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30
GRAANGIDS
2016
GRAIN GUIDE
4. Dry beans and soybeans
Follow the steps below to do a crop estimate for dry beans and soybeans:
4.1 Determine the number of plants per 10 m and the average row width.
Plants/10 m ÷ row width x 1 000 = plants/ha
4.2 Determine the average number of pods per plant and seeds per pod.
Soybeans: ± 1,8 seeds/pod: Mass: ± 0,16 g/seed
Dry beans: Seeds/pod and mass/seed vary according to cultivar:
Small white canning types: Mass: ± 0,19 g/seed
Red speckled types: Mass: ± 0,47 g/seed
4.3 Allocate a mass per plant using the above guidelines, but always keep the following in mind:
– Evenness of plant establishment and plant height.
– General appearance and colour of the plants.
– Moisture conditions (drought or waterlogged).
– Weed, insect and disease control.
4.4 Plant establishment guidelines:
4.5 Now calculate the yield with the following formula:
Plants/10 m ÷ row width x mass/plant (g/plant) ÷ 1 000 = t/ha
4.6 Make provision for losses during the harvesting process as follows:
– Adjust the calculated yield for dry beans by a factor of 80%.
– Adjust the calculated yield for soybeans by a factor of 85%.
– Also remember to take the height of the harvester blade into account for soybeans.
Dry beans:
Large seed types
Small seed types
Eastern areas:
± 120 000
150 000 +
Central areas:
± 100 000
± 140 000 - 150 000
Western areas:
± 80 000 - 100 000
± 120 000 - 140 000
Soybeans:
Eastern areas:
± 300 000 - 400 000
Central areas:
± 280 000 - 300 000
Western areas:
± 280 000 - 300 000
= t/ha
Number of heads per 10 m
1 000
Grams per head
Row width
x
3.2.5 Multiply the number of seeds per square centimetre (cm
2
) by the productive area to get
the number of seeds per head.
3.2.6 Multiply the number of seeds on the head with the average mass per seed to obtain the
mass of the head. Use a mass of 0,04 g/seed as guideline.
3.3
Count the number of heads per 10 m.
3.4 Measure the row width.
3.5 Use the following formula to calculate the yield:
5. Grain sorghum
Guidelines for grain sorghum: In the first place you work only on the plant population where
plants are still young and there are therefore no ears with kernels that can be used for the
yield estimate.
Do your own crop estimate
Continued from p. 26