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1.
Attributes affecting residual benefits of N<Subscript>2</Subscript>-fixing mungbean and groundnut cultivars 总被引:1,自引:0,他引:1
Legumes grown for grain may or may not contribute net N benefits to soil and succeeding crops. An experiment was conducted to assess N2 fixation attributes of six mungbean cultivars and two groundnut cultivars (Tainan 9 and Non-nod), which determine their residual benefit to the subsequent maize. Nodule number and dry weight of mungbeans peaked early (at 45 days) and declined thereafter strongly. In groundnut nodulation peaked later and declined only by 50% towards the final harvest. The N2-fixing groundnut produced higher total dry matter yield than mungbeans; however, mungbeans produced higher seed yields. Dry matter harvest index and nitrogen harvest index (NHI) were higher in mungbeans (average 0.44 and 0.69) than groundnut (0.23 and 0.47, respectively, in Tainan 9). The percentage of nitrogen derived from air (%Ndfa, 15N isotope dilution) ranged from 54% to 62% in mungbeans, similar to that of groundnut (64%). However, Tainan 9 fixed more N2 (82 kg N ha–1) than mungbeans (35–50 kg N ha–1) and resulted in a positive soil net N balance (+22 kg N ha–1) while negative values were found for Non-nod groundnut and mungbeans (–3 to –12 kg N ha–1). Maize grown after groundnut Tainan 9 had the highest total dry weight and total N uptake. This was equivalent to maize grown in fallow plots, which received 60–90 kg N ha–1, while the respective benefits after mungbeans were 30–60 kg N ha–1. Maize yield was directly related to the amount of residue N returned. Thus, the combination of high N yield, residue quality, %Ndfa and low NHI proved most beneficial to soil fertility and the succeeding crop. 相似文献
2.
The objective of this work was to evaluate the effect of the chemical nature and application frequency of N fertilizers at
different moisture contents on soil N2O emissions and N2O/(N2O+N2) ratio. The research was based on five fertilization treatments: unfertilized control, a single application of 80 kg ha−1 N-urea, five split applications of 16 kg ha−1 N-urea, a single application of 80 kg ha−1 N–KNO3, five split applications of 16 kg ha−1 N–KNO3. Cumulative N2O emissions for 22 days were unaffected by fertilization treatments at 32% water-filled pore space (WFPS). At 100% and 120%
WFPS, cumulative N2O emissions were highest from soil fertilized with KNO3. The split application of N fertilizers decreased N2O emissions compared to a single initial application only when KNO3 was applied to a saturated soil, at 100% WFPS. Emissions of N2O were very low after the application of urea, similar to those found at unfertilized soil. Average N2O/(N2O+N2) ratio values were significantly affected by moisture levels (p = 0.015), being the lowest at 120% WFPS. The N2O/(N2O+N2) ratio averaged 0.2 in unfertilized soil and 0.5 in fertilized soil, although these differences were not statistically significant. 相似文献
3.
The response of faba bean to the application of four rates of gypsum (0, 2.5, 5.0, 10.0 t ha−1) to a non-saline, alkaline sodic soil was measured in terms of grain yield, dry matter (DM) production, N accumulation and
the proportional dependence of the legume on symbiotic N2 fixation (P
atm). A yield-independent, time-integrated 15N-dilution model was used to estimate symbiotic dependence. A significant decrease in the exchangeable sodium percentage and
significant increases in exchangeable Ca++ and the Ca++:Mg++ ratio in the 0–10-cm soil layer were measured 30 months after application of 10 t ha−1 gypsum. Despite low and erratic rainfall during crop growth, faba bean DM and N uptake responded positively to gypsum application.
The symbiotic dependence of the legume at physiological maturity was little affected by sodicity (P
atm = 0.74 at zero gypsum and 0.81–0.82 at 2.5–10 t ha−1 gypsum). The increase in fixed N due to gypsum application was mainly due to increases in legume DM and total N uptake. At
10 t ha−1 of gypsum, faba bean fixed more than 200 kg N ha−1 in above-ground biomass. 相似文献
4.
