Agrovoc descriptors: soil fertility, nutrient availability, chemical composition, fertilizer application, mineral content, inorganic fertilizers, farmyard manure, straw, humus, soil organic matter, nitrogen
Agris category code: P35, P33
Soil organic matter content according to different management system within
long-term experiment
Monika CVETKOV1, Igor ŠANTAVEC2, Darja KOCJAN AČKO3, Anton TAJNŠEK4
Received October 12, 2009; Accepted January 19, 2010. Prispelo 12. oktobra, 2009; sprejeto 19. januarja, 2010.
ABSTRACT
IZVLEČEK
Within the long-term field experiments at IOSDV Rakičan, Slovenia, the impact of organic matter management system and mineral nitrogen fertilization on the soil organic matter content was studied in the period 1994-2008. The annual balance of Corg was calculated on the basis of the quantity of added organic fertilizers ("Bavarian method", "VDLUFA method"), while the "Swiss method" also consider the quantity of Corg in the topsoil in the calculation. The following management systems were selected: system A - no organic matter, system B - farmyard manure ploughing in, system C -straw/catch crop ploughing in. Four different mineral N rates (N0, N1, N2, N3) were evaluated. In 2008 the Corg content in topsoil (0-25 cm) was measured according to ISO 10694. Farmyard manure (FYM) fertilization significantly influenced the content of Corg, while the straw application did not result in the significant increase of Corg content. Mineral nitrogen fertilization did not impact Corg content within system A. In system B and system C positive effect of nitrogen fertilization
VSEBNOST ORGANSKE SNOVI V TLEH V ODVISNOSTI OD NAČINA GOSPODARJENJA ZNOTRAJ TRAJNEGA POSKUSA
V statičnem poskusu IOSDV Rakičan, Slovenija smo preučevali vpliv gospodarjenja z organskimi gnojili in vpliv gnojenja z mineralnimi dušikom na vsebnost organske snovi v tleh v letih 1994 do 2008. Letna bilanca Corg je bila izračunana na podlagi količin dodanih organskih gnojil pri „Bavarski metodi" in „ VDLUFA metodi", medtem ko se je pri „ Švicarski metodi" v izračunih upoštevalo tudi stanje Corg v tleh. Vključeni sistemi gospodarjenja so bili: sistem A -gospodarjenje brez organskega gnojenja, sistem B - gnojenje s hlevskim gnojem, sistem C - zaoravanje slame/podorin. Preučevane so bile štiri stopnje gnojenja z mineralnim dušikom: N0, N1, N2 in N3. V letu 2008 je bila izmerjena vsebnost Corg v globini od 0 do 25 cm po standardu ISO 10694. Gnojenje s hlevskim gnojem je značilno povečalo
on the Corg content was detected. However, statistically vsebnost Corg, medtem ko gnojenje s slamo ni imelo takšnega
significant impact of mineral N on a higher Corg content was not determined. All three methods underestimated the actual analysed results, although, we can determine the "Swiss method" as the most precise and appropriate for this site-specific location.
Key words: organic fertilizers, farmyard manure, straw, N fertilizers, Corg content, humus balance, humus balance calculation methods
vpliva. V sistemu brez organskih gnojil gnojenje z mineralnim dušikom ni doprineslo k povečanju vsebnosti Corg. Kljub pozitivnemu vplivu gnojenja z mineralnim dušikom na vsebnost Corg v sistemu B in C, pa vpliv ni bil statistično značilen. Izračuni vseh treh metod podcenijo dejanske rezultate laboratorijskih analiz posameznega vzorca. Še najbolj se omenjenim rezultatom približajo vsebnosti Corg, izračunane s „Švicarsko metodo", zato lahko povzamemo, da je slednja najbolj primerna za določitev Corg za preučevano lokacijo.
