Tree girdling increases soil N mineralisation in two spruce stands

Productivity of 3 different 2-year crop rotations, namely continuous wheat, wheat-chickpea, and wheat-fallow, was measured over 4 consecutive seasons beginning in 1991-92 at the ICARDA station, Tel Hadya, Syria. Nitrogen (N) fertiliser (30 kg N/ha at sowing) was broadcast every other year in the continuous wheat only. 15N-labelled fertiliser was used to quantify the amount of nitrogen supplied to the crops through current and past applications of fertiliser and by N2 fixation. The remaining N in the crop was assumed to come from the soil. In any single season, wheat yields were unaffected by rotation or N level. However, 2-year biomass production was significantly greater (32%, on average) in the continuously cropped plots than in the wheat-fallow rotation. On average, <10% of the N in the wheat crop came from fertiliser in the season of application, and <1·2 kg N/ha of the residual fertiliser was recovered by a subsequent wheat crop. Chickpea fixed 16-48 kg N/ha, depending on the season, but a negative soil N budget was still likely because the amount of N removed in the grain was usually greater than the amount of atmospheric N2 fixed. Uptake of soil N was similar in the cereal phase of all 3 rotations (38 kg N/ha, on average), but over the whole rotation at least 33% more soil N was removed from continuously cropped plots than from the wheat-fallow rotation, suggesting that the latter is a more sustainable system. A laboratory study showed that although wheat and chickpea residues enhanced the gross rate of N mineralisation by c. 50%, net rates of N mineralisation were usually negative. Given the high C/N ratio of the residue, immobilisation, rather than loss processes, is the likely cause of the decline in the mineral N content of the soil. Consequently, decomposition of crop residues in the field may in the short term reduce rather than increase the availability of N for crop growth.

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Priming effect of biuret addition on native soil N mineralisation under laboratory conditions

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2005.02.034 ◽

2005 ◽

Vol 37 (10) ◽

pp. 1959-1961 ◽

Cited By ~ 3

Author(s):

J.M. Xue ◽

R. Sands ◽

P.W. Clinton ◽

T.W. Payn ◽

M.F. Skinner

Keyword(s):

Priming Effect ◽

N Mineralisation ◽

Soil N ◽

Laboratory Conditions ◽

Native Soil

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Effects of wildfire and topography on soil nitrogen availability in a boreal larch forest of northeastern China

International Journal of Wildland Fire ◽

10.1071/wf13218 ◽

2015 ◽

Vol 24 (3) ◽

pp. 433 ◽

Cited By ~ 14

Author(s):

Jian-jian Kong ◽

Jian Yang ◽

Haiyan Chu ◽

Xingjia Xiang

Keyword(s):

Soil Nitrogen ◽

Northeastern China ◽

Larch Forest ◽

N Availability ◽

N Mineralisation ◽

Soil N ◽

Inorganic N ◽

Soil N Availability ◽

N Supply ◽

Burned Site

Both topography and wildfire can strongly affect soil nitrogen (N) availability. Although many studies have examined the individual effects of fire and topography on N, few have investigated their combined influences and relative importance. In this study, we measured soil extractable inorganic N concentrations, N mineralisation rates, and in situ soil inorganic N supply rates at 36 plots in three topographic positions (north-facing, south-facing and flat valley bottom) of burned and unburned sites in a boreal larch forest of northeastern China. Our data showed that wildfire significantly increased soil N availability, with mean soil extractable inorganic N concentrations, N mineralisation rates and N supply rates being 63, 310 and 270% higher in the burned site 1 year following fire. Additionally, soil N availability in the unburned site was significantly greater on the north-facing slope than on the south-facing slope, though this pattern was reversed at the burned site. Wildfire and topography together explained ~50% of the variance in soil N availability, with wildfire explaining three times more than topography. Our results demonstrate that wildfire and topography jointly affected spatial variations of soil N availability, and that wildfire decreased the influence of topography in the early successional stage of this boreal larch ecosystem.

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Availability of nitrogen from municipal biosolids for dryland forage grass

Canadian Journal of Plant Science ◽

10.4141/p99-160 ◽

2000 ◽

Vol 80 (3) ◽

pp. 575-582 ◽

Cited By ~ 17

Author(s):

B. J. Zebarth ◽

R. McDougall ◽

G. Neilsen ◽

D. Neilsen

Keyword(s):

N Uptake ◽

Forage Yield ◽

Nitrate Content ◽

First Year ◽

Forage Grass ◽

N Mineralisation ◽

Soil N ◽

Total N ◽

Available N ◽

Municipal Biosolids

A 3-yr study, initiated in 1996, evaluated the availability of N from applied biosolids for dryland forage grass production under the cool, continental climatic conditions in central British Columbia. Treatments included 600 (LB), 1200 (MB) and 1800 (HB) kg total N ha−1 applied as municipal biosolids, a single application of 150 kg N ha−1 as urea in the first year of the experiment (SF), a multiple application of 150, 60 and 30 kg N ha−1 as urea in the first, second, and third years of the experiment (MF), and a control that received no biosolids or urea. All treatments were roto-tilled to 15-cm depth and seeded to a mixture of four grasses. The LB treatment was predicted to supply a similar quantity of plant-available N as the MF treatment, assuming 25, 10, and 5% of biosolids N is available in the first, second, and third year, respectively. Soil N fertility was poor as indicated by the very low forage yield and N uptake in the control, and minimal apparent net soil N mineralisation. Recovery of urea N in the crop over 3 yr averaged only 27%, likely reflecting net immobilisation in this recently broken site and accumulation of N in non-harvested portions of the crop. Cumulative recovery of N from biosolids in the harvested forage averaged only 11%. However, the fertiliser N equivalency of the biosolids N (ratio of recovery of biosolids N to urea N) was estimated at 41%, close to the predicted value of 40%. Forage yield and N uptake were similar for the LB and MF treatments, suggesting that actual biosolids N availability was similar to that predicted. Limited forage yield increase for the HB compared with the MB treatment early in the experiment, and high forage nitrate content for the HB treatment in the first year, suggest that the HB treatment initially supplied an excessive quantity of N. Both urea and biosolids applications increased cumulative uptake of other macro- and micro-nutrients, with forage Cu concentrations reaching values in the establishment year that may be of concern for some animal species. Monitoring of forage NO3 and Cu concentrations is advisable where biosolids are applied. Key words: Phleum pratense L., Dactylis glomerata, Bromus inermis, Bromus biebersteinii, soil N mineralisation, NO3 toxicity

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