SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION AND SOIL MICROBIOLOGICAL ACTIVITY UNDER CONDITIONS OF VARIED CROP ROTATION SYSTEMS AND FERTILIZATION

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1 POLISH JOURNAL OF SOIL SCIENCE VOL. XL/ PL ISSN Soil Fertilization KRYSTYNA KONDRATOWICZ-MACIEJEWSKA* SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION AND SOIL MICROBIOLOGICAL ACTIVITY UNDER CONDITIONS OF VARIED CROP ROTATION SYSTEMS AND FERTILIZATION Received November 3, 2006 Abstract. The long-term effects were investigated of crop rotation systems (enriching and depleting soil with humus) as well as fertilisation with farmyard manure and mineral nitrogen on the susceptibility of soil organic matter to oxidation and soil biological activity. It was found that crop rotation enriching the soil with humus produced organic matter less susceptible to oxidation than those depleting the soil with humus, independent of the manure used. Fertilisation with nitrogen and manure resulted in an increase of microbial populations and a higher enzymatic activity in soil. The site conditions and agrotechnical measures significantly affect the chemical and biochemical parameters of soil. Simplified rotation of crops and intensive use of chemicals can impair the biological and energy equilibrium of soil agro-ecosystems. If the quality and quantity of humus is decisive for soil fertility, the main tasks of the user should be to protect humus resources in the soil and to maintain them at the highest possible level. It is also necessary to monitor the status of soil fertility in terms of its biological indices, such as quantitative and qualitative composition of the microorganisms in the soil environment [14]. Microorganisms are direct consumers of biogenic elements (carbon, nitrogen and phosphorus), being at the same moment their reservoir and labile source. Soil microorganisms play a key role in the processes of decomposition and mineralisation of organic matter. The course of enzymatic processes in soil is usually very difficult to study because they are affected by many different factors active in the soil environment. The enzymatic activity in various types of soils changes under the influence of *K. Kondratowicz-Maciejewska, DSc.; University of Technology and Life Sciences, Department of Environmental Chemistry, Bernardyñska 6, Bydgoszcz, Poland.

2 90 K. KONDRATOWICZ-MACIEJEWSKA their physical and chemical properties and the soil horizon. Moreover, changes in the enzyme activities depend on the microbial species composition, plant cover and plant vegetation period, all of which are connected with the accumulation of substrates for reactions carried out by enzymes [3]. For this reason a model of the chemical oxidation of humus with potassium manganate (VII) in a neutral solution was proposed to assess the quantitative changes occurring in the humus as an effect of various agrotechnical treatments [10]. According to many authors, the humus of soils permanently fertilized with organic fertilisers is more susceptible to oxidation than after the exclusive use of minerals [5, 6]. The supply of fresh organic matter to soil creates conditions for a higher susceptibility of humus to mineralisation processes as well as a higher concentration of more readily-oxidised fractions. The objective of the study was to assess the effects of agrotechnical treatments, such as crop rotation and fertilisation, on the microbiological activity of the soil as well as the susceptibility of its organic matter to oxidation. MATERIALS AND METHODS Soil samples were collected from the top soil (0-25 cm) of a long-term static experiment started in 1980 at the Grabów Experimental Station, Institute of Soil Science and Plant Cultivation (IUNG), Pu³awy, on a soil of light loamy sand texture, very good for growing rye, of bonitation class IVa, Albic Luvisols according to WRB (1998). The field experiment was carried out as a three-factor system: Factor I: crop rotation: A without plants considered to enrich soil with humus (potato winter wheat spring barley corn), and B with plants promoting formation of soil humus (potato winter wheat + mustard as an aftercrop for ploughing barley with companion crop mixture of clover with grasses). Factor II: differentiated fertilisation with farmyard manure used under potato (s: 0, 20, 40, 60 and 80 t ha -1 ). Factor III: differentiated fertilisation with mineral nitrogen: N0 no nitrogen; N1 170 kg N ha -1 in crop rotation A and 275 kg N ha -1 in crop rotation B; N2 340 kg N ha -1 in crop rotation A and 550 kg N ha -1 in crop rotation B; N3-510 kg N ha -1 in crop rotation A and 825 kg N ha -1 in crop rotation B per rotation. Phosphorus and potassium fertilisers were applied in the same way over the whole experimental period: phosphorus 60 kg P 2 O 5 ha -1 under potato, spring barley and winter wheat; 80 kg P 2 O 5 ha -1 under corn and the mixture of clover with grasses; potassium 90 kg K 2 Oha -1 under spring barley, 100 kg K 2 Oha -1 under winter wheat, 140 kg K 2 Oha -1 under potato, 159 kg K 2 Oha -1 under corn and the mixture of clover with grasses.

