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1.
The effect of presubmergence and green manuring on various processes involved in [15N]‐urea transformations were studied in a growth chamber after [15N]‐urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH3 volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH4+‐N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH3 volatilization losses. Although green manure did not affect the KCl extractable NH4+‐N from applied fertilizer, it maintained higher NH4+‐N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9 % (T1), 23.9 % (T2), and 36.4 % (T3) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N.  相似文献   

2.
 The effects of floodwater algae and green manure on transformations of 15N-urea were studied in columns of a sandy loam soil in a growth chamber. The columns were flooded and either kept in the light, to allow algal growth, or in the dark (control) for 17 days before adding the labelled urea. Changes in urea-, NO3 –- and NH4 +-N levels and the pH of the floodwater were measured over the subsequent 41-day period, during which the control column remained in the dark and those containing algae were maintained either in the dark to cause the death of the algae or in the light. Volatilized NH3 was monitored, and on termination of the experiment the distribution of 15N between NO3 –, NH4 + and organic forms was measured in the soil. Urea hydrolysis was most rapid in the presence of both living algae and green manure, followed by dead algae, and was slowest in the control. The concentration of NH4 +-N in the floodwater was, however, reduced in the presence of algae due to assimilation and NH3 volatilization owing to the raised day-time pH in the floodwater. NH3 volatilization for the first 10 days was rather high in the columns kept in the light compared to those in the dark. Total volatilization plus denitrification losses were greatest where dead algae were present, owing to the absence of live algae which assimilated more than half of the applied N. Algal growth in floodwater increased the depth of the aerobic soil layer present at the soil-water interface. Subsequently, under dark conditions, stimulated algal growth reduced the depth of the aerobic layer causing less nitrification, which resulted in lower losses of N due to denitrification, i.e. 17% of the applied urea-N as compared to 39% in the light treatments. Although the presence of green manure caused a marked increase in the rate of hydrolysis, algal assimilation prevented excessive N losses via volatilization, indicating that the retention of higher quantities of NH4 +-N may have increased fertilizer-N use efficiency. Received: 22 January 1999  相似文献   

3.
We have examined the effects of different types of slurry on CH4 and N2O emissions, Zn and Cu contents of rice, and nitrate content of the drainage water. The experiment included four treatments: (1) anaerobically digested cattle slurry (ADCS), (2) ADCS filtered to remove the coarse organic matter fraction, (3) anaerobically digested pig slurry (ADPS), and (4) chemical fertilizer (CF). The application rate was 30?g?NH4?CN?m?2. Different amounts of C were incorporated with fertilization: 725?g?C?m?2 in ADCS, 352?g?m?2 in filtered ADCS, and 75?g?m?2 in ADPS. The average CH4 emissions during a growing period were 304, 359, 452, and 579?mg?m?2?day?1 in the CF, ADPS, filtered ADCS, and ADCS treatments, respectively. The CH4 emission was significantly higher in ADCS than in CF and ADPS. Negligible N2O emissions were observed during the growing period. Comparable concentrations of Zn and Cu were observed in the rice grain among the treatments. In contrast, their concentrations in the stems and leaves were significantly higher in ADPS than in CF treated rice, although the values were lower than the upper limit of feed additives. Nitrate concentrations in the drainage water were consistently low (0.5?mg?N?L?1). The present study suggested that ADPS, containing a lower amount of C than ADCS, might be an organic fertilizer in paddy field with comparable environmental impacts to chemical fertilizers (CF), but long-term field studies are needed to better understand the effects of these organic fertilizers.  相似文献   

