Temporal and spatial dynamics of soil solution C and N concentrations during Lolium perenne L. sward establishment and the effects of elevated CO2 and N additions

• Published in: Soil biology & biochemistry 2006-06, Vol.38 (6), p.1290-1297
• Main Authors: Hill, P.W, Jones, D.L, Marshall, C, Farrar, J.F
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; carbon; carbon dioxide; Chemical, physicochemical, biochemical and biological properties; dissolved organic carbon; elevated atmospheric gases; fertilizer application; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Lolium perenne; nitrogen; nitrogen content; Nitrogen, phosphorus, potassium fertilizations; phenols; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant establishment; plant growth; Soil science; soil solution; Soil-plant relationships. Soil fertility. Fertilization. Amendments; spatial variation; sward; temporal variation; Water and solute dynamics
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2005.09.024

There is now clear evidence for a prolonged increase in atmospheric CO2 concentrations and enrichment of the biosphere with N. Understanding the fate of C in the plant-soil system under different CO2 and N regimes is therefore of considerable importance in predicting the environmental effects of climate change and in predicting the sustainability of ecosystems. Swards of Lolium perenne were grown from seed in a Eutric Cambisol at either ambient (ca. 350 micromole mol-1) or elevated (700 micromole mol-1) atmospheric pCO2 and subjected to two inorganic N fertilizer regimes (no added N and 70 kg N ha-1 month-1). After germination, soil solution concentrations of dissolved organic C (DOC), dissolved inorganic N (DIN), dissolved organic N (DON), phenolics and H+ were measured at five depths down the soil profile over 3 months. The exploration of soil layers down the soil profile by roots caused transient increases in soil solution DOC, DON and phenolic concentrations, which then subsequently returned to lower quasi-stable concentrations. In general, the addition of N tended to increase DOC and DON concentrations while exposure to elevated pCO2 had the opposite effect. These treatment effects, however, gradually diminished over the duration of the experiment from the top of the soil profile downwards. The ambient pCO2 plus added N regime was the only treatment to maintain a notable difference in soil solution solute concentration, relative to other treatments. This effect on soil solution chemistry appeared to be largely indirect resulting from increased plant growth and a decrease in soil moisture content. Our results show that although plant growth responses to elevated pCO2 are critically dependent upon N availability, the organic chemistry of the soil solution is relatively insensitive to changes in plant growth once the plants have become established.