- Top of page
- 1 INTRODUCTION
- 2 DATA AND METHODS
- 3 RESULTS AND DISCUSSION
- 4 CONCLUSIONS
- Supporting Information
Triazine herbicides have been used by US crop producers for over 50 years. Atrazine (6-chloro-N-ethyl-N-isopropyl-1,3,5-triazine-2,4-diamine) was first commercially available for maize (Zea mays L.) production in the United States in 1959. Since then, atrazine has become the most widely used chloro-s-triazine herbicide in the United States and the most commonly used maize herbicide for many years, only recently surpassed by glyphosate (Fig. 1). Atrazine is the keystone of herbicide-based weed control in maize and crops such as sorghum (Sorghum bicolor L.), sweet maize (Zea mays var. saccharata) and sugar cane (Sacharum officinarum L.).[2, 3] In the United States, propazine (6-chloro-N,N4-diisopropyl-1,3,5-triazine-2,4-diamine) is used on sorghum, while simazine (6-chloro-N2,N4-diethyl-1,3,5-triazine-2,4-diamine) is used on maize and sweet maize acres and for weed control in many specialty crops such as citrus (genus Citrus), grapes (genus Vitis) and other fruits and nuts.
Figure 1. Percentage of US corn acres treated with atrazine, treated with glyphosate and planted with a herbicide-tolerant (HT) variety (Sources: Atrazine GfK and Glyphosate GfK,52 Atrazine USDA and HT USDA).
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Economic assessments of the benefits of atrazine have been part of the research and debate surrounding atrazine. Several studies have examined the farm-level economics of atrazine or have analyzed benefits at larger scales, holding crop prices and planted areas fixed.[4-11] To assess the market-level benefits of atrazine and triazine herbicides, a few studies also included grain supply changes to account for price effects. Carlson summarized previous comprehensive national or regional economic assessments of the benefits of atrazine and triazine herbicides, but these studies are older, with the most recent published in 1998.
Although more than a decade has passed since these economic assessments were published, they are still in use, in spite of large increases in maize yields, prices and planted area. For example, Ackerman used the 1994 report of Ribaudo and Bouzaher as part of an assessment of the economic impacts of a loss of atrazine for growers in the United States. Not only has the underlying demand structure for grain markets changed as a result of population growth and the rapid economic development of nations such as China, but also the overall economic size of the maize market in the United States has increased tremendously since the early 1990s. The 3 year average planted area of maize in the United States was 31.0 × 106 ha for 1990–1992, and had increased to 35.9 × 106 ha for 2007–2009, a 16% increase. Yields also increased: the 3 year average maize yield for 1990–1992 was 6.80 Mg ha−1 for each ha harvested, and 9.03 Mg ha−1 for 2007–2009, or 33% greater. Average prices received by farmers also increased. The 3 year average maize price was $US 88.20 Mg−1 for 1990–1992 and $US 157.11 Mg−1 for 2007–2009, a 78% increase. All combined, the 3 year average total production of maize in the United States increased from 211 × 106 Mg to 325 × 106 Mg over the same period, a 54% increase, and the 3 year average market value of this production increased by 170%, from $US 18.6 × 109 to 50.2 × 109 over the same period. Simply adjusting older estimates of the benefits of triazine herbicides for inflation, in the manner of Ackerman, ignores this expansion of the US maize market and underestimates the benefits. Rather, previous economic assessments of the benefits of triazine herbicides are outdated because they do not incorporate the large expansion of the maize market.
Other trends also imply that previous benefit assessments of triazine herbicides are no longer accurate for current markets and production conditions. Transgenic crops were first commercialized in 1995 and have become widely adopted since then. For example, 86% of the area planted to maize in the United States in 2010 was some type of transgenic (i.e. insect resistant and/or herbicide tolerant). Indeed, herbicide-tolerant crops have become so popular among farmers that, in 2007, glyphosate [N-(phosphonomethyl)glycine] surpassed atrazine as the most widely used herbicide on maize (Fig. 1). However, glyphosate-resistant weeds now threaten the efficacy of glyphosate, with many farmers aware of the problem and concerned about herbicide-resistant weeds.[19-24] In addition, the biofuel industry has become much larger since these previous studies were completed, causing various adjustments in the agricultural sector as a result of higher demand for maize.[25-27] Given market changes and trends such as these, previous assessments of the economic benefits of atrazine and triazine herbicides are outdated and do not accurately represent the current state.
