HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Curtin, D. Articles by McCallum, F. M. Search for Related Content PubMed Articles by Curtin, D. Articles by McCallum, F. M. Agricola Articles by Curtin, D. Articles by McCallum, F. M. Related Collections Nutrient Management Nitrogen Soil Analysis

Soil Biology & Biochemistry

Hot Water-Extractable Nitrogen as an Indicator of Soil Nitrogen Availability

New Zealand Institute for Crop & Food Research, Private Bag 4704, Christchurch, New Zealand

^* Corresponding author (curtind{at}crop.cri.nz)

There is keen interest among soil scientists in identifying chemical assays that may be used as predictors of soil N mineralization potential. Our objective was to determine if hot water-extractable N (16-h extraction at 80°C) is a useful predictor of mineralizable N and plant N availability. In a group of 30 New Zealand soils, representing different management histories and parent materials, hot water extracted between 2.6 and 8.7% of total N. The extracted N consisted mainly (80%) of organic N, with the remainder being NH₄–N, generated by hydrolysis of heat-labile organic N. The C/N ratio of the extracted organic matter was relatively low (mean 8:1 vs. 11:1 for total organic matter), indicating that it included N-rich substrates (i.e., substrates likely to have high mineralization potential). However, about three-quarters of the extracted organic N was relatively recalcitrant, i.e., it did not hydrolyze to ninhydrin-reactive N (NH₄–N, amino acid-N, amino sugar N) when treated with 1 M HCl for 6 h at 80°C. The contribution of mineralized N to plant N uptake was measured using a greenhouse-grown oat (Avena sativa L.) crop, which received no added N. Hot water-extractable N accounted for 50% of the variation in plant N derived from mineralization (PNDM), compared with 16% for total soil N, 32% for anaerobically mineralizable N (AMN), and 24% for NH₄–N released by hot 2 M KCl. The best predictor of PNDM was N mineralized in a 28-d aerobic incubation at 20°C (79% of variability in PNDM explained).

Abbreviations: AMN, anaerobically mineralizable nitrogen • Aerobic N, nitrogen mineralized under aerobic conditions • HWC, hot water-extractable C • PNDM, plant nitrogen derived from mineralization