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

Mohr, Ramona M.; Janzen, H. H.; Entz, Martin H.

doi:10.4141/s96-026

Cited by 13 publications

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“…In a concurrent study using comparable termination treatments (Mohr et al 1998), the plant-available N supply in soil-incorporated residue treatments was 47 mg N pot -1 greater than that in surface-applied residue treatments. Based on this estimate, the volatile losses observed in the present study (14 mg N pot -1 ) account for less than onethird of the difference between soil-incorporated and surface-applied residue.…”

Section: Discussionmentioning

confidence: 93%

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

Mohr¹,

Janzen²,

Entz³

1998

Can. J. Soil. Sci.

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. 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...

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Section: Discussionmentioning

confidence: 93%

“…1). Additional replicates were used for determination of alfalfa N content, and in a complementary experiment to determine the effect of termination method on N mineralization and N uptake by subsequent crops (Mohr et al 1998). …”

Section: Methodsmentioning

confidence: 99%

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

Mohr¹,

Janzen²,

Entz³

1998

Can. J. Soil. Sci.

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“…Similar results have been reported for green manure crops: accumulations of soil inorganic N were lower under winter green manure crops terminated by herbicide application than in those terminated by tillage (Sarrantonio and Scott, 1988) Greater accumulations of inorganic N under the tilled system may be due to higher soil temperatures (Mitchell and Teel, 1977) and or improved soil moisture which may promote mineralization (Sarrantonio and Scott, 1988) In part, our observations may simply reflect greater N release from incorporated than from surficial residues (McKay et al, 1952; Wilson and Hargrove, 1986; Varco et al, 1993). Results of controlled‐environment studies suggest that differences in N release under herbicide‐terminated and tillage‐terminated systems are primarily a function of residue placement, rather than of termination method per se (Mohr et al, 1998a, 1998c); N mineralization of soil incorporated residues is enhanced with greater exposure of residues to soil microbial populations (Cogle et al, 1987) In addition, incorporation may reduce volatile N losses from alfalfa residues, and this may contribute somewhat to a larger available N supply (Janzen and McGinn, 1991; Mohr et al, 1998b).…”

Section: Resultsmentioning

confidence: 99%

“…Few studies have directly compared N release from alfalfa terminated by chemical means with that from tilled alfalfa. Under controlled conditions, incorporation of alfalfa residues resulted in more rapid N release from alfalfa residues and a larger short‐term supply of plant‐available N than where residues were retained on the soil surface (Mohr et al, 1998a, 1998c). In field experiments, termination of a green manure crop by herbicide application resulted in a 22% lower grain yield in a subsequent wheat crop than termination by tillage (Biederbeck and Slinkard, 1988) The observed yield reduction was attributed to delayed decomposition of herbicide‐treated residues, which may have reduced the available nutrient supply.…”

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confidence: 99%

Plant‐Available Nitrogen Supply as Affected by Method and Timing of Alfalfa Termination

et al. 1999

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alfalfa or alfalfa-grass stands in Manitoba and Saskatchewan is 6.5 years (Entz et al., 1995). This exceeds the Herbicide application may provide an alternative to intensive tilleconomic optimum of 4 to 5 years reported by Jeffrey age for the termination of alfalfa stands, but might alter N release and N availability to subsequent crops. Our objective was to deter- et al. (1993) and the duration required to attain maximine, under field conditions, the effect of timing and method of mum N benefits (Hoyt and Hennig, 1971; Heichel et termination on the pattern of N release from perennial alfalfa, and al., 1984). However, successful adoption of shorter-term on N uptake and yield of subsequent wheat crops. Four field experialfalfa stands requires management practices that effecments were initiated on perennial alfalfa (Medicago sativa L.) in tively terminate alfalfa, but maximize the benefits prosouthern Manitoba in 1992 and 1993. A factorial of three methods vided to subsequent crops. (herbicide, tillage, herbicide ϩ tillage) and two times of termination Intensive tillage, the usual method of terminating al-(early summer, after first alfalfa cut, and late summer, after second falfa, leaves the soil prone to erosion and moisture loss. alfalfa cut) was arranged in a randomized complete block design. A An alternative is to apply herbicides, either in the previspring-applied herbicide treatment was also included. Spring wheat ous summer or in the spring immediately before estab-(Triticum aestivum L.) was established after alfalfa termination. Soil NO Ϫ 3 content, plant N uptake, and yield were then monitored for one lishment of a subsequent crop, and leave residue standto two years. In three of four experiments, plant-available N in the ing on the soil surface. Broad-spectrum herbicides allow spring after termination was higher in tilled treatments than in treatreliable, cost-effective termination of alfalfa, and simulments receiving only herbicides. Regardless of method, plant-available taneously control weeds. In addition, standing surface N in the spring after termination was reduced when termination was residues reduce soil erosion and moisture loss, and may delayed from early to late season. Despite the lower short-term plantincrease soil moisture by trapping snow (Bullied and available N supply in early-and late-summer herbicide treatments, Entz, 1999).wheat yields in herbicide treatments were similar to or greater than Although using herbicides in place of tillage has many those in tillage treatments. Differences in the N content among treatapparent benefits, herbicide termination might affect ments diminished with time; by the fall of the second growing season after termination, differences in the cumulative available N supply

