Aggregate analyses were made of soil samples taken at successive intervals after plowing down of alfalfa and sweet clover in rotations of legume 2 years, row crop, oats, wheat and at corresponding times in a rotation of row crop, oats, wheat. Approximately 50% higher total aggregation was found in samples taken before row crop and before oats from the legume rotations than those taken from the nonlegume rotations. Differences in aggregation were not significant in samples removed from the wheat plots either in early spring or after harvest. This apparent break down of water-stable aggregates in the legume rotations coincides with small grain yields in these rotations. The legume rotations have increased oat yields an average of 6.7 bushels over the nonlegume rotation yields, but have increased wheat yields only 1.1 bushels. It appears that the favorable effects of the legume upon subsequent small grain yields under these conditions may be largely through its effect on soil structure rather than from its influence on soil nitrogen.

Dwarf wheat plants were first obtained in F2 of crosses between Quality and P165 and between P165 and 25V112. They were also found in other crosses later. From the mode of segregation, the results can be explained on the assumption of an interaction of three complementary factors, D1, D2, and D3, and two duplicate factors, D'1 and D'3, with an addition of an inhibitor, I. The presence of all three complementary factors or a substitute of its respective duplicate factor is necessary for the manifestation of dwarf plants. The recessive condition of one of these three essential factors will give a normal plant. The presence of the inhibitor I in the presence of the three essential factors for dwarf plants also results in the production of normal plants. This assumption is substantiated further by F3 data, by data obtained in progenies of dwarf plants, and by data obtained from crossing dwarf plants to the multiple recessive stock 2905. Duplicate factor D'2 is postulated in explaining the results obtained from crossing (Onas X Fawn) to Quality and (Peiteng X Fawn) to Quality. Altogether there are three basic complementary factors, D1 D2 D3, three duplicate factors, D'1 D'2 D'3, and an inhibitor, I, that have been used to account for the genetical explanation of dwarfness in wheat. The probable genetical constitution of the different parents used is tabulated.

Greenhouse pot-culture studies to determine the nutrient value of di-guanidine phosphate, tri-guanidine phosphate, di-guanidine sulfate, and dicyanodiamide, which have been suggested as possibly possessing fertilizer value, have been made. Pot-culture experiments were conducted with millet (German), oats, and wheat. The guanidine salts were employed in the greenhouse studies in different quantities, namely, 40, 80, 120, and 160 pounds per acre in 2-8-8, 4-8-8, 6-8-8, and 8-8-8 nutrient mixtures. Compared with the control (no-nitrogen mixture, 0-8-8), the nitrogen of the guanidine compounds proved to be fairly effective at the 40- and 80-pound rates, but lowered the yields of all indicator crop plants when stepped up to 120 and 160 pounds of nitrogen per acre. These findings indicate that any attempt to use the guanidine salts as nitrogen sources would have to be made cautiously and limited to probably not more than 80 pounds of nitrogen per acre. In comparing the millet, oats, and wheat yields obtained with the guanidine salts with those from the urea and the ammonium sulfate-sodium nitrate-dried blood mixtures, the guanidine compounds generally were less effective throughout than the standard nitrogen sources. The guanidine salts gave greater increases in yields of millet on close-to-neutral soils than on distinctly acid soil. With respect to dicyanodiamide, nothing favorable can be ascribed to it as a source of nitrogen on the basis of findings in these tests. Throughout the plant tests in the greenhouse it made a poor showing, with indications of a toxic action toward the indicator plants as evidenced by a bleached-out or chlorotic appearance. It is also conceivable that bacterial action might have been inhibited so that the nitrogen of the dicyanodiamide was not rendered available in time to be of any nutrient use to the plants grown. The latter hypothesis is supported by both the ammonification and nitrification studies, which tend to show that the guanidine compounds and dicyanodiamide were not easily broken down. Of the different compounds the di-guanidine phosphate was the least resistant to change.

Iowa is a major crop- and seed-producing area. More acres of corn and oats are grown in Iowa than in any other state, and most of the seed of these crops for Iowa farmers is produced within the state. Furthermore, in 1943 over 95 percent of the corn acreage was planted with hybrid seed, and over 60 percent of the oat acreage was planted with seed of new rust-resistant varieties. Other seed crops of importance in Iowa are soybeans, bluegrass, timothy, wheat, flax, bromegrass, red clover, sweet clover, sudan grass, sweet corn, watermelon and sorghum. The yield and quality of a crop harvested each year is dependent in part on the quality of seed that is planted and the only way to know the quality factors of purity, vitality, weed seed content and sanitation is to test seed prior to planting. The purpose of this bulletin is to provide teachers and farmers with information about the need for clean seed and methods of testing seed with special emphasis on determination of pure seed, identification, of weed and crop seeds, germination tests and use of seed disinfectants for the control of molds that cause disease.

