b'ROUNDTABLEcompaction layers exist, says Barrett. This spring, we initiated some trial work with growers to verify the depth of compaction layers in their fields.At Oyster Cove, the Ramsays have used a simple penetrometer built using a protocol created by Kensington North Watershed Association staff in collaboration with scientists at Agriculture and Agri-Food Canada. This simple device has been shown to provide results similar to the complex and more expensive penetrometers on the market. In their own investigations of the extent of compaction in P.E.I. potato fields, Barrett and his team calculated the average penetrometer reading to be 200 psi at an 8-inch soil depth. This is a seriousAn aerial viewfindingthat measurement corresponds to a po- shows nutrient deficiencies caused by field traffic in a tential root penetration of about 35 per cent. In termssoybean crop. Even if growers of what type of compaction was observed, Barrettcant see it from the road, soil reports both surface compaction (with high soil bulkcompaction could be affecting densities) as well as compaction layers (plow pans)their crops. Using a drone,the crops uneven growth due to in many fields. soil compaction is evident. Sawatzky says testing for compaction is quitePHOTO: JODI DEJONG-HUGHESextensive in Manitoba and most growers work with consultants who use mechanical probes for more consistent readings. Findings reveal varying layers of resistance, he explains, and higher-traffic areas such as headlands tend to show the greatest issues. TRAFFIC takes good managementand in heavily-compact-There is still some degree of belief out there amonged fields, multiple years may be required to achieve PREVENTION growers that its better to spread out compaction,significant improvements.There are multiple practices that can minimizesays DeJong-Hughes, but this is an absolute myth.In Prince Edward Island, he and his colleagues compaction and its effects, and none of them areUse controlled traffic practices, she advises, onlyhave seen increased use of crops such as daikon new. Effective prevention is a matter of using most,driving in existing tracks.radish, sorghum sudangrass, forage pearl millet and if not all, of the practices consistently. That meansBarrett reports many growers in Prince Edwardalfalfa, all of which produce deep, penetrating roots. ensuring everyone on the farm is on board. Island are finding ways to decrease field traffic,They are also generally associated with building soil reducing the number of tillage passes, and passesorganic matter, which also improves the structure of DECREASING EQUIPMENT WEIGHT over the field by hilling at planting or putting seedersoil, he says. Many growers in Prince Edward Island, according toboxes on tillage equipment. Not only does this reduceAlfalfa generally requires a longer rotation of Barrett, are now using trucks/trailers with more axlesthe potential for compaction, but also saves timefour to five years to get the maximum benefit from its to spread the load. This takes effort to communicateand money. deep, fibrous taproots. Sudangrass and pearl millet to all equipment operators, but the benefits are real,Last year, the Ramsays started planting andneed to be mowed at least once to encourage root he says. tilling only on tramlines, and theyve also used agrowth, aiding in compaction mitigation. As well as decreasing axel weights, De- vertical tiller that goes down to 24 inches on tramBarrett and his team will be continuing field Jong-Hughes advises reducing the overall weight oflines in the fall, which did result in some increasedtrials with a number of growers to help quantify the your equipment as much as you can. The Ramsaysyield the year after. The benefits seem to be largelyimpact of these crops on soil health, soil compaction have already done this. They are now using smallerassociated with creating hills, and were not sureand marketable potato yield.tractors in their fields (weighing about 15,000what benefits were getting from the subsoil beingAt Oyster Cove Farms, Ramsay says they have pounds each) and have sold a piece of equipmenttilled, says Ramsay. We need replicated split trialstried a lot of rotational crops such as mustard and that they felt was too heavy. We still have a lot ofwith vertical tillage and controlled traffic. Its stillbuckwheat to determine what effect they will have three-point hitch equipment, Ramsay adds, andearly days in our understanding. on soil-borne disease and general soil health, but were still looking at ways to spread out the weightthey are moving toward more perennial forages for so that its not concentrated at the back.ROTATION the benefits of reduced tillage and to promote better DeJong-Hughes also advises using bigger tiresIts well known that employing rotation crops issoil structure. on field equipment and ensuring they are properlya good practice to achieve many aims, includingIn Manitoba, potato crop rotation generally inflated (not overinflated). minimization of compaction, but Barrett warns that itincludes rye, wheat, corn or soybeans, and a bit of 26 SPUDSMART.COM WINTER 2020'