accumulation of soil organic phosphorus by soil tillage and cropping systems under subtropical...

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Accumulation of Soil Organic Phosphorus by Soil Tillageand Cropping Systems Under Subtropical ConditionsDanilo dos Santos Rheinheimer a & Ibanor Anghinoni ba Department of Soil Science , Federal University of Santa Maria—UFSM , Santa Maria, RS,Brazilb Department of Soil Science , Federal University of Rio Grande do Sul—UFRGS , PortoAlegre, RS, BrazilPublished online: 16 Aug 2006.

To cite this article: Danilo dos Santos Rheinheimer & Ibanor Anghinoni (2003) Accumulation of Soil Organic Phosphorus bySoil Tillage and Cropping Systems Under Subtropical Conditions, Communications in Soil Science and Plant Analysis, 34:15-16,2339-2354, DOI: 10.1081/CSS-120024068

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Accumulation of Soil Organic Phosphorusby Soil Tillage and Cropping Systems

Under Subtropical Conditions

Danilo dos Santos Rheinheimer1 and Ibanor Anghinoni2,*

1Department of Soil Science, Federal University of Santa

Maria—UFSM, Santa Maria, RS, Brazil2Department of Soil Science, Federal University of Rio Grande

do Sul—UFRGS, Porto Alegre, RS, Brazil

ABSTRACT

Changes in the concentration of organic phosphorus (P) fractions as

affected by different soil tillage and cropping systems were analyzed in

four long-term experiments established on two Oxisols (very clayey and

clayey Rhodic Hapludox) and one Ultisol (sandy clay loam Rhodic

Paleudult) of different clay contents, in southern Brazil. No tilled and

conventional tilled soil under several crop sequences were collected in

1997 at three depths (0–2.5, 2.5–7.5, 7.5–17.5 cm) and analyzed for

total, inorganic and organic soluble P by using different extractants (0.5 M

sodium bicarbonate (NaHCO3) and 0.1 and 0.5 M sodium hydroxide

2339

DOI: 10.1081/CSS-120024068 0010-3624 (Print); 1532-2416 (Online)

Copyright q 2003 by Marcel Dekker, Inc. www.dekker.com

*Correspondence: Ibanor Anghinoni, Department of Soil Science, Federal University

of Rio Grande do Sul—UFRGS, Postal Box 776, CEP 90001-970, Porto Alegre, RS,

Brazil; E-mail: [email protected].

COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS

Vol. 34, Nos. 15 & 16, pp. 2339–2354, 2003

MARCEL DEKKER, INC. • 270 MADISON AVENUE • NEW YORK, NY 10016

©2003 Marcel Dekker, Inc. All rights reserved. This material may not be used or reproduced in any form without the express written permission of Marcel Dekker, Inc.

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(NaOH)). Microbial P was also determined. The sum of the organic P

extracted by the three extractants and microbial P were considered the

biological P pool, whereas the sum of inorganic and organic P in the

residue was considered the geochemical P pool. Effects of soil tillage and

cropping systems were mostly observed in the low activity clay soil

(sandy clay loam Paleudult), with higher values under no-tillage and for

soil cropped to oat þ vetch/corn þ cowpea rotation. Organic P

accumulated mainly as the moderately labile P pool (P–NaOH). The

geochemical P pool was higher than the biological P pool, and the

biological reactions showed increasing importance in the low-active

surface topsoil layer of no-tilled soils.

Key Words: Geochemical and biological phosphorus; Organic phos-

phorus; Soil management.

INTRODUCTION

It is generally accepted that in more weathered soils, phosphates are

adsorbed by aluminum (Al) and iron (Fe) oxides and hydroxides.[1] The

organic P is associated with high molecular weight compounds through

aluminum and iron linkages and not as structural components.[2] The P

distribution in different fractions will then depend on the soil parent material,

weathering degree, and physical, chemical and mineralogical characteristics,

biological activity and dominant vegetation.[3,4]

Hedley et al.[5] proposed a fractionation method for total P, with organic P

of increasing stability towards microbial activity, based on extractions by a

sequence of alkaline solutions. The organic P extracted by NaHCO3 will be

easily mineralized and thus considered to be potentially available to plants and

microorganisms (labile Po). The organic P extracted by NaOH is considered as

moderately labile and can accumulate during soil formation. Cross and

Schlesinger[4] suggested that biological P is composed of organic P extracted

with NaHCO3 and NaOH, while geochemical P includes the inorganic P

extracted with the same extractants used in the fractionation procedure plus

the highly stable residual P fraction.

