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1.
为探究不同间伐强度对杉木人工林土壤碳氮及其组分特征的影响,以福建省三明市官庄国有林场11年生杉木(Cunninghamia lanceolata)人工林为研究对象,采用弱度间伐(LIT)、中度间伐(MIT)、强度间伐(HIT)等3种间伐强度,研究不同间伐强度林分0—10,10—20,20—40,40—60,60—80,80—100 cm土层总有机碳(SOC)、全氮(TN)及易氧化有机碳(ROC)、硝态氮(NO_3~--N)、铵态氮(NH_4~+-N)、微生物量碳(MBC)、微生物量氮(MBN)、微生物熵碳(qMBC)、微生物熵氮(qMBN)的变化特征,以探讨不同间伐强度对杉木人工林土壤碳氮及其组分特征的影响。结果表明:间伐降低了土壤SOC和TN的含量,降低幅度分别为1.4%～36.9%,3.1%～45.7%。间伐增加了土壤MBC、NO_3~--N的含量,而对ROC、NH_4~+-N和MBN的程度在不同土层有差异,qMBC和qMBN随着间伐强度的增加而增大。相关性分析表明,土壤SOC分别与TN、qMBC、ROC、NH_4~+-N、MBC、MBN呈极显著正相关(P0.01);TN与qMBN、ROC、NH_4~+-N、MBC、MBN呈极显著正相关(P0.01)。杉木人工林间伐处理降低了土壤表层SOC和TN含量,增加了土壤SMBC和qMBC、qMBN,同时也增加了土壤表层(0—10 cm)SMBN。抚育间伐导致土壤SOC和TN含量降低主要是由于活性碳、氮含量的增加,提高土壤中有机质分解速率,最终导致土壤SOC和TN含量降低。 相似文献
2.
PurposeSustainable management of riparian zone soils is required to ensure the health of natural ecosystems and maintenance of soil nitrogen (N) pools and soil N cycling. However, the effect of revegetation type and age on soil N pools remains poorly understood. Materials and methodsThis study compiled data from published articles to understand the effects of revegetation types and age on soil total N (TN) and soil inorganic N (NH4+-N, and NO3?-N) using a meta-analysis. We extracted 645 observations from 52 published scientific articles. Results and discussionThe revegetation of riparian zones led to a significant increase of soil TN (mean effect size: 11.5%; 95% CI: 3.1% and 20.6%). Woodland increased soil TN significantly by 14.0%, which was associated with the presence of N fixing species and high litter inputs. Soil NH4+-N concentration significantly increased (mean effect size: 20.1%; 95% CI: 15.1% and 25.4%), whereas a significant decrease in soil NO3?-N (mean effect size: ? 21.5%; 95% CI: ? 15.0% and ? 27.5%) was observed. Of the revegetation types considered in this paper, NO3?-N concentration in soil followed the order: grassland < shrubland < woodland, suggesting that woodland might be more efficient in soil NO3?-N retention than grassland. The high plant N uptake and accelerated NO3?-N leaching in grassland could be related to the decreased soil NO3?-N in grassland compared with other revegetation types. Revegetation significantly decreased soil moisture by (mean effect size: ? 7.9%; 95% CI: ? 3.3% and ? 12.2%) compared with the control, which might be associated with the selection of exotic species as dominant vegetation in the riparian zone. Soil TN increased in revegetation ages between 10 and 40 years following revegetation and was related to increased soil organic carbon inputs within those ages following the establishment. ConclusionsThis study provides insight into influence of different vegetation types and age on soil N pools and soil moisture. This study also highlights the importance of revegetation in riparian zones to increase soil TN. 相似文献
3.
Carbon sequestration via sound agronomic practices can assist in combating global warming. Three long-term experiments (Experiment 502, Experiment 222, and The Magruder Plots) were used to evaluate the effect of fertilizer nitrogen (N) application on soil organic carbon (SOC), total nitrogen (TN), and pH in continuous winter wheat. Soil samples (0–15 cm) were obtained after harvest in 2014, analyzed, and compared to soil test results from these experiments in 1993. Soil pH decreased with increasing N fertilization, and more so at high rates. Nitrogen application significantly increased TN in Experiment 502 from 1993 to 2014, and TN tended to be high at high N rates. Fertilizer N significantly increased SOC, especially when N rates exceeded 90 kg ha ?1. The highest SOC (13.1 g kg ?1) occurred when 134 kg N ha ?1 was applied annually. Long-term N application at high rates increased TN and SOC in the surface soil. 相似文献
4.
