After being used in artificial fertiliser, some of the phosphorus ends up in the seas, and it is difficult to retrieve it from there. Some of the minerals, such as phosphorus, are obtained by mining, and the supply is limited. Using mineral fertiliser has two disadvantages. They have shown that we apply too much manure at certain places in Sweden, and compensate for this by using mineral fertiliser, also known as artificial fertiliser, at other places. They conclude that it is possible to use the nutrients much more efficiently than at present. Uno Wennergren and his doctoral student Usman Akram have studied conditions in Sweden and Pakistan.
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We must be made to understand that it should be a system with the task of returning nutrients to agriculture”, says Uno Wennergren. “In the long-term, I believe that it will be necessary. And it’s not just animal manure that can be used, but also human excrement, he points out. Uno Wennergren uses mathematical models to calculate how much it would cost to transport the biofertiliser back to the fields in the most efficient manner. They map the places where fertiliser is available, in other words the places where livestock is kept and where people live, since most of the food ends up in urban areas. The researcher have, for example, detailed knowledge about which crops are cultivated in which fields all over Sweden, since farmers report this when they apply for EU support. His research group uses data from many different databases to determine where nutrients are needed in agriculture and the amounts that are needed. It is for this reason that he is looking at how fertiliser can be transported back to agricultural fields such that the nutrients become elements in a circulation. This is why we need to close the nutrient system as tightly as possible”, says Uno Wennergren. But if we use more fertiliser than the plants can absorb, the excess nourishment causes problems in the form of eutrophication of the sea and lakes. “Since the nutrients are needed in our food production, people are keen to force ever-increasing amounts of nutrients into the system. But the same nutrients can, of course, also promote the growth of other plants, such as algae in water courses. The excrement from both livestock and humans contains quantities of nutrients that can be used as plant fertiliser. We humans either eat the plants directly, or animals eat the plants and we then eat the animals. Let’s start at the beginning: plants need nutrients, such as nitrogen, phosphorus and potassium. In Sweden, the way in which nutrients are managed in agriculture plays a major role for other reasons. But they are stuck at the wrong level and cannot climb out of poverty”, says Uno Wennergren. “If these people could buy fertiliser for a period such that the harvests increased, they would be able to sell part of the harvest and buy fertiliser with the profit they make. The impoverishment depends to a large extent on farmers not being able to afford fertiliser, and the disappearance of nutrients from the soil each time the cultivated plants are harvested.
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Hunger and starvation principally arise in rural areas, where the soil has been impoverished and gives harvests that are too small.
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A billion people who are today hungry are already demanding that we manage food production better”, says Uno Wennergren, professor in theoretical biology in the Department of Physics, Chemistry and Biology. The problem is not that the population is increasing, but that we do not use the necessary resources efficiently. There’s no difficulty in growing food for 11 billion people on the cultivated area we currently use. Photo credit Charlotte Perhammar“The world’s population is now 8 billion and forecasts point to 11 billion in 2100 – when those born today are pensioners. Uno Wennergren is looking at how fertiliser can be transported back to agricultural fields.