When potatoes grow too fast, the inside of the tuber tears apart as seen in this photo. This occurs when potatoes are improperly watered, improperly fertilized with nitrogen, or planted too far apart. Hollow heart not only results in the loss of edible flesh due to the need to cut out the discolored tissue before cooking, but can contribute to rot when hollow heart cracks to the surface of the tuber.
Fertilizer: Applying an excessive amount of organic matter high in nitrogen, or over applying an organic or synthetic nitrogen product can increase hollow heart due to an excessive amount of nitrogen being available during the tuber enlargement stage of growth. A soil test is important in determining the fertilizer needs of potatoes and your other vegetable crops.
Nitrogen products, whether organic (http://www.coopext.colostate.edu/TRA/PLANTS/Organic_Fertilizers.pdf ), or synthetic, should be applied in split applications and not all at one time. Once you know the amount of nitrogen required, one-third to two-thirds is typically applied after the plants emerge with the remaining required amount applied 60 days after planting. Smaller but more frequent applications of nitrogen are recommended.
A soil test will tell you what nutrients in addition to nitrogen are required. Other than nitrogen, these nutrients will need to be applied and worked into the soil prior to planting. If you want a soil test analysis run on your soil, you can submit a sample through our office. We will need to receive this form along with your sample(s). I will provide you recommendations on what you need and how the nutrients should be applied based on the crop you plan on growing. A soil test will also indicate if you have a salt problem you should be concerned about. We can test your soil and irrigation water for salts at no charge at our offices in Mesa, Delta, and Montrose Counties.
Watering: Potatoes should not be allowed to drop below 60-65% of available soil moisture. 75 – 85% soil moisture is preferred after the plants emerge from the soil and before they start to set tubers. When the plants start to set tubers, the soil moisture content should be maintained between 80 and 90%. The best way to determine when tubers start to set is by digging into the soil and checking the stolon tips to see if they are starting to swell. This usually occurs when the plants start to flower.
To determine the moisture content of the soil, you can use the soil ball technique (http://www.coopext.colostate.edu/TRA/PLANTS/soilmoist.pdf ) or by checking the lenticles. Lenticles become enlarged when soil moisture is excessive. See http://swiftsgardeningblog.blogspot.com/2011/02/potatoes-have-lenticles.html for an explanation of lenticles on potatoes.
Spacing: While the spacing of potatoes varies somewhat with variety, row width is typically 30 to 36 inches. For cultivars with a tendency to develop oversized tubers or set few tubers, such as Katahdin and Kennebec, seed pieces should be spaced 6 – 9 inches apart within the row. For cultivars that produce a heavy set, such as Norchip, seed pieces should be spaced 11 – 14 inches apart in the row. Be sure to check the production characteristics of the cultivar you are planting to determine the required spacing. Your local nursery or garden center should be able to provide you guidance on spacing for the varieties of seed potatoes they sell.
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