The cropped area under no-tillage in southern Brazil has increased greatly

in the last decade, reaching about 7 million ha today. Oxisols and Ultisols are

the dominant soils, with a variety of physical, chemical and mineralogical

characteristics, and the cropping systems include plants with different yields

under subtropical climate conditions.

In no-tilled soils, the organic matter content increases in the surface

layers since in the absence of erosion, the addition rate is higher than

dos Santos Rheinheimer and Anghinoni2340



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the decomposition rate. As fertilizers are surface applied, without

incorporation, the P content largely increases in the surface layer.[6] However,

the increase in organic P content can be lower than the increase in total P

content.[7] It was also observed[8] that total carbon (C) and nitrogen (N)

contents can increase without changes in organic P, because of P adsorption by

Al and Fe compounds and or dominance of P mineralization over

immobilization.

The knowledge of P distribution in the different pools in different soils

under various soil tillage and cropping systems is important for assessing short

and long-term P availability. This would allow one to optimize the use of P

fertilizer. The effects of soil tillage and cropping systems on P availability and

distribution are poorly known in most soils,[4,5] but are almost unknown in

Brazilian soils.

The objective of this research was to measure the changes in organic P

fractions in different soils under various tillage and cropping systems in

southern Brazil.

MATERIALS AND METHODS

Site and Experiment Description

The research was conducted in four long-term experiments in the state of

Rio Grande do Sul, in southern Brazil (latitude range of 278 to 308S, average

annual temperature of 208C, January, 318C and June, 8.58C, and annual

precipitation of 1400 mm), based on a split plot design with randomized

blocks with four replications in the first experiment, and three replications in

the other experiments. In each experiment, the tillage system treatments were

located in the main plots and the different crop sequences, in the split plots.

The first experiment was set up in 1979, at the Center of Agriculture and

Forest Activity of the Wheat Cooperative of Santo Angelo on a very clayey

Rhodic Hapludox, derived from basalt, with 680 g kg21 clay, 246 g kg21 iron

extracted by dithionite–citrate–bicarbonate, and pH of 5.6 (soil:water 1:1).

No-tilled and conventionally tilled plots were cropped with (a) wheat/soybean

or (b) forage oat (Avena strigosa)/corn (Zea mays). The effect of a third crop

rotation [wheat, soybean, lupin (Lupinus angustifolius), corn, sorghum

(Sorghum vulgare), and forage oat þ clover (Trifolium repens)] was only

monitored in no-till treatments. No N fertilizer was applied whereas an overall

input of 792 kg ha21 of the P was applied over the 18 years.

The second experiment was started in 1983, at the National Wheat

Research Center/EMBRAPA, in Passo Fundo on a clayey Rhodic Hapludox,

Accumulation of Soil Organic P 2341



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derived from basalt, with 530 g kg21 clay, 56 g kg21 iron extracted by

dithionite–citrate–bicarbonate, and pH 5.8 (soil:water 1:1). No-tilled or

conventional tilled plots were cropped with (a) common vetch (Vicia sativa),

corn, forage oat, soybean, barley (Hordeum vulgare), soybean, common

vetch, corn, forage oat, soybean, barley, soybean, common vetch and sorghum

or (b) forage oat, soybean, barley, soybean, common vetch, corn, forage oat,

soybean, barley, soybean, common vetch, sorghum, forage oat and soybean.

Soils were sampled under the last listed crop (sorghum or soybean) of each

rotation. The overall P input over 14 years was 616 kg ha21.

