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Partitioning variation in chemical properties of some andepts — A comparison of classification systems
Geoderma, 29 (1983) 13--26
13
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
PARTITIONING VARIATION ANDEPTS-- A COMPARISON
IN CHEMICAL PROPERTIES OF SOME O F C L A S S I F I C A T I O N S Y S T E M S .1
R.S. YOST and R.L. FOX
Department of Agronomy and Soil Science, University of Hawaii, Honolulu, HI 96822 (U.S.A.) (Received October 10, 1981; accepted after revision June 26, 1982)
ABSTRACT Yost, R.S. and Fox, R.L., 1983. Partitioning variation in chemical properties of some andepts -- A comparison of classification systems. Geoderma, 2 9 : 1 3 - - 2 6 . One purpose of classification systems is to group objects with similar properties so that meaningful generalizations can be made concerning their properties, behavior and potential use. It has been difficult to measure the success of such groupings. Similarly it has been difficult to determine how well soil classification systems group properties different from the criteria upon which the systems are based. Eighty soil samples (0--15 cm depth) of the Andept suborder were collected from the Island of Hawaii. Soil chemical properties (pH, exchangeable cations, extractable P, P sorption, and silicon) were measured. The 80 soils were grouped according to Soil Taxonomy, the proposed Andisol order of Soil Taxonomy, the FAO Legend for the Soil Map of the World, the French Classification System, and the 1938 Soil Classification System. Each system's effectiveness in grouping was compared by using regression techniques based on the statistical model of the classification scheme. Each system had a specific category which most effectively grouped soils with similar properties. The most effective category (that which decreased the pooled variance most) was the great group level of Soil Taxonomy, the suborder level of the proposed Andisol order of Soil Taxonomy, the Groupe level of the French System, and the suborder level of the 1938 System. In considering the FAO legend, only soil units were examined. These effectively separated variation in most soil properties in this group of soils. As indicated by the greatest precision (smallest pooled variance) Soil T a x o n o m y was effective in grouping all soil chemical properties except Na, whereas grouping 80 soils into 3 orders of the 1938 System did not increase homogeneity within groups. The Groupe category of the French System which formed the 2 taxa of saturO and desatur$ was effective for most properties, especially soil pH. In our case the two Andisol suborders were identical within the Groupe level of the French System (satur~ and desatur~), whereas the four taxa of the Andept great group category corresponded with four great groups of the proposed Andisol order. Lower categories of Soil Taxonomy, the 1938 System, or the French System did little to increase precision, suggesting that differentiae of the lower highly defined categories studied here were correlated with those of more general higher categories. .1 Journal Series no. 2614 of the Hawaii Agric. Exp. Stn. This work was supported by a 211(d) Basic Grant (AID/CSD-2833). All reported opinions, conclusions, and recommendations are those of the authors and not those of the funding agency or the U.S. Government.
0016-7061/83/0000--0000/$03.00
© 1983 Elsevier Scientific Publishing Company
14 INTRODUCTION One of the purposes of classification is to group items that have similar properties so that meaningful general statements can be made about those properties and potential use. Such groupings of soils improve the understanding and use of soil resources. It is sometimes difficult to quantify the success of such groupings, or to quantitatively compare properties n o t expressly col~ sidered in soil classification systems. The criteria for Andepts (Andisols), for example, include consideration of subhorizons. For specific purposes such as crop production, the surface soil properties are more influential than subsoil properties. It can be useful to determine what inferences of surface properties are given by systems based, in part, on subsurface horizons. Similarly one could compare how well classification systems group crop yields, soil water properties, microbiological populations, disease incidence, etc. All of which are not directly used as classification criteria. Soil classification schemes can be compared by examining the way partitioning of total variation in selected soil properties has been effected in a group of soils (Yost and Fox, 1981). Effective soil classification schemes should designate homogeneous groupings of soils for one or more properties. Mean values of such a soil property within each group may suggest management needs for soils of t h a t group. Also, the more detailed, lower level taxa should be more homogeneous than higher level categories and this should be indicated by smaller within-group variances. These criteria were used to compare Soil T a x o n o m y with other soil classification systems in partitioning variation in soil chemical properties of certain Andepts. MATERIALS AND METHODS Soil samples were collected along transects on the Island of Hawaii. Samph~ collection procedures were described by ~ ost and Fox (1981). Data reported here represent samples from the 0- to 15-cm depth. Sample locations, 164 in number, were recorded from published soil maps of the Soil Survey of the Island of Hawaii (Sato et al., 1973). Of the soils sampled, 20 soil series were in the Andept suborder of Soil T a x o n o m y (Soil Survey Staff, 1975). The 20 series (Table I) were placed into other classification systems as suggested by Beinroth et al. (1979). Classification of the 20 series according to the proposed Andisol order of Soil T a x o n o m y (Smith, 1978) followed the work of Recel et al. (1981). The soil order Andisol was proposed to consider or improve consideration of soil moisture regimes and water retention properties, variable charge properties, particle size and mineralogy. Proposed suborders include aquands, borands, xerands, ustands, tropands, and udands. Softs of this study were either ustands or tropands. Further modifications have been discussed by Leamy {1982). The soil series and mapping unit categories were included in computations
15 TABLEI Soil series names and soil family designations of 80 samples of Andepts used in this study Series
Family
Akaka Apakuie Hanipoe Hilo Honokaa Kaiwiki Kealakekua Kikoni Kilohana Kukaiau Laumaia Maile Naalehu Olaa Pakini Palapalai Punohu Puu 0o Puu Pa Waimea
Thixotropic, isomesic, Typic Hydrandept Medial, isomesic, Umbrie Vitrandept Medial, isomesic, Typic Dystrandept Thixotropic, isohyperthermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Medial, isothermie, Typic Eutrandept Ashy, isomesic, Mollic Vitrandept Thixotropic, isothermic, Hydric Dystrandept Medial, isomesic, Typic Dystrandept Thixotropic, isomesic, Hydric Dystrandept Medial, isohyperthermic, Typic Eutrandept Thixotropic, over fragmental, isohyperthermic, Typic Hydrandept Medial, isohyperthermic, Entic Eutrandept Medial, isothermic, Typic Entrandept Thixotropic, isomesic, Hydric Dystrandept Thixotropic, isomesic, Hydric Dystrandept Medial-skeletal, isothermic, Ustollic Eutrandept Medial, isothermic, Typic Eutrandept
of pooled variance, although neither the French System nor the FAO legend have these categories. Similarly, the mapping unit was included in the Soil T a x o n o m y model while recognizing t ha t this category is n o t part of the system. This addition was useful in demonstrating the effectiveness of the categories immediately above the series category in both the FAO legend (soil units) and the French system. The 1938 Soil Classification System r e p o r t e d here was that applied to Hawaii by Cline (1955) and includes the suborder "D eep Unconsolidated Soils" n o t f o u n d in the original 1938 system. This system is now archaic and was included only for comparison. Means are given for the category of each system that account ed for the most variation in soil chemical properties. Statistical calculations were made using the Statistical Analysis System (Barr et al., 1979). Normality of the data was analyzed by the KolmogorovSmirnov statistic. The general linear models procedure (GLM) was used for c o m p u t i n g the unbalanced analysis of variance. Estimates of precision for each t a x o n o m i c category (pooled variance) were obtained by regression soil properties on d u m m y variables t hat assumed unique values for each taxa of the category. Because the statistical models of these systems are all hierarchical, the residual mean square of the regression of soil properties on individual categories provides a pooled estimate of the variances within
