February 01, 2009
by Meyer Sosland
As the earth’s population grows over the next century, the demand for food will increase at a dramatic rate. It must be decided what is the most effective and sustainable way to produce that food. Field to Market: The Keystone Alliance for Sustainable Agriculture — a collaborative stakeholder group of producers, agribusinesses, food and retail companies and conservation organizations — is working to develop a supply-chain system for agricultural sustainability.
The group compiled information to measure outcomes for five environmental indicators — land use, soil loss, irrigation water use, energy use and climate impact (greenhouse gas emissions) — and track productivity (yield per acre) of corn (maize), cotton, soybeans and wheat in the United States, one of the world’s key grain-producing nations. In 2007, these crops comprised 69% of the 305.7 million acres of U.S. agricultural crops harvested and had a combined crop value of $98.12 billion.
After compiling and analyzing this information, the Alliance released its Environmental Resource Indicators report on Jan. 12 at the American Farm Bureau Federation’s annual meeting. The study covers the years 1987-2007.
"U.S. agricultural production has been very effective in reducing its use of energy and water and in reducing its soil loss," said Marty D. Matlock, a professor at the University of Arkansas, who participated in the study. "These are positive trends."
The Alliance commented that nearly all estimates of future demand for agricultural goods suggest a need to at least double agricultural production by 2050 to maintain adequate supplies for a growing world population. This "first-of-its-kind" study is viewed by the organization as its first step to help it define sustainable agriculture and improve upon it to help future generations meet their needs.
IMBALANCE The Alliance’s study of corn, soybeans and wheat indicated that while the first two crops have seen increases in demand and production efficiency, the latter has lagged behind.
The Alliance’s report noted that over the past three decades corn (maize) has continued to rise in importance in the mix of U.S. crops. In 1983, corn represented 19% of total U.S. cultivated area. Corn hit its current peak of 29% of the total U.S. cultivated area in the 2007-08 marketing year. Technology advancements have allowed corn to be planted farther north and south of the "Corn Belt" every year.
The Alliance noted that corn has replaced millions of less productive sorghum acres over time. The continued growth in share of the U.S. and world feed grain market has made corn the standard for livestock feed ingredients. More recently, the U.S. ethanol industry has adopted corn as its predominate feedstock, accounting for nearly 25% of total corn demand in 2007 and contributing to sharp increases in land use for corn production during that year.
Over the 20-year period that the study was conducted, corn demonstrated a 41% increase in productivity. At the same time, corn’s planted area increased 21%, with a significant increase occurring in 2007. The Alliance said that corn’s productivity gains have allowed for a 37% reduction in the land needed to produce one bushel.
The report indicated that U.S. soybean demand has benefited from steady growth in both domestic demand (crush) and export demand for whole beans. The Alliance said domestic demand has increased over time due to increased meat consumption, particularly poultry and pork. A similar phenomenon has occurred in China, resulting in that country importing more soybeans for animal feed use.
These demand increases have led to a rise in soybean planted area from a low of 58 million acres in 1990 to a recent high of 75 million acres in 2006. Soybean productivity increased by 29% over the study period, while planted area for soybeans increased by 31%. The report showed that increasing yields have resulted in soybean land use per bushel decreasing by 26% over the past 20 years.
The report shows that U.S. wheat acreage has generally declined during that period due to acreage competition from other crops, primarily corn and soybeans. Minimal growth in yields has reduced wheat’s competitiveness with alternative crops and has contributed to the acreage loss (see related article on page 42). In the late 1990s and early 2000s, the impact of the low-carbohydrate diet caused consumption of bread, pasta, and other wheat-based products to decline in absolute and per-capita terms.
The report said that only in the last couple of years has there been an increase in domestic demand, albeit relatively small. Export demand has been highly variable over the years.
Wheat productivity increased 19% over the study period, while U.S. wheat land use decreased 24%. Land use per bushel was variable, with an average overall decrease of 17%.
SOIL LOSS According to the Alliance, soil loss above tolerable levels due to corn production has been significantly reduced in all regions of the U.S., with a 43% decrease in tons lost per acre. When combined with productivity advances, soil loss above tolerable levels per bushel of corn produced during the period 1987 to 2007 has decreased by 69%.
The soybean soil loss indicators (per acre and efficiency) have also improved dramatically over time, with a 31% reduction in soil loss per acre and 49% reduction in soil loss per bushel. The Alliance said this trend has coincided with significant changes in farming practices in states that grow the bulk of U.S. soybeans.
The indicator of soil loss for wheat made significant progress during the period 1987 through 1997 as soil loss above tolerable levels decreased from approximately four tons to two tons per acre. Reductions in the soil lost per acre have been relatively modest from 1997 forward.
WATER USE The average amount of irrigation water being applied per acre of corn has declined from about 450,000 gallons per acre to 400,000 gallons per acre in the most recent survey year (2003), with a 4% trend decrease overall. Irrigation efficiency per bushel has been variable over this time period, with a decrease of 27%.
Noting that irrigation use on soybeans is relatively limited, the Alliance said only 4% to 7% of the crop utilizes supplemental water. At about 260,000 gallons per acre per year, soybeans use much less water than corn and wheat. The amount of water applied per acre has changed very little over time, while water use efficiency per bushel fluctuated over time, showing an overall 20% improvement between 1987 and 2007.
Unlike the improvements seen in water use for corn and soybeans, the Alliance noted that water applied per acre of wheat increased 17% over the past 20 years from roughly 420,000 gallons per acre to 490,000. The portion of total planted area that is irrigated has varied from 5.5% to nearly 7% over the years. Irrigated wheat yields are nearly twice that of non-irrigated yields, a larger yield response than with many other crops.
ENERGY CONSUMPTION During the study period, corn’s energy use per acre increased by 3%, with improvement since 1999. The energy used to produce a bushel or unit of corn has decreased by 37%.
Meanwhile, the energy use per acre for soybeans has decreased by 48%, while energy use per bushel has decreased by 65%. The Alliance said soybeans utilize a very limited amount of nitrogen fertilizer and this considerably reduces the total amount of energy used to produce the soybeans, especially in comparison with more nitrogen-intensive crops. Soybeans have seen the most dramatic shift in inputs used, particularly herbicides and fuel for tillage. These factors have allowed the per-unit energy requirements to decline substantially over time.
Increased applications of nitrogen over the study period, coupled with relatively limited yield response, resulted in fluctuation of wheat’s energy use per acre and per bushel of output, with an overall 8% increase in energy per acre and a 9% decrease in energy per bushel.
GREENHOUSE EMISSIONS During the study period, corn saw an increase in emissions per acre of 8% and a 30% decrease in emissions per bushel.
Soybean tillage practices have moved heavily toward no-till over the years. Even with the assumption that only 10% of the annual no-till is continuous, as measured by the Conservation Technology Information Center, the net carbon balance per acre decreased for most of the study period, by 14% overall. Emissions per bushel decreased 38%.
The Alliance said that wheat’s climate indicator shows an increase in emissions per acre and per bushel of output over time, with the largest increases occurring in the last 10 years, resulting in a 34% increase in emissions per acre and 15% increase in emissions per bushel between 1987 and 2007. The primary factors affecting this indicator are increased nitrogen application with only a small increase in yields. While no-till is being readily adopted by wheat farmers, given the assumption of only 10% being continuous no-till, the soil carbon sequestration is inadequate to offset the nitrogen use.
"I was surprised to see that over the last twenty years we have dramatically reduced greenhouse gas emissions," Kevin Rogers, a member of the Alliance and a cotton grower from Arizona, said.