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1.
A pot experiment was conducted using a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments) amended with either citrus leaves or compost, to measure the nitrogen (N) mineralization and its availability to two citrus rootstock seedlings. A rapid increase in NH4‐N concentration was evident in the soil amended with citrus leaves as compared to compost during the initial 14 to 20 d. Subsequently, the concentration of NH4‐N decreased in the citrus leaves amended soil. The extractable NO3‐N concentration was greater in the soil amended with citrus leaves as compared to compost, throughout the 270 d duration of the study. The N concentrations and N uptake by Cleopatra mandarin (CM) and Swingle citrumelo (SC) seedlings grown in citrus leaf amended soil were very similar to those in urea amended soil. Therefore, mineralization of N from dry ground citrus leaves was quite rapid. The N concentrations in both rootstock seedlings were much lower in the compost amended and unamended soils as compared to those in either citrus leaves or urea amended soils. Rapid mineralization of N from cirrus leaves added to sandy soil, resulting in an increased availability of N, suggested that the contribution of N from shed leaf mineralization must be considered while developing N rate recommendations for improving N use efficiency.  相似文献   

2.
The capability to determine nitrogen availability of composts is necessary to ensure that such materials will provide sufficient fertilization to the growing crop and cause minimal environmental degradation. A greenhouse study using tall fescue as a bioindicator was used to evaluate nitrogen availability of two biosolids composts, two mixed yard waste-poultry manure composts, and one commercially-processed poultry litter. Five inorganic nitrogen (as NH4NO3-N) treatments applied at 0, 22.5, 45, 67.7, and 90 mg N/kg soil were employed to establish an N calibration curve. Yield, fescue biomass total nitrogen (as total Kjeldahl N (TKN)), and soil TKN and KCl extractable NO3?-N and NH4+-N concentrations of the organically amended treatments were compared to the inorganically fertilized treatments to determine amendment N mineralization rates and N fertilizer equivalent values (NFEV). Nitrogen mineralization rates were greatest in the poultry litter (21%) and Panorama yard waste compost (5%) amended pots. The NFEV of these amendments were 49% and 10%, respectively. Wolf Creek biosolids compost and Huck's Hen Blend yard waste compost immobilized N (?5% and 0.18%, respectively), and had percent NFEV of ?0.66% and 0.19%, respectively. Rivanna biosolids compost immobilized N (?15%), but the NFEV was 30% due to the relatively high inorganic N content in the amendment. Nitrogen mineralization and NFEV were generally greater in amendments with greater total N concentrations and lower C:N values. The total N concentration and C:N values were less reliable variables in predicting N mineralization and percent NFEV when a significant portion of the total N was in the inorganic form. Nitrogen equivalency value and N mineralization for each amendment increased with time of sampling, indicating the potential for early season N insufficiency to plants fertilized with compost due to lack of synchrony between N mineralization and plant N needs.  相似文献   

3.
Abstract

In the search for an approach which could be used to predict available nitrogen (N) in organic amendments, biological and chemical methods were investigated in laboratory and growth chamber studies. Two biological methods [maize plants (Zea mays L.) grown in pots, and soil‐amendment mixtures incubated aerobically at 2, 4, 6, 8, 12, and 16 weeks], and four chemical methods [autoclave, 0.5M potassium permanganate (KMnO4), pepsin, and 6M hydrochloric acid (HCl)] were compared to determine N availability in 36 organic amendments applied to soil. Total N mineralized in a soil amended with different organic amendments ranged from‐12 to 428 mg N/kg soil. The highest value was obtained from sludge number 11 and the lowest from cow manure 2, urban refuse, and grape‐marc. In general, the aerobically‐treated sewage sludges gave higher N‐mineralization rates than other amendments. The 6M HCl and autoclave methods were more suitable for predicting N availability in these organic amendments than either the pepsin or KMnO4 methods. Prediction of N availability in the growth chamber experiments improved if several chemical and biological methods were combined in a multiple regression analysis.  相似文献   