4.
Broadcasting of urea to agricultural soils can result in considerable losses by NH3 volatilization. However, it is unclear if the impact of this practice on NH3 emissions is further enhanced when performed on no-till (NT) soils. The objective of this study was to compare NH3 volatilization following broadcasting of urea to NT and moldboard plowed (MP) soils. Intact soil cores were taken shortly after harvest from NT and MP plots of three long-term tillage experiments in Québec (Canada) and stored for 4.5 months prior to incubation. Urea (14 g N m−2) was applied at the soil surface and NH3 volatilization was measured for 30 d using an open incubation system. Mean cumulative NH3 losses were greater (P < 0.001) in NT (3.00 g N m−2) than in MP (0.52 g N m−2). Several factors may have contributed to the higher emissions from the NT soils. Urease activity in the top 1 cm of soils was on average 4.2 times higher in NT than in MP soils. As a result, hydrolysis of urea occurred very rapidly in NT soils as indicated by enhanced NH3 emissions 4 h after application of urea. The presence of crop residues at the surface of NT soils also decreased contact of the urea granules with the soil, possibly reducing adsorption of NH4+ on soil particles. Lower volatilization on the MP soils may also have partly resulted from a fraction of urea granules falling into shallow cracks. Field trials are needed to confirm our finding that NT soils bear greater potential for NH3 volatilization following surface application of urea than MP soils.  相似文献   

5.
太湖地区稻田氨挥发及影响因素的研究   总被引：63，自引：7，他引：63       下载免费PDF全文
应用微气象学方法研究太湖地区水稻三个不同施肥期施用尿素后的氨挥发损失 ,并对其影响因素 (气候、田面水中NH 4 N浓度和作物覆盖等 )的作用进行了分析研究。结果表明 ,水稻施用尿素后的氨挥发损失为各时期施氮量的 18 6 %～ 38 7% ,其中以分蘖肥时期损失最大 ,其次为基肥 ,穗肥氨挥发损失最小。氨挥发损失主要时期是在施肥后 7d内。在水稻不同生长期 ,各因素对氨挥发的影响能力大小并不一样 ,三个施肥期的氨挥发损失通量与施肥后田面水中铵态氮浓度呈显著正相关。  相似文献   

6.
Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid by-products into an organic fertilizer, for which there is growing demand. Because fertilizer application to lawns can increase the risk of nutrient contamination of groundwater, we quantified leaching of NO3–N and PO4–P from perennial ryegrass turf (Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) and synthetic (SY). Field plots were established on an Enfield silt loam, and liquid (L) and granular (G) fertilizer formulations of squid and synthetic fertilizers were applied at 0, 48, 146, and 292 kg N ha−1 year−1. Levels of NO3–N and PO4–P in soil pore water from a depth of 60 cm were determined periodically during the growing season in 2008 and 2009. Pore water NO3–N levels were not significantly different among fertilizer type or formulation within an application rate throughout the course of the study. The concentration of NO3–N remained below the maximum contaminant level (MCL) of 10 mg L−1 until midSeptember 2009, when values above the MCL were observed for SQG at all application rates, and for SYL at the high application rate. Annual mass losses of NO3–N were below the estimated inputs (10 kg N ha−1 year−1) from atmospheric deposition except for the SQG and SYL treatments applied at 292 kg N ha−1 year−1, which had losses of 13.2 and 14.9 kg N ha−1 year−1, respectively. Pore water PO4–P levels ranged from 0 to 1.5 mg P L−1 and were not significantly different among fertilizer type or formulation within an application rate. Our results indicate that N and P losses from turf amended with squid-based fertilizer do not differ from those amended with synthetic fertilizers or unfertilized turf. Although organic in nature, squid-based fertilizer does not appear to be more—or less—environmentally benign than synthetic fertilizers.  相似文献   

7.
 A sandy loam was incubated under floodwater in the laboratory either in the dark or in the light (7 h day, 20  °C; 17 h night, 15  °C) and with four N sources [control, ammonium carbonate [(NH4)2CO3], ammonium chloride (NH4Cl), potassium nitrate (KNO3)]. In the dark, floodwater pH rose steadily from 6.4 to about 7.5 over 60 days in the control, KNO3 and (NH4)2CO3 treatments, but with NH4Cl pH decreased to 5.8. In the light, algal growth began to affect the floodwater pH after 9 days. At the end of the night, pH values were similar for all treatments to those kept in the dark. During the day, pH changes depended on the morning pH value: the daily increase was zero at pH 5.6 rising to a maximum of about 2 units at pH 6.3 and falling again at higher pH values. Changes in the carbonate equilibria in response to CO2 removal by algal photosynthesis partly explain the results, but increasing inputs of acid are also implicated below pH 6.3 possibly due to reduced volatilization and increased nitrification. Redox potential (Eh) in the floodwater was little affected by N treatment until algal growth began. Eh then decreased each day as pH rose and recovered during the night. The daily decrease in Eh per unit increase in pH rose from about 10 to 90 mV pH–1 over the incubation period. Initially, therefore, O2 concentration must have been increased during the day by algal photosynthesis (values <59 mV pH–1), but later O2 concentration must have fallen, due possibly to the decomposition of algal cells. The presence of algae initially increased the depth of the aerobic soil layer, but eventually an algal mat settled on the soil surface acting as a zone of O2 demand as the algae decomposed. Received: 7 July 1997  相似文献   

