IT IS NOT easy to harvest the seeds of grasses and legumes. Many methods and special machines are needed, and they get only a part of the seed.

Several factors are involved—variations in the size, weight, and maturity of the seeds; plant types; the height and spacing of the plants; the growing season; and time of harvest.

Some examples: Velvet bentgrass has 10,800,000 seeds to a pound; field peas have only 1,800. Subterranean clover may bury its seed in the topsoil; sudangrass will grow to 8 feet tall. Vetch seed is large and dense; the Arizona cottontop has a light, fluffy seed, covered with short, white hairs.

The seeds of some species ripen evenly; the slender gramagrass has seed in all stages from the bloom to maturity, from June until frost.

Some seed plants are grown in solid stands. Others may be sparsely spaced in rows. Some kinds have a single stem; others grow in a clump.

A survey by research engineers in the Department of Agriculture disclosed that a farmer might be harvesting less than one-half of the seeds he produced—33 percent of the crimson clover crop as pure live seed; 23 percent of the subterranean clover; 65 percent of the Alta fescue; 53 percent of the hairy vetch; 46 percent of the alfalfa; 25 percent of birdsfoot trefoil; and 40 percent of the Ladino clover.

To combat such heavy losses of seed, improved machines and methods are being developed continually. Some of them we consider here.

THE COMBINE, developed to harvest cereal grain crops, has been modified to handle small seeds and is the chief machine used in harvesting crops of grass and legume seed. All the different types of combines have been used, tractor drawn and self-propelled, with cutting mechanisms 6 to 18 feet wide. Small harvesting machines save more seed than the larger ones.

Modifications of the combine include a speed control for the cleaning air fan; baffles for air distribution; rubber-covered angle bars in place of a spike-tooth or rasp bar cylinder and concave; special sieves for the combine cleaning shoe; a variable speed control for the threshing cylinder; a sheet metal pan under the chaffer tailing extension; and check curtains behind the threshing cylinder.

The weather, the stage of seed maturity, and the kind of seed crop determine the alterations necessary.

Rubber-covered angle bar cylinder and concave often are used to thresh crimson clover seed, which is hard to remove from the pod yet damages easily.

The size and shape of the openings of the special sieves on the combine cleaning shoe accommodate a particular seed. For example, a 24 by 24 wire mesh screen is recommended for red-top seed. The adjustable sieve can be regulated to accommodate many seed sizes. To handle dallisgrass, the sieve is set one-half open and the cleaning air is shut off. With the variable cylinder speed control, the cylinder speed can be increased to handle seed, like crimson clover, that is hard to thresh. It can be reduced to handle seed that is easy to thresh.

The metal pan under the tailing extension keeps seeds, stems, and leaves from falling into the return elevator and being rethreshed. Check curtains back of the cylinder deflect the discharging material down to the rack so that the seed can be shaken out of the straw and on to the shoe for cleaning.

Rubber rolls may be mounted ahead of the threshing cylinder for crushing seed pods in crops like alfalfa and flax. For threshing alfalfa, the cylinder speed can be reduced as much as 1,000 revolutions per minute; there is less damage to seed, and the percentage of unthreshed seed is no higher.

Four-way automatic leveling devices are used in hillside combining to keep the threshing and cleaning mechanism level while operating on the side of a hill. Without the leveling, the material would crowd to the low side of the cylinder, rack, and the cleaning shoe, thereby causing cylinder chokage, inefficient separation of the seeds from the straw, a slow forward speed, and greater loss and damage of seeds.

A vertical sickle at the end of the cutterbar cuts the tangled crop and separates the cut and uncut standing crop, so that there is less chokage and seed shatter in crops like vetch. The rotary screen cleaner, mounted in the discharge of the combine grain bin auger, screens out dirt and small seeds of weeds before the seeds go into the sacker.

Lift fingers on the cutterbar raise a low-growing crop or a down crop above the sickle so it can be cut. A vacuum attachment under the combine can be used to reclaim shattered seed from the ground.

Special cutterbars, like the lespedeza bar, have more and smaller ledger plate guards and cut the crop near the ground. The double sicklebar has no guards, and both the top and bottom sickles reciprocate to cut heavier and greener crops without chokage.

Special reels can be used, like the tined reel, which lifts down crops, or the wind reel, which blows the crop into the cutterbar, instead of the revolving reel, which causes shattering.

Special gears reduce the forward speed of the combine without lowering the speed of the threshing and cutting mechanism. The possibility of cylinder chokage and overloading the rack and shoe is less.