The third experiment started in 1985, at the Agronomic Experimental

Station/UFRGS, in Eldorado do Sul on a sandy clay loam Rhodic Paleudult,

derived from granite, and conventionally tilled for 15 years. The soil had

220 g kg21 clay, 36 g kg21 iron extracted by dithionite–citrate–bicarbonate,

and pH 5.7 (soil:water 1:1). No-tilled and conventional tilled plots were

cropped with (a) forage oat/corn or forage oat þ common vetch/corn þ

cowpea (Vigna unguiculata). No N fertilizer was applied whereas an overall

input of 528 kg ha21 of the P was applied over the 12 years.

The fourth experiment started in 1983 in an area beside experiment 3.

There were only no-till and three crop rotations treatments: (a) forage

oat/corn, (b) forage oat þ common vetch/corn þ cowpea, and (c) pigeon pea

(Cajanus cajan)/corn). No N fertilizer and the same P input as in the previous

experiment was applied.

Soil Sampling

Soils were collected in May 1997, at three depths (0–2.5, 2.5–7.5 and

7.5–17.5 cm), just after tillage. Two sub-samples of 50 £ 10 cm (wide £

thickness) were mixed, air dried, sieved (,1 mm) and stored at room

temperature.

Soil Analysis

Organic P was estimated by the difference between the amount extracted

by 0.2 M HCl with and without ignition.[9] Organic and inorganic P was also

extracted from soil samples with 0.5 M NaHCO3 at pH 8.5, and with 0.1 and

0.5 M NaOH in a sequential procedure.[5] The inorganic P (Pi) of the extracts

was determined as reported by Dick and Tabatabai,[10] whereas the total P was

obtained after digestion of the extract obtained with a H2O2 þ H2SO4 þ

MgCl2 solution.[11]




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The amount of microbial P was determined as reported by Hedley and

Stewart,[12] with available Pi extracted by resin before fumigation,[13] and

calculated by considering the amount adsorbed by soil.[14] The sum of

microbial P with the organic P, extracted with NaHCO3, 0.1 M and 0.5 M

NaOH gave the biological P pool, while the sum of the inorganic P and

residual total P was considered as the geochemical P pool.[4]

The clay content was determined by the densimeter method, the iron

content was determined after sodium dithionite–citrate–bicarbonate extrac-

tion, and the total organic C, by wet digestion.[15]

RESULTS AND DISCUSSION

Total Organic Phosphorus

Total organic P content in the very clayey Hapludox soil was not affected

by any of the different crop rotations under no-tillage system for 18 years

(Table 1). The average value for organic P was 268 mg kg21, representing

only 31% of the total P, because of the low organic C input. It is reasonable to

hypothesize that crop yield was low because no fertilizer N was applied. The

high percentage of inorganic P (69%) may also be the result of the high

inorganic P adsorption by clay (680 g kg21) and iron oxide (246 g kg21).

The organic P content of the clayey Hapludox soil was affected by tillage

system (Table 1), since it did not change with soil depth under conventional

tillage, whereas the values were higher in the two surfaces than in the deep

layer under no-tillage. The surface values were also higher than those of the

same soil layers under conventional tillage. However, the organic/total P ratio

was lower[31] in no-tilled than in conventionally tilled[38] plots. This is

further evidence that P mainly accumulates as inorganic forms due to the

strong interactions of P with iron and aluminum oxides.

The no-tillage for 12 years in the Paleudult soil (third experiment) created

a higher organic P contents in all analyzed layers, as compared to

conventionally tilled soil (Table 1). The average values for organic P were 113

and 86 mg kg21 for no-tilled and conventionally-tilled plots, respectively. The

use of the oat þ vetch/corn þ cowpea produced a higher organic P content

(average of 107 mg kg21), as compared to oat / corn (average 87 mg kg21).

Regardless of the soil tillage or cropping system, organic P content decreased

from top to subsoil layers; however this decrease was more intense in no-tilled

treatments because of surface deposition of crop residues.

The conversion of inorganic to organic P is related to the C, N, and sulfur

(S) dynamics in soil.[16] Total organic C and total N contents increased by




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Table 1. Total organic phosphorus (TOP) and ratios TOP/total P (TP) and carbon (C)/organic P (OP) as affected by tillage, crop

rotation, and soil depth.