8.
The objective of this study was to evaluate plant-available N pools and the role of N management index (NMI) in the surface (0–20 cm) of a fluvo-aquic soil after 18 years of fertilization treatments under a wheat–maize cropping system in the North China Plain. The experiment included seven treatments: (1) NPK, balanced application of chemical fertilizer NPK; (2) OM, application of organic manure; (3) 1/2OMN, application of half organic manure plus chemical fertilizer NPK; (4) NP, application of chemical fertilizer NP; (5) PK, application of chemical fertilizer PK; (6) NK, application of chemical fertilizer NK; and (7) CK, unfertilized control. Total organic N (TON), microbial biomass N (MBN), labile N (LN), inorganic N (ION, including ammonium (NH4+)–N and nitrate (NO3−)–N) contents, net ammonification rate (NAR), net nitrification rate (NNR), net N mineralization rate (NNMR), and NMI in the fertilized treatments were higher than in the unfertilized treatment. Application of chemical fertilizer N (NPK, NP, and NK) increased ION in soils, compared with application of organic N or control. Nitrate N prevailed over exchangeable NH4+–N in all treatments. Nitrogen storage of the OM- and 1/2OMN-treated soils increased by 50.0% and 24.3%, respectively, over the NPK-treated soil, which had 5.4–22.5% more N than NP-, PK-, and NK-treated soils. The MBN, LN, and ION accounted for 1.7–2.4%, 25.7–34.2%, and 1.4–2.9% of TON, respectively, in different fertilization treatments. The surface soils (0–20-cm layer) in all treatments mineralized 43.6–152.9 kg N ha–1 year–1 for crop growth. Microbial biomass N was probably the better predictor of N mineralization, as it was correlated significantly (P < 0.01) with NNMR. The OM and 1/2OMN treatments were not an optimal option for farmers when the crop yield and labor cost were taken into consideration but an optimal option for increasing soil N supply capacity and N sequestration in soil. The NPK treatment showed the highest crop yields and increased soil N fractions through crop residues and exudates input, and thus, it may be considered as a sustainable system in the North China Plain.  相似文献   

9.
氨挥发是稻田氮素损失的一个重要途径,有效控制稻田氨挥发对水稻增产减排具有重要意义。界面阻隔材料具有环境友好性和低成本的特点,可以作为一种截然不同的氨挥发减排方法。本研究比较分析了3种界面阻隔材料对水稻产量、氮肥利用率和氨挥发排放的影响,以期为水稻降本增效及减少环境污染提供技术支持。通过在稻田喷施表面分子膜材料和覆盖稻糠,比较了两种表面分子膜材料——聚乳酸(PLA)和卵磷脂(LEC)及稻糠(RB)施用后水稻产量及其构成、稻田田面水pH和铵态氮及硝态氮含量动态、稻田氨挥发及氮肥吸收利用的变化特征。结果表明, 3种界面阻隔材料均显著增加了水稻产量,与常规施肥对照(CKU,无添加界面阻隔材料)相比增幅分别为13.0%(RB)、21.0%(PLA)和24.1%(LEC)。增产主要是因为有效穗数的增加,其中RB和PLA处理与CKU处理差异达显著水平;每穗粒数和结实率均无显著差异。LEC处理显著提高了氮肥利用率(19.0%),但RB处理氮肥利用率显著低于CKU。与CKU处理相比,3种界面阻隔材料的添加减少12.3%～19.9%的氨挥发量。PLA处理氨挥发减排效果最佳,达显著水平;其次为LEC处理。氨挥发减排可能与界面阻隔材料添加导致的田面水pH、铵态氮浓度变化和土壤铵态氮含量的增加有关。与CKU处理相比,所有处理均增加了田面水铵态氮浓度,但同时降低了田面水pH,且在水稻分蘖期影响较明显。其中PLA处理还提高了土壤铵态氮含量。本研究表明,稻田施加界面阻隔材料是稻田氨挥发减排以及增产增效的另一种可行的技术途径。  相似文献   