Kaiwen Pan Zhihong Xu Tim Blumfield Shane Totua Manxin Lu 《Journal of Soils and Sediments》2008,8(6):398-405
Background, aim, and scope Hoop pine (Araucaria cunninghamii) is a nitrogen (N) demanding indigenous Australia softwood species with plantations in Southeast Queensland, Australia. Soil
fertility has declined with increasing rotations and comparison study of N cycling between hoop pine plantations, and adjacent
native forest (NF) is required to develop effective forest management for enhancing sustainable forest production and promoting
environmental benefits. Field in situ mineral 15N transformations in these two forest ecosystems have not been studied. Hence, the present study was to compare the differences
in soil nutrients, N transformations, 15N fluxes, and fate between the hoop pine plantation and the adjacent native forest.
Materials and methods The study sites were in Yarraman State Forest (26°52′ S, 151°51′ E), Southeastern Queensland, Australia. The in situ core
incubation method was used in the field experiments. Mineral N was determined using a LACHAT Quickchem Automated Ion Analyzer.
15N were performed using an isotope ratio mass spectrometer with a Eurovector elemental analyzer. All statistical tests were
carried out by the SPSS 11.0 for Windows statistical software package.
Results Soil total C and N were significantly higher in the NF than in the 53-year-old hoop pine plantation. Concentrations of NO3
– were significantly higher in the NF soil than in the plantation soil. The plantation soil had significantly higher 15N and 13C natural abundances than the NF soil. The NF soil had significantly lower C/N ratios than the plantation soil. NO3
––N was dominated in mineral N pools in both NF and plantation soils, accounting for 91.6% and 70.3% of the total mineral N
pools, respectively. Rates of net nitrification and net N mineralization were, respectively, four and three times higher in
the NF soil than in the plantation soil. The 15NO3
––N and mineral 15N were significantly higher in the NF soil than in the plantation soil. Significant difference in 15NH4
+–N was found in the NF soil before and after the incubation.
Discussion The NF soil had significantly higher NO3
––N, mineral N, total N and C but lower δ15N, δ13C, and C/N ratios than the plantation soil. Moreover, the rates of soil net N mineralization and nitrification were significantly
higher, but ammonification rate was lower in the NF than in the plantation. The NF soil had many more dynamic N transformations
than the plantation soil due to the combination of multiple species and layers and, thus, stimulation of microbial activity
and alteration of C and N pool sizes in favor of the N transformations by soil microbes. The net rate of N and 15N transformation demonstrated differences in N dynamic related to the variation in tree species between the two ecosystems.
Conclusions The change of land use and trees species had significant impacts on soil nutrients and N cycling processes. The plantation
had larger losses of N than the NF. The NO3
––N and 15NO3
––N dominated in the mineral N and 15N pools in both forest ecosystems.
Recommendations and perspectives Native forest soil had strong N dynamic compared with the plantation soil. Composition of multiple tree species with different
ecological niches in the plantation could promote the soil ecosystem sustainability. The 15N isotope dilution technique in the field can be quite useful for studying in situ mineral 15N transformations and fate to further understand actual N dynamics in natural forest soils. 相似文献
5.
