It is important to harvest groundnuts at the right time. If harvested too early, the seeds will shrink as they dry, which lowers the yield, oil content and quality.
Delays in harvesting will result in poor quality seed due to mould infections and subsequent contamination of the seeds/pods.
Late harvesting also reduces yields because higher proportions of pods are left in the ground due to the pegs being weak which cause the pods to break off.
If harvested late, some non-dormant varieties will begin to sprout in the field resulting in yield losses. Leaves falling off is not a good indicator of harvesting.
It is recommended that a few plants (3-5) should be pulled up and the pods removed and shelled. The insides of the shells should be examined.
If the majority of pods (70% upwards) have dark markings inside the shell and the seeds are plump and the correct colour for that variety, then the groundnuts are mature and ready for harvest.
If the crop is severely defoliated as a result of disease (only one or two leaves per branch) or if sprouting has begun, the crop should be harvested regardless of maturity.
The estimated period of maturity for each variety can be used as a rough guide. Harvesting by hand only is more suitable for the erect groundnut varieties in sandy, loam soils, which are well-drained.
When the soil is wet and heavy or very dry, it is much more difficult to pull up the whole plant without losing the pods.
By using a hoe during harvesting it is possible to lift plants out of heavy or dry soil with a reduced pod loss. Spreading varieties can also be more easily lifted.
Care should be taken not to damage the pods with the hoe as damage makes the pods susceptible to fungal attack. A hoe fork lessens the likelihood of such damage.
It is important to shake the plant after lifting to remove excess soil from the pods, particularly when the soil is wet or heavy.
Soil stuck to the pods will lengthen drying times and reduce the development of unwanted fungal growth.
The correct drying of harvested groundnuts is important because poor drying can induce fungal growth (producing aflatoxin contamination) and reduce seed quality for consumption, marketing and germination for the following season’s planting.
For good storage and germination, the moisture content of the pods should be reduced to between 6% and 8%.
There are different ways of drying the pods, some of which are better than others.
It is particularly important to note that if the pods are exposed to the sun for too long the seed quality can deteriorate considerably and the germination rate can be affected.
If the harvested groundnut plants are left to dry on the soil surface where they have been lifted, the pods are likely to be in contact with the soil, which contains moisture and has a higher temperature.
This can affect the quality of the seed, particularly if there is rain during the drying period. If field drying is used, it is better to use windrows, where plants are laid in rows to catch the wind and dry more quickly.
The drying of pods in windrows should produce the required level of moisture before the pods are picked or stripped. Excessive exposure to the sun can affect the quality of the seed.
The plants can be picked/plucked from the windrows and then laid out in a thin layer in the sun on dry ground, matting or other dry surfaces for a further two to five days, which would normally dry the pods to the required moisture content for storing.
Pods should be covered or taken indoors during the wet weather. They can also be picked immediately after lifting and then dried in the sun for six to eight days. Excessive exposure to the sun can affect the quality of the seed.
Ideally pods should be dried with plenty of air circulation and in the shade.