The AGSIM model is used to provide an updated economic assessment of the benefits of atrazine to US producers, based on the yield effects reported by Bridges. Similar to previous studies, a counterfactual approach is used. Specifically, a non-triazine scenario is developed that describes how yields and costs would change if triazine herbicides were not available, and then the economic benefits of triazine herbicides are estimated as the difference between this non-triazine scenario and a baseline scenario in which triazine herbicides are used.
- Top of page
- 1 INTRODUCTION
- 2 DATA AND METHODS
- 3 RESULTS AND DISCUSSION
- 4 CONCLUSIONS
- Supporting Information
Triazine herbicides have been used by US crop producers for over 50 years, beginning with simazine for maize in 1958. US producers rely on atrazine, which for many years was the most widely used herbicide for maize production, only recently surpassed by glyphosate in popularity (Fig. 1). Even in the current era of widespread reliance on transgenic crops in the United States, atrazine continues to be popular, used on 57% of US maize acres in 2009 (Fig. 1). Atrazine is also commonly used on sorghum, sweet maize and sugar cane in the United States. In addition, propazine is registered for use on sorghum, and simazine is registered for use on maize, as well as on other fruit and nut crops.
In spite of its continued widespread use, recent economic assessments of the benefits of atrazine and the other triazine herbicides have been lacking, particularly market-level assessments that account for changes in crop prices and planted areas as a result of triazine herbicides. The last market-level assessment was published in 1998. US markets for maize and other crops have changed much since that time, with large increases in prices, yields and planted areas. This paper presents an updated economic assessment of its benefits for major commodity crops, including maize and sorghum, though not for all crops for which it is registered for use.
The analysis reported here uses AGSIM, an econometric model of supply and demand for ten major US crops that has been widely used to examine a variety of different policies. AGSIM uses a counterfactual approach that requires specifying how crop yields and costs of production would change for a policy, and then AGSIM projects changes in crop prices and land allocations for each crop, as well as changes in producer income and consumer surplus. The analysis here developed six non-triazine scenarios that projected how US producers would respond to not having triazine herbicides for maize and sorghum production.
Firstly, producers would increase use of non-triazine herbicides as substitutes, with glyphosate probably a popular choice for many growers. However, because glyphosate use has already reached very high levels among US maize producers (Fig. 1), two glyphosate use scenarios are specified to bracket the likely grower response. Following the model of Bridges, glyphosate use on maize is first allowed to increase as projected, up to 100% adoption, and then glyphosate use is held constant at 2009 levels and growers instead substitute other non-triazine herbicides besides glyphosate, as projected. These shifts in herbicide use imply decreases in maize and sorghum yields and changes in herbicide costs, for which this analysis uses the estimates of Bridges (Table 1).
Secondly, without triazine herbicides, growers would shift towards more intensive tillage, not only because an effective residual herbicide could not be used (atrazine) but also to address growing problems with glyphosate-resistant weeds. Table 2 reports baseline tillage system adoption rates by crop and region, and Table 3 reports the shifts in these adoption rates under the non-triazine scenarios. Rather than develop a predictive model, the shifts in Table 3 used for this analysis assume that tillage adoption would move to levels similar to those common 5–10 years ago in the United States. These tillage shifts would occur not only for maize and sorghum but also to a lesser extent for soybean and cotton, crops commonly rotated with maize and sorghum. Costs for no-till, conservation tillage and conventional tillage systems are estimated for these four crops, using crop budgets from several states (supporting information), and then the net effect of these tillage shifts on the average cost of production is determined for each crop and region (Table S5). AGSIM analysis combines cost changes due to tillage shifts (Table S5) and due to herbicide use changes (Table 1) to generate cost changes for six different non-triazine scenarios (Table 4).
AGSIM projections for the non-triazine scenarios are reported for crop prices (Table 5), crop-planted areas (Table 6), producer income changes (Table 7), consumer surplus changes (Table 8) and the effect on net social surplus by shifting from each non-triazine scenario to the 2009 baseline in which US crop producers use triazine herbicides (Table 9), which can be interpreted as the benefit of triazine herbicides.
