The Permacultivator - Journal of Cool Climate Permaculture
Agriculture ranks second after the energy sector in greenhouse gas production (ABC Landline, 27th June 2004)! How is that possible, as plants are photosynthetic and fix carbon dioxide? The answer lies in wasteful approaches to almost everything a farmer does, compounded by unnecessary trade and long-distance transportation of produce. It is ridiculous that the energy content of any food is outweighed by the energy cost of its production, processing and transportation. This imbalance is a recipe for disaster.
There are in fact three adverse greenhouse effects - warming by carbon dioxide itself, heat stress of leaves by restriction of stomatal opening, and nutritional erosion of seed products. A combination of the first two effects will obviously diminish the yields of staple crops. But even with adequate yields, the more atmospheric carbon dioxide concentration increases, the less sulfur and nitrogen content our staple grains will possess. High quality proteins will be replaced by proteins of lesser quality, and the total amount of protein per seed will decline. This was my prediction in a letter to the Seed Savers' Network Newsletter in 1992, set out formally in my book Carbon Dioxide and Plant Responses (1997), then confirmed independently by other researchers 10 years after the original prediction.
It is estimated that two-thirds of Australian agriculture's greenhouse gas emissions come from introduced animals, chiefly herbivores. Cattle and sheep produce about 250 litres of methane per day each, representing about 15% of the feed they consume. This in turn represents about one-third of our total grain production. Lot-fed beef cattle are the most wasteful, with an estimated eight units of grain needed to produce one unit of meat. Beef consumption and lamb consumption have risen 2.5% and 1% respectively in the past year, so despite the higher monetary costs of these meats, too many Australians don't really care about the impact of their diet on the environment.
The remaining one-third of agricultural greenhouse gas emissions comes from nitrogenous fertilisers, manures and effluent ponds. Let's look at the greenhouse burden of producing nitrogenous fertilisers. We all learned about the Haber process at high school. At high temperature and pressure, nitrogen and hydrogen are catalytically combined to form ammonia. The production of urea, which is broken down to ammonia by soil bacteria, is very similar, requiring energy supplied by natural gas. It takes even more energy to produce nitrate from some of that ammonia. Ammonium nitrate clearly has an unacceptable cost in terms of carbon dioxide production!
Attention has focused on ammonium nitrate since its use in the bombs detonated in Bali. Manufacturers have now refused to sell ammonium nitrate as such (Nitram). But in more complex mixtures, ammonium nitrate is still being made available. One such combination is 50% ammonium nitrate and 50% diammonium phosphate. It is business as usual -ammonium nitrate is often the major nitrogenous component of synthetic fertilisers. (See Table )
However, very few plants prefer to take up ammonium ions. There are bacteria in the soil that convert ammonium to nitrate, which is utilized by most plants. But if too much nitrate is present, this can accumulate in plant products, giving rise to the carcinogen nitrosamine in the intestines when these plant products are consumed. Alternatively, surplus nitrate is broken down to oxides of nitrogen, which have their own greenhouse contribution! Farmers tend to apply nitrogenous fertilisers on just a few occasions, and excessively, exacerbating the worst possible scenario.
The critical limiting nutrient for crop growth in the future will be phosphorus. Most readily accessible deposits of phosphatic fertiliser have been mined already. This was made into superphosphate, and applied year after year, with only about 30% of each application actually available to crops or pasture plants. As phosphorus has become increasingly scarce, and more expensive, the amount of phosphorus removed with the crop has become a useful parameter to consider. Cereals are relatively low in their requirement - about 3 kg of P removed per tonne of grain produced. Legumes are intermediate, but with legumes, there is a key advantage in reducing the need to apply nitrogenous fertiliser - to zero. Canola is excessive - with more than twice as much P removed per tonne as for any cereal (7 kg of P removed per tonne of grain produced), plus there is the need to provide all of its nitrogen. A truly economic look at plant nutrition and fertiliser costs would place canola in the 'no thank you' category. None of this investment in N and P is reflected in the final product for human consumption, i.e. an oil of dubious quality. Margarines made from canola oil have been found to promote macular degeneration, a disease which is on the increase in Australia.
Water: It was stated on ABC Radio on 14 September 2004 that agriculture uses 70% of water in Australia - cities etc. use only 30%. Well, we are not getting a very good return on that massive usage, are we? The irrigators are winging constantly despite the fact that research has shown how to maintain yields with half the previous water usage. This is done with split root irrigation, and it works extremely well with citrus trees and grapes. Ducting irrigation water with enclosed pipes instead of open channels would save another order of magnitude, and get rid of irrigation channel weeds at the same time. Irrigators complain about the costs of infrastructure, but ignore the savings. However, cotton and rice are water-wasters, and we should ration both. These are really tropical crops, best grown in countries with monsoonal rainfalls.
Amalgamation of farms is happening increasingly. This leads to simplification in crop production and excessive clearance of native vegetation. This may appear to be 'efficient', but only in terms of the crops actually produced, not in absolute terms, where no one is measuring the productivity and biodiversity that has been foregone. The most productive areas of vegetation are complex, with trees, shrubs, vines, herbs and grasses all growing together. The most productive agricultural systems mimic nature in this respect, e.g. gardens involving multifunctional tree crops in Sri Lanka, or cork oak forests in Portugal. Reject wines that have plastic plugs or Stelven seals!
Annual crop monocultures dispense with the protection against extremes of weather provided by plant species diversity, and are more prone to stresses and consequent sub-optimal performance. The lack of deep-rooted species allows water tables to rise, bringing salt to the surface in many areas. More soil is lost to erosion by wind and water. The most productive farms in absolute terms are not the largest - they are among the smallest, involving more people, a mixture of plant types, better retention of soil and soil organisms, and less heavy machinery.
Pesticides and Herbicides:
We are constantly releasing new pesticides without full and proper assessment, and then retiring them with hindsight. Look at methyl bromide, released in 1894. This wretched compound is organic in name only, but was espoused by Peter Bennett as a way of converting lawn into garden in all six editions of his book 'Organic Gardening'. Finally it has had its approval withdrawn world-wide. Look at the simazine herbicides. In the 1980s they were said to double the nitrogen content of leaves! There was a confused discussion about concentration versus actual amount of nitrogen per leaf. Meanwhile, these herbicides accumulated in ground-water. And simazine-resistant canola varieties had a substantial yield penalty, of between 10 and 20%. Eventually simazine herbicides were shown to be endocrine disruptors. First banned in France, they have now been banned in the whole of the European Community, as announced in 'The Garden' of September 2004. Australia will be the last to follow suit, as usual. The basic problem with all pesticides is that they are non-specific, affecting beneficial organisms and humans as well as pests. We should proceed as if there were no such thing as a safe agricultural chemical - then we would be right nearly all the time.
J 46 Summer 2004 - Autumn 2005