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1.
A soil lysimeter field study assessed the efficacy of different pasture species to reduce nitrogen (N) leaching loss from cow urine deposited in different seasons. A single application of cow urine ( 15N‐labelled; equivalent to 622 kg N ha ?1) was applied in three different seasons (summer, autumn or winter) to three pasture species monocultures (perennial ryegrass, plantain or lucerne) on a free‐draining volcanic soil and monitored over 362 days. Leachate analyses revealed consistently large leaching losses of inorganic‐N from lucerne (>200 kg N ha ?1) across different urine application times due to the relatively low plant growth rates during winter (<15 kg DM ha ?1 day ?1) that led to low total recovery of urine‐N by lucerne plants (<20% of the applied urine‐ 15N). Conversely, plant uptake of the urine‐N was higher by plantain (ranging from 30% to 45% of that applied) driven by moderately higher winter plant growth rates (30 to 60 kg DM ha ?1 day ?1). Plantain exhibited large seasonal variation in its efficacy to reduce urine‐N leaching relative to ryegrass (ranging from 15% to 50% reduction for summer or winter urine applications, respectively) with an overall reduction of 39% in the total amount of inorganic‐N leached across the three seasons (53 vs. 87 kg N ha ?1 leached relative to ryegrass). This study has demonstrated the potential benefit of using plantain to reduce N leaching losses from urine deposited in the summer to winter grazing period. However, further research is required to quantify the effects of plantain on annual N leaching losses from grazed pastoral systems. 相似文献
2.
PurposeGrazing livestock has strong impact on global nitrous oxide (N2O) emissions by providing N sources through excreta. The scarcity of information on factors influencing N2O emissions from sheep excreta in subtropical ecosystems such as those of Southern Brazil led us to conduct field trials in three different winter pasture seasons on an integrated crop–livestock system (ICL) in order to assess N2O emission factors (EF-N2O) in response to variable rates of urine and dung. Materials and methodsThe equivalent urine-N loading rates for the three winter seasons (2009, 2010, and 2013) ranged from 96 to 478 kg ha?1, and the dung-N rates applied in 2009 and 2010 were 81 and 76 kg ha?1, respectively. Air was sampled from closed static chambers (0.20 m in diameter) for approximately 40 days after excreta application and analyzed for N2O by gas chromatography. Results and discussionSoil N2O-N fluxes spanned the ranges 4 to 353 μg m?2 h?1 in 2009, ??47 to 976 μg m?2 h?1 in 2010, and 46 to 339 μg m?2 h?1 in 2013. Urine addition resulted in N2O-N peaks within for up to 20–30 days after application in the 3 years, and the strength of the peaks was linearly related to the N rate used. Emission factors of N2O (EF-N2O, % of N applied that is emitted as N2O) of urine ranged from 0.06 to 0.34% and were essentially independent of N rate applied. By considering a ratio of N excreted by urine and dung of 60:40, a single combined excretal EF-N2O of 0.14% was estimated. ConclusionsOur findings showed higher mean EF-N2O for sheep urine than that for dung (0.21% vs 0.03%), irrespective of the occurrence or not of urine patches overlap. This value is much lower than default value of 1% of IPCC’s Tier 1 and reinforces the needs of its revision. 相似文献
3.
Denitrification rates are often greater in no-till than in tilled soils and net soil-surface greenhouse gas emissions could be increased by enhanced soil N 2O emissions following adoption of no-till. The objective of this study was to summarize published experimental results to assess whether the response of soil N 2O fluxes to the adoption of no-till is influenced by soil aeration. A total of 25 field studies presenting direct comparisons between conventional tillage and no-till (approximately 45 site-years of data) were reviewed and grouped according to soil aeration status estimated using drainage class and precipitation during the growing season. The summary showed that no-till generally increased N 2O emissions in poorly-aerated soils but was neutral in soils with good and medium aeration. On average, soil N 2O emissions under no-till were 0.06 kg N ha −1 lower, 0.12 kg N ha −1 higher and 2.00 kg N ha −1 higher than under tilled soils with good, medium and poor aeration, respectively. Our results therefore suggest that the impact of no-till on N 2O emissions is small in well-aerated soils but most often positive in soils where aeration is reduced by conditions or properties restricting drainage. Considering typical soil C gains following adoption of no-till, we conclude that increased N 2O losses may result in a negative greenhouse gas balance for many poorly-drained fine-textured agricultural soils under no-till located in regions with a humid climate. 相似文献
4.
