least six inches deep. Our experience has shown that quack grass roots do not penetrate through the soil much beyond a depth of four or five inches, very few going beyond six inches. The following season sow with grain. After the grain is removed plow the land and harrow in such a way as to get all the roots on the surface, and repeat the disking and harrowing as often as the grass occurs, once a week if necessary.

The Cover Method.-Covering with tarred paper, manure, or straw is effective when well done. When tarred paper is used the edges should be thoroughly covered with dirt. The grass must remain covered at least six months. If manure is used it must be compact, a foot or more in depth. Straw, which is much looser, must be several feet in thickness.

Professors Eaton and Edson of Vermont report success in the treatment for quack grass, "no matter how seriously infested, by the following procedure: (1) Ridging the rows just before the corn sprouts, using a disc hoe or any other tool which makes a ridge over the row. (2) Cultivating three days later with a five-toothed cultivator, or a heavy two-horse hoe, carrying side hoes, (such as potato-hilling hoes turned backwards), drawing the soil away from the sides of the ridges previously made, so that the subsequent harrowing can more effectively level them. (3) Harrowing or weeding (preferably the former) the same day. (4) Cultivating twice thoroughly, a week or ten days later. (5) Weeding the same day, still further leveling the ridges and improving the soil mulch. (6) Cultivating thoroughly and shallow every week or ten days thereafter, so long as it can be done without injuring the crop, the oftener the better. (7) Hand hoeing in mid-July."

Perennial Sow Thistle.-The perennial sow thistle is one of the most troublesome weeds of eastern Canada and in a few of the northern states. Prof. J. E.

Howitt suggests that sheep that sheep be turned in after harvest; these animals, by close cropping, weaken the underground rootstocks. He suggests, further, that the field be cultivated until about the middle of June; to keep the tops down and weaken the roots, slightly ridge up the land with a double moldboard plow, then sow rape at the rate of one and one-half pounds per acre; cultivate the rape every week until it occupies all of the ground. He considers the rape a most excellent weed exterminator, which might be applied to many perennial weeds.

Canada Thistle.-The Canada thistle can be treated with the sodium arsenite. No other chemicals, so far as our experiments extend, will entirely destroy this weed. Carbolic acid only partially destroys the roots and the plants shoot up again from below the point of injury, but by repeating the process the Canada thistle can ultimately be exterminated. A good method to eradicate the weed is to plow shallow and cultivate frequently during the summer. The roots of the Canada thistle extend deeply down into the soil, hence for this reason deep cultivation will be of no avail. After plowing, the soil should be dragged and the roots exposed to the sun and removed, when possible. It may be necessary to run over the field with a hoe to cut off the stray plants which appear. This method was tried on a patch several years ago and no Canada thistles have since made their appearance in this place. Various crops, such as clover and sorghum, are said to be effective in subduing the thistles.

Of the various chemicals which have been used to exterminate Canada thistles none is more effective than sodium arsenite. It is applied at the rate of one and onehalf pounds to 52 gallons of water.

Carbolic acid at the rate of one part to one part water destroys the root where it comes in contact with the mixture, and for a little distance beyond. This is not an effective method, as the roots sprout out from below.

In response to circulars of inquiry sent out by the Iowa Experiment Station, the majority of correspondents recommended shallow plowing, disking, and harrowing, and continuing cultivation and hoeing as long as the thistles make their appearance. Some report successful treatment with salt when scattered thickly about the thistles, especially if cattle or sheep are given access to it. Some report success with carbolic acid where it is applied directly to the stem. Tarred paper in a few instances gave success, as did also the method where the thistle was covered thickly with straw or manure. The depth of covering was not, however, given.

