We saw record-breaking rainfall in July, which was quite a change from an exceptionally dry May, along with the drought we endured last season. Of course, too much rain can cause several problems of its own – from foliar disease, to increased weed growth, to soil compaction – it can cause quite the headache.
Below is an excerpt from the UMass Extension newsletter Vegetable Notes. They recently explained just how detrimental flooded fields can become for crops:
“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. In general, if flooding or water logging lasts for less than 48 hours, most vegetable crops can recover. Longer periods will lead to high amounts of root death and lower chances of recovery. While there has been limited research on flooding effects on vegetables, the following are some physiological effects that have been documented:
- Oxygen starvation to vegetable roots will cause roots to cease to function resulting in plant collapse with limited recovery potential.
- Oxygen starvation in root crops such as potatoes will lead to cell death in tubers and storage roots. This will appear as dark or discolored areas in the tubers or roots. In carrots and other crops where the tap root is harvested, the tap root will often die leading to the formation of unmarketable fibrous roots.
- Ethylene buildup in saturated soil conditions can cause leaf drop, flower drop, fruit drop, or early plant decline in many vegetable crops.
- Leaching and denitrification losses of nitrogen and limited nitrogen uptake in flooded soils will lead to nitrogen deficiencies across most vegetable crops.
- In bean crops, flooding or waterlogging has shown to decrease flower production and increase flower and young fruit abscission or abortion.
- Lack of root function and movement of water and calcium in the plant can lead to calcium related disorders in plants. There is a potential for higher incidence of blossom end rot in tomatoes, peppers, watermelons, and other susceptible crops when fruits are forming and soils are saturated.
Low lying areas of fields are most affected by excess rainfall. However, cropping practices can also increase water standing. In vegetables, field compaction will reduce water infiltration leading to increased crop losses in wet weather.”
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Thankfully, the soil at Stearns dries out quickly and we rarely see standing water or flooding in the fields. While we are concerned about diseases that spread easily in hot, humid weather, we are fortunate that our crops are not routinely sitting in water. Moving forward, we continue to keep an eye on low-lying sections of the fields that may show signs of poor drainage or plants that may be nutrient deficient.
Until next time,