16 the c a t e g o r y taxa. F u r t h e r testing is possible b y d e t e r m i n i n g if the individual t a x a variances are h o m o g e n e o u s a n d if d i s t r i b u t i o n s are n o r m a l . Statistical m o d e l s f o r the various classification s y s t e m s follow. Soil T a x o n o m y Y = p + A i + Bij + Cijk + D i j k l + E i j k l m + Fijklm n + Gijklrn n o + eijktm nop w h e r e Y is t h e value o f t h e soil p r o p e r t y , A = order, B = s u b o r d e r , C = great g r o u p , D = s u b g r o u p , E = f a m i l y , F = series, G = m a p p i n g u n i t if a p p r o p r i a t e , a n d e = error. S u b s c r i p t s i n d i c a t e the n u m b e r o f t a x a f o r each c a t e g o r y (e.g., i = 10 f o r the ten soil orders). N o t all c o m b i n a t i o n s o f subscripts are used t o n a m e soils, thus r e q u i r i n g the u n b a l a n c e d analysis o f variance a p p r o a c h 1 9 3 8 Classification S y s t e m Y = ~ + A i + Bij + Cijk + cijkl w h e r e Y = as a b o v e , A = order, B = s u b o r d e r , C = g r e a t g r o u p , e = error. F r e n c h Classification S y s t e m Y = p + A i + Bij + Cijk + D i j k l + cijklm w h e r e Y is as above, A = classe, B = sous-classe, C = g r o u p e , D = s o u s - g r o u p e , a n d e = error. F A O L e g e n d f o r the Soil M a p o f the World Y = p + A i + Bij + eijk w h e r e Y is as a b o v e , A = m a j o r groupings, B = soil units, and e = error. RESULTS AND DISCUSSION Means o f the soil c h e m i c a l p r o p e r t i e s a c c o r d i n g to the f o u r s y s t e m s are p r e s e n t e d in T a b l e s I I - - V . Large d i f f e r e n c e s a m o n g g r e a t g r o u p m e a n s {Table II) i n d i c a t e t h a t this c a t e g o r y o f Soil T a x o n o m y p a r t i t i o n e d certain soil p r o p e r t i e s relatively well. T h e large s t a n d a r d d e v i a t i o n o f the m e a n s o f g r e a t g r o u p s (Table II), h o w e v e r , suggests t h a t t h e g r e a t g r o u p s include soils requiring d i f f e r e n t m a n a g e m e n t practices. T o illustrate f u r t h e r , the ranges in soil p H a n d soluble Si w i t h i n soil g r e a t g r o u p s w e r e as follows: pH Si Hydrandepts 4.6--6.4 0.26--7.2 Dystrandepts 4.3--7.0 0.8--15.6 Eutrandepts 5.8--8.1 2.9--19.3 Vitrandepts 6.3--6.9 4.6--20.9
0.63--268
50.0--1100
Extractable P (NaHCO 3 ) (~g P/g)
P buffering capacity (ug P) 693 (408)
6.83 (8.2)
0.011 (0.01)
692 (158) 2825 (887)
525 (314)
17.7 (37)
0.039 (0.04)
309 (73) 1730 (633)
21.0 (22.3)
15.0 (18.5) 4.34 (5.9) 1.04 (1.2) 0.72 (0.97)
5.43 (4.7)
5.78 (0.65)
Dystrandepts (27)
193 (116)
110 (160)
0,41 (0.93)
<0 (45) 391 (]19)
40.5 (26.0)
29.1 (22.0) 7.51 (4.7) 2.92 (2.7) 0.82 (0.43)
10.9 (6.1)
6.69 (0.68)
Eutrandepts (19)
106 (45)
21.4 (37)
0.017 (0.008)
<0 (1.1) 468 (45)
21.4 (8.3)
17.2 (7.7) 2.86 (1.0) 1.12 (1.3) 0.47 (0.15)
10.3 (6.5)
6.68 (0.23)
Vitrandepts (6)
,1 Means were calculated according to procedures for lognormal distributions as given in Haan, ]977. Arithmetic means are given for soil pH. *~ Numbers in parentheses are number of soils in each great group. ,3 Values <0 indicate that some soils release P to 0.01 M CaC12 solution. ,4 Standard deviations of the respective lognormal distribution (Haan, 1977) are given as estimates of homogeneity of the great groups.
0.001--1.18
P in saturation extract (~g P/ml)
<0--1800 *3 <0--5370
1.03--72.9
4.98 (4.6)
P requirement for 0.02 ~g P/ml (~g P/g) 0.2 ug P/ml (ug P/g)
Sum of cations (Ca,Mg,K,Na) (meq./100 g)
(4.6) (1.5) (0.10) (0.51)
2.02 (2.03) 3.13 1.18 0.23 0.64
0.26--20.9
Silicon in saturation extract (ug Si/ml)
5.38 (0.44) *4
Hydrandepts (28) *2
Great group means .1
Exchangeable cations (meq./] 00 g) calcium 0.25--65.9 magnesium 0.14--17.8 potassium 0.07--6.97 sodium 0.11--8.45
4.3--8.1
Range
Soil pH
Chemical property
Summary of some soil chemical properties of 80 Andepts and means of four Great Groups f r o m the Island of Hawaii
TABLE II
18 T A B L E III M e a n s of soil c h e m i c a l p r o p e r t i e s of 2 g r o u p s of A n d e p t s s e p a r a t e d a c c o r d i n g to the F r e n c h Classification S y s t e m Chemical property
Sols desatur~s (55)*~
Sols satures i25~
Soil pH
5.57 ( 0 . 5 9 ) * :
Silicon in s a t u r a t i o n e x t r a c t (~g Si/ml)
3.76 (4.41
10.6 ((i i
E x c h a n g e a b l e c a t i o n s ( m e q . / 1 0 0 g) calcium magnesium potassium sodium
9.69 2.63 (1.57 0.68
25.9 ( l ~ . 6 J 6.37 (.1.531 2.58 (3.0) 0.73 (O 4
S u m o f c a t i o n s (Ca,Mg,K,Na) ( m e q . / 1 0 0 g) P r e q u i r e m e n t for 0.02 pg P / m l (ng P/g) 0.2 #g P / m l (pg P/g) P in s a t u r a t i o n e x t r a c t (pg P / m l ) 0.5 M N a H C O 3 (~g P/g} P b u f f e r i n g c a p a c i t y (~zg P!
(20) (4.4) (0.7) (0.7)
12.7 ( 1 8 . 5 ) 503 ( 1 3 4 ) 2290 (882) 0 . 0 2 5 (0.04)
11.,l (21.41 606 ( 3 6 9 )
6.69 ((!.601
35.5 ~22.~) < 0 . 0 (31)*~ 4 1 0 (1101 0.2~ (0.82)
91.9(1i:0~ 162 (99~
*~ M e a n s were c a l c u l a t e d a c c o r d i n g to p r o c e d u r e s for l o g n o r m a l d i s t r i b u t i o n s as given by H a a n (19771. T h e a r i t h m e t i c m e a n is given for soil pH. N u m b e r s in p a r e n t h e s e s are the n u m b e r of soils in t h e group. ,2 S t a n d a r d d e v i a t i o n s of t h e respective l o g n o r m a l d i s t r i b u t i o n s (Haan, 1977} are given a,, e s t i m a t e s of h o m o g e n e i t y of t h e taxa. ,3 Values less t h a n 0.0 i n d i c a t e some soils release P to 0.01 M CaCI, solution.
For some purposes, such as growing plants that are sensitive to A1 or Mn, the need for lime almost certainly differs from soil to soil within the great group. Soil pH values less than about 5.2 frequently are associated with excess A1 and Mn accumulation by plants whereas in the range about 5.2 to 5.8 onty Mn is a likely problem {Jones and Fox, 1978). The concentration of Si that separates Si-deficient from Si-sufficient soils is about 1 to 2 mg/1 (Fox et al., 19671. Thus, there is no clear line of demarkation between great groups with respect to Si solubility. Perhaps the lower more detailed categories should partition soil properties more effectively although they do not do so with these soils. Exchangeable sodium was not effectively partitioned by any system as might be expected because it is associated with proximity to the sea. The French system effectively separated the 20 soil series into two taxa, sols satur6s and sols desatur6s (Table III). This system effectively separated softs on the basis of pH, as well it should because the partitioning into two categories is based largely on soil pH (F.H. Beinroth, pers. comm., 1981). Although only two taxa were designated, sizeable differences in means were
5.00 (4.5)
Sum of cations (Ca,Mg,K,Na) (meq./100 g)
7.62 (9.6) 490 (381)
18.2 (39)
0.03 (0.04)
252 (61) 1558 (602)
25.8 (21.1)
15.3 (18.0) 4.10 (5.0) 1.16 (1.4) 0.78 (1.1)
5.30 (4.1)
5.83 (0.71)
Calcimorphic soils (24)
103 (54)
37.4 (77)
0.02 (0.01)
8.0 (10) 400 (20)
20.1 (9.3)
15.8 (8.4) 2.91 (1.0) 1.02 (0.8) 0.47 (0.2)
13.0 (7.1)
6.60 (0.24)
Deep unconsolidated soils (4)
257 (195)
103 (191)
0.33 (0.76)
611 (263)
< 0 ( 2 2 ) *3
39.3 (25.2)
28.5 (21.8) 7.20 (4.1) 2.79 (3.3) 0.77 (0.45)
9.96 (6.2)
6.63 (0.69)
Dark colored soils (22)
,1 Means were calculated according to procedures for lognormal distributions as given by Haan (1977). Arithmetic means are given for soil pH. Numbers in parentheses are the number of soils in each group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977) are given as estimates of homogeneity of the suborders. .3 Values less than 0.0 indicate some soils release P to 0.01 M C a C I 2 solution.