PurposeGlomalin-related soil protein (GRSP) is an essential component of soil organic C for maintaining soil quality and structure and plays a critical role in soil carbon (C) sequestration. However, how GRSP changes under nitrogen (N) deposition remains poorly understood. Materials and methodsWe assessed total GRSP (T-GRSP) and easily extractable GRSP (EE-GRSP) under a control (no N input), low N addition (LN, 40 kg N ha?1 year?1), and high N addition (HN, 80 kg N ha?1 year?1) treatments in 2015 and 2016 in a Chinese fir (Cunninghamia lanceolata) plantation in the subtropical China. We also analyzed soil properties contents and explored the stoichiometric ratios of soil organic C (SOC), total N (TN), and total phosphorus (TP) with GRSPs. ResultsCompared to the control, both T-GRSP and EE-GRSP were significantly reduced under the HN treatment, but had no significant difference under the LN treatment. The ratio of T-GRSP and EE-GRSP was reduced by the N addition. Soil organic C (SOC) and dissolved organic C (DOC) were significantly affected by N addition treatments. The ratios of GRSP-C to SOC and of EEGRSP-C to SOC ranged from 6.29 to 16.07% and 1.34 to 3.52%, respectively. T-GRSP and EE-GRSP were positively correlated with SOC/TN ratio, but negatively correlated with soil TN/TP and SOC/TP ratios. ConclusionOur results indicated that the GRSP reductions under N deposition in soil are mediated by soil C, N, and P stoichiometry, and particularly, the reduction of EE-GRSP by DOC. This study improved our mechanistic understanding of dynamics of GRSPs under increasing N enrichment in subtropical plantation ecosystems. 相似文献
5.
An increasing area of oilseed rape cultivation in Europe is used to produce biodiesel. However, a large amount of straw residue is often left in the field in autumn. Straw mineralization provides both carbon (C) and nitrogen (N) sources for emission of soil nitrous oxide (N 2O), which is an important greenhouse gas with a high warming potential. Some studies have focused on soil N 2O emissions immediately post-harvest; however, straw mineralization could possibly last over winter. Most field studies in winter have focused on freeze-thaw cycles. It is still not clear how straw mineralization affects soil N 2O emissions in unfrozen wintertime conditions. We carried out a field experiment in northern Germany in winter 2014, adding straw and glucose as a source of C with three rates of N fertilizer (0, 30, and 60 kg N ha −1). During the 26 days of observation, cumulative N 2O emission in treatments without C addition was negative at all N fertilizer levels. Straw addition produced –3.2, 11.2, and 5.0 mg N 2O-N m −2 at 0, 30, and 60 kg N ha −1, respectively. Addition of glucose surprisingly caused –1.5, 74.6, and 165 mg N 2O–N m −2 at 0, 30, and 60 kg N ha −1, respectively. This study demonstrates that oilseed rape straw does not cause high N 2O emissions in wintertime when no extreme precipitation or freeze-thaw cycles are involved, and soil organic C content is low. However, N 2O emission could be intensively stimulated, when both easily available organic C and nitrate are not limited and the soil temperature between 0 and 10°C. These results provide useful information on potential changes to N 2O emissions that may occur due to the increased use of oilseed rape for biodiesel combined with less severe winters in the northern hemisphere driven by global warming. 相似文献
6.
Nitrous oxide (N 2O) is a greenhouse gas and agricultural soils are major sources of atmospheric N 2O. Its emissions from soils make up the largest part in the global N 2O budget. Research was carried out at the experimental fields of the Leibniz-Institute of Agricultural Engineering Potsdam-Bornim (ATB). Different types (mineral and wood ash) and levels (0, 75 and 150 kg N ha −1) of fertilization were applied to annual (rape, rye, triticale and hemp) and perennial (poplar and willow) plants every year. N 2O flux measurements were performed 4 times a week by means of gas flux chambers and an automated gas chromatograph between 2003 and 2005. Soil samples were also taken close to the corresponding measuring rings. Soil nitrate and ammonium were measured in soil extracts.N 2O emissions had a peak after N fertilization in spring, after plant harvest in summer and during the freezing–thawing periods in winter. Both fertilization and plant types significantly altered N 2O emission. The maximum N 2O emission rate detected was 1081 μg N 2O m −2 h −1 in 2004. The mean annual N 2O emissions from the annual plants were more than twofold greater than those of perennial plants (4.3 kg ha −1 vs. 1.9 kg ha −1). During January, N 2O fluxes considerably increased in all treatments due to freezing–thawing cycles. Fertilization together with annual cropping doubled the N 2O emissions compared to perennial crops indicating that N use efficiency was greater for perennial plants. Fertilizer-derived N 2O fluxes constituted about 32% (willow) to 67% (rape/rye) of total soil N 2O flux. Concurrent measurements of soil water content, NO 3 and NH 4 support the conclusion that nitrification is main source of N 2O loss from the study soils. The mean soil NO 3-N values of soils during the study for fertilized soils were 1.6 and 0.9 mg NO 3-N kg −1 for 150 and 75 kg N ha −1 fertilization, respectively. This value reduced to 0.5 mg NO 3-N kg −1 for non-fertilized soils. 相似文献
7.