AS THE CROP gets drier, the seeds shatter more easily, but the setting of the concave clearance can be wider and the threshing cylinder can be operated at slower speed.

When the moisture is high, the cylinder speed is increased and the clearance is lowered to thresh the seed.

In direct combining, the standing crop is cut and immediately run through the combine to free the seed from their pods and separate them from the straw. When crop conditions, maturity of seed, and weather permit, direct combining is desirable. It requires less labor and equipment.

In windrow combining, the crop is cut and gathered into swaths or windrows to field cure. A pickup attachment on the combine lifts the cured crop from the windrow and feeds it into the combine, which threshes and separates the seed from stems and leaves. Windrow combining is used usually on crops whose seeds shatter before the plant and seeds are dry enough to combine and store.

TO ANALYZE the operation of a combine, we recommend several steps:

Adjust the threshing cylinder speed and clearance to the crop that is being harvested.

Regulate the forward speed of the machine so that the crop will not overload the threshing cylinder, rack, and shoe.

Make a test run and analyze the operation by considering the combine in four sections—feeding, threshing, separating, and cleaning—and observe the operation of each part.

The feeding section consists of reel, divider, cutterbar, and feeding mechanism. The reel should hold the crop upright, while the sickle makes the cut, and then lay the straw gently on the draper. The reel speed should be 10 percent faster than the forward movement of the machine. The reel height should be adjusted so the slats contact the straw just below the seed heads. The cutterbar knives and ledger plates should be sharp and in register.

The threshing section consists of a threshing cylinder and concaves. The discharging of unthreshed heads over the rack is caused by a low cylinder speed or excessive concave-cylinder clearance. Broken seeds are due to too high a cylinder speed, too little concave-cylinder clearance, or the return of threshed seed to the cylinder by the tailing return auger.

In setting the threshing cylinder, adjust the cylinder-concave clearance to one and one-half times the thickness of long seed or one and one-half times the diameter of round seed.

If excessive straw breakage is observed, increase the concave-cylinder clearance.

Adjust the cylinder speed so the seed is rubbed or knocked out of the seed pods or heads. Then gradually reduce the speed until some of the heads are unthreshed.

At this point, slowly raise the cylinder speed until only an occasional unthreshed seed head is found. Most of the occasional unthreshed seed is immature or partly filled seed.

The separating section consists of the beater cylinder, check curtains, and straw rack. Threshed seed in the straw discharge is due to overloading the rack, too slow a speed, or a worn check curtain.

Slow down the forward speed of the combine to prevent overloading.

Increase the rack speed to shake seed out of straw and renew the check curtain if the cylinder is throwing the seed over the rack.

The cleaning section has the fan, grain return, chaffer sieve, chaffer extension, and shoe sieve.

Excessive air blows seed over the chaffer sieve and out the back of the combine. Too large a volume of material also prevents seed from coming in contact with the sieve and dropping into the seed pan.

Adjust the cleaning air so the material is slowly agitated over the chaffer sieve. Precise air adjustment is required on light grass seed. For some grasses, the fan discharge is completely closed. The shoe sieve opening should be as large as possible without getting excessive straw and trash in the clean grain.

On grasses that are easy to thresh, the concave-cylinder clearance is widened to reduce the straw breakage, and the chaffer extension is blanked off by placing a piece of sheet metal under the bars to prevent material from being returned to the cylinder for rethreshing and possible damage.

IF A CONVENTIONAL grain binder is used to cut and bundle the seed crop, the bundles are shocked and left in the field to cure. The bundles are then threshed in a stationary thresher or a combine.

In dew areas, cutting and binding are done usually in early morning, while the humidity is high. After a curing period, the bundles are threshed in the afternoon when the sun has lowered the humidity.

To reduce seed losses, the binder often is altered by removing every other reel slat and installing catch pans under the binder deck and beneath cracks between the canvas and elevator to catch the shattered seed. Since the binding-shocking-threshing method involves a number of operations and takes more work and equipment, it is being abandoned, even though it may save more seeds than other methods.

IN SEED STRIPPING, the ripe seed is removed and the plant is left growing. A number of native grasses in the Great Plains, which cannot be harvested satisfactorily by any of the conventional methods, are stripped. Many kinds of shop-made strippers are in use.

Even under the best operating conditions, seed stripping is an inefficient way of harvesting seed; the stripped seed must be cured or dried before cleaning and storing.

A widely used machine is the bluegrass stripper, which removes the ripe seed with a ground-driven, spike-tooth cylinder so mounted that the revolving cylinder rakes off the mature seeds and discharges them into a seed hopper as the machine is pulled through the field.

