Nitrogen Accumulation in Soil as Influenced by the Cropping System 1

Wheat was grown continuously after forage the forage swards, two to six years, did not crops or fallow of a fallow-wheat rotation, affect subsequent wheat yields. Total N and witir fertilizer being applied to only the fifth organic matter in the surface soil changed wheat crop. Yields of ihe flrst, second, fourth only slightly under ,the forage swards. and fifth ivheat crops succeeding alfalfa were Mineralizable N and chlorophyll units were greater than those succeeding iallow by 71, in much greater amounts in the first year 82,75 and,68Va, respectively. The third crop following alfalfa, alone.or in mixture with was frozen. Yields were slightly less after a bromegrass, than following the other cro,ps, bromegrass-alfalfa mixture than after alfalfa but the differences had diminished somewhat alone. Yields after red fescue or bromegrass by the fifth year.

Section: Soilmentioning

confidence: 99%

Effect of Alfalfa and Grasses on Yield of Subsequent Wheat Crops and Some Chemical Properties of a Gray Wooded Soil

Hoyt¹,

Hennig²

1971

“…Significant N contributions made by alfalfa to the available N supply are well-documented (Lyon and Bizzell 1933;Hoyt and Hennig 1971;Bruulsema and Christie 1987) but the effect of termination method on the fertilizer value derived from established alfalfa stands has not been determined. Efficient utilization of alfalfa-derived N requires a better understanding of the magnitude of volatile N losses from alfalfa following termination.…”

mentioning

confidence: 99%

Nitrogen dynamics under greenhouse conditions as influenced by method of alfalfa termination. 1. Volatile N losses

Mohr¹,

Janzen²,

Entz³

1998

. 1998. Nitrogen dynamics under greenhouse conditions as influenced by method of alfalfa termination. 1. Volatile N losses. Can. J. Soil Sci. 78: 253-259. Use of herbicide to terminate alfalfa (Medicago sativa L.), while reducing soil erosion, could conceivably enhance volatile N losses from alfalfa residues. A controlled environment study was conducted to determine the effect of termination method on the quantity of NH 3 volatilized from residues of alfalfa. A factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (incorporated, surface applied) was applied to alfalfa. Treatments were incubated in a flow-through chamber in the greenhouse for 95 d during which NH 3 and CO 2 evolution was measured periodically. After 95 d, 8% of surface applied legume N was lost as NH 3 in tillage treatments compared to 12% in herbicide treatments. These losses amounted to 3% and 4% of total legume N in tillage and herbicide treatments, respectively. Incorporation of alfalfa residue essentially eliminated volatile N losses. Termination method had comparatively less effect on NH 3 evolution than residue placement although herbicide application tended to increase the proportion of alfalfa N lost via volatilization. Residue incorporation increased cumulative CO 2 evolution regardless of termination method. Results of this study suggest that termination methods in which alfalfa residue is retained on the soil surface may result in significant volatile N losses which could diminish the fertilizer value derived from alfalfa residues. However, these N losses do not necessarily preclude the adoption of herbicide termination of alfalfa given the potential reductions in soil erosion and moisture loss which may be associated with this management practice. Key words:Volatile N losses, NH 3 evolution, termination method, alfalfa, herbicide, tillage, greenhouse Mohr, R. M., Janzen, H. H. et Entz, M. H. 1998. Cinétique de l'azote en culture sous serre selon la méthode de destruction d'une prairie de luzerne. 1. Perte de N volatil. Can. J. Soil Sci. 78: 253-259. L'emploi des herbicides pour interrompre la culture de la luzerne (Medicago sativa L.), s'il aide à freiner l'érosion du sol, pourrait en revanche accroître les déperditions de N sous forme gazeuse à partir des restes de la culture. Une étude en conditions contrôlées a été réalisée pour déterminer les effets de la méthode de destruction de la prairie de luzerne sur la quantité de NH 3 volatilisée à partir des restes de la culture. Nous comparions deux méthodes de destruction : chimique ou mécanique et deux méthodes d'épandage des résidus : avec incorporation ou en surface, selon un protocole factoriel. Les sols de chaque traitement étaient mis à incuber pendant 95 j sous serre dans une enceinte à circuit ouvert et on mesurait à divers intervalles de temps les émissions de NH 3 et de CO 2 . Au bout des 95 j, 8 % du N des restes de luzerne épandus en surface étaient perdus en NH 3 après destruction mécanique contre 12 % après destructio...

“…Contributions made by alfalfa to the soil N supply have long been recognized (Lyon and Bizzell 1933;Boawn et al 1963;Hoyt and Hennig 1971;Campbell et al 1993). However, poor synchrony between N release from legume residues and crop N demands may reduce the fertility benefits of the legume (Huntington et al 1985;Westermann and Crothers 1993).…”

mentioning

confidence: 99%

Nitrogen dynamics under growth chamber conditions as influenced by method of alfalfa termination 2. Plant-available N release

Mohr¹,

Janzen²,

Entz³

1998

. 1998. Nitrogen dynamics under growth chamber conditions as influenced by method of alfalfa termination 2. Plant-available N release. Can. J. Soil Sci. 78: 261-266. Herbicide application has been proposed as an alternative to tillage for termination of established alfalfa (Medicago sativa L.) stands but it may alter the pattern and amount of N released from alfalfa residues. A controlled environment study was conducted to investigate the effect of termination technique on the availability of N to four barley (Hordeum vulgare L.) crops. Four treatments consisting of a factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (surface, incorporated) were established. Nitrogen uptake by the four consecutive crops of barley was measured during a 125-d period after termination. Termination method, particularly residue placement, strongly affected N release from alfalfa residues. Nitrogen accumulation by the initial barley crop accounted for >60% of cumulative N uptake in incorporated treatments compared with 39% and 24% for herbicide and tillage treatments in which alfalfa residue was surface applied. Herbicide application also slightly increased N uptake by the initial barley crop. Nitrogen uptake by subsequent barley crops was not affected by termination method; however, cumulative N uptake remained substantially greater for incorporated treatments throughout the 125 d experiment. Effects of residue particle size on N release from alfalfa residues were small. These results suggest that herbicide termination in which residue is retained on the soil surface may reduce the short-term plant-available N supply. Provided that mineralization is sufficient to meet the N needs of subsequent crops, maintaining a smaller reservoir of soil inorganic N may be beneficial in reducing the potential for leaching or denitrification losses. Le N absorbé par la première culture d'orge correspondait à plus de 60 % de l'exportation cumulative de N dans les traitements avec incorporation, contre, respectivement, 39 et 24 % pour le traitement herbicide et pour le traitement cultural avec localisation des restes en surface. La méthode chimique donnait également lieu à un léger accroissement de l'absorption de N par la première culture d'orge. L'absorption du N par les soles subséquentes d'orge était sensiblement la même indépendamment de la méthode de destruction utilisée, bien que l'exportation cumulative de N par chaque culture demeurat sensiblement plus forte dans les traitements avec incorporation tout au long de l'expérience. Les effets de la grosseur particulaire des restes sur la libération du N de la luzerne étaient de faible importance. Ces observations incitent à conclure que la destruction chimique serait susceptible de réduire la disponibilité à court terme du N assimilable. Pour autant que le degré de minéralisation soit suffisant pour satisfaire au besoin en azote des cultures subséquentes, le maintien d'un réservoir moins abondant de N minéral dans le sol aurait l'avantage ...