Within the manual Protocols for experimental plot sampling, handling and processing of cereals in field experiments by G.J. Rebetzke (Greg.Rebetzke@csiro.au), A. van Herwaarden, B. Biddulph, C. Moeller, R. Richards, A. Rattey and K. Chenu.
Plant height, lodging, and seed shattering can differ substantially between lines. They are readily scored.
As each line reaches maturity (rapidly losing green colour in the leaves, stems and ears), a quick assessment should be made of:
- a. Canopy height: Plant height be given to the nearest 5-cm for the average culms in each plot. This is achieved simply by identifying a representative part of the plot and holding together a handful of stems. A graduated stick marked to every 5cm is then placed against the bundle and height recorded to the tip of the ear for an average stem (ignoring the awns) (Fig. 22).
- b. Crop lodging: Lodging can occur before flowering but is commonly scored at maturity (Fig. 22). To score lodging, estimate the percentage area of plot that is lodged and then estimate the angle of stem lodging (eg. an angle of 10∘ from the perpendicular is scored as 10 whereas prostrate stems are scored as 90). Lodging for the plot can then be calculated as: (% plot area lodged x angle of lodging from vertical)/90. For example, a plot where approximately half the plot is estimated to be lodging at 45∘, the plot lodging score is calculated as (50 x 45)/90 = 25. A similar assessment should be made if lodging occurs before, at or soon after flowering. When lodging occurs this early, mutual shading may reduce crop yields. Be sure to also record the date when lodging was first observed as crops lodged early in the season sometimes straighten (evidenced by a small bend at the base of the stem).
Figure 22. Measuring plant height (left) and lodging (right). The lodging score for the plot on the right reflected two separate lodging scores (front half of plot was lodging angle of 60∘, and back half was 40∘): (50 x 60)/90 + (50 x 40)/90 = 56
- c. Shattering: Seed shattering is expressed as percentage of seeds released from main culm spikes at maturation, and is scored in the crop stand (Fig. 23). Main culm spikes are often larger than spikes formed on tillers, and the main culm is often the longest on an individual plant. In cases where you have detected shattering in a plot (i.e. seeds on the ground, seeds exposed and not covered by lemma and palea, rachis visible), randomly select five main culm spikes in different areas of the plot. Estimate the percentage of seeds abscised for each spike. The shattering score for the line is the average of the five estimates. For example, a score of 20 indicates that 20% of the seeds have fallen out.
Figure 23. The timing of crop harvest influences the shattering score. In lines susceptible to shattering, the score will increase with time past the optimal harvest date. The photos show an example of 30-40% shattering.
Appendix 1. Text description of phenological scale, Zadoks decimal code (DC).
Appendix 2. Picture description of phenological scale, Zadoks decimal code (DC).
Zadoks JC, Chang TT, Konzak CF (1974) A decimal code for the growth stages of cereals. Weed Research 14(6),415-421. doi: 10.1111/j.1365-3180.1974.tb01084.x
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