3 SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION 91 The experiment was carried out in four replications for each object. Soil material was sampled after 22 years of the experiment after the winter wheat harvest. The samples (mean for four replications) were analysed for: concentration of carbon of organic compounds (Corg.) by dry combustion in the SKALAR TOC PRIMACS analyser, total nitrogen content (Nt) according to Kjeldahl [12], humus fractions susceptible to oxidation as described by oginow [10], enzymatic activity (48 h after sampling): dehydrogenase activity [2], cellulose activity [4], protease activity [8], total populations of bacteria (B), actinomycetes (A) and fungi (F) as deep inoculation with 10 times diluted soil. These solutions were prepared from 10 g of soil in the Ringer solvent. The microbial populations were evaluated as the number of colonies in specific groups of microorganisms developed under optimum conditions on the relevant media, i.e. total bacteria on the medium as given by Bunt and Rovira [1], actinomycetes as described by Kuster and Williams [8], and fungi according to Martin [11]. The results were used in calculations of the development coefficient (B+A/F) [13]. The results were evaluated with variation analysis with the use of the Tukey test at the significance level of =0.05, for multi-factor experiments without replications, on the relevant system of factors: factor I crop rotation, factor II manure, factor III mineral nitrogen. RESULTS AND DISCUSSION The content of organic compounds in soil prior to the experiment was 7.7 g kg -1. It was found that in the humus-depleting crop rotation after 22 years of the experimental application of only mineral fertilisation and farmyard manure (in s 20 and 40 t ha -1 ) with and without mineral fertilisers caused a decrease in organic carbon (Corg.) in the soil. On the contrary, crop rotation B (enriching the soil with organic carbon) resulted in an increase of the Corg. concentration in soil by about 26% when compared with its content in the same soil prior to the investigations (Table 1). Statistical analysis showed that rotation of crops and fertilisation were factors significantly affecting the content of Corg. in the soil. The effect of plants enriching the soil in humus cultivated under the crop rotation B was observed as an increase of Corg. concentration in soil samples by 29.3%, while in the system A (depletion) the corresponding value was on average 9.7 g kg -1 (Table 1).

4 92 K. KONDRATOWICZ-MACIEJEWSKA TABLE 1. RESULTS OF VARIATION ANALYSIS FOR ORGANIC CARBON (Corg., g kg -1 ) AND TOTAL NITROGEN (Nt, g kg -1 ) CONTENT IN SOIL AND VALUES OF THE RATIO Corg. : Nt Factor C org Nt C org : Nt I Crop rotation II Manure III Mineral nitrogen Depleting A Enriching B N N N2 8.5 n.s N n.s. It was also observed that the influence of the amount of manure on carbon content depended on the choice of plants used during the crop rotation. Cultivation of plants considered as depleting the soil with humus requires the use of higher s of farmyard manure (60 and 80 t ha -1 ) in order to maintain Corg. on a level close to the initial one. In the case of rotation of crops enriching the soil with humus then application of only 20 t ha -1 was enough to achieve a significantly higher Corg. concentration in the soil when compared with the initial value for soil fertilised exclusively with mineral nitrogen. Another interesting fact was that manure s higher than 20 t ha -1 did not cause any further increase of Corg. in soil (Table 1a). Statistical analysis did not show any effect of fertilisation with mineral nitrogen on the content of organic carbon in soil. Average Corg. concentration in soil samples without nitrogen fertilisation and in those fertilised with nitrogen applied TABLE 1a. AVERAGE CONTENT OF ORGANIC CARBON (C org, gkg -1 ) IN SOIL AS DEPENDENT ON CROP ROTATION SYSTEM (FACTOR I) AND MANURE DOSE (FACTOR II) Manure Crop rotaion A B I/II 0.45, II/I 0.66.

