INFLUENCE OF IRRIGATION ON THE SULPHUR CONTENT AND SOIL ENZYMES ACTIVITY UNDER SILPHIUM PERFOLIATUM L.

Anetta Siwik-Ziomek¹, Anna Figas², Roman Rolbiecki^3
1 Department of Biogeochemistry and Soil Science, University of Science and Technology, Bydgoszcz, Poland
² Department of Agricultural Biotechnology, University of Science and Technology, Bydgoszcz, Poland
³ Department of Land Reclamation and Agrometeorology, Faculty of Agriculture and Biotechnology, University of Technology and Life Sciences in Bydgoszcz, Poland

ABSTRACT

The aim of the present research was to determine the effect of drip irrigation on the activity of enzymes (rhodanese and arylsulphatase) participating at cycling sulphur in soil and content of total sulphur and sulphate (VI) in soil under crops cup plant. The research material was derived from an experiment located at Kruszyn Krajeński in the vicinity of Bydgoszcz. The main factor of the experiment was irrigation at following variants: O – without irrigation (control plots), D – with drip irrigation. The plant material was made up by plants seedlings from micropropagation. The amount of sulphur available for plants, in the soil investigated for control plots was, on average, 7.62 mg·kg^-1 and for the irrigation plots it was similar 5.88 mg·kg^-1, which, according to the soil richness with sulphur S-SO₄^2- classifies it as the soil of its average content and growing cereals requires supplementary fertilisation with sulphur. There was shown a high sensitivity of arylsulphatase on the changes in soil moisture and a greater stability in the activity of rhodanese on that factor.

Key words: arylsulphatase, cup plant, micropropagation, rhodanese, drip irrigation.

INTRODUCTION

Soil enzymes are derived primarily from soil fungi, bacteria, plant roots, micreobial cells, plant and animal residues [8] and play an important role in the decomposition of carbon (C), nitrogen (N), sulphur (S) and phosphorus (P), therefore there are to be the rate-limiting step in microbially mediated distribution [12, 17, 22]. Sulphur transformation in soil is managed by mineralization of organic compounds containing sulphur and inorganic compounds oxidation processes. Arylsulphatases hydrolysis of aromatic sulphate esters (R-O-SO^3-) to phenols (R-OH) and sulphate (SO₄^2-) [20]. Rhodanese converts S2O^3- to SO₃^2- which are intermediates during the oxidation of elemental sulphur (S°) [21]. Soil moisture has a strong effect on plant growth, animal and microbial activity. In general, studies found decreased respiration rates in dry soils [13]. Microorganisms are not affected equally by low soil moisture potential [4]. Sardans and Peñuelas [16] found that the reduction of soil moisture considerably decreased urease, protease and ß-glucosidase activity in soil. McDaniel et al. [10] reported that increased temperature and precipitation had limited effects on soil extracellular enzyme activities in soils of a post-harvest forest. Increased precipitation can enhance soil extracellular enzyme activities via increasing enzyme and substrate diffusion [1]. However, there are no studies that examined the responses of enzymes involve in transformation of sulphur in irrigation soil under crops cup plant. Cup plant (Silphium perfoliatum L) offers a potentially valuable material for pharmaceutical and foodstuffs industries since the roots and rhizomes contain inulins and its leaves, flowers and rhizomes – biologically active substances of isoprenoids group, phenol and polyphenol compounds. The species is a perennial growing on poor soils and since it can adapt to different environments it can also be used as a pioneer plant for land rehabilitation in the areas destroyed by industry and municipal services management [6]. The Silphium perfoliatum plantations produce large quantities of biomass used as energy-producing material [18].

The aim of the present research was to determine the effect of drip irrigation on the activity of enzymes (rhodanese and arylsulphatase) participating in cycling sulphur in soil and the content of total sulphur and sulphate (VI) in soil under crops cup plant.

