Harvesting refers to the removal of the entire plant or its economic parts from the field after maturity, through operations like cutting, picking, plucking, or digging. The remaining stem part after harvest is called stubble. The economic product may include grain, seed, leaf, root, or the entire plant.
Harvest Index (H.I):
H.I = (Economic yield / Biological yield) × 100
This index is the ratio of economic yield to total biological yield, expressed as a percentage.
Time of Harvesting:
Early Harvesting: Leads to high moisture content, immature grains, pest attacks, reduced germination, and impaired grain quality.
Late Harvesting: Results in grain shattering, premature germination during the rainy season, and breakage during processing.
External Symptoms of Physiological Maturity:
- Wheat and Barley: Complete loss of green color from glumes.
- Maize and Sorghum: Formation of a black layer in the grain's placental region.
- Pearl Millet: Bleached peduncle appearance.
- Soybean: Loss of green color from leaves.
- Redgram: Green pods turn brown about 25 days after flowering.
Harvest Maturity Symptoms:
- Rice: Hard and yellow-colored grains.
- Wheat: Yellowing of spikelets.
- Sorghum, Pearl Millet, Foxtail Millet: Yellow ears with hard grains.
- Ragi: Brown ears with hard grains.
- Pulses: Brown pods with hard seeds.
- Groundnut: Pods turn dark on the inner side.
- Sugarcane: Yellowing of leaves.
- Tobacco: Leaves slightly yellow with specks appearing.
The criteria for harvesting of crops are given in the table below:
| Crop | Criteria for Harvesting of Crops |
|---|---|
| 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 flowering |
| Redgram | 35–40 days after flowering |
| Black/Green gram | Pod turns 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 color of the testa |
| Cotton | Bolls fully opened |
| Jute | 50% pod stage (120–150 days) |
| Sugarcane | Brix 18–20%, Sucrose 15% |
Determining the harvesting date is straightforward for determinate crops but challenging for indeterminate crops, as they simultaneously have flowers, immature, and mature pods or fruits. Delaying harvest to accommodate immature pods can lead to mature pods shattering, while early harvesting reduces yield due to immature pods. To address this, harvest when 75% of pods are mature, harvest periodically, or apply chemicals like Paraquat or 2,4-D sodium salt to induce uniform maturity.
When harvesting fodder crops, consider factors like toxin levels, nutritive value, purpose (e.g., for stall feeding or storage), and whether the crop is intended for single or multiple cuts. For instance, sorghum has high HCN toxin content up to 30–45 days after sowing (DAS).
- Manual Harvesting: The primary tool for manual harvesting is the sickle, which should be sharp, curved, and serrated for efficiency. Knives are used for crops with thick, woody stems. Modern sickles reduce labor drudgery.
- Mechanical Harvesting: This involves using implements or machines to harvest crops.