Herbicide Adoption Contributed Greatly to Increased Corn Production


Corn yields tripled in the U.S. between the 1930s and 1980s. Many new technologies and practices contributed to this increase in corn yields: hybrids, fertilizers, herbicides, insecticides, increased plant populations, early planting. A researcher at the University of Minnesota studied all of these factors to determine their contribution to the increase and determined that herbicides contributed about ¼ of the increase due to better weed control.

“Corn (Zea mays L.) yields in Minnesota have increased from the 2,010 kg/ha yield level of the pre-1930’s to the current 6,290 kg/ha average. This increased yield can be attributed to a series of technological, cultural, and management practices adopted by farmers. My objective is to attempt an analysis of the magnitude of the changes and the relative contributions to grain yield each practice has made over the 50-year time period.

Improved weed control by the use of herbicides on 93% of the hectarage has increased yields 23%.”

Author: Cardwell, V. B.
Affiliation: University of Minnesota, St. Paul.
Title: Fifty years of Minnesota corn production: sources of yield increase.
Source: Agronomy Journal. 1982. 74[November-December]:984-990.

Dangerous Respirable Dust Increased by Organic Farming in California

Airborne Dust From Cultivation

Airborne Dust From Cultivation

Health effects of breathing dust can be major. When inhaled, small dust particles can travel easily to the deep parts of the lungs and may remain there, causing respiratory illness, lung damage, and even premature death in sensitive individuals. People in California are exposed to unhealthful levels of small dust particles more frequently than to any other air pollutant measured. California farmers have minimized dust emissions by using herbicides to reduce weed populations instead of plowing the dry soil.  However, organic farmers do not use herbicides and cultivate their fields which results in significant increases in respirable dust in California.

“Respirable dust (RD), defined as particles smaller than 4µm diameter, was collected at the implement from 29 farming operations performed for furrow-irrigated tomato, corn, and wheat crop production over a 2-year period. …Among the cropping systems studied, those that required more tillage or land preparation to be performed when the soil was driest produced the most RD.

Cultivation of organically managed corn caused the greatest increase in RD, more than four times baseline.

In the organically grown crops, all operations related to soil structure improvement were performed in the dry fall. The organically grown corn was disked five times and land planed only once in the fall, while the organically grown tomatoes had four disking and three land-planing operations. As a result, the organically grown tomatoes had a much higher RD production. As in 1994, the organically grown crops produced more respirable dust than their conventional counterparts. The RD increase relative to conventionally grown crops ranged from 15% for the organically grown corn to 40% for the organically grown tomatoes.”

Authors: Clausnitzer, H., and M. J. Singer.
Affiliations: Department of Land, Air & Water Resources, UC Davis.
Title: Intensive land preparation emits respirable dust.
Source: California Agriculture. 1997. 51[2]:27-30

Herbicide Use Conserves Water, Tripling Sorghum Yields


Sorghum Yield: Bushland, Texas

Sorghum is grown primarily in Great Plains states where it is used as a livestock feed. Early grain sorghum production generally involved clean tillage for weed control which eliminated most surface residues. When retained on the surface, crop residues increase soil water storage which increase crop yield. A USDA-ARS laboratory was established in Texas in 1938 and numerous tests have been conducted on ways of increasing sorghum yield in the very dry Texas climate. When herbicides became available and tillage was no longer required for weed control, more residues remained on the soil surface, more water was conserved and sorghum yields increased dramatically.

“In early dryland studies at the USDA laboratories in Bushland, Texas, USA, most residues were plowed under. Residue management for sorghum production received a major boost when improved herbicides and planting equipment became available in the 1960s. Retaining crop residues on the soil surface with no-tillage and improved herbicidal weed control are largely responsible for the increased water conservation achieved since the early 1970s. For 37 studies at the laboratory, preliminary analysis revealed that dryland sorghum grain yields more than tripled from 1939 to 1997. A major increase occurred in the early 1970s when using no-tillage became common. From 1939-1970, mean yield exceeded 2000 kg ha-1 only six times, but exceeded that amount 20 times after 1970.

Soil water content at planting was the dominant factor contributing to yield increases with time. Most increases in soil water content at planting occurred after the early 1970s, when improved herbicides became available and using conservation tillage (crop residue retention on the soil surface) received major emphasis at the laboratory.”

Authors: Unger, P. W., and R. L. Baumhardt.
Affiliation: USDA-ARS.
Title: Crop residue management increases dryland grain sorghum yields in a semiarid region.
Source: Sustaining the Global Farm. Selected Papers from the 10th International Soil Conservation Meeting held May 24-29, 1999. Pgs: 277-282.