10.
Excessive nitrogen (N) fertilizer input leads to higher N loss via ammonia (NH3) volatilization. Controlled‐release urea (CRU) was expected to reduce emission losses of N. An incubation and a plant growth experiment with Gossypium hirsutum L. were conducted with urea and CRU (a fertilizer mixture of polymer‐coating sulfur‐coated urea and polymer‐coated urea with N ratios of 5 : 5) under six levels of N fertilization rates, which were 0% (0 mg N kg−1 soil), 50% (110 mg N kg−1 soil), 75% (165 mg N kg−1 soil), 100% (220 mg N kg−1 soil), 125% (275 mg N kg−1 soil), and 150% (330 mg N kg−1 soil) of the recommended N fertilizer rate. For each type of N fertilizer, the NH3 volatilization, cotton yield, and N uptake increased with the rate of N application, while N use efficiency reached a threshold and decreased when N application rates of urea and CRU exceeded 238.7 and 209.3 mg N kg−1 soil, respectively. Ammonia volatilization was reduced by 65–105% with CRU in comparison to urea treatments. The N release characteristic of CRU corresponded well to the N requirements of cotton growth. Soil inorganic N contents, leaf SPAD values, and net photosynthetic rates were increased by CRU application, particularly from the full bloom stage to the initial boll‐opening stage. As a result, CRU treatments achieved significantly higher lint yield by 7–30%, and the N use efficiency of CRU treatments was increased by 25–124% relative to that of urea treatments. These results suggest that the application of CRU could be widely used for cotton production with higher N use efficiency and lower NH3 volatilization.  相似文献   

11.
Yang  Qinglong  Liu  Peng  Dong  Shuting  Zhang  Jiwang  Zhao  Bin 《Journal of Soils and Sediments》2019,19(5):2200-2211
Purpose

In this study, we analyzed the effects of different maize varieties with nitrogen utilization efficiency, fertilizer type, and rate on the ammonia volatilization emission of farmland. Aimed to seek the best matching method to improve grain yield and fertilizer utilization efficiency of summer maize simultaneously.

Materials and methods

In field experiments, we choose two maize varieties with different nitrogen utilization efficiency (Zhengdan958, Z and Lainong14, L) as material. Set four different fertilizer treatments (200 kg N hm?2 inorganic fertilizer (U1), 100 kg N hm?2 inorganic fertilizer (U2), 200 kg N hm?2 organic fertilizer (M1), and 100 kg N hm?2 organic fertilizer (M2) to study their effect on NH3 emission and loss, maize grain yield, and nitrogen accumulation.

Results and discussion

Ammonia volatilization accounted for 8.61–21.68% of applied N. Under the same variety, ammonia volatilization accumulation after fertilization was as follows: U1 > U2 > M1 > M2. Ammonia volatilization rates increased first and then gradually decreased after the fertilization. The ammonia volatilization loss and cumulative loss increased due to increased nitrogen fertilizer application rate. The average nitrogen accumulation and harvest index of 200 kg N hm?2 N treatments were higher than 100 kg N hm?2 N treatments, and the difference between the inorganic fertilizer and organic fertilizer was not significant. In 2016 and 2017, the average yield of Zhengdan958 was 11,758.79 kg hm?2, which was 15.78% higher than that of Lainong14, and the difference between the two fertilizer types was not significant. The average yield of 200 kg N hm?2 N treatment was 11,959.42 kg hm?2, which was 20.13% higher than those of 100 kg N hm?2 N treatment.

