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Hydraulic tables
1933
Williams, Gardner S. | Hazen, Allen
The colorimetric determination of sodium in vegetation Texte intégral
1933
(1) A revision of the method by Malan and Van der Lingen for the colorimetric determination of sodium in vegetation is described in detail. (2) Evidence is presented to show that:- (a) .04-0.1 mgm. Na can be determined with reasonable accuracy in the presence of 0.1 mgm. P; when 0.1- 0.2 mgm. Na is to be determined 0.2 mgm. P, and when 0.2-0.8 mgm . Na, up to 0.4 mgm. P may be present. (b) The interference of K is dependent upon absolute concentration and temperature; working at ordinary laboratory temperature ( ± 25° C.) not more than 0.8 mgm. K should be present in the aliquot for a determination. (c) At 26° C. precipitation is complete within experimental error in 30 minutes.
Afficher plus [+] Moins [-]Lodging in small grains Texte intégral
1933
Clark, E.R. | Wilson, H.K.
Rates of tillering were studied in 24 varieties of spring and durum wheat and 17 varieties of barley grown in the 1/40 acre varietal plats at University Farm, St. Paul, Minn., in 1931. No differences in the tillering rates of wheat plats were found which could be attributed to genetic differences in the varieties, since the variance between the average tillering rates was not statistically significant. However, a study of the partial correlation between tillering rates in series I and tillering in series II, holding stand constant, indicated that differences in tillering were associated with differences in stand. It is suggested that these differences in stand may have been due to differences in the number of seeds sown on unit areas, since the plats were sown at uniform rates by weight and the varieties varied somewhat in size of seed. No correlation was found between the tillering rates of wheat varieties in these trials and the lodging behavior of the same varieties at Morris in 1930. The 17 varieties of barley differed significantly in rates of tillering. These differences in tillering were not entirely associated with differences in stand. It is believed that these differences may be genetic. The breaking strength of wheat culms was determined by breaking 10 culms from each of the three plats of each variety. The differences in breaking strength were found to be significant. The correlation coefficient between breaking strength and diameter of culm was .537 +/- .148. The breaking strength of the varieties as determined in these trials was compared with the lodging behavior of the same varieties at Morris in 1930 and at four Minnesota stations in 1928, 1929, and 1930. No correlation was found between breaking strength and lodging in either of these comparisons. Three durum varieties included in the study had higher breaking strength, greater diameter of culm, and lower tillering rate than the common wheat varieties.
Afficher plus [+] Moins [-]Chemical blood studies. II. A contribution to the determination of urea in animal blood filtrates ("laked" and "unlaked") Texte intégral
1933
The series of five papers deal with blood levels in health and disease, in respect of total nitrogen, non-protein nitrogen, total creatinine, urea, uric acid, amino acids, sugar and haemoglobin. Protocols are numerous and of a nature which necessitates consultation in the original text, but the general trend of the data may be indicated. The first paper deals with technique and the general plan of investigation. The second discusses the influence of pH on urease activity in the determination of blood urea. The third deals with changes in sheep's blood during the pre-infection period, the incubation period, the hyperthermic reaction and the convalescent period, of R. ruminantium infection and catarrhal fever. Considerable changes are recorded, varying with the severity of reactions. The fourth paper deals with 14 cases of horse-sickness. Alterations in nitrogen partition were not pronounced. The fifth paper records alterations in practically every constituent determined, in cases of A. marginale infection. Babesia bigemina infection showed increase in all nitrogenous fractions and in sugar, associated with the period of maximum erythrocyte destruction.
Afficher plus [+] Moins [-]Chlorophyll content as an index of the productive capacity of selfed lines of corn and their hybrids Texte intégral
1933
Sprague, H.B. | Curtis, N.
