v | ok | Kirjasto Aj-k | On the resistance of spring wheat to yellow rust

The residual effect of previous irrigations showed up on the following Marquis wheat crop. Where water was applied late in the growing season, that is at "heading," "blossoming," or "filling," the following crop was influenced more than where water was applied at "germination," "tillering," or where the plats received a "distributed" irrigation. When the crops of the two years were combined the plats receiving a "distributed" irrigation gave the highest yield of grain and straw. The plats irrigated at "heading" gave the highest yield of the plats receiving a single irrigation of 6 inches. Soil moisture determinations made at the end of the first season showed that more moisture was left in the first 5 feet of soil when the plats were irrigated at "filling" and that the amount decreased with the earlier application. The rainfall during the crop year affected the yield but not the ranking of the different treatments. The succeeding crop grown on the plats irrigated at "filling" gave the highest yield whether the rainfall was 5.64 inches or 23.26 inches.

The time of applying irrigation water is an important factor in spring wheat production. Water applied at "jointing" increases the yield of straw and grain but not the quality of the grain as indicated by bushel weight and weight per 1,000 kernels. When water is applied at "heading" slightly lower yields of grain and straw are obtained than when water is applied at "jointing." But the quality of grain is materially improved as indicated by bushel weight and weight per 1,000 kernels. Irrigation as late as "blossoming" and "filling" has very little effect on yields of grain or straw, but has a marked effect on grain quality as indicated by weight per measured bushel. Late irrigations at "heading," "blossoming," and "filling" have a residual effect on the following crop. Early irrigations at "germination" and "tillering" increase the straw yield to a greater extent than the grain yield but produce a grain of poor quality. Irrigations of small amounts (1 inch) distributed through the growing season give the best results but are impractical. Soil moisture experiments carried out in potometers did not agree with similar experiments carried out under field conditions.

The methods of measuring quality varies with the crop and the purpose for which the crop is grown. Quality depends upon the market demands and in many instances there are no standards with which to measure quality. Evidence has been gathered from literature indicating that potash is an important element in producing quality in potatoes, sugar crops, corn, wheat, tobacco, and soybeans. The evidence is not clear as to just what form of potash produces the most desirable quality in every case. In some cases potash does not have any effect upon the quality of the crop grown and in such cases it is to be supposed that there is plenty of potash available in the soil. The problem then becomes one of providing a balanced ration by supplying other plant food needed. An example of this is the supplying of nitrates in order to obtain hard wheat in Colorado. Conflicting results in many cases may be due to the impurities carried by the potash fertilizers or to variation as to the kind and amount of impurities carried by a given potash fertilizer. There is a need of some well-defined investigations along this line. A plant may need the element potassium in order to produce a high quality product, but the potassium may be supplied in a form that carries an acid radicle that is inhibitive to the proper growth and development of the plant. These acid radicles may be chlorid, sulfate or phosphate in the most commonly used potassium salts. A small percentage of any or all of these acid radicles may not inhibit the production of a high quality product or one of these acid radicles may be inhibitive and the remainder harmless. Investigations are needed as to the relation of the quality of product produced with these various acid radicles in potassium salts and the percentage of each that is permissible. The results that have been reported were carried on with various soil types. The properties and reactions of these soil types are not all the same. Some soils may possess properties that counteract the undesirable reactions of impurities in potassium salts or fertilizer mixtures, while others do not possess such properties. Likewise, the harmful effects of certain of the acid radicles may be counteracted by the properties of some soils and not by others. It is important, therefore, to consider the soil type in planning an investigation of this nature, and in making recommendations to make them only for the soil type upon which the study has been made.