The science behind sustainable healthy soil

Organic Carbon content is a vital parameter of soil quality, yet the prevailing climate in arid and semi-arid areas is not conducive to its sustained accumulation. Dr Gil Eshel of the RECSOILCARBON project explains how his initiative into agricultural management can improve carbon sequestration.

Much of the world’s irrigated agricultural land is arid or semi-arid in nature, and while there is a long history of crop cultivation in areas with low rainfall, their environmental and climatic circumstances mean the effective management of the soil is a complex task. Organic carbon content in particular is one of the most important parameters of soil quality, yet climatic conditions in both arid and semi-arid areas prevent its accumulation in intensive cultivated lands, which in turn has a significant impact on the overall fertility of the soil. With concern growing over the impact climate change will have on the world’s agricultural land, these are issues the RECSOILCARBON project was formed to investigate.

“The main objective of RECSOILCARBON is to develop management strategies for carbon sequestration in agricultural soil in arid and semi-arid regions,” says Dr Gil Eshel, the project coordinator. The research is crucial not only for agriculture but for the wider environmental implications of the global carbon cycle too. “We aim to understand the relationship between the soil and the atmosphere, and to analyze the effects of the different management strategies; for example, what happens if we increase the carbon content in the soil?” he continues. “We are looking at how the organic carbon content of soil changes due to different soil practices or agricultural management strategies. We are also looking at the inorganic carbon in the soil; how the nature of the crops or management of the soil affects its CO2 profile for example, and the rate of soil – C02 exchange between the soil and the surrounding atmosphere.”

Climate change is predicted to change the nature of much agricultural land the world over, so the research isn’t just limited to arid or semi-arid areas. Eshel stresses that changes in soil management in arid areas – regions that enjoy less than 200 millimetres of rainfall per average year - can significantly improve their overall productivity. Soil Inorganic carbon, a calcite mineral, is also found in dry region soils and there’s a delicate balance between the two carbon pools. “The way you manage the soil affects the levels of organic carbon found within that soil. Organic carbon improves the structure of the soil, and also includes nutrients crucial to plant growth, such as nitrogen and phosphorus,” he says.

“Soil organic carbon improve the overall structure of the soil – the quality of the soil improves the more organic carbon there is. Since intensive plowing managements become so popular, about 40 per cent of original organic carbon contact been lost to the atmosphere by enhancing it’s oxidation,” outlines Eshel. “The challenge for those charged with managing the world’s soil is to build the world’s soil carbon stocks back up to earlier levels, so that sequestered carbon may be used for compensating our cornet CO2 emissions. Another major issue is the pool of inorganic carbon; in arid or dry regions you are likely to find more inorganic carbon than in wet areas, where inorganic carbon is usually leeched from the soil. So the pool of inorganic carbon is much higher in arid areas than it is in wet areas.”

The RECSOILCARBON project, based at the Israeli Ministry of Agriculture at its Soil Erosion Research Station, is committed to pursuing rigorous research into the effects of soil property, tillage intensity and organic matter load on carbon sequestration. However, the information needs to be transferred to farmers to make a true impact. “One of our most important goals is to improve the farming community’s knowledge of soil properties, and to help them improve their land management,” he explains. “Our research showed that the highest CO2 concentration in the soil is below the main root zoon of a number of plants, including orchards and filed crops. We believe that this kind of knowledge could bring significant benefits for farmers,” says Eshel. “We want to move farmers towards low to no-till practices that will help them improve the quality sustainability of their soil, and to use the CO2 concentration in the soil as a parameter for the soils aeration. The way in which the air changes in the soil is a parameter that can tell us if we need to plough it, and taking account of this kind of issue will bring significant improvements over traditional practices. Farmers used to think: ‘the more I plough the soil I “open” it and improve the air exchange between the soil and the atmosphere’, but our resent measurements show that under no till managements the soil aeration even better than under conventional tillage managements.

The project is even more relevant considering the international concern of climate change and agreements that all countries should reduce their carbon emissions. “The international authorities have decided to include smaller countries within the next climate change agreement. These countries should also reduce their carbon emissions and then balance these emissions with the sequestration of carbon, therefore agricultural management is an issue with broad relevance,” explains Eshel. “Climate change is not going to have a uniform impact across the globe. There will be areas that will be wetter and some that will be drier. In some areas precipitation levels may well not even change at all, but the intensity will increase.”

But, with some semi-arid areas predicted to become fully arid in the future, continuing research is essential. “We plan to work further on the tools that we have developed in this project and then apply them in order to improve our understanding of the effects of soil management on soil organic carbon. For example, we already know that high tillage intensity leads to a loss of soil organic carbon, while we are also looking at soil conservation, soil degradation, and soil chemical properties.”

For more information on the research, contact Dr Gil Eshel at eshelg@moag.gov.il

Published: Wednesday, 14th April 2010 by Tom Freeman

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