The equipment can be washed with water when compressed air is not available. Attention must be given to the lubrication of bearings immediately after washing.

The seedgrower should always have a copy of the operator's manual for his make and model of combine or stationary thresher. His machinery dealer should be able to supply it. The operator must understand the operation and adjustment of the machine if he expects to harvest the maximum amount of high-quality seed.

The germinating quality of harvested seed is closely related to the amount of cracked, broken, and internally damaged seed. Cylinder speed is normally the main cause of this type of damage. The use of grain blowers to handle the harvested seed also is a factor.

THE ACCOMPANYING table lists a range of cylinder speeds and concave adjustments that will give adequate threshing without excessive damage to the seed.

The peripheral speed of the cylinder depends on the cylinder diameter and cylinder shaft speed. The larger the cylinder, the slower the shaft needs to turn for a given peripheral speed.

When the cylinder speed is given in feet per minute, the required cylinder r.p.m. (revolutions per minute) can be computed by dividing the cylinder peripheral speed by the product of 3.14 times the cylinder diameter in feet.

THE GERMINATING quality of the harvested seed can also be seriously reduced by grain blowers. That is a result of the same type of damage that is caused by excessive cylinder speed. The impeller shaft speed of the grain blower should be checked and adjusted, if necessary, to the speed recommended by the manufacturer for the particular application.

Feeding the grain blower at considerably lower than the rated handling rates can also result in damage to the grain even when the blower is operated at the proper speed.

The speed of the cylinder and the clearance between the cylinder and concave bars (or the number of rows of teeth in the concave and the overlap between cylinder and concave teeth) should be such that an occasional seed remains in the head and there is little cracked grain in the seed when it is harvested.

The open, bar-type, concave grate should be open to allow maximum separation of seed from the straw at the concave except when harvesting a seed crop that is difficult to thresh and the straw breaks up badly. Then part or all of the grate should be closed to reduce the amount of chaff going over the shoe as well as increase the threshing action of the cylinder.

INCREASING the cylinder speed or overlap between the cylinder and concave teeth, reducing the clearance between bar-type cylinders and concaves, or increasing the number of teeth in the concave will all increase the amount of threshing.

An increase in cylinder speed, however, will increase rapidly the amount of damaged seed, even if there is adequate clearance for the seeds in the cylinder.

Increasing the number of teeth in the concave or reducing the cylinder concave clearance generally will not noticeably increase the amount of seed damage until the minimum clearance is about the same as the largest dimension of the seed.

Spike-tooth cylinder teeth should be centered on the concave teeth, and worn cylinder bars or bent concaves should be replaced, so that a uniform clearance is maintained between the cylinder and concave bars.

Better bearding of varieties that have suffered from hot weather or lack of moisture during the seed-forming period can be accomplished by reducing the clean grain sieve opening and thereby returning a high percentage of the seed to the cylinder for re-threshing.

THE COST and time spent in growing and harvesting a seed crop make it quite expensive. It would be foolish to ruin it by using poor equipment to unload it into granaries.

A wind elevator operated with too much pressure can cause enough mechanical injury to make the crop worthless for seed purposes. Damage also may result if auger equipment is run at excessive speeds. The operation of such equipment should be thoroughly checked. A trial run should be made before they are used.

HARLAND STEVENS, an agronomist engaged in cereal research, Cereal Crops Research Branch, Agricultural Research Service, has been stationed at the Branch Experiment Station, Aberdeen, Idaho, since 1931.

JOHN R. Goss is an agricultural engineer in the Agricultural Engineering Department, University of California, Davis.