Carbon dioxide (CO2) in the atmosphere is used by plants to build their tissues, and when plants die, the carbon can reach the soil in which they grow. If the way of cultivating the earth can be optimized to prevent some of this carbon from returning to the atmosphere in the form of CO2, it will be contributing towards cutting greenhouse gas (GHG) emissions, one of the main causes of global warming and climate change. The Soil Management Group of the Public University of Navarre, which is now participating alongside INTIA (The Navarrese Institute of Agrifood Technologies and Infrastructure) and Fundagro (Foundation for Rural Development in Navarre) in the European LIFE project RegaDIOX, has been working in this line of research for the last ten years.
The project, being coordinated by Fundagro, is due to run for three years. The main aim is to design, test and disseminate the impact that can be exerted by an improved model of sustainable management of irrigation farming with respect to CO2 capture and GHG emissions. Various indicators will be assessed and analysed, among other things, to be able to estimate carbon sequestration, energy consumed and the quantity of emissions generated in relation to soil management, crop typology, irrigation systems, fertilisation, etc.
The NUP/UPNA researchers Paloma Bescansa, Iñigo Virto and Alberto Enrique will be responsible for a very specific part of the project which is related to soil management. 'For the last ten years we've been working on the processes involved in incorporating and stabilising organic matter in the soil,' said Paloma Bescansa. “A fresh approach is linked to the increase in carbon dioxide in the atmosphere and to keeping part of that CO2 in the soil, in the stored organic matter.”
In this respect, Alberto Enrique explains how the fixing of carbon in the soil is a natural process, but when the soil began to be cultivated, they lost part of the carbon which until that moment they had managed to retain. 'Organic matter is good for soil. Let’s consider a beech grove, for example. The tree converts CO2 molecules into carbon chains that form leaf tissue. When the leaves fall to the ground, they constitute highly beneficial organic matter for the soil in terms of fertility, and chemical and physical properties, etc. Finally, they end up being turned into nutrients, but in the meantime they provide the soil with a number of properties: they improve porosity, allow water to be transported, etc. In many agricultural soils, this content is reckoned to be between 1 and 3%, which seems very low but which nevertheless plays a very significant role in how the soil functions.”
What the researchers are now looking at is how to raise this input of natural carbon in the soil by means of better treatment and management of agricultural land, water, etc. so that with a specific soil and climate it is possible to achieve a greater capacity to retain CO2. “If the soil gains organic matter,” says Iñigo Virto, “not only can it partially prevent that return of CO2 to the atmosphere but it can also offer advantages from the point of view of soil fertility and help to cut erosion, for example. Agriculture, with different systems of management, can influence the whole process and, in the case of irrigation, the soil may be able to retain more carbon because, in some way, we are changing the conditions of a soil that used to be arid and which is now going to have more water; to simplify this a lot, we could say that the organic matter potential in the soil in a semi-arid area would turn into that of a more humid area.”
The NUP/UPNA researchers are participating directly in three of the six tasks set out by the RegaDIOX project: firstly, they will be comparing traditional dry regions with irrigation; secondly, they will be assessing various herbaceous crops (maize, vegetables, forage, alfalfa, etc.); and thirdly, within permanent crops, they will be focussing on vines and olive trees, because their soils are better suited to management with or without plant cover.
In this initial phase of the work the researchers are selecting a number of plots throughout the area affected by the Navarre Canal (areas which have been turned into irrigated land over the last fifteen years) before proceeding to characterise the soils. 'We'll be seeing what types of soils exist, because it’s one of the factors that has the greatest influence on this whole process and we’re going to see how the amount and type of organic matter in the soil evolve depending on the different systems of crop management,” explained Paloma Bescansa.
To their work will be added that developed by INTIA; this will produce a balance of the energy used and the GHG emissions associated with each agro-system; that way, it will be possible to estimate how much energy is used on a crop, how much fertiliser, the amount of emissions associated with that system, etc. “The idea,” as Iñigo Virto pointed out, “is to evaluate as broad a range as possible: water use, management systems, fertilisation, etc. and to quantify the GHG balance associated with all the actions linked to irrigation activity.”
For its part, the Fundagro Foundation will capitalising on and pursuing the advances made in the research and experimentation of the project with the agricultural sector in mind so that they can be transmitted to farmers; in turn, the practical application of them can be turned into reality by means of techniques and management systems with proven effectiveness.