Nitrogen (N) losses via nitrate (NO 3−) leaching, ammonia (NH 3) volatilization and nitrous oxide (N 2O) emissions from grazed pastures in New Zealand are one of the major contributors to environmental degradation. The use of N inhibitors (urease and nitrification inhibitors) may have a role in mitigating these N losses. A one-year field experiment was conducted on a permanent dairy-grazed pasture site at Massey University, Palmerston North, New Zealand to quantify these N losses and to assess the effect of N inhibitors in reducing such losses during May 2005-2006. Cow urine at 600 kg N ha −1 rate with or without urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) or (trade name “Agrotain”) (3 L ha −1), nitrification inhibitor dicyandiamide (DCD) (7 kg ha −1) and the use of double inhibitor (DI) containing a combination of both Agrotain and DCD (3:7) were applied to field plots in autumn, spring and summer. Pasture production, NH 3 and N 2O fluxes, soil mineral N concentrations, microbial biomass C and N, and soil pH were measured following the application of treatments during each season. All measured parameters, except soil microbial biomass C and N, were influenced by the added inhibitors during the three seasons. Agrotain reduced NH 3 emissions over urine alone by 29%, 93% and 31% in autumn, spring and summer respectively but had little effect on N 2O emission. DCD reduced N 2O emission over urine alone by 52%, 39% and 16% in autumn, spring and summer respectively but increased NH 3 emission by 56%, 9% and 17% over urine alone during those three seasons. The double inhibitor reduced NH 3 by 14%, 78% and 9% and N 2O emissions by 37%, 67% and 28% over urine alone in autumn, spring and summer respectively. The double inhibitor also increased pasture dry matter by 10%, 11% and 8% and N uptake by the 17%, 28% and 10% over urine alone during autumn, spring and summer respectively. Changes in soil mineral N and pH suggested a delay in urine-N hydrolysis with Agrotain, and reduced nitrification with DCD. The combination of Agrotain and DCD was more effective in reducing both NH 3 and N 2O emissions, improving pasture production, controlling urea hydrolysis and retaining N in NH 4+ form. These results suggest that the combination of both urease and nitrification inhibitors may have the most potential to reduce N losses if losses are associated with urine and improve pasture production in intensively grazed systems. 相似文献
8.
PurposeAccelerated erosion removes fertile top soil along with nutrients through runoff and sediments, eventually affecting crop productivity and land degradation. However, scanty information is available on soil and nutrient losses under different crop covers in a vertisol of Central India. Thus, a field experiment was conducted for 4 years (2010–2013) to study the effect of different crop cover combinations on soil and nutrient losses through runoff in a vertisol. Materials and methodsVery limited information is available on runoff, soil, and nutrient losses under different vegetative covers in a rainfed vertisol. Thus, the hypothesis of the study was to evaluate if different crop cover combinations would have greater impact on reducing soil and nutrient losses compared to control plots in a vertisol. This experiment consisted of seven treatment combinations of crop covers namely soybean (Glycine max) (CC1), maize (Zea mays) (CC2), pigeon pea (Cajanus cajan) (CC3), soybean (Glycine max)?+?maize (Zea mays) ??1:1 (CC4), soybean (Glycine ma x))?+?pigeon pea (Cajanus cajan) ?2:1 (CC5), maize (Zea mays)?+?pigeon pea (Cajanus cajan) ??1:1 (CC6), and cultivated fallow (CC7). The plot size was 10?×?5 m with 1% slope, and runoff and soil loss were measured using multi-slot devisor. All treatments were arranged in a randomized block design with three replications. Results and discussionResults demonstrated that the runoff and soil loss were significantly (p?<?0.05) higher (289 mm and 3.92 Mg ha?1) under cultivated fallow than those in cropped plots. Among various crop covers, sole pigeon pea (CC3) recorded significantly higher runoff and soil loss (257 mm and 3.16 Mg ha?1) followed by that under sole maize (CC2) (235 mm and 2.85 Mg ha?1) and the intercrops were in the order of maize?+?pigeon pea (211 mm and 2.47 Mg ha?1) followed by soybean?+?maize (202 mm and 2.38 Mg ha?1), and soybean?+?pigeon pea (195 mm and 2.15 Mg ha?1). The lowest runoff and soil loss were recorded under soybean sole crop (194 mm and 2.27 Mg ha?1). The data on nutrient losses indicated that the highest losses of soil organic carbon (SOC) (25.83 kg ha?1), total nitrogen (N), phosphorus (P), and potassium (K) (7.76, 0.96, 32.5 kg ha?1) were recorded in cultivated fallow (CC7) as compared to those from sole and intercrop treatments. However, sole soybean and its intercrops recorded the minimum losses of SOC and total N, P, and K, whereas the maximum losses of nutrients were recorded under pigeon pea (CC3). The system productivity in terms of soybean grain equivalent yield (SGEY) was higher (p?<?0.05) from maize?+?pigeon pea (3358 kg ha?1) followed by that for soybean?+?pigeon pea (2191 kg ha?1) as compared to sole soybean. Therefore, maize?+?pigeon pea (1:1) intercropping is the promising option in reducing runoff, soil-nutrient losses, and enhancing crop productivity in the hot sub-humid eco-region. ConclusionsStudy results highlight the need for maintenance of suitable vegetative cover as of great significance to diffusing the erosive energy of heavy rains and also safe guarding the soil resource from degradation by water erosion in vertisols. 相似文献
