PRINCIPLES OF CROP PRODUCTION ABT-320 (3 CREDIT HOURS) LECTURE 09 HARVESTING OF DIFFERENT CROPS FACTORS AFFECTING HARVESTING

HARVESTING FIELD CROPS If the full economic potential of any crop is to be realized, the mature grain must be removed as quickly as possible from the field and placed in safe storage. Extra help may be needed to ensure the highest efficiency of operation. Contractors can be used on larger farms to facilitate harvest within a reasonable time. Despite the disadvantages associated with using an outside header, the saving in potential crop will usually out-weight the added costs, especially if the crop can be rapidly placed into safe storage. Harvesting efficiencies range from 25% to 80%, with an average 60% of the time actually spent harvesting. The remaining 40% of the time is spent either travelling back to field bins, waiting for trucks or empty field bins to arrive, or repairing the header and other harvesting equipment.

HARVESTING FIELD CROPS Winter harvesting normally coincides with the time when thunderstorm activity is high and the potential yield losses through weather and delays could reach 1.5% dry matter per day. A thorough pre-harvest cleaning and preventative maintenance check of all harvest machinery reduces risk of breakdowns. Ensure that essential spare parts, especially drive belts, are on-hand, or readily available. Much time is lost moving, emptying or waiting for trucks. Adequate on-farm storage, trucks and field bins are needed to keep the header harvesting. Field studies suggest that on-farm storage capacity should be about 50% of the total harvest.  Harvest pattern can affect harvest efficiency.

HARVESTING FIELD CROPS Matching the header capacity both to harvest area and crop yield is important. The harvesting capacity of most headers will be determined by the front width. Winter cereal crops are physiologically mature at moisture contents of approximately 35%. Whilst few headers can effectively thresh crops above 20% moisture, most can thresh cereal grain at 17 to 18% moisture. Access to grain drying facilities and aeration equipment enables harvest to start well before a crop dries down to the required 12% moisture level, potentially 10-12 days earlier. It also permits harvesting to start earlier and end later each day. A range of moisture meters are now available for different crops and conditions.

CROP HARVEST With an ever-increasing variety of crops being grown, the correct setting-up of headers is essential. Grain legumes in particular must be harvested and handled very carefully. Even seemingly small losses and grain damage can seriously reduce profits. Obtaining the best quality harvest sample cannot be over-emphasized. A top quality sample will maximize returns to growers by reducing the amount of downgrading and minimizing the grading time needed.

CEREALS Winter cereal crops are reasonably easy to thresh. Harvesting can begin whenever the header is capable of threshing and giving a clean grain sample. Whilst this could mean harvesting at moisture contents greater than 20%, very little grain is harvested above 18% moisture. A moisture test on a grain sample is the commonly used method of assessing harvest maturity. Wheat, barley and oats can be stored or sent to the grain depot at 12%. Mature barley does not stand weather damage as well as wheat. Lodging can be a problem and patches of unripe crop near headlands and low lying wet areas should be avoided as too much green or immature grain can prevent a sample from reaching malting classification.  Care needs to be taken when harvesting malting barley as the importance of apparently minor damage is not always realized. Cracked grains, skinned or partially skinned grains, and grains killed through damage to the germination, do not malt properly. When examining a barley seed sample for damage, look at the individual grains not just the mass of grain. Always examine grains back uppermost, and ignore the crease side.

CEREALS Rye and triticale - Some adjustments to conventional headers may be required to handle the lighter and longer grain. A similar setting to wheat is suitable, with the drum speed slightly reduced. Ripe crops left in the field are likely to shed badly. Mature oats will shatter more readily than barley or wheat, and should be given priority at harvest. Header settings are the same as for wheat and barley.

GRAIN LEGUMES/PULSES As most legumes set their seed pods close to the ground, and the pods have a tendency to shatter easily, care must be taken by the operator to avoid excessive harvest loss, which can be in the order of 10-30%. To minimize losses, consider: Receivable moisture content for most winter pulses has recently been adjusted to 14%. Check before harvest. Harvest the crop with a grain moisture content of 14-15%. Shatter loss is a problem with dry crops. Aeration may be required with higher moisture contents above 14%. Cut as low as practical to gather as many of the pods as possible. Use reduced ground speeds to keep shatter loss to minimum (4 to 5 km/h). Use relatively low cylinder speeds to reduce grain damage, and select relatively high fan speeds to effectively clean the sample.

RYE, OATS, LEGUMES, CHICKPEA

LINSEED, CANOLA, SAFFLOWER

OIL SEEDS Linseed is ready for harvest when the bolls are dry and brittle and crush easily in the hand, and the seed rattles in the bolls when shaken. Late rain can cause secondary growth and flowering, requiring the use of a desiccant to assist harvesting. The crop can be harvested with a comb-front or open-front header, but a lower speed than wheat is recommended. To avoid seed damage, the setting of drum speed and wind-blast is critical. Linseed is a very free-running seed. To avoid seed losses it is advisable to check all harvesting and handling machinery for leaks. Canola is very susceptible to shattering either prior to, or at harvest. Care needs to be taken when setting up the header. On comb front machines, the fingers should be spaced wider. Best separation occurs when pods are slightly moist so consider harvesting at night or during cool cloudy days. A lower fan speed helps reduce losses from the back of the header. Grain moisture content of 8- 9% is desirable for storage, as levels above 10% can cause rapid heating and mould development.

OIL SEEDS Safflower can commence harvest when most of the leaflets around the head become dry and brown and the stem is dry. The crop is easily harvested, but drum speeds must be low enough to avoid cracking and breaking seeds, as oil quality deteriorates in damaged seed. Harvesting at night or early morning will result in a much cleaner sample as the dew makes the dead safflower foliage pliable and less likely to disintegrate. Safflower dust can build up on the header and ignite under hot, dry conditions.

EARLY HARVEST FOR YIELD, QUALITY AND PROFIT Harvesting early at moistures above the receivable limit maximizes quality and yield and minimizes risks of rain damage. Harvesting at higher moisture allows the harvest to start earlier than normal; means more hours of harvesting each day; and earlier resumption of harvesting after rain. Increasing harvest hours per day can be just as effective in speeding up the harvest as using another header, and is much cheaper. However, high moisture grain must be handled and stored carefully. Under hot, moist conditions grain quality deteriorates rapidly, mould problems can develop within days and insect problems in a month or two. The advantages of early harvesting must be balanced against the extra costs of holding the higher moisture grain.

EARLY HARVEST FOR YIELD, QUALITY AND PROFIT Strategies for handling over-moisture grain, starting from the least cost option and progressing to the most expensive option, are: blending with dry grain to meet moisture specifications aeration cooling to prevent mould development until the grain is used or dried aeration drying hot air drying All strategies require sufficient on-farm storage to hold the over-moisture grain.

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