Ključne besede: organska gnojila, hlevski gnoj, slama, mineralni dušik, vsebnost Corg, bilanca
humusa, metode humusa
izračunavanja bilance
1	University of Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, SI-1111 Ljubljana, e-mail: monika.kunaver@bf.uni-lj.si
2	ibid., igor.santavec@bf.uni-lj.si
3	ibid., darja.kocjan@bf.uni-lj.si
ibid., tone.tajnsek@bf.uni-lj.si
4
1 INTRODUCTION
Land use and agricultural management practices such as crop rotation, soil tillage and organic amendment, depending on the site-specific conditions can affect soil organic matter (SOM). Changes in the organic carbon (Corg) content in soil occur almost exclusively in its decomposable part. The tendency of the decomposable carbon (Cdec) changes also depends on its initial level. Application of the same fertilization and cropping system can cause a decrease of the SOM content if its initial level was high, as well as an increase of the SOM if its initial level was low (Körschens, 2002). As the organic substances interact with clay in soil to form complexes and micro-aggregates, which make the organic matter less accessible to decomposers, Corg tend to increase and mineralization rate decrease with the clay content (Bosatta and Ägren, 1997; Körschens, 2004; Diekow et al., 2005). The content of organic carbon (Corg) is controlled by changes in management via the annual input of organic matter and the rate at which decays (Jenkinson et al., 1999).
The amount of SOM is generally higher in the fertilized soils than in the unfertilized soils (Ellmer et al., 2000; Hoffmann et al., 2002; Berecz et al., 2004; Goyal et al., 2006). Data from several long-term comparative experiments on the effect of FYM and mineral fertilization prove that FYM increases the organic matter content of the soil to a greater extent than mineral fertilization (Körschens, 1997; Kuzyakov and Domanski, 2000; Berecz et al., 2004; Brodowski et al., 2007; Šimon, 2007). On the other hand organic C stocks had barley changed in response to very considerable changes in management in the experiment by Jenkinson et al. (1999). In case of omitted mineral N fertilization, the humus content in the soil decreased rapidly (Stumpe et al., 2000; Beschow and Merbach, 2004; Winkelmann et al., 2006). Incorporation of harvest residues also
increased Corg content in soil (Buyanovsky and Wagner, 1998; Triberti et al., 2008). Not only the quantity, also the structure of SOM varies depending on the rate of fertilizer (Ellerbrock et al., 1999; Dorado et al., 2003).
By using methods of calculating the balance of humus we are given an opportunity to control the SOM content in arable soils in order to achieve higher yields and simultaneously avoid environmental pollution. Since the most Corg is bound in soil humic matter, the mineralization and humification of plant carbon in soil should be monitored (Filip and Kubat, 2004). There are several humus balance calculation methods and models, however, in many models, humification is not considered as a part of the process of transformation of organic debris into humus, and the role of humus in the kinetics of this process is evidently underestimated (Chertov et al., 2007). Three humus balance calculation methods, which take into account a humification and mineralization rates and are believed to be appropriate for European Central site-conditions are investigated: "Swiss method" determined by Diez and Krauss (1992), the "Bavarian method" determined by Bavarian working group (Anonymous, 1998) and the "VDLUFA method" determined by Körschens et al. (2004).
The aim of our study was to examine, with the application of mentioned methods, the impact of organic and mineral fertilization on the humus content in the soil according to particular crop rotation at ISODV Rakičan location. As the soil analyses were conducted every year since the establishment of the trial, the results calculated by each method could be compared with the analysed results, therefore a most appropriate method for this site-specific condition could be selected.
2 MATERIAL AND METHODS
2.1 Experimental layout
As part of the "International Long-term Experiments for Investigating the Effect of Organic and Inorganic Fertilizers" (IOSDV), field experiment was set up at Rakičan, Slovenia (46°38'N, 14°11'E, Pannonian climate, sandy silt) in 1993. The trial was set up as a permanent experiment related to crop rotation with ten different fertilization combinations as a block trial with three repetitions. First, the trial area was divided into three plots, on which each year crops were sown in the following order: corn, winter wheat, barley. Each plot was further divided into two subplots, on which different systems of fertilization with organic management were studied. Each subplot thus represented five variants differing according to the rate of fertilization with mineral nitrogen in the three
repetitions. The basic plot size was 30 m2 (5 x 6 m). Ten different treatments were included in the investigation:
-	management system with no organic fertilizers (system A) and two different mineral rates (N0, N3),
-	management system with farmyard manure (FYM) ploughing in (system B) and four different mineral N rates (N0, N1, N2, N3),
-	management system with straw ploughing in (system C) and four different mineral N rates (N0, N1, N2, N3).
