Australia is seeing increases in the frequency of extreme weather events such as droughts and heavy rainfall. The Bureau of Meteorology (BOM) and the CSIRO have just released the new State of the Climate Report 2020. This report shows that Australia’s average temperature has increased by 1.44 degrees since 1910. (BOM 2020)
- Australia is seeing increases in the frequency of extreme weather events such as droughts and heavy rainfall.
- The Bureau of Meteorology (BOM) and the CSIRO have just released State of the Climate Report 2020.
- This report shows that Australia’s average temperature has increased by 1.44 degrees since 1910.
- Farmers have to adapt to the increasing intensity and frequency of adverse and extreme weather events such as droughts and heavy, damaging rainfall.
- Farming systems that actively increased soil organic matter (SOM) are more resilient to predicted weather extremes and can produce higher yields compared to industrial farming systems.
- SOM is one of the most neglected yet most important factors in soil fertility, disease control, water efficiency, and farm productivity.
- The key to successful soil health is the correct management of SOM.
- Research shows that organic systems use water more efficiently due to better soil structure and higher levels of humus and other organic matter compounds.
- Improving the efficiency of rain fed agricultural systems through good SOM practices is the most efficient, cost effective, environmentally sustainable and practical solution to ensure reliable farm production in the increasing weather extremes being caused by climate change.
The critical issue the Report shows is that the frequency of extreme weather events are increasing with longer and more severe droughts, disruptions in regular seasonal rainfall and increases in heavy and destructive rain events.
The fact is, even if the world achieves the Paris Climate Meeting target of two degrees warmer, the temperature increase will result in an increase in the severity of extreme weather events. This means that farmers have to adapt to the increasing intensity and frequency of adverse and extreme weather events such as droughts and heavy, damaging rainfall.
Greater Resilience for Farms in Adverse Conditions
Published studies show that farming systems that actively increased soil organic matter (SOM) are more resilient to the predicted weather extremes and can produce higher yields compared to industrial farming systems in such conditions (Drinkwater et al., 1998; Welsh, 1999; Pimentel, 2005). For instance, the Wisconsin Integrated Cropping Systems Trials found that system with higher levels of SOM had higher yields in drought years and the same as industrial agricultural systems in normal weather years (Posner et al., 2008)
SOM is one of the most neglected yet most important factors in soil fertility, disease control, water efficiency, and farm productivity. The key to successful soil health is the correct management of SOM, as this gives the soil an open, friable structure to aid both drainage and water retention.
Soil organic matter is mostly composed of carbon. In many technical texts the carbon in the soil is referred to as Soil Organic Carbon (SOC). Soil organic matter contains many other minerals, not just carbon, and that is why this article will refer to SOM rather than SOC. The accepted ratio for the amount of soil organic carbon in soil organic matter is SOC × 1.72 = SOM.
This ratio shows that carbon is the major component of soil organic matter. The vast majority of this carbon has come from carbon dioxide (CO2) in the air that has been captured through photosynthesis. The ability of regenerative farming systems to drawdown (sequester) CO2 from the air and deposit it in the soil is critical to improving the productivity of farming systems.
Because soil health and soil organic matter have largely been ignored in industrial agriculture until recently, most of the published scientific research has been done in organic agriculture systems because they were the only systems that actively used methods to increase soil organic matter. Lately other systems are adopting the techniques pioneered by the organic sector under the umbrella of Regenerative Agriculture. Most of the scientific references in this article are from the organic sector due to the absence of similar published data from the industrial farming sector.