Based on these results, triazine herbicides lower sorghum prices by about $US 24.50–26.00 Mg−1 and maize prices by about $US 9.50 Mg−1 to almost $US 12.00 Mg−1, with minimal effects on prices for other crops. These price effects reduce producer income by around $US 0.58–1.13 × 109 annually, but benefit consumers by $US 3.6–4.4 × 109 annually, for a net economic benefit ranging between $US 2.9 × 109 and 3.4 × 109 annually. Finally, triazine herbicides reduce the total land area in crop production by 270 000–390 000 ha.
The magnitude of these annual economic benefits from triazine herbicides, $US 2.9–3.4 × 109, are generally greater than for previous studies that also used AGSIM. For example, studies using the CEEPES modeling system relied on AGSIM for their market-level estimate of net benefits from triazine herbicides, with the resulting estimates in the range from $US 0.95 × 109 to almost $US 1.00 × 109.[15, 42, 67-70] The last comprehensive study using AGSIM that is comparable with this assessment found annual benefits ranging from around $US 1.2 × 109 to 1.3 × 109. Differences exist between these studies and the present study in terms of area treated, yield losses without triazine herbicides and herbicide cost changes, but the most significant change driving these differences is a large increase in the size of the US maize market.
More specifically, the area treated with atrazine has fallen from about 70% of the maize-planted area in the mid-1990s, the base period for the Carlson study, to 57% in 2009 (Fig. 1). Also, the herbicide cost changes for maize used for the Carlson study are slightly larger and the maize yield losses slightly smaller than those used in this study. However, the greatest difference between the studies is the tremendous expansion in the size of the US market for maize during the intervening years. Comparing 3 year averages for 1994–1996 and 2007–2009, the US area planted to maize increased by 16% and average maize yields increased by 24%, so that total maize production increased by 43%. In spite of this production increase, the average maize price increased by 44%, for an overall increase in average market value of US maize production of 109%, from $US 24.1 × 109 to 50.2 × 109.
The estimated annual net benefit of $US 2.9–3.4 × 109 from use of the triazine herbicides in crop production reported here updates these benefit estimates to reflect the substantial changes in the maize market summarized above. Furthermore, this assessment uses an updated AGSIM model that incorporates shifts in market relationships owing to changes such as the widespread adoption of transgenic crops, the expansion of the US biofuel industry and the increased demand for grain and livestock as a result of the rapid economic growth of nations such as China and India. Simple adjustments of older estimates of the benefits of triazine herbicides for inflation, as used by Ackerman, ignore the many changes in markets and policies that have occurred since the mid-1990s.
The version of AGSIM used for this analysis was updated for the 2008 crop year, for which marketing ends in August 2009. Since that time, commodity prices and planted areas have changed from the 2009 baseline used for this analysis, begging the question as to how these results would change under the market conditions of 2012, with 39.0 × 106 ha of maize planted and substantially higher market prices. In general, AGSIM estimates of price effects and consumer and producer surplus do not change substantially for different price bases, implying that the results reported here still generally apply for current market conditions. An update would be needed if significant market condition changes occurred, as would be the case for any empirical market model such as AGSIM.
The estimated net benefits reported here do not account for any of the environmental benefits from triazine herbicides that are due to land allocation effects. Specifically, this analysis projects that triazine herbicides reduce the total US land area in crop production by 270 000–390 000 ha. This land is currently in non-crop uses, such as planted to grasses and trees for enrollment in the Conservation Reserve Program or pasture. Such land probably generates more benefits for wildlife than as crop land, and, as such land is generally more marginal for crop production, is likely to have lower soil erosion rates than if used for crops.[61, 71, 72] Thus, triazine herbicides also generate economic benefits such as wildlife habitat and erosion control. Furthermore, the more intensive tillage projected to occur without triazine herbicides implies additional reductions in soil erosion owing to triazine herbicides, as well as less overall fuel consumption. The benefits of this reduced soil erosion have been estimated to range between $US 210 × 10 and 350 × 106 annually. As a result, the estimated annual net benefit of $US 2.9–3.4 × 109 for triazine herbicides reported here is in some sense a lower bound on the actual benefits, as it does not include values for these sorts of benefits. Nevertheless, the economic assessment summarized here updates the analysis to a base year of 2009, finding that triazine herbicides generate substantial benefits for the US economy, even without accounting for these environmental benefits.