Conclusions

By changing the type of fertilizer, replacing chemical fertilizers with organic fertilizer can reduce the loss of ammonia volatilization and promote the synergistic improvement to yield and resource utilization efficiency. Among them, using nitrogen-efficient varieties and using organic fertilizer instead of chemical fertilizer was beneficial to reduce the loss of ammonia volatilization, increase the accumulation of nitrogen, and promote the growth of maize to obtain high yield.

  相似文献   

12.
Maximizing nitrogen use efficiency (NUE) involves synchronizing the interplay between nitrogen preferential crops and the nitrogen transformation pathways of soil. Biochar may benefit specific N-preference crops in relatively unsuitable soil environments; however, experimental data are lacking. This study tested eight treatments, consisting of four nitrogen treatments (N0 = control; N1 = NH4Cl; N2 = NaNO3; and N3 = 1:1 ratio of NH4+ and NO3−) each with biochar applied at 0% or 2% (w/w). The results show that biochar and/or nitrogen application enhanced maize seedling biomass and NO3−-based fertilizer resulted in higher seedling biomass than NH4+-based fertilizer. With the application of biochar and NH4+-based fertilizer, maize seedling biomass increased and soil NH4+-N content was significantly reduced compared with NH4Cl sole application. Correlation analysis and redundancy analysis revealed that SOC content and inorganic nitrogen content were the main factors influencing maize growth and N absorption. Biochar with or without nitrogen fertilizer (except N1 treatment) significantly increased β-1,4-glucosidase (BG) activity. Co-application treatments also resulted in higher vector length, an indicator of C limitation—the increment might add to the risk of microbial C limitation. The activity of ammonia monooxygenase (AMO), a key enzyme in nitrification, decreased with the co-application of biochar and nitrogen, suggesting the alteration of nitrogen transformation.  相似文献   

13.
Denitrification has long been considered a major mechanism of N loss when N fertilizer is applied to flooded rice paddies. However, the direct determination of denitrification in soils is almost impossible because of the high atmospheric background of dinitrogen (N2). Dissolved N2 in a small water sample can be rapidly and precisely measured through membrane inlet mass spectrometry (MIMS). This study is the first to directly measure N2 flux through MIMS in flooded rice paddy plots that received different amounts of urea. Ammonia (NH3) volatilization was measured simultaneously to verify whether NH3 volatilization and denitrification are complementary loss mechanisms. The average cumulative N2–N loss measured by MIMS 21 days after fertilization was 4.7?±?1.7 % of the applied N, which was within the range of the reported values obtained by cumulative recovery of (N2 + N2O)–15N and 15N-balance technique. Underestimation or overestimation of denitrification can be prevented in MIMS given that N2 can be measured directly without 15N-labeled fertilizer. A good positive correlation was found between the dissolved in situ N2 concentrations of floodwater and the denitrification rates of intact soil cores. Urea incorporation reduced NH3 volatilization unlike surface broadcasting. However, urea incorporation significantly increased cumulative N2–N loss during the 21 days after fertilization. Correlation analysis showed that nitrate (NO3 ?–N) concentration in floodwater could be the primary restricting factor for soil denitrification in the experimental field. Results suggest that MIMS is a promising technique for the measurement of denitrification in a flooded rice paddy.  相似文献   

14.
This study determined N uptake by serrano chilli pepper for two years and evaluated the effects of biochar amendment or organic N (org-N) fertilizer on N use under a Mediterranean climate. A field experiment was conducted using microplots from 2016 to 2017 in California, USA. Treatments included biochar amendment rates [0 (control), 10, 30 and 50 tons (t) ha−1] biochar, all with 100% inorganic N fertilizer (165 kg N ha−1), and org-N fertilizer applications at 50%, 75% and 100% of the total available N supply. Pepper yield, vegetative biomass, N uptake, ammonia (NH3) volatilization and changes in soil organic carbon (SOC), and nitrate were determined. Pepper yield was highest in the 50% org-N and lowest in the 50 t ha−1 biochar treatment during the first year. There were no differences in fruit yield among the organic treatments during the second year, and all were higher than that from the control. The 100% org-N treatment had less NH3 volatilization than all other treatments during the first year. The two-year results showed that chilli pepper plants sequestered 4.6‒6.1 kg N to produce one ton fresh pepper fruits. During the first year, the 50% org-N treatment resulted in the highest N productivity or yield with lowest projected N fertilizer application requirements as compared to other treatments although there were no differences among all treatments in the second year. Thus, a combination of inorganic and org-N fertilizers can be an effective strategy to improve soil N productivity in long-term management.  相似文献   