Soil layer (cm)

Soil Treatment 0–2.5 2.5–7.5 7.5–17.5 Average TOP/TP C/OP

TOP (mg kg21)

Very clayey Soil tillage

Rhodic Hapludox No-tillage 290 260 222 275 A 31 A 74 A

Conventional 263 280 240 261 A 31 A 71 A

Crop rotation

Oat/corn 271 285 238 265 A 31 A 70 A

Wheat/soybean 282 271 236 263 A 31 A 74 A

Crop rotation 294 243 214 250 A 32 A 76 A

Clayey Rhodic Soil tillage

Hapludox No-tillage 256 aA 259 aA 185 bB 31 B 70 A

Conventional 229 aB 224 aB 217 aA 38 A 71 A

Previous crop

Sorghuma 233 239 179 217 A 34 A 65 B

Soybean 235 235 215 228 A 35 A 78 A

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Sandy clay

loam Rhodic

Paleudult

Soil tillage

No-tillage 143 106 90 113 A 29 A 118 B

Conventional 98 82 78 86 B 25 B 137 A

Crop rotation

Oat/corn 98 85 77 87 B 23 B 132 A

Oat þ

vetch/corn

þ cowpea

135 102 84 107A 31 A 127 B

Crop rotation

Oat/corn 130 aB 89 bB 80 bA 25 C 134 A

Oat þ

vetch/corn

þ cowpea

159 aAB 119 abAB 91 bA 33 A 116 B

Pigeon pea

þ corn

188 aA 142 bA 89 cA 30 B 137 A

Mean values followed by the same letter, small in the line and capital in the column, are not different by Tukey ðp , 0:05Þ:a Sorghum or soybean as previous crop before soil sampling.

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increasing the input of crop residues in the first nine years (1985/94) in both

cropping systems in the third experiment under both tillage systems.[17,18] The

increase was higher for oat þ vetch/corn þ cowpea in no-tillage than oat/corn

in conventional tillage, and was attributed to the highest addition of crop

residues and to the lowest soil organic losses (erosion and oxidation). Total

organic C was 12 Mg ha21 and total N was 0.9 Mg ha21 higher in

oat þ vetch/corn þ cowpea in no-tillage than in oat/corn conventionally-

tilled soil in the 0–30 cm soil layer. This means an increase of 1.33 Mg ha21 of

total organic C and of 0.10 Mg ha21 of total N per year. The C sequestration by

soil accounted for 44 Mg ha21 more CO2 removal from the atmosphere in nine

years by oat þ vetch/corn þ cowpea in no-tillage.

Comparisons among crop sequences under no-tillage system (fourth

experiment) show higher organic P for the oat þ vetch/corn þ cowpea

followed by pigeon pea þ corn and oat/corn. These effects were generally

observed in the two surface soil layers. The increase in organic P was

also obtained by a high input of plant residues to soil and/or by plant ability to

absorb high P amounts from the soil solution, as observed for cowpea and

pigeon pea.[19] Crops with high yields increased the organic P content, because

they store large amounts of this nutrient in plant residues; this stimulates

microbial growth and increases the organic matter contents of soil.[20] The

addition of ten crop residues in the first 12 years[17,18] in the fourth experiment

increased total C and total N contents in the 0–17 cm layer; and this increase

was related to CðY ¼ 28:63 þ 0:19X; r2 ¼ 0:81* Þ and NðY ¼ 2:63 þ 0:28X;

r2 ¼ 0:76* Þ inputs. Additions by oat/corn, oat þ vetch/corn þ cowpea and

pigeon pea þ corn were 37.0, 67.3, and 75.2 Mg C ha21 and 1.7, 2.5, and

3.4 Mg N ha21, respectively. About 19% of C and 28% of N present in crop

residues remained in the soil.[17]

The C/organic P ratio (C/OP) (Table 1) was about 70 for the Hapludoxes

and about 120 for the Paleudult soil. It is reasonably to hypothesize that

because of the low clay and oxides content of the latter soil, the C

accumulation or oxidation and the P immobilization or mineralization

turnover are more rapid in the latter than in the former soils. Labile organic

phosphates will be rapidly decomposed under cultivation because P is

adsorbed less in the Paleudult soil. The C/OP ratio is lower in the Hapludoxes

than in the Paleudult soils because the simple organic phosphates are strongly

adsorbed by soil colloids,[21] and the C content does not show marked

changes. In this way, either tillage or cropping system did not affect such ratio

in the Hapludoxes. The highest ratio in the clayey Hapludox was observed

after sorghum (Table 1). The ratio was lower in no-tilled (118) than

conventionally tilled (137) Paleudult soil because, as reported by Bayer

et al.,[17,18] there is a higher input of crop residues and a lower decomposition