Fertilizing plan for the nutrition of arable crops is shown in Table 1. Fertilization with phosphor and potassium was uniform for all mineral nitrogen rates (N0=0 N kg/ha, N1=73 N kg/ha, N2=147 N kg/ha, N3= 220 N kg/ha): 75 kg/ha P2O5 and 160 kg/ha K2O. At the harvest time, yield and straw quantities were measured for
each plot. After harvesting every year soil samples from each plot were taken at a depth of 0-25 cm.
Table 1: Management systems, mineral N fertilization with regard to the crop, the average amount of mineral N in the three-year crop rotation (N-minaver.) at IOSDV Rakičan location
		N-min	Maize	Wheat	Barley/	N-minaver.
		rates/	(kg/ha N)	(kg	(kg	(kg
		Treatment		/ha N)	/ha N)	/ha N)
-<	No organic		/	/	/	
fi	fertilizers					
o 5«		NO (ANO)	0	0	0	0
in		N3 (AN3)	300	195	165	220
	FYM ploughing in		30 t/ha FYM*	/	/	
ca	(t/ha)					
S		NO (BN0)	0	0	0	0
5«		N1 (BN1)	100	65	55	73
XJì		N2 (BN2)	200	130	110	147
		N3 (BN3)	300	195	165	220
	Straw/catch crop		Barley straw +	Maize	Wheat	60**
U	ploughing in (t/ha)		fodder radish	straw	straw	
S		NO (CN0)	0	0	0	0
5«		N1 (CN1)	100	65	55	73
m		N2 (CN2)	200	130	110	147
		N3 (CN3)	300	195	165	220
* FYM is applied every third year.
** Mineral N is added after barley and before fodder radish is sown, every third.
2.2 Weather and soil conditions
The soil type, soil properties and some climatic characteristics of the experimental site are listed in Table 2 (Tajnšek, 2003). Annual precipitation and the average
annual temperature for the period 1994-2008 in comparison with the long-term average precipitation and the long-term average temperature for the period 1960-1990 are shown in Figure 1.
Table 2: Soil properties of the experimental site (Tajnšek, 2003)
Long. East1	Lat. North2	Prec3. (mm)	Temp4. (°C)	Soil type (FAO classification)	Clay (<2.0^m) (%)	pH (KCl)	C ^org (%)	N org (%)	C/N Ratio
14°11'	46°38'	814	9.2	Eutric Fluviosol (ELe)	14.67	7.04	0.926	0.098	9.5
'Longitude; 2 Latitude; 3 Precipitation, the long-term average precipitation in the period 1961-1990; 4 Temperature, the long-term average temperature in the period 1961-1990
Weather conditions for IOSDV Rakičan
1200
1000
800
.2 c
ÜE 600
400
200
• •
14
12
10
8 3
SF
a ~ 6 EE
0	I I I I I I 1 I 1 11 I I I I I I 11 I 1 0
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Years
]P (61-90) ] P (94-08) -T (61-90) T (94-08)
Figure 1: Annual precipitation and the average annual temperature for the period 1994-2008, the long-term average precipitation (1961-1990) and the long-term average temperature (1961-1990) for the IOSDV Rakičan (weather station Murska Sobota) location
2.3 Humus balance calculation methods
In our investigation, there are three methods of calculating the balance of humus involved:
- The method determined by Diez and Krauss (1992) named as the "Swiss method" or "S". The annual balance is calculated on the basis of the ploughed-in quantity of organic matter (manure, straw, catch crop, harvest residues) with the corresponding humification coefficient, taking into account the quantity of humus in the soil (H) with the appropriate mineralization coefficient. Results are given in
matter inputs: manure, straw and catch crop. The organic matter decay is represented in the coefficients of depleting and increasing crop species. While for the major intensive forms of agricultural managements the lower values of annual humus balance under specific crop are recommended by DirektZahlVerpfIV (Körschens et al., 2004), we have chosen the lower values for further calculation. Results are given in the Corg value (t/ha), which is calculated on the basis of content Humus-C (kg/ha) multiplied by factor 0.001 (kg/ha^t/ha).
