DANGERS OF INOCULATION BY SOIL TRANSFER
Touching upon the dangers possibly resulting from inoculation by soil transfer a bulletin from the United States Department of Agriculture has this to suggest:
“Satisfactory inoculations have been obtained by transferring soil from old fields on which the legume has been grown, but experience has shown that there are dangers incident to such methods of soil transfer which it is wise to avoid.
“The source of supply of such soil should be definitely known, and in no case should soil be used from fields which have previously borne any crop affected with a fungous disease, a bacterial disease, or with nematodes. Where a rotation of crops is practiced, it is often difficult to make sure of this factor, so that the method of soil transfer is, under average circumstances, open to suspicion, if not to positive objection. Numerous animal and plant parasites live in the soil for years, and are already established in so many localities that it is manifestly unwise to ship soil indiscriminately from one portion of the country to another.
“The bacterial diseases of the tomato, potato, and egg plant, and the club-root, brown rot, and wilt disease of the cabbage, all more or less widely distributed, are readily transmitted in the soil; while in the South and West there are the wilt diseases of cotton, melons, sweet potatoes, cowpeas, and flax, and various nematoid and root-rot diseases which might easily become a serious menace over areas much larger than they now occupy if deliberately spread by the careless use of soil for inoculation purposes. There are several insects and fungous diseases of clover to be avoided, and various diseases of beans and peas. There is also a disease of alfalfa, the ‘leaf spot,’ which is causing damage in some regions. These are only a few of many diseases liable to be transmitted in soils. The farmer should therefore be on his guard. The danger from such sources is by no means imaginary. The Department of Agriculture has had specific cases of such accidental distribution reported, and if the business of selling soil for inoculation is made to flourish by farmers purchasing without question ‘alfalfa soil,’ ‘cowpea soil,’ etc., there is every reason to believe that experience will demonstrate the folly of such haphazard methods.
“Of scarcely less importance is the danger of disseminating noxious weeds and insect pests through this plan of inoculation by means of soils. Even though weeds may not have been serious in the field, the great number of dormant seeds, requiring but a slight change in surroundings to produce germination, is always a menace. The enormous damage to crops caused by introduced insects and weeds should convey a warning and lead to caution. It is not the part of good judgment to view the risk as a slight one.”