# Monitoring head and pod density

The number of tiller in cereals establishes the yield potential of the crop for the season. The branching of legumes and canola largely determines the yield potential in these crops. An assessment of head and pod numbers is a useful indicator as to the number of tillers that have survived to form heads and whether or not maximum yield potential of the crop has been maintained.

## Assessing head and pod numbers

1. Count the number of heads (pods) along both sides of a 1 m long ruler or rod placed between two rows of crop at random, at ten sites across the area to be assessed.
2. Calculate the average number of heads (pods) measured at the 10 sites.
3. To convert this figure to heads or pods per square metre use the following equation:

No of heads/m² = av. Head no./metre of row x 100         e.g.      50 heads / m x 100          = 333 heads

Row spacing (cm)                                                        15 cm

### Interpreting head and pod counts

There is a range of recommended optimum flowering head densities available for cereals for a range of different rainfall zones.
Recommended approximate flowering head densities for wheat for different rainfall zones are given below.

Recommended approximate flowering head densities for wheat for different rainfall zones

Annual rainfall (mm) Head density
250 - 350 225
350 - 400 325
400 - 450 400
450 - 500 500

These densities will help to ensure that the opportunities for maximising wheat yields are maintained. Other cereals including barley and oats generally require between 10 – 15 % higher densities than those recommended for wheat.

The percentage reduction in tiller numbers can be established by calculating the differences in measurements between the tiller number measured at nutrition and the flowering head number.

A reduction in number may indicate that seasonal, pest or agronomic conditions reduced the yield potential of the crop. There is always a drop in head numbers between late tillering and flowering no matter how much nutrition is available. It just a fact of crop life.

Rule of thumb: In general, if there has been a mortality rate of 25 % or more, the crop has suffered significant stress. The stress could be nitrogen or water related and should be considered in relation to nitrogen fertiliser, soil water status and weed competition.

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Page last updated: Monday, 12 January 2015 - 1:47pm