Without Herbicides, Cranberry Beds Would Be Overwhelmed by Weeds and Growers Would Go Out of Business

Treated vs Untreated

Herbicide Treated (L) vs Untreated (R)

71 - graph

The leaves of the cranberry plant form a dense mat over the surface. There are no paths through a cranberry bog. Weeds are particularly troublesome in cranberry bogs, since mechanical equipment (such as cultivators) cannot be used. The first synthetic chemical herbicide to receive widespread use in cranberries was registered in 1965 followed by two more in the 1970s. The use of these three herbicides is credited as the most important factor in the doubling of cranberry yields from 1960-1978. The introduction of glyphosate is credited with a steep increase in cranberry yields in the early 1980s.

“Without chemical pesticides fruit quality would be drastically reduced and it would be virtually impossible to economically produce a cranberry crop.

Without some selected herbicides or any herbicide, up to half of the growers would eventually go out of business because it would no longer be profitable to farm when their beds become overwhelmed by weeds in 5 to 10 years.

Without insecticides, fungicides, and herbicides, fruit quality would be drastically reduced. It would be virtually impossible to economically produce a cranberry crop. Ultimately, many growers would go out of business.”

Authors: Mahr, S. E. and Moffitt, L. J.
Affiliation: University of Wisconsin and University of Massachusetts.
Title: Biologic & Economic Assessment of Pesticide Usage on Cranberry.
Source: NAPIAP Report Number 2-CA-94-1994.

Herbicides Can Help in Making Tibet Food Secure

Farmland in Tibet

Farmland in Tibet

Tibet is isolated from the outside world by physical inaccessibility. Physical remoteness is exacerbated by the lack of roads. However, even though some roads exist, the long distance contributes to remoteness. In such circumstances, to produce enough food within the region and to minimize the dependency of acquiring food through exchange are the essence of food security. Crop yields in Tibet could be much higher. It is suspected that uncontrolled weeds are a major cause of low yields in Tibet and herbicides could be an effective technology to making Tibet food secure.

“In the south of the Tibet Autonomous Region of China there is a network of valleys where intensive agriculture is practiced. Although considered highly productive by Tibetans, farm incomes in the region are low, leading to a range of government initiatives to boost grain and fodder production. … Average yields for the main grain crops are around 4.0 t/ha for spring barley and 4.5 t/ha for winter wheat, significantly lower than should be possible in the environment.

…there is a large gap between attainable yields in Tibet and those that are typically attained on farms in the cropping zone.

There is a need to identify the most important weeds on Tibetan farms and the yield penalties they impose. If weeds do prove to be a significant constraint, as is suspected, a program to improve the availability and affordability of herbicides to Tibetan farmers, and to train farmers in their effective and safe use, should lead to crop yield increases. There is also a need to promote integrated weed management practices that combine cultural and manual control methods with the use of clean seed, targeted rotations, and herbicides.

In recent decades, there has been a major shift around the world towards no-till farming systems, in which weeds are controlled using herbicides before crops are sown into undisturbed soil using no-till seed drills. Such seeding systems would likely offer several benefits in Tibet: viz. lower crop establishment costs (e.g. for fuel and labour), less disturbance to soil structure, less disturbance to levelness of fields, and the option of retaining more stubble without impeding sowing for improved soil health.”

Authors: Paltridge, N., et al.
Affiliation: The University of Adelaide, Australia.
Title: Agriculture in Central Tibet: an assessment of climate, farming systems, and strategies to boost production.
Source: Crop & Pasture Science. 2009. 60:627-639.

Herbicide Technology Can Reduce Massive Crop Losses Caused by Parasitic Weeds in Africa

Treated vs. Un-treated

Treated (back) vs. Un-treated (front)

The parasitic weed Striga causes yield losses of 30-80% on 2.5 million hectares of crops in Africa. Striga seeds germinate and attach themselves to the roots of crop plants below ground. Striga sucks nutrients and water from the crop plant. The purple Striga flower appears above ground attached to the crop plant. A promising herbicide technology has been developed. The crop seed is coated with a herbicide. Striga seeds germinate, attach to the crop root and are killed by the herbicide. The herbicide technology is known as “IR-maize.”

