Harvesting of crops

Harvesting of crops is removal of entire plant or economic portion of plant after maturity from the field. The economic product may be grain, seed, root, lint, latex or entire plant. The portion of stem that is left on the field is known as stubble. Straw comprises the dried stalks or stem and other parts of various crops, from which seed has been threshed in ripe or nearly ripe stage. In maize and sorghum the plant part that remains after separating the ear is referred to as stover.

Time of Harvesting

Time of harvesting has profound influence on yield and quality of the crop produced. A crop should be harvested at proper stage of maturity, i.e. either at physiological maturity or at complete maturity. Crops harvested before physiological maturity or at over maturity are usualy affected adversely. If a crop is harvested early or in pre-mature stage, both yield and quality are reduced. Such crops produce unfilled, underdeveloped, shrivelled grains, low in test weight and starch content. Grains of such crops are high in moisture content and are liable to be infested with pests and diseases. Their germination percentage is also reduced. But over ripening or delayed harvesting results in shattering of grains from pods and ears. They germinate in standing crop even before harvesting during rainy season and break during the processing. Therefore crops should be harvested at correct time to get good-quality grains and higher yield.

Physiological Maturity

Crop is considered to be at physiological maturity when the translocation of photosynthetic is stopped to economic parts. The translocation of carbohydrate to seed is stopped due to formation of abscission layer between rachis and grain. Hence no further increase in dry matter takes place in seed. In most crops after physiological maturity there is reduction in moisture content of grain. The moisture content of grain falls steeply from 40 to 20 per cent. The attainment of physiological maturity can be seen from external symptoms like black- layer formation in sorghum and maize, bleaching of peduncle beneath in pearl millet, turning of green pods to brown or black in pulses etc. Generally, crops should be harvested at physiological maturity when there is need to vacate the field for sowing of next crop.

Maturity

Complete maturity generally occurs 4-7 days after physiological maturity. During this period of 7 days the grain moisture is reduced to a desirable level. The general symptoms of harvest at complete maturity are yellowing of leaves and drying of grains or pods.

Criteria for harvesting of crops

In determinate plants or crops, time of maturity and date of harvesting can be decided easily since all plants mature simultaneously but for indeterminate crops it is slightly difficult. At a given time, on indeterminate plants flowers, immature – and mature pods or fruits can be seen. If harvesting is delayed for allowing the immature pods to mature, the grains from mature pods may shatter. Therefore to avoid such losses in indeterminate crops periodic picking of mature pods should be done.

Harvesting of Fodder Crops

Generally green forage crops should be harvested at flower-initiation stage, – when there is maximum accumulation of dry matter and fodder is soft and – palatable. For multicut crops, stubble = height is important. Fodder grasses – and legumes regenerate well when the stubble is left with at least two nodes above the ground level. The stubble height may be kept at 5-15 cm, depending on internodal length of stem. In forage sorghum a toxin – called Dhurin (HCN) is present in early stage of crop growth, which is poisonous to animals. In later stages its concentration is very much
roller is pulled with the help of a pair of bullocks over the circular path of ears. The repeated rolling separates the seed from the ears. The bullock- operated Olpad thresher is used for threshing wheat, barley, oats, etc. The dried produce is spread in a circular path on the threshing floor and disc of thresher runs over the produce. Repeated movement of thresher helps separate grains from straw
Nowadays several power-operated threshers of different capacities are available. These threshers are provided with a drum, over which pegs or teeth are fixed all around the circumference which rotate with power. Threshing of wheat, barley, paddy, mustard and several other crops can be done easily and rapidly with the help of these threshers. In maize the shellers are available for separating grains from cobs.

Winnowing

Winnowing is done after threshing. It is a process of separating grains from chaff. Generally winnowing is done when wind is blowing, because husk or chaff is lighter than grain, chaff is blown away and grain is separated. Power-operated winnowers are available, with whose help winnowing can be done at any time.

Drying

Moisture content of grain at the time of crops is about 18 to 20 per cent. Moisture for safe storage is 12 per cent for most of the crops. Drying is a process by which moisture content from grain is reduced to a safe limit. Drying is done either by using solar

Storage

Harvesting of crops is seasonal, but consumption of the foodgrains is continuous. The market value of the produce is generally low at harvesting time. There is therefore necessary to store the produce for different periods. The different categories of agricultural produce needing storages are foodgrains, oilseeds, seeds and fodder. Factors affecting storage: Several factors that influence the storage of foodgrains are moisture content, quality of produce, climatic and storage conditions.no od
The most important factor deciding the stability of the produce is moisture content of grains. Higher moisture content of grains results in severe attack of insects and micro-organisms in addition to heating and germination. Grains with high moisture respire at higher rate than dry seeds When the moist seeds are stored, the moisture from upper layers moves downwards, deteriorating the grains in lower layers. Insects obtain water needed for their body from the food material they eat. Moist seeds are suitable for easy biting or chewing by insects. Due to this the grains with high moisture are prone to insect attack than dry seeds. Sometimes moist grains may even germinate and become unfit for consumption. Moisture content for safe storage of grains of most crops is about 14 per cent.
Among the climate factors influencing storage of food-grains, tempera- ture, light and relative humidity are most important. Respiration of grains increases with increase in temperature. Temperature also influences metabolism, growth, development