5 SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION 93 in the s N1 and N2 was 8.5 g kg -1, while that after the use of N3 was 8.8 g kg -1. The total nitrogen Nt values were determined by all the three experimental factors (Table 1). Average Nt concentration noted in case of crop rotation B (enriching the soil with humus) was 33.3% higher than in soil under crop rotation A. Another factor influencing Nt concentration in the soil was manure. A significant effect was observed for the s 40, 60 and 80 t ha -1, where the average Nt content in soil was higher by 8, 9.3, and 16.0%, respectively in comparison to the variant without organic fertilisation. Nt concentration was also affected by fertilisation with mineral nitrogen. The highest Nt content (0.83 g kg -1 ) was recorded after the use of the highest mineral nitrogen, N3. In general, Nt concentration in the soil samples of that variant was 7.8% higher than in the same without nitrogen fertilisation. Changes in total content of carbon in the soil were not simply quantitative; they were also connected with another susceptibility of organic matter to oxidation, that by potassium manganate (VII) in an acidic solution [10]. The assessment of liability to decomposition can indicate the potential ability of soil organic matter for quick release of nutrients [6, 10]. The percentage content of organic matter fraction susceptible to oxidation (Table 2) was significantly higher (by 7.4%) in soil samples taken from plots under plants depleting the soil with organic matter as compared to those of variant B (crop rotation enriching the soil with humus). A decrease of the share of the fraction of organic matter susceptible to oxidation was observed along with TABLE 2. VARIATION ANALYSIS FOR THE CONTENT AND PERCENTAGE OF ORGANIC MATTER FRACTION SUSCEPTIBLE TO OXIDATION IN SOIL [OXIDABLE CARBON CONTENT (g kg -1 soil) AND PERCENT OF OXIDABLE CARBON (% Corg)] Factor Oxidable carbon content (g kg -1 ) Percent of oxidable carbon (% C org) I Crop rotation II Manure III Mineral nitrogen Depleting A Enriching B n.s N N N n.s N n.s.

6 94 K. KONDRATOWICZ-MACIEJEWSKA increasing manure s. The percentage of that fraction in soil fertilised with the highest of manure was 3.6% lower than in soil samples without manure. Under crop rotation A (depleting the soil with humus), the use of 40 t ha -1 manure caused a significant increase in the share of the fraction of organic matter susceptible to oxidation (Table 2a). TABLE 2a. AVERAGE PERCENT OF ORGANIC MATTER FRACTION SUSCEPTIBLE TO OXIDATION (% C org) AS DEPENDENT ON CROP ROTATION SYSTEM (FACTOR I) AND MANURE DOSE (FACTOR II) Manure Crop rotaion A B I/II 2.41, II/I The results clearly indicated that the choice of plants for rotation of crops is an important factor, having an impact on the percentage of the fraction of organic matter susceptible to oxidation. Various percentages of oxidable carbon to total organic carbon was also confirmed by the changing biological properties of the soil observed as the effect of crop rotation systems and fertilisation used in the experiment (Table 3 and 4). Increasing s of farmyard manure were parallel to increasing the biological activity of soil sampled from the plots under the crop rotation B (enriching). The latter increased the intensity of decomposition of labile carbon forms, and as a consequence decreased the share of organic matter fraction susceptible to oxidation. The results confirmed earlier observation of Gonet and Wegner [5], Janowiak [6] and oginow et al. [9] concerning the relationship between soil biological activity and the percentage variability of the fraction of organic matter susceptible to oxidation. Correct fertilisation adjusts the resources of nutrients, affects its physical and chemical properties as well as it has an impact on the development of microbiological populations taking part in transformations of matter and energy flow in the soil agroecosystems [15]. The intensity of the growth of heterotrophic microorganisms in the soil depends partly on the availability of carbon and nitrogen compounds. For this reason, crop rotation systems and fertilisation change the qualitative and quantitative composition of soil microorganism populations in the most drastic way [14]. Differentiated fertilisation applied under the plants of the crop rotation B (enriching) stimulated the growth of soil microflora (Table 3). The statistical analysis did not show any significant effect of crop rotation on the size of bacteria and actinomycetes in the soil, while fungi formed a microbial group that grew significantly better in the soil under crop rotation A than in the soil under crop rotation B.

