Agriculture has both been a cause of climate change and has been impacted by climate change.
Fossil fuel use, release of carbon from intensively farmed soils, greenhouse gas emissions from concentrated animal feeding operations (CAFOs), poisoning of water and soil due to use of toxic chemicals, depletion of topsoil and organic matter due to erosion and intensive cropping practices and pollinator scarcity as a result of insecticides which have proven detrimental to beneficial insects as well as insect pests are some of the causative contributions modern ag practices have made. Intensive fossil fuel- and chemical-dependent systems of growing food have and continue to contribute to the climate changes which will continue to impact all food production.
So agriculture is changing. It has to.
Some changes are technological, utilizing precision practices to better target and utilize resources. Some changes rely on artificial environments with controlled growing condition (which come with their own concerns). Other changes involve minimizing the use of fossil fuels, practicing no-till growing, keeping soil covered and using companion planting, crop rotation and other low-impact means of promoting soil, crop and overall environmental health.
Below are a few innovations being studied now to lessen the impact vegetable growers make on the environment, and to help growers adjust to erratic and continually changing growing conditions.
At the University of Kentucky, graduate student Sarah Clark is studying the use of essential oils as a pest management tool in Brassica crops. Her field trials involve the use of three different essential oils, in varying concentration, to determine their efficacy in preventing damage from harlequin bugs and measure any negative impact in productivity or quality the use of these oils might cause the crop.
Harlequin bugs damage crops with their sucking and piercing actions. These highly mobile insects communicate through hormone signals, Clark said, which serve as a calling card to other harlequin bugs, resulting in thousands of insects congregating in areas where suitable host plants are growing. While pyrethroids can be used to control harlequin bugs, these chemicals also have a detrimental impact on pollinators and other beneficial insects.
Essential oils have “gained popularity in scientific research,” Clark said. Her field research aims to “figure out the proper concentrations … so that you (farmers) can get the most benefit.”
These oils work by repelling insects with their strong smell or by coating the plant and making it very distasteful to the insect pests. There is also mounting evidence that some essential oils can have insecticidal properties, killing the insects, she said.
A concern with essential oil use is phototoxicity. Clark hopes that her field research will help determine if and when phototoxicity occurs in Brassica crops with essential oil usage and will quantify the degree of damage to the plant. Not only will she measure visual damage; she will also measure any resulting yield loss and changes in crop characteristics, such as head size or growth rate, that can affect farm productivity.
At the University of Minnesota, a three-year trial led by Dr. Cindy Tong, in conjunction with farmer Erik Heimark of Maple Ridge Produce, has focused on the ongoing and increasingly problematic issue of fields being too wet for spring planting of vegetable crops, delaying planting dates. Planting in wet soils damages soil structure, and any crops that do get planted face sub-optimal growing conditions.
In trials, raised beds covered with plastic mulch are formed in the fields in autumn and readied for spring planting. Then a cover crop – in this case, rye – is grown in between the rows to help absorb excessive water from heavy rains. Rye, vetch and a rye/vetch combination, as well as landscape fabric and bare soil, were all researched.
Rye provided the best results for absorbing spring rain and getting farmers into the fields to plant crops in early spring. The rye was seeded in early autumn for best results. Rates of 1.5 to three bushels of seed per acre for winter rye were effective. Rye or other cover crops can be periodically mowed or cut at heading.
Heimark has a field of clay soil which has been difficult to utilize for spring-planted crops. He normally uses landscape fabric between raised bed rows covered with black plastic, but the fabric holds a lot of water under it and keeps the moisture trapped, causing issues with muddy fields. Although it was not a wet year when he participated in the rye cover crop trials, he believes that the rye got him into the fields a bit earlier than he otherwise could have gained access. He intended to crimp the rye, but time constraints led him to mow it instead.
While black plastic is the standard for most crops grown in raised beds, a change in plastic coloring might be warranted by climate change in order to reduce the impact of added heat on the soil and the crop – white or light-colored plastics retain less heat. Natural mulches, such as rolled small grain cover crops, are also an option for reducing soil and crop temperatures.
Shading structures, kaolin clay or other reflective materials applied to the crop, or planting cultivars which are more heat tolerant, may be warranted, according to information from the University of Delaware. As growing conditions change, some cultivars won’t be able to complete their lifecycle – perhaps not having enough time to ripen or suffering from adverse effects of hot temperatures or prolonged periods of weather which are too wet or too dry.
Biodegradable plastic mulch is another climate smart option, as it degrades into the soil after being tilled in at season’s end. According to Shuresh Ghimire, UConn Extension agent, biodegradable plastic mulch trials are being conducted as a means of coping with climate change and work by modification of the growing microclimate. Biodegradable mulch is used in the same manner as plastic mulch. Because it does not have to be removed, it’s less labor intensive and can assist in getting a cover crop planted in a timely fashion.
If pollinators and crop flowering are out of sync due to changes in climate, both the pollinator population and the crop’s yield will suffer. Heat stress causes pollination problems. Nighttime temperature increases have been found to inhibit pollination in snap beans, according to University of Delaware researchers. Heat can also lower photosynthesis rates, reduce yield, increase internal and external crop defects and abiotic diseases and cause stunting of fruits.
As climates change, new pathogens emerge. Pathogens can migrate along with the changing climate, causing disease problems in crops in regions where they have not previously been problematic.
Changes in growing seasons, temperature and humidity norms, water availability and intensity of rain events and migration of pest populations as climates are altered are a few of the consequences that vegetable growers are now facing in real time. Mitigating climate change requires multiple approaches, as climate change doesn’t affect just one thing. It impacts everything.