Crop yield gap (Yg) can be disaggregated into two components: (i) one that is consistent across years and is, therefore, attributable to persistent factors that limit yields, and (ii) a second that varies from year to year due to inconsistent constraints on yields. Quantifying relative contributions of persistent and non-persistent factors to overall Yg, and identifying their underpinning causes, can help identify sound interventions to narrow current Yg and estimate magnitude of likely impact. The objective of this study was to apply this analytical framework to quantify the contribution of persistent factors to current Yg in high-yield irrigated maize systems in western US Corn Belt and identify some of the underpinning explanatory factors. We used a database containing producer yields collected during 10 years (2004–2013) from ca. 3000 irrigated fields in three regions of the state of Nebraska (USA). Yield potential was estimated for each region-year using a crop simulation model and actual weather and management data. Yg was calculated for each field-year as the difference between simulated yield potential and field yield. Two independent sources of field yield data were used: (i) producer-reported yields, and (ii) estimated yields using a combined satellite-crop model approach that does not rely on actual yield data. In each year (hereafter called ‘ranking years’), fields were grouped into ‘small’ and ‘large’ Yg categories. For a given category, Yg persistence was calculated by comparing mean Yg estimated for ranking years against mean Yg calculated, for the same group of fields, for the rest of the years. Explanatory factors for persistent Yg were assessed. Yg persistence ranged between ca. 30% and 50% across regions, with higher persistence in regions with heterogeneous soils. Estimates of Yg size and persistence based on producer-reported yields and satellite-model approach were in reasonable agreement, though the latter approach consistently underestimated Yg size and persistence. Small Yg category exhibited a higher frequency of fields with favorable soils and soybean-maize rotation and greater N fertilizer and irrigation inputs relative to the large Yg category. Remarkably, despite higher applied inputs, efficiencies in the use of N fertilizer, irrigation, and solar radiation were much higher in fields exhibiting small Yg. The framework implemented in this study can be applied to any cropping system for which a reasonable number of field-year yield and management data are available.
Large-scale monitoring of crop growth and yield has important value for forecasting food production and prices and ensuring regional food security. A newly emerging satellite retrieval, solar-induced fluorescence (SIF) of chlorophyll, provides for the first time a direct measurement related to plant photosynthetic activity (i.e. electron transport rate). Here, we provide a framework to link SIF retrievals and crop yield, accounting for stoichiometry, photosynthetic pathways, and respiration losses. We apply this framework to estimate United States crop productivity for 2007–2012, where we use the spaceborne SIF retrievals from the Global Ozone Monitoring Experiment-2 satellite, benchmarked with county-level crop yield statistics, and compare it with various traditional crop monitoring approaches. We find that a SIF-based approach accounting for photosynthetic pathways (i.e. C3 and C4 crops) provides the best measure of crop productivity among these approaches, despite the fact that SIF sensors are not yet optimized for terrestrial applications. We further show that SIF provides the ability to infer the impacts of environmental stresses on autotrophic respiration and carbon-use-efficiency, with a substantial sensitivity of both to high temperatures. These results indicate new opportunities for improved mechanistic understanding of crop yield responses to climate variability and change.
Most people in the world today think democracy and gender equality are good, and that violence and wealth inequality are bad. But most people who lived during the 10,000 years before the nineteenth century thought just the opposite. Drawing on archaeology, anthropology, biology, and history, Ian Morris, author of the best-selling Why the West Rules--for Now, explains why. The result is a compelling new argument about the evolution of human values, one that has far-reaching implications for how we understand the past--and for what might happen next.
Fundamental long-term changes in values, Morris argues, are driven by the most basic force of all: energy. Humans have found three main ways to get the energy they need--from foraging, farming, and fossil fuels. Each energy source sets strict limits on what kinds of societies can succeed, and each kind of society rewards specific values. In tiny forager bands, people who value equality but are ready to settle problems violently do better than those who aren't; in large farming societies, people who value hierarchy and are less willing to use violence do best; and in huge fossil-fuel societies, the pendulum has swung back toward equality but even further away from violence.
But if our fossil-fuel world favors democratic, open societies, the ongoing revolution in energy capture means that our most cherished values are very likely to turn out--at some point fairly soon--not to be useful any more.
Originating as the Tanner Lectures delivered at Princeton University, the book includes challenging responses by novelist Margaret Atwood, philosopher Christine Korsgaard, classicist Richard Seaford, and historian of China Jonathan Spence.
A Stanford-led team has discovered how to estimate crop yields with more accuracy than ever before with satellites that measure a special form of light emitted by plants. This breakthrough will help scientists study how crops respond to climate change.
As Earth's population grows toward a projected 9 billion by 2050 and climate change puts growing pressure on the world's agriculture, researchers are turning to technology to help safeguard the global food supply.
