Least limiting water range, S-index and compressibility of a Udalf under different management systems

Lima, Cláudia Liane Rodrigues de; Dupont, Patrícia Bianca; Pillon, Clenio Nailto; Miola, Ezequiel Cesar Carvalho

doi:10.1590/1678-992X-2017-0224

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Agricultural Engineering • Sci. agric. (Piracicaba, Braz.) 77 (1) • 2020 • https://doi.org/10.1590/1678-992X-2017-0224 copy

Least limiting water range, S-index and compressibility of a Udalf under different management systems

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

Agricultural areas in the region of Turuçu, on the Southeast Hillside in the state of Rio Grande do Sul (RS), Brazil present many examples of soil physical degradation. Accordingly, strategies aimed at evaluating and ameliorating the structural quality of soils should be developed to ensure the sustainable use of these areas. This study aimed to evaluate the least limiting water range (LLWR), S-index, compressibility parameters, organic carbon and the organic matter granulometric fractions of a Udalf under different agricultural uses. Soil samples with disturbed and non-disturbed structure from the 0.00 to 0.10 m layer were collected on farms in the Southeast Hillside, Turuçu region, RS, for analyzing soil under: i) conventional system of corn after tobacco crop, (CT); ii) conventional system of corn after native field (CNF), iii) native field (NF) and iv) native area (NA). Both the CT and the CNF systems had a negative influence on the values of bulk density, soil porosity, least limiting water range, compressibility parameters and total organic carbon, coarse fraction carbon and carbon associated with minerals.

Keywords:
soil quality; soil physics; soil structure; soil compaction

Management systems¹ 1 CT = soil with corn crop after tobacco crop under a conventional system; CNF = soil with corn crop after native field under a conventional system; NF = native field soil and NA = native area.	Clay	Silt	Sand	TOC
	------------------------------------ g kg^–1 ------------------------------------
CT	94.1	206.4	699.5	6.3
CNF	134.5	214.4	651.1	9.7
NF	152.1	240.2	607.7	17.5
NA	178.0	270.1	551.9	18.2

Equation	Coefficient	CT	CNF	NF	NA
$\begin{array}{l} θ \\ = θ r e s \\ + \frac{θ_{s a t} - θ_{r e s}}{{[1 + {(α \times \| ψ \|)}^{n}]}^{m}} \end{array}$	θ_res	0.06	0.14	0.15	0.11
	θ_sat	0.21	0.31	0.37	0.33
	α	0.12	0.26	0.01	0.01
	m	0.21	3.35	5.02	1.71
	n	2.25	3.18	3.20	6.24
$θ = exp (a \times bBd) ψ^{c}$	a	-2.63	-1.66	-1.03	-0.93
	b	0.12	-0.19	-0.52	-0.64
	c	-0.17	-0.14	-0.14	-0.13
$PR = d θ^{e} {B d}^{f}$	d	0.00	0.05	0.21	0.39
	e	-1.36	-1.38	-1.03	-0.67
	f	8.90	4.47	3.44	2.67

Management systems¹ 1 CT = soil with corn crop after tobacco crop under a conventional system; CNF = soil with corn crop after native field under a conventional system; NF = native field soil and NA = native area. Δref. (%) = increase (+) or decrease (-) as a percentage of NF. Means followed by the same small letter in the column, did not differ from each other in the LSD test at the 5 % level.	Bd	Tp	θ_FC	θ_PWP	AW	S
	Mg m^–3	-------------------------------------------------------- m³ m^–3 -------------------------------------------------------------				-
CT	1.65 a	0.35 c	0.19 b	0.10 c	0.09 ns	0.036 ns
Δ_ref. NF (%)	+17.9	-20.5	-36.7	-54.5	+12.5	-64.7
Δ_ref. NA (%)	+15.4	-14.6	-34.5	-37.5	-30.8	-50.0

CNF	1.50 b	0.40 b	0.26 a	0.18 ab	0.08 ns	0.082 ns
Δ_ref. NF (%)	+7.1	-9.1	-13.3	-18.2	0.0	-19.6
Δ_ref. NA (%)	+4.9	-2.4	-10.3	+12.5	-38.5	+13.9

NF	1.40 c	0.44 a	0.30 a	0.22 a	0.08 ns	0.102 ns
NA	1.43 bc	0.41 ab	0.29 a	0.16 b	0.13 ns	0.072 ns

Systems of use¹ 1 CT = soil with corn crop after tobacco crop under a conventional system; CNF = soil with corn crop after native field under a conventional system; NF = native field. Δref. (%): increase (+) or decrease (-) as a percentage of NF. Means followed by the same small letter in the column, did not differ from each other in the LSD test at the 5 % level.	σ _p	CI	Bd_{σ p}	CD_200kPa	CD_1600kPa	CD_{σ p}
	kPa	------------------------- Mg m^–3 ------------------		--------------------------- % -----------------------------
CT	315.90 a	0.15 c	1.75 a	97.33 a	92.12 a	96.83 a
Δ_ref. NF (%)	+86.5	-57.14	+15.13	+9.23	+21.57	+4.89
CNF	173.30 b	0.26 b	1.60 b	92.15 b	81.79 b	94.86 b
Δ_ref. NF (%)	+2.30	-25.71	+5.26	+3.42	+7.94	+2.76
NF	169.40 b	0.35 a	1.52 b	89.10 c	75.77 c	92.31 c

Systems of use¹ 1 CT = soil with corn crop after tobacco crop under a conventional system; CNF = soil with corn crop after native field under a conventional system; NF = native field soil and NA = native area. Δref. (%): increase (+) or decrease (-) as a percentage of NF and NA. Means followed by the same small letter in the column did not differ from each other in the LSD test at the 5 % level	TOC	CFC	CAM
	----------------------------------- g kg^–1 -----------------------------------
CT	6.3 c	2.4 b	3.9 c
Δ_ref. NF (%)	-64.0	-35.1	-72.5
Δ_ref. NA (%)	-65.3	-42.9	-72.1
CNF	9.7 b	2.4 b	7.3 b
Δ_ref. NF (%)	-44.6	-35.1	-46.7
Δ_ref. NA (%)	-46.7	-42.9	-47.9

NF	17.5 a	3.7 a	13.7 a
NA	18.2 a	4.2 a	14.0 a

Escola Superior de Agricultura "Luiz de Queiroz" USP/ESALQ - Scientia Agricola, Av. Pádua Dias, 11, 13418-900 Piracicaba SP Brazil, Phone: +55 19 3429-4401 / 3429-4486 - Piracicaba - SP - Brazil
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[1] *Corresponding author <clrlima@yahoo.com.br>