Increased proportion of active soil N in Breton loam under cropping systems with forages and green manures

Wani, S P and McGill, W B and Haugen-Kozyra, K L and Juma, N G (1994) Increased proportion of active soil N in Breton loam under cropping systems with forages and green manures. Canadian Journal of Soil Science, 74 (1). pp. 67-74. ISSN 1918-1841

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Total soil N and N mineralization rate partially ctririct&iie the influence olvariouJcropping systems on the growth of.sequent.crop.s in a rotation' The objectives of this study were to (1) quantify the relationship among cropping system, total N and mineralizable N, and (2) compare amount of N mineralized under'controlled laboratory conditions-with pianl N uptake under green]ouse conditi:ns. Three cropping systems that have been in operation between 9 and 60 yr on a Gray-Luvisol (Breton loam; were ^selected . They included: (1) an ag.lo: ecological (lnn) d-yr rotation involving fabibeans as gr-een manure (AER1 sampled after the_first lababean crop-?nq AER? ,u-pied after 3 yr of continuous forage)l (2) continuous grain system (CG), with fertilizer N at 90 kg ha-'^yr- '; inttrated in 1980 and considered established in f"98i; i3) a classicial Ereton iotation (CBR) involving 9]o-ng-term (ca. 1930) 5-yr rotation with forages and cereals and no return of.ciop residues (CBR1 fertilized with P-K-S and CBR2 unfertilized). We cautio_n that not all ohlses of each rotation were sampled: bur conclusions pertain to N-mineralization potential in soil samples immediately preceding barley as sequent crop in each rotation. The rate ofN mineralization declined with time, but it remained greater than iero aftei 20 wi< of incirbation in all soils. Mineral-N accumulation at 20 wk followed the order AER1 > AER2 > > CBRI > CBR2 : CG. Mineralizable soil N, following one cycle of the AER rotation, was almost double that following 60 yr of the CBR rotation. Data for mineral-N accumulation under laboratory conditions were described best by a single-component expo-n-ential model. Legume-based rotations were associated with increased total soil N and a greater proportional increase in active N than in total soilN. Active N was least in soil under the CG system. The incubation-extraction procedure resulted in higher estimates of mineralizable N than did the plant-uptake method; liowever, the ranking of N-supplying power of soils was the same.

Item Type: Article
Uncontrolled Keywords: Cropping systems, Gray Luvisol, N mineralization, soil quatity, Typic Cryoboralf
Subjects: Others > Soil Science
Depositing User: Users 6 not found.
Date Deposited: 03 Nov 2011 05:44
Last Modified: 03 Nov 2011 05:46
Official URL:
Funders: Alberta Agriculture Research Institute, Natural Sciences and Engineering Research Council of Canada
Acknowledgement: The Farming for the Future Program of the Alberta Agriculture Research Institute, as well as Natural Sciences and Engineering Research Council of Canada, provided financial support. We thank J. Konwicki, C. Nguyen, J. Brown and J. Thurston for technical assistance and S. Nakashima for word processing asslstance.
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