A brief guide to estimating crop yields

Accurate, early estimation of grain yield is an important skill. Farmers require accurate yield estimates for a number of reasons:

• crop insurance purposes
• delivery estimates
• planning harvest and storage requirements
• cash-flow budgeting

Extensive personal experience is essential for estimating yield at early stages of growth. As crops near maturity, it becomes easier to estimate yield with greater accuracy.

Estimation method

There are many methods available for farmers and others to estimate yield of various crops. Some are straightforward whereas others are more complicated. The method presented here is one that can be undertaken relatively quickly and easily

Steps are as follows:

1. Select an area that is representative of the paddock. Using some type of measuring rod or tape, measure out an area of 1m² and count the number of heads or pods.
2. Do this 5 times to get an average of the crop (A)
3. Count the number of grains in at least 20 heads or pods and average (B)
4. Using Table 1 determine the grain weight for the crop concerned (C)
5. Yield in t/ha = (A × B × C) / 10,000

For example, to calculate a wheat yield where:

• Average number of heads/pods per m² is 220 (A)
• Average number of grains per head/pod is 24 (B)
• Weight of 100 grains of wheat is 3.4g (per Table 1) (C)

Yield in t/ha = (220 × 24 × 3.4) / 10,000 = 1.79

Accuracy of yield estimates depends upon an adequate number of counts being taken so as to get a representative average of the paddock. The yield estimate determined will only be a guide and assumptions made from the estimates contain a degree of uncertainty.

This type of yield estimation is one of the easiest and quickest to complete and should be able to be used in a number of situations on a grain growing property. Grain losses both before and during harvest can be significant and an allowance for 5 to 10% loss should be included in your final calculations.

Table 1. Grain weights expressed as weight per 100 grains.