Baker C J, Sterling M, Berry P (2014) “A generalised model of crop lodging”, Journal of Theoretical Biology 10.1016./j.jtbi.2014.07.032
“A generalised model of crop lodging” was awarded College Best Publication Award August 2014
Lodging, the term used to describe the flattening effect of high wind speeds and heavy rainfall on trees or crops, has a significant economic impact on the UK crop industry. Research in the School of Civil Engineering seeks to make recommendations for improvements in the agricultural industry to reduce the sometimes devastating effects. To clarify, this study does not look at crop circles; caused by clever pranksters or aliens, depending on your preference!
Lodging costs the UK agricultural industry heavily. For example winter wheat, in a severe lodging year (which occurs on average every three years) costs the agricultural industry in the UK an estimated £105m. The average annual cost associated with all cereal crops is of the order of £200m. It is clear then that to reduce lodging even by a small amount, could mean the potential savings are significant.
Researchers in the School of Civil Engineering have studied lodging for many years, - indeed the current Head of School worked on this problem as a young and eager Post-Doctoral Research Fellow towards the end of the 1990s. The primary focus at this time was on winter wheat, and the cause of the lodging, which was much contested among farmers. Two types of lodging were identified: ‘root lodging’, where the root anchorage system failed and the plant uprooted, and ‘stem lodging’ where the stem buckled, usually near the ground. The circumstances under which lodging occurred and thus the appropriate response was also disputed: Some advocated rolling the ground to increase soil strength whilst others advocated the use of plant growth regulators to reduce the height of plants and thus to make them more “stable”. Alternatively some argued for selective breeding of crops to encourage those crop traits that reduced lodging (although there was no agreement on what these traits actually were). The School collaborated with colleagues in agricultural and environmental consultancy group, ADAS, to investigate the problem. With a ‘typically engineering’ style approach – researchers built a mathematical model of the soil/crop/weather system, using classical structural analysis principles. This proved to be very useful and was able to identify the plant characteristics, soil types and weather conditions under which the different types of lodging occurred, and thus enabled alleviation methods to be applied in a rational way. This work was supplemented by experimental work to measure a range of winter wheat parameters – crop height, stem and root strength, natural frequency etc., and by the use of a mobile wind tunnel that could be taken out into fields to blow crops over. This work was incorporated into ADAS guidance for the farming industry on how lodging can be reduced.
More recently there has been increased interest in the need to reduce lodging in other types of crop, such as barley (of interest to beer drinkers), oats (of interest to porridge lovers) and oil seed rape (used to make cooking oil). The nature of these crops is very different from winter wheat – with some having different types of root (a long tap root rather than a root ball), and some having interlocked plants in the latter part of the growing season.
The generalised model has important practical significance; it has identified those plant, soil and weather characteristics that most influence lodging for a variety of different types of crops, and also allows the variation of lodging risk to be determined. It thus provides important information for decisions to be made on the value of changing any of these of these plant characteristics.
Furthermore, because the new model is based on wind speed and rainfall probability distributions it allows for consideration of the effects of potential climate change, as the current climate predictions are also based on such distributions. This is an important new area of investigation, but there is still much to be done. Many of the parameter values in the new model have had to be assumed (or guessed!) and extensive field tests are required to obtain these values and to validate the assumptions made in the model. Future research could have significant impact on the UK’s ability to protect its crop yield in an increasingly complex climate.
Summary by Professor Chris Baker