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rate under no-tillage.[22] In the same way, because of higher residue

addition,[18] the C/OP ratio was higher for pigeon pea/corn (137) and

oat þ vetch/corn þ cowpea (134) than oat/corn þ cowpea (116) under no-

tillage (Table 1).

Labile Organic Phosphorus

The labile organic P content, as estimated by NaHCO3 extraction, in the

very clayey Hapludox was very low, 1.5% of the total P, and was not affected

by tillage or crop rotation (Table 2). It has been observed that tropical soils

with surface-active colloids had a very low content of labile organic P.[21,23]

The labile organic P contents were not affected ðp , 0:05Þ by tillage, sorghum

or soybean in the clayey Hapludox soil (Table 2).

In the Paleudult soil (Table 2), the labile organic P was higher under no-

tillage (14 mg kg21) than conventional tillage (11 mg kg21). The values for

this soil are higher than in the very clayey Hapludox, which may indicate that

labile organic P accumulates in soils with low contents of surface-active clay.

The highest labile organic P content resulted from oat þ vetch/corn þ

cowpea, followed by pigeon pea þ corn and oat/corn under no-tillage in the

sandy clay loam soil (fourth experiment, Table 2).

Moderately Labile Organic Phosphorus

The organic P content extracted by 0.1 M NaOH (Table 3) in the very

clayey Hapludox (first experiment) was much higher than that obtained by

0.5 M NaOH (Table 4) and by NaHCO3 (Table 2) extractions. Therefore, the

organic P (Table 1) seems to accumulate in moderately labile forms. These

results agree with those of Tiessen et al.,[23] who observed variations in

organic P extracted by NaOH caused by tillage in tropical soils with high

phosphate sorption capacity.

There was a significant interaction of soil tillage system and previous

crop (sorghum or soybean) in the clayey Hapludox soil (second

experiment), for moderately labile organic P. In no-tillage, the content of

organic P extracted by 0.1 M NaOH was higher after soybean (85 mg kg21)

than after sorghum (43 mg kg21) (Table 3). Similarly, for 0.5 M NaOH

extraction, the content of organic P in the soil was also higher after soybean

(77 mg kg21) than after sorghum (59 mg kg21) (Table 4). Again, the organic

P extracted by both NaOH solutions was the most sensitive fraction to

detect modifications caused by tillage and previous crop. The incorporation




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Table 2. Organic phosphorus extracted by sodium bicarbonate in soil as affected by tillage, crop rotation, and soil depth.

Soil tillage

Soil Soil layer (cm) No-tillage (mg kg21) Conventional (mg kg21) Crop rotation or previous cropa (mg kg21)

O/C W/S Rotation

Very clayey 0–2.5 3 4 3 3 4

Rhodic 2.5–7.5 2 4 2 3 3

Hapludox 7.5–17.5 4 5 4 2 4

Average 3 a 4 a 3 a 3 a 4 a

Sorghum Soybean

Clayey 0–2.5 20 15 17 18

Rhodic 2.5–7.5 17 16 16 16

Hapludox 7.5–17.5 16 13 11 16

Average 18 a 15 a 15 a 17 a

O/C O þ V/C þ Cp

Sandy clay loam 0–2.5 23 13 18 17

Rhodic 2.5–7.5 11 10 15 11

Paleudult 7.5–17.5 9 9 8 9

Average 14 a 11 b 14 a 12 a

O/C O þ V/C þ Cp Pp þ C

Sandy clay loam 0–2.5 12 38 32

Rhodic 2.5–7.5 15 26 21

Paleudult 7.5–17.5 18 22 20

Average 15 b 29 a 24 ab

Sorghum or soybean as previous crop before soil sampling.

