Herbicides costs

Table 12.3 Yield and herbicide cost changes per area of crop grown if atrazine and the triazines were not available (various studies published prior to 1995)...

The percent yield loss and per acre or hectare cost changes are shown in Table 12.3. Due in part to the low estimate of atrazine pounds used, the CEEPES model resulted in a 1.19% yield loss and a 1.08 extra production cost per acre ( 2.66/ha) of corn grown, which is very small as compared with those by Battelle (1989, 1993) and is less than half of the effects shown by NAPIAP (1992), Danielson et al. (1993), and Pike el al. (1994). More recently, USEPA (2003) estimated that without atrazine in com, there would be a yield reduction of 8.8 bu/A, or a 6.4% reduction based on 2001 estimates of 138 bu/A. The total increased production cost estimated by USEPA for com was 28.31/A, based on decreased yield and increased herbicide cost. 

The CEEPES (1993, 1994) and NAPIAP (1992) studies show a higher yield and herbicide cost penalty for loss of atrazine or the triazines on sorghum than on com. This is due to the fact that there are fewer substitute herbicides registered for use on sorghum. 

Herbicide Cost Change ( /A) Yield Change (bu/A) Net Return Change ( /A treated)b Herbicide Cost Change ( /A) Yield Change (bu/A) Net Return Change ( /A treated)b... 

The review of triazine benehts studies shows the extensive data collection and analytical effort that is needed to carry out a credible benehts assessment. For the loss of an herbicide used on many crops, and which makes up a large part of the agricultural economy, it is essential to look at effects beyond the farm gate. In this case, losses are substantial because of lower weed control, higher herbicide costs, and indirect costs related to drift damage, sedimentation damage, and losses in reduced tillage com. In 2003, the USEPA estimated an annual value of 1.58 billion in the United States for com (USEPA, 2003). 

Banding of herbicides is not a new practice. In fact, when herbicides were first introduced for com production, it was common to band herbicides in order to keep herbicide costs low. However, farmers have largely replaced banding of herbicides in corn with broadcast sprays over the entire field. In 1993 in the US Com Belt, 16% of the com acreage was banded (USDA ERS, 1994). The rate of banding was highest in Nebraska (50%) and lowest in Illinois (3%). 

Chemical control. There are many different herbicides and products on the market, although several have been withdrawn recently due to EU legislatioa New herbicides cost a lot to develop and to get approval for use, so currently few new products are coming on to the market. The following is a suimnaty of modes of action of some of the currently approved herbicides. 

Historically, the discovery of one effective herbicide has led quickly to the preparation and screening of a family of imitative chemicals (3). Herbicide developers have traditionally used combinations of experience, art-based approaches, and intuitive appHcations of classical stmcture—activity relationships to imitate, increase, or make more selective the activity of the parent compound. This trial-and-error process depends on the costs and availabiUties of appropriate starting materials, ease of synthesis of usually inactive intermediates, and alterations of parent compound chemical properties by stepwise addition of substituents that have been effective in the development of other pesticides, eg, halogens or substituted amino groups. The reason a particular imitative compound works is seldom understood, and other pesticidal appHcations are not readily predictable. Novices in this traditional, quite random, process requite several years of training and experience in order to function productively. 

Degradation or Transformation. Degradation or transformation of a herbicide by soil microbes or by abiotic means has a significant influence not only on the herbicide s fate in the environment but also on the compound s efficacy. Herbicides that are readily degraded by soil microbes or other means may have a reduced environmental impact but may not be efficacious. Consider the phenomenon of herbicide-resistant soils. In these cases, repeated application of a given herbicide has led to a microbial population with an enhanced ability to degrade that herbicide (252,253). This results in a decrease or total loss of the ability of the herbicide to control the weed species in question in a cost-effective manner. 

Preparation of soil—sediment of water samples for herbicide analysis generally has consisted of solvent extraction of the sample, followed by cleanup of the extract through Uquid—Uquid or column chromatography, and finally, concentration through evaporation (285). This complex but necessary series of procedures is time-consuming and is responsible for the high cost of herbicide analyses. The advent of soUd-phase extraction techniques in which the sample is simultaneously cleaned up and concentrated has condensed these steps and thus gready simplified sample preparation (286). 

Between 1979 and 1991, the amounts of herbicide apphed in the United States have remained constant, but the expenditures on herbicides have increased 54%. Agricultural costs accounted for ah. of this increase and more, since herbicide user expenditures in the government/commercial and home sectors combined dropped 3 to 4% during that period. Increased weed control costs related to crop protection have also contributed to the 37% increase, since 1988, in total annual user expenditures for pesticides in general, ie, herbicides, fungicides, and insecticides. In the United States, agricultural uses (ca 1993) account for more than 67% of total pesticide user expenses and 75% of the quantity used annually. Herbicides are now the lea ding type of pesticides in terms of both user expenditures and volumes used (1). 

Because of the possibility that the herbicide alachlor could adulterate food if either poultry or livestock consumed contaminated materials, Lehotay and Miller evaluated three commercial immunoassays in milk and urine samples from a cow dosed with alachlor. They found that milk samples needed to be diluted with appropriate solvents (1 2, v/v) to eliminate the matrix effect. One assay kit (selected based on cost) was also evaluated for use with eggs and liver samples from chickens. Egg and liver samples were blended with acetonitrile, filtered, and diluted with water. Linear calibration curves prepared from fortified egg and liver samples were identical... 

Worldwide herbicide sales were projected to increase by 11.9% from 1980 to 1985 (17). The projected increase in herbicide sales in the United States from 1980 to 1985 was estimated at 12.4%. It was estimated that by 1985 herbicide sales would represent 61% of all pesticide sales in the United States, whereas herbicides would account for 42% of the pesticide sales worldwide (17). It is projected that pesticide sales by 1990 will reach 6.14 billion, a 7% per year growth from 1978 s 2.72 billion in sales (19). It is also projected that the average cost of pesticides will increase from 3.46/kg in 1978 to 6.88/kg in 1990 because of higher raw-materials costs and a shift to higher-performance materials. 

An annual estimated cost of approximately 938,835,000 is required for labor and equipment to apply 204.5 million kilograms of herbicides to 147.6 million hectares of cropland in the United States (Table IV). Mechanical tillage to control weeds between cropping seasons and interrow tillage of crops has been used for centuries as a very effective method of weed control. Approximately 50% of all tillage between crops is done to control weeds. The number of cultivations required for effective weed control within a row crop varies from two to five during a cropping season. 

The estimated cost of equipment, labor, and herbicides for weed control within a specific crop can be very expensive. For example, in 1980, cotton was planted on 5.2 million ha in the United States. The total cost for equipment, labor, and herbicides used to control weeds was estimated to be 547 million (20). Herbicides account for 32% of the total cost while equipment and labor costs were 34% each. 

Extent and Cost of Weed Control with Herbicides and on Evaluation of Important Weeds " U.S. Department of Agriculture, ARS-H-1, 1972, p 1-227. 

---