Field investigations into the manurial value of liquid undigested sewage sludge when applied to grassland

• Published in: The Journal of agricultural science 1987-12, Vol.109 (3), p.479-494
• Main Authors: Coker, E. G., Hall, J. E., Carlton-Smith, C. H., Davis, R. D.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Other nutrients. Amendments. Solid and liquid wastes. Sludges and slurries; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 0021-8596; 1469-5146
• DOI: 10.1017/S0021859600081697

Two sets of experiments were carried out during 1978–82 in order to compare the value of nitrogen in liquid undigested sludge (LUDS) with that in ‘Nitro-Chalk’. One set took place in the area of north Hertfordshire-south Bedfordshire, and the other at the University of Leeds. In the first growing season after application the relative effectiveness of LUDS-N was about 20%. In subsequent years it was about 40% though it was less on a soil initially very deficient in soil-N. At Leeds the 2nd-year value was 60–75%. In the growing season immediately following treatment, N mineralized from LUDS became available too late to increase D.M. yields greatly; much of this appeared to be retained in the turf mat and increased the yield of D.M. the following year. When the lower 1st-year responses were taken into account there did not appear to be any yield penalty in making autumn (November) applications, compared with spring (February). This overall result concealed differences between soils. In a year when it was dry during the main growing period yields were reduced by about 25%. It seems that LUDS-N is most valuable when it is applied regularly to the same area, and in the wetter parts of the country. Much LUDS comes from smaller rural sewage treatment works which are much less likely to carry contamination from potentially toxic elements.