PurposeHulunbuir steppe has flat terrain and wide riparian zone of rivers and lakes on it. Owing to climate change, these riparian zones are often submerged or dried. This not only results in the instability of biodiversity in these regions but also affects the soil biogeochemical cycles. Soil C:N:P ecological stoichiometry plays a vital role in predicting and understanding the balance of multiple chemicals in ecological interactions. However, few studies have examined the soil C:N:P ecological stoichiometry in riparian zones of Hulunbuir steppe under different submergence states. Our objectives were to explore whether submergence frequencies impact soil C:N:P stoichiometry and identify the key factors. Materials and methodsFour study sites were selected along the Hui river in Hulunbuir steppe, and three plots of different submergence frequencies, high (HF-sub, 5 to 7 times per year), moderate (MF-sub, 2 to 3 times per year), and low (LF-sub, unflooded or flooded once per year), were selected for each study site. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), their ecological stoichiometric ratios (soil C:N, N:P, and C:P), soil ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3?-N), available phosphorus (AP), soil pH, electrical conductivity (EC), soil moisture content (SMC), soil bulk density (SBD), porosity, and hardness were measured and analyzed. Results and discussionThe results indicated that soil C:N:P ecological stoichiometry was notably affected by submergence frequency across the four study sites (P?<?0.05). SOC, TN, TP, and their stoichiometric ratios changed regularly with the submergence frequency change, whereas their trends were inconsistent at different drainage basins. Soil C:N decreased with the decrease in submergence frequency but kept in a narrow scope, whereas the N:P and C:P were changed greatly under different submergence frequencies. Further analysis found that these significant variations in N:P and C:P were mainly due to the changes in soil TP which suggested there might be a P limitation in the riparian zones. The results of redundancy analysis (RDA) and path analysis indicated that soil AP and NO3?-N were the key indirect factors affecting soil C:N:P ecological stoichiometry under different submergence frequencies, and SMC was an indirect factor. ConclusionsWe demonstrated that the soil C:N:P ecological stoichiometry was significantly affected by the submergence frequency in the riparian zones of Hulunbuir steppe. Soil N:P and C:P were more susceptible to change than C:N under different submergence frequencies. If the contents of soil AP and NO3?-N were appropriate, soil C:N:P ecological stoichiometry will be more beneficial to regulating the cycle and balance of soil nutrient elements in the riparian zones, which can promote the riparian zones to provide better ecological functions. 相似文献
5.
Future climate change is predicted to influence soil moisture regime, a key factor regulating soil nitrogen (N) cycling. To elucidate how soil moisture affects gross N transformation in a cultivated black soil, a 15N tracing study was conducted at 30%, 50% and 70% water-filled pore space (WFPS). While gross mineralization rate of recalcitrant organic N (N rec) increased from 0.56 to 2.47 mg N kg −1 d −1, the rate of labile organic N mineralization declined from 4.23 to 2.41 mg N kg −1 d −1 with a WFPS increase from 30% to 70%. Similar to total mineralization, no distinct moisture effect was found on total immobilization of ammonium, which primarily entered the N rec pool. Nitrate (NO 3−) was mainly produced via autotrophic nitrification, which was significantly stimulated by increasing WFPS. Unexpectedly, heterotrophic nitrification was observed, with the highest rate of 1.06 mg N kg −1 d −1 at 30% WFPS, contributing 31.8% to total NO 3− production, and decreased with WFPS. Dissimilatory nitrate reduction to ammonium (DNRA) increased from near zero (30% WFPS) to 0.26 mg N kg −1 d −1 (70% WFPS), amounting to 16.7–92.9% of NO 3− consumption. A literature synthetic analysis from global multiple ecosystems showed that the rates of heterotrophic nitrification and DNRA in test soil were comparative to the forest and grassland ecosystems, and that heterotrophic nitrification was positively correlated with precipitation, soil organic carbon (SOC) and C/N, but negatively with pH and bulk density, while DNRA showed positive relationships with precipitation, clay, SOC, C/NO 3− and WFPS. We suggested that low pH and bulk density and high SOC and C/N in test soil might favor heterotrophic nitrification, and that C and NO 3− availability together with anaerobic condition were crucial for DNRA. Overall, our study highlights the role of moisture in regulating gross N turnover and the importance of heterotrophic nitrification for NO 3− production under low moisture and DNRA for NO 3− retention under high moisture in cropland. 相似文献
6.
