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Agriculture, nutrient balance, Eutrophication


Let’s start with a simple analogy: if a person eats more than they need, they gain weight. That is: if our feed inputs (kilojoules in) are greater than our outputs (exercise — kilojoules out) then we will gain weight (kilojoules in storage).That’s our fat. If, on the other hand, our feed inputs are less than our outputs, then we will lose weight.And if our inputs are the same as our outputs, our weight will remain constant. In general, the further away you are from an ‘ideal’weight, the greater the health risks. And yes, other aspects of your body management — smoking, drinking, too many late nights and B grade movies will also impact on your health — but the excess weight is important. It’s all about balance. An agricultural enterprise is very similar: if inputs of feed and fertiliser (nutrient in) exceed the sum of the products sold or exported from the property (nutrients out), then there will be nutrients for storage in the soil or loss. The immediate nutrient losses can cause eutrophication of waterways, and the stored nutrients represent a potential for loss in the future when stored in the soil. So this is the environmental risk — too much “fat” in the agricultural system!

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