Soil indicators of C and N transformations under pure and mixed grass–clover swards

• Published in: European journal of agronomy 1998-11, Vol.9 (2), p.157-172
• Main Authors: Alvarez, G., Chaussod, R., Loiseau, P., Delpy, R.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; biological activity in soil; Biological and medical sciences; biomass; C:N ratio; carbon; carbon nitrogen ratio; Chemical, physicochemical, biochemical and biological properties; crop residues; Diagnosis; dry matter accumulation; Fundamental and applied biological sciences. Psychology; genotype mixtures; Grassland; grassland soils; grasslands; ground cover; leaching; Lolium perenne; Microbial biomass; Mineralization; N leaching; nitrates; nitrogen; Organic matter; Particle-size fraction; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant residues; Respiration; Rye-grass; soil fertility; soil microorganisms; soil organic matter; Soil science; Soil water-extracts; sward; Trifolium repens; White clover
• ISSN: 1161-0301; 1873-7331
• DOI: 10.1016/S1161-0301(98)00034-3

The changes occurring in the soil organic status under grassland swards after 3 years were examined as a function of the initial soil nitrogen supplying capacity (SNSC: 135 or 225 kg N ha −1 year −1) and of the soil cover: bare soil, pure white clover, pure rye-grass or a mixture of both species. The amounts of C and N of the coarse particle size OM, the microbial biomass-C, the C and N in water extracts (microbial metabolites) and the C and N mineralization in 28-day incubation tests were used as indicators of the transformation of the organic C and N inputs to the soil under these contrasting managements. The part of the variation of these indicators explained by the initial soil N supplying capacity decreased from the metabolite-C to the coarse plant residues-C to the microbial biomass-C (MB-C) soil compartments. The part of the variation explained by plant cover increased in the same order. For each variable, the effect of soil fertility was maintained under pure grass and was reduced or suppressed under pure legume. The soil organic status under the mixed stand was similar to that of the pure clover and intermediate between that of the pure clover and the pure grass stands. The amount of N mineralization was similar with similar N amounts in the plant residues, whereas amounts of C in the plant residues and MB-C were in the order: pure clover