Mohammad Mofizur Rahman Jahangir Dries Roobroeck Oswald Van Cleemput Pascal Boeckx 《Biology and Fertility of Soils》2011,47(7):753-766
Nitrous oxide (N2O) emissions, soil microbial community structure, bulk density, total pore volume, total C and N, aggregate mean weight diameter
and stability index were determined in arable soils under three different types of tillage: reduced tillage (RT), no tillage
(NT) and conventional tillage (CT). Thirty intact soil cores, each in a 25 × 25-m2 grid, were collected to a depth of 10 cm at the seedling stage of winter wheat in February 2008 from Maulde (50°3′ N, 3°43′ W),
Belgium. Two additional soil samples adjacent to each soil core were taken to measure the spatial variance in biotic and physicochemical
conditions. The microbial community structure was evaluated by means of phospholipid fatty acids analysis. Soil cores were
amended with 15 kg NO3−-N ha−1, 15 kg NH4+-N ha−1 and 30 kg ha−1 urea-N ha−1 and then brought to 65% water-filled pore space and incubated for 21 days at 15°C, with regular monitoring of N2O emissions. The N2O fluxes showed a log-normal distribution with mean coefficients of variance (CV) of 122%, 78% and 90% in RT, NT and CT, respectively,
indicating a high spatial variation. However, this variability of N2O emissions did not show plot scale spatial dependence. The N2O emissions from RT were higher (p < 0.01) than from CT and NT. Multivariate analysis of soil properties showed that PC1 of principal component analysis had
highest loadings for aggregate mean weight diameter, total C and fungi/bacteria ratio. Stepwise multiple regression based
on soil properties explained 72% (p < 0.01) of the variance of N2O emissions. Spatial distributions of soil properties controlling N2O emissions were different in three different tillages with CV ranked as RT > CT > NT. 相似文献
6.
S. C. Maris J. Lloveras A. Vallejo M. R. Teira-Esmatges 《Water, air, and soil pollution》2018,229(1):11
A high soil nitrogen (N) content in irrigated areas quite often results in environmental problems. Improving the management practices of intensive agriculture can mitigate greenhouse gas (GHG) emissions. This study compared the effect of maize stover incorporation or removal together with different mineral N fertilizer rates (0, 200 and 300 kg N ha?1) on the emission of nitrous oxide (N2O) and carbon dioxide (CO2) on a sprinkler-irrigated maize (Zea mays L.). The trail was conducted in the Ebro Valley (NE Spain) in a high nitrate-N soil (i.e. 200 g NO3–N kg?1). Nitrous oxide and CO2 emissions were sampled weekly using a semi-static closed chamber and quantified using the photoacoustic technique in 2011 and 2012. Applying sidedress N fertilizer tended to increase N2O emissions whereas stover incorporation did not have any clear effect. Nitrification was probably the main process leading to N2O. Denitrification was limited by the low soil moisture content (WFPS <?54%), due to an adequate irrigation management. Emissions ranged from ??0.11 to 0.36% of the N applied, below the IPCC (2007) values. Nitrogen fertilization tended to reduce CO2 emission, but only in 2011. Stover incorporation increased CO2 emission. Nitrogen use efficiency decreased with increasing mineral fertilizer supply. The application of N in high N soils of the Ebro Valley is not necessary until the soil restores a normal mineral N content, regardless of stover management. This will combine productivity with keeping N2O and CO2 emissions under control provided irrigation is adequately managed. Testing soil NO3 ?–N contents before fertilizing would improve N fertilizer recommendations. 相似文献
7.
Nitrate leaching from intensively and extensively grazed grassland measured with suction cup samplers and sampling of soil mineral‐N I Influence of pasture management Leaching of nitrate (NO3—) from two differently managed cattle pastures was determined over four winters between 1993 and 1997 using ceramic suction cup samplers (with min. 34 cups ha—1); additionally, vertical soil mineral‐N content in 0—0.9 m (Nmin) was measured at the beginning and end of two winters (with min. 70 different sample cores ha—1). The experimental site in the highlands north‐east of Cologne, Germany, is characterized by high annual precipitation (av. 1,362 mm between 1993 and 1996). An intensive continuous grazing management (1.3 ha, fertilized with 250 kg N ha—1 yr—1, average stocking density 4.9 LU ha—1, = [I]) was tested against an extensive continuous grazing system (2.2 ha, av. 2.9 LU ha—1; no N‐fertilizer but an estimated proportion of Trifolium repens up to 15 % of total dry matter in the final year, = [E]). The results can be summarized as follows: (1) Mean leaching losses of NO3‐N, estimated from suction cup sampling and balance of drainage volume, were 85 kg NO3‐N ha—1 [I] and 15 kg NO3‐N ha—1 [E] during three wet winters with drainage volumes between 399 and 890 mm; in a dry winter with 105 mm calculated percolation, nitrate leaching decreased by a factor of 5 for both grazing treatments. (2) Although the amount of mineral N in soil (Nmin) sampled in late autumn showed differences between intensive and extensive grazing, the Nmin method permits no certain indication of the risk of NO3 leaching. For example, during the winter period 1994/95 a reduction of mineral N in the soil (0—0.9 m) in both grazing treatments was found (—33 [I] / —8 [E] kg NO3‐N ha—1 and —26 [I] / —21 [E] kg NH4‐N ha—1) whereas during the winter 1996/97 an increase in almost all mean mineral N values occurred (+10 [I] / +2 [E] kg NO3‐N ha—1 and +10 [I] / —10 [E] kg NH4‐N ha—1). (3) In spite of the differences between both methods, the experiment shows that NO3‐N leaching under extensive grazing could be reduced almost to levels close to those under mown grassland. 相似文献
8.
