Soil tests for predicting nitrogen supply for grassland under controlled environmental conditions. (22nd April 2014)

• Record Type: Journal Article
• Authors: MCDONALD, N. T.; WATSON, C. J.; LAUGHLIN, R. J.; LALOR, S. T. J.; GRANT, J.; WALL, D. P.
• Editors: Richards, Karl; Fenton, Owen; Watson, Catherine
• Is Part Of: Journal of agricultural science. Volume 152(2014)Supplement 1
• Page Start: 82
• Page End: 95
• Publication Date: 2014-04-22
• Subjects: Agriculture -- Periodicals; 630.5
• DOI: 10.1017/S0021859614000264
• Languages: English
• ISSNs: 0021-8596

Abstract

SUMMARY: Mineralized soil nitrogen (N) is an important source of N for grassland production. Some soils can supply large quantities of plant-available N through mineralization of soil organic matter. Grass grown on such soils require less fertilizer N applications per unit yield. A reliable, accurate and user-friendly method to account for soil N supply potential across a large diversity of soils and growing conditions is needed to improve N management and N recommendations over time. In the current study, the effectiveness of chemical N tests and soil properties to predict soil N supply for grass uptake across 30 Irish soil types varying in N supply potential was investigated under controlled environmental conditions. The Illinois soil N test (ISNT) combined with soil C : N ratio provided a good estimate of soil N supply in soils with low residual mineral N. Total oxidized N (TON) had the largest impact on grass dry matter (DM) yield and N uptake across the 30 soil types, declining in its influence in later growth periods. This reflected the high initial mineral N levels in these soils, which declined over time. In the current study, a model with ISNT-N, C : N and TON (log TON) best explained variability in grass DM yield and N uptake. All three rapid chemical soil tests could be performed routinely on field samples to provide an estimate of soil N supply prior to making N fertilizer application decisions. It can be concluded that these soil tests, through their assessment of soil N supply potential, can be effective tools for N management on grassland; however, field studies are needed to evaluate this under more diverse growing conditions.