2. Harvesting: Removal of entire plant or economic parts after maturity from the field is
called harvesting. It includes the operation of cutting, picking, plucking or digging
or a combination of these for removing the useful part or economic part from the
plants/crops. The portion of the stem that is left in the field after harvest is called
as stubble. The economic product may be grain, seed, leaf, root or entire plant
Time of harvesting: If the crop is harvested early, the produce contains high moisture
and more immature ill filled and shriveled grains. High moisture leads to pest
attack and reduction in germination percentage and impairs the grain quality. Late
harvesting results in shattering of grains, germination even before harvesting
during rainy season and breakage during processing. Hence, harvesting at correct
time is essential to get good quality grains and higher yield.
Crops can be harvested at physiological maturity or at harvest maturity or at
harvest maturity. Crop is considered to be at physiological maturity when the
translocation of photosynthates is stopped to economic parts. In other words,
physiological maturity refers to a developmental stage after which no further
increase in dry matter occurs in economic part.
In cereals, moisture content of grain is very high during milking stage and it
gradually decreases from 40% to 20% due to accumulation of photosynthates. At
this stage, the translocation of photosynthates is stopped due to formation of
abscission layer between rachis and grain.
Abscission layer: A layer of cells in a plant which contain abundant starch and dense
cytoplasm. Natural separation of the leaf from the rest of plant.
3. Crops Symptoms (external) of maturity
Wheat Complete loss of green color from glumes
Withering of leaf blades
Central spike may be used as an indicator grain
Maize Black layer in placental region of corn kernel
Barley Loss of green color from the glumes or pedunlce
Sorghum Black layer in placental region of grain
Cotton Ball bursting
Red
gram
(pigeon
pea)
Green pods turning brown, after 25 days of flowering
Soybean Greenish yellow leaves and pods
The attainment of physiological maturity can be seen from external symptoms.
4. Harvest maturity generally occurs one week after physiological maturity at which
loss of moisture from plants take place. Yellowing of leaves and drying of pods
or grain are common symptoms of harvest maturity.
Crop should be harvested at physiological maturity when field is to be vacated for
the sowing of next crop, otherwise it is advisable to follow harvest maturity.
Crop Criteria for harvesting
Rice 32 days after flowering
Green grains not more than four to nine per cent
Percentage of milky grains less than one per cent
Moisture content of grains less than 20 per cent
80 per cent panicles straw coloured and grains in lower portion of
panicle in hard dough stage. At least five hills are to be studied at
maturity
Sorghum 40 days after flowering
Grain moisture content less than 28 per cent
Yellow coloured ears with hard grains
Bajra 28 to 35 days after flowering
Compact ears, on pressing hard seeds come out
Moong and
urd
Pods turn brown or black with hard seeds inside pods
5. Crops Criteria for harvesting
Maize Less than 22 to 25 per cent moisture in grain
Husk colour turns pale brown
25 to 30 days after tasseling
Wheat About 15 per cent moisture in grain
Grains in hard dough stage
Yellowing of spikelets
Sugarcane The ratio of brix between top and botton part of cane nearly one
Brix 18 to 20 per cent
Sucrose 15 per cent
Leaves turn yellow
Red gram 35 – 40 days after flowering
80 – 85 per cent of pods turn brown
Groundnut Pods turn dark from light colour.
Dark coloured patches inside the shell.
Kernels red or pink
On pressing the kernels, oil is observed on fingers
Cotton Bolls fully opened
6. Determination of harvesting date is easier for determinate crops
and difficult for indeterminate crops. At a given time, the
indeterminate crop plant 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 immature pods. These problem can be overcome byb any of
the following three methods:
1. Harvesting pods or ear when 75% of them are mature
2. Periodical harvesting or picking of pods
3. Inducing uniform maturity by spraying paraquat or sodium salt.
For deciding harvesting date of fodder crops following additional
aspects are to be considered
1. Toxins present in the crop (generally high at early stage)
2. Nutritive value (generally protein content decreases and fibre
content increases with age)
3. Purpose of harvest (whether for stall feeding or for storage)
7. Threshing: “Threshing” is the operation of separating the grains from the plants. These
operations may be carried out in the field or on the threshing floor, by hand or with
the help of animals or machines. Whatever the system used, it is very important that
threshing be done with care. Otherwise, these operations can cause breakage of the
grains or protective husks, thus reducing the quality of product and subsequent
losses from the action of insects and moulds. Care should also be taken while
transporting the harvested crops from the field to threshing floor to avoid any loss.
Hand Threshing: Hand threshing is generally done in case of pigeonpea. One of the
simplest systems for threshing of pigeonpea crop is to strike the sheaves of crop
spread over threshing floor with a flail or a stick.
Threshing with Animals or Tractors: Subject to the availability of draught animals, large
quantity of crops can be threshed by treading the animals over about 30 cm thick
layer of sheaves(A wheel having a groove in the rim for a rope to work in). This
operation, which is also called “treading out”, can equally well be accomplished with
vehicles.
Threshing with hand driven machines: Normally a hand-operated machine like Olped
thresher, which is basically used for threshing of paddy can also be used for
threshing of cut stocks of pigeonpea. By means of the handle or pedal, a big drum
fitted with metal rings or teeth is made to rotate. The cut-stocks of pigeonpea is
threshed by hand-holding the sheaves and pressing the upper portion of dried plants
against the rotating drum.
Threshing with Motorized threshers: The use of motorized threshers or threshers
operated by tractor power has become very common for threshing of pulse crops.
The threshers available in the market are basically designed for threshing of cereal
crops and no specific thresher is available for threshing of pulse crops