the Corg value (t/ha), which is calculated on the basis of 2. 4 Chemical analyses humus content (t/ha) multiplied by factor 0.58. The method determined by Bayerische Landesanstalt für Bodenkultur und Pflanzenbau, Freising-München (Anonymous, 1998) named as the »Bavarian method« or »B«. The humus balance is calculated on the basis of humification rate of individual crop in crop rotation, taking into account the quantity of added organic matter: manure, straw and catch crop. In this method humification factor varies due to soil texture, therefore at IOSDV Rakičan a humification factors for soil type sandy silt (Eutric Fluviosol [ELe]) are chosen. Results are given in the Corg value (t/ha), which is calculated on the basis of humus content (dt/ha) multiplied by factor 0.58 (humus
In the year of the establishment of the experiment (1993), as well as in all subsequent years, the soil analyses were conducted at the laboratories UFZ Leipzig-Halle, Germany (Tajnšek, 2003). The Corg content was determined according to ISO 10694, 1996-08. In the calculation of humus balance we considered initial value of Corg content in 1993.
content^Corg) and by factor 0.1 (dt/ha^t/ha). The method determinated by working group Körschens et al. (2004) named as the »VDLUFA method« or »V«. With the "VDLUFA method" an organic matter surplus is calculated by addition of specific humification coefficients using for organic matter depleting crop species and for the organic
2.5 Processing of statistical data
Statistical analysis was conducted with the Statgraphics Plus 4.0 program. Before analysis each treatment was tested for homogeneity of treatment variances. If variances were not homogeneous, data was transformed to log (Y) before ANOVA. Multifactor ANOVA was used in order to analyze the effect of different management systems on the humus content in the soil. Differences among treatments were detected by Duncan's Multiple Range Test (p < 0.05). Data is presented as untransformed means±SE.
4
2
3 RESULTS
3.1 The humus balance in the period 1993-2008
Results showing the Corg content of the analysed soil samples at IOSDV Rakičan in the beginning of the trial and the Corg content calculated by different methods for the year 2008 are given in Table 3. The initial value of Corg in 1993 was 37.27 t/ha Corg. FYM fertilization significantly influenced the content of Corg, while the straw application did not result in a significant increase of the Corg content. Results show that mineral N fertilization had no significant impact within all three management systems.
content in the management without organic fertilization (system A). Moreover, with the application of the average amount of N in a three-year crop rotation (220 kg/ha N), the Corg content resulted in a decrease of 2.3 %, i.e. 0.94 t/ha Corg. This is comparable to the results of the experiment by Beschow and Merbach (2004), where a comparison of the highest mineral nitrogen (N) with no-N resulted in a merely 1.2-fold higher value of the Corg content in the topsoil. Likewise, in the case of mineral N fertilization, the content of Corg was slightly higher (1.4 to 1.5 %) than without any N fertilization (1.3 %) (Stumpe et al., 2000; Triberti et al., 2008).
As demonstrated in Table 3, mineral nitrogen fertilization did not contribute to an increase of the Corg
Table 3:	Corg content (t/ha) of analysed soil samples in 1993 and 2008, the Corg content (t/ha) in 2008,
calculated by »Swiss« (S), »Bavarian« (B) and »VDLUFA« (V) methods and the difference between analysed and calculated Corg content (t/ha) in 2008 for ten different treatments (IOSDV Rakičan)
Tre.	Corg1993	Corg2008(anal.)		Corg2008(cal.)		Corg2008(anal.) - C		org2008(cal.)