Striga hermonthica (L.) Benth. or witchweed is a parasitic weed that attacks maize, sorghum, and pearl millet. It has become an increasing problem to small-scale subsistence farmers in sub-Saharan Africa and represents today the largest single biological barrier to food production in the region…. Striga infestations can become so severe in all major cereal producing regions of Africa that farmers will abandon their fields to cereal production and therefore large swathes of Africa will be precluded from becoming major cereal producing areas.

With this seed coating technology, Striga seeds after germination and before attachment and Striga seedlings that attach are controlled when the herbicide concentration in the soil or plant is adequate, thereby protecting the maize plant when it is most sensitive to parasitism.

New technologies being developed should be tested on-farm, under researcher- as well as under farmer-managed conditions before general dissemination…. Therefore, a set of trials, surveys, and farmer evaluations were conducted in western Kenya, parallel to the development of IR-maize.

IR-maize showed good Striga control and a dramatic yield increase of 2,400 kg ha−1 (from 1,300 to 3,700 kg ha−1).”

Authors: Ransom, J., et al.
Affiliations: North Dakota State University.
Title: Herbicide applied to imidazolinone resistant-maize seed as a Striga control option for small-scale African farmers.
Source: Weed Science. 2012. 60[2]:283-289.

The Importance of Pendimethalin Herbicide in Greece


Greek Cotton Field

Pendimethalin is normally used to control weeds on about 85% of the cotton and onion farms in Greece. During the last decade, the number of approved herbicides has drastically declined in Europe, leaving farmers with less choices and high weed control costs. Researchers at Aristotle University recently summarized the potential effects on Greek farmers if use of pendimethalin were to be stopped as a result of EU regulatory action.

“This work aims to determine the current state of experts’ knowledge, attitudes and beliefs regarding pendimethalin use in three crops (cotton, onion, processing tomato). The survey is focused on experts’ perceptions towards the necessity of pendimethalin in weed control, the advantages and disadvantages of pendimethalin and the probable impacts of pendimethalin withdrawal due to EU regulation or stoppage in manufacturing.

Any action of stoppage or withdrawal of pendimethalin from the market will bring about devastated effects on the farmers and crops, mainly due to lack of effective substitutes or herbicide combinations. The most significant impact, in case of pendimethalin withdrawal, would be a surge in production cost, since farmers must apply more costly and perhaps less effective weed control techniques (hoeing, covering land with plastic and using other combinations of herbicides).

…a Greek farmer hardly can harvest cotton without chemical weed control. Also, they stated that hardly can vision the possibility to cultivate onion, in the Viotia area, and cotton in Thessaly region without herbicide availability, since cost effective alternatives cannot being foreseen.

Then, considering the withdrawal effects of the use of pendimethalin in a regional level, the growers of cotton in Thessaly will lose a total of approximately €16.4 million of their gross production value and a total of approximately €7.3 million of their net revenues. …Finally, in a national level the growers of cotton in whole Greece will lose a total of approximately €42.8 million of their gross production value and a total of approximately €19.1 million of their net revenues.”

Authors: Mattas, K., et al.
Affiliations: Aristotle University of Thessaloniki.
Title: Economic assessment of Pendimethalin herbicide use in selective crops (cotton, processing tomato & onion).
Source: Aristotle University of Thessaloniki Working Papers No 166116 Available: http://EconPapers.repec.org/RePEc:ags:grauwp:166116.

Herbicide Use in Spanish Olive Groves Conserves Soil


The actual soil surface is indicated by the continuous black line, while the dashed line indicates the position of the original, eroded soil surface. The difference between both surfaces corresponds to the eroded soil profile.

Weed control in olive groves is necessary to prevent them from competing with the olive trees for moisture. In the 1970s, tillage with tractors became commonplace in Spanish olive groves. However, repeated ploughing left the soil loosened and torrential winter rains washed away the topsoil. Herbicide use has replaced tillage for weed control during the last twenty years and large reductions in soil erosion have occurred. A recent study determined that during the period of mechanical tillage, erosion rates were as high as 40t/ha/year while today, the erosion rate is 10t/ha/year.

“Olive orchards are an important agro-ecosystem in the Mediterranean. Soil erosion is a widely recognized threat to their sustainability. …This study aims at measuring and modelling soil erosion rates in olive orchards over a 250-year period, and relating these to changes in management practices and yield, as documented from historical sources. In three study areas in S-Spain, the height of relic tree mounds was measured in olive orchards dated between 153 and 291 years old to determine soil profile truncation. Historical documents allowed characterizing land management since 1752 in eight distinct periods.

