The photo below was taken in our field of radishes and turnips on Wednesday, two full days after our last rain shower. As you can see, the wheel tracks where the tractor has driven still contain streams of water draining down from the mountain to the east of the fields. The small seedlings attempting to grow there are turning yellow and their growth has slowed remarkably. I knew it had something to do with all the wet soil, but the specific biochemical reasons I couldn't explain. So I did some research.
As explained by Vegetable Growers News, "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."
After another ten days of frequent showers and infrequent sun, I noticed this wilting phenomenon on our kale as soon as the sun came out and temperatures warmed up on Tuesday. Our eggplants are exhibiting the signs of premature senescence with leaves turning yellow and dropping to the ground. Of course a plant can't produce abundant tasty fruits without its leaves!
"Climate scientists predict that extreme weather events will become more common in the mid-atlantic 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, and resulting crop losses."
Last week while driving the farm truck between fields I caught on the radio an episode of Science Friday with an agriculture scientist and microbiologist discussing the "imperative of the soil." We are all taught in school the importance of protecting the environment to maintain clean air and water. The importance of soil, and the dire consequences of soil loss across the planet, are less recognized. As climate change alters rainfall patterns and exacerbates extreme weather events, soil loss due to erosion will increase and the productive quality of soils will be reduced by the physical and chemical affects of too much moisture. Additionally, increasing temperatures are changing the soil micro-biology and carbon-holding capacity of soils. Now, more than ever, it is imperative that we develop and implement agriculture practices that balance crop production with soil protection. Doing so profitably has always been a challenge and will only become more difficult as climate change takes its toll. Its certainly going to require adaptation at the farm level, and also among consumers of fresh food. We can't do it without you!