MATERIALS AND METHODS

The research material was derived from an experiment located at Kruszyn Krajeński in the vicinity of Bydgoszcz. The soil from the experimental plot represented Phaeozems produced from alluvial sand. The soil demonstrated a very low water retention capacity. The experiment was performed as one factorial in 4 replications. The main factor of the experiment was irrigation at the following variants: O-without irrigation (control plots), D-with drip irrigation. The experimental soil was characterized by a low capacity for water retention. The water reserve to 1 m depth of soil at field capacity was 87 mm and the available water 68 mm. Irrigation was done with drip line ‘T-Tape’. Terms of irrigation and water rates were established according to tensiometers indications. The irrigation was started at -50 kPa of soil water potential. The irrigation seasonal water doses were connected with termal and rainfall conditions during the experimental periods (Tab. 1) and amounted 116 and 131 mm in 2012 and 2013, respectively. The temperature data were taken from automatic weather station located at Mochełek. The rainfalls were measured manually, directly at the field by Hellmann’s rain gauge. The agrotechnical practices and fertilization were applied at the rate of 500 kg·ha^-1 N:P:K at the ratio of 2:2:3. The nitrogen fertilization was supplied in three single rates. The single experimental plot was 11 m². During the vegetation seasons the plants were in good health condition. The occurrence of diseases and pests weren’t seen. The plant material was made up by plants seedlings from micropropagation.

In the adequately prepared material there were determined: total organic carbon (C_org) and total nitrogen (N_tot) with the Primacs analyser provided by Scalar. The soil arylsulphatase activity (ARS) was assayed according to Tabatabai and Bremner [20], rhodanese activity (ROD) – according to Tabatabai and Singh [21], the content of total (S_tot) and sulphate sulphur (VI) (SO₄^2-) – as described by Bardsley and Lancaster [2].

The results were exposed to the analysis of variance and the significance of differences between means was verified with the Tukey test at the significance of p=0.05. The calculations involved the use of FR-ANALWAR software based on Microsoft Excel. Besides the results of the analyses of the features investigated were exposed to the analysis of simple correlation (p<0.05) which determined the degree of the dependence between respective features. The analysis of correlation was made using ‘Statistica for Windows Pl’ software.

RESULTS AND DISCUSSION

The content of basic soil nutrients; total organic carbon (C_org) and total nitrogen (N_tot) differed in the content across the years, however, the differences were non-significant. Neither was there found the effect of the application of drip irrigation on the content of those soil components. The total organic carbon in the soil analysed ranged from 10.7 g·kg^-1 to 13.4 g·kg^-1 for control plots and 8.47 g·kg^-1 do 9.30 g·kg^-1 for plots with drip irrigation in the first year of investigation. In the following research year the mean C_org was lower; it was 7.82 g·kg^-1 (Tab. 2). The total nitrogen content in the soil was, on average, 1.10 g·kg^-1 for plots without irrigation and on average 0.853 g·kg^-1 for irrigation plots in the first year of investigation and, respectively, 0.78 g·kg^-1 and 0.99 g·kg^-1 in the second year.

The irrigation applied in the experimental field at Kruszyn did not have a significant effect on the content of the nutrients of organic matter and its mineralization, which is expressed by the ratio of C:N. Koszański et al. [7], after seven-year irrigation, found a significant increase in the content of carbon and nitrogen in the arable layer of soil without changes in the ratio of C:N.

The total sulphur (S_tot) content in the very light soil was, on average, 0.0341 g·kg^-1 for control plots, on average 0.0367 g·kg^-1 for irrigation plots in the first year of investigation and 0.035 g·kg^-1 and 0.038 g·kg^-1 at the second year, respectively (Tab. 3). The contents of sulphur recorded in the present research classified the soil, applying the grading scale developed by IUNG, as showing a natural (≤ 0.150 g·kg^-1) sulphur content [11].

There was demonstrated no significant effect of irrigation on the content of total sulphur in the soil (Tab. 3), which must be due to the heterogeneous composition of compounds containing sulphur and the complexity of the process of its transformations. Total sulphur in soil is bound to organic moleculeles (>95%) and inorganic sulphate. This organic sulphur is present as a heterogeneous mixture of forms, partly included in microbial biomass and partly in the soil organic matter, and very little is known about the chemical identity of the specific sulphur-containing molecules [5]. The sulphur pools in soil are not static, but extremely dynamic. Inorganic sulphur forms are immobilized to organic sulphur, different organosulphur forms are interconverted, and immobilized sulphur is simultaneously mineralized to yield plant available inorganic sulphur. These processes occur concurrently, and many of them are linked to the microbial biomass present in the soils [5].