673 (400)
Extractable P (NaHCO3) (pg P/g)
P buffering capacity (ug P)
0.012 (0.02)
682 (150) 2776 (861)
P in saturation extract (~g P/ml)
P requirement for 0.02 #g P/m] (~g P/g) 0.2 ug P/ml (ug P/g)
3.24 1.10 0.25 0.62
Exchangeable cations (meq./100 g) calcium magnesium potassium sodium (4.6) (1.4) (0.12) (0.48)
5.39 (0.43) *~ 2.33 (2.8)
Soil pH
Latosols *~ (30)
Silicon in saturation extract (~g Si/ml)
Chemical property
Means of soil chemical properties of 4 Suborders of Andepts classified according to the 1938 Soil C]assification
TABLE IV
CO
(9.7) (2.5) (0.2) (0.5)
644 (358)
7.33(9.3)
0 .0 1 6 ( 0 .0 2 )
646 (140) 2645(829)
7.13 (8.9)
4.98 1.64 0.28 0.62
2.78 (3.3)
5.42 (0.54) *2
Ochric Andosols (35)*'
535 (356)
20.8 (172)
0.04(0.05)
252 (63) 1652(661)
22.4 (23.7)
16.0 (19) 4.44 (6.0) 1.24 (1.4) 0.81 (1.3)
5.27 (4.5)
5.84 (0.59)
Humic Andosols (20)
169 (109)
100(172)
0.32(0.8)
<0.0 (36) *3 392(108)
36.7 (24.5)
26.5 (20) 6.67 (4.6) 2.58 (2.6) 0.76 (0.4)
11.2 (6.2)
6.68 (0.62)
Mollic Andosols (23)
113 (18.0)
7. 60( 2. 1)
0.012(0.002)
18 (1.0) 607(80)
24.0 (3.4)
19.8 (0.8) 2.94 (1.5) 2.51 (4.9) 0.05 (0.1)
4.96 (0.5)
6.85 (0.07)
Vitric Andosols (2)
*~ Means were calculated according to procedures for lognormal distributions as given by Haan (1977 ). Arithmetic means are given for soil pH. Numbers in parentheses are the number of soils in each group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977) are given as estimates of the soil units. ,3 Values less than 0.0 indicate some soils release P to 0.01 M CaCI~ solution.
P buffering capacity (pg P)
Extractable P (NaHCO 3 ) (ug p/g)
P in saturation extract (ug P/ml)
P requirement for 0.02 ~g P/ml (ug P/g) 0.2 ug P/ml (~g P/g)
Sum of cations (Ca, Mg, K, Na) (meq./100 g)
Exchangeable cations (meq./100 g ) calcium magnesium potassium sodium
Silicon in saturation extract (ug Si/ml)
Soil pH
Chemical property
Means of soil chemical properties of 4 soil units of some Andepts classified by the FAO soil mapping system
TABLE V
2] TABLE VI Means of soil chemical properties of 2 suborders of the proposed Andisol order for Soil Taxonomy Chemical property Soil pH
Ustands (25) .1 6.69 (0.60) *5
Silicon in sat. extract (t~g Si/ml) 10.6 (6.1) Exchangeable cations (meq./100 g) Ca 25.9 (18.6) Mg 6.37 (4.5) K 2.58 (3.0) Na 0.73 (0.4) Sum of cations (meq./100 g) (Ca, Mg, K, Na) 35.5 (22.8) P requirement for 0.02 mg P/1 (~g P/g) <0.0 (31) *3 0.2 mg P/1 (~g P/g) 410 (110) P in sat. extract (ug P/ml) Extractable P (NaHCO3) (ng P/g) P buffer capacity (pg P/g)
0.28 (0.82) 91.9 (170) 162 (99)
Tropands (55) 5.57 (0.59) 3.76 (4.4) 9.69 (20) 2.63 (4.4) 0.57 (0.7) 0.68 (0.7) 12.7 (18.5) 503 (135) 2290 (882) 0.025 (0.04) 11.4 {21.4) 606 (369)
,1 Means were calculated according to procedures for lognormal distributions as given by Haan (1977). The arithmetic mean is given for soil pH. Numbers in parentheses are the number of soils in the group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977 ) are given as estimates of homogeneity of the suborders. ,3 Values less than 0.0 indicate some soils release P to 0.01 M CaCI~ solution. o b t a i n e d for m o s t o t h e r properties. The s t a n d a r d deviations o f the properties were, h o w e v e r , quite large. This indicates t h a t while the m e a n s were far apart, t h e y were n o t precisely e s t i m a t e d and thus overlap in soil p r o p e r t i e s o c c u r r e d a m o n g the taxa. Softs a l m o s t certainly d e f i c i e n t in s o m e n u t r i e n t s were g r o u p e d with softs w h i c h s h o u l d be well-supplied. In the 1 9 3 8 Soil Classification S y s t e m , soil chemical p r o p e r t i e s were m o s t effectively p a r t i t i o n e d at the s u b o r d e r c a t e g o r y and m e a n s are given for the f o u r categories (Table IV). The differentiae for this s e p a r a t i o n were n o t particularly effective on soil pH. D a r k C o l o r e d Softs and D e e p U n c o n s o l i d a t e d Soils h a d similar average pH values whereas P s o r p t i o n (0.2 m g P/l) values were similar for D a r k C o l o r e d Soils and C a l c i m o r p h i c Soils (Table IV). T h e criteria f o r s u b o r d e r designations in the 1 9 3 8 s y s t e m a p p e a r less c o r r e l a t e d with soil chemical p r o p e r t i e s t h a n does Soil T a x o n o m y and the F r e n c h S y s t e m The s y s t e m s with m o s t similarity were F A O soil units derived f r o m the F A O m a p of the w o r l d and Soil T a x o n o m y (Dudal, 1976). In o u r s t u d y , h o w e v e r , s o m e differences were n o t e d . T h e F A O g r o u p i n g was n o t particularly effective in separating soil p H a n d soil Ca (Table V). Soil Mg was separated d i f f e r e n t l y f r o m soil Ca (Table V) w h i c h c o n t r a s t s with Soil T a x o n o m y w h e r e
22 TABLE VII Homogeneity of the various categories of five soil classification systems for soil chemical properties of selected Andepts from the Island of Hawaii as expressed by pooled variances of the taxa for each category Chemical property
Initial Variance variance*~ of map . . ping units (25)*:
Soil T a x o n o m y . . . . . . . . great subfamily group group (13) (4) (9)
FAO Soil Legend soil uml (4)
Soil pH
0.64
0.20
0.33
0.28
0.2b
0.3,1
Silicon in sat. extract (~g Si/ml)
1.12
0.46
0.55
0.50
0.63
0.63
Exchangeable cations (meq./100 g) Ca Mg K Na
2.00 1.50 1.35 0.56
0.67 0.54 0.49
0.90 0.84 0.61 0.55
0.94 0.87 0.60 0.56
0.89 0.77 0.57 0.55
1.0~, 0.94 0.65 0.56
Sum of cations (meq./100 g) (Ca, Mg, K, Na)
1.35
0.43
0.59
0.62
0.57
0.70
P requirement for 0.02 ~g P/ml (~g P/g) 0.2 t~g P/ml (ug P/g)
0.14 0.26
0.068 0.10
0.07 0.10
0.07 0.10
0.07 0.10
0.07 0.10
P in sat. extract (pg P/ml)
2.41
1.00
1.25
1.22
1.12
] .54
0.58
Extractable P (NaHCO~) (ug P/g)
2.20
1.13
1.29
1.24
1.19
1.34
P buffering capacity (~g P/g)
0.55
0.28
0.32
0.30
0.26
0.34
, l Initial variance is the variance of 80 samples corrected for the mean. ,2 Variance of mapping units was the minimum variance (most homogeneous grouping) against which the categories of the various systems may be compared. Numbers in parenthese indicate the number of taxa per category for the various systems. h i g h soil M g a c c o m p a n i e s h i g h s o i l Ca. T h i s r e f l e c t s a c o n t r a s t in t h e d i f f e r e n t i a e b e t w e e n t h e t w o s c h e m e s f o r t h e l i m i t e d g r o u p o f s o i l s in t h i s s t u d y . For the proposed order of Andisols {Smith, 1978) the greatest paritioning o c c u r r e d a t t h e s u b o r d e r l e v e l . T h e s o i l s r e p r e s e n t e d in t h i s s t u d y p e r t a i n e d to the two suborders Ustands and Tropands. This division corresponded exactl y w i t h t h a t o f t h e F r e n c h C l a s s i f i c a t i o n (sols satur~ and sols desaturS), respectively (Tables III and VI). In addition, the four great groups of Andisols c o m p a r e d e x a c t l y w i t h t h e n u m b e r o f soils a n d a v e r a g e soil c h e m i c a l p r o p e r t i e s o f t h e f o u r g r e a t g r o u p s o f t h e A n d e p t s . I n t h i s l i m i t e d s a m p l e o f soils all H y d r a n d e p t s w e r e H y d r o t r 0 p a n d s (n = 2 8 ) , all D y s t r a n d e p t s w e r e a l s o H a p l o t r o p a n d s (n = 2 7 ) , V i t r a n d e p t s w e r e V i t r u s t a n d s (n = 6), a n d E u t r a n -
23
French Classification
1938 System
groupe (2)
sousgroupe (5)
order (3)
suborder (4)
great group (6)
suborder (2)
great group (4)
subgroup (9)
family (13 )
0.35
0.35
0.63
0.36
0.33
0.35
0.33
0.31
0.32
0.73
0.75
1.06
0.58
0.57
0.73
0.55
0.55
0.49
1.40 1.10 0.90 0.55
1.42 1.13 0.90 0.56
1.94 1.51 1.36 0.57
0.88 0.73 0.70 0.56
0.89 0.72 0.69 0.56
1.40 1.10 0.90 0.55
0.90 0.84 0.61 0.55
0.91 0.90 0.61 0.58
0.90 0.82 0.62 0.56
0.92
0.93
1.33
0.56
0.57
0.92
0.59
0.61
0.60
0.08 0.12
0.08 0.12
0.14 0.25
0.08 0.12
0.08 0.12
0.08 0.12
0.07 0.10
0.06 0.10
0.07 0.10
1.76
1.79
2.46
1.32
1.31
1.76
1.25
1.16
1.13
Soil Taxonomy (with proposed Andisol order)
1.48
1.48
2.23
1.48
1.48
1.48
1.29
1.19
1.20
0.34
0.32
0.57
0.41
0.40
0.34
0.32
0.30
0.26
d e p t s w e r e H a p l u s t a n d s (n = 19). As i n d i c a t e d i n T a b l e V I , m e a n s o f m o s t soil c h e m i c a l p r o p e r t i e s w e r e q u i t e d i f f e r e n t a m o n g t h e p r o p o s e d s u b o r d e r s . T h e s t a n d a r d d e v i a t i o n s w e r e also large, h o w e v e r , i n d i c a t i n g c o n s i d e r a b l e overlap in p r o p e r t i e s for the t w o t a x a U s t a n d s a n d T r o p a n d s . F o r t h e s p e c i f i c p u r p o s e o f g r o u p i n g soils a c c o r d i n g t o n u t r i e n t m a n a g e ment requirements, additional criteria based on nutrient supplying characteristics o f t h e softs a p p e a r n e c e s s a r y .