Short-term competition between soil microbes and seedlings of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) for N was assessed in a pot study using (15NH4)2SO4 as a tracer. Seedlings were grown in organic and mineral soil, collected from a podsol soil; 3.18 mg (15NH4)2SO4 per pot were injected into the soil, corresponding to 4 µg 15N g-1 d.m. (dry matter) mineral soil and 17 µg 15N g-1 d.m. organic soil. The amounts of N and 15N in the seedlings and in microbial biomass derived from fumigation-extraction were measured 48 h after addition of 15N. In the mineral soil, 19–30% of the added 15N was found in the plants and 14–20% in the microbial biomass. There were no statistically significant differences between the tree species. In the organic soil, 74% of the added 15N was recovered in the microbial biomass in birch soil, compared to 26% and 17% in pine and spruce soils, respectively. Correspondingly, about 70% of the 15N was recovered in pine and spruce seedlings, and only 23% in birch seedlings. In conclusion, plants generally competed more successfully for added 15NH4 + than soil microbes did. An exception was birch growing in organic soil, where the greater amount of available C from birch root exudates perhaps enabled micro-organisms to utilise more N. 相似文献
9.
Impact of elevated CO<Subscript>2</Subscript>, flooding,and temperature interaction on heterotrophic nitrogen fixation in tropical rice soils 总被引:1,自引:0,他引:1
Response of N2 fixation to elevated CO2 would be modified by changes in temperature and soil moisture because CO2 and temperature or water availability has generally opposing effects on N2 fixation. In this study, we assessed the impacts of elevated CO2 and temperature interactions on nitrogenase activities, readily mineralizable C (RMC), readily available N (NRN) contents
in an alluvial and a laterite rice soil of tropical origin. Soil samples were incubated at ambient (370 μmol mol-1) and elevated (600 μmol mol-1) CO2 concentration at 25oC, 35oC, and 45oC under non-flooded and flooded conditions for 60 days. Elevated CO2 significantly increased nitrogenase activities and readily mineralizable C in both alluvial and laterite soils. All these
activities were further stimulated at higher temperatures. Increases in nitrogenase activity as a result of CO2 enrichment effect over control were 16.2%, 31.2%, and 66.4% and those of NRN content were 2.0%, 1.8%, and 0.5% at 25oC, 35oC
and 45oC, respectively. Increases in RMC contents were 7.7%, 10.0%, and 10.6% at 25°C, 35°C and 45°C, respectively. Soil flooding
resulted in a more clear impact of CO2 enrichment than the non-flooded soil. The results suggest that in tropical rice soils, elevated CO2 increased readily available C content in the soil, which probably stimulates growth of diazotrophic bacteria with enhanced
N2 fixation and thereby higher available N. 相似文献
10.
