Although hemp requires a rich soil, it does not remove from the farm an excess of plant-food material. Nearly all the leaves on the hemp plants, containing much of the plant nutrients removed from the soil, fall off during the growth and maturing of the plant. The remaining leaves may drop off in the field during the process of retting. Further, the plant stems lose about 20 percent in weight of soluble and decomposed materials, which leach out upon the fields, and the stubble may be plowed under. The plant in this manner returns to the land a large part of the plant nutrients that it removes during its growth.
Commercial fertilizers may be used to advantage on soils that are not well supplied with organic matter. Ordinarily, the best fertilizer for hemp is barnyard manure, but commercial fertilizer can be used to advantage to supplement manure. Lime applications may be supplied on acid soils to advantage. Consult your county agent for recommendations as to amounts of fertilizer and lime to apply.
The period of flowering of the hemp plant may extend over several weeks, and as a result the seed does not all mature at one time. Hemp seed for sowing frequently contains some immature green to yellowish-green seeds that may not germinate well. Good hempseed for sowing should be relatively free of such seeds and should germinate 90 percent or better. As the oil content of hempseed usually ranges between 29 and 34 percent, the seed should be kept cool and dry, as it spoils rapidly under warm and damp conditions. Hemp seed seldom retains its germinating power well enough to be used for seed after 2-years' storage.
Hemp should be planted in the spring just before corn. In a program calling for small spring grains and corn, the farmer should plan to plant his hemp between the time he plants his small grains and the corn.
Hemp grown for seed production should be sown in rows or hills. The hills are commonly spaced 5 by 5 feet, with 6 to 10 seeds to the hill, planted not more than 1/2 inch deep. The plants are thinned to 3 to 5 to a hill. If care is taken to save seed, about 11/2 pounds wall sow an acre. Most farmers use more seed, and frequently the crop is replanted because of late floods or failure to obtain good stands.
Hemp grown for fiber should be sown with a broadcast seeder or with a grain drill. A drill with 4 inches between drill tubes is preferred to one with 6 inches or more. The seed should not be planted deeper than 1 inch, and a depth of 1/2 inch is preferred. If the seed is planted deep, the hemp seedling is not capable of pushing its way to the surface of the ground. A slight crust on the ground frequently results in a poor stand. If the seedbed is loose, disks on a seed drill may cut too deep into the soil and the seed will be sown more than 1 inch deep. In such cases, to make certain that the disks do not cut too deep into the seedbed, they should be tied to the seed box.
A standard bushel of hempseed weighs 44 pounds. The rate of seeding hemp for fiber production ranges between 3 and 5 pecks of seed per acre. In Kentucky, where hemp is hand-broken, it has been the practice to sow 3 pecks (33 pounds) per acre. However, when the hemp is to go to the mill, 1 bushel per acre gives a product that is better suited to milling. Wisconsin and other Corn Belt farmers have commonly sown 5 pecks per acre. The lighter rate of seeding in Kentucky produces larger stalks. These stalks are easily broken, and the fiber is easily prepared by the hand-breaking methods that have been used there since colonial days. Machine methods of breaking and scutching to prepare the fiber are used in Wisconsin, and recently to some extent in Kentucky. The machines will handle finer stems, and the sowing of 5 pecks is advisable where hemp is to be prepared by machine.