4.
Residues from some tree species may contain allelopathic chemicals that have the potential to inhibit plant growth and symbiotic N2-fixing microorganisms. Soybean [Glycine max (L.) Merr] was grown in pots to compare nodulation and N2-fixation responses of the following soil amendments: control soil, leaf compost, red oak (Quercus rubra L.) leaves, sugar maple (Acer saccharum Marsh) leaves, sycamore (Platanus occidentalis L.) leaves, black walnut (Juglans nigra L.) leaves, rye (Secale cereale L.) straw, and corn (Zea mays L.) stover. Freshly fallen leaves were collected from urban shade trees. Soil was amended with 20 g kg-1 air-dried, ground plant materials. Nodulating and nonnodulating isolines of Clark soybean were grown to the R2 stage to determine N2-fixation by the difference method. Although nodulation was not adversely affected, soybean grown on leaf-amended soil exhibited temporary N deficiency until nodulation. Nodule number was increased by more than 40% for soybean grown on amended soil, but nodule dry matter per plant generally was not changed compared with control soil. Nonnodulating plants were severely N deficient and stunted as a consequence of N immobilization. Nodulating soybean plants grown on leaf or crop residue amended soil were more dependent on symbiotically fixed N and had lower dry matter yields than the controls. When leaves were composted, the problem of N immobilization was avoided and dry matter yield was not reduced. No indication of an allelopathic inhibition on nodulation or N2-fixation from heavy application of oak, maple, sycamore, or walnut leaves to soil was observed.  相似文献   

5.
ABSTRACT

Effects of temperature and moisture on nitrogen (N) mineralization from organic amendments in high tunnel farming systems are rarely studied to assist N fertilizer management for high N-demand crops with short cycles. In this study, soils from a new high tunnel site were incubated at four temperatures (2, 10, 20, & 30°C) and five gravimetric water contents (15, 20, 25, 30, & 35%) with and without a dried and ground alfalfa amendment. Net N mineralization was determined by measuring NH4+-N and NO3–-N contents periodically over 84 days. Significant main effects of temperature and moisture were found (p < .0001) and tendencies of a significance of alfalfa amendment (p = .0855) and interaction between amendment and temperature (p = .0842) were observed. Only a significant increase of the net mineralized N at 30ºC in amended soil was observed compared to unamended soil (p = .0043). Estimated from the first-order exponential model, maximum potential mineralized N was 1.2 times greater while mineralization rate was up to 2.1 times greater in amended soil compare to un-amended soil. Q10 estimated from the Arrhenius model ranged from 1.62 to 2.04 in the amended soil and 1.66 to1.85 in the un-amended soil. The average optimal soil water content for maximum N mineralization estimated from the Gaussian function model was 33.8% in amended soil and 35.9% in un-amended soil. The results from this study can be used to suggest soil moisture and temperature management strategies to control N availability in high tunnel systems.  相似文献   

6.
The mineralization and availability of cover crop N to the succeeding crop are critical components in the management of soil N to reduce N leaching. The effects of several leguminous and non-leguminous cover crops on soil N availability, N mineralization potential, and corn (Zea mays L.) yield were examined. The cover crops had variable effects on soil N availability and corn yield and N uptake. Because of the rapid mineralization of the cover crops following incorporation, the inorganic N levels in the soil sampled in mid-May 1992 (4 weeks after incorporation of cover crops), rather than the potentially mineralizable N, rate constants, initial potential mineralization rate, or cumulative N mineralized over 14 weeks, correlated well with N concentrations, C:N ratios, or the N added in the cover crops. However, the inclusion of potentially mineralizable N with inorganic N in a multiple regression improved the variability in the corn yield and the N uptake accounted for. Since extensive mineralization had occurred before the 21 May sampling, the potentially mineralizable N was affected more by the soil organic N and C than by the N concentrations of the cover crops. The presidedress NO3 --N test levels were well predicted by the inorganic and potentially mineralizable N (R 2=0.89, P<0.01), although the test levels were better in predicting corn yield and N uptake. If the available soil N test needs to be made earlier than recommended by the presidedress NO3 --N test, both inorganic and potentially mineralizable N are needed to better predict the corn yield and N uptake in the soils.  相似文献   