9.
PurposeArid steppes in northern China have degraded severely in recent decades due to frequent human activities, resulting in poor soil quality and thus low productivity. The objective of the current study was to investigate whether nitrogen addition was a useful approach to improve productivity of these degraded steppes in Inner Mongolia. Materials and methodsIn the current study, severely degraded arid steppe was fenced in June 2014 and then fertilized for consecutive 3 years, 2014, 2015, and 2016. There were four nitrogen fertilization rates, 0, 50, 100, and 150 kg N ha?1, and two phosphorus rates, 0 and 60 kg P2O5 ha?1. Each treatment replicated three times, with each plot size reaching 400 m2 (20 m?×?20 m). The annual precipitation in 2014 and 2016 were 255 and 309 mm (dry years), respectively, lower than that (412 mm) in 2015 (wet year). Results and discussionThe results indicated that aboveground biomass in wet years was significantly higher than that in dry years, suggesting that water is the most important limiting factor influencing steppe productivity. Plant nitrogen concentration in Stipa krylovii (dominant species) was positively correlated with the concentrations of soil available nitrogen and nitrogen use efficiency (NUE), confirming that the plant adsorbed more nitrogen under fertilization and thus increasing the NUE. The NUE and water use efficiency (WUE) in wet year were higher than those in dry years and a positive correlation was also observed between WUE and NUE, confirming that the NUE was relied mainly on precipitation. ConclusionsNitrogen fertilization was effective in increasing grassland production in wet years but not in dry years, suggesting that the primary limitation on grassland productivity in this ecosystem might shift from precipitation in dry years to nitrogen in wet years. Higher NUE could be obtained under low nitrogen rates in wet years. Therefore, in degraded arid steppe, low nitrogen rate (50 kg N ha?1) was recommended in wet years to improve steppe productivity. 相似文献
10.
PurposeRecent research suggests that Swedish organic arable soils have been under-recognized as a potential source of phosphorus (P) loading to water bodies. The aim of this study was to compare P losses through leaching from organic and high-fertility mineral soils. In addition, the effectiveness of a magnesium-salt-coated biochar applied below the topsoil as a mitigation strategy for reducing P losses was evaluated. Materials and methodsPhosphorus leaching was measured from four medium- to high-P arable soils, two Typic Haplosaprists (organic 1 and 2), a Typic Hapludalf (sand), and an unclassified loam textured soil (loam), in a 17-month field study utilizing 90-cm-long lysimeters. A magnesium-salt-coated biochar was produced and characterized using X-ray powder diffraction (XPD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and X-ray adsorption (XANES) spectroscopy, and its phosphate adsorption capacity was determined at laboratory scale. It was also applied as a 3-cm layer, 27 cm below the soil surface of the same lysimeters and examined as a mitigation measure to reduce P leaching. Results and discussionTotal-P loads from the 17-month, unamended lysimeters were in the order of organic 2 (1.2 kg ha?1)?>?organic 1 (1.0 kg ha?1)?>?sand (0.3 kg ha?1)?>?loam (0.2 kg ha?1). Macropore flow, humic matter competition for sorption sites, and fewer sorption sites likely caused higher P losses from the organic soils. Analysis by XRD and SEM revealed magnesium was primarily deposited as periclase (MgO) on the biochar surface but hydrated to brucite (Mg(OH)2) in water. The Langmuir maximum adsorption capacity (Qmax) of the coated biochar was 65.4 mg P g?1. Lysimeters produced mixed results, with a 74% (P?<?0.05), 51% (NS), and 30% (NS) reduction in phosphate-P from the organic 1, organic 2, and sand, respectively, while P leaching increased by 230% (NS) from the loam. ConclusionsThe findings of this study indicate that P leached from organic arable soils can be greater than from mineral soils, and therefore, these organic soils require further investigation into reducing their P losses. Metal-enriched biochar, applied as an adsorptive layer below the topsoil, has the potential to reduce P losses from medium- to high-P organic soils but appear to be less useful in mineral soils. 相似文献
11.