Effects of biochar addition on N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> emissions from two paddy soils 总被引:2,自引:0,他引:2
Jinyang Wang Man Zhang Zhengqin Xiong Pingli Liu Genxing Pan 《Biology and Fertility of Soils》2011,47(8):887-896
Impacts of biochar addition on nitrous oxide (N2O) and carbon dioxide (CO2) emissions from paddy soils are not well documented. Here, we have hypothesized that N2O emissions from paddy soils could be depressed by biochar incorporation during the upland crop season without any effect
on CO2 emissions. Therefore, we have carried out the 60-day aerobic incubation experiment to investigate the influences of rice
husk biochar incorporation (50 t ha−1) into two typical paddy soils with or without nitrogen (N) fertilizer on N2O and CO2 evolution from soil. Biochar addition significantly decreased N2O emissions during the 60-day period by 73.1% as an average value while the inhibition ranged from 51.4% to 93.5% (P < 0.05–0.01) in terms of cumulative emissions. Significant interactions were observed between biochar, N fertilizer, and
soil type indicating that the effect of biochar addition on N2O emissions was influenced by soil type. Moreover, biochar addition did not increase CO2 emissions from both paddy soils (P > 0.05) in terms of cumulative emissions. Therefore, biochar can be added to paddy fields during the upland crop growing
season to mitigate N2O evolution and thus global warming. 相似文献
11.
A laboratory incubation experiment was conducted to demonstrate that reduced availability of CO2 may be an important factor limiting nitrification. Soil samples amended with wheat straw (0%, 0.1% and 0.2%) and (15NH4)2SO4 (200 mg N kg–1 soil, 2.213 atom% 15N excess) were incubated at 30±2°C for 20 days with or without the arrangement for trapping CO2 resulting from the decomposition of organic matter. Nitrification (as determined by the disappearance of NH4+ and accumulation of NO3–) was found to be highly sensitive to available CO2 decreasing significantly when CO2 was trapped in alkali solution and increasing substantially when the amount of CO2 in the soil atmosphere increased due to the decomposition of added wheat straw. The co-efficient of correlation between NH4+-N and NO3–-N content of soil was highly significant (r =0.99). During incubation, 0.1–78% of the applied NH4+ was recovered as NO3– at different incubation intervals. Amendment of soil with wheat straw significantly increased NH4+ immobilization. From 1.6% to 4.5% of the applied N was unaccounted for and was due to N losses. The results of the study suggest that decreased availability of CO2 will limit the process of nitrification during soil incubations involving trapping of CO2 (in closed vessels) or its removal from the stream of air passing over the incubated soil (in open-ended systems). 相似文献
12.
The potential for N2O emission and nitrate leaching in seasonally open solar greenhouses during the summer fallow: a 15N tracer study
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The mechanisms responsible for nitrous oxide (N2O) emission and the potential for nitrate leaching under seasonally open solar greenhouses were investigated in a nitrogen‐15 (15N) tracer study during the summer fallow period in Yangling, Shaanxi Province, China. 15N‐labelled urea and KNO3 were applied at 30 (U1, K1) and 60 (U2, K2) kg N/ha, respectively, to microplots in a solar greenhouse after harvest of tomatoes. Large N2O emissions resulted from each treatment, with a total N2O flux of 482, 1481, 2283, 656 and 991 g N/ha for control (CK), U1, U2, K1 and K2, respectively, were primarily observed during the first month of the summer fallow period, reflecting the combination of considerable residual nitrate, soil organic matter and rainfall. The total 15N‐N2O flux was 35.2, 37.2, 7.9 and 11.2 g N/ha for U1, U2, K1 and K2, respectively, accounting for 0.54, 0.40, 0.17 and 0.12% of the applied N, suggesting that both nitrification and denitrification contributed to the enhanced N2O emission. After 2 months of fallow, only 52.08–54.78% of applied 15N remained in the top 0–40 cm soil layer, where there was the main concentration of tomato roots. Of the total 15N‐labelled KNO3 applied, 86.76% (K1) and 82.06% (K2) remained in the 0–100 cm soil layers and the rest of the N (about 13.07% for K1 and 17.82% for K2, calculated by subtracting 15N‐N2O loss and 15N remaining in the 0–100 cm soil layers from the total applied 15N) leached below 100 cm. Solar greenhouses in north‐west China clearly have great potential for both N2O emission and nitrate leaching during the summer fallow period. 相似文献
13.