7.
Olive pulp (OP), the residual material of a two-phase olive oil extraction system, and effluents from hydrogen (EH2) and methane (ECH4) production, have been evaluated as soil amendments particularly for their impact on soil mineral nitrogen (N) dynamics, gross N mineralization, and soil microbial biomass N (Nmic). Both N transformation and microbial growth were mainly influenced by the amount and quality of added organic carbon (C). Both OP and EH2, which contain more carbohydrates and lipids than polyphenolic compounds, stimulated NO3 − immobilization during the early incubation period and increased Nmic, saprophytic fungi, and N mineralization. On the contrary, soil amended with ECH4, which is characterized by the lowest C content but the highest content of polyphenolic compounds, behaved as the control; neither NO3 − immobilization nor microbial growth were observed and gross N mineralization was stimulated only at the beginning of the incubation period. Bacterial plate count was significantly correlated with direct bacterial count and fungal count was correlated with Nmic. Therefore, it is suggested that both bacterial and fungal plate counts may be used as indicators of the overall bacterial and fungal populations inhabiting soil, respectively. The knowledge of the impact of these materials on soil N dynamics is crucial for their correct use in agriculture because it has been shown that NO3 − availability can be strongly influenced by the addition of different amounts and quality of organic amendment.  相似文献   

8.
The process of biomass, nitrogen (N), and potassium (K) accumulation over time as affected by N forms is poorly understood. The objective of this study was to identify the effects of N form on growth as well as on N and K nutrition of flue‐cured tobacco plants (Nicotiana tobaccum L.). The plants were grown in a greenhouse with pots of soil for 117 days after 200 days of preculture. Three treatments (calcium nitrate [Ca(NO3)2], ammonium nitrate (NH4NO3), and ammonium nitrate plus straw (NH4NO3 + straw)) were used. The results showed that there were no significant differences in shoot dry mass of tobacco among the three treatments during the entire growth stage except at 30 and 117 days after transplanting. At these two growth stages, shoot biomass with the Ca(NO3)2 treatment was significantly less than that with NH4NO3 with or without straw. The NH4NO3 + straw plants had more mature leaves and greater leaf dry weight than the other two treatments. At an early stage (before 66 days), N concentration of Ca(NO3)2‐fed plants was less than with the other two treatments. The leaf K concentration and shoot K content of NH4NO3 and NH4NO3 + straw plants were more than with the Ca(NO3)2 treatment before maturity. Also, K concentration in mature leaves with these two treatments was greater than with Ca(NO3)2 treatment. All these results indicated that NH4NO3 application had benefits to the maturity and K accumulation in leaves of tobacco.  相似文献   

9.
《Applied soil ecology》2009,42(3):351-359
Beringite (B) and zerovalent iron grit (Z), singly and in combination (BZ), were added to a loamy sand soil contaminated by trace elements (Reppel, Belgium), mainly by arsenic (As), to reduce As labile fractions and phytoavailability. An uncontaminated sandy soil was studied for comparison. Soils were placed in large lysimeters cultivated with maize and vegetables for 6 years. pH, organic C and total N content increased in amended soils. The Z and BZ treatments reduced the Ca(NO3)2− extractable soil As and As uptake by lettuce. The BZ lettuces had also the lowest foliar Pb, Cd, Zn, and Mn concentrations. All amendments had positive effects on the soil microbial biomass and reduced the qCO2. Glucose mineralization was increased in Z and BZ amended soils. Acid phosphomonoesterase activity was higher in the untreated soil than in the other soils; the alkaline phosphomonoesterase, phosphodiesterase and protease activities were increased by Z and BZ treatments, whereas B amendment had less positive effects. Genetic fingerprinting using Denaturing Gradient Gel Electrophoresis (DGGE) revealed shifts in the composition of eubacterial and fungal communities of the amended soils. Microbial species richness decreased rather than increased in the treated soils, regardless of reduced trace element availability and increased soil microbial biomass and activity.  相似文献   