The hopper lid is opened periodically, and the stripped seed is removed for curing and processing. Sometimes several bluegrass strippers are drawn by one tractor.

The pneumatic-type stripper in general use is a tractor-mounted machine in which an airblast directed at the seed heads blows the seed into a receiving head equipped with a rotating spiked drum and a scrubbing screen. The air current from the nozzle and the revolving drum convey the light seed through the air duct and into a burlap bag.

HEADERS are machines that clip the plants just under the seed heads and gather the material in a catch pan. The seeds are cured in piles and later are threshed.

Combines equipped with a wheel-mounted trailer box are used in harvesting some of the native grasses, like the bluestems, in the Great Plains. The heads are threshed by the combine. The tailings are caught in the trailer box, dumped in piles, and left to cure. The straw is then rethreshed to recover a large proportion of the seed that would have been left in the field.

COMMON METHODS OF HARVESTING GRASS, LEGUME, AND SEED CROPS
Crop name (common)	Binder	Windrow	Direct	Stripper	Remarks
Alfalfa (West and North Central States).	x	x	x		Windrowing is the most common practice.
Bentgrass		x	x		Weather conditions permitting, direct combining yield better.
Bermudagrass		x	x
Bluegrass, Kentucky				x	Small areas are often hand stripped.
Bluegrass, Merion	x	x
Bluestem, big and sand	x		x		Seed from combine should be cured several days before being sacked.
Bluestem, cane-				x
Bluestem, King Ranch			x	x
Bluestem, little			x	x
Bristlegrass, plains			x	x
Bromegrass, field			x		It is necessary to deawn seed to facilitate cleaning.
Bromegrass, smooth	x		x		Direct combine, unless crop badly lodged.
Buffalograss		x	x		Requires special beater mounted in place of sickle for direct combine.
Canarygrass, reed	x	x	x		When direct combined, the seed must be dried immediately.
Cenchrus, big*
Clover, crimson		x	x		Sometimes double threshed.
Clover, Ladino		x	x
Clover, red		x
Clover, sub		x
Cottontop, Arizona*
Cowpea		x	x
Dallisgrass		x	x		Direct combining starts when a few spikelets have shattered and most are brown.
Fescue, chewings		x	x		To direct combine, harvest when seed are in the hard-dough stage.
Fescue, tall	x	x	x		Check for seed heating when direct combining.
Grama, blue			x	x	Combine in hard-dough stage. Windrow before full maturity.
Grama, sideoats			x	x
Hardinggrass	x
Indiangrass	x		x
Lespedeza, annual		x			Some farmers mow and stack the hay for threshing at a later time.
Lovegrass, sand			x
Lovegrass, weeping	x		x		Make two runs with stripper.
Lupine		x	x		Windrowing should be done while seed are in medium-to hard-dough stage.
Meadow foxtail	x		x		Harvest as soon as seed will thresh; dry immediately.
Oatgrass, tall	x		x
Orchardgrass	x		x		Combine within a 3-day period following seed ripening or seed will be lost by shattering.
Peas, field		x
Redtop	x	x	x		When combine harvested, cure immediately.
Ryegrass	x	x	x		To direct combine, the field should be uniformly ripe, free from green weeds.
Soybean			x
Sprangletop, green			x
Sudangrass	x		x		Usually seed do not ripen uniformly for combining; most of the seed crop is cut with a binder.
Sweetclover		x	x		Seed obtained in combining direct must be dried before hulling and cleaning.
Switchgrass	x		x		Combined seed should be dried to prevent heating.
Timothy	x		x		Binders used little in large timothy producing areas.
Trefoil, birdsfoot		x			After first seed sets begin shattering, cut when humidity is high or morning dew is on the plants.
Vetch, hairy		x	x		Seed saved in windrow-combining justifies extra operation. In direct combining, fill sack only two-thirds full; let dry in field.
Wheatgrass, crested	x	x	x		Harvest should begin at stiff-dough stage to reduce shattering.
Wheatgrass, western		x	x	x	Combined and stripped seeds should be allowed to cure before sacking.
Wheatgrass, slender	x		x		Heavy shatter losses occur when direct combining.
Wildrye, Canada	x		x		To combine, use only partial width of cut.
*Forage harvester can be used.

THE FORAGE harvester that is used to harvest green forage often is used to harvest subterranean clover and the light seed of several of the Great Plains grasses. The practice is to let the seed mature and use the unit to chop the forage and blow it into trailing wagons. The finely chopped material of the native grasses is cured and planted. For subterranean clover, the chopper is run as close to the ground as possible to pick up free seed burs. The harvested material is then threshed with a combine.

