Soil mineral nitrogen

Percentage of labelled fertilizer nitrogen left in soil at harvest, and percentage increase in soil mineral nitrogen at harvest caused by fertilizer ... 

Foulkes, M.J., Sylvester-Bradley, R. and Scott, R.K. 1998. Evidence for differences between winter wheat cultivars in acquisition of soil mineral nitrogen and uptake and utilisation of applied fertiliser nitrogen. Journal of Agricultural Science 130 29-44. 

SNS=Soil mineral nitrogen (SMN)+estimate of nitrogen already in the... 

CDU in pure form is a white powder. It is made slowly available to the soil solution by nature of its limited solubihty in water. Once in the soil solution, nitrogen from CDU is made available to the plant through a combination of hydrolysis and microbial decomposition. As with any CRE which is dependent on microbial action, the mineralization of CDU is temperature dependent. Product particle size has a significant effect on CDU nitrogen release rate. Smaller particles mineralize more rapidly because of the larger surface contact with the soil solution and the microbial environment. The rate of nitrogen release is also affected by pH because CDU degrades more rapidly in acidic soils. 

Arable farmers in the UK rarely grow more than one crop in a year, but horticulturalists may grow two or more crops in a year on the same soil, so the question of crop sequences is more intense for them, particularly as Brassica vegetables, such as cabbages and brussel sprouts, can leave large organic as well as mineral nitrogen residues. 

Goh KM, Haynes RJ (1986) Nitrogen and agronomic practice. In Haynes RJ (ed) Mineral nitrogen in the plant-soil system. Academic Press, Orlando, pp 379—468 Golchin A, Oades JM, Skjemstad JO, Clark P (1994) Soil structure and carbon cycling. Aust J Soil Res 32 1043-1068... 

Marsh et al. [47] have described an apparatus based on an autoanalyser system for the automatic preparation of soil extracts for mineral nitrogen determination. It consists of a reagent adder, which adds the correct volume of extractant for an approximately weighed amount of soil, and a sample preparation unit, which mixes, filters, dilutes and loads samples on to an autoanalyser sampler. A labour saving of 60% is achieved in this method compared to manual method. Examples are given of the determination of nitrate plus nitrate nitrogen and ammonium nitrogen. 

Haynes, R. J. Mineral Nitrogen in the Plant-Soil System Academic Orlando, FL, 1986 p 483. 

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