usual period. Aside from its influence in destroying weeds, which appears to be the main purpose of all intercultural tillage, a moderate amount of stirring to a depth which will not seriously injure the roots appears, therefore, to be somewhat beneficial. If two inches of cut straw are spread upon the surface of the soil, the evaporation of water from the soil will be checked. If the surface of the soil is sheltered from rain, but exposed to the sun, and at the same time stirred to the depth, say, of two inches, the stirred portion rapidly becomes dry, and when in this condition acts as a mulch to the soil below, although not as effectively as does the cut straw. Under the above conditions the author has checked evaporation of water from the soil equal to onefourth of an inch of rainfall per week. When, however, the soil is exposed to the usual atmospheric conditions of the humid regions, where it rains one day in three, it becomes a question whether the evaporation from the lower soil is checked more than that from the stirred portion is increased. The author has concluded from pot experiments conducted during three seasons that for humid regions during ordinary weather these two factors were nearly equal, although during rainy weather the evaporation may be increased and during periods of severe drouth it may be decreased by constant surface stirring of the soil, both of which may be desirable. The average evaporation in inches of rainfall from two pots treated as indi. cated below was determined for eighty-six days during the months of June, July, August and September at the Pennsylvania Station: Evaporation in Inches of Rainfall During Eighty-Six Days. Water 19.8 One maize plant, soil cultivated One maize plant, soil mulched with cut straw 10.6 Oats followed by oat stubble 27.7 In these experiments only the loss of water from evaporation was determined. The looser soil will absorb more of the rainfall and thus lessen the amount that runs off the surface. This is especially true of compact clay soil and those having considerable slope. Generally, but not always, the looser soil will hold the most water and retard its falling beyond the reach of the roots. Since the trials which have been made indicate that surface cultivation is better than no stirring, and since occasional stirring has given as good results as frequent stirring, the inference is that so far as the conservation of moisture is concerned the most important effect of stirring the soil is to enable it to absorb and hold the rainfall. 315. Hilling and Bedding.-Some throwing of the earth towards the row is often necessary in order to cover and destroy weeds. On all well-drained soils, hilling does not give any better results WA WATER Method of bedding for low wet land. (After Hartley.) than level culture, and when, in order to hill, deep cultivation is practiced, then injury results. (312) On the poorly drained bottom lands of the Southern States bedding is practiced to give surface drainage. The Mississippi Station1 recommends that the beds be made eight feet wide or wide enough for two rows with water furrows in the alternate rows. 1 Miss. Bul. 33. XV. MAIZE. WEEDS, FUNGOUS DISEASES AND INSECT ENEMIES. 316. Weeds.-Maize differs from the other cereals in that the grain as it goes to market does not contain weed seeds, nor is there any danger of adding such seeds to the soil when the maize is planted. There are, therefore, no distinctive weeds of the maize crop, but weeds that chance to infest the soil may occur in the maize field. Fields are not infrequently cultivated in order that the cultivation incident to the maize may partially or wholly eradicate existing weeds. This, in fact, is one of the purposes of a systematic rotation of crops. Besides the injury that all weeds do, some are more troublesome than others, either through their tenacity, their immediate injury to the young maize plant, or through the inconvenience which their presence involves. Among the more troublesome weeds of the maize field may be mentioned: (1) Foxtail (Chamoeraphis). (2) Bindweed (Convolvulus). (3) Cocklebur (Xanthium canadense Mill., and X. spinosum L.). (4) Spanish Needles (Bidens bipinnata L., B. connata Muhl., and B. frondosa L.). 317. FOXTAIL.-There are two species of foxtail; one known as Pigeon grass (Chamoeraphis glauca (L.) Kuntze), and the other known as Bottle grass (Chamoeraphis viridis (L.) Porter). So far as actually reducing the yield of grain is concerned, these foxtails are probably the worst weeds that infest the maize fields. They are annuals, varying from a few inches to two feet or more in height, with dense spiked heads, yellow in Pigeon grass and green in Bottle grass. The heads are less dense and the bristles longer in the latter. Their abundance of seed, produced almost under any environment, which is evidently stored in the soil for considerable periods, makes it almost, if not quite impossible, to eradicate it permanently. 318. BINDWEED.