Closing yield gaps through nutrient and water management

Could ‘sustainable intensification’ be the solution to meeting future food needs and reducing agriculture’s negative impact on the natural environment? Gordon Conway has defined this approach simply as ‘producing more while using fewer resources’, and the practical implementation of the term has been increasingly scrutinised and the subject of controversy. Indeed it is the topic of an upcoming Chatham House Food Security 2012 conference in London entitled, Sustainable intensification: miracle or mirage?

A recent paper in Nature discussed the possibility of agricultural intensification and specifically of closing yield gaps – the gap between yields which are attainable and yields which are observed – for 17 major crops. The variability in yields achieved for different crops was found to be largely due to differences in fertiliser use, irrigation and climate.

Authors of the paper found that closing the yield gaps by 100% would result in an increase of crop production for most major crops of 45% to 70%. Significant opportunities for intensification of major cereals exist in Eastern Europe and sub-Saharan Africa. Reaching this level of yield gap closure would, however, require increases in irrigation and nutrient application, actions that are not necessarily in line with the paradigm of sustainable intensification. Sub-Saharan Africa does, however, have large untapped water sources that, if used responsibly and, yes sustainably, could improve food production.

The authors argue that increased irrigation and nutrient application could be offset with decreases in other areas. For example, a reduction in the use of nitrogen on maize, wheat and rice by 11 million tonnes would not impact current yields. Indeed opportunities exist to reduce nutrient overuse and inefficiency while also increasing production of major cereals by 30%.

The authors do recognise that intensifying agricultural production is not always practicable, identifying such barriers as ‘regional land management policies, limits on sustainable water resources and socio-economic constraints’. Further they note alternative forms of farming such as conservation tillage and the use of high-yielding hybrids as viable options for minimizing environmental damage. Identifying opportunities for increasing food production alongside decreasing agricultural inputs will, no doubt, be an ongoing topic of investigation.