为探究微塑料输入与秸秆添加对农田土壤氮淋溶的影响，以潮土和黄棕壤为研究对象，每种土壤各设置8个处理，包括对照（CK）、低量微塑料（PE1）、中量微塑料（PE2）、高量微塑料（PE3）、秸秆（S）、秸秆+低量微塑料（S+PE1）、秸秆+中量微塑料（S+PE2）、秸秆+高量微塑料（S+PE3），研究了添加秸秆与不添加秸秆条件下，不同微塑料输入量对土壤氮淋溶的影响。结果表明，仅添加微塑料条件下，与对照（CK）相比，潮土PE1、PE2、PE3处理总氮（TN）淋溶量均无显著差异，黄棕壤仅PE1处理显著增加了TN淋溶量。在添加秸秆（S）处理中，与对照（CK）相比，潮土添加秸秆后显著降低了硝态氮（NO 3--N）、铵态氮（NH 4+-N）、TN淋溶量，分别降低了31.15%、13.45%、15.26%，黄棕壤添加秸秆后显著增加了TN淋溶量，增加了22.56%。添加秸秆处理相较于不添加秸秆处理，潮土各浓度微塑料输入下NO 3--N、NH 4+-N、TN的累计淋溶量呈降低趋势，而黄棕壤低量微塑料输入降低了TN淋溶量，高量微塑料输入增加了TN淋溶量。偏最小二乘路径模型（PLS-PM）分析表明，在潮土中添加秸秆主要通过影响淋溶液pH和NO 3--N淋溶量影响氮素淋溶，微塑料添加量对氮淋溶无显著影响；在黄棕壤中添加秸秆主要通过影响淋溶液NO 3--N、NH 4+-N淋溶量影响氮淋溶，微塑料添加量主要通过影响淋溶液NH 4+-N淋溶量影响氮淋溶。研究结果可为农田土壤微塑料污染风险的管控及减少土壤氮素的淋失提供依据。 相似文献
7.
In this study, the concentrations and loads of different forms of nitrogen [nitrate nitrogen (NO 3-N), total Kjeldahl nitrogen (TKN), and total nitrogen (TN)] in the headwater catchment of the Mero River (NW Spain) were analyzed. The TN concentrations were relatively low (mean: 2.57 mg L ?1). Nitrate was the predominant form of N in the Mero catchment, accounting for 76.65 percent of the TN concentration. Measured NO 3-N concentrations were always lower than the maximum allowed drinking water concentration. An annual TN load of 61.2 Mg was computed, representing an export of 0.94 Mg km ?2 y ?1, whereas annual exports NO 3-N and TKN were of 0.79 and 0.15 Mg km ?2 y ?1, respectively. 相似文献
8.
为明确肥料氮素在土壤中的迁移转化动态特征,利用模拟土柱方法,研究了3倍常规施肥量条件下不同肥料处理(尿素、硫铵)黑土的矿质氮变化。结果表明:不同氮肥处理的氮素养分迁移转化特征有明显差异。对照处理(不施肥)土柱内各层次间NH4+-N和NO3--N含量差异不明显;施用尿素或硫铵后,表层0~50mm土层的NH4+-N和NO3--N含量比不施肥对照分别升高100.8~3408.1mg·kg-1、113.4~388.0mg·kg-1和126.7~4671.1mg·kg-1、51.4~63.3mg·kg-1,且在培养前14d内变化最大。在整个培养期内,施用硫铵处理各层次NH4+-N平均含量比尿素处理高2.54~1423.7mg·kg-1,NO3--N平均含量低4.38~335.1mg·kg-1;而尿素处理各层次的硝化率是硫铵处理的0.79~9.12倍。表明肥料氮素的迁移与转化集中在0~50mm土层内,尿素处理的氮素转化速率较硫铵处理高。 相似文献
9.
