Agriculture Reference
In-Depth Information
component, grain filling). This relationship is particularly interesting because of its
predictive nature. It can be interpreted as an early effect of take-all on nitrogen and
carbon assimilates, limiting re-mobilisation from stems and leaves during grain
filling.
-
-
-
Figure 14.3. Disease-yield loss relationships established from field experiments on winter
wheat crops infected with take-all. Yield loss function of cumulative disease incidence
-
between sowing and flowering is established for low (N ) and high (N+) levels of nitrogen
fertilisation. (From Schoeny et al ., 2001).
This was confirmed in a subsequent study showing that although wheat plants with
severe take-all infection took up more nitrogen per unit of efficient root than
uninfected plants, this compensatory response was insufficient to give nitrogen
accumulation levels equivalent to those in healthy plants (Schoeny et al., 2003).
Thus, split applications of nitrogen with the amount of nitrogen adapted to the lower
capacity of infected root systems to absorb nitrogen, as proposed by Lucas et al.
(1997), might be of value.
14.3.3 Importance of cultivation management between crops
The role played by the intercrop period has not received adequate attention from
plant pathologists in the analysis of soil-borne pathogen epidemics. The severity of
rhizoctonia root rot on wheat has been linked to the presence of volunteers and
weeds growing in the field between harvest and planting of the subsequent crop.
These plants act as a 'green bridge', maintaining or increasing the potential
inoculum of many plant pathogens, such as R. solani AG-8 in particular (Smiley
et al., 1992). Dulout et al . (1997) compared the effects of wheat volunteers,
blackgrass ( Alopecurus myosuroides ) and bare soil on soil infectivity and soil
conduciveness to take-all. They showed that both wheat volunteers and blackgrass
maintained soil infectivity at a higher level than bare soil. Soil conduciveness
was reduced by wheat volunteers whereas bare soil and blackgrass were highly
Search WWH ::




Custom Search