	(anal.)	(t/ha)		(t/ha)			(t/ha)	
	(t/ha)							
			»S«	»B«	»V«	»S«	»B«	»V«
AN0		41.73± 1.28	37.06±0.02	33.28±0.00	31.67±0.00	4.67	8.45	10.06
		a*	a	a	a			
AN3		40.79±1.10	37.26±0.08	33.28±0.00	31.67±0.00	3.53	7.51	9.12
		a	a	a	a			
BN0		46.96±1.36	38.19±0.02	36.76±0.00	37.67±0.00	8.77	10.20	9.29
		bcde	c	b	b			
BN1		48.97±2.16	38.25±0.02	36.76±0.00	37.67±0.00	10.72	12.21	11.30
		de	cd	b	b			
BN2		49.37±0.58	38.37±0.04	36.76±0.00	37.67±0.00	11.00	12.61	11.70
	37.27	e	e	b	b			
BN3		47.63±0.75	38.35±0.00	36.76±0.00	37.67±0.00	9.28	10.87	9.96
		cde	de	b	b			
CN0		40.79±1.68	37.90±0.11	37.63±0.06	37.61±0.08	2.89	3.16	3.18
		a	b	c	b			
CN1		42.53±1.36	37.92±0.07	38.67±0.16	39.08±0.23	4.61	3.86	3.45
		ab	b	d	c			
CN2		44.41±1.10	37.94±0.10	39.27±0.18	39.91±0.25	6.47	5.14	4.50
		abcd	b	e	d			
CN3		43.74±2.11	38.18±0.03	39.90±0.03	40.80±0.04	5.56	3.84	2.94
		abc	c	f	e			
1 xpovp.|						6.75	7.79	7.55
a-f The same letter in the column indicates thet there is no significant difference among treatments (Duncan Multiple Range Test, P<0.05).
In the system with FYM (system B), Corg was were not significant. The Corg content increased by significantly higher in all the treatments when compared 5.23 t/ha (BN0), 7.24 t/ha (BN1), 7.64 t/ha (BN2) and to AN0 and AN3. The application of mineral N 5.90 t/ha (BN3). The highest amount of mineral N increased the Corg content; however, the differences (BN3) combined with 10 t/ha.yr FYM resulted in a
slightly lower Corg content. Ellmer reported that the total carbon content between 600 and 800 mg/100g can be achieved by organic fertilization (15 t/ha.yr FYM) and with appropriate crop rotation (Ellmer et al., 2000). An average demand for FYM was determined to be 10 t/ha in a year (Körschens et al., 2004).
In the management with ploughing in of straw (system C), there was a decrease of the Corg content by 0.94 t/ha in the treatment without mineral N (CN0). Although the Corg content increased with higher fertilizer rates of mineral N, a significant impact of N fertilizing could not be confirmed among the treatments. The Corg content increased by 0.80 t/ha (CN1), 2.68 t/ha (CN2) and 2.01 t/ha (CN3). In the experiment by Triberti et al. (2008), the SOC stock did not change in unfertilized plot and N fertilized plot, while it increased at a mean rate of 0.16, 0.18 and 0.36 t/ha in a year with the incorporation of residues, slurry and manure.
was confirmed. Compared to the unfertilized plot, the FYM application resulted in a 8.2 % higher total organic carbon content than the equivalent NPK fertilization according to Hoffmann et al. (2006). In the experiment by Berecz et al. (2004), both types of organic manuring (FYM, straw or green manure) resulted in significantly higher Corg contents compared to the mineral N fertilization without manuring or incorporation of crop residues.
Application of FYM combined with mineral N resulted in the highest Corg content among all the treatments. This is in accordance with the results given by other authors (Filip and Kubat, 2004; Goyal et al., 2006). The increase of the C content in the soil during a 50-year period required a four times (e.g. FYM on loamy soil) to 12 times (e.g. straw fertilization on sandy soil) higher input C, depending on the local conditions and the type of primary organic matter (Körschens et al., 2004).
In both systems (system B, system C), the application of the highest amount of mineral N (BN3, CN3) resulted in
a lower Corg content.