Means values followed by the same letter, are not different by Tukey ðp , 0:05Þ:a O/C ¼ oat/corn; W/S ¼ wheat/soybean; O þ V/C þ Cp ¼ oat þ vetch/corn þ cowpea; Pp þ C ¼ pigeon pea/corn.

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Table 3. Organic phosphorus extracted by 0.1 M sodium hydroxide as affected by tillage, crop rotation, and soil depth.

Soil tillage


O/C W/S Rotation

Very clayey 0–2.5 167 aA 139 bA 146 154 179

Rhodic 2.5–7.5 153 aB 144 aA 143 164 163

Hapludox 7.5–17.5 125 aC 128 aB 129 127 125

Average 139 a 148 a 156 a

Clayey Sorghum Soybean

Rhodic No-tillage 43 bB 85 aA

Hapludox Conventional 64 aA 69 aB

O/C O þ V/C þ Cp

Sandy clay loam 0–2.5 74 A 42 A 52 62

Rhodic 2.5–7.5 59 B 42 A 47 54

Paleudult 7.5–17.5 55 B 39 A 43 48

Average 63 a 41 b 47 b 55 a

O/C O þ V/C þ Cp Pp þ C Average

Sandy clay loam 0–2.5 53 53 53 53 A

Rhodic 2.5–7.5 32 37 45 38 AB

Paleudult 7.5–17.5 23 25 25 24 B

Average 36 a 38 a 41 a


Mean values followed by the same letter, small in the line and capital in the column, are not different by Tukey ðp , 0:05Þ:a O/C ¼ oat/corn; W/S ¼ wheat/soybean; O þ V/C þ Cp ¼ oat þ vetch/corn þ cowpea; Pp þ C ¼ pigeon pea/corn.

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Table 4. Organic phosphorus extracted by 0.5 M sodium hydroxide as affected by tillage, crop rotation, and soil depth.

Soil tillage


O/C W/S Rotation

Very clayey 0–2.5 60 aA 54 aB 45 67 69

Rhodic 2.5–7.5 23 bB 66 aA 46 49 24

Hapludox 7.5–17.5 20 bB 49 aB 30 44 12

40 b 53 a 35 b

Clayey Average Sorghum Soybean

Rhodic No-tillage 59 bB 77 aA

Hapludox Conventional 97 aA 71 bA

O/C O þ V/C þ Cp

Sandy clay loam 0–2.5 40 25 19 bA 44 aA

Rhodic 2.5–7.5 26 19 16 bA 28 aB

Paleudult 7.5–17.5 20 21 21 aA 18 aB

Average 29 a 22 b

O/C O þ V/C þ Cp Pp þ C

Sandy clay loam 0–2.5 6 9 29

Rhodic 2.5–7.5 4 5 21

Paleudult 7.5–17.5 6 4 26

Average 5 b 6 b 25 a


Mean values followed by the same letter, small in the line and capital in the column, are not different by Tukey ðp , 0:05Þ:a O/C ¼ oat/corn; W/S ¼ wheat/soybean; O þ V/C þ Cp ¼ oat þ vetch/corn þ cowpea; Pp þ C ¼ pigeon pea/corn.

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Table 5. Biological and geochemical phosphorus as affected by tillage, crop rotation, and soil depth.

Very clayey

Rhodic Hapludox Clayey Rhodic Hapludox

Sandy clay loam

Rhodic Paleudult

Sandy clay loam

Rhodic Paleudult

P poola No-tillage Conventional No-tillage Conventional No-tillage Conventional O/Cb O þ V/C þ Cp Pp þ C

(mg kg21)