PurposeSoil chromium (Cr) pollution has received substantial attention owing to related food chain health risks and possible promotion of greenhouse gas (GHG) emissions. The aim of the present study was to develop a promising remediation technology to alleviate Cr bioavailability and decrease GHG emissions in Cr-polluted paddy soil. Materials and methodsWe investigated the potential role of biochar amendment in decreasing soil CO2, CH4, and N2O emissions, as well in reducing Cr uptake by rice grains at application rates of 0 t ha?1 (CK), 20 t ha?1 (BC20), and 40 t ha?1 (BC40) in Cr-polluted paddy soil in southeastern China. In addition, the soil aggregate size distribution, soil organic carbon (SOC) concentration of soil aggregates, soil available Cr concentration, and rice yield were analyzed after harvesting. Results and discussionBiochar amendment significantly reduced CO2, CH4, and N2O emission fluxes. Compared to CK, total C emissions in the BC20 and BC40 treatments decreased by 9.94% and 17.13% for CO2-C, by 30.46% and 37.10% for CH4-C, and by 34.24% and 37.49% for N2O-N, respectively. Biochar amendment increased the proportion of both the 2000–200 μm and 200–20 μm size fractions in the soil aggregate distribution. Accordingly, the organic carbon concentration of these fractions increased, which increased the total SOC. Moreover, biochar amendment significantly decreased soil available Cr concentration and total Cr content of the rice grains by 33.6% and 14.81% in BC20 and 48.1% and 33.33% in BC40, respectively. Rice yield did not differ significantly between biochar amendment treatment and that of CK. ConclusionsBiochar application reduced GHG emissions in paddy soil, which was attributed to its comprehensive effect on the soil properties, soil microbial community, and soil aggregates, as well as on the mobility of Cr. Overall, the present study demonstrates that biochar has a great potential to enhance soil carbon sequestration while reducing Cr accumulation in rice grains from Cr-polluted rice paddies. 相似文献
12.
Among energy crops, short‐rotation coppices (SRC) are recommended to provide renewable energy. Compared to annual crops, willows and poplars are regarded as plants with low requirements for nutrients, herbicides, pesticides, and soil maintenance. However, only little is known about N‐fertilizer effects on SRC and the few studies are even inconsistent. Therefore, we studied the effects of N on yields of willows and poplars in a field experiment. The effects of N fertilization on nitrate leaching and nitrous oxide emissions from the loamy‐sand soil were also measured. Cuttings of willows ( Salix viminalis clone Inger) and poplars ( Populus maximovizcii × P. nigra clone max 4) were planted on farmland in 2008. The experiment was arranged in a random block design with three levels of N fertilizer (0, 50, and 75 kg N ha –1 y –1). After 2 y, the trees were harvested for the first time. Fertilization did not affect the yields of willows or poplars. However, the application of 75 kg N ha –1 y –1 caused an average increase of N leaching in the willow and poplar plots of 25 kg N ha –1 y –1 and 40 kg N ha –1 y –1, respectively. Emissions of N 2O were increased by a maximum of only 0.2 kg N ha –1 y –1. Further, the N fertilizer stimulated the growth of the weed biomass in case of the willow plots by 46% and of the weed N content by 52% ( r = 0.53). In conclusion, in the first 2 y, SRC could be produced in a more effective and environmentally friendly manner without mineral fertilizer. 相似文献
13.