15.
氨挥发是稻田氮素损失的主要途径之一,探究稻田生态种养模式对稻田土壤氨挥发产生的影响,可为该模式的生态环境效益评价提供理论依据。为评估稻蛙共作模式对水稻-紫云英轮作系统氨挥发的影响,通过开展田间小区试验,采用密闭式间歇抽气法采集氨气,对水稻-紫云英轮作系统的土壤氨挥发及其影响因素进行研究。试验共设置3个处理:空白对照(CK,不施肥,不放蛙)、常规水稻种植模式(CR,施化肥,不放蛙)、稻蛙共作模式(RF,施化肥,放蛙)。结果表明:稻蛙共作模式水稻季氨挥发累积量为47.02kg·hm~(-2),占当季施氮量12.9%;其后茬紫云英季的氨挥发累积量为16.27kg·hm~(-2);全年轮作系统的氨挥发累积量为63.29kg·hm~(-2),较常规水稻种植模式的氨挥发累积量降低15.3%。稻蛙共作模式全年水稻-紫云英轮作系统的氨挥发累积量占施氮量的比例为17.4%,显著低于常规水稻种植模式所占比例(20.5%)。水稻田面水的铵态氮浓度是影响水稻季氨挥发的主要因素,水稻田面水p H、水温、气温、风速等因素的影响次之,随温度上升,水稻田面水铵态氮浓度对氨挥发速率的影响逐渐增大。放蛙对水稻产量、水稻产量构成因素、氮肥利用效率及后茬作物紫云英产量的影响不显著。综上所述,稻蛙共作模式在水稻-紫云英轮作系统中具备一定的氨减排潜力,但该模式对稻田氨挥发影响的长期效应及其影响机理仍需进一步研究。  相似文献   

16.
Abstract

A commercially blended 7–2–11 fertilizer containing 27 g ? kg‐1 soluble ammoniacal nitrogen (NH4‐N) was evaluated for ammonia (NH3) volatilization and injury to leatherleaf fern (Rumohra adiantiformis) and an indicator plant, tomato (Lycopersicon esculentum). Closed system laboratory incubation studies on pH‐buffered sand medium indicated a very highly significant response (p≤0.001) of NH3 volatilization to sand pH. The greatest risk from NH3 emissions at pH 8.6 and 32°C appeared to be in the 5 to 70 hour period after fertilizer application. Gypsum (CaSO4) did not affect NH3 volatilization. Ammonium nitrate (NH4NO3) was identified as the main source of NH3 volatilization from this fertilizer formulation, while on an equal mass basis, ammonium sulphate [(NH4)2SO4] was more important. Both tomato and immature leatherleaf fern fronds were highly sensitive to volatilized NH3 from the fertilizer. A critical phytotoxic NH3(aq) concentration in sand solution of 0.14 mM was estimated for immature fern fronds. Mature fern fronds were significantly more tolerant of NH3 emissions, which may explain their observed resistance to NH3 injury in the field. Assessment of selected soil and irrigation water pH's from a leatherleaf fern growing area in Florida indicated a strong likelihood that volatilized NH3 injury to foliage can occur under field conditions.  相似文献   