Homogeneity of the taxa A n o t h e r m e a s u r e o f t h e e f f e c t i v e n e s s o f c l a s s i f i c a t i o n s c h e m e s is t h e p r e c i -
24
O. 7--
P 0 O L E O V R R I R N C E F g R P H
0.60.50.40.30.2O. 1O.O-
I
NO. LEGENO:
. . . . . . . . . . . . . . . . .
5
0
T
OF
TRXR
IN ERCH
* • m _193B ~-~--~ R N D I S O L ~-4~--~ F R E N C H
SYSTEM
T.
. . . . . . . . . . . . . . . . . .
lO
.
.
.
.
.
~ - T
15
20
CRTEGORT *-x-~ RNOEPT ~-4~-~ FRO
Fig. 1. Homogeneity of soil pH within soil groupings, expressed as pooled variance, of 80 Andepts classified according to Soil Taxonomy, Soil Taxonomy with the proposed order Andisols, the French, FAO, and 1938 systems. 0.30P {3 0 L E 0 V R R I R N c E F 0 R
0.25-
0.20-
O. iS-
O. IO-
O. O5-
P 0.000 NI~.
LEGENO:
SYSTEM
OF
1
I
5
I0 TRXQ
IN ERCH
• ~ _1938 ~-~-~ RNOISOL 4,--e-~ F R E N C H
I---
15
I"
20
CRTEDORY ~-x-~ RNOEPT 8-~a-~ FRO
25
sion within the soil taxa which result from classification (Cline, 1949; Webster and Beckett, 1968). Such precision is a comprehensive measure of the ability of the system to group the property in question. The precision associated with each soil property mean reported in Tables II--VI is represented in Table VII and Figs. I and 2 as the pooled variances. For example, the pooled variance of soil pH for the 4 taxa of Soil T a x o n o m y , FAO soil legend, and the 1938 systems are respectively 0.33, 0.34, and 0.36 (Fig. 1). The two taxa of the French System gave precision estimates of 0.35. In this case, all systems gave remarkably similar estimates of precision for soil pH. The 80 soils in this study were placed in all three orders of the 1938 system. This grouping was almost totally ineffective, however, as shown by the lack of improved precision (reduced pooled variance). For example, sample variance for soil pH was 0.64 and after placing the 80 samples into 3 groups of Zonal, Intrazonal, and Azonal soils the pooled variance was still 0.63 which indicates no substantial improvement in homogeneity. This category also was ineffective for all other soil chemical properties examined in this study (Table VII). Plots of the estimates of precision (pooled variance) against the number of taxa in each category also demonstrate which differentiae were most effective (Figs. 1 and 2). The differentiae which separate the 80 samples into 2 groups accounted for the most variation in the French System and the proposed order Andisols, whereas the differentiae which separate the samples into 4 groups were most effective in the Soil T a x o n o m y 1938 System and FAO legend. Further partitioning by any system was not effective (Table VII), indicating that the criteria used for the additional partitioning were not well correlated with the chemical properties of these soils. Why each system had one category which was especially effective in grouping the soil properties is not clear. This result emphasizes the need to examine the differentiae used to group soils and the correlations among such criteria and accessory soil properties. With the exception of Soil T a x o n o m y , the precise differentiae used by the various systems are n o t apparent. The differentiae that the systems use must be more precisely known in order to properly evaluate and suggest improvements. The results of this study also suggest that the application of criteria at the lower categories may be far less effective than is generally supposed if such criteria are highly correlated with criteria applied at higher categories. Rapid assessment of classification system performance permits comparison of numerous classification systems including trial systems or those designed for specialized uses. This in turn should p r o m o t e incorporation of improvements and development of systems to answer special needs such as those of grouping soils and climates in order to match crop requirements. Fig. 2. Homogeneity of P sorption (P required at 0.02 mg P/l) within soil groupings, expressed as pooled variance, of 80 Andepts classified according to Soil Taxonomy, Soil Taxonomy with the proposed order Andisols, the French, FAO, and 1938 systems.
26 REFERENCES Barr, A.J., Goodnight, J.H., Sail, J.P., Blair, W.H. and Chilko, D.M., 1979. SAS User's Guide. SAS Institute, Inc., Raleigh, NC. Beinroth, F.H., Ikawa, H. and Uehara, G., 1979. Classification of the Soil Series of the State of Hawaii in four systems: a guide to correlate soils. Tech. Rep. 2, Benchmark Soils Project, Univ. of Hawaii, and Univ. of Puerto Rico. Cline, M.G., 1949. Basic principles of soil classification. Soil Sci., 67: 81--91. Cline, M.G., 1955. Soil survey of the territory of Hawaii. Soil Surv. Ser. 1939, No. 25, Soil Conservation Service, USDA, Washington, D.C. Dudal, R., 1976. Inventory of the major soils of the world with special reference to mineral stress hazards. In: M.J. Wright (Editor), Plant Adaptation to Mineral Stress in Problem Soils. Proceedings of a Workshop at the National Agricultural Library, Beltsville, Nov. 1976. Agency for International Development, Washington, D.C. Fox, R.L., Silva, J.A., Younge, O.R., Plucknett, D.L. and Sherman, G.D., 1967. Soil and plant silicon and silicate response by sugar cane. Soil Sci. Soc. Am. Proc., 31: 775- 779 Haan, C.T., 1977. Statistical Methods in Hydrology. Iowa State University Press, Ames. Iowa. Jones, J.P. and Fox, R.L., 1978. Phosphorus nutrition of plants influenced by manganese and aluminum uptake from an oxisol. Soil Sci., 126: 230--236. Leamy, M.L., 1982. Some implications of testing the Andisol proposal. Int. Soil Sci. Soc. Congr., 12th, New Delhi, Abstract. Recel, M., Ikawa, H. and Uehara, G., 1981. The classification of the Andepts of Hawaii according to the proposed key to Andisols. Paper presented to the 4th International Soil Classification Workshop, Rwanda, June 2--12, 1981. Sato, H.H., Ikeda, W., Paeth, R., Smythe, R. and Takehiro, M., 1973. Soil Survey of the Island of Hawaii. USDA-SCS-Univ. of Hawaii Agric. Expt. Sta., Honolulu, Hawaii. Smith, G.D., 1978. Preliminary proposal for reclassification of Andepts and some Andic subgroups. Unpublished manuscript. Soil Survey Staff, 1975. Soil Taxonomy: a Basic System of Soil Classification for Making and Interpreting Soil Surveys. Soil Conservation Service, USDA Agriculture Handbook No. 436, U.S. Government Printing Office, Washington, D.C. Webster, R. and Beckett, P.H.T., 1968. Quality and usefulness of soil maps. Nature (London), 219: 680--682. Yost, R.S. and Fox, R.L., 1981. Partitioning variation in soil chemical properties of some Andepts using Soil Taxonomy. Soil Sci. Soc. Am. J., 45: 373--377.
