This Guide provides access to the content of Wheat studies, a series published in twenty volumes from 1924 to 1944. The series presented research results on the role of wheat in world economics.--Cf. Foreword.

Applications of sodium nitrate to wheat were made at a number of periods during the growing season under conditions under which no definite response with respect to yield was obtained. The results show that (a) the protein content increased gradually the nearer the applications were made to the time of heading and declined again on the plots on which the applications were made after this stage of growth, (b) that the sulfur content followed in a general way the same course as the protein content; and (c) that there was no correlation between the protein content and the weight per bushel and weight per 1,000 kernels.

Milling, baking, vitamin B1 (thiamine), and germination tests have been made of nine samples of Marquis wheat grown for the crop years 1921 to 1927, inclusive, and 1929 ad 1942, and of Kanred wheat grown for the crop years 1921, 1924, and 1929. The wheat samples were stored at Fort Collins, Colo., in a dry, unheated room for periods varying from 14 to 22 years. Twenty-two per cent of Mqrquis and 4% of Kanred germinated after storage for 22 years. Storage had no consstent effect on the protein content of the grain. The ash content of the flour increased somewhat with storage, due perhaps to brittleness of the bran coat, with the result that more of it pulverized in milling and was carried over into the flour. There was a definite and fairly regular but small increase in fat acidity with storage, those samples stored fro the longer periods having fat acidity values which ordinarily would be indicative of considerable deteriortion. Such deterioration, however, was not apparent from the bread baking tests, since satisfactory bread was made from all lots of flour. The best bread ws made from the 1921 crop, the small difference as compared with later crops being due, no doubt, to the higher protein content of the flour. Determinations of thiamine content of the wheat, flour, and bread were made in 1943. The differences were no greater than might reaosnaby be attributed to differences in the grain when it was first stored.

A survey of published field tests shows that in many cases persistent increase of the amount of fertilizer added to the soil results in depression of the normal yields of all kinds of crops, due to the creation of nutritional unbalance. Failure to preserve nutritional balance seems to be a major factor in repressing the fertility of the soil, and is one of the barriers to full exploitation of the known great inherent growth-energies of useful crops. Measures for correcting or avoiding nutritional unbalance require first of all a means of recognizing it and measuring its degree. Such a means is found in the use of the standard yield diagram, which is based on the Mitscherlich-Baule theoreum. On the South Carolina farms represented in the examples here given soil nitrogen is evidently in excess when its total amount exceeds 0.30 or 0.36 baule. Potash is out of balance when its amount exceeds 0.6 baule. In the Illinois soils considered, potash is not out of balance with corn and wheat when its average amount is about 2.0 baules. With soybeans, unbalance with potash begins at about 0.6 baule. Proof is cited that nutritional or agrobiologic unbalance arising from an excess of one nutrient (N for example) may be corrected by an additionof a deficient nutrient. This corrective effect is, of course, just another verification of the agrobiologic law that quantitative plant growth depends on a harmonic balance of all its factors.

1. Individual native grazing plants, whether grasses, shrubs, or nongrassy herbs, have distinctive growth habits and feeding values. The native forage crop is composed of many species, thus making its management more difficult than a single farm crop like corn or alfalfa. 2. The mixed prairie is composed of climax midgrasses, short grasses, and dryland sedges, plus a variety of subdominant nongrassy herbs. 3. Grasses and other vegetation have been modified throughout the ages as environment has been changed by shifting climates. 4. The mixed prairie supports nearly one-fourth of the livestock in the United States west of the 98th meridian. 5. The cool season midgrasses, and palatable nongrassy herbs, are the first plants to go out under heavy grazing and drought. 6. The drought-resistant summer-growing short grasses, dryland sedges, Sandberg bluegrass, and unpalatable nongrassy herbs increase during the first stages in the depletion of excellent mixed prairie grasslands. 7. The following annual grasses and weeds increase on depleted mixed prairie ranges: Lambs quarter, Russian thistle, Woolly Indian wheat, sunflower, peppergrass, six weeks' fescue, witches' broom, Japanese chess, cheatgrass brome, little barley, and false buffalo.

A mathematical model of wheat bunt field trials has been constructed which seems to be adequate. The mean and spread of the heterozygous plants cannot be observed, but these can be calculated because the means and variances of the percentages for the homozygous and segregating rows can be observed and it can be assumed that the probabilities of infection for different types of plants are perfectly correlated as between rows. The variance of the percentages for the segregating rows results from the probabilities of infection for the various genotypes present. For the data presented the variance for the segregating rows was very close to the binomial variance, although the variances for the homozygous rows are considerably greater. This apparent inconsistency did not result from different a values for the genotypes of plants present. It was shown that by using a value of 1.6 for a1 and a2 the calculated errors resulting did not differ significantly from those observed. It was assumed that the spreading effects noted in this experiment were due to environmental influences. Modifying factors would have a similar effect and probably the two could not be distinguished unless the modifiers affected only some genotypes. This model should be of aid in interpreting complex hybrids in that the nature of the variances will be understood better. This is particularly true where a row or family is heterozygous or made up of plants of different genotypes which have different probabilities of infection. It also indicates that the spread of the percentages depends on the length of rows, the spread of infectivity levels, and the general level of infection. The considerations involved in developing this model apply to developing models for any similar experiments. The results of the mathematical model have been applied in detail to extensive genetic data from a cross between Banner Berkeley and Baart wheats. The results are consistent with the assumption that the spreading effect as measured by a is independent of genotype and length of row. This assumption is probably only true for certain ranges of genotypes and lengths of row.