Gordon Johnson, Extension Ag Agent, Kent Co.; email@example.com
We have had a considerable amount of blackheart in Delaware potatoes this year. This is a disorder related to low oxygen conditions. Heavy rainfall in August, especially on our heavier silt loam soils, set up conditions for blackheart to develop. In soils that are flooded or that stay saturated for long periods of time, oxygen diffusion into potato tubers is restricted (oxygen diffusion is much slower through water than soil air spaces). Lack of oxygen to the tuber interior causes interior tissue to die and ultimately turn brown, purple, or black. When dug, tubers may appear normal on the outside, but when cut reveal the dead areas. This makes grading very difficult. With each truckload coming into the packing shed, a sample of tubers must be cut open and if a significant percentage show blackheart, the load is rejected.
Blackheart can also occur when soils are compacted, restricting air movement; when soils are hot and tubers are respiring heavily, using up more oxygen that can diffuse through the soil; and in storage or shipping when piled too high or stacked too closely for long time periods, again restricting oxygen. Managing low oxygen blackheart in the field requires attention to drainage, forming high loose ridges around tubers (avoid cultivating and ridging when soils are wet), managing field traffic to limit compaction, and harvesting in a timely manner, targeting fields with higher potential for blackheart to be dug first. Low areas in fields may have to be examined (samples cut open to see the percent of blackheart) and passed over during harvest.