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Soil Nitrate Loss During Irrigation: Enhancement by Plant Roots 1
Author(s) -
Volz M. G.,
Ardakani M. S.,
Schulz R. K.,
Stolzy L. H.,
McLaren A. D.
Publication year - 1976
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1976.00021962006800040023x
Subject(s) - hordeum vulgare , loam , irrigation , nitrate , chemistry , agronomy , organic matter , nitrogen , soil water , dns root zone , poaceae , environmental science , soil science , biology , organic chemistry
Since roots can both absorb NO ‐ 3 and supply organic matter for NO ‐ 3 reduction by soil microbes, the influence of a root system on NO ‐ 3 N loss from soil solution during irrigation was studied. Two Hanford sandy loam plots (Typic Xerorthent), one fallow, and the other planted to CM‐67 barley ( Hordeum vulgare L.), were ponded for 44 hours with a solution containing 100 ppm N and 46 ppm CI‐ (tracer for NO ‐ 3 ) as KNO 3 and CaCl 2 , respectively. Nitrate — N, NO ‐ 2 ‐N, NH + 4 ‐N, and Cl‐ concentrations in soil solution were determined and related to N uptake by roots and microbial transformation of NO ‐ 3 . During irrigation, concentrations of NO ‐ 3 ‐N were lower in most soil solution samples from 0 to 60 cm under barley than in those from the fallow plots. However, Cl‐concentration profiles were identical in both plots to a depth of 45 cm. While nitrate uptake by barley in the top 15 cm led to some solution N loss, soil NO ‐ 2 and NO ‐ 2 reduction reactions are thought to have been responsible primarily, especially in deeper layers, after 26 hours. Data also indicate that, during irrigation, organic C is produced in the root zone of barley and that redox potentials in the planted plot decreased relative to those in the fallow plot. This organic C, percolating with NO ‐ 3 solution, is thought to have facilitated NO ‐ 3 loss both in, and below the root zone, by stimulating microbial activity and by decreasing redox potentials.