Current soil losses by tillage are low because of the replacement of the spring tillage operations by herbicide application since the start of Period 8 in 2000. Only superficial harrowing is continued during summer. These superficial operations result in a lower movement of soil. In contrast, the highest soil erosion rates by tillage are found right after the introduction of mechanized agriculture, between 1970 and 1990 (Period 7), mainly because of deep mouldboard plowing, which is done at least twice a year.

Most of the tillage erosion occurred during periods of intense tillage, like from 1970 to 1990. To date, tillage is of minor importance due to the preference for herbicide use for controlling weeds.”


Authors: Vanwalleghem, T., et al.
Affiliation: Instituto de Agricultura Sostenible, Spain.
Title: Quantifying the effect of historical soil management on soil erosion rates in Mediterranean olive orchards.
Source: Agriculture, Ecosystems and Environment. 2011. 142:341-351.

Labor Shortages on Indian Tea Plantations Result in Need for Herbicides

Scraping Weeds In Tea Fields

Scraping Weeds In Tea Fields

Historically, the most common method of weed control on tea plantations in India was to manually scrape the weeds off the surface of the soil. However, this is a labor-intensive method and needs to be repeated at regular intervals. The paucity of labor in the tea gardens of south India has made weeding a difficult exercise. Presently, tea growers rely heavily on herbicides to control weeds due to labor shortages for manual weeding.

“Grassy weeds reduce the productivity of tea by 21 per cent, while broad-leaved weeds accounts for 9-12 per cent. Weeds remove substantial amount of nutrients and moisture from the soil besides increasing the incidence of pests and diseases in crop by serving as alternate host.

Herbicides, as a tool for controlling weeds in tea plantations is very much popular and have been widely used ever since their introduction – primarily due to their cost effectiveness, efficiency in controlling diverse weed flora and less labour intensiveness, etc. Tea plantations alone use about 20 per cent of the total quantity of herbicides used in India.

Mechanical and manual control of weed are costly, time consuming, laborious and sometimes injurious to feeder roots of young tea plants in comparison to herbicidal control of weeds. Such methods are also limited by non-availability of labours in peak season.These methods require about 75 man days/ha annually for young tea and 35 man days for mature tea while, 15 man days/ha for young tea and 8 man days for mature tea in the first year are required for herbicidal control of weeds excluding the cost of herbicides.

At present, herbicides worth over Rs.7 crores are being used by tea industry of North East. India alone is expected to increase further in view of acute shortage of labours in time and escalating wages of labour.”

Authors: Rajkhowa, D. J., et al.
Affiliation: National Research Centre for Weed Science.
Title: Weed management in tea.
Source: NRC for Weed Science, Jabalpur.2005. Pgs. 3-13.

Angry Italian Women Replaced by Herbicides


Le Mondine of the 1950s                                                                      Riso Amaro “Bitter Rice”

In Italian rice fields in the 1950s prior to the development of herbicides, weeding was done by hand. In May, the rice fields had to be weeded to prevent the young rice from being choked by other vegetation. Hundreds of women known as le mondine, or weeders, arrived from all parts of Italy to perform the delicate task of rooting out the weeds while leaving the young rice plants in place. Le mondine have become a nostalgic memory, immortalized by the famous film Riso Amaro or ‘Bitter Rice.’ It was a hard life for le mondine. They had to work bent double, up to their knees in water under a blazing sun. As the women weeded, they sang. One of the songs, Bella Ciao, was adopted by the Italian Communist Party to express the social injustice of the system. In the 1960s, most of the women left the rice fields when jobs opened up in cities, such as Milan, Genoa, and Turin. Today, herbicides are used in Italian rice fields.

“Italy is the largest rice producer in Europe, with about 235,000 ha in 2012. The main rice cultivation area is concentrated in the north-western regions of Piedmont and Lombardy where the continuous paddy rice system is widespread. Weed management is one of the key aspects of rice cultivation because pedo-climatic conditions are favourable to weeds that are generally competitive, there is a rich and persistant seed bank, and the weed flora is often dominated by difficult-to-control species… Consequently, farmers need to apply complex chemical and agronomic strategies to guarantee good weed control. Herbicide use is intense, with an average treatment frequency index higher than 2.5.”

Authors: Scarabel, L, et al.
Affiliations: National Research Council, Italy.
Title: Resistance evolution and sustainability of the rice cropping system: the Italian case study.
Source: Global Herbicide Resistance Challenge: Program and Abstracts. February 18-22, 2013. Pg. 105.