during shorter windows during the season to avoid bare soil and crowd out weeds.
As is typical with vegetable crops, tillage is used for soil preparation. Cover crop biomass is incorporated with a spader; this implement also has tines in the back that do thorough yet shallow primary tillage. This tillage encourages a flush of weeds to emerge from the surface layer of soil. After this flush, what Dr. Williams calls a “stale seedbed cultivator” is used. This implement has different tools to uproot, sever, and bury weed seedlings, spiders on the sides to cultivate and further define the sides of the beds, and a roller in the back to smooth out the bed in preparation for planting. These tools concentrate disturbance on the top 1-1.5” of soil where germinating and emerging weeds are located and also creates a great seedbed for good crop establishment. They try to use it twice, each time killing the flush of weeds that emerges after the previous soil disturbance—this helps to deplete the number of germinable weed seeds in the top quarter- to half-inch of soil (part of the soil seedbank). This illustrates the stale seedbed concept—depletion of the germinable seedbank in the top layer of soil followed by planting with minimal soil disturbance. The depth here is key—after the initial spader pass, there’s no soil disturbance below 1-1.5” so no more weed seeds are brought up to a depth from which they can germinate. (In addition, this shallow soil disturbance helps keep deeper soil intact. There’s a lot of organic matter entering these soils with all the cover cropping and compost additions, so that helps maintain soil quality too!)
For crops grown on plastic like peppers and tomatoes, drip tape is then laid 6” deep under the crop row. (For crops grown on bare soil, like cole crops and greens, drip tape is also placed 6” deep under the row but this happens before the stale seedbed cultivator is used.) Placing the drip tape just under the crop row (there are two rows per bed), keeps irrigation water where the crop can use it best. When bed preparation is complete, crops are either direct-seeded or transplanted. Compost is applied over the whole fields prior to tillage, but all fertilizer applied at and after planting goes just on the crop row. Targeted resource placement just into the crop rows also helps with weed management.
Once the crops are established, they’re cultivated primarily with two different tools. The first cultivation pass uses rolling baskets, mounted on an offset cultivating tractor, which uproot small weed seedlings (see photo to the right). Subsequent cultivation passes are made with a super cool cultivator from Germany (photo on right, bottom). This cultivator also has different tools for different purposes. Shovels and side knives are used to uproot weeds between and alongside the beds, respectively. Finger weeders weed in the crop row—the yellow part is flexible and can uproot weeds right up to the crop plants without damaging the crop. There’s a seat mounted above these finger weeders (stay tuned for a photo!) that allows an operator to steer this unit. This allows some flexibility in case things aren’t planted in a perfectly straight line.
This system of integrated weed management has been developed over many years and works really well for this farm. There are other factors that I haven’t even talked about here—having two crop rows per bed allows for quicker canopy closure that shades out weeds, living mulches are used with some crops (see this photo of broccoli undersown with clover), and another piece of dedicated cultivation equipment is used to clean up headlands at the end of the beds. To me, one of the coolest things about this operation is its educational focus—all students going through the sustainable agriculture program at UK get to work on this farm, get their hands dirty, and learn about integrated weed management.