-There are a number of species belonging to the Morning Glory family which may infest cultivated fields; the most serious are the field bindweed (Convolvulus arvensis L.), imported, and the hedge bindweed or morning glory (Convolvulus sepium (L.) Willd.), native. Both are perennial vines, with extensive underground stems, which make them practically impossible to eradicate. They may be greatly reduced by thorough cultivation. Where they are a serious pest, it is desirable to cultivate the field two years in maize, in order to reduce their injury to succeeding grain and grass crops. Good results have been obtained by using sorghum or rye as a smother crop. They do their chief injury by winding themselves about the cultivated plants. When a badly infested field is to be planted to maize, it is desirable to delay plowing until the weather is favorable for a rapid growth of maize. By this time the bindweeds will have started in the unplowed land. By plowing and immediately planting, the maize will get well started before the bindweeds have recovered from the plowing. The land should be kept harrowed, so as to prevent, as far as possible, the growth of other weeds, until both maize and bindweeds have a good start. If the bindweeds are now cut off with a hoe, and the land thereafter kept cultivated in the usual manner, no further serious inconvenience will be experienced from the bindweeds. 319. COCKLEBUR is also a branching annual, belonging to the Aster and Daisy family. It grows from one to two feet high, and is especially distinguished for its large spiny burs, which are so serious an inconvenience by clinging to the bodies of our domestic animals. Each bur contains two seeds, only one of which grows the first year, the other remaining dormant until the second year, unless the plant of the first seed has been destroyed, when, as shown by McCluer, the second seed may ger minate. The plants usually grow in such limited numbers that those which escape destruction through ordinary methods of cultivation may be pulled by hand. 320. SPANISH NEEDLES, STICK-TIGHTS, BEGGAR'S TICKS.-These are branched annuals belonging to the Aster and Daisy family (Compositae), growing two to four feet high, with brown, thin, flat seeds, two to four downwardly barbed These weeds do their principal damage by the seeds adhering to animals and clothing. Reasonably careful cultivation will destroy them. awns. 321. Fungous Diseases.-The more important fungi which attack the growing maize plant are as follows: (1) Maize smut (Ustilago zeae (Beckm.) Ung.). (2) The bacterial disease of dent maize (Bacillus cloacae Jordan). (3) The bacterial or wilt disease of sweet maize (Pseudomonas stewarti). (4) Maize rust (Puccinia sorghi Schw.). (5) The leaf blight fungus (Helminthosporium graminum Rab.). The maize smut is the only disease that has assumed any widespread economic importance. 322. MAIZE SMUT differs from the smut of the other cereals in its mode and source of infection, making its appearance upon any part of the plant above grouna; although the ears and tassels are the portions chiefly infected. Formerly it was thought that infection was largely by means of smutty seeds. It is now pretty well agreed that the principal and perhaps the only source of infection is from the flying conidia produced by the germination on the ground of the myriad spores of the smut boil. Warmth, moisture and soluble food material are very essential to the germination of the spores and the spread of the disease. Naturally, therefore, as the season of active growth progresses the conditions favorable to spore germination increase and the number of pustules is increased as the foliage, tassels and silk increase to afford a suitable matrix for the conidia. The abundance of silk and the great amount of nourishment in the grains explain the enormous development of the smut boils, which often attain the size of a man's head. The infection is purely local; the disease does not spread, as is shown by the appearance of the smut boils at the point of infection two to three weeks after the conidia have made their entrance into the host. Thus, it is seen that infec tion may take place at any time in the growing season, and the longer the season of growth, the greater the infection is likely to be. It is reported that sweet maize is more susceptible to the disease than the ordinary field maize; estimates on the percentage of infection of the latter have been variously stated at from five-tenths to twenty-six per cent. It therefore follows that the extent of infection depends considerably upon five factors: (1) seasonal conditions, a rainy season tending to keep much of the conidia washed out of the air, while much dry weather is fatal to the germinative powers; (2) the thickness of planting, the moisture held by the plants being increased as the foliage is multiplied; (3) the presence of decayed vegetable matter; (4) manure, which may be infested with spores; (5) the degree of maturity of the different parts of the plant. The only practical method of prevention, so far as known, is to gather all smut pustules as they appear, care being taken to prevent scattering the black powder (spores), two or three times in the growing season and destroy them by burning or placing in boiling water. Great care should be taken, also, in seeing that, as far as possible, the manure for the maize field is free from spores. Experiments have shown that the hot water treatment used for smut of oats and wheat is of no avail in combating maize smut; this is explained by the fact that inoculation of the host comes not from the seed but from the flying conidia which alight upon the growing plant. Maize smut has been fed to cattle in numerous instances in large quantities for a considerable period of time without apparent injury.1 Maize smut boil. 323. BACTERIAL DISEASE.-There has been observed in Illinois and other North Central States a bacterial disease of maize, which not only does considerable damage to maize in some localities, but it is supposed that the germ which causes the disease in maize is able to cause a sudden and fatal disease in cattle, L 1 For detailed study of maize smut, see Ind. Rpt. 1899 (12), pp. 84-135; also Farmers' Bul. 69; Kan. Bul. 62; Ohio Bul. 78. |