13
Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
PARTITIONING VARIATION ANDEPTS-- A COMPARISON
IN CHEMICAL PROPERTIES OF SOME O F C L A S S I F I C A T I O N S Y S T E M S .1
R.S. YOST and R.L. FOX
Department of Agronomy and Soil Science, University of Hawaii, Honolulu, HI 96822 (U.S.A.) (Received October 10, 1981; accepted after revision June 26, 1982)
ABSTRACT Yost, R.S. and Fox, R.L., 1983. Partitioning variation in chemical properties of some andepts -- A comparison of classification systems. Geoderma, 2 9 : 1 3 - - 2 6 . One purpose of classification systems is to group objects with similar properties so that meaningful generalizations can be made concerning their properties, behavior and potential use. It has been difficult to measure the success of such groupings. Similarly it has been difficult to determine how well soil classification systems group properties different from the criteria upon which the systems are based. Eighty soil samples (0--15 cm depth) of the Andept suborder were collected from the Island of Hawaii. Soil chemical properties (pH, exchangeable cations, extractable P, P sorption, and silicon) were measured. The 80 soils were grouped according to Soil Taxonomy, the proposed Andisol order of Soil Taxonomy, the FAO Legend for the Soil Map of the World, the French Classification System, and the 1938 Soil Classification System. Each system's effectiveness in grouping was compared by using regression techniques based on the statistical model of the classification scheme. Each system had a specific category which most effectively grouped soils with similar properties. The most effective category (that which decreased the pooled variance most) was the great group level of Soil Taxonomy, the suborder level of the proposed Andisol order of Soil Taxonomy, the Groupe level of the French System, and the suborder level of the 1938 System. In considering the FAO legend, only soil units were examined. These effectively separated variation in most soil properties in this group of soils. As indicated by the greatest precision (smallest pooled variance) Soil T a x o n o m y was effective in grouping all soil chemical properties except Na, whereas grouping 80 soils into 3 orders of the 1938 System did not increase homogeneity within groups. The Groupe category of the French System which formed the 2 taxa of saturO and desatur$ was effective for most properties, especially soil pH. In our case the two Andisol suborders were identical within the Groupe level of the French System (satur~ and desatur~), whereas the four taxa of the Andept great group category corresponded with four great groups of the proposed Andisol order. Lower categories of Soil Taxonomy, the 1938 System, or the French System did little to increase precision, suggesting that differentiae of the lower highly defined categories studied here were correlated with those of more general higher categories. .1 Journal Series no. 2614 of the Hawaii Agric. Exp. Stn. This work was supported by a 211(d) Basic Grant (AID/CSD-2833). All reported opinions, conclusions, and recommendations are those of the authors and not those of the funding agency or the U.S. Government.
0016-7061/83/0000--0000/$03.00
© 1983 Elsevier Scientific Publishing Company
14 INTRODUCTION One of the purposes of classification is to group items that have similar properties so that meaningful general statements can be made about those properties and potential use. Such groupings of soils improve the understanding and use of soil resources. It is sometimes difficult to quantify the success of such groupings, or to quantitatively compare properties n o t expressly col~ sidered in soil classification systems. The criteria for Andepts (Andisols), for example, include consideration of subhorizons. For specific purposes such as crop production, the surface soil properties are more influential than subsoil properties. It can be useful to determine what inferences of surface properties are given by systems based, in part, on subsurface horizons. Similarly one could compare how well classification systems group crop yields, soil water properties, microbiological populations, disease incidence, etc. All of which are not directly used as classification criteria. Soil classification schemes can be compared by examining the way partitioning of total variation in selected soil properties has been effected in a group of soils (Yost and Fox, 1981). Effective soil classification schemes should designate homogeneous groupings of soils for one or more properties. Mean values of such a soil property within each group may suggest management needs for soils of t h a t group. Also, the more detailed, lower level taxa should be more homogeneous than higher level categories and this should be indicated by smaller within-group variances. These criteria were used to compare Soil T a x o n o m y with other soil classification systems in partitioning variation in soil chemical properties of certain Andepts. MATERIALS AND METHODS Soil samples were collected along transects on the Island of Hawaii. Samph~ collection procedures were described by ~ ost and Fox (1981). Data reported here represent samples from the 0- to 15-cm depth. Sample locations, 164 in number, were recorded from published soil maps of the Soil Survey of the Island of Hawaii (Sato et al., 1973). Of the soils sampled, 20 soil series were in the Andept suborder of Soil T a x o n o m y (Soil Survey Staff, 1975). The 20 series (Table I) were placed into other classification systems as suggested by Beinroth et al. (1979). Classification of the 20 series according to the proposed Andisol order of Soil T a x o n o m y (Smith, 1978) followed the work of Recel et al. (1981). The soil order Andisol was proposed to consider or improve consideration of soil moisture regimes and water retention properties, variable charge properties, particle size and mineralogy. Proposed suborders include aquands, borands, xerands, ustands, tropands, and udands. Softs of this study were either ustands or tropands. Further modifications have been discussed by Leamy {1982). The soil series and mapping unit categories were included in computations
15 TABLEI Soil series names and soil family designations of 80 samples of Andepts used in this study Series
Family
Akaka Apakuie Hanipoe Hilo Honokaa Kaiwiki Kealakekua Kikoni Kilohana Kukaiau Laumaia Maile Naalehu Olaa Pakini Palapalai Punohu Puu 0o Puu Pa Waimea
Thixotropic, isomesic, Typic Hydrandept Medial, isomesic, Umbrie Vitrandept Medial, isomesic, Typic Dystrandept Thixotropic, isohyperthermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Thixotropic, isothermic, Typic Hydrandept Medial, isothermie, Typic Eutrandept Ashy, isomesic, Mollic Vitrandept Thixotropic, isothermic, Hydric Dystrandept Medial, isomesic, Typic Dystrandept Thixotropic, isomesic, Hydric Dystrandept Medial, isohyperthermic, Typic Eutrandept Thixotropic, over fragmental, isohyperthermic, Typic Hydrandept Medial, isohyperthermic, Entic Eutrandept Medial, isothermic, Typic Entrandept Thixotropic, isomesic, Hydric Dystrandept Thixotropic, isomesic, Hydric Dystrandept Medial-skeletal, isothermic, Ustollic Eutrandept Medial, isothermic, Typic Eutrandept
of pooled variance, although neither the French System nor the FAO legend have these categories. Similarly, the mapping unit was included in the Soil T a x o n o m y model while recognizing t ha t this category is n o t part of the system. This addition was useful in demonstrating the effectiveness of the categories immediately above the series category in both the FAO legend (soil units) and the French system. The 1938 Soil Classification System r e p o r t e d here was that applied to Hawaii by Cline (1955) and includes the suborder "D eep Unconsolidated Soils" n o t f o u n d in the original 1938 system. This system is now archaic and was included only for comparison. Means are given for the category of each system that account ed for the most variation in soil chemical properties. Statistical calculations were made using the Statistical Analysis System (Barr et al., 1979). Normality of the data was analyzed by the KolmogorovSmirnov statistic. The general linear models procedure (GLM) was used for c o m p u t i n g the unbalanced analysis of variance. Estimates of precision for each t a x o n o m i c category (pooled variance) were obtained by regression soil properties on d u m m y variables t hat assumed unique values for each taxa of the category. Because the statistical models of these systems are all hierarchical, the residual mean square of the regression of soil properties on individual categories provides a pooled estimate of the variances within