The objective of this study was to investigate the effect of adding flue gas desulphurization gypsum (FGDG) on the transformation and fate of nitrogen during co-composting of dairy manure and pressmud of a sugar refinery. The ammonia absorption of FGDG was investigated. The changes in compost temperature, pH, electrical conductivity (EC), moisture, organic matter, the C/N ratio, Kjeldahl N, NH 4+-N, NO 2?-N, NO 3?-N were assessed. The addition of FGDG did not significantly affect compost temperature, pH, EC, moisture, and organic matter degradation. However, the addition of FGDG significantly increased the NH 4+-N content in the compost during the thermophilic phase, and the NH 4+-N maximal content in the compost with FGDG (CP+G) was 59.9% more than that in the compost without FGDG (CP–G). FGDG was thought to create the formation of (NH 4) 2SO 4 and the cation exchange between NH 4+ and Ca 2+. The NO 2?-N content in the CP+G peaked on day 15, and was not observed in the CP–G. In the final compost products, the NO 3?-N concentration in the CP–G was more than that in the CP+G, which was 1451 (CP–G) and 1109 mg ·kg ?1 (CP+G) dry material. This might be due to the NO 2? accumulation in the CP+G, which accelerated N loss in the form of N 2O. There is a strong correlation between N 2O emission and NO 2?-N accumulation in the composting process. Compared with the original N content in the compost mixture, the N loss in CP–G and CP+G were 15.0 and 10.8%, respectively. These results revealed that NH 4+-N conservation effect was improved during the thermophilic phase and the total N loss was mitigated by adding FGDG into composting materials. FGDG could be utilized as a potential amendment to conserve nitrogen during composting. 相似文献
10.
Phosphorus uptake is often enhanced by ammonium compared to nitrate nitrogen nutrition of plants. A decrease of pH at the soil-root interface is generally assumed as the cause. However, an alteration of root growth and the mobilization of P by processes other than net release of protons induced by the source of nitrogen may also be considered. To study these alternatives a pot experiment was conducted with maize using a fossil Oxisol high in Fe/Al-P with low soil solution P concentration. Three levels of phosphate (0, 50, 200 mg P kg ?1) in combination with either ammonium or nitrate nitrogen (100 mg N kg ?1) were applied. Plants were harvested 7 and 21 d after sowing, P uptake measured and root and shoot growth determined. To assess the importance of factors involved in the P transfer from soil into plants, calculations were made using a model of Barber and Claassen. In the treatments with no and low P supply NH 4-N compared to NO 3-N nutrition increased the growth of the plants by 25 % and their shoot P content by 38 % while their root growth increased by 6 % only. The rhizosphere pH decreased in the NH 4-N treatments by 0.1 to 0.6 units as compared to the bulk soil while in the NO 3-N treatments it increased by 0.1 to 0.5 units. These pH changes had a minor influence on P uptake only, as was demonstrated by artificially altering the soil pH to 4.7 and 6.3 respectively. At the same rhizosphere pH, however, P influx was doubled by the application of NH 4-compared to NO 3-N. It is concluded that in this soil the enhancement of P uptake of maize plants after ammonium application cannot be attributed to the acidification of the rhizosphere but to effects mobilizing soil phosphate or increasing P uptake efficiency of roots. Model calculation showed that these effects accounted for 53 % of the P influx per unit root length in the NO 3-N and 72 % in the NH 4-N supplied plants if no P was applied. With high P application the respective figures were only 18 and 19%. 相似文献
11.
PurposeWetlands in Mu Us Desert have severely been threatened by grasslandification over the past decades. Therefore, we studied the impacts of grasslandification on soil carbon (C):nitrogen (N):phosphorus (P) stoichiometry, soil organic carbon (SOC) stock, and release in wetland-grassland transitional zone in Mu Us Desert. Materials and methodsFrom wetland to grassland, the transition zone was divided into five different successional stages according to plant communities and soil water conditions. At every stage, soil physical and chemical properties were determined and C:N:P ratios were calculated. SOC stock and soil respirations were also determined to assess soil carbon storage and release. Results and discussionAfter grasslandification, SOC contents of top soils (0–10 cm) decreased from 100.2 to 31.79 g kg?1 in June and from 103.7 to 32.5 g kg?1 in October; total nitrogen (TN) contents of top soils (0–10 cm) decreased from 3.65 to 1.85 g kg?1 in June and from 6.43 to 3.36 g kg?1 in October; and total phosphorus (TP) contents of top soils (0–10 cm) decreased from 179.4 to 117.4 mg kg?1 in June and from 368.6 to 227.8 mg kg?1 in October. From stages Typha angustifolia wetland (TAW) to Phalaris arundinacea L. (PAL), in the top soil (0–10 cm), C:N ratios decreased from 32.2 to 16.9 in June and from 19.0 to 11.8 in October; C:P ratios decreased from 1519.2 to 580.5 in June and from 19.0 to 11.8 in October; and N:P ratios decreased from 46.9 to 34.8 in June and changed from 34.9 to 34.0 in October. SOC stock decreased and soil respiration increased with grasslandification. The decrease of SOC, TN, and TP contents was attributed to the reduction of aboveground biomass and mineralization of SOM, and the decrease of soil C:N, C:P, and N:P ratios was mainly attributed to the faster decreasing speeds of SOC than TN and TP. The reduction of aboveground biomass and increased SOC release led by enhanced soil respiration were the main reasons of SOC stock decrease. ConclusionsGrasslandification led to lowers levels of SOC, TN, TP, and soil C:N, C:P, and N:P ratios. Grasslandification also led to higher SOC loss, and increased soil respiration was the main reason. Since it is difficult to restore grassland to original wetland, efficient practices should be conducted to reduce water drainage from wetland to prevent grasslandification. 相似文献
12.