The contribution of FYM to the maintenance of the Corg content is greater than the input of straw. According to AN0, where the Corg content amounted to 41.73 t/ha, the Corg content in system B increased in the range of 5.23 to 7.64 t/ha Corg, i.e. 12.5 % to 18.3 %. In system C, where no mineral N was added (CN0), the Corg content decreased by 0.9 t/ha, while in
increased by 0.80 to 2.68 t/ha Corg, %.
other treatments it i.e. by 1.9 % to 6.4
According to different management system, the same fertilizing rate of mineral N significantly influenced the Corg content only in system B. In comparison with AN0, the change of the Corg content was higher for 12.5 % in BN0, while in system C the Corg content decreased for 2.3 % (CN0). When comparing the treatments with the highest mineral N rate, an increase of the Corg content by 16.7 % in BN3 and by 7.2 % in CN3 according to AN3
3.2 Calculated and analysed Corg content in 2008
In calculation by "Swiss method", the Corg content increased by application of mineral nitrogen (AN3). The results calculated by "Bavarian method" and "VDLUFA method" within the systems are equal; this was expected as the calculation takes into account the amount of added organic matter which does not differentiate between treatment AN0 and AN3. As it is seen from figure 2, method which most closely approximated the analysed Corg content in the system with no organic matter was "Swiss" method. The difference between analysed Corg2008 content and calculated Corg2008 content is called deviation from analysed Corg content. Deviation from analysed Corg content was higher by using "Bavarian" and " VDLUFA" methods, deviation ranged
"Bavarian" method and VDLUFA" method.
from 7.51 to 8.45 t/ha Corg at
from 9.12 to 10.06 t/ha Corg at
Figure 2: Corg content of analysed soil samples (CorgM), Corg content, calculated by »Swiss« (CorgS), »Bavarian« (CorgB) and »VDLUFA« (CorgV) methods in 2008 for two treatments in management system with no organic fertilizers (IOSDV Rakičan)
Rakičan, 2008
46 -,
44
42
_ 40 co
^ 38
E?
o
U 36 34 -32 -30
ANO
AN3
□	Corg S
o	Corg B
A	Corg V
X	Corg M
The application of mineral nitrogen in system with FYM statistically increased Corg content in results calculated by "Swiss" method at BN2 and BN3, while within treatments in "Bavarian" and "VDLUFA" methods there were no differences. Deviation from analysed Corg content ranged from 8.77 to 11.00 t/ha
Corg at "Swiss", from 10.20 to 12.61 t/ha Corg at "Bavarian", from 9.29 to 11.70 t/ha Corg at "VDLUFA" method. For this system method which most closely approximated the analysed Corg content was again "Swiss" method (Figure 3).
Rakičan, 2008
54 52 50 48 46 44 42 40 38 36 34 32 30
g ♦
BN0
g ♦
BN1
is ♦
BN2
& ♦
BN3
□	Corg S
o	Corg B
A	Corg V
X	Corg M
Figure 3:	Corg content of analysed soil samples (CorgM), Corg content, calculated by »Swiss« (CorgS),
»Bavarian« (CorgB) and »VDLUFA« (CorgV) methods in 2008 for four treatments in management system with FYM ploughing in (IOSDV Rakičan )
50
48
46
44
£ 42
S" 40 t»
S 38
36 34 32 30
Rakičan, 2008
5
o
CN0
CN1
CN2
CN3
□	Corg S
♦	Corg B
A	Corg V
X	Corg M
Figure 4: Corg content of analysed soil samples (CorgM),
Corg content,
calculated by »Swiss« (CorgS), »Bavarian«
(CorgB) and »VDLUFA« (CorgV) methods in 2008 for four treatments in management system with straw ploughing in (IOSDV Rakičan)
In the system with straw ploughing in application of mineral nitrogen significantly increased the Corg content in »Bavarian« and »VDLUFA« method, while in »Swiss« method the impact of mineral nitrogen was notices only in treatment with the highest mineral rate (CN3). In this system the most precise method seemed to be »VDLUFA« method, where the deviation from
analysed Corg ranged from 2.94 to 4.50 t/ha Corg (Figure 4). Using "Swiss" method the mentioned deviation ranged from 2.89 to 6.47 t/ha Corg, using "Bavarian" method it was in interval from 3.16 to 5.14 t/ha Corg.
