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Title: Agronomic consequences of paper mill waste incorporation into soil
Author: Owen, Icarus Jason
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1995
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The aims of this thesis were to study the agronomic impact of paper sludge incorporation on agricultural soil. through investigation of crop physiological response to paper sludge incorporation, nutrient cycling, soil parameters, soil moisture retention and then attempting to combine this multidisciplinary approach to the study of paper sludge into one empirical model, or management tool. Paper sludge (from Federal Tait Paper, Inverurie) was characterised to determine its composition and variability. In particular, the concentrations of nitrogen, cellulose and calcite were found to vary greatly. Prior to large scale field scale application and biomass-N studies a preliminary germination trial and biomass-N feasibility study were undertaken. The germination trial assessed the potential for paper sludge incorporation into soil to cause germination failure, due to the production of phytotoxic compounds, (e.g. acetic acid). It concluded that there was no risk of germination failure. However, it also indicated possible crop chlorosis associated with those seedlings grown on soil with paper sludge additions, suggesting N immobilisation. A preliminary biomass-N experiment concluded that large cores were unsuitable for biomass-N determinations and concluded that small sealed flasks with a well homogenised soil and paper sludge matrix would be more suitable for biomass-N determinations. To assess the agronomic effects of paper sludge incorporation into agricultural soil, a series of field experiments were carried out. Soil samples were regularly removed to assess soil parameters (e.g. soil pH). The incorporation of high N-concentrations of paper sludge was associated with no reduction in crop growth, harvest index, grain weight or grain numbers per ear. However, grain N-concentration and straw N-concentration were significantly increased as compared to those plots receiving no paper sludge additions. The increase in grain N-concentration approached that permissible by the malting industry of Scotland. The incorporation of low N-concentration paper sludge into soil was associated with significant decreases in crop growth, harvest index, grain numbers per ear and grain and straw N-concentrations, as compared to grain from those plots receiving no paper sludge additions. The decrease in crop growth and grain and straw N-concentrations suggest that N was limiting crop growth. Supplementary inorganic-N additions reinforced this hypothesise that N was limiting, as inorganic-N additions partly negated the reduction in crop growth associated with those plots receiving low N-concentration paper sludge additions. However, significant crop growth reductions were also associated with those plots receiving lime additions ( 8 t ha-1), suggesting that over liming of the soil could also cause crop growth reductions. As the paper sludge has a calcite component it was not possible to distinguish between the influence of the paper sludge affecting soil-N cycling and soil pH alterations in reducing crop growth. Paper sludge significantly increased soil pH. The moisture release characteristics of soil on plots receiving paper sludge applications were also significantly affected so that soil in plots receiving paper sludge additions held more moisture (at particular moisture tensions) than control soils. The biomass-N / N-immobilisation study demonstrated the rapid rise in biomass-N associated with paper sludge incorporation. Significant increases in biomass-N after 3 days of incubation, were associated with the soil receiving paper sludge. The potential for paper sludge to increase soil biomass-N was clearly demonstrated. To analyse the effect of individual paper sludge components on crop growth, a core experiment investigated the relationship between total biological yield (TBY) and those properties of the paper sludge considered to affect the crop growth (i.e. N-concentration, calcite concentration and cellulose concentration) using multiple linear regression techniques. Statistical modelling of the effect paper sludge incorporation into soil had upon crop TBY, explained 74.3% of the observed variation. The NCON (N-concentration of the paper sludge) variable was the largest influencing factor in determining the TBY (r=0.803).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available