Milkweed.-Milkweed, like the morning-glory, is a deep-rooted perennial, and where abundant in small grain fields it is rather difficult to remove. The plowing here should always be shallow, as the roots are deep seated and new plants spring up from where the roots are cut off. The plowing should be followed by disking and harrowing to expose as many of the roots as possible and it should be turned into pasture as soon as possible. It is seldom that milkweed becomes injurious to pastures, as the plants lose their vitality. It is by continuous cropping of one crop that the weed becomes pernicious in its character.

In response to a query sent out one correspondent recommended oats one year, clover one year, corn two. years, saying the weed is not troublesome in the pasture after the second year. Some have advocated pulling the weed by hand. This is not practical.

Horse Nettle.-In southern states north to Iowa the horse nettle is one of the most troublesome weeds to deal with. Like morning glory and milkweed, it is a deeprooted perennial. The roots are known to extend into the soil as much as three to four feet. The cultivation here should be shallow. When the weed is common, disk thoroughly and harrow, exposing the roots. When a

field is covered with it, it is better to summer fallow, then cultivate thoroughly and hoe during the entire season, or sow with oats; plow when harvested; disk and harrow for the remainder of the season. The same method used for Canada thistle may also be applied.

Wild Timothy or Dropseed Grass.-The Iowa station. has received many letters complaining about this weed. The character of the "roots" is so different from that of the roots of quack grass and the other perennial weeds that we have mentioned before that it is not difficult to exterminate. The "roots" of this weed and the allied species are more or less clustered. In an experiment conducted to exterminate this weed we found that by giving a shallow plowing of four or five inches, and harrowing to expose the roots to the sun, they were killed, no growth making its appearance during the rest of the season. Of course this is not effective during rainy weather.

Cocklebur.-The cocklebur is a serious menace to cultivated crops in many parts of the United States, more especially in southern Iowa and the South. A large number of queries sent out to farmers in different parts of the state brought many responses. Nearly every correspondent reported the weed. The seed habit of cocklebur differs materially from that of many annual weeds that belong to the same family. The bur has two so-called seeds, one of which has a slightly different position from the other; the seed coat, too, is slightly different in structure and, according to Dr. Crocker, this is the reason for delayed germination. Dr. Arthur, in a study of the same seeds, determined that the opinion generally prevailing, that one seed will germinate one season and the other the following, is essentially correct. We have found in our own work that occasionally both seeds germinate the same season. It is very plain, therefore, that if cocklebur occurs in the soil you cannot hope to destroy more than about one-half of the seeds in one season, and if the same

field is cultivated with corn the next year, another crop of seedings will come on. How long the seeds will retain their vitality has not been definitely determined. The best method of combating the cocklebur is the rotation of crops and clean culture. When a field is in corn, the field should be thoroughly cultivated and none of the plants allowed to mature seed. If they cannot be caught by the cultivator, it may pay to kill the remaining plants with a hoe, or to pull them by hand. The corn should be followed with winter rye and then oats, using the oats as a nurse crop for clover and timothy. Leave the field in meadow for at least two years and then if possible turn it into pasture. This certainly eradicates the cocklebur, ragweed and many other annual weeds.

Foxtail. It is not generally recognized, but it is probably true, that more money is spent in the extermination of foxtails than of any other class of weeds we have in the state of Iowa, yet they are all easily destroyed. One of the best and most effective methods of destroying the foxtail is by plowing the small grain field as soon as the grain is removed. If this is not done a large amount of seed is produced. After this plowing in the fall the field should be disked and harrowed in the spring and then planted to corn. The corn should be cultivated as frequently as possible, at least four or five times. This method should prove effective for the destruction of foxtail and pigeon grass.

Squirrel-tail or Wild Barley.-Squirrel-tail or wild barley is a most pernicious weed along road sides and in pastures and meadows; pernicious because it not only prevents the growth of the better grasses, but it is injurious to live stock. As this weed is most common in the pasture, the best way to treat it is to mow the pasture before the grass has matured its seed. Since this weed is an annual, or winter annual, this would effectively dispose of the plant were it not for the fact that the seed is