Compactibility of cohesive soils from tablelands as influenced by cassava wastewater

Gonçalves, Raissa Homem; Nóbrega, Júlio César Azevedo; Santos, Davi Ney; Silva, Reginaldo Barboza da; Ajayi, Ayodele Ebenezer; Lima, José Maria de

doi:10.1590/1413-7054202347015022

ABSTRACT

Consolidation tests give important insights into soil compactibility. However, it requires equipment that is not always available. The costal tablelands in Northeastern Brazil have extensive areas of cohesive soils where compaction is an expressive problem. This region is a prominent producer of food and fibers with cassava as one of the leading products. Part of the cassava is used for flour production, generating wastewater, which is often applied as organic fertilizer to the soil. This can affect the compaction properties of soil due to its dispersing-flocculating characteristics. Uniaxial-compression tests and mathematical models are the primary methods to measure or estimate soil compaction. This study measured soil compression with a centrifuge, seeking a simple-quick method. We used specific loads (stainless-steel cylinders: mass) and increasing G-force (weight) to simulate the pressure on the samples used in most consolidation apparatus. Soils, sampling layers, and the presence of cassava wastewater (manipueira) were also compared since they may affect compactibility-related attributes. Samples of a Gray Cohesive Argisol and Dystrocohesive Yellow Latosol (depths of 0-0.20 m and 0.20-0.40 m) from the Tablelands of the state of Bahia, Brazil, were used. Wastewater affected water-dispersible clay, aggregate stability, pH, ∆pH, flocculation, and organic carbon, thus influencing compactibility but not the moisture and maximum density measured by the Proctor test. Centrifugation caused lower density than the Proctor test. The results were close to those estimated by the mathematical models, thus considered a promising alternative to estimating consolidation. This method also provides insight into the root growth-limiting density and the moisture content that leads to it.

Index terms:
Preconsolidation pressure; soil density; moisture content; G-force; centrifugation.

[1] ^*Corresponding author: jml.dcs@gmail.com

Parameter	Mean ± standard deviation
pH	5.98 ± 0.03
Free cyanide (mg L^-1)	61.27 ± 5.94
Reducing sugars (g L^-1)	40.60 ± 1.74
Nonreducing sugars (g L^-1)	17.51 ± 1.74
Total carbohydrates (g L^-1)	58.11 ± 2.13
Total nitrogen (g L^-1)	1.94 ± 0.08
Ca mg (L^-1)	241.62 ± 5.56
Mg mg (L^-1)	370.59 ± 4.35
P mg (L^-1)	220.35 ± 3.28
Na mg (L^-1)	147.55 ± 1.31
K mg (L^-1)	1247.92 ± 7.36
Zn mg (L^-1)	1.83 ± 0.16
Fe mg (L^-1)	15.37 ± 1.75
Cu mg (L^-1)	1.51 ± 0.02

Parameter	Symbol	Unit	Method
Soil texture	-	g kg^-1	Day (1965DAY, P. R. Particle fractionation and particle-size analysis. In: BLACK, C. A. Methods of soil analysis, Part 1: Physical and Mineralogical properties, including statistics of measurement and sampling. p.545-567, 1965. )
Water-dispersible clay	Wdc	g kg^-1	Day (1965DAY, P. R. Particle fractionation and particle-size analysis. In: BLACK, C. A. Methods of soil analysis, Part 1: Physical and Mineralogical properties, including statistics of measurement and sampling. p.545-567, 1965. )
Degree of flocculation	DF	%	Df = 100(Total Clay-Wdc)/Total Clay
Particle density	PD	Mg m^-3	Blake and Hartge (1986BLAKE, G. R.; HARTGE, K. H. Particle density. In: KLUTE, A. Methods of soil analysis: Part 1: Physical and mineralogical properties, including statistics of measurement and sampling. The American Society of Agronomy, Inc. p.377-382, 1986.)
Density	Ds	Mg m^-3	Blake and Hartge (1986BLAKE, G. R.; HARTGE, K. H. Particle density. In: KLUTE, A. Methods of soil analysis: Part 1: Physical and mineralogical properties, including statistics of measurement and sampling. The American Society of Agronomy, Inc. p.377-382, 1986.)
Aggregate size fraction	AS	mm	Yoder (1936YODER, R. E. A direct method of aggregate analysis of soils and a study of the physical nature of erosion losses. Journal of the American Society of Agronomy, 28(5):337-351, 1936.)/Grohmann (1960GROHMANN, F. Análise de agregados de solos. Bragantia, 19:201-213, 1960. )
Total porosity	TP	%	Tp =100 [1- (Bd/Pd)]
Weighted mean diameter	WMD	mm	Kemper and Rosenau (1986KEMPER, W. D.; ROSENAU, R. C. Aggregate stability and size. Methods of soil analysis. In: KLUTE, A. Part 1: Physical and mineralogical methods, 5th ed. p.425-442, 1986. )
1:2.5 water pH	pH_H2O	-	-
1M KCl pH	pH_KCl	-	-
Delta pH	∆pH	-	∆pH = pH_KCl - pH_H2O
Remaining P	P_rem	mg L^-1	Alvarez et al. (2000ALVAREZ, V. H. V. et al. Determinação e uso do fósforo remanescente. Sociedade Brasileira de Ciência do Solo. Boletim informativo, 25(1):27-32, 2000.)
Total organic matter	OM	g kg^-1	Walkley and Black (1934WALKLEY, A.; BLACK, I. A. An examination of the degtjareff method for determining soil organic matter, and a proposed modification of the chromic acid titration method. Soil Science, 37(1):29-38, 1934. ) Yeomans and Bremner (1988YEOMANS, J. C.; BREMNER, J. M. A rapid and precise method for routine determination of organic carbon in soil. Communications in Soil Science and Plant Analysis, 19(13):1467-1476, 1988. )

Depth (m)	OMC			Dmax
Depth (m)	GCA	DYL	1	GCA	DYL	1
	--------------------%------------------			-------------------- g cm^-3 ---------------
0 - 0.2	8.88 bA	9.71 aA	1	2.23 aA	2.19 bA	1
0.2 - 0.4	8.26 bA	10.22 aA	1	2.23 aA	2.20 bA	1
Mean*	8.57 B	9.97 A		2.23 A	2.20 B

Layer (m)	Treat.	GCA		DYL
		Pressure* (kPa)	Density (Mg m^-3)	Pressure (kPa)	Density (Mg m^-3)
0 - 0.2	DW	95	1.59	90 1.40	1.43
	WW		1.54
0.2 - 0.4	DW	98	1.54	108 1.45	1.46
	WW		1.48

Brasil

Brasil

Compactibility of cohesive soils from tablelands as influenced by cassava wastewater

Compactabilidade de solos coesos dos tabuleiros costeiros do nordeste sob influência de água residuária de mandioca

ABSTRACT