1. In a study of methods, it was found that the area of corn leaf blades could be determined as accurately by the formula length X greatest width X 0.75, as by planimeter readings of blue-printed leaf outlines. Leaf areas may conveniently be determined from growing plants by this method without injury. 2. Both chlorophyll and carotin were most concentrated in the uppermost leaves and least in the bottom leaves. The gradient between the uppermost and lowest leaves was fairly regular, and the middle leaf or leaves of the plant exhibited practically the same concentration of pigment as the average for the whole plant. Xanthophyll values were erratic and no significance was attached to such observations. 3. Estimates of total chlorophyll content per plant based on the concentration of the pigment in the middle leaf and on the leaf area determined by the formula were practically as reliable as complete analyses of all leaves. Carotin content of plants was also estimated satisfactorily by this method. A Ganong leaf punch which clips circles 1 sq. cm. in area was used to sample leaf blades without appreciably disturbing the living plant. 4. A group of 12 newly homozygous selfed lines selected basis of observed greenness of leaves in 1929 varied in chlorophyll concentration from 5.14 mgms. of chlorophyll per 100 sq. cm. of leaf for the lightest strain to 11.30 mgms. for the darkest green strain when grown in 1930. Total chlorophyll per plant ranged from 106 to 407 mgms., although no strain showed obvious chlorophyll defects. The 12 strains also differed widely in leaf area, total yield of dry matter, and shelled grain. 5. Eighteen first generation hybrids involving the 12 selfed lines were chosen to represent all combinations of greenness. The chlorophyll concentration within this group ranged from 6.23 to 11.61 mgms., and the total chlorophyll from 332 to 607 mgms. From the chlorophyll content of these hybrids, it appeared that chlorophyll concentration of a given strain may either be genetically recessive, dominant, partly dominant, or cumulative in relation to that of other selfed lines. 6. The mean values of the attributes for the, parents of each hybrid suggest that chlorophyll inheritance is controlled by a relatively small number of genetic factors in contrast with leaf area and yield. Chlorophyll concentration in leaves of the hybrids was only slightly greater than the mean value of the parents, whereas leaf areas and yields were 50 to 100% higher. 7. Correlation coefficients between attributes of the 12 selfed lines indicated that total chlorophyll was significantly related to chlorophyll concentration, leaf area, yields of total dry-matter, and shelled grain. Chlorophyll concentration was correlated with shelled grain and leaf area, but not with total dry matter. 8. Within the group of 18 hybrids, total chlorophyll was more highly correlated with yields of total dry matter and grain, leaf area, and chlorophyll concentration than any other attribute. Chlorophyll concentration was significantly correlated with production of total dry matter, but not with leaf area. 9. Mean values of the parental attributes of total chlorophyll, chlorophyll concentration, and leaf area were all significantly correlated with total dry weight of the hybrids. Mean chlorophyll concentration of the parents was also closely related to chlorophyll concentration and total chlorophyll of the hybrids. 10. The mean values for chlorophyll concentration and total chlorophyll of selfed lines are reasonably reliable indexes of the total yield that will be produced by their hybrids. Light green inbreds with other desirable attributes should be mated with dark green rather than light green strains for best results. Selection of dark green plants in successive generations of segregating strains should be an aid in isolating prepotent lines.
Afficher plus [+] Moins [-]Chemical blood studies. I. Comparative studies on blood, "laked" and "unlaked" blood filtrates of animals in health and disease, with particular reference to methods and technique employed Texte intégral
1933
The series of five papers deal with blood levels in health and disease, in respect of total nitrogen, non-protein nitrogen, total creatinine, urea, uric acid, amino acids, sugar and haemoglobin. Protocols are numerous and of a nature which necessitates consultation in the original text, but the general trend of the data may be indicated. The first paper deals with technique and the general plan of investigation. The second discusses the influence of pH on urease activity in the determination of blood urea. The third deals with changes in sheep's blood during the pre-infection period, the incubation period, the hyperthermic reaction and the convalescent period, of R. ruminantium infection and catarrhal fever. Considerable changes are recorded, varying with the severity of reactions. The fourth paper deals with 14 cases of horse-sickness. Alterations in nitrogen partition were not pronounced. The fifth paper records alterations in practically every constituent determined, in cases of A. marginale infection. Babesia bigemina infection showed increase in all nitrogenous fractions and in sugar, associated with the period of maximum erythrocyte destruction.