16 the c a t e g o r y taxa. F u r t h e r testing is possible b y d e t e r m i n i n g if the individual t a x a variances are h o m o g e n e o u s a n d if d i s t r i b u t i o n s are n o r m a l . Statistical m o d e l s f o r the various classification s y s t e m s follow. Soil T a x o n o m y Y = p + A i + Bij + Cijk + D i j k l + E i j k l m + Fijklm n + Gijklrn n o + eijktm nop w h e r e Y is t h e value o f t h e soil p r o p e r t y , A = order, B = s u b o r d e r , C = great g r o u p , D = s u b g r o u p , E = f a m i l y , F = series, G = m a p p i n g u n i t if a p p r o p r i a t e , a n d e = error. S u b s c r i p t s i n d i c a t e the n u m b e r o f t a x a f o r each c a t e g o r y (e.g., i = 10 f o r the ten soil orders). N o t all c o m b i n a t i o n s o f subscripts are used t o n a m e soils, thus r e q u i r i n g the u n b a l a n c e d analysis o f variance a p p r o a c h 1 9 3 8 Classification S y s t e m Y = ~ + A i + Bij + Cijk + cijkl w h e r e Y = as a b o v e , A = order, B = s u b o r d e r , C = g r e a t g r o u p , e = error. F r e n c h Classification S y s t e m Y = p + A i + Bij + Cijk + D i j k l + cijklm w h e r e Y is as above, A = classe, B = sous-classe, C = g r o u p e , D = s o u s - g r o u p e , a n d e = error. F A O L e g e n d f o r the Soil M a p o f the World Y = p + A i + Bij + eijk w h e r e Y is as a b o v e , A = m a j o r groupings, B = soil units, and e = error. RESULTS AND DISCUSSION Means o f the soil c h e m i c a l p r o p e r t i e s a c c o r d i n g to the f o u r s y s t e m s are p r e s e n t e d in T a b l e s I I - - V . Large d i f f e r e n c e s a m o n g g r e a t g r o u p m e a n s {Table II) i n d i c a t e t h a t this c a t e g o r y o f Soil T a x o n o m y p a r t i t i o n e d certain soil p r o p e r t i e s relatively well. T h e large s t a n d a r d d e v i a t i o n o f the m e a n s o f g r e a t g r o u p s (Table II), h o w e v e r , suggests t h a t t h e g r e a t g r o u p s include soils requiring d i f f e r e n t m a n a g e m e n t practices. T o illustrate f u r t h e r , the ranges in soil p H a n d soluble Si w i t h i n soil g r e a t g r o u p s w e r e as follows: pH Si Hydrandepts 4.6--6.4 0.26--7.2 Dystrandepts 4.3--7.0 0.8--15.6 Eutrandepts 5.8--8.1 2.9--19.3 Vitrandepts 6.3--6.9 4.6--20.9
0.63--268
50.0--1100
Extractable P (NaHCO 3 ) (~g P/g)
P buffering capacity (ug P) 693 (408)
6.83 (8.2)
0.011 (0.01)
692 (158) 2825 (887)
525 (314)
17.7 (37)
0.039 (0.04)
309 (73) 1730 (633)
21.0 (22.3)
15.0 (18.5) 4.34 (5.9) 1.04 (1.2) 0.72 (0.97)
5.43 (4.7)
5.78 (0.65)
Dystrandepts (27)
193 (116)
110 (160)
0,41 (0.93)
<0 (45) 391 (]19)
40.5 (26.0)
29.1 (22.0) 7.51 (4.7) 2.92 (2.7) 0.82 (0.43)
10.9 (6.1)
6.69 (0.68)
Eutrandepts (19)
106 (45)
21.4 (37)
0.017 (0.008)
<0 (1.1) 468 (45)
21.4 (8.3)
17.2 (7.7) 2.86 (1.0) 1.12 (1.3) 0.47 (0.15)
10.3 (6.5)
6.68 (0.23)
Vitrandepts (6)
,1 Means were calculated according to procedures for lognormal distributions as given in Haan, ]977. Arithmetic means are given for soil pH. *~ Numbers in parentheses are number of soils in each great group. ,3 Values <0 indicate that some soils release P to 0.01 M CaC12 solution. ,4 Standard deviations of the respective lognormal distribution (Haan, 1977) are given as estimates of homogeneity of the great groups.
0.001--1.18
P in saturation extract (~g P/ml)
<0--1800 *3 <0--5370
1.03--72.9
4.98 (4.6)
P requirement for 0.02 ~g P/ml (~g P/g) 0.2 ug P/ml (ug P/g)
Sum of cations (Ca,Mg,K,Na) (meq./100 g)
(4.6) (1.5) (0.10) (0.51)
2.02 (2.03) 3.13 1.18 0.23 0.64
0.26--20.9
Silicon in saturation extract (ug Si/ml)
5.38 (0.44) *4
Hydrandepts (28) *2
Great group means .1
Exchangeable cations (meq./] 00 g) calcium 0.25--65.9 magnesium 0.14--17.8 potassium 0.07--6.97 sodium 0.11--8.45
4.3--8.1
Range
Soil pH
Chemical property
Summary of some soil chemical properties of 80 Andepts and means of four Great Groups f r o m the Island of Hawaii
TABLE II
18 T A B L E III M e a n s of soil c h e m i c a l p r o p e r t i e s of 2 g r o u p s of A n d e p t s s e p a r a t e d a c c o r d i n g to the F r e n c h Classification S y s t e m Chemical property
Sols desatur~s (55)*~
Sols satures i25~
Soil pH
5.57 ( 0 . 5 9 ) * :
Silicon in s a t u r a t i o n e x t r a c t (~g Si/ml)
3.76 (4.41
10.6 ((i i
E x c h a n g e a b l e c a t i o n s ( m e q . / 1 0 0 g) calcium magnesium potassium sodium
9.69 2.63 (1.57 0.68
25.9 ( l ~ . 6 J 6.37 (.1.531 2.58 (3.0) 0.73 (O 4
S u m o f c a t i o n s (Ca,Mg,K,Na) ( m e q . / 1 0 0 g) P r e q u i r e m e n t for 0.02 pg P / m l (ng P/g) 0.2 #g P / m l (pg P/g) P in s a t u r a t i o n e x t r a c t (pg P / m l ) 0.5 M N a H C O 3 (~g P/g} P b u f f e r i n g c a p a c i t y (~zg P!
(20) (4.4) (0.7) (0.7)
12.7 ( 1 8 . 5 ) 503 ( 1 3 4 ) 2290 (882) 0 . 0 2 5 (0.04)
11.,l (21.41 606 ( 3 6 9 )
6.69 ((!.601
35.5 ~22.~) < 0 . 0 (31)*~ 4 1 0 (1101 0.2~ (0.82)
91.9(1i:0~ 162 (99~
*~ M e a n s were c a l c u l a t e d a c c o r d i n g to p r o c e d u r e s for l o g n o r m a l d i s t r i b u t i o n s as given by H a a n (19771. T h e a r i t h m e t i c m e a n is given for soil pH. N u m b e r s in p a r e n t h e s e s are the n u m b e r of soils in t h e group. ,2 S t a n d a r d d e v i a t i o n s of t h e respective l o g n o r m a l d i s t r i b u t i o n s (Haan, 1977} are given a,, e s t i m a t e s of h o m o g e n e i t y of t h e taxa. ,3 Values less t h a n 0.0 i n d i c a t e some soils release P to 0.01 M CaCI, solution.
For some purposes, such as growing plants that are sensitive to A1 or Mn, the need for lime almost certainly differs from soil to soil within the great group. Soil pH values less than about 5.2 frequently are associated with excess A1 and Mn accumulation by plants whereas in the range about 5.2 to 5.8 onty Mn is a likely problem {Jones and Fox, 1978). The concentration of Si that separates Si-deficient from Si-sufficient soils is about 1 to 2 mg/1 (Fox et al., 19671. Thus, there is no clear line of demarkation between great groups with respect to Si solubility. Perhaps the lower more detailed categories should partition soil properties more effectively although they do not do so with these soils. Exchangeable sodium was not effectively partitioned by any system as might be expected because it is associated with proximity to the sea. The French system effectively separated the 20 soil series into two taxa, sols satur6s and sols desatur6s (Table III). This system effectively separated softs on the basis of pH, as well it should because the partitioning into two categories is based largely on soil pH (F.H. Beinroth, pers. comm., 1981). Although only two taxa were designated, sizeable differences in means were
5.00 (4.5)
Sum of cations (Ca,Mg,K,Na) (meq./100 g)
7.62 (9.6) 490 (381)
18.2 (39)
0.03 (0.04)
252 (61) 1558 (602)
25.8 (21.1)
15.3 (18.0) 4.10 (5.0) 1.16 (1.4) 0.78 (1.1)
5.30 (4.1)
5.83 (0.71)
Calcimorphic soils (24)
103 (54)
37.4 (77)
0.02 (0.01)
8.0 (10) 400 (20)
20.1 (9.3)
15.8 (8.4) 2.91 (1.0) 1.02 (0.8) 0.47 (0.2)
13.0 (7.1)
6.60 (0.24)
Deep unconsolidated soils (4)
257 (195)
103 (191)
0.33 (0.76)
611 (263)
< 0 ( 2 2 ) *3
39.3 (25.2)
28.5 (21.8) 7.20 (4.1) 2.79 (3.3) 0.77 (0.45)
9.96 (6.2)
6.63 (0.69)
Dark colored soils (22)
,1 Means were calculated according to procedures for lognormal distributions as given by Haan (1977). Arithmetic means are given for soil pH. Numbers in parentheses are the number of soils in each group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977) are given as estimates of homogeneity of the suborders. .3 Values less than 0.0 indicate some soils release P to 0.01 M C a C I 2 solution.