10.
The use of composted municipal refuse on agricultural land requires prior knowledge of the interactions among compost, soil, and plants. Research into the availability of N in highly matured municipal refuse compost is particularly important considering the current concern about groundwater contamination by NO inf3 sup- -N. A greenhouse pot bioassay was conducted to determine the percentage of short-term apparent bioavailable N of a highly matured refuse compost and its relative efficiency in supplying inorganic N to the soil-plant system in comparison with NH4NO3. Municipal refuse (after 165 days of composting) was applied at rates equivalent to 10, 20, 30, 40, and 50 t ha-1 to a ferrallitic soil from Tenerife Island (Andeptic Paludult). NH4NO3 was applied at rates equivalent to the total N content of the compost treatments. Perennial ryegrass (Lolium perenne L.) was grown in 3-kg pots and the tops were harvested at regular intervals after seedling emergence. The compost increased dry matter yield, soil mineral N, and plant N uptake proportional to the applied rate. These increases were significantly higher than the control at an application rate of 20 t ha-1. After 6 months the apparent bioavailable N ranged from 16 to 21%. The relative efficiency was 43% after 30 days. This suggests that large inputs of inorganic N into soil can be obtained with high rates of this kind of compost, with a potential for NO inf3 sup- -N contamination. However, applied at moderate rates in our bioassay (<50 t ha-1), compost showed a low N-supplying capacity to ryegrass, i.e. a small fraction of the mineralized compost N was used by plants in the course of time. This was ascribed to a partial biological immobilization. This pattern of N availability in highly matured municipal refuse compost, positive net mineralization but partial immobilization, is similar to the pattern of N availability in biologically active soils and is therefore extremely interesting for the conservation of N in agro-ecosystems.  相似文献   

11.
The turnover of native and applied C and N in undisturbed soil samples of different texture but similar mineralogical composition, origin and cropping history was evaluated at −10 kPa water potential. Cores of structurally intact soil with 108, 224 and 337 g clay kg−1 were horizontially sliced and 15N-labelled sheep faeces was placed between the two halves of the intact core. The cores together with unamended treatments were incubated in the dark at 20 °C and the evolution of CO2-C determined continuously for 177 d. Inorganic and microbial biomass N and 15N were determined periodically. Net nitrification was less in soil amended with faeces compared with unamended soil. When adjusted for the NO3-N present in soil before faeces was applied, net nitrification became negative indicating that NO3-N had been immobilized or denitrified. The soil most rich in clay nitrified least N and 15N. The amounts of N retained in the microbial biomass in unamended soils increased with clay content. A maximum of 13% of the faeces 15N was recovered in the microbial biomass in the amended soils. CO2-C evolution increased with clay content in amended and unamended soils. CO2-C evolution from the most sandy soil was reduced due to a low content of potentially mineralizable native soil C whereas the rate constant of C mineralization rate peaked in this soil. When the pool of potentially mineralizable native soil C was assumed proportional to volumetric water content, the three soils contained similar proportions of potentially mineralizable native soil C but the rate constant of C mineralization remained highest in the soil with least clay. Thus although a similar availability of water in the three soils was ensured by their identical matric potential, the actual volume of water seemed to determine the proportion of total C that was potentially mineralizable. The proportion of mineralizable C in the faeces was similar in the three soils (70% of total C), again with a higher rate constant of C mineralization in the soil with least clay. It is hypothesized that the pool of potentially mineralizable C and C rate constants fluctuate with the soil water content.  相似文献   