A research team, led by Kaiyu Guan, a postdoctoral fellow in Earth system science at Stanford's School of Earth, Energy, & Environmental Sciences, has developed a method to estimate crop yields using satellites that can measure solar-induced fluorescence, a light emitted by growing plants. The team published its results in the journal Global Change Biology.
Scientists have used satellites to collect agricultural data since 1972, when the National Aeronautics and Space Administration (NASA) pioneered the practice of using the color – or "greenness" – of reflected sunlight to map plant cover over the entire globe.
"This was an amazing breakthrough that fundamentally changed the way we view our planet," said Joe Berry, professor of global ecology at the Carnegie Institution for Science and a co-author of the study. "However, these vegetation maps are not ideal predictors of crop productivity. What we need to know is growth rate rather than greenness.
The growth rate can tell researchers what size yield to expect from crops by the end of the growing season. The higher the growth rate of a soybean plant or stalk of corn, for instance, the greater the harvest from a mature plant.
"What we need to measure is flux – the carbon dioxide that is exchanged between plants and the atmosphere – to understand photosynthesis and plant growth," Guan said. "How do you use color to infer flux? That's a big gap."
Recently, researchers at NASA and several European institutes discovered how to measure this flux, called solar-induced fluorescence, from satellites that were originally designed for measuring ozone and other gases in the atmosphere.
A plant uses most of the energy it absorbs from the sun to grow via photosynthesis, and dissipates unused energy as heat. It also passively releases between 1 and 2 percent of the original solar energy absorbed by the plant back into the atmosphere as fluorescent light. Guan's team worked out how to distinguish the tiny flow of specific fluorescence from the abundance of reflected sunlight that also arrives at the satellite.
"I think of it like crumbs falling to the ground as people are eating. It's a very small trail," said co-author David Lobell, associate professor of Earth system science at Stanford's School of Earth, Energy, & Environmental Science. "This glow that plants have seems to be very proportional to how fast they're growing. So the more they're growing, the more photosynthesis they're doing, and the brighter they're fluorescing." Lobell is also deputy director of the Center on Food Security and the Environment.
The research team saw an opportunity to use this new data to close the knowledge gap about crop growth, beginning with a major corn- and soybean-producing region of the U.S. Midwest.
"With the fluorescence breakthrough, we can start to directly measure photosynthesis instead of color," Guan said.
The fact that fluorescence can now be detected from space allows researchers to measure plant growth across much larger areas and over long periods of time, giving a much clearer picture of how yields fluctuate under changing weather conditions.
"One of the really cool things about fluorescence is that it opens up a whole new set of questions that we can ask about vegetation, and often times it's these new measurements that drive the science forward," Lobell said.
The research team has already identified a number of potential uses of this approach by agricultural scientists, farmers, crop insurance providers and government agencies concerned with agricultural productivity.
If there is a day when the plant is really stressed, the fluorescence will drop significantly, Lobell said. Capturing these short-term responses to environmental changes will help scientists understand what factors plants are responding to on the daily time scale.
"That helps us, for example, figure out what we need to worry about in terms of stresses that crops are responding to," Lobell said. "What should we really be focusing on in terms of the next generation of cropping systems? What should they be able to withstand that the current crops can't withstand?"
At this early stage, fluorescence measurements are relatively low-resolution (a single measurement covers about 50 square kilometers) and because it is only collected once per day, cloudy skies can interfere with the fluorescence signal. For now, researchers have to supplement the data with other information and with on-the-ground observations to refine the measurements.
"Now that we have demonstrated the concept, we hope to soon be orbiting some new satellites specifically designed to make fluorescence measurements with better spatial and temporal resolution," Berry said.
The team plans to continue its research on U.S. crop yields while expanding measurements to other parts of the world.
"In the future, we hope to directly use this technology to monitor global food production, for example in China or Brazil, or even in your backyard," Guan said.
David Lobell is also deputy director of the Center on Food Security and the Environment, and William Wrigley Senior Fellow at the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment. The study was also co-authored by Youngguan Zhang of the International Institute for Earth System Sciences at Nanjing University and the German Research Center for Geosciences (GFZ); Joanna Joiner of the NASA Goddard Space Flight Center Laboratory for Atmospheric Chemistry and Dynamics; Luis Guanter of GFZ; and Grayson Badgley of Stanford's Department of Earth System Science and Department of Global Ecology at the Carnegie Institution for Science.