673 (400)
Extractable P (NaHCO3) (pg P/g)
P buffering capacity (ug P)
0.012 (0.02)
682 (150) 2776 (861)
P in saturation extract (~g P/ml)
P requirement for 0.02 #g P/m] (~g P/g) 0.2 ug P/ml (ug P/g)
3.24 1.10 0.25 0.62
Exchangeable cations (meq./100 g) calcium magnesium potassium sodium (4.6) (1.4) (0.12) (0.48)
5.39 (0.43) *~ 2.33 (2.8)
Soil pH
Latosols *~ (30)
Silicon in saturation extract (~g Si/ml)
Chemical property
Means of soil chemical properties of 4 Suborders of Andepts classified according to the 1938 Soil C]assification
TABLE IV
CO
(9.7) (2.5) (0.2) (0.5)
644 (358)
7.33(9.3)
0 .0 1 6 ( 0 .0 2 )
646 (140) 2645(829)
7.13 (8.9)
4.98 1.64 0.28 0.62
2.78 (3.3)
5.42 (0.54) *2
Ochric Andosols (35)*'
535 (356)
20.8 (172)
0.04(0.05)
252 (63) 1652(661)
22.4 (23.7)
16.0 (19) 4.44 (6.0) 1.24 (1.4) 0.81 (1.3)
5.27 (4.5)
5.84 (0.59)
Humic Andosols (20)
169 (109)
100(172)
0.32(0.8)
<0.0 (36) *3 392(108)
36.7 (24.5)
26.5 (20) 6.67 (4.6) 2.58 (2.6) 0.76 (0.4)
11.2 (6.2)
6.68 (0.62)
Mollic Andosols (23)
113 (18.0)
7. 60( 2. 1)
0.012(0.002)
18 (1.0) 607(80)
24.0 (3.4)
19.8 (0.8) 2.94 (1.5) 2.51 (4.9) 0.05 (0.1)
4.96 (0.5)
6.85 (0.07)
Vitric Andosols (2)
*~ Means were calculated according to procedures for lognormal distributions as given by Haan (1977 ). Arithmetic means are given for soil pH. Numbers in parentheses are the number of soils in each group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977) are given as estimates of the soil units. ,3 Values less than 0.0 indicate some soils release P to 0.01 M CaCI~ solution.
P buffering capacity (pg P)
Extractable P (NaHCO 3 ) (ug p/g)
P in saturation extract (ug P/ml)
P requirement for 0.02 ~g P/ml (ug P/g) 0.2 ug P/ml (~g P/g)
Sum of cations (Ca, Mg, K, Na) (meq./100 g)
Exchangeable cations (meq./100 g ) calcium magnesium potassium sodium
Silicon in saturation extract (ug Si/ml)
Soil pH
Chemical property
Means of soil chemical properties of 4 soil units of some Andepts classified by the FAO soil mapping system
TABLE V
2] TABLE VI Means of soil chemical properties of 2 suborders of the proposed Andisol order for Soil Taxonomy Chemical property Soil pH
Ustands (25) .1 6.69 (0.60) *5
Silicon in sat. extract (t~g Si/ml) 10.6 (6.1) Exchangeable cations (meq./100 g) Ca 25.9 (18.6) Mg 6.37 (4.5) K 2.58 (3.0) Na 0.73 (0.4) Sum of cations (meq./100 g) (Ca, Mg, K, Na) 35.5 (22.8) P requirement for 0.02 mg P/1 (~g P/g) <0.0 (31) *3 0.2 mg P/1 (~g P/g) 410 (110) P in sat. extract (ug P/ml) Extractable P (NaHCO3) (ng P/g) P buffer capacity (pg P/g)
0.28 (0.82) 91.9 (170) 162 (99)
Tropands (55) 5.57 (0.59) 3.76 (4.4) 9.69 (20) 2.63 (4.4) 0.57 (0.7) 0.68 (0.7) 12.7 (18.5) 503 (135) 2290 (882) 0.025 (0.04) 11.4 {21.4) 606 (369)
,1 Means were calculated according to procedures for lognormal distributions as given by Haan (1977). The arithmetic mean is given for soil pH. Numbers in parentheses are the number of soils in the group. ,2 Standard deviations of the respective lognormal distributions (Haan, 1977 ) are given as estimates of homogeneity of the suborders. ,3 Values less than 0.0 indicate some soils release P to 0.01 M CaCI~ solution. o b t a i n e d for m o s t o t h e r properties. The s t a n d a r d deviations o f the properties were, h o w e v e r , quite large. This indicates t h a t while the m e a n s were far apart, t h e y were n o t precisely e s t i m a t e d and thus overlap in soil p r o p e r t i e s o c c u r r e d a m o n g the taxa. Softs a l m o s t certainly d e f i c i e n t in s o m e n u t r i e n t s were g r o u p e d with softs w h i c h s h o u l d be well-supplied. In the 1 9 3 8 Soil Classification S y s t e m , soil chemical p r o p e r t i e s were m o s t effectively p a r t i t i o n e d at the s u b o r d e r c a t e g o r y and m e a n s are given for the f o u r categories (Table IV). The differentiae for this s e p a r a t i o n were n o t particularly effective on soil pH. D a r k C o l o r e d Softs and D e e p U n c o n s o l i d a t e d Soils h a d similar average pH values whereas P s o r p t i o n (0.2 m g P/l) values were similar for D a r k C o l o r e d Soils and C a l c i m o r p h i c Soils (Table IV). T h e criteria f o r s u b o r d e r designations in the 1 9 3 8 s y s t e m a p p e a r less c o r r e l a t e d with soil chemical p r o p e r t i e s t h a n does Soil T a x o n o m y and the F r e n c h S y s t e m The s y s t e m s with m o s t similarity were F A O soil units derived f r o m the F A O m a p of the w o r l d and Soil T a x o n o m y (Dudal, 1976). In o u r s t u d y , h o w e v e r , s o m e differences were n o t e d . T h e F A O g r o u p i n g was n o t particularly effective in separating soil p H a n d soil Ca (Table V). Soil Mg was separated d i f f e r e n t l y f r o m soil Ca (Table V) w h i c h c o n t r a s t s with Soil T a x o n o m y w h e r e
22 TABLE VII Homogeneity of the various categories of five soil classification systems for soil chemical properties of selected Andepts from the Island of Hawaii as expressed by pooled variances of the taxa for each category Chemical property
Initial Variance variance*~ of map . . ping units (25)*:
Soil T a x o n o m y . . . . . . . . great subfamily group group (13) (4) (9)
FAO Soil Legend soil uml (4)
Soil pH
0.64
0.20
0.33
0.28
0.2b
0.3,1
Silicon in sat. extract (~g Si/ml)
1.12
0.46
0.55
0.50
0.63
0.63
Exchangeable cations (meq./100 g) Ca Mg K Na
2.00 1.50 1.35 0.56
0.67 0.54 0.49
0.90 0.84 0.61 0.55
0.94 0.87 0.60 0.56
0.89 0.77 0.57 0.55
1.0~, 0.94 0.65 0.56
Sum of cations (meq./100 g) (Ca, Mg, K, Na)
1.35
0.43
0.59
0.62
0.57
0.70
P requirement for 0.02 ~g P/ml (~g P/g) 0.2 t~g P/ml (ug P/g)
0.14 0.26
0.068 0.10
0.07 0.10
0.07 0.10
0.07 0.10
0.07 0.10
P in sat. extract (pg P/ml)
2.41
1.00
1.25
1.22
1.12
] .54
0.58
Extractable P (NaHCO~) (ug P/g)
2.20
1.13
1.29
1.24
1.19
1.34
P buffering capacity (~g P/g)
0.55
0.28
0.32
0.30
0.26
0.34
, l Initial variance is the variance of 80 samples corrected for the mean. ,2 Variance of mapping units was the minimum variance (most homogeneous grouping) against which the categories of the various systems may be compared. Numbers in parenthese indicate the number of taxa per category for the various systems. h i g h soil M g a c c o m p a n i e s h i g h s o i l Ca. T h i s r e f l e c t s a c o n t r a s t in t h e d i f f e r e n t i a e b e t w e e n t h e t w o s c h e m e s f o r t h e l i m i t e d g r o u p o f s o i l s in t h i s s t u d y . For the proposed order of Andisols {Smith, 1978) the greatest paritioning o c c u r r e d a t t h e s u b o r d e r l e v e l . T h e s o i l s r e p r e s e n t e d in t h i s s t u d y p e r t a i n e d to the two suborders Ustands and Tropands. This division corresponded exactl y w i t h t h a t o f t h e F r e n c h C l a s s i f i c a t i o n (sols satur~ and sols desaturS), respectively (Tables III and VI). In addition, the four great groups of Andisols c o m p a r e d e x a c t l y w i t h t h e n u m b e r o f soils a n d a v e r a g e soil c h e m i c a l p r o p e r t i e s o f t h e f o u r g r e a t g r o u p s o f t h e A n d e p t s . I n t h i s l i m i t e d s a m p l e o f soils all H y d r a n d e p t s w e r e H y d r o t r 0 p a n d s (n = 2 8 ) , all D y s t r a n d e p t s w e r e a l s o H a p l o t r o p a n d s (n = 2 7 ) , V i t r a n d e p t s w e r e V i t r u s t a n d s (n = 6), a n d E u t r a n -
23
French Classification
1938 System
groupe (2)
sousgroupe (5)
order (3)
suborder (4)
great group (6)
suborder (2)
great group (4)
subgroup (9)
family (13 )
0.35
0.35
0.63
0.36
0.33
0.35
0.33
0.31
0.32
0.73
0.75
1.06
0.58
0.57
0.73
0.55
0.55
0.49
1.40 1.10 0.90 0.55
1.42 1.13 0.90 0.56
1.94 1.51 1.36 0.57
0.88 0.73 0.70 0.56
0.89 0.72 0.69 0.56
1.40 1.10 0.90 0.55
0.90 0.84 0.61 0.55
0.91 0.90 0.61 0.58
0.90 0.82 0.62 0.56
0.92
0.93
1.33
0.56
0.57
0.92
0.59
0.61
0.60
0.08 0.12
0.08 0.12
0.14 0.25
0.08 0.12
0.08 0.12
0.08 0.12
0.07 0.10
0.06 0.10
0.07 0.10
1.76
1.79
2.46
1.32
1.31
1.76
1.25
1.16
1.13
Soil Taxonomy (with proposed Andisol order)
1.48
1.48
2.23
1.48
1.48
1.48
1.29
1.19
1.20
0.34
0.32
0.57
0.41
0.40
0.34
0.32
0.30
0.26
d e p t s w e r e H a p l u s t a n d s (n = 19). As i n d i c a t e d i n T a b l e V I , m e a n s o f m o s t soil c h e m i c a l p r o p e r t i e s w e r e q u i t e d i f f e r e n t a m o n g t h e p r o p o s e d s u b o r d e r s . T h e s t a n d a r d d e v i a t i o n s w e r e also large, h o w e v e r , i n d i c a t i n g c o n s i d e r a b l e overlap in p r o p e r t i e s for the t w o t a x a U s t a n d s a n d T r o p a n d s . F o r t h e s p e c i f i c p u r p o s e o f g r o u p i n g soils a c c o r d i n g t o n u t r i e n t m a n a g e ment requirements, additional criteria based on nutrient supplying characteristics o f t h e softs a p p e a r n e c e s s a r y .
