Soil Organic Matter Quality in Soils With Different Levels of Manure Fertilisation

Soil	Soil use characteristics
I	For 15 years before the date of soil sampling, manure was applied annually at a dose of approximately 30 t ha⁻¹. In the years preceding sampling, maize (for silage), spring wheat and maize (for silage) were grown.
II	Manure fertilisation was performed every 4 years; the last dose was approximately 30 t ha⁻¹ 3 years prior to the date of soil sampling. In the years preceding sampling, winter wheat, rapeseed and winter wheat were grown.
III	Soil deprived of organic fertilisation in the last dozen or so years before collecting soil samples. In the years preceding the sampling, winter wheat, rapeseed and triticale were grown.

Soil	Granulometric fraction^*			Granulometric group^*	pH (1 M KCl)	SOM g · kg⁻¹
Soil	Sand	Silt	Clay	Granulometric group^*	pH (1 M KCl)	SOM g · kg⁻¹
I	44	36	20	Loam	5.24	40.7
II	31	46	23		5.45	27.2
III	35	46	19		5.17	22.2

Soil	C	H	N	O	H/C	w	A_4/6	ΔlogK
Soil	atomic %				H/C	w	A_4/6	ΔlogK
I	37.0	42.5	2.95	17.6	1.15	0.039	4.09	0.604
II	39.9	39.9	2.58	17.6	1.00	0.077	3.80	0.595
III	39.4	40.3	2.33	18.0	1.02	0.067	4.38	0.649

Soil	Unit of measure	TC	C_DEC	C_BIT	C_HS	C_FA	C_HA	C_HUMIN	C_HA/C_FA
I	g·kg⁻¹	23.6	0.51	0.32	11.9	5.01	6.89	10.9	1.38
I	% TC	100	2.16	1.36	50.4	21.2	29.2	46.2	1.38
II	g·kg⁻¹	15.8	0.25	0.90	6.80	2.81	3.99	7.80	1.42
II	% TC	100	1.58	5.70	43.0	17.8	25.3	49.4	1.42
III	g·kg⁻¹	12.9	0.23	0.63	7.00	2.61	4.39	5.00	1.68
III	% TC	100	1.78	4.88	54.3	20.2	34.0	38.8	1.68

Name and symbol of the fraction	Extraction procedure
Post decalcification fraction C_DEC	Extraction with 0.05 M H₂SO₄; extraction time 24 h; m/V = 1/50; centrifugation (g = 4000 rpm) and filtration through a cellulose filter. The carbon in the solution was determined using the oxidation-titration method
Bitumen fraction C_BIT	Extraction (ethanol + n-hexane, v/v = 1/1) in an automatic solvent extraction extractor. Bitumen mass was determined by weight. Carbon in the preparations was determined on an elemental analysis analyzer.
Humic substance fraction C_HS	Extraction with 0.1 M NaOH; extraction time = 24 h; m/V = 1/50; centrifugation (g = 4000 rpm) and filtration through a cellulose filter. The carbon in the solution was determined using the oxidation-titration method.
Fulvic acid fraction C_FA	Acidification (2.5 M H₂SO₄, pH = 1.80) of a measured portion of the 0.1 M NaOH extract. After precipitation and sedimentation of humic acids (24 h) in the solution of fulvic acids, the carbon content was determined using the oxidation-titration method.
Humic acid fraction C_HA	Calculated from the following equation: $C_{HA} = C_{HS} - C_{FA}$ {{\rm{C}}_{{\rm{HA}}}} = {{\rm{C}}_{{\rm{HS}}}} - {{\rm{C}}_{{\rm{FA}}}}
Residual (humin) fraction C_HUMIN	Calculated from the following equation: $C_{RES} = TC - (C_{DEC} + C_{BIT} + C_{HS})$ {{\rm{C}}_{{\rm{RES}}}} = {\rm{TC}} - \left( {{{\rm{C}}_{{\rm{DEC}}}} + {{\rm{C}}_{{\rm{BIT}}}} + {{\rm{C}}_{{\rm{HS}}}}} \right)