Field Preparation

Heavy equipment traffic and excessive tillage cause soil compaction, which reduces potato yield and quality (see Soil Compaction). Minimize compaction by reducing the amount of traffic or weight in the field. Do not carry out unnecessarily tillage operations.

Potato producers use a wide range of tillage equipment and techniques to prepare the potato seed bed. The variation in tillage practices results from the wide range of soil types used in potato production and the variety of tillage implements available for soil preparation.

Regardless of the tillage system used, it must meet the following criteria:
Incorporate trash – A balance must be maintained between incorporating an adequate amount of crop trash to facilitate planting while maintaining sufficient soil trash cover to prevent wind erosion. Crop residue must be incorporated into the soil to allow for trouble free planting. The amount of tillage required to do this will depend upon the soil type, the type of crop preceding potatoes and the ability of the planter to perform properly in crop residues. Tillage should not incorporate so much crop residue that the soil is susceptible to wind erosion. See Soil Conservation section for more details regarding soil erosion.

Produce good tilth without drying out the soil or producing soil clods - Tillage should produce enough loose soil to allow the planter shoe to penetrate to the desired depth and to provide the hiller discs with enough loose soil to construct a proper hill over the seed. Tillage that dries out the soil surface will reduce emergence and vigor. Tillage of finer texture soil types (loams) with the wrong implement or at the wrong soil moisture content will produce clods that remain intact throughout the growing season and into harvest. Soil clods are difficult to separate from the potatoes on the harvester thus reducing efficiency and increasing cost. Hard dry clods that come into contact with the tubers on the harvester and other handling systems will cause blackspot bruising. For more information on bruise prevention see section 3.8.4 Bruise Prevention.

Herbicide incorporation - Sufficient tillage is required to properly incorporate pre-emergence herbicides. Follow the chemical manufacturers’ instructions regarding the tillage method required for herbicide incorporation

Field preparation should be performed in as few operations as possible. Excessive tillage will increase the cost of production, the likelihood of wind erosion and the amount of soil compaction. Below is a short description of three common tillage methods used on the Prairies.

Conventional
Operations such as deep tillage or discing are performed in the fall and cultivation is performed prior to planting in the spring.

Advantages: Inexpensive – Low capital and operating costs High capacity – 15-25 acres/hour (6-10 ha/hr) depending upon tractor speed and width of implement Preserves surface trash depending upon number of operations and shovel design

Disadvantages: Can produce soil clods, depending upon soil conditions at the time of tillage

Rotary Power Cultivator
In Manitoba and Saskatchewan, producers growing potatoes on loam and clay loam soils use conventional tillage (deep tiller or double disc) in the fall. In the spring, a single pass with a rotary power cultivator prepares the soil before planting. The rotary cultivator is a power cultivator that stirs the soil laterally rather than mixing the soil vertically like a rotovator.

Advantages: Clod free soil bed Preserves surface trash Preserves moisture, especially important in rain-fed production

Disadvantages Low capacity – 5-7 acres/hour (2-2.8 ha/hr) with a 20-foot (6 m) implement depending upon soil conditions and texture Costly – High capital and operating expenses Poor weed control – has a tendency to transplant rather than destroy weeds

Fall Bedding and Reservoir Tillage
A fall bedding and reservoir tillage (diking) implement performs both the tillage and hilling operations. In the fall prior to spring planting of potatoes, the field is tilled with a deep tiller or a double disc. Next, deep subsoil tillage is performed, hills are constructed and reservoir dikes or depressions are formed between the rows (Figures 3.4-7 and 3.4-8). The reservoirs capture water from melting snow and increase soil moisture. In spite of the aggressive fall tillage, surface trash cover is preserved, reducing the potential for wind erosion. In the spring, the hills are packed with rolling wire baskets to break up soil clods that survive the freezing and thawing cycles over the winter, the hills are reshaped and the reservoirs are removed. The potatoes are planted directly into the pre-formed hills. After planting, the final hilling is carried out and new reservoirs are formed between the rows.

Advantages: High Capacity – 8-11 ac/hr (3-4.5 ha/hr) in fall, 15 ac/hr (6 ha/hr) in spring Hills warm up faster in the spring Increased water retention Reduces run-off and drown-out in low areas as a result of precipitation or irrigation More even moisture between high and low areas of the field Clod free soil preparation Preserves soil trash

Disadvantages: Costly – high capital cost Requires a large tractor (>300 h.p.) in the fall

Written by B. Geisel and L. Delanoy

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