The nitrogen content of several experimental plots studied, on which a rotation including legumes was used, was higher where phosphatic and potassic fertilizers were applied than where no fertilizers were applied, in spite of greater removal of nitrogen by crops from fertilized plots. In some cases the nitrogen gain due to use of phosphorus and potassium was as much as 40 pounds of nitrogen per acre per year. The use of phosphorus and potassium on corn and wheat at Bedford, Indiana, caused an increase in the number of nodules and percentage nitrogen content of soybeans and lespedeza grown in subsequent years. In greenhouse experiments, fertilization of soybeans, alfalfa, and alsike clover increased nitrogen fixation by as much as 30% in some cases. Soybeans deficient in phosphorus are relatively lower in percentage nitrogen content and contain a somewhat higher concentration of soluble nitrogen than normal plants, suggesting that a deficiency of phosphorus may inhibit nitrogen fixation by interrupting protein synthesis. Soybeans deficient in potassium are relatively higher in percentage nitrogen and contain a lower concentration of soluble nitrogen than normal plants. These facts may be explained by assuming potassium to have some role in the synthesis or mobilization of carbohydrates.

1. Field, greenhouse, and laboratory experiments were conducted to determine the influence of acidifying treatments on yield and chemical composition of plants growing on various calcareous soils. 2. In a field experiment on Taylorsville silty clay loam, which contains 5 to 8% lime, the yields of wheat, potatoes, and sugar beets were not increased by sulfur, sulfur and manure compost, or phosphoric acid over the yields of comparable nonacidified treatments. In a 12-year study on Millville loam, which contains over 40% lime, sulfur and rock phosphate added to manure did not result in better yields than manure treatments alone. 2. In greenhouse studies the yields of alfalfa, barley, and corn growing on three different calcareous soils were not significantly increased by acidifying treatments, including two rates of sulfur, sulfuric acid, and phosphoric acid, over yields obtained from comparable treatments that were not acidifying. Irrigation water acidified to pH 3.0 by sulfuric acid decreased the yield of alfalfa. 3. In a greenhouse test with two calcareous soils and one noncareous soil, water acidified to pH 3.0 and to pH 5.0 with sulfuric acid had no significant effect on the yield or mineral content of tomato plants, but the treatments decreased the yield of alfalfa. Results on the noncalcareous soil were not appreciably different from those on calcareous soils. In this same experiment banded applications of sulfuric acid, dried manure, and treble superphosphate in various combinations showed no distinctive effects on calcareous soil compared with their effects the noncalcareous soil in regard to yield, or to iron, manganese, or calcium contents of tomato plants. The treatment means for all soils indicate that manure bands alone increased the concentration of iron in the plants. Sulfuric acid added to the manure further increased the content of iron but did not increase the manganese. Treble superphosphate decreased the iron and manganese contents. But the specific effects varied from soil to soil and indicate no distinctive benefits from the acid treatments on calcareous soils compared with a noncalcareous soil. 5. Alfalfa following the tomatoes was significantly decreased in yield by acidified irrigation waters. Phosphate content of alfalfa was significantly increased by the banded treatment combination of manure, sulfuric acid, and concentrated superphosphate. Other treatment effects were not significant. 6. Irrigation with waters acidified to pH 3.0, 4.0, 5.0, and 6.0 with sulfuric acid decreased the pH of three soils somewhat in proportion to the degree of acidity of the water used, but in no case was the pH of calcareous soils lowered below 7.0. 7. Water-soluble calcium determinations gave more consistent values in relation to the effects of sulfur and sulfuric acid treatments than did pH. Phosphoric acid decreased the pH of some soils but did not increase the calcium solubility. Farm manure treatments did not result in changes in either pH or soluble calcium in soils. The acidifying treatments showed no relationship to phosphorus soluble in a pH 5 acetate buffered solution. 8. A consideration of the results of this study and other reported investigations on the use of acidifying materials on calcareous soils indicates that there is insufficient evidence to date to warrant any widespread recommendation of such treatments for benefiting plant nutrition and growth. The value of acidifying agents in preventing phosphate reversion in calcareous soils has not been studied extensively enough to warrant conclusions.