KICKING THE HABIT: FERTILISERS
It is estimated that around 50% of the food produced today in conventional farming systems would not exist without fertiliser applications. Plants require nutrients to grow and to produce the seeds and fruits that we eat. The selective breeding of high yielding varieties of crops has meant that yields have dramatically increased since the 1960’s to keep pace with a rising global population. However, these productive varieties only have high yields when they are ‘fed’ with fertilisers containing nitrogen and phosphorus. The question is how can we increase the efficiency of use of fertilisers, thereby reducing their use, and decrease their side-effects on the environment?
Phosphorus fertilisers contain superphosphate, the major source of which comes from mining phosphate rock. Its production leads to hundreds of millions of tonnes of wate, although heavy metals and other impurities still sometimes make their way into the fertiliser and then the soil. When rain washes it from fields into freshwaters, the sudden influx of phosphorus fuels harmful population explosions of algae.
Nitrogen is usually in the form or ammonium or urea, but microbes in the soil soon convert any excess into other nitrogen-based molecules which behave very differently. What that means is that poor timing and over application of nitrogen fertilisers are not only inefficient but lead to water pollution (in the form of nitrates, where as much as 30% can end up in water courses), air pollution (in the form of ammonia gas) and climate change (from the gas nitrous oxide).
STRAIGHT FROM THE EXPERTS
Alternative approaches are being sought to the ‘high input’ approach to farming because of the negative environmental consequences of fertilisers, such as aquatic pollution, loss of soil biodiversity, and increased greenhouse gas emissions. However, getting rid of such chemicals altogether is, for the foreseeable future at least, unrealistic. By identifying situations where they are being applied unnecessarily, or finding non-chemical alternatives to inorganic fertilisers (combined with interventions to mitigate the negative environmental impacts of those we do use) the aim should be to develop integrated, sustainable systems that reduce and optimize inputs but also maintain food supply