Roberta Gentile Mike Dodd Mark Lieffering Shona C. Brock Phil W. Theobald Paul C. D. Newton 《Biology and Fertility of Soils》2012,48(3):357-362
Altered soil nutrient cycling under future climate scenarios may affect pasture production and fertilizer management. We conducted
a controlled-environment study to test the hypothesis that long-term exposure of pasture to enriched carbon dioxide (CO2) would lower soil nutrient availability. Perennial ryegrass was grown for 9 weeks under ambient and enriched (ambient + 120 ppm)
CO2 concentrations in soil collected from an 11.5-year free air CO2 enrichment experiment in a grazed pasture in New Zealand. Nitrogen (N) and phosphorus (P) fertilizers were applied in a full
factorial design at rates of 0, 12.5, 25 or 50 kg N ha−1 and 0, 17.5 or 35 kg P ha−1. Compared to ambient CO2, under enriched CO2 without P fertilizer, total plant biomass did not respond to N fertilizer, and tissue N/P ratio was increased indicating
that P was co-limiting. This limitation was alleviated with the lowest rate of P fertilizer (17.5 kg P ha−1). Plant biomass in both CO2 treatments increased with increasing N fertilizer when sufficient P was available. Greater inputs of P fertilizer may be
required to prevent yield suppression under enriched CO2 and to stimulate any response to N. 相似文献
14.
The only known sink for nitrous oxide (N2O) is biochemical reduction to dinitrogen (N2) by N2O reductase (N2OR). We hypothesized that the application of N2O-reducing denitrifier-inoculated organic fertilizer could enhance soil N2O consumption while the disruption of nosZ genes could result in inactivation of N2O consumption. To test such hypotheses, a denitrifier-inoculated granular organic fertilizer was applied to both soil microcosms and fields. Of 41 denitrifier strains, 38 generated 30N2 in the end products of denitrification (30N2 and 46N2O) after the addition of Na15NO3 in culture condition, indicating their high N2O reductase activities. Of these 41 strains, 18 were screened in soil microcosms after their inoculation into the organic fertilizer, most of which were affiliated with Azospirillum and Herbaspirillum. These 18 strains were nutritionally starved to improve their survival in soil, and 14 starved and/or non-starved strains significantly decreased N2O emissions in soil microcosms. However, the N2O emission had not been decreased in soil microcosms after inoculating with a nosZ gene-disruptive strain, suggesting that N2O reductase activity might be essential for N2O consumption. Although the decrease of N2O was not significant at field scales, the application of organic fertilizer inoculated with Azospirillum sp. TSH100 and Herbaspirillum sp. UKPF54 had decreased the N2O emissions by 36.7% in Fluvisol and 23.4% in Andosol in 2014, but by 21.6% in Andosol in 2015 (H. sp. UKPF54 only). These results suggest that the application of N2O-reducing denitrifier-inoculated organic fertilizer may enhance N2O consumption or decrease N2O emissions in agricultural soils. 相似文献
15.
Effects of biochar,urea and their co‐application on nitrogen mineralization in soil and growth of Chinese cabbage
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Experiments were conducted to study the effect of soil applications of kunai grass (Imperata cylindrica) biochar (0 and 10 t/ha) and laboratory grade urea (0, 200 and 500 kg N/ha) and their co‐application on nitrogen (N) mineralization in an acid soil. The results of an incubation study showed that the biochar only treatment and co‐application with urea at 200 kg N/ha could impede transformation of urea to ammonium‐N (NH4+‐N). Soil application of biochar together with urea at 500 kg N/ha produced the highest nitrate‐N (NO3?‐N) and mineral N concentrations in the soil over 90 days. Co‐application of urea N with biochar improved soil N mineralization parameters such as mineralization potential (NA) and coefficient of mineralization rate (k) compared to biochar alone. In a parallel study performed under greenhouse conditions, Chinese cabbage (Brassica rapa L. ssp. chinensis L.) showed significantly greater (P < 0.05) marketable fresh weight, dry matter production and N uptake in soil receiving urea N at 500 kg/ha or co‐application of biochar with urea N compared to the control. Application of biochar only or urea only at 200 kg N/ha did not offer any short‐term agronomic advantages. The N use efficiency of the crop remained unaffected by the fertilizer regimes. Applications of biochar only at 10 t/ha did not offer benefits in this tropical acid soil unless co‐applied with sufficient urea N. 相似文献
16.