In grazed pasture systems, a major source of N 2O is nitrogen (N) returned to the soil in animal urine. We report in this paper the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), applied in a fine particle suspension (FPS) to reduce N 2O emissions from dairy cow urine patches in two different soils. The soils are Lismore stony silt loam (Udic Haplustept loamy skeletal) and Templeton fine sandy loam (Udic Haplustepts). The pasture on both soils was a mixture of perennial ryegrass ( Lolium perenne) and white clover ( Trifolium repens). Total N 2O emissions in the Lismore soil were 23.1–31.0 kg N 2O-N ha −1 following the May (autumn) and August (late winter) urine applications, respectively, without DCD. These were reduced to 6.2–8.4 kg N 2O-N ha −1 by the application of DCD FPS, equivalent to reductions of 65–73%. All three rates of DCD applied (7.5, 10 and 15 kg ha −1) were effective in reducing N 2O emissions. In the Templeton soil, total N 2O emissions were reduced from 37.4 kg N 2O-N ha −1 without DCD to 14.6–16.3 kg N 2O-N ha −1 when DCD was applied either immediately or 10 days after the urine application. These reductions are similar to those in an earlier study where DCD was applied as a solution. Therefore, treating grazed pasture soils with an FPS of DCD is an effective technology to mitigate N 2O emissions from cow urine patch areas in grazed pasture soils. 相似文献
14.
High population pressure in the central highlands of Kenya has led to continuous cultivation of land with minimal additional inputs leading to soil nutrient depletion. Research work has reported positive results from use of manure and biomass from Tithonia, Calliandra, Leucaena, Mucuna and Crotolaria for soil fertility replenishment. An experimental field was set up in Chuka Division to test different soil nutrient replenishment treatments. The experimental design was randomised complete block with 14 treatments replicated three times. At the beginning and end of the experiment, soil was sampled at 0–15 cm depth and analysed for pH, Ca, Mg, K, C, N and P. End of the 2000/2001 short rains (SR) season and 2001 long rains (LR) season, soil samples were taken at 0–30, 30–100 and 100–150 cm for nitrate and ammonium analysis. All the treatments received an equivalent of 60 kg N ha −1, except herbaceous legume treatments, where N was determined by the amount of the biomass harvested and incorporated in soil and control treatment received no inputs. Results indicate soil fertility increased slightly in all treatments (except control) over the 2-year study period. Average maize grain yield across the treatments was 1.1, 5.4, 3.5 and 4.0 Mg ha −1 during the 2000 LR, 2000/2001 SR, 2001 LR and 2001/2002 SR, respectively. The reduced yield in 2000 LR and 2001 LR are attributed to poor rainfall distribution during the two seasons. On average, Tithonia with half recommended rate of inorganic fertilizer recorded the highest (4.8 Mg ha −1) maize yield followed by sole Tithonia (4.7 Mg ha −1). Highest average concentration (144.8 and 115.5 kg N ha −1) of mineral N was recorded at the 30–100 cm soil depth at the end of both 2000/2001 SR and LR, respectively. The lowest average concentration (67.1 kg N ha −1) was recorded in the 100–150 cm soil depth in both seasons, while during the 2001 LR, the 0–30 cm soil depth recorded the lowest concentration (52.3 kg N ha −1). The residual mineral N in the 100–150 cm soil depth doubled at the end of the LR 2001 compared to what was present and the end of the SR 2000/2001 season in all treatments. This shows that there is substantial amount of mineral N that is being leached below the rooting zone of maize in this region. 相似文献
15.
Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N 2O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced 15N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil N new (i.e., N derived from 15N-fertilizer or - 15N-cover crop), with 173 kg N new ha −1 in the conventional system compared to 71.6 and 69.2 kg N new ha −1 in the low-input and organic systems, respectively. In the conventional system, more N new was found in the microaggregate and silt-and-clay fractions, whereas, the N new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N 2O emissions (39.5 g N 2O–N ha −1 day −1) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha −1) produced intermediate N 2O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N 2O emissions, and N availability. 相似文献
16.
