Resistance of Soil Organic Matter in “Humic A Horizons” of the Mountainous Region in the State of Rio De Janeiro

Fontana, Ademir; Pereira, Marcos Gervasio; Balieiro, Fabiano de Carvalho; Chagas, Cesar da Silva; Donagemma, Guilherme Kangussu; Oliveira, Lucienne Silva de

doi:10.1590/2179-8087.009119

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Original Article, Silviculture • Floresta Ambient. 27 (1) • 2020 • https://doi.org/10.1590/2179-8087.009119 copy

Resistance of Soil Organic Matter in “Humic A Horizons” of the Mountainous Region in the State of Rio De Janeiro

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Soils with high organic carbon content, such as those with “humic A horizon”, occur in different regions of Brazil. This study aimed to determine the quantitative and qualitative characteristics of organic matter regarding the humic A horizon under different land uses in Bom Jardim, in Rio de Janeiro State, Brazil. Samples from forest, pasture, Eucalyptus plantation, coffee cultivation, olericulture, and also passion fruit soils were sampled and analyzed. In October 2011, undisturbed samples from humic A horizons, were collected for soil density analysis. In addition, disturbed samples were collected for the determination of organic carbon (C_org) content, total carbon, humic substance fractions contents and natural abundance of ¹³Carbon (δ¹³C). Low C_org contents were observed in areas under olericulture, pasture and passion fruit cultivation. The fulvic acid fraction was higher than other fractions, regardless of land use. The small variability in δ¹³C indicated maintenance of original C_org and suggest high resistance of Soil Organic Matter in humic A horizons.

Keywords:
organic carbon; humic substances; isotopic composition

Uses	Horizon	Depth	C_org	FAF	HAF	HUMIN	HAF/FAF
Uses	Horizon	cm	g kg^-1	^__________%^__________			-
Eucalyptus plantation	Ap	0-18	30.1	17	23	46	1.4
	A1	18-45	22.8	12	26	45	2.1
	A2	45-85	22.8	12	15	39	1.3
	AB	85-100	14.8	11	16	39	1.4
Olericulture	Ap	0-40	15.6	22	20	29	0.9
	A1	40-65	10.5	25	14	26	0.6
	A2	65-80	11.1	11	16	66	1.5
	AB	80-102	10.9	25	23	53	0.9
Pasture	Ap	0-23	15.9	15	18	26	1.2
	A1	23-58	11.1	22	13	46	0.6
	A2	58-95	11.0	15	18	25	1.2
Coffee cultivation	Ap	0-19	23.1	20	13	61	0.6
	A1	19-32	20.5	18	13	43	0.7
	A2	32-60	20.6	9	13	31	1.5
	AB	60-79	12.9	26	20	25	0.8
Passion fruit	Ap	0-20	17.2	13	13	31	1.0
	A1	20-38	15.8	15	15	29	1.0
	A2	38-61	17.2	24	26	11	1.1
	AB	61-85	10.9	15	23	43	1.6
Forest	A1	0-22	27.3	8	6	79	0.8
	A2	22-40	27.1	8	6	76	0.7
	A3	40-65	22.1	10	9	57	0.9
	AB	65-75	12.8	13	15	49	1.1

Uses	Horizon	TC	BD	Horizon Stock	Total Stock
Uses	Horizon	g kg^-1	Mg m^-3	Mg ha^-1
Eucalyptus plantation	Ap	45.0	0.79	63.99	284.69
	A1	31.4	0.82	69.52
	A2	30.3	0.92	111.50
	AB	22.8	1.16	39.67
Olericulture	Ap	19.6	1.07	83.89	201.47
	A1	18.5	1.09	50.41
	A2	16.8	1.28	32.26
	AB	12.8	1.24	34.92
Pasture	Ap	19.2	1.25	55.20	176.26
	A1	13.3	1.15	53.53
	A2	16.9	1.08	67.53
Coffee cultivation	Ap	26.6	1.08	54.58	208.10
	A1	25.3	1.13	37.17
	A2	23.0	1.21	77.92
	AB	15.8	1.28	38.43
Passion fruit	Ap	22.4	1.01	45.25	162.64
	A1	20.6	1.00	37.08
	A2	22.7	0.91	47.51
	AB	13.4	1.02	32.80
Forest	A1	32.1	0.89	62.85	185.51
	A2	29.8	0.94	50.42
	A3	22.4	1.02	57.12
	AB	12.7	1.19	15.11

Instituto de Florestas da Universidade Federal Rural do Rio de Janeiro Rodovia BR 465 Km 7, CEP 23897-000, Tel.: (21) 2682 0558 | (21) 3787-4033 - Seropédica - RJ - Brazil
E-mail: floram@ufrrj.br

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[1] Ademir Fontana Embrapa Solos – CNPS, Rua Jardim Botânico, CEP 22460-000, Rio de Janeiro, RJ, Brasil e-mail: ademir.fontana@embrapa.br