The N_min‐method – an aid to integrating various objectives of nitrogen fertilization

Abstract

There is increasing interest in the rate and timing of N-fertilization from both an economical and an ecological point of view. Fertilizer recommendations for a variety of aims can be made using the N,,,-method, as shown by experiments on deep rootable loess loam soils.Yields of cereal crops and sugar were increased by 2-3 dtiha by application of the N,,-method. The N,,,-method led to a reduction in the rate of fertilizer application by 30 kg N h a with sugar beet.Any stipulated NO3 level in leaf vegetables can be met, If N is fertilized according to N,,,-method. The necessary data for many vegetable crops are given. In particular low nitrate content in spinach and lettuce at high yield was achieved without loss of yield by adjusting both their NO3 and CI nutrition.Leaching of nitrate out of soils often follows the application of too much fertilizer, but fertilization errors can be avoided and leaching reduced if the N,,-method is used.Applications and limitations of the N,,,-method are discussed. Die N&-Methode -Em Hilfsmittel zuc Integration verschiedener Ziele bei der N-DiingungDie Anforderungen an die Dosierung der N-Diingung sind gestiegen. Neben okonomischen finden okologische Fragen verstarkt Beachtung.Die N,,,-Methode ist, wie Versuche auf tiefgriindigem Lonlehm zeigen, ein brauchbares Hilfsmittel zur Anpassung der N-Diingung an die jeweiligen Zielvorgaben.Steigerungen der Ertrage um 2-3 dt/ha werden in der Praxis bei Getreide und Zucker durch Anwendung der N,,-Methode erzielt. Die N,,,-Analyse fiihrt bei Zuckerriiben zu einer Verminderung der Diingung urn ca. 30 kg N h a .Vorgegebene Hochstwerte der Nitratgehalte fur Blattgemiise lassen sich einhalten, wenn die N-Diingung auf der Grundlage der N~,-Methode dosiert wird. 149, 428-440 (1986) N(min)-analysis 429

Estimation of soil nitrogen supply in potato fields using a plant bioassay approach

“…Determination of soil mineral N content in spring (i.e., N min test) (Wehrmann and Scharpf 1986) measures one component of soil N supply. The pre-sidedress soil nitrate test (Magdoff 1991) provides an index of relative soil N supply through measurement of soil NO 3 -N content early in the growing season.…”

Soil inorganic nitrogen content in commercial potato fields in New Brunswick

“…Spring soil inorganic N measurements have been used in making fertilizer N recommendations for potato in some potato production areas, for example in Germany (Wehrmann and Scharpf 1986). However, Bélanger et al (2001) concluded that preplant measurement of soil NO 3 content, or soil inorganic N content, did not adequately predict the optimal fertilizer N rate for potato in Atlantic Canada when used alone.…”

Decreasing Nitrate Leaching in Vegetable Crops with Better N Management

“…However, the measurement of the magnitude of the soil mineral nitrogen (SMN) pool accessible to plant roots is not very reliable when there are periods with high rainfall during the growing season, or under high temperatures, or in soils with high organic matter contents (Wehrmann and Scharpf 1986). Stoniness is also a factor, as laboratory results in milligrams per kilogram need to be converted to kilograms per hectare to a given sample depth using an assumed bulk density for the soil.…”

“…In the Nmin method (Wehrmann and Scharpf 1986), the N-fertiliser requirement of the crop (N rate ) is estimated as N rate = N target − N min . N target is a specific target level of nitrogen that must be available for maximum growth and yield to occur (Feller and Fink 2002); the target value is determined experimentally and takes into account both nitrogen already in the soil and nitrogen supplied by the application of fertilisers.…”