Options for increasing global agricultural production are limited. One option is to increase the land area devoted to crop production, but this alone will not meet future needs. A second option is to raise the yield per unit area by closing “yield gaps,” which is the difference between potential and actual yields per unit land area under cultivation. There are four potential ways to increase yields per unit area:
- improved crop varieties,
- use of fertilisers and pesticides,
All of these technical interventions have been achieved in developed countries, to greater or lesser degrees, as farmers focus on closing the yield gap per unit of resource input (e.g. fertiliser, pesticides, water, labour).
Regardless of the strategy pursued, the application of fertiliser is a key component in increasing agricultural production. Despite a basic understanding of the potential payoff in the use of fertilisers, farmers in less-developed countries are reluctant to trade their low-risk system (i.e. low-input, low-yield) for a high-risk system (i.e. high-input, potentially high yield). Moreover, the opportunities to close yield gaps are highly variable among regions due to physical restrictions of climate and soil but also socio-economic limitations of crop selection, access to inputs (including germplasm, fertilisers, water and labour or mechanisation), access to markets and the income levels of farmers (and hence their ability to invest).
Aside from a general need to increase agricultural production globally, local growth in rural populations intensifies the need for increased production efficiency as demand rises and field sizes diminish. However, there are thresholds beyond which the cost of inputs (i.e. inorganic fertiliser) fail to lead to corresponding increases in yield.
Beyond economic inefficiency, overuse of commercial inorganic fertiliser can also result in a decline in soil condition and structure, including reduced soil carbon content, soil water holding capacity and porosity. These changes may compromise the long-term ability to support food production and pose long term threats to neighbouring ecosystems as well as surface and groundwater resources.
Use of organic fertilisers (i.e. manures, crop residues) can counter the trends of many of these problems by increasing soil organic carbon, improving soil structure, tilth and water holding capacity. These improvements require a commitment to sustainable land management practices that incorporates a broad swathe of land- and water-management approaches, of which the use of organic fertiliser is just one component.
Because of the global variability of environmental and economic conditions in which farmers must operate, the use of fertilisers alone does not offer a panacea. Even where fertilisers and pesticides are affordable and readily available to close yield gaps, other inputs may play an equal or greater role in increasing agricultural production from place to place.
YThe global total quantity of nitrogen, phosphorous and potassium (NPK) fertiliser used on croplands reached 172.2 million metric tonnes in 2010/11 of which 60.5 % is N based. Developing countries are applying increasingly more N fertiliser, while at regional scale East Asia tops the consumption. The world average fertiliser consumption is 138 kg/ha. Many African countries use less than 10 kg/ha while other new economies apply well over 500 kg/ha.