How fast have crop yields been rising?
Since the mid-1960s, average U.S. crop yields have been increasing. Corn yields have been increasing steadily at about 1.9 bu/ac per year. Soybean yields have increased as well, at about one third that rate. The slower rate of increase in soybean reflects the much higher energy content of soybean seed compared to corn. When corrected for the difference in energy content, both corn and soybean seed yields have been increasing at about the same speed. And in both cases, this 50-year record of continuous increase attests to the power of modern science and technology applied to crop production, especially since negative environmental impacts from erosion and inefficient use of fertilizers in producing these crops have decreased markedly. And although agriculture must continue to reduce negative environmental impacts, maintaining robust yield gains on existing farmland is essential to produce sufficient food supply without further expansion of crop area by conversion of rain forest and draining wetlands.
What factors contribute most to crop yield advance?
Modern, science-based crop production depends on three components: (i) improvements in crop genetics to support higher yields and greater insect and disease resistances, (ii) provision of an adequate supply of all 16 essential plant nutrients, of which nitrogen (N), phosphorus (P), and potassium (K) are required in greatest quantities, and (iii) improvements in the efficiency, power, and precision of mechanized equipment for sowing, harvesting, applying nutrients, and implementing pest control measures. Estimating the relative contribution of each component is difficult because they are all complementary such that combined benefits far outweigh the sum of individual contributions.
In fact, the remarkable yield advance of the past 50 years has been driving by a powerful locomotive of innovation in all three areas, including genetics, agronomy, and equipment, as can be seen in the Figure 1 below showing the innovations with greatest contributions to the steady increase in U.S. corn yields.
And for those who believe that future innovations will be much more powerful than those of past decades, consider the contribution of N fertilizer on corn yields, increasing three-fold from about 50 lb N/ac in the mid-1960s to more than 150 lb N/ac today. Or the fact that irrigated corn increased from less than 5% of total U.S. corn area in the mid-1960s, to nearly 15% of total corn area today. Or the large positive contributions to yield advance from earlier planting, higher sowing rates and plant densities, wider use of no-till and other conservation tillage methods in drier parts of the Corn Belt, precision high-speed planters, and auto-steer guidance systems that avoid overlaps and missing areas of seed, fertilizers and biocide applications. And all of this in addition to improved crop genetics, including transgenic herbicide and insect resistances!
Figure 1. Yield trends of U.S. corn since 1965 and associated technologies supporting this trend. Modified from Cassman et al., 2006. Convergence of energy and agriculture. Council on Agriculture, Science, and Technology (CAST), Madison, WI.
Will crop yields continue to rise?
The simple answer is yes, but the more important questions are by how much? For how long? And, by what means? The bad news is that the inflated prediction of doubling U.S. corn yields to 300 bu/ac by 2030, as predicted in 2008 by the ex-CEO of a recently merged seed company, are pure poppycock. Even if current rates of corn yield gains continue, that would only give average yields of about 220 bu/ac. Likewise, there is no evidence that the future technology locomotive will be more powerful than the train that brought us to where we stand today, as seen in the Figure. But the good news is that we can expect continued annual yield gain for corn of about 2 bu/ac and a bit less than one third of that for soybean, but only if there is continued public- and private sector investment in research and development to drive further innovations in genetics, agronomy, equipment. And only if we learn to harness the power of Big Data, as the fourth dimension of technological innovation, which was the topic of an earlier blog posted last year: mainstreetdata.cos://www.gisc.coop/the-end-of-agronomy-in-a-high-tech-world/
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