12.
Abstract

The amount of organic‐N in a given soil is a result of the cumulative influences of factors affecting additions to and losses from the soil. Many of these factors also influence the rate of N mineralization and, thus, the quantity of available N for plants. Regression techniques were used with data gathered while field testing a soil N availability test for corn (Zea mays L.) to evaluate the influence of various factors on N availability and the rate of N mineralization. Both check plot (no N fertilizer) yields and soil test NO3‐N were related to total Kjeldahl N (TKN), drainage class, and manure application. The estimated rate of N mineralization decreased as TKN increased. Answers to a farmer questionnaire that accompanied samples submitted for soil testing also indicated the importance of soil characteristics and fresh organic residue decomposition to N availability. These findings suggest that soil tests based on TKN or parameters correlated with TKN will not successfully predict N availability for widely different soil types and management practices. The Magdoff Pre‐Sidedress Nitrate Test (PSNT), however, is able to assess the cumulative effects of the variety of factors that govern nitrogen availability in soils.  相似文献   

13.
We assessed the influence of the addition of four municipal or agricultural by-products (cotton gin waste, ground newsprint, woodchips, or yard trimmings), combined with two sources of nitrogen (N), [ammonium nitrate (NH4NO3) or poultry litter] as carbon (C) sources on active bacterial, active fungal and total microbial biomass, cellulose decomposition, potential net mineralization of soil C and N and soil nutrient status in agricultural soils. Cotton gin waste as a C source promoted the highest potential net N mineralization and N turnover. Municipal or agricultural by-products as C sources had no affect on active bacterial, active fungal or total microbial biomass, C turnover, or the ratio of net C:N mineralized. Organic by-products and N additions to soil did not consistently affect C turnover rates, active bacterial, active fungal or total microbial biomass. After 3, 6 or 9 weeks of laboratory incubation, soil amended with organic by-products plus poultry litter resulted in higher cellulose degradation rates than soil amended with organic by-products plus NH4NO3. Cellulose degradation was highest when soil was amended with newsprint plus poultry litter. When soil was amended with organic by-products plus NH4NO3, cellulose degradation did not differ from soil amended with only poultry litter or unamended soil. Soil amended with organic by-products had higher concentrations of soil C than soil amended with only poultry litter or unamended soil. Soil amended with organic by-products plus N as poultry litter generally, but not always, had higher extractable P, K, Ca, and Mg concentrations than soil amended with poultry litter or unamende soil. Agricultural soil amended with organic by-products and N had higher extractable N, P, K, Ca and Mg than unamended soil. Since cotton gin waste plus poultry litter resulted in higher cellulose degradation and net N mineralization, its use may result in faster increase in soil nutrient status than the other organic by-products and N sources that were tested. Received: 15 May 1996  相似文献   

14.
Abstract

Spinach was grown in the greenhouse in soil with the pH adjusted to 5.0, 5.5, 6.0, 6.5, and 7.0, N fertilizer rates of 0, 50 and 200 mg N/Kg soil, and Mo fertilizer rates of 0, 0.3 and 1.2 mg Mo/Kg soil. The NO3‐N concentration of the tissue increased with fertilizer N or a rise in pH from 5.0 to 7.0. The addition of Mo at either rate reduced the NO3 concentration of spinach grown at pH 5.0 and 5.5 but had no effect on plants grown at pH 6.5 or 7.0. At pH 6.0 the 1.2 mg Mo/Kg soil rate was effective at the 50 and 200 mg N/Kg soil fertilizer rates but had no effect on spinach grown without a N application. At the same pH, the 0.3 mg Mo/Kg soil rate had no effect on NO3 content of spinach grown with the 50 mg N/Kg rate but did reduce the NO3 content of spinach grown without N added or with the 200 mg N/Kg soil. The 1.2 mg Mo/Kg soil rate was more effective than 0.3 mg Mo/Kg rate in reducing NO3 content of spinach grown with 200 mg N/Kg soil at pH 5.0–6.5 inclusive but gave variable results when no N or 50 mg N/Kg soil was added. Molybdenum did not affect the total N or NO2 concentrations of the plants.  相似文献   