Daan Beheydt Pascal Boeckx Hasan Pervej Ahmed Oswald Van Cleemput 《Biology and Fertility of Soils》2008,44(6):863-873
In this study, we investigated N2O emissions from two fields under minimum tillage, cropped with maize (MT maize) and summer oats (MT oats), and a conventionally
tilled field cropped with maize (CT maize). Nitrous oxide losses from the MT maize and MT oats fields (5.27 and 3.64 kg N2O-N ha−1, respectively) were significantly higher than those from the CT maize field (0.27 kg N2O-N ha−1) over a period of 1 year. The lower moisture content in CT maize (43% water-filled pore space [WFPS] compared to 60–65%)
probably caused the difference in total N2O emissions. Denitrification was found to be the major source of N2O loss. Emission factors calculated from the MT field data were high (0.04) compared to the CT field (0.001). All data were
simulated with the denitrification decomposition model (DNDC). For the CT field, N2O and N2O + N2 emissions were largely overestimated. For the MT fields, there was a better agreement with the total N2O and N2O + N2 emissions, although the N2O emissions from the MT maize field were underestimated. The simulated N2O emissions were particularly influenced by fertilization, but several other measured N2O emission peaks associated with other management practices at higher WFPS were not captured by the model. Several mismatches
between simulated and measured
\textNH4+ {\text{NH}}_4^ + ,
\textNO3- {\text{NO}}_3^ - and WFPS for all fields were observed. These mismatches together with the insensitivity of the DNDC model for increased N2O emissions at the management practices different from fertilizer application explain the limited similarity between the simulated
and measured N2O emissions pattern from the MT fields. 相似文献
17.
Nodulating and non‐nodulating soybeans were grown on a Alfic Udipsamment and a Typic Hapludoll amended with 10 or 100 kg N/ha. Tissue and grain samples were analyzed to determine N2‐fixation, dry matter, and N, P, and K accumulation. Highest grain yields were associated with the highest levels of N2‐fixation and N and K accumulation in grain. The largest dry matter production was by nodulating plants grown on a high soil N regime. Nodulating plants accumulated more grain and tissue N, P, and K than non‐nodulating plants. Nitrogen stress increased P concentrations in both grain and tissue and decreased harvest indices. 相似文献
18.
The 15N isotopic dilution technique was used to assess N2 fixation in desi chickpea (Cicer arientinum L.) cv. Myles at different growth stages as influenced by inoculation method. In this growth chamber study, no significant differences in nodule dry weight, amount of N2 fixed and plant dry matter were observed between seed inoculation with seed-applied peat inoculant and soil-applied granular inoculant placed 2.5 cm below the seed. However, seed inoculation with liquid inoculant was inferior to the seed-applied peat or the granular inoculant for all parameters measured at all sampling dates. The seed-applied peat and granular inoculant treatments fixed 4.8 and 4.1 mg N plant-1, respectively, by the late vegetative stage, and reached a maximum of 20.6 and 25.6 mg N plant-1, respectively, by the late pod-filling stage. These values accounted for 30.5% and 34.9% of the total plant N for the peat and granular inoculant, respectively, by late pod-filling. For the liquid inoculant treatment, the amount of N2 fixed increased from 2.3 mg N plant-1 by the late vegetative stage to a maximum of 9.6 mg N plant-1 which was 22.2% of total plant N by the mid pod-filling stage. The highest daily N2 fixation rate for the peat and granular inoculant was 0.9 mg N plant-1 and occurred between flowering and early pod-filling, whereas that for the liquid occurred between early and mid pod-filling stages (0.23 mg N plant-1). After the mid pod-filling stage, little or no N2 was fixed in all treatments. Plant dry matter increased from the late vegetative stage to physiological maturity but the greatest dry matter accumulation occurred between the late vegetative and early pod-filling stages in all treatments. 相似文献
19.
