Farmers depend on natural resources—particularly water and nutrient-rich soil— to grow their food and feed the planet. Climate change is already changing the availability of these resources and farmers now need to explore new techniques and technologies to make their crops sustainable.
Jerry Hatfield, a laboratory director at the U.S. Department of Agriculture, studies the role of natural resources in agriculture. He presented his research at the 2014 AAAS Annual Meeting in a talk on Sunday Feb. 16 entitled, "Natural Resources: The Overlooked Component in Food Security and Sustainable Agriculture."
AAASMC: You are giving your talk as part of the AAAS seminar on "Research and Development for Sustainable Agriculture and Food Security." What agricultural effects are already resulting from climate change? What effects do you predict will occur in the future?
Jerry Hatfield, professor and laboratory director at the United States Department of Agriculture: Throughout the history of agricultural production, we have had the effects of variable weather and climatic cycles on production. This has caused variation in production among years and across different growing regions. These changes are evident when you look at the long-term trends in crop production. If you examine the corn yields for the United States since 1950, you find there are periods in which there was very little variation among years during the 1950-60s and again in the late 1970-90s. Between these "quiet" periods there is a large degree of variation, and it appears we are entering into a period of larger variation again. These yield variations are primarily due to variation in precipitation (drought, with 1988 and 2012 as recent examples; flooding in 1993) and exaggerated by cool springs or hot summers.
One of the most striking examples is the large shift in corn and soybean production into North and South Dakota. This has occurred over the past five years and areas which were once predominantly wheat and sunflower are now corn and soybean. This is a result of warmer temperatures and an increase in precipitation.
The largest effect in the future will be the increase in variation in production at a local, regional and national scale. The increased variation in climate will cause more variation in production. The decrease in summer precipitation may lead to changes in crop rotations to favor crops which grow in the early spring and summer and mature before the late-summer dry periods occur. The increases in temperature extremes will also cause more variation in production. If high temperature extremes occur during pollination then very severe yield reductions could occur.
AAASMC: In the summary of your talk, you refer to increasing the efficiency of using water, solar radiation, and nutrients in agriculture. Do you see more promise in increasing efficiency through genetic engineering of plants or through adaptation of agricultural methods?
Hatfield: Increasing the efficiency of water, solar radiation, and nutrients will be a combination of genetics and management. We refer to this effect as the G x E x M complex, which is the genetic by environment by management interaction. There will not be any one single process or component of the overall system we will be able to change [to] increase efficiency. For example, water-use efficiency (WUE) is the grain yield per-unit-of-water transpired by the crop. We can affect WUE through changes in genetics but more importantly by how we manage the water in the soil profile; however, if we have a crop variety which does not grow deep roots to collect this water, its efficiency will be diminished. I believe that increased efficiency will come from understanding the G x E x M complex because it will help us determine how to select plants for given environments but also how to utilize adaptation practices to alleviate the stresses during the growing season. This is the area in which we can have the largest impact on food security and one of the more promising [ways] to help agriculture respond to climate change.
AAASMC: When it comes to restoring nutrients to soil, do you see any promise in the increasing attention paid to composting and anaerobic digestion?
Hatfield: There is an emerging concept in agriculture called soil biological fertility in which we consider the role of soil biology in increasing nutrient cycling and release in the soil. This begins by considering what it takes to feed and promote soil biological activity and then letting the biological system recycle the nutrients in the soil. Composted material is one source of nutrients which can help biological activity and even the residue from anaerobic digestion because this material is basically digested biological material. Both of these sources provide a readily available food source for the soil biological system. We have large amounts of manure in the United States, and developing methods to more effectively capture and return these to the soil would be great value.
An added benefit to adopting this philosophy would be increase in soil organic matter, which in turn would increase the soil water-holding capacity, meaning the soil reservoir for water would increase [thus] making more water available to the crop. This would provide us with a method to increase climate resilience in our cropping systems which rely on precipitation for their water supply.
AAASMC: Do you believe increases in agricultural efficiency will result more from local action or changes in federal policy? What types of actions or changes do you believe are necessary?
Hatfield: Increases in agricultural efficiency will come from producers understanding the dynamics of cropping systems and how these can be used to improve efficiency. That is why we are trying to utilize the G x E x M concept as a unifying principle to understand how to improve efficiency and work with producers to apply these concepts in their operations. The primary action is for producers to realize that there are a large number of possibilities to improve efficiency, but they are going to have to be willing to change some of their practices. One of the major components in this effort is to improve the soil as a water reservoir through improved infiltration and water storage, coupled with residue-management practices which reduce soil-water evaporation and increase the amount of water available to the crop. This will increase water-use efficiency of cropping systems. Adoption of widespread conservation practices as a federal policy would benefit cropping systems by improving water management and reducing erosion.
AAASMC: What can farmers do now to protect their crops from the impacts of climate change?
Hatfield: Farmers have already adopted a number of practices to protect their crops. Some of the simple ones are using a variety of different corn hybrids across a farm to avoid the risk of just planting one particular maturity class. This spreads out the time in which the crop matures and avoids the potential exposure to hot or dry periods. Producers also change planting dates to avoid periods of stress during critical growth stages. However, this remains a guess because we can't accurately [predict] the weather during the growing season, which means that protection has to come from selecting genetic material which can provide resistance to stress during the growing season.
One of the primary ways in which farmers protect their crop from climate is through irrigation. Supplying water to the crop to offset the irregularities of rainfall alleviates one of the major impacts of climate change.