Greenhouse Gas Emissions Lower With Herbicide Use

Cultivating Weeds in Australia

Cultivating Weeds in Australia

Agricultural greenhouse gas emissions can be curbed by decreasing fuel use by field equipment. The largest contribution to reducing emissions associated with farming is made by the reduction of tillage operations which are made primarily to control weeds. By substituting herbicides for tillage, dramatic reductions in fuel use and emissions occur because one herbicide application substitutes for multiple tillage trips. Tillage equipment is also heavier than herbicide sprayers and needs more energy to pull steel implements through the soil. A row crop cultivator requires four times more diesel fuel per acre than an herbicide sprayer. A recent study in Australia calculated the effects on greenhouse gas emissions…..

“In a wheat fallow system in semi-arid subtropical Queensland, Australia, practicing zero tillage reduced fossil fuel emissions from machinery operation by 2.2 million g CO2/ha over 33 years or 67 kg CO2/ha/year (four to five tillage operations with a chisel plough to 10 cm during fallow each year were replaced by one herbicide spray).”

Authors: Ortiz-Monasterio, I., et al.
Affiliation: CIMMYT, Mexico
Title: Greenhouse Gas Mitigation in the Main Cereal Systems: Rice, Wheat and Maize
Source: Climate Change and Crop Production. CAB International 2010.

Fungicide Use on UK Crop Acres Results in Significant Reductions in Greenhouse Gas Emissions

Fungicides are used on more than 90% of the cereal acres in the UK resulting in yield increases of 16-20%. Without fungicide use, it would be necessary to bring about 20% more land into cereal production to meet demand. All of the operations needed to bring a parcel of land into crop production (tractor operations, fertilization, pesticide application) result in the emission of greenhouse gases. Since fungicide use reduces the number of acres that need to be in production, their use is credited with a significant reduction in greenhouse gas emissions.

“The GHG emissions produced by growing arable crops derive mainly from agricultural inputs, such as fertiliser applications, the use of field machinery and crop treatments including disease control measures such as fungicides. … Nevertheless, the largest contributors to barley emissions are fertilisers, which account for 71-76% of all emissions. … Field operations contributed 19-23% of total emissions. … Crop protection chemicals contributed less than 1% of the total emissions.”

Fungicides were applied to 98 and 87% by area of UK winter and spring barley, respectively, in 2008. … If fungicide treatment had not been applied, an additional crop area of 165,000 ha (17%) on average would have been required each year to produce the same harvested yields of winter and spring barley in 2005-2009. Furthermore, an additional crop area of 638,000 ha (16%) on average would have been required to produce the same harvested yields of the four crops winter barley, spring barley, winter wheat and winter oilseed rape in 2005-2009.”

“Fungicide treatment of the major UK arable crops is estimated to have directly decreased UK GHG emissions by over 1.5 Mt CO2 eq. in 2009. … These results suggest that disease control in UK arable crops can have the positive environmental effect of reducing direct GHG emissions by making more efficient use of the inputs to agricultural production. …use of fungicides applied to control disease in UK barley contributed relatively little to GHGs while increasing yield and decreasing GHG emissions per tonne of crop.”

Authors: David Hughes et al.
Affiliation: Rothamsted Research, Harpenden, Herts, UK
Title: Effects of disease control by fungicides on greenhouse gas emissions by UK arable crop production.
Publication: Pest Management Science. 2011. 67:1082-1092.