The major symptoms of physiological maturity of some field crops are as follows:
• Wheat and Barely– Complete loss of green colour from the glumes.
• Maize and Sorghum– Black layer in the placental region of grain
• Pearl millet– Appearance of bleached peduncle
• Soybean– Loss of the green colour from leaves.
• Redgram– Green pods turning brown about 25 days after flowering.
Harvest Maturity Symptoms
The harvest maturity symptoms of some important crops are as follows:
• Rice– Hard and yellow coloured grains.
• Wheat– Yellowing of spikelets.
• Sorghum, Pearl millet, foxtail millet– Yellow coloured ears with hard grains.
• Ragi– Brown coloured ears with hard grains
• Pulses– Brown coloured pods with hard seeds inside the pods.
• Groundnut– Inner side of the pods turn dark from light color.
• Sugarcane– Leaves turn yellow.
• Tobacco– leaves slightly turn yellow in colour and specks appear on the leaves.
Criteria for Harvesting of Crops
The criteria for harvesting of crops is given
|Crop||Criteria for harvesting|
|Rice –||32 days after flowering, Green grains not more than 4-9%|
|Wheat-||About 15% moisture in grain, Grain in hard dough stage.|
|Maize-||25–30 days after tasselling, Seed moisture content is at 34%|
|Sorghum-||40 days after flowering|
|Cumbu-||28–35 days after flowerin|
|Redgram-||35–40 days after flowering|
|Black/Green gram-||Pod turn brown/black|
|Rapeseed/mustard-||75% of the silique turn yellow, Seed moisture at 30%|
|Sunflower-||Back of heads turns to lemon yellow|
|Groundnut-||Yellowing of leaves and shedding Development of purple colour of the testa|
|Cotton-||Bolls fully opened|
|Jute-||50% pod stage (120–150 days)|
|Sugarcane-||Brix 18–20%, Sucrose 15%|
Determination of harvesting date is easier for determinate crops and difficult for indeterminate crops because at a given time, the indeterminate plants contain flowers, immature and mature pods or fruits. If the harvesting is delayed for the sake of immature pods, mature pods may shatter, if harvested earlier, yield is less due to several immature pods. This problem can be overcome by,
• harvesting pods or ears when 75% of them are mature (or)
• periodical harvesting or picking of pods
• inducing uniform maturity by spraying Paraquat or 2, 4-D sodium salt.
In fodder crops, toxins present in the crop, nutritive value, purpose of harvest (whether for stall feeding or for storage) and single or multi cut are also to be considered during harvest. Example–HCN toxin content in sorghum is high up to 30–45 DAS.
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