Homogeneity of the taxa A n o t h e r m e a s u r e o f t h e e f f e c t i v e n e s s o f c l a s s i f i c a t i o n s c h e m e s is t h e p r e c i -
24
O. 7--
P 0 O L E O V R R I R N C E F g R P H
0.60.50.40.30.2O. 1O.O-
I
NO. LEGENO:
. . . . . . . . . . . . . . . . .
5
0
T
OF
TRXR
IN ERCH
* • m _193B ~-~--~ R N D I S O L ~-4~--~ F R E N C H
SYSTEM
T.
. . . . . . . . . . . . . . . . . .
lO
.
.
.
.
.
~ - T
15
20
CRTEGORT *-x-~ RNOEPT ~-4~-~ FRO
Fig. 1. Homogeneity of soil pH within soil groupings, expressed as pooled variance, of 80 Andepts classified according to Soil Taxonomy, Soil Taxonomy with the proposed order Andisols, the French, FAO, and 1938 systems. 0.30P {3 0 L E 0 V R R I R N c E F 0 R
0.25-
0.20-
O. iS-
O. IO-
O. O5-
P 0.000 NI~.
LEGENO:
SYSTEM
OF
1
I
5
I0 TRXQ
IN ERCH
• ~ _1938 ~-~-~ RNOISOL 4,--e-~ F R E N C H
I---
15
I"
20
CRTEDORY ~-x-~ RNOEPT 8-~a-~ FRO
25
sion within the soil taxa which result from classification (Cline, 1949; Webster and Beckett, 1968). Such precision is a comprehensive measure of the ability of the system to group the property in question. The precision associated with each soil property mean reported in Tables II--VI is represented in Table VII and Figs. I and 2 as the pooled variances. For example, the pooled variance of soil pH for the 4 taxa of Soil T a x o n o m y , FAO soil legend, and the 1938 systems are respectively 0.33, 0.34, and 0.36 (Fig. 1). The two taxa of the French System gave precision estimates of 0.35. In this case, all systems gave remarkably similar estimates of precision for soil pH. The 80 soils in this study were placed in all three orders of the 1938 system. This grouping was almost totally ineffective, however, as shown by the lack of improved precision (reduced pooled variance). For example, sample variance for soil pH was 0.64 and after placing the 80 samples into 3 groups of Zonal, Intrazonal, and Azonal soils the pooled variance was still 0.63 which indicates no substantial improvement in homogeneity. This category also was ineffective for all other soil chemical properties examined in this study (Table VII). Plots of the estimates of precision (pooled variance) against the number of taxa in each category also demonstrate which differentiae were most effective (Figs. 1 and 2). The differentiae which separate the 80 samples into 2 groups accounted for the most variation in the French System and the proposed order Andisols, whereas the differentiae which separate the samples into 4 groups were most effective in the Soil T a x o n o m y 1938 System and FAO legend. Further partitioning by any system was not effective (Table VII), indicating that the criteria used for the additional partitioning were not well correlated with the chemical properties of these soils. Why each system had one category which was especially effective in grouping the soil properties is not clear. This result emphasizes the need to examine the differentiae used to group soils and the correlations among such criteria and accessory soil properties. With the exception of Soil T a x o n o m y , the precise differentiae used by the various systems are n o t apparent. The differentiae that the systems use must be more precisely known in order to properly evaluate and suggest improvements. The results of this study also suggest that the application of criteria at the lower categories may be far less effective than is generally supposed if such criteria are highly correlated with criteria applied at higher categories. Rapid assessment of classification system performance permits comparison of numerous classification systems including trial systems or those designed for specialized uses. This in turn should p r o m o t e incorporation of improvements and development of systems to answer special needs such as those of grouping soils and climates in order to match crop requirements. Fig. 2. Homogeneity of P sorption (P required at 0.02 mg P/l) within soil groupings, expressed as pooled variance, of 80 Andepts classified according to Soil Taxonomy, Soil Taxonomy with the proposed order Andisols, the French, FAO, and 1938 systems.
26 REFERENCES Barr, A.J., Goodnight, J.H., Sail, J.P., Blair, W.H. and Chilko, D.M., 1979. SAS User's Guide. SAS Institute, Inc., Raleigh, NC. Beinroth, F.H., Ikawa, H. and Uehara, G., 1979. Classification of the Soil Series of the State of Hawaii in four systems: a guide to correlate soils. Tech. Rep. 2, Benchmark Soils Project, Univ. of Hawaii, and Univ. of Puerto Rico. Cline, M.G., 1949. Basic principles of soil classification. Soil Sci., 67: 81--91. Cline, M.G., 1955. Soil survey of the territory of Hawaii. Soil Surv. Ser. 1939, No. 25, Soil Conservation Service, USDA, Washington, D.C. Dudal, R., 1976. Inventory of the major soils of the world with special reference to mineral stress hazards. In: M.J. Wright (Editor), Plant Adaptation to Mineral Stress in Problem Soils. Proceedings of a Workshop at the National Agricultural Library, Beltsville, Nov. 1976. Agency for International Development, Washington, D.C. Fox, R.L., Silva, J.A., Younge, O.R., Plucknett, D.L. and Sherman, G.D., 1967. Soil and plant silicon and silicate response by sugar cane. Soil Sci. Soc. Am. Proc., 31: 775- 779 Haan, C.T., 1977. Statistical Methods in Hydrology. Iowa State University Press, Ames. Iowa. Jones, J.P. and Fox, R.L., 1978. Phosphorus nutrition of plants influenced by manganese and aluminum uptake from an oxisol. Soil Sci., 126: 230--236. Leamy, M.L., 1982. Some implications of testing the Andisol proposal. Int. Soil Sci. Soc. Congr., 12th, New Delhi, Abstract. Recel, M., Ikawa, H. and Uehara, G., 1981. The classification of the Andepts of Hawaii according to the proposed key to Andisols. Paper presented to the 4th International Soil Classification Workshop, Rwanda, June 2--12, 1981. Sato, H.H., Ikeda, W., Paeth, R., Smythe, R. and Takehiro, M., 1973. Soil Survey of the Island of Hawaii. USDA-SCS-Univ. of Hawaii Agric. Expt. Sta., Honolulu, Hawaii. Smith, G.D., 1978. Preliminary proposal for reclassification of Andepts and some Andic subgroups. Unpublished manuscript. Soil Survey Staff, 1975. Soil Taxonomy: a Basic System of Soil Classification for Making and Interpreting Soil Surveys. Soil Conservation Service, USDA Agriculture Handbook No. 436, U.S. Government Printing Office, Washington, D.C. Webster, R. and Beckett, P.H.T., 1968. Quality and usefulness of soil maps. Nature (London), 219: 680--682. Yost, R.S. and Fox, R.L., 1981. Partitioning variation in soil chemical properties of some Andepts using Soil Taxonomy. Soil Sci. Soc. Am. J., 45: 373--377.