Our planet is hungry now. It will be hungry in the future. World population is expected to reach 9.5 billion by 2050 and possibly as many as 24 billion by 2150. Although these long term forecasts are speculative, whatever the future holds the planet will continue to benefit from the use of fertilisers. If the more extreme predictions of population growth hold up, then fertiliser performance will be vital if western civilisation is to survive.

All plants need nitrogen to grow, but as most can absorb it only from the soil in the form of nitrates or ammonia, mankind soon learnt that it was helpful to add ingredients to the soil to aid productivity. Therefore, for most of human history, we have been feeding ourselves by using a proven method of adding animal dung and plant waste, rich in nutrients to increase crop yields.

The development of an industrial process to manufacture ammonia in the early 1900’s changed the way we viewed agriculture. This meant the application in liquid or solid form of ammonium nitrate, urea-ammonium sulphate, urea-ammonium nitrate (UAN solution), urea, dairy manure and poultry litter.

Today, synthetic nitrogen fertilisers have led us to the modern world of mass production on farms, increasing food production by 35-50% since the 1940’s. They are used in all but the poorest of countries and form a base part in the production of every meal we eat.

In fact, we depend on them for our survival. As Wikipedia notes, “Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizer. Global market value is likely to rise to more than US$185 billion by 2019.The European fertilizer market will grow to earn revenues of approx. €15.3 billion in 2018.”

Whilst this has been a great success story in the progress of mankind, it is far from the end of the story, because our current methods have several major flaws.

1. Energy. The production of nitrogen fertiliser is energy intensive, accounting for around 50% of the total fossil fuels burned in agriculture. Burning fossil fuels produces the greenhouse gas carbon dioxide, which causes climate change, which affects farmers more than most.
2. When applied to fields, only about 50% of the nitrogen in fertiliser is actually absorbed by plants. The excess is washed out of the soil into rivers and lakes where it promotes the growth of algae. Excessive nitrogen fertiliser use can cause algal blooms that can kill life forms by blocking out light and lowering the oxygen content in the water.

This is a problem being tackled by many government worldwide, including in Western Australia where legislation has been implemented to ensure the “development and promotion of low impact fertiliser products” in an attempt to achieve “a goal of 50% reduction in nutrient loss to waterways and wetlands” by 2018.

3. Greenhouse gases Excess nitrogen fertiliser in soil can also be converted into nitrous oxide by some bacteria. Nitrous oxide is a very strong and long-lived greenhouse gas, which currently has rising levels in the atmosphere. Agriculture is a major contributor to this increase and accounts for over 80% of total nitrous oxide emissions.
4. Expensive The cost of producing and transporting nitrogen fertilisers puts them out of reach of many farmers in developing countries, especially those in more remote and barren areas. Ironically, the same areas where poverty and malnutrition mean that increased crop yields are most needed. As fossil fuels are depleted and energy prices increase farmers in these countries need alternative, more affordable solutions to supply nitrogen to their crops.

Furthermore, the application of fertilisers is an applied science. Less educated farmers need to know what they are putting in their fields and when, if yields are to be maximized. As crops change, different products are needed. As prices change, different amounts need to be applied to maintain profitability.

This is a growing problem, which makes the use of fertiliser an increasingly complex puzzle. As a study by Charles Mitchell of Auburn University and Deanna Osmond of North Carolina State University notes “Ammonium nitrate (34-0-0) formerly was the standard but has become difficult to find and transport. Solid urea-ammonium sulphate blend (33-0-0) is very acid-forming and subject to volatilization. Solid urea (46-0-0) has a high risk of volatilization losses during hot, dry summer months when surface applications are not incorporated. This is especially true when urea is applied on crop residue in a high pH soil.”

As you can see, there are many factors to take into consideration when using nitrogen based fertilisers, which means that the search for a replacement that is cheaper, better for the environment, easier to use, consumes less energy and is less exposed to price fluctuations is sorely needed.

And science is working hard to find a replacement, and has already come up with a number of alternatives to traditional nitrogen based fertiliser methods. These include;

1. Slow- and controlled-release fertilisers Releasing ammonia and nitrate into the soil more gradually over a period of weeks or months, reduces the chances of run-off and are a generally more effective way of aiding plant growth. They are however typically more expensive than regular fertilisers.
2. Simply better practice. Scientists at the International Fertilizer Development Centre based in the Netherlands, believe that frequently farmers turn too quickly to nitrogen based fertilisers. In response to this they have developed an Integrated Nutrient Management System which they believe can increase yields more effectively. They claim that, “The method has the potential to increase yield levels up to 4,500 kg/ha with 40% less fertiliser use while protecting the environment.”

Other studies also recommend a more detailed analysis of farming practices, particularly in developing countries where farming practices are based on traditional methods founded before a modern understanding of agriculture.

3. Leaf absorption As leaves, as well as roots, can absorb nutrients, the Virtual Fertilizer Research Centre (VFRC) is conducting research into new methods of applying fertilisers, believing that they may hold the answer to more efficient absorption and therefore reduced usage.

“This direct path of nutrients entering the plant near the assimilation point might enhance fertilizer efficiency.”  However, they do acknowledge that, “The efficacy of foliar fertilizer application is ambiguous because little is known about the plant processes governing uptake and utilization.”

4. Different crops For hundreds of years man has employed crop rotation methods as a way of increasing fertility in soil. The planting of members of the legume family — such as peas and beans, as well as clover — often as a winter crop, can produce ammonia from naturally found nitrogen gas in the soil. Bacteria living within the roots of these plants provide the plant with ammonia in exchange for sugars. The relationships can be so successful that excess ammonia can be released into the soil, which farmers appreciate for the benefits it gives the next harvest.

The downside being that in drier climates, legume winter crops can consume valuable water from the soil that is needed for the main summer crop.

As further research is carried out, doubtless more solutions will be found. One such solution is the mass production of ammonia-producing bacteria, which could prove cheaper than industrially producing ammonia.

Since legumes have such a clever solution to accessing nitrogen, scientists are studying whether it is possible to cultivate ammonia-producing bacteria in the root systems of other plants by way of genetic modification. Since ammonia is produced most efficiently within the host legume plant, copying this method to enable wheat or rice to host ammonia producing bacteria would be an historic development.

No one can be certain what new discoveries will be made to ease our impending food crisis, but certainly something needs to happen if crisis is to be averted.

The most likely outcome is that several technologies will be developed, and need to be applied to replace our valuable nitrogen fertilisers, as there is unlikely to be a ‘one size fits all’ solution. Until these new products and methods are found mankind must take greater care of the resources it has. As Charles Mitchell of Auburn University says, “Given the high cost of nitrogen and the environmental consequences of losses into surface water and groundwater resources, nitrogen fertilizers must be managed very carefully,”

The one question remaining is whether the new developments can come into use in time to feed the world.