17.
Fixation and defixation of ammonium in soils: a review   总被引：2，自引：0，他引：2  
Fixed NH4+ (NH4+ f) and fixation and defixation of NH4+ in soils have been the subject of a number of investigations with conflicting results. The results vary because of differences in methodology, soil type, mineralogical composition, and agro-climatic conditions. Most investigators have determined NH4+ f using strong oxidizing agents (KOBr or KOH) to remove organic N and the remaining NH4+ f does not necessarily reflect the fraction that is truly available to plants. The content of native NH4+ f in different soils is related to parent material, texture, clay content, clay mineral composition, potassium status of the soil and K saturation of the interlayers of 2:1 clay minerals, and moisture conditions. Evaluation of the literature shows that the NH4+ f-N content amounts to 10–90 mg kg−1 in coarse-textured soils (e.g., diluvial sand, red sandstone, granite), 60–270 mg kg−1 in medium-textured soils (loess, marsh, alluvial sediment, basalt) and 90–460 mg kg−1 in fine-textured soils (limestone, clay stone). Variable results on plant availability of NH4+ f are mainly due to the fact that some investigators distinguished between native and recently fixed NH4+ while others did not. Recently fixed NH4+ is available to plants to a greater degree than the native NH4+ f, and soil microflora play an important role in the defixation process. The temporal changes in the content of recently fixed NH4+ suggest that it is actively involved in N dynamics during a crop growth season. The amounts of NH4+ defixed during a growing season varied greatly within the groups of silty (20–200 kg NH4+-N ha−1 30 cm−1) as well as clayey (40–188 kg NH4+-N ha−1 30 cm−1) soils. The pool of recently fixed NH4+ may therefore be considered in fertilizer management programs for increasing N use efficiency and reducing N losses from soils.  相似文献   

18.
Simple and rapid chemical indices of soil nitrogen (N)-supplying capacity are necessary for fertilizer recommendations. In this study, pot experiment involving rice, anaerobic incubation, and chemical analysis were conducted for paddy soils collected from nine locations in the Taihu Lake region of China. The paddy soils showed large variability in N-supplying capacity as indicated by the total N uptake (TNU) by rice plants in a pot experiment, which ranged from 639.7 to 1,046.2 mg N pot−1 at maturity stage, representing 5.8% of the total soil N on average. Anaerobic incubation for 3, 14, 28, and 112 days all resulted in a significant (P < 0.01) correlation between cumulative mineral NH4+-N and TNU, but generally better correlations were obtained with increasing incubation time. Soil organic C, total soil N, microbial C, and ultraviolet absorbance of NaHCO3 extract at 205 and 260 nm revealed no clear relationship with TNU or cumulative mineral NH4+-N. Soil C/N ratio, acid KMnO4-NH4+-N, alkaline KMnO4-NH4+-N, phosphate–borate buffer extractable NH4+-N (PB-NH4+-N), phosphate–borate buffer hydrolyzable NH4+-N (PBHYDR-NH4+-N) and hot KCl extractable NH4+-N (HKCl−NH4+-N) were all significantly (P < 0.05) related to TNU and cumulative mineral NH4+-N of long-term incubation (>28 days). However, the best chemical index of soil N-supplying capacity was the soil C/N ratio, which showed the highest correlation with TNU at maturity stage (R = −0.929, P < 0.001) and cumulative mineral NH4+-N (R = −0.971, P < 0.001). Acid KMnO4-NH4+-N plus native soil NH4+-N produced similar, but slightly worse predictions of soil N-supplying capacity than the soil C/N ratio.  相似文献   

19.
Laboratory incubation study showed that iron pyrites retarded nitrification of urea-derived ammonium (NH4 +), the effect being greatest at the highest level (10000 mg kg–1 soil). Nitrification inhibition with 10000 mg pyrite kg–1 soil, at the end of 30 days, was 40.3% compared to 55.9% for dicyandiamide (DCD). The inhibitory effect with lower rates of pyrite (100–500 mg kg–1) lasted only up to 9 days. Urea+pyrite treatment was also found to have higher exchangeable NH4 +-N compared to urea alone. DCD-amended soils had the highest NH4 +-N content throughout. Pyrite-treated soils had about 7–86% lower ammonia volatilization losses than urea alone. Total NH3 loss was the most with urea+DCD (7.9% of applied N), about 9% more than with urea alone. Received: 11 November 1995  相似文献   

20.
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   

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