The chopper is used to harvest Arizona cottontop, needlegrasses, feather bluestems, and Texas bluegrass. The seeds and chopped forage can then be planted with a picker wheel-type cotton planter. Harvesting big cenchrus with the chopper reduces the time required to hammermill the seed burs to remove spines. This procedure is necessary before the burs can be planted.

The suction seed reclaimer is used as another combine attachment. It sucks shattered seeds from the ground during the harvesting operation and feeds them to the combine for threshing along with the incoming crop. The reclaimer recovered an average of 68 percent of the shattered seed in harvesting crimson clover. Eighty-nine percent of the seed was recovered in subterranean clover. The machine reclaimed only 11 percent of the shattered seed in birdsfoot trefoil, where the small, round, dense, naked seeds were beneath the stubble.

Tractor-drawn or self-propelled windrowing machines are 8 to 16 feet wide. They consist of a cutterbar and a draper conveyor that delivers the straw to the center or to one end.

Another type is the tined windrower, which consists of a series of metal tines—each one progressively longer—fastened to the back of the mower cutterbar so that the material being cut rolls into a continuous roll as the mower moves through the field.

The wheel windrower consists of two tined wheels mounted behind the mower cutterbar so that they come in contact with the ground and slowly rotate and gently fold the outer edges of the cut material toward the center to form a swath.

The width of material cut and put into the windrow should be about the same as the width of normal cut of the combine that is to be used to thresh the seed. Swathing the straw for the seed to cure is a method used to harvest seed crops such as bentgrass, alfalfa, bermudagrass, Merion bluegrass, buffalograss, and many others.

CHEMICAL SPRAYS may be used to hasten the curing of standing seed crops. They make it easier to combine a crop before the seeds shatter excessively.

Chemical curing has been effective in reducing cost and losses in the harvesting of seed in sunshine areas where the temperature is moderate to high. The chemicals give uncertain results in areas where cool nights, heavy dews, fogs, and cloudy days occur. For example, in the Willamette Valley of Oregon, a treatment may be worthless one time; the next time the chemical will dehydrate the leaves, seed pods, and stems enough so that the standing crop can be combined without damaging the seed or the roots. In California, where the temperature is higher and the humidity is lower, nearly all the alsike clover is chemically cured and direct combined with the aid of chemical sprays. The practice is used on Ladino clover, alfalfa, red clover, birdsfoot trefoil, sudangrass, Alta fescue, and orchardgrass.

The advantages are many where chemical dehydration and direct combining can be practiced. It saves the labor and equipment required to windrow a crop. The loss of seed caused by cutting, windrowing, and the pickup operations are saved by direct combine harvesting.

The rapid development of new agricultural chemicals has led to the appearance of many unproved desiccants on the market. To prevent the possibility of poor seed production, one should use only the chemicals that have been tested and recommended by agricultural experiment station specialists or county agents.

TIMING the harvest is important.

Tests in the Willamette Valley have shown that a day's delay in harvesting may result in severe loss of seed due to shatter. As an extreme example, yields of birdsfoot trefoil were found to be reduced about 25 percent over a 4-hour period of hot, sunny weather after several days of cool weather.

A 3-year study was made at the Oregon Agricultural Experiment Station of the effect of mowing time on the amount of pure, live seed collected in the combine grain bin. It showed that proper timing could increase by 75 percent the seed saved of crimson clover, 36 percent of Alta fescue, and 60 percent of subterranean clover.

Early harvest does not work on all seed crops, however. In the same test, the take of pure live seed of birdsfoot trefoil was reduced substantially by early harvest. The first seed set was beginning to shatter before the germination of harvested seed was high enough to meet the requirements of State and interstate seed laws.

Enough nutrients were left in the windrowed straw of crimson clover for the seed to finish maturing. The result was the largest amount of seed, the highest germination, and the lowest percentage of damaged and shriveled seeds.

Records were kept of the appearance of the stems, the leaves, the floret, the seed, and the moisture content of the seed. Color pictures were used as guides to pinpoint the time to harvest a crop for maximum yields. Only the seed moisture at the time of cutting was a true indication of the time to windrow the crop each year.

Results of research studies indicate that a seed is at its peak in quality at maturity and that it should be harvested immediately in order to get the highest percentage of quality seed. Seeds start deteriorating immediately upon reaching maturity, and all man can do is to retard the change by regulating the time and method of harvest and treatment after harvest.