An evaluation of selected soil properties and their effect on the biological activity of soils in organic farming in the Czech Republic

Sarapatka, B.A, Pokorny, E.B, Hejatkova, K.C, Matlova, V. D, Krskova, M.E

Abstract - In our research we have evaluated a series of soil indicators to determine the correlation between individual soil properties in organic farming. Regression analysis has proven that the biological activity of the soil on organically farmed areas (grasslands) as expressed by respiration is mainly influenced by the bulk density, moisture, porosity, humus content, the proportion of cation exchange capacity and total nitrogen content. The multiple regressions have proven the important dependency of basal respiration to the moisture, bulk density and total nitrogen. The supply of organic matter to the soil environment, thus greatly influences the studied soil biological activity. Similar dependences were visible in the results of both conventional and organic farming on arable land.

Introduction
Soil quality belongs among the topical environmental issues in the Czech Republic. According to Sarapatka, Novak and Bednar (2006) the most serious degradation of soils in the Czech Republic is caused by water erosion, but other types of degradation, e.g. loss of organic matter, are also significant. One of the approaches attempting to deal with soil degradation is organic farming, currently practised on 263,299 ha of farmland in the Czech Republic (6.16% of agricultural soil in the country). The majority of this area (89.4%) is covered by grass stands (Collective, 2005). An appropriate evaluation of soil quality requires the selection of relevant indicators. According to Doran and Parkin (1966) health indicators should correlate well with ecosystem processes; integrate physical, chemical and biological soil properties and processes; be sensitive to management practices; be relatively simple to use under field conditions and easy to assess by both specialists and producers. Therefore, we have also focused on the operatational practicability of the indicators. We have evaluated a series of soil indicators to determine the correlation between individual soil properties in organic farming. In further research we plan to investigate other correlations with quantitative questions on the subject of grass associations.

Materials and methods
The soil samples were collected from 18 farms (54 areas) during 2001-2004. The prevailing soil type was cambisol. Landscape use reflected the land cover which was permanent grass stand, the quality of the association was also followed. The basic physical (bulk density, porosity, water and air regime, texture) and chemical (humus content and quality, Ntot, pH, CEC, basic elements, conductivity) features were studied according to common pedological laboratory methods (Zbíral et al., 1995-1997). The results of basal respiration were correlated with the results of physical and chemical analysis and probatory dependences were expressed by approximate regress polynoms of bot the first and second degree of compatibility. 

Results
We considered the biological activity of soil as measured by respiration, one of the basic features which is easily measured and used as an indicator of soil quality (Harris et al. 1966). The use of microbiological and enzymological methods for investigating soil quality is well known (e.g. Nannipieri et al. 1990, Dick, Breakwell and Turco 1996, Sikora et al. 1995). The methods are in close relation to other soil features, but in contrast to subsequent methods they could show changes sooner and, in keeping with subsequent bio-indicators, they integrate the pedological, chemical and biological states of the soil.
	The respiration test yielded important results in all variants. It has correlated well (5% significance level) with several physical and chemical soil features. The effect of the bulk density was conclusively proved. Optimal bulk density values for basal respiration power are mass volumes around 1g.cm-3. Further increasing the values leads to a decrease in respiration. It ceases at 1.8 cm-3 according to a regression curve. The relationship between respiration power and bulk density has been published in more articles but its quantification on a large scale of mass volumes has not been previously carried out until now. Basal respiration is greatly influenced by soil porosity and pore distribution. With increasing porosity basal respiration increases. The increase in basal respiration with growing at 30 min. moisture reflects the preparation of the sample in the lab before analysis. In samples with prevailing capillary pores the preparation of the sample (loosening) causes a substantial improvement in the respiratory conditions. The humus content, as an energy source for respiration, markedly influences physical conditions (structure, bulk density). Within the permanent grass stand studied we marked as 8% as optimal. The dependence is linear; positive where an increasing value of humus content causes an increase in basal respiration, 90% of the values are lower than 8.15%. This demonstrativeness was found between the values of cation exchange capacity and basal respiration. This dependency is positive with maximum basal respiration values achieved at CEC 350 mmol.kg-1. A similar positive dependency exists between the total nitrogen content of soil and basal respiration. Maximum basal respiration values are achieved at a nitrogen content of 0.5%. So, high values are possible on grass stand whereas on arable land they could only be sporadically achieved. In effect: the bigger Ntot content the higher the basal respiration.

Conclusions
Regression analysis has proven that the biological activity of the soil on organically farmed areas as expressed by respiration is mainly influenced by the bulk density, moisture, porosity, humus content, the proportion of cation exchange capacity and total nitrogen content. The multiple regressions have proven the important dependency of basal respiration to the moisture, bulk density and total nitrogen. The supply of organic matter to the soil environment, thus greatly influences the studied soil biological activity. Similar dependences were visible in the results of both conventional and organic farming on arable land. The next investigative step, phytocenological recordings, will be acquired and then the received dependences will be examined in relation to the quality of the association of grass stand using multivariate analysis. These results will be reviewed with data received from other projects of the grass stands ecosystems study.

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First A. Author is from the Palacký University, Olomouc and Bioinstitut, tr. Svobody 26, 771 46 Olomouc, Czech Republic (borivoj.sarapatka@upol.cz)
Second B. Author is from the Mendel University of Agriculture and Forestry, Zemedelska 1, 613 00 Brno (pokorny@mendelu.cz)	
Third C. Author is from the ZERA, Namest nad Oslavou, Czech Republic  (hejatkova@cmcnamest.cz)
Fourth D. Author is from Research Institute of Animal Production, 104 01 Prague – Uhrineves, Czech Republic (matlova.vera@vuzv.cz)
Fifth E. Author is from the Palacky University, tr. Svobody 26, 771 46 Olomouc, Czech Republic (krskova@cvt.upol.cz)