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“…In other studies, researchers have reported greater soil nitrate-N levels when alfalfa residues were incorporated into soil compared to those left on the soil surface (Biederbeck and Slinkard 1988;Mohr et al 1999). Tillage increases aeration and temperature promoting residue decomposition and N mineralization (Mitchell and Teel 1977), thus more N is released more quickly from incorporated residues (Wilson and Hargrove 1986;Varco et al 1993;Mohr et al 1998aMohr et al , 1998c. In addition, incorporation of alfalfa residues may reduce gaseous N losses and consequently result in a greater supply of mineral N (Janzen and McGinn 1991;Mohr et al 1998b).…”

Section: Soil Mineral Nmentioning

confidence: 96%

Influence of time and method of alfalfa stand termination on yield, seed quality, N uptake, soil properties and greenhouse gas emissions under different N fertility regimes

Malhi

Lemke

Schoenau

2009

Nutr Cycl Agroecosyst

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A field experiment was conducted in a 7-year old alfalfa stand to compare the influence of time and method of terminating alfalfa stands on crop yield, seed quality, N uptake and recovery of applied N for wheat (Triticum aestivum L.) and canola (Brassica napus L.), soil properties (ammonium-N, nitrate-N, bulk density, total and light fraction organic C and N), and N 2 O emissions on a Gray Luvisol (Typic Cryoboralf) loam near Star City, Saskatchewan, Canada. The treatments were a 3 9 3 9 4 factorial combination of three termination methods [herbicide (H), tillage (T), and herbicide ? tillage (HT)], three termination times (after cut 1 and cut 2 in 2003, and in spring 2004) and four rates of N (0, 40, 80 and 120 kg N ha -1 ) applied at seeding to wheat-canola rotation from 2004 to 2007.In the termination year, soil nitrate-N was considerably higher in T or HT treatments than in the H treatment and decreased with delay in termination. In the first crop year, seed and straw yields of wheat grown on T and HT treatments were significantly greater than H alone (by 1,055-1,071 kg seed ha -1 and by 869-929 kg straw ha -1 ), due to greater content of soil available N in T treatments. Yields decreased with delay in termination time. In general, yield and N uptake in seed and straw, and protein concentration tended to increase with increasing N rate. A greater yield increase occurred on the H compared to T and HT treatments from the first increments of N applied. Nitrous oxide emissions were generally low and there were no treatment differences evident when cumulative 4-year N 2 O-N losses were compared. Appropriate N fertilization was able to compensate for yield reductions due to delayed termination timing, but could not do so entirely for yield reductions on the H compared to T or HT termination method. The amounts of TOC, TON, LFOC and LFON after four growing seasons were usually higher or tended to be higher under H treatment than under T treatment in the 0-5 cm soil layer, but the opposite was true in the 5-10 cm or 10-15 cm soil layers.

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

Cited by 13 publications

References 20 publications

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

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

Plant‐Available Nitrogen Supply as Affected by Method and Timing of Alfalfa Termination

Influence of time and method of alfalfa stand termination on yield, seed quality, N uptake, soil properties and greenhouse gas emissions under different N fertility regimes

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