4 CONCLUSIONS
After the fifteen-year experiment at IOSDV Rakičan, the application of organic fertilizers (farmyard manure, straw) influenced the Corg content. However, the impact was significant only in the system with farmyard manure. Mineral nitrogen fertilization contributed to an increase of the Corg content in all three management systems (system A, system B, system C). However, the increase was not significant. With the application of mineral nitrogen in the system with no organic fertilizers the Corg content resulted in a decrease of 2.3%, i.e. 0.94 t/ha Corg. In the system with farmyard manure ploughing in the Corg content increased by 5.23 t/ha (BN0), 7.24 t/ha (BN1), 7.64 t/ha (BN2) and 5.90 t/ha (BN3). In the system with straw ploughing in the
Corg content increased by 0.80 t/ha (CN1), 2.68 t/ha (CN2) and 2.01 t/ha (CN3). The comparison of Corg contents calculated by different humus balance methods in 2008 shows that all three methods underestimated the actual analysed results. "Swiss" method's results most closely approximated the analysed Corg in the systems A and system B, while in the system C the most appropriate method was "VDLUFA". As the average of absolute values of deviations from analysed Corg contents was the lowest by using "Swiss" method (6.75 t/ha Corg), we can conclude that this method is most appropriate method for this site-specific location.
5 ACKNOWLEDGEMENT
This work is part of the "Genetics and modern technologies of agricultural plants" programme (P4-
0077) funded by the Slovenian Research Agency (ARRS).
6 REFERENCES
Anonymous, (1998): Leitfaden für die Düngung von Acker-und Gründland, 6. uberarbeitete Auflage 1997, Bayerische Landesanstalt für Bodenkultur und Pflanzenbau, Freising - München: 9-12 p.
Berecz, K., Kismànyoky, T., Debreczeni, K. (2004): Studying the effect of organic matter recycling combined with mineral N fertilization in long-term field and model pot experiments. Archives of Agronomy and Soil Science, 50: 65 - 72.
Beschow, H., Merbach, W. (2004): Entwicklung der Organischen Bodensubstanz (OBS) auf Löss in Abhängigkeit von unterschiedlicher Düngung am Beispiel des Bodenbildungsversuches in Halle/Saale. Archives of Agronomy and Soil Science, 50: 59 - 64.
Bosatta, E., Ägren, G.I. (1997): Theoretical analyses of soil texture effects on organic matter dynamics. Soil Biology and Biochemistry, 29: 1633 - 1638.
Brodowski, S., Amelung, W., Haumaier, L., Zech, W. (2007): Black carbon contribution to stable humus in German arable soils. Geoderma, 139: 220 - 228.
Buyanovsky, G.A., Wagner, G.H. (1998): Changing role of cultivated land in the global carbon cycle. Biology and Fertility of Soils, 27: 242 - 245.
Chertov, O.G., Komarov, A.S., Nadporozhskaya, M.A. (2007): Analysis of the Dynamics of Plant Residue Mineralization and Humification in Soil. Eurasian Soil Science, 40: 140 - 148.
Diekow, J., Mielniczuk, J., Knicker, H., Bayer, C., Dick, D.P., Kögel-Knabner, I. (2005): Carbon and nitrogen stocks in physical fractions of a subtropical Acrisol as influenced by long-term no-till cropping systems and N fertilisation. Plant and Soil, 268: 319 - 328.
Diez, T., Krauss, M. (1992): Berechnung von Humisbilanzen, SuB 06: III-9-III-11.
Dorado, J., Zancada, M.-C., Almendros, G., López-Fando, C. (2003): Changes in soil properties and humic substances after long-term amendments with manure and crop residues in dryland farming systems. Journal of Plant Nutrition and Soil Science, 166: 31 - 38.
Ellmer, F., Peschke, H., Köhn, W., Chmielewski, F.-M., Baumecker, M. (2000): Tillage and fertilizing effects on sandy soils. Review and selected results of long-term experiments at Humboldt-University Berlin. Journal of Plant Nutrition and Soil Science, 163: 267 - 272.
Ellerbrock, R.H., Höhn, A., Rogasik, J. (1999): Functional analysis of organic matter as affected by long-term manurial treatment. European Journal of Soil Science, 50: 65 - 71.