0–2.5 cm

Biological 275 ac 230 b 218 a 186 b 169 a 94 b 97 b 124 a 142 a

Geochemical 588 a 501 b 708 a 514 b 353 a 281 b 365 a 309 b 331 b

2.5–7.5 cm

Biological 203 b 240 a 170 a 184 a 109 a 78 b 64 b 82 ab 103 a

Geochemical 567 a 563 a 667 a 511 b 275 a 264 a 275 a 245 a 285 a

7.5–17.5 cm

Biological 170 b 208 a 138 b 175 a 90 a 74 b 54 a 61 a 77 a

Geochemical 446 b 497 a 554 a 478 b 197 a 233 a 241 a 192 b 239 ab

a Biological ¼ P-microbial þ Po–NaHCO3 þ Po-0.1NaOH þ Po-0.5NaOH; Geochemical ¼ inorganic P þ Po-residual.b O/C ¼ oat/corn; O þ V/C þ Cp ¼ oat þ vetch/corn þ cowpea; Pp þ C ¼ Pigeon pea þ corn.c Means values for soil tillage methods and crop sequences followed by the same letters, are not different by Tukey ðp , 0:05Þ:

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of sorghum residues with low P content in the soil stimulated P

immobilization in organic forms.

Long-term management under no-tillage in the Paleudult soil resulted in

higher content of moderately labile organic P than under conventional tillage

(Tables 3 and 4). Organic P values extracted by 0.1 M NaOH were generally

higher in the topsoil layers under no-tillage (Table 3). The higher organic P

content for oat þ vetch/corn þ cowpea, as compared to oat/corn (Table 1), is

related to the amount extracted with both 0.1 and 0.5 M NaOH solutions. As

previously presented,[18] higher organic C contents were already observed in

the first nine years of the experiment for such crop sequences and no-tillage

management.

Table 5 shows biological and geochemical P pools in all experiments.

Overall, the geochemical P pool was higher than the biological P pool. The

geochemical pool was affected by soil tillage in all experiments, being higher

in the no-tillage system. The contribution of the biological pool increased in

the surface layer of the sandy clay loam soil (Paleudult), mostly when high

residue yielding plants were used. The division of P into geochemical and

biological pools can help in assessing the impact of soil management systems,

crop rotation or P cycling in soil.

CONCLUSIONS

The main findings of this research can be summarized as:

1. Long-term no-tillage systems did not affect the total organic P

content in the very clayey (Hapludox) soil, but increased this pool in

the clayey (Hapludox) and in the sandy clay loam (Paleudult) soils,

compared to the conventional tillage.

2. Cropping with oat þ vetch/corn þ cowpea increased total organic P

content in the low active-clay soil (Palaeudult).

3. The major portion of organic P was accumulated in the moderately

labile form.

4. The labile organic P content was higher under no-tillage in the low

active-surface soil, with no effects of soil tillage or cropping system

in the high phosphate sorption soils.

5. The geochemical P pool was higher than the biological P pool; the

importance of the biological reactions in the no-tillage system

increased in the top layer, especially in the low-active clay soil and

crops with high capacity of residue production.




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ACKNOWLEDGMENTS

To the researchers Joao Mielniczuk, Rainoldo Alberto Kochhann,

Amando Dalla Rosa, and Joao Becker, by making the experimental area

available for collecting the soil samples used in this research. Research

supported by Pronex/CNPq and Fapergs.

REFERENCES

1. Walker, T.W.; Syers, J.K. The fate of phosphorus during pedogenesis.

Geoderma 1976, 15, 1–19.

2. Brannon, C.A.; Sommers, L.E. Stability and mineralization of organic

phosphorus incorporated into model humic polymers. Soil Biol.

Biochem. 1985, 17, 221–227.

3. Magid, J. Vegetation effects on phosphorus fraction in set-aside soils.

Plant Soil 1993, 149, 111–119.

4. Cross, A.F.; Schlesinger, W.H. A literature review and evaluation of the

Hedley fractionation: applications to the biogeochemical cycle of soil

phosphorus in natural ecosystems. Geoderma 1995, 64, 197–214.

5. Hedley, M.J.; Stewart, J.W.B.; Chauhan, B.S. Changes in inorganic and

organic soil phosphorus fractions induced by cultivation practices and by

laboratory incubations. Soil Sci. Soc. Am. J. 1982, 46, 970–976.

6. Andraski, B.J.; Mueller, D.H.; Daniel, T.C. Phosphorus losses in runoff

as affected by tillage. Soil Sci. Soc. Am. J. 1985, 49, 1523–1527.

7. Selles, F.; Kochhann, R.A.; Denardin, J.E.; Zentner, R.P.; Faganello, A.

Distribution of phosphorus fractions in Brazilian oxisol under different

tillage systems. Soil Till. Res. 1977, 44, 23–24.