Afficher plus [+] Moins [-]Chemical blood studies, III. Comparative studies on "laked" and "unlaked" blood filtrates of sheep in health and during "heartwater" (Rickettsia ruminantium infection) and bluetongue (catarrhal fever) Texte intégral
1933
(1) The total nitrogen and haemoglobin of whole blood, and the sugar, urea, amino-acid, "total" creatinine, uric acid and non-protein nitrogen of "laked" and "unlaked" blood filtrates of sheep have been determined. (2) Determinations were made during the pre-infection period ("normal"), the incubation period, the actual hyperthermic reaction stage, and in recovery cases during the convalescent stage, until the level of the blood constituents had returned to normal. (3) "Normal " data in respect of the above constituents for both "laked'' and "unlaked" filtrates have been separately detailed. ( 4) As far as differences in the two types of filtrates are concerned, the concentrations in "laked" filtrates are in all cases higher than in the "unlaked", the difference being least in the case of urea. (5) Temperature charts to show the nature and type of the reaction, as well as the periods at which blood was withdrawn, have been incorporated. (6) Well marked changes are recorded in Heartwater and Bluetongue, the degree of the change corresponding approximately to the severity of individual reactions.
Afficher plus [+] Moins [-]Soil rebuilding at the Red Plains Erosion Station Texte intégral
1933
Phillips, S.W.
The investigations fall under three major groups, as follows: (1) Fundamental studies of erosion and run-off rates, fertility losses, and the processes involved, under various condition of slope and cropping and tillage practice; (2) experimentation with various vegetative and artificial means of erosion control; and (3) soil rebuilding after depletion by erosion. Under the first head the effects of such factors as length of slope, crop rotations, sod and forest covers, bare surface condition, absence of topsoil, fall and winter plowing, and burning off of woodlands are being quantitatively measured in terms of run-off, wash-off, plant food losses, and crop yields. Along with these measurements are determined also the precise effect of crops, rotations, tillage methods, and terracing on moisture conservation. Under the second heading the effectiveness and cost of strip cropping, contour cultivation, and various other adaptions of cropping and tillage methods, subsoiling, terracing, and the building of dams as implements of erosion control are being worked out.
Afficher plus [+] Moins [-]Hard seed in Korean lespedeza Texte intégral
1933
Middleton, G.K.
Ten well-matured samples of Korean lespedeza seed were tested at monthly intervals from November 1931 through March 1932. The results show a rapid decrease in the hard-seed content and a corresponding increase in germination for each sample from November through January, but with very little further change by March. The average percentages of hard seed for November, January, and March were 47.25, 12.25, and 11.05, and the average percentages of germination for the same periods were 46.70, 83.30, and 84.85, respectively. The data show that, if satisfactory results are to be obtained, germination tests should be delayed at least until January following harvest. This conclusion is substantiated by reports on several hundred samples of seed tested during the past 3 years. The results of tests made in the fall of 1931 and in March 1932, on 30 samples of seed, show that when tests are made early in the season the total viable seed content (germination plus hard seed) is a more reliable guide to the agricultural value of the seed than is germination alone. For samples of well-matured, bright, plump seed, the deduction of 15% from this total, as determined in the fall, has proved a safe estimate of the actual germination obtained the following spring.
Afficher plus [+] Moins [-]The phosphorus concentration of the exuded sap of corn as a measure of the available phosphorus in the soil Texte intégral
1933
Pohlman, G.G. | Pierre, W.H.
The determination of the PO4 content of the exuded sap of corn plants is suggested as a method for measuring phosphorus deficiency in the soil. This sap appears to offer all the advantages of the expressed juice without such disadvantages as the possibility of change in composition due to expression. In addition, it is easier to collect and analyze than is the expressed plant juice. The amount of inorganic PO4 found in corn sap varied from 62 to 602 p.p.m. Usually the amount increased with the age of the plant. The results obtained under greenhouse conditions show a good correlation with the response of corn to phosphate fertilization and also with the water-soluble PO4 and the available PO4 as determined by the Truog method. The data seem to justify additional tests with the method in order to ascertain limiting concentrations of PO4 for normal growth. Certain factors, such as light, temperature, moisture condition of the soil, supply of other nutrients, age and metabolic condition of the plant, and height of cutting, may affect the results and these should be considered in further studies of the method. Although no data are presented in this paper to show the concentrations of other nutrients in the exuded sap it would appear that the method might be used to advantage in a study of the availability of various elements, particularly nitrogen and potassium.
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