Method of harvesting - Harvest and Post Harvest Operations, Crop Production | Crop Production Notes- Agricultural Engineering PDF Download

Harvesting Processes Before harvesting can commence, a number of decisions must be taken and preparations must be made. 

The harvesting process can be divided into sections. If for instance a reasonable percentage of the fruit in a certain orchard will not be fit for export because of external damage, a decision must be taken to pick the fruit that is more likely to be fit for export separately. Note that pickers who are entrusted with pre-selection in the orchard / field must be well trained and closely monitored to ensure that export fruit is not picked by mistake.

Based on the maturity indexing data and the crop estimate, a decision has to be taken on when picking will start, and on the picking period.

A decision can also now be taken on the number of pickers and picking teams that will be required. The necessary workers are recruited and trained, if necessary prior to the harvest.

In preparation for harvesting, a general inspection of the equipment is required to ensure that maintenance has been adequately seen to. Pruning shears, picking bags, ladders, bins or trailers, and tractors are inspected to ensure that they are in the proper working condition. All equipment that may come into contact with fruit must also be cleaned and sterilised to limit waste and decay.

Mechanical harvesters are very expensive and harvesting is often contracted out. It is therefore essential for a farmer to book the harvesters well in advance to prevent yield and quality losses due to too late harvesting. Contractors usually prefer to harvest all the fields in a particular production area before moving on to the next production area and will seldom return to an area in the same season. Therefore the planting time of the crops should also be seen as part of the harvest preparation, because if you plant earlier or later than the other farmers in the area, your crops development will not be in synchronization with the rest of the fields in the area and that can lead problems come harvest time. If a farmer, however, has his/her own harvesters, the latter is not of importance. As with contract harvesting, make sure to enquire and plan for contract labour, transport of the produce to markets, gins, silos etc., if it has to be contracted out.

Harvesting Methods 

* Fruit picking methods

•  Snap picking; and 
•  Clipping

Snap picking is a method whereby fruit is twisted off sharply by hand without using an implement. Clipping makes use of specifically designed pruning shears that are used to cut the stem of the fruit. Clipping is generally recommended in most situations, but there are cases where snap picking, which is faster, is appropriate.

In the case of clipping, purpose-built pruning shears are used to cut the stem as close to the button, or calyx, as possible without injuring the shoulder of the fruit. Long stems of between 1mm and 4mm, which result from inefficient cutting, are a frequent problem in harvesting and can lead to injuries to fruit when they are put into the picking bags, trailers or bins. Injuries of this nature can cause the fruit to decay at a later stage. If fruit is handled roughly or if the shoulders are cut by inexperienced pickers or pickers who are not taking enough time, it also increases the risk of fruit decay.

Snap picking is not recommended for produce such as export citrus fruit for a number of reasons. The calyx buttons are pulled out easily, oleocellosis develops because of the pressure on fruit as it is pulled and twisted, and stems are sometimes not cleanly broken off. It is however appropriate in certain situations, such as when a team is sent in to select and pick non-export fruit.

Snap picking is often done in tomatoes and other vegetable fruit crops, while the use of clipping is often done to improve the quality of the produce less bruising and other physical damage associated with snap picking occurs.

• Harvesting of leafy vegetables
  In most cases the cabbage and lettuce heads are cut from the root at the base of the head and as close as possible to the soil surface, using a knife. Where individual leaves are harvested such as Swiss chard (spinach) or lettuce, the fingers are placed close to the base of the petioles and while firmly keeping hold of the petiole the leaf will be removed from the plant in the same way as the snap pick procedure followed in tree fruit. This may, however, cause tearing of the petiole tissue and knifes could also be used for a cleaner cut.
• Harvesting of grain and seed crops
  If small areas are to be harvested, maize ears can be harvested with the snap picking explained in session 3.1, while pruning shears can be used cut the heads of the sunflower stem. The ears can then be taken to the shed where the ear leaves have to be removed to gain access to the kernels. By simply rubbing the hand palm firmly over the ear, the kernels can be removed. An alternative is to rub two ears together. When soybeans are harvested it would be easier to cut the stem with pruning shears or any other sharp tool close to the soil surface, taking the stems to the shed and manually removing the pods from the stem there. The seeds can be removed by pressing hard on the sides of the pods to force it open.

Guidelines to Harvesting Crops

The section below summarises harvesting guidelines for selected crops.

* Citrus Once picking starts, a few basics guidelines should be adhered to, as set out below.

•  Picking bags are suspended from the side of the pickers and not in front of them. This prevents damage to the fruit as the picker leans against a ladder or pushes into branches in the canopy. 
•  Pickers must walk with full picking bags and not run, as running will bounce and chafe the fruit, leading to the development of oleocellosis. 
•  When picking bags are emptied they should be placed close to or on existing fruit lying in the bulk bins or picking trailers before being emptied. This will also limit injury. 
•  Once a bag has been emptied, it must be opened and shaken to remove loose twigs, leaves and sand that might have collected during the picking process. 
•  Fruit that were dropped during the picking process must not be picked up off the ground and put with export fruit. Similarly, fruit lying on the ground and in contact with the soil should not be picked up and mixed with export fruit.

 When varieties that are susceptible to oleocellosis are harvested, filling of bulk bins and trailers should be limited. The extent of the limitation will depend on the specific condition, but it would generally never be approximately 50% of the volume of the bin/trailer. As an added precaution, rubber or cardboard sheeting can be used to line bins providing protection.

