Conventional agriculture production relies heavily on fossil fuels, particularly in its ability to provide energy at a low cost. However, the uncertain future of fossil fuel availability and prices point to need to explore energy efficiencies in other cropping systems.
Most of the U.S. Corn Belt relies on a two-year rotation of corn and soybean with heavy inputs of fertilizer, herbicides and pesticides derived from fossil fuels to achieve high yields keep costs low. Matt Liebman, Michael Cruse, and their colleagues at Iowa State University conducted a six-year study to compare energy use of a conventionally managed corn and soybean system with two low input cropping systems that use more diverse crops and manure applications, but also use less fertilizer and herbicides. The results were published in the May/June 2010 edition of Agronomy Journal, published by the American Society of Agronomy.
The two input systems consisted of a three-year rotation of corn-soybean/small grain/red clover and a four-year rotation of corn-soybean-small grain/alfalfa-alfalfa. Between 2003 and 2008, nitrogen fertilizer inputs in the 3-year rotation decreased 66% and decreased 78% in the 4-year rotation. Herbicide use decreased 80% in the three-year rotation and 85% in the four-year rotation. Despite the energy input reduction, corn and soybean yields matched or exceeded the conventional system yields.
Did the application of manure decrease the fossil fuel energy costs? Manure prices are dependent on local economic conditions, but the two low-input systems used 23% to 56% less fossil energy than conventional systems. To analyze the energy and economic costs of manure application, the researchers used two approaches. One where manure was a waste product of live stock and essentially free of cost except for the energy used in its application, and a second approach as if the costs of manure were the same as commercial fertilizers. As a low economic input, manure can return $249 per acre, or $28 to $38 under high economic input for four and three-year systems, respectively.
Most of the fossil energy input for all systems was from grain drying and handling. Conditions in northern latitudes, where farmers have limited time to allow grain to dry in the field, make it difficult to reduce this cost. The researchers point out, however, that growing corn less frequently in a rotation sequence can reduce the need for grain drying with fossil energy.
The three and four-year rotation plans rely on agriculture systems where livestock feeding, manure application are integrated into crop production practices. "Iowa has a long history of mixed crop and livestock farming, although these operations do require more management and labor," said Liebman. "If fossil energy costs rise steeply, we may see more of them again."
While fossil energy inputs may decrease with manure application and increased crop rotation, the opposite trend is true for labor inputs. A two-year rotation required 41 minutes per acre per year, with a three-year rotation increasing labor 54%, and a four-year rotation requiring 91% more labor. However, the increases in labor were mainly in parts of the year not associated with corn or soybean production activities.
The researchers conclude that low energy prices and high wages contributed to the adoption of the conventional two-year corn/soybean rotation. Fossil fuels offset labor costs and allow net economic returns to remain constant. If demand from ethanol or overseas grain markets increase, or if biofuels from corn stover become economically viable, Midwest cropping systems may continue on a trend of less diversity and more corn. However, if fossil energy prices rise without an increase in crop value, diversified cropping systems may become more preferable.
"It's hard to predict the exact details of what the future will bring us," said Liebman. "But results of this study show that we do have options for maintaining high farm productivity and profitability while substantially reducing our dependence on fossil energy."
The research team was funded by the Leopold Center for Sustainable Agriculture and the U.S. Department of Agriculture. It is expanding its activities into measurements of effects of the different cropping systems on water quality, greenhouse gas emissions, and soil carbon and nitrogen dynamics.
The full article is available for no charge for 30 days following the date of this summary. View the abstract at https://www.agronomy.org/files/publications/agronomy-journal/abstracts/102-3/aj09-0457-abstract.pdf.
A peer-reviewed international journal of agriculture and natural resource sciences, Agronomy Journal is published six times a year by the American Society of Agronomy, with articles relating to original research in soil science, crop science, agroclimatology and agronomic modeling, production agriculture, and software. For more information visit: http://agron.scijournals.org.
The American Society of Agronomy (ASA) www.agronomy.org, is a scientific society helping its 8,000+ members advance the disciplines and practices of agronomy by supporting professional growth and science policy initiatives, and by providing quality, research-based publications and a variety of member services.
Filling intercropping info gap
16.11.2017 | American Society of Agronomy
Climate change, population growth may lead to open ocean aquaculture
05.10.2017 | Oregon State University
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses