Implementation of artificial methodology for generating lodging data for the purposes of VCU National Listing.

Background

This report summarises the third year’s results of a DEFRA-funded investigation of methodology for assessing resistance to lodging in maize varieties.

Lodging is a major/intermediate NL -VCU character for maize. Lodging and brackling are caused by high winds, typically in the period leading up to harvest, but sporadically earlier in the growing season. The ability of a forage maize variety to remain erect is an important characteristic in determining its yield, quality and manageability.

The current NL trialing system necessarily relies on small plots of maize. It is sometimes difficult to quantify lodging in a way comparable to maize grown on the field scale. The force of the wind may vary within a trial due to height differences between varieties. Susceptibility to lodging also differs with growth stage. Thus the tendency of a variety to lodge or brackle is only fully revealed in trials exposed to windy conditions at the critical stage for this variety.

In France, a method has been developed to apply a uniform lodging pressure, thereby overcoming many of the problems associated with incident determination of resistance to lodging. A horizontal steel bar is pushed through the trial in mid-summer post tasselling, followed by assessments of plant lodging and subsequent recovery.

Results from the first and second year of trials indicated lodging pressure applied post tasselling at between 40cms and 80cms correlated with incident results seen in NL and Descriptive List trials (figure 1). However results showed that the timing of application affected the methodology. A further years testing was required to assess the sensitivity of the methodology and the feasibility of utilising data produced from lodging assessment in NL decision making.

Aims of project

§  To validate a methodology for consistently applying a force to cause lodging on all varieties and therefore fairly assess they’re true potential to lodge.

§  To confirm the methodology can account for variation in crop maturity.

·  To assess the feasibility of using the methodology as a part of the VCU trial procedure

Methods

The assessment was conducted at Cambridge NL trial sites, with the NL2 trial. The trials consisted of 3 replicates, using plots 4 rows wide by 12m long. Pathways of 2m were cut out from the ends of these plots reducing the plots to 10m long. The two centre rows of the plots were thinned to a target population of 105,000 plants per ha.

Variable lodging pressure was applied by driving a tractor with a mounted horizontal bar protruding into the plot at set but different heights (0.6m).

Lodging treatment was applied via this method to the plot end directly following 50% tasselling of all control varieties. Records were made on 1-9scale (1=all plants lodged, 9= no plants lodged) of plants lodged (plants at >30° from the vertical) directly following each treatment. Mean crop height was also recorded for each plot.

Results and Discussion

Lodging pressure at 60cms showed substantial lodging damage but produced only a weak correlation with previous performance of NL2 in terms of lodging resistance (figure 2) and brackling resistance. Comparison of individual site data for same varieties trialed at Cambridge in NL1 (2003) and NL2 (2004) showed no correlation. Which suggest that the lack of correlation was not due to site or year effect. Co-variate analysis was carried out with height which showed no relationship. Maturity was already accounted for in the timing of the treatment.

It should also be considered that these assessments were carried out using a tractor mounted bar in place of a hand assessment as in 2002. There were a number of advantages could be identified using a tractor, such as speed of assessment and repeatability, however it would appear from these results that sensitivity is lost with the tractor mounted assessment resulting in a weak correlation.

Overall the results of this trial would suggest that this methodology is not sensitive enough to assess NL material of close similarity in lodging resistance. But previous work would suggest that it is perfectly adequate at assessing the extremes of the lodging resistance range.

Preliminary Conclusion and Further Work

The tractor run assessment proved to be quick and easily repeatable. The treatment and assessment can be carried out within 1 day. Potentially the method would appear suitable for use in National List testing. However the results from the third year of trials indicates that the mechanical methodology lacks the sensitivity to adequately assess the range of NL material for either lodging or brackling, further investigation of methodology should cease until the methodology is further developed in France.



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