Nitrous oxide (N 2O) and methane (CH 4) emitted by anthropogenic activities have been linked to the observed and predicted climate change. Conservation tillage practices such as no-tillage (NT) have potential to increase C sequestration in agricultural soils but patterns of N 2O and CH 4 emissions associated with NT practices are variable. Thus, the objective of this study was to evaluate the effects of tillage practices on N 2O and CH 4 emissions in long-term continuous corn ( Zea mays) plots. The study was conducted on continuous corn experimental plots established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. The experimental design consisted of NT, chisel till (CT) and moldboard plow till (MT) treatments arranged in a randomized block design with four replications. The N 2O and CH 4 fluxes were measured for 1-year at 2-week intervals during growing season and at 4-week intervals during the off season. Long-term NT practice significantly decreased soil bulk density ( ρb) and increased total N concentration of the 0–15 cm layer compared to MT and CT. Generally, NT treatment contained higher soil moisture contents and lower soil temperatures in the surface soil than CT and MT during summer, spring and autumn. Average daily fluxes and annual N 2O emissions were more in MT (0.67 mg m −2 d −1 and 1.82 kg N ha −1 year −1) and CT (0.74 mg m −2 d −1 and 1.96 kg N ha −1 year −1) than NT (0.29 mg m −2 d −1 and 0.94 kg N ha −1 year −1). On average, NT was a sink for CH 4, oxidizing 0.32 kg CH 4-C ha −1 year −1, while MT and CT were sources of CH 4 emitting 2.76 and 2.27 kg CH 4-C ha −1 year −1, respectively. Lower N 2O emission and increased CH 4 oxidation in the NT practice are attributed to decrease in surface ρb, suggesting increased gaseous exchange. The N 2O flux was strongly correlated with precipitation, air and soil temperatures, but not with gravimetric moisture content. Data from this study suggested that adoption of long-term NT under continuous corn cropping system in the U.S. Corn Belt region may reduce GWP associated with N 2O and CH 4 emissions by approximately 50% compared to MT and CT management. 相似文献
17.
PurposeIn grazed pastures, nitrous oxide (N2O), a powerful greenhouse gas and an ozone depletion substance, is mostly emitted from animal excreta, particularly animal urine-N returned to the soil during grazing. We conducted a series of four field lysimeter and plot experiments to assess the potential of using gibberellic acid (GA) and/or alternative pastures or forage crops to mitigate N2O emissions from outdoor dairy farming systems.Materials and methodsPasture and forage plants assessed in the experiments included Italian ryegrass (Lolium multiflorum L.), lucerne (Medicago sativa L.), diverse pastures (including plantain (Plantago lanceolata L.), chicory (Cichorium intybus L.), perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.)), fodder beet (Beta vulgaris L.), kale (Brassica oleracea L.), as well as the standard perennial ryegrass and white clover (RG/WC) pastures. N2O was determined using a standard static chamber method in the field either on top of lysimeters or field plots.Results and discussionThe results showed that the application of GA to urine-treated lysimeters with Italian ryegrass, lucerne or RG/WC pastures did not result in lower N2O emissions. However, the use of diverse pastures which included plantain with a lower urine-N loading rate at about 500 kg N ha?1 significantly decreased N2O emissions by 46 % compared with standard RG/WC with a urine-N loading rate at 700 kg N ha?1. However, when urine-N was applied at the same rates (at 500 or 700 kg N ha?1), the N2O emissions were similar between the diverse and the standard RG/WC pastures. This would indicate that it is the N-loading rate in the urine from the different pastures that determines the N2O emissions from different pastures or forages, rather than the plants per se. The N2O emissions from cow urine from fodder beet were 39 % lower than from kale with the same urine-N application rate (300 kg N ha?1).ConclusionsThese results suggest that N2O emissions can potentially be reduced by incorporating diverse pastures and fodder beet into the grazed pasture farm system. Further studies on possible mechanisms for the lower N2O emissions from the different pastures or forages would be useful. 相似文献
18.
Nitrogen amendment followed by flooding irrigation is a general management practice for a wheat–maize rotation in the North China Plain, which may favor nitrification and denitrification. Consequently, high emissions of nitrous oxide (N 2O) and nitric oxide (NO) are hypothesized to occur. To test this hypothesis, we performed year-round field measurements of N 2O and NO fluxes from irrigated wheat–maize fields on a calcareous soil applied with all crop residues using a static, opaque chamber measuring system. To interpret the field data, laboratory experiments using intact soil cores with added carbon (glucose) and nitrogen (nitrate, ammonium) substrates were performed. Our field measurements showed that pulse emissions after fertilization and irrigation/rainfall contributed to 73% and 88% of the annual N 2O and NO emissions, respectively. Soil moisture and mineral nitrogen contents significantly affected the emissions of both gases. Annual emissions from fields fertilized at the conventional rate (600 kg N ha −1 yr −1) totaled 4.0 ± 0.2 and 3.0 ± 0.2 kg N ha −1 yr −1 for N 2O and NO, respectively, while those from unfertilized fields were much lower (0.5 ± 0.02 kg N ha −1 yr −1 and 0.4 ± 0.05 kg N ha −1 yr −1, respectively). Direct emission factors (EF ds) of N 2O and NO for the fertilizer nitrogen were estimated to be 0.59 ± 0.04% and 0.44 ± 0.04%, respectively. By summarizing the results of our study and others, we recommended specific EF ds (N 2O: 0.54 ± 0.09%; NO: 0.45 ± 0.04%) for estimating emissions from irrigated croplands on calcareous soils with organic carbon ranging from 5 to 16 g kg −1. Nitrification dominated the processes driving the emissions of both gases following fertilization. It was evident that insufficient available carbon limited microbial denitrification and thus N 2O emission. This implicates that efforts to enhance carbon sink in calcareous soils likely increase their N 2O emissions. 相似文献
19.
