Among the many challenges that the agriculture of the future faces, soil fertility ranks high on the list of priorities.
Originally, most farms were mixed. They had land to grow crops and they had animals for milk, eggs and meat. Markets were mostly local, and food was consumed in the villages and towns near the farms. Food waste was fed to farm animals; the manure produced was mixed with straw and returned to the fields where the crops had been grown. Over time, farming has evolved. Agriculture has become much larger scale, global and specialized. This evolution has been driven by the use of oil, mechanization, and by the development of mineral fertilizers.
That model, which has been greatly based on cheap energy and resources, needs to be looked at critically as the economic environment changes. Energy is no longer cheap and, like oil, the resources used for the production of fertilizers have been depleted. New solutions are required to be able to produce optimally.
The production of nitrogen fertilizers requires a lot of energy. According to estimates, it uses 5% of the world’s natural gas production, and half the fossil fuels used in agriculture. Because nitrogen is quite mobile when dissolved, as this happens when it rains, a large amount of these high-energy-consumption compounds are lost. An estimated 50% of the nitrogen spread on crops leaches through the soil. It ends up in the water system. The reserves of phosphates, another important mineral fertilizer, are facing depletion. This might happen in 20 years from now. With the development of precision agriculture, the waste of minerals can be reduced. With the development of satellite imaging indicating the mineral status of a field, and the local variations within the field, it has become possible for farmers to bring just the right amount of the right mineral at the right time and at the right place. This follows somehow a similar thinking as fertilizing plants in hydroponics operations where crops are produced without soil and fed a mineral solution drop by drop.
A consequence of the specialization between crop farms and intensive animal farms is the rupture of the organic matter cycle. Large monoculture farms have suffered soil erosion because of a lack of organic matter, among other reasons. In soils, the presence of organic matter increases moisture retention, increases minerals retention and enhances the multiplication of microorganisms. All these characteristics disappear when the quantity of organic matter decreases. A solution to alleviate this problem is the practice of no-tillage together with leaving vegetal debris turn into organic matter to enrich the soil. This has helped restore the content of organic matter in the soil, although one can wonder if this practice has only positive effects. Tillage helps eliminating weeds. It also helps break the superficial structure of the soil, which can develop a hard crust, depending on the precipitations and the clay content of the soil. Possibly, in the future the use of superficial tillage could become the norm. Deep tillage, as it has been carried out when agriculture became mechanized, has the disadvantage of diluting the thin layer of organic matter in a much deepen layer of soil. This dilution seriously reduces the moisture and mineral retention capacity of soils, thus contributing to erosion as well, even in organic matter-rich soils.
The removal of farm animals from specialized crop farms requires the systematic use of mineral fertilizers because farmers do not have access to manure and the minerals it contains, even though most of these minerals originate from the crops farms.
At the other end of this interrupted cycle of manure, intensive animal farms do not suffer a lack of organic matter and minerals. They have the opposite problem. They have too much of it, and not enough acreage, if any, where to spread it. This leads to accumulation of manure and other related problems, such as stench, high concentrations of minerals in the soil and eventually in the waterways and drinking water reserves.
Since nothing is lost, what has happened to the minerals from fields and from fertilizers? They have been transferred to other places via the global trade of agricultural commodities. Many of these commodities are used to produce animal feed. Phosphate in European pig manure may come from Asian manioc farms. Therefore, the best way to find out where the minerals are is to look at where intensive animal husbandry farms are. As mentioned earlier, nitrogen is washed away into the water system because of its mobility. Unlike nitrogen, phosphates are not mobile in the soil. They will accumulate, which also leads to a loss of soil fertility, eventually. The other area of concentrations of these minerals is in city sewers, and in the soil of slums. Since the purpose of agriculture is to produce food, and since consumers are increasingly concentrated in urban centers, the exportation of minerals is actually gathering momentum out of rural areas.
In the future, we are going to see a new look at fertilization. The economics of agriculture will change. This is inevitable, because the cost of inputs will increase. This will be a direct consequence of the increase of the price of oil, and of the depletion of phosphates reserves. This change of economics will drive renewed interest for manure, and for sewage. These sources will become attractive and competitive, as they contain large amounts of minerals directly available. Because of their nature, they have a high content of organic matter. One of the most efficient ways to remove nitrates from water is to grow plants with it. One of the main sources of phosphates will be manure.
There is little indication that the human population will return to the land, but animal farms can be moved rather easily. After all, they already are segregated from vegetal production. The increased need for manure will call for a relocation of animal productions. In an expensive-energy economy, having the “fertilizer factory” on site, or at least much closer than today makes a lot of sense. This is especially true because manure contains a lot of water, although there are substantial differences between productions. Transporting water is expensive. Mixing crops and animal productions again on farms will also allow the inclusion of vegetal debris together again with the feces and urine, producing a higher dry matter content, with limited transport costs between the field and the “fertilizer factory”. Regardless of the size of the farms, I expect to see a relocation of animal production units on agricultural land. They will be spread more evenly in the landscape than today. This will decrease the density of farm animals in currently high-density areas to levels that will allow a better control of environmental issues, as well as reduce partly the risks of transmission of animal diseases. Animal production units will reappear in areas where they had disappeared because of the fertilizer that they will provide.
This evolution will also come together with a new approach of manure storage and treatment. Open-air lagoons like those that we know today will simply cease to exist. The changed economics of energy will make the capture of gases financially attractive. Manure storage units will be covered; the biogas will be collected to be used for energy purpose, for the farm and the local communities. The solid and the liquid fractions of the manure will be processed and transformed to provide organic matter and the fertilizing minerals necessary for crop production. The location of the “manure units” will be influenced by the type of animal production, and therefore by the physical quality of the manure. There will be a logistic optimization of manure collection to the crop farms. It will be based on efficiency and optimization of resources. Therefore, the new farm structure will be efficient, as much financially as environmentally. Similarly, open-ocean fish farms that currently do not collect the feces will see the financial value in recuperating the fish waste and sell it. In cities, there will be an increasing interest to recycle the sewage. The purpose will be to recuperate the organic matter and the minerals it contains. A similar approach for human waste will apply as for animal production units as I described above. This will also be integrated in the future approach of urban farming, as it will provide the necessary nutrients for an efficient urban food production. It will be a source of revenue to the cities.
In rural areas and in urban areas, organic matter and fertilizing minerals will become strategic activities. They will serve the purpose of feeding sustainably the world population.
Copyright 2011 – The Happy Future Group Consulting Ltd.