7 SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION 95 TABLE 3.VARIATION ANALYSIS OF BACTERIA (B), ACTINOMYCETES (A) AND FUNGI (F) POPULATION SIZE ( 10 5 per 1 g d.m.) AND VALUES OF MICROBIAL DEVELOPMENT INDEX (R) Factor Bacteria (B) Actinomycetes (A) Fungi (F) R (B+P/G) I Crop rotation II Manure III Mineral nitrogen Depleting A 56.5 n.s Enriching B N N N N

8 96 K. KONDRATOWICZ-MACIEJEWSKA A significant effect of fertilisation with farmyard manure was that observed on the microbiological populations in the soil as well as the index of their development in both crop rotation systems (Table 3). Increasing s of manure caused an increase in the size of the populations of bacteria, actinomycetes and fungi in the soil under study. The of 80 t ha -1 manure increased the size of bacteria population four times, while that of actinomycetes and fungi populations five times when compared with the soil without manure. The highest values of the soil microflora development were calculated for the s of 20 and 40 t ha -1 manure (11.7 and 10.8, respectively). Statistical analysis revealed the biggest difference in the actinomycetes populations in soil samples under the two crop rotation systems at the of 60 t ha -1 manure (Table 3a). The average size of those microorganism populations in the soil for that manure for crop rotation B was 19.7% lower than under crop rotation A. It was also found that even at a of 40 t ha -1 manure the size of those microbial population significantly increased for both crop rotation systems under study. For both crop systems A and B, the highest of manure (80 t ha -1 ) caused a change in the populations of actinomycetes some five-fold higher than in the variant without the use of manure. TABLE 3a. AVERAGE SIZE OF ACTINOMYCETES POPULATION (A) ( 10 5 per 1 g d.m.) IN SOIL AS DEPENDENT ON CROP (FACTOR I) AND MANURE DOSE (FACTOR II) Manure Crop rotaion A B I/II 0.444, II/I An intense development of soil microflora was also confirmed by the index of development (B+A/F). The increase of fungal population in soil at high s of farmyard manure and mineral nitrogen caused a drop of the development index value [13]. These values suggest that the stimulating effect of fertilisation had a negative influence on the growth of microbial populations in the soil. Crop rotation systems and differentiated fertilisation can affect not only the qualitative and quantitative composition of soil microorganisms but also their metabolism. This was confirmed as changes in the investigated enzymatic activities (Table 4). A stimulatory effect of fertilisation with farmyard manure and mineral nitrogen observed for both crop rotation systems was confirmed in an increase of dehydrogenase activity. These enzymes are a measure of the respiratory (metabolic) activity of microorganisms, thus indirectly also their

9 SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION 97 biomass. The trophic effect performed on differentiated fertilisation both in the depleting and enriching crop rotation systems caused a promotion of the development of microorganisms, in consequence also higher enzymatic activities. Statistical analysis disclosed interactions between factor I and II for cellulose activity as well as factor I and II for protease activity. It was found that the crop rotation A at the nitrogen N3 caused the highest activity of celluloses (Table 4a); however, the crop rotation B was better for this type of activity because the N1 was beneficial for the activity of those enzymes. For the proteases, a statistically significant difference between crop rotations A and B was noted for farmyard manure s of 40 and 60 t ha -1 (Table 4b). After the use of the same s of manure the enzymatic activity was by 14.4 and 21.8%, respectively, in Factor Cellulose activity Dehydrogenase activity I Depleting A Crop rotation Enriching B II Manure III Mineral nitrogen TABLE 4. VARIATION ANALYSIS OF CELLULOSE (nm glucose/1 h/1 g d.m.), DEHYDROGENASE (mg triphenyloformazan/1 g d.m./24 h), AND PROTEASE (mg glycin/1 g d.m./24 h) ACTIVITIES IN SOIL N N N N Protease activity TABLE 4a. AVERAGE CELLULOSE ACTIVITY AS DEPENDENT ON FERTILISATION (FACTOR I) AND MINERAL NITROGEN DOSE (FACTOR II) Nitrogen Crop rotaion N0 N1 N2 N3 A B I/III 0.744, III/I 1.014