At cattle overwintering areas, inputs of nutrients in animal excrements create conditions favourable for intensive microbial
activity in soil. During nitrogen transformations, significant amounts of N2O are released, which makes overwintering areas important sources of N2O emission. In previous studies, however, increasing intensity of long-term cattle impact did not always increase emissions
of N2O from the soil: in some cases, N2O emissions from the soil were lower at the most impacted area than at the moderately impacted one. Thus, the relationships
between the level of long-term animal impact and potential production of N2O from soil by denitrification were investigated in field and laboratory experiments. Field measurements indicated that the
production of N2O after glucose and nitrate amendments was greater in severely and moderately impacted locations than in an unimpacted location,
while differences between the severely and moderately impacted locations were not significant. In laboratory experiments,
the potential production of N2O (measured as anaerobic production of N2O after addition of glucose and nitrate) was highest in the moderately impacted soil. Surprisingly, potential N2O production was lower in the most impacted than in the moderately impacted soil, and the net N2O production in the highly impacted soil was further decreased by a significant reduction of N2O to N2. The expected stimulating effect of an increasing ratio of glucose C to nitrate N on the reduction of N2O to N2 during denitrification was not confirmed. The results show that cattle increase the denitrification potential of the soil
but suggest that the denitrification potential does not increase indefinitely with increasing cattle impact. 相似文献
20.
Background : Rice production in low‐input systems of West Africa relies largely on nitrogen supply from the soil. Especially in the dry savanna agro‐ecological zone, soil organic N is mineralized during the transition period between the dry and the wet seasons. In addition, in the inland valley landscape, soil N that is mineralized on slopes may be translocated as nitrate into the lowlands. There, both in‐situ mineralized as well as the laterally translocated nitrate‐N will be exposed to anaerobic conditions and is thus prone to losses. Aim : We determined the dynamics of soil NO3‐N along a valley toposequence during the dry‐to‐wet season transition period and the effects of soil N‐conserving production strategies on the grain yield of rainfed lowland rice grown during the subsequent wet season. Methods : Field experiments in Dano (Burkina Faso) assessed during two consecutive years the temporal dynamics and spatial fluxes of soil nitrate along a toposequence. We applied sequential and depth‐stratified soil nitrate analysis and nitrate absorption in ion exchange resin capsules in lowlands that were open to subsurface interflow and in those where the interflow from the was intercepted. During one year only we also assessed the effect of pre‐rice vegetation on conserving this NO3‐N as well as on N addition by biological N2 fixation in legumes using δ15N isotope dilution. Finally, we determined the impact of soil N fluxes and their differential management during the transition season on growth, yield and N use of rainfed lowland rice. Results : Following the first rainfall event of the season, soil NO3‐N initially accumulated and subsequently decreased gradually in the soil of the valley slope. Much of this nitrate N was translocated by lateral sub‐surface flow into the valley bottom wetland. There, pre‐rice vegetation was able to absorb much of the in‐situ mineralized and the laterally‐translocated soil NO3‐N, reducing its accumulation in the soil from 40–43 kg N ha?1 under a bare fallow to 1–23 kg N ha?1 in soils covered by vegetation. Nitrogen accumulation in the biomass of the transition season crops ranged from 44 to 79 kg N ha?1 with a 36–39% contribution from biological N2 fixation in the case of legumes. Rice agronomic performance improved following the incorporation as green manure of this “nitrate catching” vegetation, with yields increasing up to 3.5 t ha?1 with N2‐fixing transition seasons crops. Conclusion : Thus, integrating transition season legumes during the pre‐rice cropping niche in the prevailing low‐input systems in inland valleys of the dry savanna zone of West Africa can temporarily conserve substantial amounts of soil NO3‐N. It can also add biologically‐fixed N, thus contributing to increase rice yields in the short‐term and, in the long‐term, possibly maintaining or improving soil fertility in the lowland. 相似文献