Improved Efficiency of Water Use
Research shows that organic systems use water more efficiently due to better soil structure and higher levels of humus and other organic matter compounds (Lotter et al., 2003; Pimentel, 2005). Lotter and colleagues collected data over ten years during the Rodale Farm Systems Trial (FST). The more porous structure of the organically treated soil allows rainwater to quickly penetrate the soil, resulting in less water loss from run-off and higher levels of water capture. This was particularly evident during the two days of torrential downpours from hurricane Floyd in September 1999, when the organic systems captured around double the water compared to the industrial system. (Lotter et al., 2003)
Long term scientific trials conducted by the Research Institute of Organic Agriculture (FiBL) in Switzerland, a European mountain country, comparing organic, biodynamic and industrial/conventional systems (DOK Trials) had similar results showing that organic systems were more resistant to erosion and better at capturing water in extreme rainfall events. (Mader et al 2009)
This is consistent with many other comparison studies that show that organic systems have less soil loss due to the better soil structure and higher levels of organic matter. (Reganold et al. 1987, Reganold et al. 2001, Pimentel 2005) ‘We compare the long-term effects (since 1948) of organic and conventional farming on selected properties of the same soil. The organically-farmed soil had significantly higher organic matter content, thicker topsoil depth, higher polysaccharide content, lower modulus of rupture and less soil erosion than the conventionally-farmed soil. This study indicates that, in the long term, the organic farming system was more effective than the conventional farming system in reducing soil erosion and, therefore, in maintaining soil productivity’ (Reganold et al. 1987).
Humus, a key component of soil organic matter, is one of the main reasons for the ability of organic soils to be more stable and to hold more water. This is dues to its ability to hold up to 30 times its own weight in water and being a ‘sticky’ polymer, glues the soil particles together given greater resistance to water and wind erosion. (Stevenson 1998)
The Importance of Organic Matter for Water Retention and Drought Resistance
There is a strong relationship between the levels of soil organic matter and the amount of water that can be stored in the root zone of a soil. The table below should be taken as a rule of thumb, rather than as a precise set or measurements. Different soil types will hold different volumes of water when they have the same levels of organic matter due to pore spaces, specific soil density and a range of other variables. Sandy soils as a rule hold less water than clay soils.
The table gives an understanding of the potential amount of water that can be captured from rain and stored at the root zone in relation to the percentage of soil organic matter.
Volume of Water Retained /ha (to 30 cm) in relation to soil organic matter (SOM)
0.5% SOM = 80,000 litres
1 % SOM = 160,000 litres (common farm level in much of Africa, Asia, Australia and parts of Latin America)
2 % SOM = 320,000 litres
3 % SOM = 480,000 litres
4 % SOM = 640,000 litres
5 % SOM = 800,000 litres (pre-settlement/farming levels in many countries)
6 % SOM = 960,000 litres (Adapted from Morris 2004)
There is a large difference in the amount of rainfall that can be captured and stored between the current SOM level in most farms in Australia and a farm with reasonable levels of SOM. This is one of the reasons why organic farms do better in times of low rainfall and drought.
The Rodale Farming Systems Trials (FST) showed that the organic systems produced more corn than the industrial/conventional system in drought years. The average corn yields during the drought years were from 28% to 34% higher in the two organic systems. The yields were 6,938 and 7,235 kg per ha in the organic animal and the organic legume systems, respectively, compared with 5,333 kg per ha in the conventional system (Pimentel, 2005). The researchers attributed the higher yields in the dry years to the ability of the soils on organic farms to better absorb rainfall. This is due to the higher levels of SOM in those soils, which makes them more friable and better able to store and capture rain water which can then be used for crops. (Rodale 2011)
This is very significant information as the majority of Australia’s farming and grazing systems are rain fed. Australia does not have the resources to irrigate all of the agricultural lands. Nor should such a project be started as damming watercourses, pumping from all the underground aquifers and building thousands of kilometers of channels would be an unprecedented environmental disaster. It will never be funded under today’s political reality.
Improving the efficiency of rain fed agricultural systems through good SOM practices is the most efficient, cost effective, environmentally sustainable and practical solution to ensure reliable farm production in the increasing weather extremes being caused by climate change.
ABOUT THE AUTHOR / André Leu is the International Director of Regeneration International, a global NGO that promotes food, farming and land use systems that regenerate and stabilise eco systems, climate systems, the health of the planet and people. He, along with the other founders of Regeneration International, started the world wide regenerative farming movement. André is the Author of the ‘Myths of Safe Pesticides’ and ‘Poisoning our Children’. He is the co-author with Dr Vandana Shiva of ‘Biodiversity, Agroecology, Regenerative Organic Agriculture – Sustainable Solutions for Hunger, Poverty and Climate Change’ . André first came to the Douglas Shire in 1971 and has, with his wife Julia, an organic tropical fruit farm in Lower Daintree.
The next series of articles will look at how to increase SOM and it’s many other benefits to make farming and grazing more productive and profitable
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