Nitrogen nutrition of Douglas-fir (Pseudotsuga menziesii) on strongly acid sandy soil

✍ Scribed by Arjan J. Gijsman

• Publisher: Springer
• Year: 1990
• Tongue: English
• Weight: 585 KB
• Volume: 126
• Category: Article
• ISSN: 0032-079X
• DOI: 10.1007/bf00041369

✦ Synopsis

Three-year old Douglas-fir trees were grown on a strongly acid sandy soil (pH-H20 3.87), fertilized with three different sources of nitrogen (nitrate, ammonium, or both) at three levels of N-supply (10, 50, 100 mg kg-1). Rhizosphere pH was determined and calculations were done on the relative contribution of both ammonium and nitrate uptake to total N uptake, and on the H + excretion by the roots.

With ammonium nutrition the rhizosphere pH was slightly lower than the bulk soil pH, without any relationship with N level. With nitrate or ammonium nitrate nutrition, the rhizosphere pH was slightly lower than the bulk soil pH at low levels of N supply, but at higher N-levels a shift to a more alkaline rhizosphere occurred with these N-sources.

Except with very low nitrate availability, the contribution of nitrate to total N uptake was higher than the nitrate fraction in N input. This may be caused by differences in preferred N source and in mobility of ammonium and nitrate in the soil. The calculated H + excretion was in agreement with the pattern in rhizosphere pH measured. Values were similar to those commonly found for other species.