Soil nitrogen. VI.—correlations between laboratory measurements of soil mineral‐N and crop yields and responses in pot and field experiments

Abstract

Soil samples from sites of field experiments testing S-fertilisers for karley, potatoes, kale and grass were used for pot experiments with ryegrass and also t o measure ' available '-N in the laboratory.Mineral-K in the fresh soil (Mineral-Nf,,h) and the increases when fresh or re-wetted airdry soils were incubated (A Mineral-Nf,,,i, or 4 Mineral-Nnir-dry) were determined. These were more highly correlated with organic C than with total N content of the soils. Among ' available '-N measurements, Mineral-xfresh and 4 h ' l i n e r a l -S a~~d r y were most correlated with one another.The yields of dry matter and N uptake by ryegrass grown in unfertilised soil, or with two rates of applied N, were significantly correlated with Mineral-Nfresll or A hlineral-Nair.dry a t each level of nitrogen, but not with 4 Minera1-NfreSh.The unfertilised yields of barley in field experiments were significantly correlated with Mineral-Nfresh, A Mineral-Xab-,jry, and total N ; responses b y barley t o 0.5 cwt. of N/acre were significantly negatively correlated with all three ' available '-N measurements and with total X. Unfertilised yields of potatoes were significantly correlated with the three ' available '-N measurements and responses t o 1.0 cwt. of N/acre were significantly negatively correlated with A Wineral-Nai,.dry and total N. Mineral-"f,.,,h and A &1incral-Nair.dry are suggested as useful measurements for advisory purposes.

Effect of Ammonium and Nitrate Forms of Nitrogen and Restricted Water Supply on Growth and Nitrogen Uptake of Wheat

“…1,1966 With adequate water, wheat produced more dry matter and took up more N with calcium nitrate than with ammonium sulfate (Fig. 1).…”

Field evaluation of several chemical indexes of soil nitrogen availability

“…There have been many attempts to find an accurate chemical or biological index of soil N availability that could be used to improve N fertilizer recommendations (Keeney, 1982;Meisinger, 1984;Stanford, 1982). The indexes have fallen into three main categories: (A) biological incubation methods that measure the N mineralized during various types of incubations (Fox and Piekielek, 1984;Keeney and Bremner, 1966); (B) direct measurement of inorganic N (Carter et al, 1974;Gasser, 1961;Soper et al, 1971;Stanford et al, 1977); and (C) a fraction of N released from * Paper No 8211 of the Journal series of The Pennsylvania Agricultural Experimental Station. 83 organic matter by chemical treatment of the soil (Fox and Piekielek, 1978a,b;Gianello and Bremner, 1986a,b;Jenkinson, 1968;Keeney andBremner, 1966, Oien andSelmer-Olsen, 1980;Smith and Stanford, 1971).…”

The Effect of Clearing a Tropical Forest Soil

“…Mechanical analyses were done by Piper's (1944) beaker method, soil porosity by the method described by Baver (1956), and water-stable aggregates by a wet-sieving method (Williamson et al, Total N and. organic C were estimated by a Kjeldahl and the Walkley and Black (1934) method respectively; pH was measured with a glass electrode using an H,O :soil ratio of 2-5 : I ; NH,-N and NO,-N were determined by the microdiffusion method of Bremner and Shaw (1955), and A Min-N,, which is a measure of mineralizable N (Gasser, 1961) every six months until March 1960. Be P ore it disappeared, the surface caused the surface of the soi P in the exposed plots to sink below t i at of 1956).…”