Nourishing waste
"In at one end and out at the other" crudely sums up two major problems associated with intensive livestock production,
especially if near to urban centres. Huge quantities of feed oilseeds and grain, grown in rural areas, are transferred between and across continents
to produce meat and milk. Once swallowed, and inefficiently converted into bodyweight, mountains of manure accumulate, to say nothing of unwanted
slaughterhouse waste. But the problem is far greater than that of transport and disposal. Hidden within the feed lie the soil nutrients upon which
feed production, out in the fields, depends. And is it returned to the land from whence it came, or does it lie, as steaming heaps of nutrients,
creating a management headache, a pollution nightmare and, probably, a noxious smell?
One-way traffic
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Soybean production has gone up by more than 50% in the last decade closely reflecting the growth in the livestock industry. Animals are not good converters of grain to bodyweight but the conversion efficiency is much improved by the addition of high quality protein such as that found in soybean meal. Soybean, being a legume, fixes atmospheric nitrogen but it has a high demand for potash, the K content in soybean seeds being five times that of cereal grains. If the soybean plant is unable to take up sufficient potash, nodulation, and therefore biological N-fixation, is impaired. |
Farmers should be aware that it is not only their sons who migrate to the cities. The international trade in feed concentrates transfers millions of tonnes of nutrients from one part of the world to another and by no means all are replaced by application of fertilizer. Taking only oilseed cake and seeds into account, in 1997 the EU imported the equivalent of 574,000 tonnes of potash, and Japan alone imported the equivalent of 142,000t. Suppliers of potassium in the form of oilseeds included Brazil (335,000t), India (73,000t) and Argentina (211,000t). Indeed Argentina 'exports' seven times the quantity of potash that it imports with fertilizers. In other words, Argentina is exporting a substantial amount of indigenous soil fertility.
Meat and bone meal, until recently a source of protein in animal feeding, may become available as an additional source of nutrients for crop production as a consequence of EU legislation following the BSE crisis. But the ban will create a deficit of about 200,000t of protein for animal feed in the EU. This corresponds to about 500,000t soybean cake, equivalent to 30,000t of nitrogen, 2,000t of phosphate and 12,000t of potash. This would add to the import of nutrients to the EU and mine even further the nutrients from soybean producing countries.
Steaming heaps of nutrients
Only a fraction of nutrients supplied with feed to livestock is removed from the farm by marketing of animal products, the bulk remain on the farm in the form of animal excrements. The more animals that are kept therefore, the greater the accumulation of nutrients. In some northern European countries, where fertilizer application has been high for decades and concerns are growing over water quality, farmers are required to calculate nutrient balances each year. A typical livestock farm would show a nitrogen surplus of 166kg/ha. Fines are imposed if levels exceed the allowable level.
So how can the accumulated nutrients be returned to where they are needed? Efforts will have to be made to rethink how best to recycle urban waste back into agriculture. Livestock waste contains not only soil nutrients but also bacteria, antibiotics and other drug and feed additive residues such as copper, arsenic and selenium. The challenges are to overcome the costs of transporting a bulky, low value material while ensuring that it contains no harmful substances that could leave the supplier with problems of product liability.
Small and sweet' or 'Big and beautiful'?
Urban dairy farmers in Karnataka State in India may have problems storing manure but seem to have no problem in disposing of it. Fuel cakes sell for 15-20 rupees per 100 and manure for 250-300 rupees per tonne or in exchange for forage. If, at small scale, the problems are manageable, is this a lesson that should be noted? A study by FAO suggests that urban livestock production, particularly in the fast developing countries, is not sustainable in its present form. As the environmental hazards are more widely appreciated, and infrastructure improves, the trend will be to return livestock production to the rural areas where it will form one part of a large, integrated mixed farm. Nutrient recycling will be easy and profitable. Until such time, growers of feedstuffs must concentrate more attention on soil fertility remembering that 'what goes out' does not automatically 'come back in'.