CONTACTS:
p> Kaiyu Guan, Stanford School of Earth, Energy, & Environmental Sciences: kaiyug@stanford.edu
Laura Seaman, Stanford's Center on Food Security and the Environment: lseaman@stanford.edu, (650) 723-4920
Read the original post on Medium.com:
A Global Perspective on Food Policy
I applaud Mark Bittman, Michael Pollan, Ricardo Salvador, and Olivier de Schutter for advocating the introduction of a national food policy in the U.S. Greater emphasis in our current farm legislation on nutrition, health, equity, and the environment is clearly warranted and long overdue. As the authors note, Americans’ access to adequate nutrition at all income levels affects educational and health outcomes for the nation as a whole. Poor nutrition thus plays a role in determining the level and distribution of economic and social wellbeing in the U.S, now and in the future. It is surprising that no one within the large circle of Presidential hopefuls has raised the topic of food, not just agriculture, as a major political issue for the 2016 election.
The U.S. is not unique. Virtually every country with an agrarian base has, at some point in history, introduced agricultural policies that support farmers and provide incentives for them to produce major commodities. At the time, governments have been able to justify these policies on several grounds: national security (avoiding excess dependence on foreign nations for food), economic growth (using agricultural surpluses as an engine of economic growth), and social stability (keeping its population well-fed to avoid social unrest). Once agricultural policies are implemented, they typically give rise to institutions and vested political interests that perpetuate a supply-side orientation to food and agriculture. In the U.S., the political institutions that govern food and agriculture have their roots in historical political precedents that date back to the 1860s, and later to the 1930s when the New Deal was promulgated. Farm interests have been entrenched in the U.S. political system for quite some time, and they cannot be easily removed.
There is a general rule for successful policies: Align incentives with objectives. A corollary to this principle is that objectives change over the course of economic development. For the United States in earlier eras, and for many developing economies in recent decades, meeting basic calorie needs has been the first order of business. This objective has been largely achieved through public investments in infrastructure (irrigation, roads), research and development, commodity support programs, incentives for private agribusiness development, and other supply-side measures.
With successful agricultural growth and rising incomes, many countries face a new set of food and nutrition challenges: eliminating “hidden hunger” (deficiencies in iron, vitamin A, calcium, zinc and other micronutrients), and abating the steady rise in obesity that results from a transition to diets rich in energy-dense carbohydrates, fats, and sugar. Hidden hunger affects some three billion people worldwide. It is prevalent among low-income households in almost all countries, impairs cognitive and physical development (especially among infants up to two years of age) and thus limits a nation’s educational and economic potential. Meanwhile, rates of obesity now surpass rates of energy-deficient hunger throughout the world, even in developing nations.
The objectives of food and agricultural policies in virtually all countries need to shift, on balance, from promoting staple food supplies to enhancing nutrition. I am not suggesting an abandonment of agriculture, but rather an enrichment of agriculture with more crop diversity to support the nutritional needs of all people. If improved nutrition is the objective, what are the correct incentives? Proper incentives will differ among countries, but will inevitably require a fundamental change in institutional structure. With a shift from supply- to demand orientation, there needs to be a transition from Ministries of Agriculture to Ministries of Food. After all, the main goals of a Ministry of Agriculture are to increase the volume of agricultural production and to improve economic growth in the agricultural sector. The main goal of a Ministry of Food, by contrast, is to enhance the nutrition and food security of the entire population.
Bittman, Pollan, Salvador, and de Schutter emphasize that replacing the U.S. Department of Agriculture (USDA) with a “U.S. Department of Food, Health, and Wellbeing” would be difficult at best. It would require unprecedented political will and cooperation among parties. The same can be said for institutional change in agricultural ministries throughout the world. Regardless of the challenges, however, nothing will change until the conversation surrounding food policies, politics, and institutions takes a major turn.
FSE director Roz Naylor will give the opening plenary lecture at the 2nd International Conference on Global Food Security on October 12, 2015 at Cornell University. Naylor is William Wrigley Professor in Earth System Science, and senior fellow at the Stanford Woods Institute for the Environment and the Freeman Spogli Institute for International Studies at Stanford.
In addition to Naylor's lecture on "Food security in a commodity-driven world," several FSE researchers will give talks and poster sessions during the five-day conference, including professors Marshall Burke and Eric Lambin, visiting scholar Jennifer Burney, postdoctoral scholar Meha Jain, and doctoral candidate Elsa Ordway.
Abstract: How rainfall arrives, in terms of its frequency, intensity and the timing and duration of rainy season, may have a large influence on rainfed agriculture. However, a thorough assessment of these effects is largely missing. This study combines a new synthetic rainfall model and two independently-validated crop models (APSIM and SARRA-H) to assess sorghum yield response to possible shifts in seasonal rainfall characteristics in West Africa. We find that shifts in total rainfall amount primarily drive the rainfall-related crop yield change, with less relevance to intra-seasonal rainfall features. However, dry regions (total annual rainfall below 500 mm/year) have a high sensitivity to rainfall frequency and intensity, and more intense rainfall events have greater benefits for crop yield than more frequent rainfall. Delayed monsoon onset may negatively impact yields. Our study implies that future changes in seasonal rainfall characteristics should be considered in designing specific crop adaptations in West Africa.
