|
|
Crop rotations may help carbon footprint
A report released last November from the U.S. Department of Agriculture concludes that climate change is already affecting U.S. agriculture, land resources, water resources and biodiversity. The report, The Effects of Climate Change on U.S. Ecosystems, identifies many of the effects of climate change on agriculture and other ecosystems in the U.S. over the next several decades. The USDA report was done in cooperation with the University Corporation for Atmospheric Research and the U.S. Global Change Research Program (USGCRP). Some of the report's main points: --Grain and oilseed crops will mature more rapidly, but increasing temperatures will heighten the risk of crop failures, particularly where precipitation decreases or becomes more variable. --Marketable yield of horticultural crops (such as tomatoes, onions, and fruit) are more vulnerable to climate change than grains and oilseed crops due to the high sensitivity of their quality and appearance to climate factors. --Livestock mortality will decrease with warmer winters but this will be more than offset by greater mortality in hotter summers. Hotter temperatures also will result in reduced productivity of livestock and dairy animals, due to changes in consumption and lower pregnancy rates. --Weeds that can thwart agriculture production grow more rapidly under elevated atmospheric CO2, extend their range northward, and are less sensitive to herbicide applications. --Disease and pest prevalence will escalate as a result of shorter, warmer winters, challenging crop, livestock, and forest systems. --The trends toward reduced mountain snowpack and earlier spring snowmelt runoff in the Western U.S., and toward increasing drought in the West and Southwest, imply changes in the availability of water and a need to monitor the performance of reservoir systems with implications for water management and irrigated agriculture in that region. --Climate change is inducing shifts in plant species in rangelands, favoring the establishment of perennial herbaceous species that reduce soil water availability early in the growing season. Shorter winters, however, decrease the need for seasonal forage reserves. Critics The report does have its share of critics. Delegates at the American Farm Bureau Federation annual meeting Jan. 12 unanimously approved a special resolution to strongly oppose "cap and trade proposals before Congress" and strongly support "any legislative action that would suspend (the Environmental Protection Agency's) authority to regulate greenhouse gases under the Clean Air Act." The resolution asserted that proposed cap and trade legislation would result in significantly higher production costs for farmers, and that potential benefits of agricultural offsets are far outweighed by the costs. "The administration's economic projections show that the proposed cap and trade legislation would result in planting trees on 59 million acres of crop and pasture land thereby damaging the capability of U.S. agricultural producers to feed a growing world population and create the conditions for (hiking) consumer food prices," according to the resolution. "Cap and trade legislation would eliminate jobs, and could result in the loss of 2.3 million jobs in the U.S. over the next 20 years." The delegates cited recent developments in the climate change debate as reasons to re-emphasize their opposition. "E-mails made public call into question just how unsettled the science really is on climate change and demonstrate the unwillingness of many of the world's climatologists to share data or even entertain opposing viewpoints," the delegates stated. "The recently completed Copenhagen summit resulted in demands for the U.S. to transfer billions of dollars to the developing world to fight climate change, but produced no meaningful agreement." Still, despite the debate, research goes on into how farmers can successfully manage to use whatever type of legislation may confront them to their benefit. Part of cap and trade legislation foreseen by members of Congress includes payments to producers who are successful at carbon sequestration in their operations. Increasing carbon According to officials at the Soil Carbon Center at Kansas State University, through carbon sequestration, atmospheric carbon dioxide levels are reduced as soil organic carbon levels are increased. If the soil organic carbon is undisturbed, then it can remain in the soil for many years as stable organic matter. This carbon is then sequestered, or removed from the pool available to be recycled to the atmosphere. This process reduces CO2 levels in the atmosphere, reducing the chances of global warming. It has been estimated that 20 percent or more of targeted CO2 emission reductions could be met by agricultural soil carbon sequestration. There are several practices that can increase carbon sequestration, including: --No-till or reduced-till; --Increased crop rotation intensity by eliminating summer fallow; --Buffer strips; --Conservation measures that reduce soil erosion; --Using higher residue crops, such as corn, grain sorghum, and wheat; --Using cover crops; and --Selecting for varieties and hybrids that store more carbon. Dr. Humberto Blanco, assistant professor of soil management at the Kansas State University Agricultural Research Center-Hays, is the