15.
Predicting nitrogen (N) mineralization has been one of the greatest challenges to improving N management in agriculture. A laboratory incubation experiment was conducted to study the N mineralization of soil amended with rock phosphate (RP)-enriched composts. The RP-enriched rice straw compost amended soil mineralized highest N as compared to compost prepared from mustard stover and tree leaves. The first-order model was found to be the most suitable for N because it provided the best fit to the experimental data and for its simplicity. The model predicted that potentially mineralized N (N0) was varied from 4.0 to 52.1 mg kg?1 and the mineralization rate k varied from 0.015 to 0.066 day?1. The rice straw compost amended soil had higher N0 value than mustard stover and tree leaves compost amended soil. This study demonstrated the importance of application of rock phosphate-enriched composts in improving N supplying capacity of soil.  相似文献   

16.
Abstract

Nitrapyrin, terrazole and simazine were evaluated as chemical inhibitors of biological nitrification and denitrification. Corn (Zea mays L. cv. Hybrid Pioneer 3343) was grown in 60‐liter pots filled with a 50/50 (V/V) sand/Cecil clay mixture. Chemical treatments consisted of weekly applications of 0.25 ppm nitrapyrin, terrazole and/or simazine concurrently with 20 ppm N as either (NH4)2SO4 or Ca(NO3)2 for 9 weeks. Thereafter, only N (20 ppm per pot) was applied to the media every three days for 4 weeks. Nitrapyrin, terrazole and simazine reduced nitrification resulting in both higher total plant N and residual soil NH4 content relative to the control plants and soil. Plant growth was reduced by the inhibitory effects of the chemicals on nitrification and subsequent NH4 accumulation in the medium. All chemicals reduced denitrification with terrazole being more effective than nitrapyrin as reflected by higher N contents of plants and residual soil NO3‐N. Nitrapyrin and/or terrazole applied with Ca(NO3)2 increased plant biomass, but simazine, by inducing higher N02 concentration in the plant tissues, sharply reduced plant growth relative to the other treatments. When simazine was part of the chemical treatment, its effects on plant growth and total N contents generally outweighed or masked those of nitrapyrin or terrazole.  相似文献   

17.
Field observations have shown that a substantial portion of peanut leaves abscise in windrows during pod curing, leading to an uneven distribution of leaves and stems when intact residues are spread during harvest. Possible differences in nitrogen (N) mineralization rates between peanut leaf and stem residues may lead to spatial and temporal variability in available N during subsequent crops. The objective of this study was to quantify N mineralization in soil amended with different peanut residue components under simulated conventional and conservation tillage practices. A 252-day microlysimeter incubation was conducted in which peanut leaves, stems and a 1:1 mixture of leaves:stems from three varieties were incorporated or placed on the soil surface to simulate conventional or conservation tillage, respectively. Soils were periodically leached to assess N mineralization compared with a soil-only control. Nitrogen mineralization was only affected by residue component. Averaged over variety and residue placement, soil amended with leaves mineralized 10% more N relative to the control or soil containing stems. It was estimated that leaves supplied 25 kg N ha−1 over 252 days at 0–15 cm soil depth, which would likely be insufficient to induce a yield response by a subsequent crop. This study suggests that uneven distribution of peanut leaf and stem residues following harvest causes only minor spatial and temporal variability in available N during subsequent crop growth. These results support the growing body of evidence indicating that peanut residue N contributions to subsequent crops are negligible in the peanut basin of the south-eastern USA.  相似文献   

