ENZYMATIC ACTIVITIES INVOLVED IN S- TRANSFORMATIONS AND THEIR MUTUALISTIC RELATIONSHIPS WITH INORGANIC-S COMPONENTS AND DISTRIBUTIONS IN SALT AFFECTED SOILS | ||||
| Journal of Soil Sciences and Agricultural Engineering | ||||
| Article 5, Volume 33, Issue 8, August 2008, Page 6217-6240 PDF (788.06 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jssae.2008.200220 | ||||
 View on SCiNiTO | ||||
| Author | ||||
| M.A.M. El-Kammah | ||||
| Soil Science Dept., Fac. of Agric., Kafrelsheikh Univ., Kafr El-Sheikh, Egypt. | ||||
| Abstract | ||||
| A comprehensive experimental study was conducted at three locations reflecting the semi-arid conditions of Kafr El-Sheikh governorate. The selected soils are slightly salt-affected and irrigated in non-rational rates for a long-time with different sources of wastewaters, under different drainage conditions. A novel conceptual diagram was constructed to integrate the main labile and stable inorganic-S fractions and the ways by which their amounts are determined and calculated. The aim of this study was to assess the biochemical activity of some soil enzymes involved in S-transformations and gain informations about the standing stocks and distributions of all inorganic-S fractions in studied soils under different drainage conditions. Statistical of treatment of the obtained data, could be summarized as follows: Grand mean value of biological enzymes activity was 328.4 nanomoles SCN- released.g-1 soil.hour-1 for rhodanese, meanwhile, dehydrogenases activity was 9.41 µg TPF produced. g-1 soil. hour-1. Total-S pool recorded 300 mg S. kg-1 soil, its standing stock 257.48 kg S. fed-1, which was within the normal range reported in other regions. Inorganic-S value was 111.3 mg S. kg-1 soil, its standing stock 96.6 kg S. fed-1. Percentage total-S in inorganic-S accounted for 37.7%, which was only a minor fraction compared to the major fraction of organic-S. However, the content of this fraction was higher than reported from temperate and subtropical regions. Inorganic sulfate-S content was 106.2 mg S. kg-1, its percentage distribution expressed as % of total-S and of inorganic-S accounted for 36.3% and 95.6, which was the dominate fraction of inorganic-S fraction. This fraction was more pronounced in studied semi-arid soils in comparison with those reported in other regions. Its value had a positive correlation with soil clay content. Easily soluble and adsorbed sulfate-S contents were 82.1 and 1.8 mg S. kg soil, their percentage distributions accounted for 77.6% and 1.3% of inorganic sulfate-S. Soluble sulfate-S was the major S form of inorganic sulfate-S and at the same time was greater in comparison with reported in literature. Adsorbed sulfate-S had the opposite trend and negative correlation with soil pH as well as positive with clay content. Dissolved sulfate-S fraction contains insoluble sulfate-S plus Co-precipitated/Co-crystallized with CaCO3. Its value was 22.3 mg S-kg-1 soil accounted for 21.1% of inorganic sulfate-S, which was positive correlated with CaCO3 content. Inorganic non-sulfate-S value was 5.2 mg S. kg-1, accounted for 4.4% of inorganic-S, which was greater than reported in other regions and had a positive correlation with CaCO2 content. Oxygenic highly oxidized-S form and lowly oxidized-S plus reduced-S forms were 4.2 and 0.99 mg S. kg-1 soil, accounted for 84.2% and 15.8% of inorganic non-sulfate-S. Contents total-S pool and all fractions of inorganic-S as well as their percentage distributions had their maximum values in traditional drained soils in winter seasons. Whereas it reached their minimum values in badly drained soils in summer seasons. These findings in year 1999/2000 were more pronounced than those obtained in year 2000/2001. Total-S and inorganic-S, as well as their compounds in salt-affected soils had a positive correlations with: water table depth; CaCO3; clay content; organic-S and total-N. However, their values were negative correlated with ionic strength; bulk density; max. air temp.; soil temp., pH, C/S ratio. Values of biochemical enzymes activities of rhodanese and dehydrogenase had positive correlations mainly with water table depth, pH, organic-C and total-N. Enzymes activities had also positive correlation with inorganic non sulfate-S content and its forms. Whereas, their values were negatively correlated with ionic strength, C/S ratio total sulfate-S and soluble sulfate-S. Maximum biological activity was happened in winter month Feb., whereas its minimum value was in summer month July. These activities had negative correlations with max. air temp. and soil temp. which prevailing in studied area over the experimental period. | ||||
| Keywords | ||||
| Rhodanese; dehydrogenase; total-S; inorganic-S; inorganic sulfate-S; inorganic non-sulfate-S; modified Johnson-Nishita apparatus | ||||
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