It 22 field trials, over a seven-year period, highly signifi.cantly^corr-elated with the uptake iigftfy iig"ln"ant torrelations weie fou-nd be-oiniirogen, the -l value being O.86' These tw"eeri niirate nitrogen to various depths in data, combin.ed-with.a factor for the efficiency the ioiiprofile at seiding time and the-uptake of uiilization of a nitrogenous fertilizer, were oi "it.-o!"" by th" aboie-ground portidn of used to derive an equation which predicls the turt"V u"t tru*".t.-Tht be;t correiatiotr *as amount of fertilizei nitrogen required for a found at a depth of 61 cm, where the I value particular barley yield' was 0.84. Barley yields were shown to be

The use of the isotopic 15N technique to measure asymbiotic N fixation in soils has been reported by very few workers, despite the obvious advantages of the technique in assessing the importance of this fixation in agricultural soils. The effect of glucose plus cellulose (0 and 0.5% glucose + 0.5% cellulose), glucose alone (0, 0.04, 0.2, 1.0 and 5.0% on dry soil weight basis), incubation temperature, method of soil aeration, and atmospheric composition on N fixation in soil in a closed system using 15N was investigated. Significant fixation was observed mainly when a readily available supply of energy such as glucose plus cellulose or glucose alone was added to the soil. Aerating the energy‐enriched soil by diffusion resulted in greater N fixation under an aerobic and anaerobic atmosphere than aerating by a continuous air flow in a closed system. The optimum glucose concentration was 1% at the 15 and 35 C incubation temperatures employed, while 5% glucose resulted in greater fixation at the 25 C temperature. Generally, more N was fixed at 15 and 25 C than at the 35 C incubation temperature.