A study of lodging in cereals

Abstract

Many cereal growers fail to realise the full potential of their cereal crops because of lodging. This study has established that rain is the key factor amongst a complex range including the soil, other weather factors and the crop itself.

Lodging leads to significant yield losses. In trying to avoid lodging, growers may make management decisions on nitrogen, variety, seed rate and plant growth regulation which place limits on the potential yield of the crop.

Over the 1988, 1989 and 1990 seasons an integrated picture of the lodging process was developed. Working with hourly weather data, field observations and video recordings of individual stems within a crop it was found that stems did not lodge suddenly, but gradually, as stems failed to return to the vertical during periods when the crop was being bent over. Lodging events were more closely related to rainfall than wind speed or direction.

Among the tests devised was one which measured the force needed to pull a root from undisturbed soil. Where soil was at field capacity the force needed to pull a root free was half that required in drier soils. During rainfall surface water increased the weight of aerial parts of the crop by up to 20 per cent - thus adding considerably to the strain on roots.

Computer analysis showed that at any one time only two or three roots are likely to be taking the strain of the whole plant.

Ways to reduce the risk of lodging could include methods to encourage improved root development, the breeding of varieties with improved rooting and possibly treatments to increase compaction in the surface layers of the soil.