Get the answer of: How to harvest groundnut ?
Flowering extends over two months in bunch types and over three months in spreading types. It is, therefore, usual to find pods at different stages of maturity at harvest. Several methods to predict optimum harvesting date are adopted in western countries. Such methods are not common in India.
When good percentage of pods is well developed and is fairly intact with vines, the plant turns yellow and leaf shedding starts. Maturity of pods is determined by inside of the shell turning dark, kernel reaching its normal size and the testa having normal colour of the variety.
Pulling out few plants in the field at random and examining for maturity of pods determine proper harvest stage. When around 75 per cent of pods mature, harvesting has to be commenced.
Besides the above symptoms, the following procedures can be used for determining maturity in groundnut.
Shell out method:
Groundnut pods from several plants are picked and cracked or cut open to determine maturity. The percentage of pods with tan to brown colour inside the hull and pink to dark pink seed coats is worked out. Harvesting is recommended when mature pods range from 60 to 80 per cent, depending on the variety, presence of dormancy and environmental factors.
Seed weight method:
Mean seed weight per plant is determined to estimate maturity at successive intervals. It reaches a constant value when the crop is mature. If two to three plants harvested on 10 November give an average seed weight of 30 g and the other harvested on 11th or 12th November also gives the same weight, then the crop is mature.
Seed/hull ratio (maturity index):
All pods from selected plants for evaluation are removed, washed, towel-dried and opened. Those pods at or beyond maturity stage are characterised by cracks in the white internal pericarp. Such pods are separated into seed and hull. Less mature pods without such cracks are placed with the hulls.
A fresh mass ratio (FMI) is determined by seed mass divided by the hull mass. The grouped kernels and hulls are forced air-dried or dried at room temperature to determine the dry mass ratio (DMI). When FMI or DMI of the two samples is constant, harvesting is recommended. After a variety attains 50 per cent maturity a close monitoring is required to determine the date of harvest.
Harvesting consists of two operations: pulling or lifting the plants (vines) from the soil with pods intact and separation of pods from vines. Manual labor is employed for pulling out the vines, if soil moisture is adequate for easy pulling. If the soil is dry, bullock or tractor drawn blades are used for lifting the vines with pods.
Several methods are followed for shipping the pods from vines. In bunch type, if the vines are still green, the plants are knocked against a cross bar to dislodge the pods. The most common method is stripping pods with hand.
Different types of strippers, both manual and power operated, are available for separating the pods from vines, however, not in large scale use. In the case of runner types, the vines are allowed to dry, then beaten with flails and pods separated from the beaten mass by winnowing.
At the time of harvest, pods usually have moisture content around 40-50 per cent. The pods are to be dried to about 10 per cent moisture content for safe storage. Drying should be done rapidly to prevent fungal molding. Sun drying is the usual method of drying. Summer groundnut should be dried in shade to prevent loss of seed viability, if it is for seed purpose.
Storage:
Farmers usually dispose of groundnut pods within a month from the drying yard itself. A few farmers may store it for about 6 months (till kharif seeding) in anticipation of high price. Pods for seed purpose are stored for 7 to 8 months. Storage at farmers level is invariably in the form of pods. Pods for seed purpose are stored in earthen pots, mud bins or bamboo baskets. Gunny bags are also used for storing the pods.
Aflatoxin production due to Aspergillus flavus takes place just before the postharvest drying when the moisture context of kernel is above the critical level of 9 per cent. Mold growth also takes, place at later stage if kernel moisture content is above critical level.
The period of storage after harvest has performed influence on aflatoxin contamination. There may not be any toxin in groundnut pods stored in drying yard for about a week but the pods left over 15 days contains toxin. The longer the period of storage, greater is the contamination.
Harvest of rainy season groundnut coincides with rains leading to problems in drying the pods. Due to high humidity under such conditions, it is difficult to avoid aflatoxin incidence. Hence, care must be taken to dry the pods at the earliest convenience to minimise the contamination.