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2022 Midwest Vegetable Guide

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Potato – Horticulture Midwest Veg Guide 2022 233 Potato – Horticulture Major update by Ben Phillips, Liz Maynard – Oct 2020 Reviewed by Liz Maynard – Aug 2021 Crop Description Potatoes (Solanum tuberosum) are a staple food grown from small tubers of a mother plant that is grown by specialized seed-potato producers. The Midwest produces potatoes primarily for table stock and processing into potato chips. Varieties used for chipping are usually brown skinned, white- fleshed, and globe-shaped to facilitate slicing from any direction. Table stock potatoes include 'starchy' (high dry matter) baking varieties and 'waxy' (low dry matter) boiling varieties in numerous skin and flesh color combinations with widely variable sizes and shapes. Starchy varieties include the Russets. Waxy varieties include Norland Reds. Some varieties are intermediate between those two types, for example Yukon Gold. Scab is an important disease that affects the marketability of table stock potatoes. One way to manage scab is to maintain a soil pH of 5.0 to 5.2. However, low soil pH reduces phosphorus availability, and most rotational crops will not perform well at the low pH. In fields with a history of scab, using scab-resistant varieties is the best option to avoid having to adjust pH to the detriment of rotational crops. Planting and Spacing Tuber production: Rows 34 to 36 inches apart. Seed pieces 9 to 11 inches apart in row, depending on variety and intended use. Seed 16 to 18 100-pound bags per acre. Seed piece should be 1-1/2 to 2 ounces. Using B-size certified seed will save cutting labor and reduce tuber-borne diseases. Seed stock production: Select seed stock from high-yielding hills that are smooth, well-shaped, and free of diseases and insect injury. When possible, obtain certified G1 or G2 (generation) seed stock. Store seed stock in new crates to avoid disease contamination. Seed potatoes should be at least 1-1/2 to 2 ounces in weight. If cutting larger seed potatoes, warm to 45°F before cutting, then sort to remove blind, slab, sliver, ripped, and undersized pieces after cutting. Cure cut stock at 38°F to 40°F, with 85% to 95% humidity in piles less than 6 feet deep, with good air circulation for 6 to 10 days. To supply one acre of seed potatoes, you need roughly 14,000 to 26,000 seed pieces. Fertilizing pH: Maintain a soil pH of 5.5 to 6.5. Before planting, do not fertilize with N or P, but apply 50 to 400 pounds K 2 O per acre based on soil test results and recommendations from your state. The most efficient way to spread the remaining fertilizer is with a banded application at planting at least 2 inches below and 2 inches to both sides of the tuber. As a banded starter fertilizer, apply 0 to 30 pounds N per acre, 0 to 150 pounds P 2 O 5 per acre, and 0 to 200 pounds K 2 O per acre. The rate of K 2 O should not exceed 200 pounds per acre when banded. Manganese may be needed when the soil pH is above 6.5 on mineral soils and above 5.8 on organic soils. Use a soil test to determine the amount of manganese needed. Include the required amount of manganese in the starter fertilizer, or spray the foliage with 1 to 2 pounds of manganese per acre at least twice during active growth. On sandy soils, broadcast 30 pounds or band 15 pounds sulfur per acre. Sidedress once at emergence and once at hilling or tuber initiation with 50-75 pounds N per acre each time. The second application can be adjusted according to rainfall and a petiole nitrate-N analysis. Use lower end of range for early- maturing varieties. Reduce the amount of fertilizer N applied by the value of N credits from green manures, legume crops grown in the previous year, compost and animal manures, and soils with more than 3 percent organic matter. The total amount of N from fertilizer and other credits should be 100 to 150 pounds per acre. Harvesting "New" potatoes can be dug by hand from the sides of hills for continual harvest for fresh market sale, but they do not keep as well as a mature tuber. New potatoes can also be once-over harvested in sections at a time, but the chain conveyors can blemish the soft skins of these immature tubers. Storage potato market life can be lengthened by preventing sprouting of potatoes in storage; use maleic hydrazide (Royal MH-30) according to label directions one week after blossoms fall. For varieties and conditions where flowering does not occur, apply four to six weeks before potatoes are mature and ready for harvest. Make only one application. Apply when no rain is expected for 24 hours. Potatoes treated with maleic hydrazide cannot be used for seed because sprouting will be inhibited. Follow label directions. Storage potatoes benefit from uniform maturation for mechanical harvest. This can be accomplished by killing the vines with a labeled herbicide. Once vines are down and dried, mechanical harvest can begin with chain-conveyor diggers. The labeled vine-killing herbicides are listed below, along with instructions.

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