We have had widespread flooding in vegetable crops in May due to heavy and extended rains. Soils in some field areas have remained waterlogged for several days. Over a 10-day period from May 12, 2018 at our Georgetown, Delaware Research station, 7.5 inches of rainfall fell. There were 4 days with rainfall over 1 inch and one day receiving 3 inches of rain. Many surrounding areas had over 10 inches of rain during this period.
by Gordon Johnson
Climate scientists predict that extreme weather events will become more common on Delmarva over the next several decades. This will present additional challenges for vegetable growers related to flooding, wet weather diseases, nutrient losses, ability to do timely harvests, field compaction, other wet soil issues, and resulting crop losses.
In 2018, initial plantings of watermelons and other fresh market vegetables have been made; peas are nearing harvest, and significant acres of pickles, snap beans, and sweet corn are in the field. Many processing vegetable fields have already had significant crop losses (sweet corn, snap beans, peas) due to flooding.
In flooded soils, the oxygen concentration drops to near zero within 24 hours because water replaces most of the air in the soil pore space. Oxygen diffuses much more slowly in water filled pores than in open pores. Roots need oxygen to respire and have normal cell activity. When any remaining oxygen is used up by the roots in flooded or waterlogged soils, they will cease to function normally. Therefore, mineral nutrient uptake and water uptake are reduced or stopped in flooded conditions (plants will often wilt in flooded conditions because roots have shut down). There is also a buildup of ethylene in flooded soils, the plant hormone that in excess amounts can cause leaf drop and premature senescence.