18.
Previous studies have indicated that under hydroponic conditions, spring wheat (Triticum aestivum) plants produce higher grain yields, more tillers, and increased dry matter when continuously supplied with mixtures of NO3 and NH4 than when supplied with only NO3. The objective of this study was to determine if mixed N needs to be available before or after flowering, or continuously, in order to elicit increases in growth and yield of wheat. During vegetative development, plants of the cultivar ‘Marshal’ were grown in one of two nutrient solutions containing either a 100/0 or 50/50 mixture of NO3 to NH4 and, after flowering, half the plants were switched to the other solution. At physiological maturity, plants were harvested, separated into leaves, stems, roots, and grain and the dry matter and N concentration of each part determined. Yield components and the number of productive tillers were also determined. Availability of mixed N at either growth stage increased grain yield over plants receiving continuous NO3, but the increase was twice as large when the mixture was present during vegetative growth. When the N mixture was available only during vegetative growth the yield increase was similar to that obtained with continuous mixed N. The yield increases obtained with mixed N were the result of enhanced tillering and the production of more total biomass. Although plants receiving a mixed N treatment accumulated more total N than those grown solely with NO3, the greatest increase occurred when mixed N was available during vegetative growth. Because availability of mixed N after flowering increased the N concentration over all NO3 and pre‐flowering mixed N plants, it appears that the additional N accumulation from mixed N needs to be coupled with tiller development in order to enhance grain yields. These results confirm that mixed N nutrition increases yield of wheat and indicate that the most critical growth stage to supply the N mixture to the plant is during vegetative growth.  相似文献   

19.
Abstract

In a pot experiment, the effects of NO3‐N and NH4‐N fertilizer were examined on the pH of the bulk soil and rhizosphere, and on the growth and nutrient uptake of 18–35‐d old bean plants (Phaseolus vulgaris L.) supplied with KH2PO4 or rock phosphate (Hyperphos). Prior to sowing, the soil was incubated for 16 d to ensure complete nitrification of NH4‐N which decreased bulk soil pH from 6.8 to 5.5. In other pots, a nitrification inhibitor, N‐Serve, was added together with the ammonium fertilizer and after 18 d growth, the pH of the bulk soil was 6.6 while the pH of the rhizosphere decreased to 4.5. Shoot and root dry matter yield was significally greater for plants supplied with KH2PO4 and fertilized with NH4‐N compared with NO3‐N. This increased growth by NH4‐N fed plants was presumably due to a increased nutrient availability caused by the acidification of the bulk soil. Shoot concentrations of ? and micronutrients, such as Fe, Mn, Zn, and Cu, were higher for plants supplied with NH4‐N, and more strikingly were higher for plats supplied with NH4‐N+N‐Serve when expressed on a root length basis. In this latter case, the increased nutrient acquisition by plants could only be due to acidification of the rhizopshere. The inhibitory effect of NH4‐N+N‐Serve, particularly on root growth, was not caused by NH4+ toxicity, but was due to a direct effect of N‐Serve as shown by growth comparisons with another nitrification inhibitor, dicyanodiamide (DCD).  相似文献   

20.
Mineral‐N production by air‐dried biosolids was measured in an Australian tenosol type soil with two moisture conditions over 70 days, using a controlled laboratory incubation procedure. The biosolids were from both air‐drying pans and stockpiles. Inorganic‐N components (NH4‐N, NO3‐N and NO2‐N) were present in all biosolids, with higher concentrations in samples from air‐drying pans compared with stockpiles of 1 yr age. Nevertheless, significant production of NO3‐N occurred in moist soil amended with all air‐dried biosolids. In contrast, saturated soil amended with air‐dried biosolids generally showed a net loss of inorganic‐N compounds during incubation, presumably owing to denitrification. In the saturated soil, only biosolids from air‐drying pans provided NO3‐N production from existing NH4‐N. The results indicated that biosolids from air‐drying pans provided the most robust production of NO3‐N, compared with aged material from the stockpiles, owing to the reduced N content and increased stability of the organic fraction in stored biosolids. However, the rates of N‐mineralization in the tenosol soil were substantially lower than reported for more fertile soil types and most of the organic‐N content of the biosolids remained undegraded by day 70. The biosolids thus may substantially remain to provide improved properties of soil, such as structure and water‐holding capacity. The results suggest that anaerobically digested biosolids from air‐drying pans are potentially highly consistent products that could be effective replacements for inorganic‐N fertilizer in agricultural production.  相似文献   

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