Harvesting

Harvesting the Crop

Overview of Harvesting

• Harvest signifies the completion of the crop production cycle, typically referring to the seed harvest.

• The primary aim of harvest and storage systems is to maximize the harvest yield.

• At the point of physiological maturity, the grain has achieved maximum dry matter accumulation, meaning it reaches peak development and nutritional content.

• The harvest of crops provides commodities that are key for marketing and generating income for farms.

Physiological Maturity and Seed Development

• Physiological maturity marks a stage where the seeds are usually around 90% water content.

• As the seed matures and accumulates nutrients, its moisture content steadily decreases.

• Even after reaching physiological maturity, seeds are not sufficiently dry for storage; significant moisture loss is still essential before they can be stored.

Timing of Harvest for Cereal Crops

• To assess maturity in cereal crops, cut a seed in half and examine the placenta tissue at the endosperm region:   - Not Mature: The tissue appears green, indicating that nutrients, proteins, and starch are still being deposited.   - Mature: The tissue turns brown and becomes non-functional, with typical moisture content ranging from 30-35%.

• Swathing can only occur once seed maturity is confirmed.

• A method to check harvest readiness involves testing kernel hardness; if a fingernail can barely dent the pericarp, the crop is ready for harvest.

• Moisture content standards for harvesting:   - Oats and malt barley: 13.5%   - Wheat: 14.5%   - Feed barley: 14.8%

Timing of Harvest for Brassica Crops

• In Brassica crops, the leaves die before pods, which remain chlorophyll-rich (green).

• Swathing should be based on the maturity of the main stem:   - Wait until 60% of seeds on the main stem have changed from green to either brown or black.   - Seed color changes can progress at a rate of 1-3% each day.

• Pods mature from the bottom upwards; hence the least mature seeds will be located in the top pods.

• Harvesting ideally occurs when seeds exhibit about 40% moisture content.

• Early swathing may result in small seeds and a higher likelihood of having green seeds mixed in.

• Harvest Moisture Content for Canola: About 10% moisture.

Canola Swathing Techniques

• Canola is unique among crops because its quality remains high even if it rains after swathing.

• A light rain (up to half inch) can aid in curing straw and seed, which minimizes the green seed count and supports slower drying.

• Swathing can take place in light to heavy rain to mitigate seed shattering losses, particularly when crops are fully ripe.

• However, swathing should be avoided during very hot weather due to rapid drying which enhances shattering risk.

Harvesting Field Peas

• Often, field peas undergo straight cutting or desiccating because of varied maturity within crops.

• Swathing is occasionally performed, but swathed crops are prone to wind and moisture damage.

• Opt to swath when the crop has turned a yellow-tan color, as seeds will typically possess 20-25% moisture.   - Color Progression:     - Bottom third of the vine: Ripe     - Middle third: Yellow     - Upper third: Turning yellow

• Ripe pods should contain peas that are difficult to dent with a thumbnail yet separate easily under pressure.

Additional Considerations for Field Peas

• Some upper pods may exhibit a lime green shade and have a wrinkled, veined appearance.

• If using desiccants, allow further maturation compared to swathing.

• The lower third of pods should mature, and peas should rattle inside.

• Combining should commence once moisture falls to 18-20% to prevent peeling and splitting.

• Storage moisture should be maintained at 16%; crops are easily split below 14% moisture.

Drying Grain Before Harvest

• Water loss from drying grain occurs through two main processes:   - Whole Plant Transpiration: Loss of water vapor from the whole plant.   - Direct Evaporation: Water evaporating from the grain's surface.

• For effective water loss, moisture must move from the grain through its coverings or husks.

• Increased temperature, airflow, and reduced relative humidity collectively enhance water loss and speed up the drying process of both plants and seeds.

• As seed moisture decreases during drying, the moisture loss rate slows down significantly.

Percent Moisture Content for Various Crops

Table of Moisture Content at Various Maturity Stages

Swathing Procedures

• Swathers are specifically designed to cut crops at predetermined maturity stages and lay them onto stubble, which supports air circulation around them.

• The ideal stubble height is around 1/4 to 1/3 of the original crop height. Taller stubble can cause the swathed crop to settle on the ground while shorter stubble can lead to extensive straw processing, although some farmers choose to bale it for livestock feed.

Swathing Implementation

• Swathing is generally performed under the following conditions:   - Crop maturity is uneven.   - Chemical desiccation is either not desired or unavailable.   - Risk of crop shattering is present.   - There is a heavy green weed infestation.   - Sawfly infestations are noted.

• Swathed crops typically require 7-10 days for drying, depending on the ambient heat and humidity.

• Prolonged periods of damp, cool weather can lead to the growth of mildew or sprouting.

Harvesting a Swathed Crop

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Advantages of Straight Cutting

• One major advantage is the ability to cut higher, thereby reducing the amount of material processed through the combine, leading to a more efficient harvest.

Combining Process

• Combining encompasses multiple operations using a single machine, which include:   - Cutting the crop.   - Gathering the crop.   - Threshing (separating the grain from the plant).   - Cleaning the grain post-threshing.

• The grain is gathered into a hopper within the combine.

• Subsequently, it is mechanically transferred to transport vehicles.

• Grain residue, including straw, leaves, and stover, is expelled from the rear of the combine, with the option to spread or form windrows for baling.

Detailed Mechanics of the Combine

• Crop stalks are laid on a table where a screw-type auger or canvas shifts them towards feeder chains.

• These chains then transport the material to a threshing cylinder where a revolving drum rubs the flowers against a graded concave plate, effectively separating most kernels.

• The grain drops to a grain pan and subsequently onto a louvered sieve, while straw is propelled upward onto an oscillating straw walker to separate any remaining grain.

• Often, straw is chopped upon exiting the combine and spread via spinners as widely as possible.

• The grain is shaken across multiple sieves, utilizing airflow from below to eliminate lighter chaff (such as lemma, palea, and glumes), which is expelled from the rear of the machine, while heavier grains fall through adjustable sieves to move into an auger that directs them to the grain hopper atop the combine.

Drying of Grain for Storage

• Grains are usually marketed based on specific bushel weight and moisture levels, making moisture management crucial for optimal storage.

• Methods to reduce moisture include:   - Field Drying: Cost-effective in energy use but may lead to increased crop losses.   - Artificial Drying: Including aeration techniques and the use of grain dryers. This method incurs higher costs but is especially effective for high-value crops.

Aeration Techniques

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Grain Dryer Methods

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Grain Storage Essentials

• Key goals in grain storage should focus on:   - Maintenance of quality attributes such as color, purity, and odor.   - Preservation of viability for planting purposes.

• Factors affecting storage losses include temperature, moisture levels, and storage duration.

• Fungi represent the most common cause of loss during storage, with insects and rodents also posing significant threats.