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 counts are useful in understanding factors contributing to leaf area, canopy development, and ultimately yield variation. They can also provide information on quality of the seed lot, seed bed and conditions at sowing.
Method
Between the 2 and 3 leaf stage is the best time to make observations on plant establishment. It is late enough that most plants will now survive and early enough that few or no tillers make it easy to do counts quickly.
- If establishment is uniform then 2-3 counts per plot may suffice. If plots are more variable then more counts per plot may be needed to gain a reasonable estimate of plant density.
- Randomly drop 50cm piece of white dowel into plot and then align between two rows. Count the number of plants on either side of the dowel and record. Do not count edge rows. Repeat as many times as required.
- Digital photos such as the photo below can be used to count plants as long as a scale (ideally a ruler but if no ruler is available then the known distance between rows can act as a scale) is given in at least one image, and photographs collected at the approximate same height and position in each plot (e.g. Fig. 7). We use a Panasonic® Lumix TZ10 for our photos. This camera allows good control of white balance and has the Leica® precision lens.
Figure 7. Image illustrating the commonly observed variability between rows, and subsequent need to count plants across a minimum two adjacent rows at multiple locations in each plot
Other resources
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
Notes and troubleshooting tips
Literature
Download complete manual: Protocols for cereal field experiments_Nov2012.pdf
Health, safety & hazardous waste disposal considerations