” Tillage burns out the humus and calls for a new supply. It lets the air in, like opening the drafts of a stove. The higher the state of cultivation,” writes Prof. G. F. Warren of the College of Agri-culture of Cornell University, “the more humus needed. We must supply this either in barnyard manure or by cover crops. Manure is expensive, cover crops are relatively cheap and may be made to furnish the nitrogen and humus at the same time.
” We pay 15 to 20 cents a pound for nitrogen when we get it in a fertilizer bag, but we can get along very well without applying any if we plow under clover. Occasionally the orchard may need humus without additional nitrogen; then we may use rye, wheat, oats, buckwheat, or let the summer grass and other weeds grow as a cover crop. Such a condition does not often arise in practice, for few soils are troubled with too much nitrogen.
“A common mistake is in letting cover crops grow too late in the spring. We sometimes forget that we are raising fruit, not glover. The time to plow is when it will do the fruit the most good; generally this is before the clover has made much growth in the spring. But we do not accomplish all that we expect when we leave the clover so long. Before it blossoms it has in it about all the plant food that it is going to take up. But no matter how small the clover is, the ground should he plowed at the time the trees need tillage.
” Perhaps the following is as near to a general rule as can be given. It agrees closely with the present practice of many of our best growers. Plow the land deep before planting; raise corn or other tilled crops for two or three years, plowing as deep as possible without injuring the roots. Each Year a larger space should be left so that corn will not interfere with the trees. Crimson clover may be sown in the corn at the last cultivation and be plowed under early in the spring before it has made much growth.
” After the second or third year the land should be given over entirely to the orchard. It should be plowed early, before the weeds or clover have grown very much, plowing shallower than in the first years. Continue tillage with a cutaway or a spring-tooth harrow until the middle of July or August 1, then sow 15 to go pounds of crimson clover seed to the acre, or the summer grass and weeds may he allowed to grow. It is not always necessary to sow clover every year. If the trees are tilled too late in the season, there is danger that they will make too much growth in the fall and be more likely to winterkill. On some of the sandy soils it is not necessary to plow every year.
Some years the soil may be worked up with a cut-away or disk harrow.”