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.


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.

Australian Wheat Yields Have Doubled Thanks to Herbicides

Australian Wheat Yield 1930-2010 (Trendlines)

Australian Wheat Yield 1930-2010 (Trendlines)

Australian wheat-growing areas are dry. Historically, tillage was used to remove weeds, but tillage further dried out the soil. Herbicides have made it possible for Australian wheat farmers to stop tilling entirely. As a result, soil moisture retention has increased and wheat yields have doubled.

“An analysis of the yield trends of wheat production in Australia showed that yields have increased by an average of 12-13 kg ha-1 year-1 over the past six decades, despite rainfall not changing and irrigated wheat contributing only a very small proportion to total production. A more recent analysis of wheat yield trends in Australia and the various states of Australia has shown that since the early 1980s there has been a more rapid increase in yield of over 30 kg ha-1 year-1. In Western Australia, where wheat is not irrigated and rainfall has probably declined over the last 25 years, the increases… arise solely from increases in rainfall-use efficiency.

However, the major impact of agronomic management on rainfall-use efficiency has not arisen from increasing total water use by the crop in evapotranspiration, but from increasing water use by the crop itself in transpiration at the expense of water loss by weeds or from the soil by soil evaporation, deep drainage, surface runoff, or lateral throughflow.

The use of minimum tillage or conservation tillage, whereby residues from the previous crop are left on the surface, weeds are controlled by herbicides rather than tillage, and the seed is sown with minimum disturbance of the soil surface by the use of narrow tines, has led to reduced losses of water by soil evaporation and increased yields. Further, minimum tillage systems allow earlier planting as delays resulting from using tillage to remove weeds are reduced.”

Author: Turner, N. C.
Affiliation: CSIRO Plant Industry.
Title: Agronomic options for improving rainfall-use efficiency of crops in dryland farming systems.
Source: Journal of Experimental Botany. 2004. 407[55]:2413-2425.

Organic Growers Can Use Synthetic Herbicides When Planting a New Vineyard

Weedy Vineyard

Weedy Vineyard

Planting a new vineyard in a weedy field is a bad idea. Weeds would compete with the small vines for moisture, space, nutrients and light which would set back their growth. Thus, in establishing a new vineyard, growers need to clear the weeds out. Most growers use synthetic chemical herbicides when planting a new vineyard due to the high cost of hand weeding and negative effects of tillage. Using herbicides is an option for organic growers since the small vines do not produce grapes for several years which corresponds to the waiting time to be certified as organic.

“…weed management is the most expensive and technically challenging practice for organic grape production, and many organic farmers rely on mechanical and hand cultivation for weed control. Although these methods are highly effective, they are also labor intensive, more expensive, and their sustainability is questionable from a labor and environmental perspective.

Another option would be to use conventional production techniques that use synthetic herbicides during the establishment phase, and once established, transition the vineyard to achieve organic certification.”

Authors: Olmstead, M., et al.
Affiliations: Department of Horticultural Sciences, University of Florida.
Title: Weed control in a newly established organic vineyard.
Source: Hort Technology. December 2012. 22(6):757-765.

Organic Sugarbeets from Austria: Fungicide Use and Lots of Handweeding

Organic Sugar

Organic Sugar

There is a retail market for organic sugar in the EU and until recently the demand was met with imports of organic sugar from Latin America. British Sugar began producing organic sugar in the UK in 2002 but abandoned the organic line because it was not commercially viable. Now, a small number of sugarbeet growers in Austria are growing organic sugarbeets. Without herbicides for weed control, these growers need an enormous amount of hand labor. For disease control, the organic growers spray copper fungicides.

“In the past organic sugar from sugar cane was imported to Europe. In 2008 AGRANA started to contract organic sugar beet… In 2008 organic sugar beet was grown by 105 farmers on 323 ha. Up to 2011 the organic beet area was increased to 913 ha and reached about 2% of the Austrian sugar beet acreage.

Weed control is a major issue in production of organic beet. Farmers are using harrows and inter row cultivators for mechanical weed control. In addition, an enormous input of hand labour is required, on average there is the need for 200 hours per hectare.

Control of Cercospora leaf spot and powdery mildew is carried out by spraying fungicides containing copper or sulfur. Normally two or three sprayings with copper products are required to control Cercospora. It is allowed to apply up to 2 kg Copper per hectare and year.”

Authors: Kempl, F., et al.
Affiliation: AGRANA Zucker GmbH.
Title: Organically grown beets? A growing segment in the Austrian sugar production.
Source: 73ed IIRB Congress. 2012. Proceedings of Papers:183-186.