The content of sulphate sulphur (SO₄^2-) for the control soil was, on average, 7.13 mg·kg^-1 at the first year of investigation. In the second year sulphate sulphur was lower 6.34 mg·kg^-1. There was found no significant effect of irrigation on the content of that element in the soil (Tab. 3). In most of the soils under agricultural use the content of sulphate sulphur in Poland does not exceed 25 mg·kg^-1 of soil. Most soils, namely 70% of the agricultural acreage, show the content of that sulphur fraction from 5.0 to 20.0 mg·kg^-1 [9]. The amount of that sulphur fraction in the soil investigated for control plots was, on average, 7.62 mg·kg^-1 and for the irrigation plots it was similar 5.88 mg·kg^-1, which, according to the soil richness with sulphur S-SO₄^2- classifies it as the soil of its average content and growing cereals requires supplementary fertilisation with sulphur [9].

Zhang and Wang [23] investigated the impact of irrigation on phosphatase, urease, and catalase activities under tomato cultivation in a greenhouse experiment. Phosphatase and catalase activities increased when exposed to more frequent irrigation and urease activities decreased under irrigation. Arylsulphatase activity in the soil was, on average, 0.124 µM pNP·g^-1·h^-1 for the control soil and, on average 0.054 µM pNP·g^-1·h^-1 for the irrigation plots. In the second research year the activity of that hydrolase was, on average, 80% higher and it was, on average for the control plots 0.544 µM pNP·g^-1·h^-1 and for the irrigated ones 0.406 µM pNP·g^-1·h^-1. The activity of rhodanese, on the other hand, was, on average, 154 nM SCN·g^-1·h^-1 in the control soil and, on average, 372 nM SCN·g^-1·h^-1 for the irrigation plots in 2012. In the second research year the activity of that transferase was levelled and it did not depend on the irrigation applied and it was, on average, for the control plots 254.0 nM SCN·g^-1·h^-1and for the irrigated ones 219.3 nM SCN·g^-1·h^-1. In the first research year the activity of arylsulphatase and rhodanese depends on drip irrigation. A higher activity of arylsulphatese was observed in the plots without irrigation. However the activity of rhodanese was 59% higher in the irrigated soil. Deng and Dick [3] reported that the response of rhodanese activity to change in water potential depended on soil. Similarly, Ray et al. [15] showed a 2.5-6-fold increase in rhodanese activity in a pokkali (acid sulphate) soil after flooding but no changes in a flooded alluvial soil. The activity of arylsulphatase diminished and the change in the activity of β-glucosidase depended on the soil [14].

The physicochemical and edaphic properties of soil (moisture, fertility) define the soil and determine the development of living organisms in ecosystems. In 2012 the highest rainfall was reported in June and it was 133 mm, which was after May which recorded the amount of rainfall lower than the many-year period (Tab. 1). Intensive rainfall at the soil sampling time in June must have resulted in essential changes in the population of microorganisms. However, in the following year in May there was recorded an increased amount of rainfall and in June – slightly lower, as compared with the many-year period. In the soil there must have occurred such changes in the conditions which enhanced the growth and development of fungi. The activity of rhodanese in soil could be taken as a measure of the abundance of fungi [19]. However, the activity of arylsulphatase decrease significantly as a result of drip irrigation. The effect of water in soil on the activity of arylsulphatase was confirmed with a negative correlation between its activity and rainfall (r=-0.962. p=0.05).

SUMMARY

There was found no significant effect of drip irrigation on the contents of C_org, N_tot, S_tot and SO₄^2- in the light soil under study. The distribution of organic matter in soil is a complex many-staged process, which involves many physicochemical and biological factors. The rate of sulphur cycling depends on the enzymes present and on its activity. The amount of sulphur available for plants, in the soil investigated for control plots was, on average, 7.62 mg·kg^-1 and for the irrigation plots it was similar 5.88 mg·kg^-1, which, according to the soil richness with sulphur S-SO₄^2- classifies it as the soil of its average content and growing cereals requires supplementary fertilisation with sulphur. There was shown, however, the effect of drip irrigation on the activity of arylsulphatase and rhodanese in the first year of research in which May showed low rainfall and June demonstrated 60% more than the many-year period. There was shown a high sensitivity of arylsulphatase on the changes in soil moisture and a greater stability in the activity of rhodanese on that factor. Water in soil facilitates the diffusion of substrates and nutritive compounds inside the cell, enhancing the growth and development of plant, microorganisms and so it is justifiable to investigate the effect of irrigation on the content of elements and the activity of enzymes participating in their transformations to get to know the state of soil fertility better.

Accepted for print: 29.09.2015

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