The objective of this study is to evaluate different agricultural land‐use practices in terms of N leaching and to give recommendations for a sustainable agriculture on sandy soils in Middle Germany. Soil mineral N (N min) and leachate N were quantified at a sandy soil in N Saxony during 3 years. Two treatments were applied: intensive (I)—using inorganic and organic fertilizer and pesticides, and organic (O)—exclusively using organic fertilizer, legume‐based crop rotation, and no pesticides. Split application of mineral fertilizers did not result in substantial N losses at treatment I. Legumes induced a considerable increase of soil mineral N and particularly of leachate mineral N (N min_perc) at treatment O. High N min_perc concentrations (up to 78 mg N L –1) were observed during as well as after the cultivation of legumes. These high N min_perc concentrations are the reason why clearly higher N min_perc losses were determined at treatment O (62 kg N ha –1 y –1) compared to treatment I (23 kg N ha –1 y –1). At both treatments, the quantity of N losses was strongly affected by the precipitation rates. Concentrations and losses of dissolved organic N (DON perc) were assessed as above average at both treatments. The results suggest that the DON perc concentration is influenced by precipitation, soil coverage, and organic fertilizers. Higher values were determined in the percolation water of treatment O. The average annual DON perc losses amounted to 15 kg N ha –1 at I and to 32 kg N ha –1 at O. The average monthly percentage of DON perc losses on the loss of the dissolved total N of percolation water (DTN perc) ranged between <1% and 55% at O and between 2% and 56% at I. For the whole measuring period of 29 months, the relative amounts of DON perc of DTN perc (21% at O and 25% at I) were more or less the same for both treatments. The results show that DON perc can contribute significantly to the total N loss, confirming the importance to consider this N fraction in N‐leaching studies. It was concluded that at sandy sites, a split application of mineral fertilizers, as applied at treatment I, seems to be more expedient for limiting the N leaching losses than legume‐based crop rotations. 相似文献
20.
Quantifying the nitrous oxide (N 2O) and nitric oxide (NO) fluxes emitted from croplands remains a major challenge. Field measurements in different climates, soil and agricultural conditions are still scarce and emissions are generally assessed from a small number of measurements. In this study, we report continuously measured N 2O and NO fluxes with a high temporal resolution over a 2-year crop sequence of barley and maize in northern France. Measurements were carried out using 6 automatic chambers at a rate of 16 mean flux measurements per day. Additional laboratory measurements on soil cores were conducted to study the response of NO and N 2O emissions to environmental conditions.The detection limit of the chamber setup was found to be 3 ng N m −2 s −1 for N 2O and 0.1 ng N m −2 s −1 for NO. Nitrous oxide fluxes were higher than the threshold 37% of the time, while they were 72% of the time for NO fluxes.The cumulated annual NO and N 2O emissions were 1.7 kg N 2O-N ha −1 and 0.5 kg NO-N ha −1 in 2007, but 2.9 kg N 2O-N ha −1 and 0.7 kg NO-N ha −1 in 2008. These inter-annual differences were largely related to crop types and to their respective management practices. The forms, amounts and timing of nitrogen applications and the mineralization of organic matter by incorporation of crop residues were found to be the main factor controlling the emissions peaks. The inter-annual variability was also due to different weather conditions encountered in 2007 and 2008. In 2007, the fractioned N inputs applied on barley (54 kg ha −1 in March and in April) did not generate N 2O emissions peaks because of the low rainfall during the spring. However, the significant rainfall observed in the summer and fall of 2007, promoted rapid decomposition of barley residues which caused high levels of N 2O emissions. In 2008, the application of dairy cattle slurry and mineral fertilizer before the emergence of maize (107 kg N min ha −1 or 130 kg N tot ha −1 in all) coincided with large rainfalls promoting both NO and N 2O emissions, which remained high until early summer.Laboratory measurements corroborated the field observations: NO fluxes were maximum at a water-filled pore space (WFPS) of around 27% while N 2O fluxes were optimal at 68% WFPS, with a maximum potentially 14 times larger than for NO. 相似文献
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