A long-term experiment on combined inorganic fertilizers and organic matter in paddy rice ( Oryza sativa L.) cultivation began in May 1982 in Yamagata, northeastern Japan. In 2012, after the 31 st harvest, soil samples were collected from five fertilizer treatments [(1) PK, (2) NPK, (3) NPK + 6 Mg ha ?1 rice straw (RS), (4) NPK + 10 Mg ha ?1 rice straw compost (CM1), and (5) NPK + 30 Mg ha ?1 rice straw compost (CM3)], at five soil depths (0–5, 5–10, 10–15, 15–20 and 20–25 cm), to assess the changes in soil organic carbon (SOC) content and carbon (C) decomposition potential, total nitrogen (TN) content and nitrogen (N) mineralization potential resulting from long-term organic matter addition. The C decomposition potential was assessed based on the methane (CH 4) and carbon dioxide (CO 2) produced, while the N mineralization potential was determined from the potassium chloride (KCl)-extractable ammonium-nitrogen (NH 4+-N), after 2, 4, 6 and 8 weeks of anaerobic incubation at 30°C in the laboratory. Compared to NPK treatment, SOC in the total 0–25 cm layer increased by 67.3, 21.0 and10.8%, and TN increased by 64.2, 19.7 and 10.6%, in CM3, RS and CM1, respectively, and SOC and TN showed a slight reduction in the PK treatment by 5.2 and 5.7%, respectively. Applying rice straw compost (10 Mg ha ?1) instead of rice straw (6 Mg ha ?1) to rice paddies reduced methane production by about 19% after the soils were measured under 8 weeks of anaerobic incubation at 30°C. Soil carbon decomposition potential ( Co) and nitrogen mineralization potential ( No) were highly correlated with the SOC and TN contents. The mean ratio of Co/ No was 4.49, lower than the mean ratio of SOC/TN (13.49) for all treatments, which indicated that the easily decomposed organic matter was from soil microbial biomass and soil proteins. 相似文献
13.
PurposeStraw residue has been widely applied in the North China Plain agroecosystems due to their positive roles in soil fertility improvement, sustainable production, and climate change mitigation. However, little is known about how straw application alters soil respiration by influencing soil biochemical properties in this region. This is the first study to evaluate the role of soil enzyme activity and glomalin content in the response of soil respiration to straw application at different growth stages in a wheat-maize rotation system.Materials and methodsField experiment was conducted in a wheat-maize rotation system and it contained two treatments: straw residue removal (CK) and straw residues application (SR). Soil respiration, moisture, and temperature were measured using LI-8100 at different growth stages during wheat and maize (2013–2015) growing seasons. From 2013 to 2014, soil sample (0–20 cm) was collected at different growth stages during wheat and maize growing seasons and transported to the laboratory. Glomalin content and soil enzyme activity were analyzed by using Bradford and enzyme-labeled meter method, respectively. In addition, we determined soil chemical properties such as soil organic carbon (SOC), soil total N content (TN), ammonium N (NH4 +-N), and nitrate N (NO3 ?-N) concentrations.Results and discussionSR significantly increased soil respiration and this promotion effect became more significant after 4-year straw application. Soil respiration exhibited significant seasonal variation and was significantly increased by soil temperature with Q 10 ranging from 1.73 to 2.14 for CK and from 1.51 to 2.28 for SR. Both soil temperature and moisture accounted for 70–72% of the seasonal variation in soil respiration. SR significantly increased easily extractable glomalin-related soil protein during 2013–2014 wheat growing season except jointing stage. In addition, positive and significant effect of SR on activities of β-glucosidase and cellobiohydrolase was observed at initial and vigorous growth stages. Straw application significantly increased TN, but did not significantly influence SOC, NH4 +-N, and NO3 ?-N concentrations.ConclusionsOur study demonstrated that straw application increased soil respiration by stimulating soil enzyme activities and improving easily extractable glomalin-related soil protein. Straw application is recommended as an agricultural management in the North China Plain because of its role in improving biochemical properties. To improve soil biochemical parameters with a relative low soil respiration rate, further information is necessary about the optimum amount of straw application. 相似文献
14.
