The triazole fungicide, Caramba, is well known for its growth regulatory effects which form an essential part in creating an optimum canopy and optimum yields in oilseed rape. But it is less widely known how these effects come about. Research work has demonstrated that the growth regulator effects of metconazole are due to the fungicide's influence on plant hormones levels, explains BASF.
An application of metconazole has been shown to reduce plant gibberellins but increase cytokinins level. The gibberellin effect reduces apical dominance and reduces stem length as well as diverting nutrients to the axillary shoots and roots. It also initiates branching and rooting, which protects against lodging and produces a more even canopy, a benefit that many oilseed rape crops could do with this spring.
The cytokinin boost differentiates tap and adventitious roots, increases chlorophyll production and increases cell division in shoots and roots, leading to improved rooting, more vigourous plant growth, more effective photosynthesis and better nutrient utlilisation.
"Oilseed rape needs a strong tap root to access water and good adventitious roots to access nutrients. Where roots are limited, so are water and nutrient uptake. Better-rooted crops are potentially better yielding ones and Caramba has been shown to improve rooting," says Diane Heath, BASF Oilseed Rape Product Manager.
Dr. Peter Berry of ADAS High Mowthorpe concurs that good rooting at depth is important in rape in order to maintain the yield potential of the crop.
"The root system must be able to scavenge for soil moisture and nutrients and be able to satisfy the crop's demands at the critical pod filling stage. At this time drought can be a problem, resulting in premature crop senescence and reducing the length of the seed filling period," says Pete.
He explains that HGCA and BASF funded work has shown that oilseed rape crops frequently have insufficient roots at depth (below 40 cms) to fully explore the soil. "Around 50% of crops suffer sub-optimal rooting below 40cm depth, which could be limiting and ultimately be affecting yields. In a dry summer when the crop is reliant on extracting soil water from depth, crops with a poor root system suffer from drought. The use of the triazole fungicide Caramba (metconazole) has been shown to encourage greater root exploration at depth."
"Root Length Density, which is the length of roots (in centimetres) within each cubic centimetre of soil (cm root /cm3 soil) has been used as a key measurement. The use of Caramba improved Root Length Density. By reducing lodging and by enhancing root growth, it also enhanced yields over other treatments," Dr. Berry reports.
