Plants, Water, and Landscapes

When it is warm and dry, you have probably noticed that plants require a lot of water to stay healthy, but did you know that only 10% of the water a plant receives actually remains inside of it to support life processes? Plants lose the other 90% of their required water (liquid) as water vapor (gas) to the atmosphere through a process known as evapotranspiration (ET), which is a combination of water the plants emit from pores in their leaves (transpiration) and water that evaporates from soil and plant surfaces.  ET uses a tremendous amount of solar energy, and this energy use coupled to the plant water use is referred to as the water-energy cycle of a landscape. When humans alter the composition of plants across a landscape (i.e. urbanization, agriculture), they also alter the water-energy cycle. 

Water – The Critically Important Resource for our Nation’s Food Security

In this current blog series we have been featuring graduate student research on potatoes in Wisconsin, and so far we have covered research in plant breeding, seed production and pest management. We are concluding this student series with 4 blogs on a topic that has emerged as one of the most critical issues facing agriculture today—water.  Will there be a sufficient supply in the coming decades to maintain the productivity and security of our nation’s food supply while guaranteeing the long-term sustainability of the resource in future generations for all to enjoy?

In Wisconsin, the issue of water and its availability is particularly acute in the Central Sands region, which is one of the top five vegetable growing regions in the nation where potatoes, sweet corn, green beans, peas, carrots and cucumbers all rank near the top of U.S. production.  The foundation of the region’s productivity lies in its geological history, which began during the glacial ice age that encompassed Wisconsin over 15,000 years ago.  The Central Sands is a large and relatively flat glacial outwash plain that deposited abundant sandy soils—ideal for vegetable production—and is underlain by a deep groundwater aquifer that provides the water, vital for crop growth and productivity.

The region covers nearly 1,400 square miles and now supports 200,000 irrigated acres, but prior to the 1950s it was not farmed because there was no efficient way to utilize the abundant water supply and as such, much of the area remained undeveloped.  In the mid-1950s, however, this largely unused, resource-poor area was transformed rapidly when modern irrigation technology became available and affordable due to aluminum supplies increasing after World War II.  This raw material provided farmers the ability to build and deploy the center pivot irrigation systems that could, for the first time, deliver water to 160 acre crop fields in less than 24 hours.  This quickly transformed the regional economic landscape into a thriving specialty crop production area which now supports a $6.4 billion food production industry and generates close to 40,000 jobs within the state of Wisconsin.  

The Battle against Late Blight, From the Irish Potato Famine to the New Millennium

While hard to believe, the Late Blight pathogen that caused the Irish potato famine in the 1840s and 1850s and caused the starvation deaths and forced migration of hundreds of thousands across Europe, is still a major concern in food production worldwide. The fungus-like organism, Phytophthora  infestans, is aggressive and can cause disease that can rapidly destroy whole fields of potatoes  and tomatoes. This centuries old threat is still with us and causes major concerns for potato growers in Wisconsin each year!

The pathogen can be spread quickly over whole areas by wind movement of its spores from infected source plants. These are either brought into the state as already infected tomato transplants or seed potatoes or can develop locally from un-harvested tubers or crop waste that survive freezing.  Because it can spread so rapidly under cool moist conditions, Late blight is considered a ‘community disease’ that can affect both commercial growers and home gardeners alike. Crop fields must therefore be monitored   early to detect symptoms and potential disease sources.  Growers ensure that seed is disease-free to prevent the introduction of the pathogen into the fields. They control potato volunteers and nightshade weeds that may be infected in and around production fields. And, by WI state law, growers, homeowners and garden centers are required to destroy all disease sources by May 20th before the start of the growing season.