Root development responds not only to the quantity of inorganic nitrogen in the rhizosphere, but to its form, NH 4+ or NO 3?. Root growth of tomato showed a hyperbolic response to soil levels of inorganic nitrogen: very few roots were found in soil blocks depleted in inorganic nitrogen, roots proliferated as soils increased to 2 μg NH 4+-N g ?1 soil or 6 μg NO 3?-N g ?1 soil, and root growth declined in soils with the higher levels of inorganic nitrogen. High NH 4+ concentrations inhibited root growth, but low concentrations promoted the development of an extensive, fine root system. Supply with NO 3? as the sole nitrogen source led to a more compact root system. These differences in root morphology under NH 4+ and NO 3? nutrition may be mediated through pH. Rice and maize roots absorbed NH 4+ most rapidly right at the apex and appeared to assimilate this NH 4+ in the zone of elongation. During NH 4+ assimilation, root cells must release protons, and the resulting acidification around the walls of cells in this region should stimulate root extension. By contrast, NO 3? absorption reached a maximum in the maturation zone of rice and maize roots, and this NO 3? was probably assimilated in more basal regions. Absorption of NO 3? requires proton efflux, whereas NO 3? assimilation requires proton influx. The net result under NO 3? nutrition was only subtle shifts in rhizosphere pH that probably would not influence root elongation. The signal through which roots detect changes in rhizosphere NH 4+ and NO 3? levels is still obscure. It is proposed that a product of nitrogen metabolism such as nitric oxide serves as a signal. 相似文献
15.
Most investigations into the effects of changing soil pH on microbial activity use, from necessity, soils taken from different sites so that soil physical and chemical properties are confounded. Studies along continuous gradients of soil pH within a single soil type are rare, simply because so few exist, in UK or even worldwide. Here we report measurements of mineralisation of native organic matter and added arginine along a continuous soil pH gradient (range about pH 3.7–8.3) of a UK silty clay loam soil (Chromic Luvisol or Typic Paleudalf). The soil has been maintained under constant management for more than 100 years, with winter wheat sown annually. The soil NH 4+-N concentration was maximal at the lowest pH (pH 3.7), declining exponentially until pH 5.5 and remaining negligible thereafter. However, unexpectedly, soil NO 3?-N concentration was also maximal at pH 3.7 and was significantly negatively correlated with increasing pH thereafter. To investigate these unexpected NO 3?-N results, arginine was added as a labile source of organic N and its extent of ammonification and nitrification measured at soil pHs 3.79, 4.42, 6.08 and 7.82. While arginine ammonification was apparently greatest at pHs 3.79 and 4.42, similar to mineralisation of soil organic N, nitrification of this added N was greatest at soil pH 7.82 and least at pH 3.79, the reverse of the situation with soil organic N, but much more in line with what was expected. It was concluded that the decline in soil NO 3?-N with increasing pH in the unamended soils was an artefact, caused by increasing plant uptake of NO 3?-N as yield increased, rather than a true effect of low pH increasing nitrification of soil organic N. Our results differ from most previous studies, which showed poor correlations between soil pH and arginine mineralisation. This was attributed to our use of much longer incubation times (up to 50 days) than usually employed. Under our conditions, arginine was therefore shown to be a useful model for mineralisation of labile soil organic N. 相似文献
16.
