Soil Research Bodenkundliche Forschungen Recherches sur Ie Sol

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— 52 — Each plot was sampled by drawing a soil sample of 6 inches depth from centre. Thus the total number of samples drawn per plot of 0.0235 acre, was 64. An additional sample was taken at the centre spot. The samples were all air dried and mixed thoroughly. The soluble salts contents were determined in each of these samples individually and also in a series of systematic combinations which gave results agreeing well with the averages from the individuals which were mixed together. The individual plot data are given in Table I but those for the combined samples are not presented here. An analysis of the data for each of the four areas is given in Table 2. The sums of squares for deviations are given first for the 63 degrees of freedom. In the second stage the areas are divided symmetrically into quarters of 16 plots each, and the sums of squares assigned to 3 degrees representing the average differences between these blocks of 16 plots, and to 60 degrees representing the differences within the four blocks of 16 plots each. In the third stage the area is divided into sixteen blocks, each of 4 plots, and the sums of squares assigned to 15 degrees of freedom between the blocks of 4 plots and 48 degrees of freedom within these blocks. The mean squares per degree of freedom show that the unirrigated area II was particularly irregular, even when the sampling was limited to blocks' of 4 plots. The irrigated area IV was much more uniform than any of the others. In areas I, III and V the mean squares for samples within blocks of 16 or 4 plots were markedly lower than those for samples drawn from the whole area, the mean square for samples from blocks of 4 plots being about one-half of that from the whole area of 64 plots. The square root of the mean square gives the standard error per sample and, when divided by the square root of the number of blocks (4 or 16 respectively) gives the standard error of a single composite obtained by bulking together 4 or 16 soil samples taken one from each block. In the most variable area (Unirrigated II) a composite sample of 16 cores, each taken to represent one-sixteenth of the whole area, would have a higher standard error than composites of four cores, each representing a quarter, from any of the other three areas. Except on such highly irregular soil a composite made up of four cores selected at random, one from each quarter of the experimental area of 1/40 th. acre, gave standard errors ranging from 0.066 % to 0.117 % on mean values of 1.23 % to 2.41 %. Such samples should be sufficient to represent
— 53 — Table II Degrees of freedom Unirri gated area I area II Irrig ated area III area IV Mean percentage of salts — 1.23 4.42 2.41 1.26 Total Sum of Squares . . . a) Between blocks of 16 plots . Within blocks of 16 plots . 63 3 60 35.0426 10.9212 24.1214 171.9210 10.5623 161.3587 29.0464 10.0997 18.9467 9.7350 3.8062 5.9288 b) Between blocks of 4 plots . Within blocks of 4 plots . 15 48 24.7290 10.3136 59.3076 112.6134 18.4570 10.5894 6.4139 3.3211 Mean Squares a) Within blocks of 64 plots . b) Within blocks of 16 plots . . c) Within blocks of 4 plots . . • 0.5562 0.4020 0.2149 2.7289 2.6893 2.3461 0.4611 0.3158 0.2206 0.1545 0.0988 0.0692 Standard Errors a) Single sample of 64 plots . . b) Composite of 4, one fromeach block nf 16 _____ c) Composite of 16, one from each block of 4 0.7458 0.3170 0.1159 1.6519 0.8200 0.3829 0.6790 0.2810 0.1174 0.3931 01572 0.0658 the salt content of plots in replicated experiments, with the provision that more elaborate samples are needed for very irregular soils. Conclusions Pour areas, each of 1/40 th. acre, were suh-divided into 64 plots and the salt content of a sample from each plot determined. Except on very irregular soil, it was shown that the plot could be well represented by a single composite sample made up of soil from four random spots selected one from each quadrant in the area.
Seite 1 und 2:
Vol. Bd. VI 1938 Nol Soil Research
Seite 3 und 4: Soil Research—Bodenkundliche Fors
Seite 5 und 6: — 3 — Chemical Decomposition of
Seite 7 und 8: — 5 — Table III Changes of Coll
Seite 9 und 10: — 7 — changing wet and dry seas
Seite 11 und 12: — 9 — Testing a soil sample tak
Seite 13 und 14: — 11 — The chemical analysis of
Seite 15 und 16: — 13 — The study of the replace
Seite 17 und 18: — 15 — b) The increase in the a
Seite 19 und 20: — 17 — creases towards the lowe
Seite 21 und 22: — 19 — 5. In individual cases t
Seite 23 und 24: — 21 Über starre und elastische
Seite 25 und 26: — 23 — a) den eigentlichen Chem
Seite 27 und 28: — 25 — Tabelle 1 Vergleich eini
Seite 29 und 30: — 27 — C. Starre und elastische
Seite 31 und 32: — 29 — sich die Zusammenhaltsen
Seite 33 und 34: — 31 - Graphir Grflphlt-Sdure ela
Seite 35 und 36: — 33 — W. L. Bragg, U. Hofmann
Seite 37 und 38: — 35 — IV. Die elastische Struk
Seite 39 und 40: — 37 — Aenderung desNetzebenen-
Seite 41 und 42: — 39 — Ol CS A OC o m ^ = ^ —
Seite 43 und 44: 41 oo c c a> E .o lO tri o T-H '^
Seite 45 und 46: — 43 — Tabelle 7 (nach Versuche
Seite 47 und 48: — 45 — Aenderung des Umtausches
Seite 49 und 50: — 47 — kurve in Fig. 13 nach re
Seite 51 und 52: — 49 — Sampling error in irriga
Seite 53: — 51 "IRUP^^ Table I (contd) Perc
Seite 57 und 58: — 55 — Pflanzenwachstum, Bakter
Seite 59 und 60: 57 — ^=r Abb. 1. Entnabmegerat, A
Seite 61 und 62: — 59 — Die Stechzylinder sind n
Seite 63 und 64: — 61 — Die Probenahme geschieht
Seite 65 und 66: — 63 — die Zylinderproben auf W
Seite 67 und 68: ir Bio- ^ellung aahme liesem eine l
Seite 70: The General Committee of the Intern
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