ORGANIC POTATO PRODUCTION especially vulnerable to egg laying if surrounding corn hasnot reached the mid-whorl stage during the spring flightperiod.4.4 Soil and Air DrainagePotatoes need well-drained soil to reduce the risk of pink rotand Pythium leak and powdery scab. Late blight will be lessprevalent in fields with good soil and air drainage. Anypractice that promotes leaf drying can slow development offoliar diseases because of the general need by pathogens forwet surfaces during infection. Fields with poor air movementsuch as those surrounded by hedgerows or woods are apoor choice for <strong>potato</strong>es. Plant rows in an east-westdirection and avoid overcrowding to promote drying of thesoil and reduce moisture in the plant canopy.5. WEED MANAGEMENTWeed management can be one of the biggest challenges on<strong>org</strong>anic farms, especially during the transition and the firstseveral years of <strong>org</strong>anic production. To be successful, usean integrated approach to weed management that includescrop rotation, cover cropping, cultivation, and plantingdesign based on an understanding of the biology andecology of dominant weed species. A multi-year approachthat includes strategies for controlling problem species in asequence of crops will generally be more successful thanattempting to manage each year's weeds as they appear.Relying on cultivation alone to manage weeds in an <strong>org</strong>anicsystem is a recipe for disaster.Management plans should focus on the most challengingand potentially yield-limiting weed species in each field. Besure, however, to emphasize options that do not increaseother species that are present. Alternating between early andlate-planted crops, and short and long season crops in therotation can help minimize buildup of a particular weed <strong>org</strong>roup of weeds with similar life cycles or growth habits, andwill also provide windows for a variety of cover crops.5.1 Record KeepingScout and develop a written inventory of weed species andseverity for each field. Accurate identification of weeds isessential. Weed fact sheets provide a good color referencefor common weed identification. See Cornell weed ecologyand Rutgers HUweed galleryUH websites (References 24- 25)5.2 Weed Management MethodsPlanting and cultivation equipment should be set up on thesame number of rows to minimize crop damage duringcultivation. Specialized equipment may be needed tosuccessfully control weeds in some crops. See resources atthe end of this section to help fine-tune your weedmanagement system.For optimal weed management in <strong>potato</strong>es, plan severalseasons ahead. Do not plant <strong>potato</strong>es in a field infestedwith quackgrass, which can damage tubers. Eliminatequackgrass and other perennial weeds and reduce the seedbank of annual weeds (1) by growing crops that requireintensive cultivation, (2) by growing short season crops andcleaning up the field quickly after harvest, and (3) by usingcultivated fallow periods.Before planting <strong>potato</strong>es, incorporate any growing weedscompletely using a moldboard plow, spader or rotary tiller.When planting, ensure that the seed pieces are wellcovered. The surface after planting should be flat or havean inch or two of extra soil over the rows. If soil ismounded on top of seed pieces that are planted near thesoil surface, tine weeding will probably uncover the seed.Placing extra soil over the rows with the planter ensures thatthe seed remains covered and guarantees aggressive actionby the tine weeder as it knocks the extra soil into theshallow valleysTine weed every 5-7 days until <strong>potato</strong>es emerge and againwhen the shoots are 4-6". At least one pre-emergence andone post-emergence tine weeding will be needed. Anoptimal tine weeder for <strong>potato</strong>es will have stiff tines with a45-degree bend. Tines should be set so that they do not hitthe seed pieces. In particular, check to ensure that no seedpieces are flipped out of the ground by the weeder. Set thetines to run ½ to ¾" above the seed and move at 3-4 mphfor optimal weed control.If a tine weeder is used as recommended above, begin interrowcultivation when plants are about <strong>12</strong>-15” tall. At the firstcultivation, heap 2”-3” of soil around base of plants in therow to bury small seedlings. Soil can be moved into thecrop row either with disk hillers or with sweeps that have arelatively steep angle. The goal is to have the highest pointof the soil in the line of the crop, rather than a dip in themiddle where weeds remain uncovered. If <strong>potato</strong>es aregrowing slowly, an additional cultivation might be needed.Most likely, the next operation will be hilling. If a tineweeder is not available, begin inter-row cultivation when thefirst flush of weeds has emerged, regardless of whether the<strong>potato</strong>es are up yet. Throw sufficient soil into the row tocompletely cover weed seedlings. Repeat for eachsuccessive flush of weeds until the final hilling."A standard hilling operation will usually cover any additionalseedlings that have emerged. After hilling, the <strong>potato</strong> plantsare usually too large to cultivate again, but sometimes anextra cultivation between the rows will be useful.Between hilling and harvest, rogue out any large weeds thatget established: In doing so, you will (1) prevent seed setthat could pose problems for rotation crops (2) eliminatepossible virus hosts and (3) avoid the development of verylarge weeds that can jam up the <strong>potato</strong> digger. Rogueingout large weeds may require less labor than cleaning out thedigger when it becomes jammed.Before harvest mow the vines. This will not only makedigging the <strong>potato</strong>es easier, but will also decrease thelikelihood of weeds going to seed. Many weeds that havealready flowered will continue to set seeds even if they havebeen completely uprooted and left on the soil surface.820<strong>12</strong>
ORGANIC POTATO PRODUCTION Some growers flame the residue after mowing to speeddrying and kill fungal spores that might infect the tubers.This has the additional benefit of further reducing seedproduction, for example, by short weeds between the hillsand by pieces of pigweed flowering stalks.Reference HUCrop Rotation on Organic Farms: A Planning ManualUH, App. 4 (Ref. 21) HUSteel in the FieldUH e-‐book (Reference 23) Cornell Weed Ecology websiteH (Reference 24) HUNew Jersey Weed GalleryUH (Reference 25) HUPrincipals of sustainable weed management for croplandsUH (Ref 27) HUNew cultivation tools for mechanical weed control in vegetablesUH (Ref 28) HUWeed 'Em and Reap videosUH (Reference 29) HUFlame weeding for vegetable cropsUH. (Reference 30) HUVegetable farmers and their weed control machinesUH (Reference 31).920<strong>12</strong>
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