8. Kingery, W.L.; Wood, C.W.; Williams, J.C. Tillage and amendment

effects on soil carbon and nitrogen mineralization and phosphorus

release. Soil Till. Res. 1996, 37, 239–250.

9. Olsen, S.R.; Sommer, L.E. Phosphorus. In Methods of Soil Analysis,

Part 2. Chemical and Microbiological Properties; Page, A.L.,

Miller, R.H., Keeney, Q.R., Eds.; ASA-SSSA: Madison, WI, 1982;

403–430.

10. Dick, W.A.; Tabatabai, M.A. Determination of orthophosphate in

aqueous solutions containing labile organic and inorganic phosphorus

compounds. J. Environ. Qual. 1977, 6, 82–85.

11. Brookes, P.C.; Powlson, D.C. Preventing phosphorus losses during

perchloric acid digestion of sodium bicarbonate soil extracts. J. Sci.

Food Agric. 1982, 32, 671–674.




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ded

by [

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ity o

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a] a

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er 2

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12. Hedley, M.J.; Stewart, J.W.B. Method to measure microbial phosphate

in soil. Soil Biol. Biochem. 1982, 14, 377–385.

13. Brookes, P.C.; Powlson, D.S.; Jenkinson, D.S. Measurement of

microbial biomass phosphorus in soil. Soil Biol. Biochem. 1982, 14,

319–329.

14. Morel, C.; Tiessen, H.; Stewart, J.W.B. Correction for P-sorption in the

measurement of soil microbial biomass P by CHCl3 fumigation. Soil

Biol. Biochem. 1996, 28, 1699–1706.

15. Tedesco, M.J.; Gianello, C.; Bissani, C.A.; Bohnen, H.; Volkweiss, S.J.

Analysis of Soil, Plant and Other Materials; (in Portuguese) Federal

University of Rio Grande do Sul: Porto Alegre, Brazil, 1995.

16. Stewart, J.W.; Tiessen, H. Dynamics of soil organic phosphorus.

Biogeochemistry 1987, 4, 41–60.

17. Bayer, C.; Martin-Neto, L.; Mielniczuk, J.; Ceretta, C.A. Effect of no-till

cropping systems on soil organic matter in a sandy clay loam Acrisol

from Southern Brazil monitored by electron spin resonance and nuclear

magnetic resonance. Soil Till. Res. 2000, 53, 95–104.

18. Bayer, C.; Mielniczuk, J.; Amado, T.J.C.; Martin-Neto, L.; Fernandes,

S.V. Organic matter storage in a sandy clay loam Acrisol affected by

tillage and cropping systems in southern Brazil. Soil Till. Res. 2000, 54,

101–109.

19. Ae, N.; Arihara, J.; Okada, K.; Yoshihara, T.; Johansen, C. Phosphorus

uptake by pigeon pea and its role in cropping systems of the Indian

Subcontinent. Science 1990, 248, 477–480.

20. Hands, M.; Harrison, A.F.; Bayiss-Smith, R. Phosphorus dynamics in

slash-and-burn and alley cropping on Ultisols of the humic tropics. In

Phosphorus in the Global Environment: Transfers, Cycles and

Management; Tiessen, H., Ed.; Wiley J. Chichester: Toronto, Canada,

1995; 155–170.

21. Anderson, G.; Williams, E.G.; Moir, J.O. A comparison of the sorption

of inorganic orthophosphate and inositol hexaphosphate by six acid

soils. J. Soil Sci. 1974, 25, 51–62.

22. Weil, R.R.; Benedetto, P.W.; Sikora, L.J. Influence of tillage practices

on phosphorus distribution and forms in three Ultisols. Agron. J. 1988,

80, 503–509.

23. Tiessen, H.; Salcedo, I.H.; Sampaio, E.V.S.B. Nutrient and soil organic

matter dynamics under shifting cultivation in semi-arid Northeastern

Brazil. Agric. Ecosyst. Environ. 1992, 39, 139–151.




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accumulation of soil organic phosphorus by soil tillage and cropping systems under subtropical...

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