10 98 K. KONDRATOWICZ-MACIEJEWSKA TABLE 4b. AVERAGE PROTEASE ACTIVITY AS DEPENDENT ON FERTILISATION (FACTOR I) AND MANURE DOSE (FACTOR II) Manure Crop rotaion A B I/II 0.041, II/I soil samples under the crop rotation B than under crop rotation A. However, the use of this fertiliser under crop rotation B in the highest of 80 t ha -1 resulted in a relatively lower increase of protease activity (an average of 13.9%) than in case of the crop rotation A system. CONCLUSIONS 1. Fertilisation with farmyard manure in the crop rotation enriching the soil with organic matter (B) resulted in humus with a lower percentage of the fraction susceptible to oxidation, which is a consequence of increased soil biological activity. 2. Fertilisation with mineral nitrogen with manure caused a more intense development of microorganisms (bacteria, actinomycetes and fungi), in consequence a higher activity of soil enzymes. REFERENCES [1] Bunt J.S., Rowira A.D.:J.Soil Sci., 56, 119, [2] Casifa L.E.Jr., Klein D.A., Santoro T.:Soil Sci, 98, 371, [3] Cieœla W., Pech K., Pawluczuk Z., Rzeœniowiecka-Sulimierska G.:Zesz. Nauk. ATR, 44, 23, [4] Deng S.P., Tabatabai M.A.:Soil Biol. Biochem., 26, 10, 1347, [5] Gonet S.S., Wegner K.:Zesz. Nauk. AR, Wroc³aw, Rolnictwo, 53, 196, 127, [6] Janowiak J.:Zesz. Probl. Post. Nauk Roln., 421a, 145, [7] Kuster E., Williams S.T.:Nature, 202(4935), 928, [8] Ladd J.N., Butler J.H.A.:Soil Biol. Biochem., 4, 19, [9] oginow W., Andrzejewski J., Janowiak J.:Rocz. Glebozn., 42, 3/4, 19, [10] oginow W., Wiœniewski W., Gonet S.S., Cieœciñska B.: Zesz. Probl. Post. Nauk Roln., 411, 207, [11] Martin J.P.:Soil Sci., 69, 215, [12] Mocek A., Drzyma³a S., Maszner P.: Geneza, Analiza i Klasyfikacja Gleb. Wyd. AR Poznañ, [13] Myœków W.:Postêpy Mikrobiologii, 3/4, 173, [14] Runowska-Hryñczuk B.:Pam. Pu³., 100, 187, [15] Spychaj-Fabisiak E., Smoliñski S., Murawska B., Janowiak J.:Humic Subst. Ecosyst., 5, 109, 2003.

11 SUSCEPTIBILITY OF ORGANIC MATTER TO OXIDATION 99 PODATNOŒÆ MATERII ORGANICZNEJ NA UTLENIANIE I AKTYWNOŒÆ MIKROBIOLOGICZNA GLEBY W WARUNKACH ZRÓ NICOWANEGO ZMIANOWANIA I NAWO ENIA W wieloletnim doœwiadczeniu polowym badano wp³yw zmianowañ (wzbogacaj¹cego i zubo aj¹cego glebê w próchnicê), nawo enia obornikiem i azotem mineralnym na podatnoœæ materii organicznej gleby na utlenianie oraz aktywnoœæ biologiczn¹ gleby. Stwierdzono, e niezale nie od dawki stosowanego obornika, w warunkach zmianowania wzbogacaj¹cego glebê w próchnicê materia organiczna posiada ni sz¹ podatnoœæ na utlenianie ni w warunkach zmianowania zuba aj¹cego. Nawo enie azotem mineralnym oraz obornikiem skutkuj¹ wzrostem liczebnoœci mikroorganizmów w glebie oraz wzrostem aktywnoœci enzymatycznej gleby.