* Soft fruits such as tomatoes Ensure that clear instructions are given on which colour fruits should be harvested and which should be left for the next picking. Follow the site procedures where they are available. Provide examples of some poor quality fruits and what should be done if such fruit are encountered. These fruits bruise easily and should not be thrown into the picking crates from a distance 

* Ears, heads and pods - dry As these are already dry, care should be taken to prevent the seeds from falling out of the head or pod before it reaches the threshing area. At this stage some diseases could have attacked the ears, heads or pods. The pickers should know how to identify these and should separate diseased pods and cobs. 

* Vegetable Crops Vegetables should be harvested during the cool part of the morning and should be stored as soon as possible. If the produce is destined for the market, ensure that the storage conditions are correct for the produce. If they are destined for processing, they should be cooled and stored under refrigeration to preserve flavour and quality. You need to ensure that you know the basic harvest practice for each crop you are dealing with. What follows are some examples of harvest practices for different crops.

• Beans – green - Start harvesting before seeds develop in the pod – when the green pods are about the diameter of a pencil. To determine harvest readiness bend them in the middle, if they snap easily, they can be harvested. 
•  Beetroot - Harvest when they are about 5 to 8 cm in diameter. If the market is for smaller beets they can be harvested at about 2 – 3 cm diameter. The leaves should be about 10 – 15 cm long. The beet tops can also be eaten as greens. 
• Broccoli - Harvest the dark green compact clusters or heads when they are about 15 cm in diameter. The buds must be tight and should be harvested before any yellow flower develops. As you harvest the heads, smaller side shoots will develop providing an almost continuous harvest. 
• Cabbage - Harvest cabbage when the heads feel hard and solid. If left to late the heads will crack and split. Cut the heads from the stem just below the point of attachment to the stem. Ensure that you use a clean, sharp suitable knife. Always clean the knife using a dip mixture of suitable sanitizer in water. One can harvest the sprouts that develop as a later crop. 
• Cucumbers - Harvest when the fruits are deep green and before a yellow colour develops. The cucumber fruit should be 5 – 8 cm long for sweet pickles; 13 – 16 cm for dill pickles, and 16 – 20 cm for slicing pickles. Harvest 4 to 5 times per week to encourage continuous production. Mature cucumbers left on the vine will stop the production of the entire plant. 
• Lettuce - For non-heading types harvest the older, outer leaves from leaf lettuce when they are approximately 12 cm long. For heading types harvest when the heads are moderately firm but well before seed stalks form.
• Onions - Harvest when the tops fall over and begin to turn yellow. Dig out the onions and place them to dry out in the open sun for a few days. The onions are sufficiently dry when skin is toughened. Remove the dried soil by brushing the onions lightly. Cut the stem, leaving 4 to 5 cm and store in a net bag in a cool, dry place.

* Tree crops - general

•  Do not shake the branches of the trees to make the fruits fall down as this will lead to bruising.

• Use ladders where possible.
•  When harvesting for processing, a harvesting stick can be used where fruit are to high to reach but allow the fruits drop onto a soft surface, such as a net.

• When mango and avocados are to be exported or transported for extended periods, leave a portion of the stalk on the fruit. 
•  Do not throw fruits out during harvest. 
•  When harvesting heavy banana bunches use two people per bunch. 
• Harvest in the early morning or late afternoon. 
• Do the first grading according to market destination during harvest.
• Ensure that the latex from mango, banana and paw paw does not come into contact with the skin of the fruit. If this happens wash the fruit in clean water. 
• Take care of your eyes, if harvested fruits contain latex juice. 
• Place your fruits on a well-aerated surface or in containers that are not made of rough surfaces. 
• Handle the fruit as little as possible. 
• Pack the fruits as soon as possible into the final transport box or container. 
• Export fruit may have to be cooled. 
• The basic principals or orchard hygiene are:-

        • In order to avoid mould infections and rind damage a number of standard orchard             hygiene practices could also be implemented.
        • Prune trees of dead branches twigs.
        • Prune the trees to allow light and air movement through trees.
        • Harvest cultivars that are susceptible to splitting early.
        • Never place fallen fruit into bins together with fresh fruit.

The harvesting checklist 

The list provided below is a checklist of items that should be kept in mind before harvest commences.
 Harvesting equipment.
• Maintain ladders, bins, picking bags and crates in good condition.
• Wash and clean all equipment used for picking fruit.
 Harvest and the weather.
• When harvesting during colder conditions the harvest should be during the warmer parts of the day to reduce the risk of skin damage in some fruit.
• During hot conditions wilted fruit should not be picked and the orchard should be, irrigated before harvest.
 Handle fruit with care.
• Wear gloves.
• Have short fingernails.
• Empty bags carefully.
• Do not drop fruit.
• Do not overfill bags or bins.
• Ensure farm road surfaces are smooth.
• Use minimum trailer tyre pressures to cushion the ride.
• Drive slowly to the packing shed. 

 Protect fruit from the sun.
• Keep harvested out of the sun.
• Erect shelters if necessary.
• Transport full bins directly to the packing facility.
• Bulk dip or spray a suitable post-harvest fungicide onto fruit within 24 hours of harvest where appropriate