Depressive Influence of Certain Higher Plants on the Accumulation of Nitrates in Soil¹

Abstract

A partial review of published experiments which appeared to have a bearing on this subject was compiled by two of the present w'riters in 1913 (4). 3 In this review, results were grouped under two headings; (a) experiments showing higher nitrate content under plants than in fallow land, (b) experiments indicating a depressed nitrate formation under plants. It is significant that the soils in which it was found that the nitrate content under living plants was higher than in similar soil under fallow were all made during the earlier stages. of growth of the plants and that the analyses that indicated a. depressed nitrate formation were all made at a later stage or at maturity.A short time afterwards Russell (7) reported some experiments on this subject and also reviewed some of the literature. His own experiments, and most of those which he cited, indicated only a depressed nitrate formation in soil bearing plants.It should be noted that with the exception of those which did not indicate a depression of nitrate formation by the crop all of the analyses reported by Russell were made when the plants had reached maturity.Russell cited an investigation by \Varington (9) who found an apparent disappearance of nitrate nitrogen on cropped land. \Varington suggested that the crop may have taken up this nitrogen and afterwards lost it, presumably to the air. Russell, howeyer, holds that the disappearance of nitrate nitrogen in the cropped soil is more properly to be attr~buted to diminished production and further that the diminished production is not to be traced to the effect of the crop 10n the 'temperature ot: moisture content of the soil.Beside the theory advanced by Vvarington to account for the disappearance of nitrates in soil accompanying the growth of plants, one has been proposed by Deherain (r) to the effect that the growing plant by removing moisture from the soil

Inhibition of Nitrification by Climax Ecosystems

“…Smith et al (1968) felt that the evidence indicated that the pronounced increase in numbers of nitrifiers resulting from the clear-cutting of a forest ecosystem was due, not to changes in physical conditions, but to elimination of uptake of nitrate by the vegetation, or to a reduction in production of substances inhibitory to the autotrophic nitrifying population. Lyon, Bizzell, and Wilson (1923) attributed the lower total nitrate in cropped as opposed to uncropped soil (Russell, 1914) to an increased nitrate uptake by microorganisms, stimulated by root excretions with a high CjN ratio. Our own results definitely suggest that the increase in nitrifiers and nitrate were probably not due to elimination of uptake of nitrate by the vegetation.…”

“…Likens, Bormann, and Johnson (1969) reported a 100-fold increase in nitrate loss in the same ecosystem after cutting. Theron (1951), in discussing the reasons for the low nitrate level in grasslands in Africa, gave two arguments against the idea of Lyon et al (1923) that the low nitrate was due to the excretion of carbonaceous material by plants: (1) the amount of carbonaceous material required to bring about the result was too great to be excreted by the roots of the plants; and (2) when such carbonaceous material is added to a soil not only the nitrates but also the ammonia are reassimilated by microorganisms, whereas under grass ammonia is found in greater quantities than in cultivated soils. Lyon, Bizzell, and Wilson (1923) attributed the lower total nitrate in cropped as opposed to uncropped soil (Russell, 1914) to an increased nitrate uptake by microorganisms, stimulated by root excretions with a high CjN ratio.…”

The influence of plants on the mineralization of nitrogen and the maintenance of organic matter in the soil

“…The supply of energy which would thus be made available stimulates the development of nitrate-consuming microorganisms and all mineral nitrogen not immediately absorbed by the plant is reconverted to microbial protoplasm (Lyon & Wilson, 1921;Lyon, Bizzell & Wilson, 1923;Russell, 1937, p. 553). The supply of nitrogen available to the plant is greatly decreased and hence mineralization appears to be depressed.…”

Biological nitrification inhibition (BNI)-Is there potential for genetic interventions in the Triticeae?

“…Often ammonium levels exceeded nitrate concentrations by a factor of ten, indicating that ammonium was not limiting nitrification. Influence of vegetation in inhibiting nitrification was often suspected, but not proven (Lyon et al 1923, Donaldson and Henderson 1990a, 1990b, Steltzer and Bowman 1998, Lewis and Likens 2000, Christ et al 2002, Lovett et al 2004. Certain forest trees (such as Arbutus unedo) are reported to suppress soil nitrification and nitrous oxide emissions, and it is hypothesized to be due to biological molecules (i.e.…”