Filip, Z., Kubàt, J. (2004): Mineralisation and humification of plant matter in soil samples as a tool in the testing of soil quality. Archives of Agronomy and Soil Science, 50: 91
-	97.
Goyal, S., Sakamoto, K., Inubushi, K., Kamewada, K. (2006): Long-term effects of inorganic fertilization and organic amendments on soil organic matter and soil microbial properties in Andisols. Archives of Agronomy and Soil Science, 52: 617 - 625.
Hoffmann, S., Csitàri, G., Hegedüs, L. (2002): The humus content and soil biological properties as a function of organic and mineral fertilization. Archives of Agronomy and Soil Science, 48: 141 - 146.
Hoffmann, S., Schulz, E., Csitàri, G., Bankó, L. (2006): Influence of mineral and organic fertilizers on soil organic carbon pools. Archives of Agronomy and Soil Science, 52: 627 - 635.
ISO 10694, 1996-08 Soil quality - Determination of organic and total carbon after dry combustion (elementary analysis).
Jenkinson, D.S., Harris, H.C., Ryan, J., McNeill, A.M., Pilbeam, C.J, Coleman, K. (1999): Organic matter turnover in a calcareous clay soil from Syria under a two-course cereal rotation. Soil Biology and Biochemistry, 31: 687 - 693.
Körschens, M. (1997): Abhängigkeit der Organischen Bodensustanz (OBS) von Standort und Bewirtschaftung sowie Ihr Einfluss auf Ertrag und Bodeneigenschaften. Archives of Agronomy and Soil Science, 41: 435-463.
Körschens, M. (2002): Importance of soil organic matter (SOM) for biomass production and environment (a review). Archives of Agronomy and Soil Science, 48: 89
-	94.
Körschens, M. (2004): Soil organic matter and environmental protection. Archives of Agronomy and Soil Science, 50: 3 - 9.
Körschens, M., Rogasik, J., Schulz, E., Böning, H., Eich, D., Ellerbrock, R., Franko, U., Hülsbergen, K.-J., Köppen, D., Kolbe, H., Leithold, G., Merbach, I., Peschke, H., Pry stav, W., Reinhold, J., Zimmer, J. (2004): Humusbilanziehrung - Methode zur Beurteilung und Bemessung Humusversorgung von Ackerland. Verband Deutscher Landwirtschaftlichcher Untersuchungs- und Forschungsnastalten (VDLUFA) (ed.): 12 p.
Kuzyakov, Y., Domanski, G. (2000): Carbon input by plants into the soil. Review. Journal of Plant Nutrition and Soil Science, 163: 421 - 431.
Stumpe, H., Wittenmayer, L., Merbach, W. (2000): Effects and residual effects of straw, farmyard manuring, and
mineral fertilization at Field F of the long-term trial in Halle (Saale), Germany. Journal of Plant Nutrition and Soil Science, 163: 649 - 656.
Simon, T. (2007): Quantitative and qualitative characterization of soil organic matter in the long-term fallow experiment with different fertilization and tillage. Archives of Agronomy and Soil Science, 53: 241 - 251.
Tajnšek, A. (2003): Vsebnost humusa in nekatere fizikalne lastnosti tal v odvisnosti od gnojenja z organskimi gnojili in dušikom v IOSDV Jable in IOSDV Rakičan. In: Deset let poskusov IOSDV v Sloveniji, Jable in
Rakičan 1993-2003. Zbornik posveta. Tajnšek, A., Čeh Brežnik, B., Kocjan Ačko, D. (ur.) Ljubljana: 25-34.
Triberti, L., Nastri, A., Giordani, G., Comellini, F., Baldoni, G., Toderi, G. (2008): Can mineral and organic fertilization help sequestrate carbon dioxide in cropland? European Journal of Agronomy, 29: 13 - 20.
Winkelmann, W., Ellmer, F., Zeitz, J. (2006): Einfluss differenzierter organisch-mineralischer Düngung auf die partikuläre organische Substanz des Bodens. Archives of Agronomy and Soil Science, 52: 365 - 376.