latest lead scientist in a 34-year long field trial measuring soil quality in tillage treatments. Blanco explained his work in the field trial during the 2009 KSU-ARCH fall field day. Primarily, Blanco's predecessors had been exploring no-till and conventional tillage practices in various rotations to measure reduction in soil erosion. Now, with the added thoughts on climate change, use of tillage techniques for carbon sequestration is being studied. "In many cases, at research centers like ours, they don't have a lot of data on long-term residue research. Usually, at places like here you look at continuous wheat and how it doesn't hold as much moisture as wheat-fallow," Blanco said. "But now you have to look at this through different angles. Not only should we look at crop production, but also wind erosion and carbon sequestration." Long-term testing Every year and at every location across the world where research takes place, Blanco said, there are changes in how crops are looked at. At his previous posting at Ohio State University, Blanco said every year came a change in experiments. With the change in procedure came changes in outcome. "That's the difference here," Blanco said. "With a long-term experiment, you have an opportunity and an avenue to explore different things." On a test field, at KSU-ARCH, stand long-term rotations including sorghum-fallow, continuous sorghum, wheat-sorghum-fallow, wheat-fallow-fallow and continuous wheat in both conventional and no-till. Three additional rotations are in strictly no-till: continuous wheat, wheat-sorghum-sorghum-fallow and wheat-wheat-sorghum-fallow. The Hays research center also shares data with USDA's Agricultural Research Service Central Great Plains Research Station, at Akron, Colo., which also has been conducting long-term rotation studies, but for only 19 years. The Akron station, Blanco said, has had rotations of wheat-fallow, wheat-corn-fallow, wheat-corn-millet and a perennial grass under no-till. "These are all out to look at not only production, but carbon sequestration, as well," Blanco said. "If you really want to look at carbon sequestration, and get a real understanding, then long-term experiments such as this are really the only way to go." Study results Blanco's early research has found that continuous wheat is consistently higher than sorghum-fallow or wheat-fallow at increasing carbon. "You might say that continuous wheat is the best cropping system for crop production. All I'm saying is an intensive rotation can increase carbon," Blanco said. "You can look at wheat-sorghum-sunflowers-corn, as long as you maintain the soil with corn you will return more biomass every year and store more carbon each year." Storing more carbon can help the soil's structure, Blanco explained, as it assists with water retention and with other biological processes. In general, continuous cropping systems in no-till improve the structure of soil, increasing net soil aggregates. "The old system of plowing and tilling are great for short-term benefits. Now there is a tendency to grow crops while we conserve water and soil resources. There are short- and long-term impacts," Blanco said. "When you plow you reduce compaction, but you destroy the aggregate, the natural buffering capacity of the soil. You eliminate crusting when you plow, but there will be more crusting in the future." While Blanco mentioned a poor system for storing water--continuous wheat--as the best for storing carbon, the rotation considered among the best for moisture retention doesn't do as well for retaining carbon. "If you want to store carbon, a wheat-sorghum-fallow system is the worst. Why? In 30-inch rows of sorghum, there's not much residue but in wheat where the spacing is 8 inches, most of the surface is covered," Blanco said. "That reduces erosion and improves structure compared with sorghum-fallow. "When the soil is near saturation, continuous wheat stores more water than sorghum-fallow. Why is that? Because of carbon accumulation," Blanco said. The key, Blanco said, is to use no-till and intensive crop rotations together in a way to increase carbon sequestration. "Carbon sequestration improves certain physical qualities of the soil. This increase in carbon can offset some of the risks of compaction. Obviously, no-till works when there is residue on the soil. Remove the residue and soil erosion can be as high as that on plowed soil," Blanco said. "No-till works when there is proper residue. Residue is a like a nice blanket for soil. Remove the blanket; the soil will freeze. "I know that a fallow period can increase crop yields because it stores water; but, if you are interested in conserving soil and water, reducing water pollution, in carbon sequestration, in sustained crop production, you need to reduce these fallow periods." Blanco still suggests using wheat-sorghum-fallow as a rotation on the High Plains as a balanced system for moisture retention and carbon sequestration. "I, for one, am hoping to get paid for carbon sequestration," Blanco said. "We can, in some cases, probably eliminate fallow and get extra income from carbon credits." Larry Dreiling can be reached by phone at 785-628-1117, or by e-mail at ldreiling@aol.com.
Copyright/Privacy
Copyright 1995-2011. High Plains Publishers, Inc. All rights reserved. Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com |
|