Vermicompost, a byproduct of earthworm digestion of organic solid waste is receiving attention as a peat substitute in the production of plug seedling media. We aimed to test the effects of adding nitrogen to vermicompost on the morphological development of tomato seedlings. Nursery experiments on tomato seedlings were carried out in the greenhouse. Urea at 0.00 kg/m 3, 0.25 kg/m 3, 0.50 kg/m 3, and 1.00 kg/m 3 was added to vermicompost and to the vermicompost-vermiculite (at a volume ratio of 4:1) mixture. Results showed that (1) Nitrogen application at different rates to the vermicompost significantly increased the strong seedling index (SSI) at the middle (T1) and late (T2) seedling growth stages. Besides, nitrogen application significantly increased concentrations of available nitrogen (available-N) at the beginning of seedling cultivation (T0) and nitrate nitrogen (NO 3?-N) at T2 in vermicompost. (2) Adding nitrogen to vermicompost significantly increased the number of root tips at T1 and T2 and the root volume at T2. And it significantly decreased the electrical conductivity (EC), total N (TN), available N, ammonium N (NH 4+-N), and NO 3?-N at T1 and T2. (3) Adding nitrogen to the vermicompost-vermiculite mixture significantly increased the root/shoot ratio, and SSI at T1 and T2. And it significantly increased the pH and reduced the EC at T1 and the available-N, NH 4+-N, and NO 3?-N at T2. In short, adding nitrogen (0.5～1.0 kg/m 3 urea) to vermicompost improved the shoot and root morphological development of tomato seedlings, as well as the biomass accumulation and allocation. Adding nitrogen to the vermicompost-vermiculite mixture further promoted the development of tomato seedlings. 相似文献
17.
The aim of this study was to evaluate the sustainability of an agro-industry sludge as a nitrogen (N) fertilizer in perennial crops by assessing its dynamics of release of: 1) N as ammonium (NH 4+)- and nitrate (NO 3?)-N, and 2) carbon as soil respiration. In incubation assay, application of agro-industry sludge promoted the maximum NH 4+-N concentration (50 mg kg ?1) 2 h after application, then it decreased with time until day 26. NO 3?-N increased, reaching the maximum between day 60 and day 100, according to a second degree function. Agro-industry sludge showed a slower release of NO 3?-N compared with urea. Soil basal respiration and cumulative amount of carbon dioxide were higher in sludge from day 71 on. In field, soil NO 3?-N increased after fertilization treatments and was higher in Calcari Stagnic Cambisols soil. Sludge showed a potential lower environment impact in terms of mineral N release, than urea. 相似文献
18.
This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO 3-N) and ammonium (NH 4-N) from each amendment averaged 115 kg N ha ?1 at application and 25 kg N ha ?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg ?1, 4 wk after emergence to 3,000 mg N kg ?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg ?1, 10,000 mg K kg ?1, and 2,000 mg S kg ?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha ?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments. 相似文献
19.
Inhibition of nitrification as a mitigation tool to abate nitrogen (N) losses and improve N use efficiency (NUE) is a promising technology. Nitrification inhibitor (dicyandiamide, DCD) was evaluated in two consecutive wheat-maize rotations (2015–2017), with two different N fertilizer levels applied in wheat (160, 220 kg N ha ?1) and maize (180, 280 kg N ha ?1). More NH 4+-N contents (101% and 102% in wheat and 74% and 73% in maize) and less NO 3–-N contents (37% and 43% in wheat and 46% and 57% in maize) were observed at both N levels treated with DCD compared to without DCD. Higher pH, lower EC and reduced NO 3–-N accumulation were the other benefits of DCD. The NO 3–-N accumulation within the 0–200 cm soil profile was significantly less at both N levels with DCD (66 mg kg ?1 and 121 mg kg ?1) compared to without DCD (96 mg kg ?1 and 169 mg kg ?1). Application of DCD also improved the growth and yield in both crops. Increase in NUE from 38% to 49% in wheat and 27% to 33% in maize with DCD at higher N level was also observed. Overall, the effectiveness of DCD in retarding the nitrification process was higher in wheat than maize. 相似文献
20.
Soil NH +4-N and NO ?3-N at five soil depths (0–10, 10–20, 20–40, 40–60, 60–80 cm) and some environmental variables were measured in a field trial under fallow and wheat for 9 months.Significant linear and quadratic relationships were obtained relating soil NH +4-N, NO ?3-N, NH +4-N + NO ?3-N, and NH +4-N + NO ?3 + total-N uptake by wheat to soil heat accumulation (temperature), moisture, and rainfall. R 2 values generally decreased with soil depth and the maximum value (37%) was obtained for NO ?3-N changes in the topsoil (0–10 cm).Although a considerable amount of variation in the inorganic values recorded is not included in the equations, our results suggest that the development of the above relationships particularly of the quadratic type are useful to predict crop requirements for N by measurement of environmental variables in the field. 相似文献
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