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1.
Using saturated or enriched zeolites as slow release fertilizers (SRFs) is considered as an environmental-friendly strategy to enhance use of macronutrients in sandy soils. In this paper, two natural zeolites, clinoptilolite (CLI) and chabazite (CHA) were used as mineral precursors to prepare NH4+/K+ saturated clinoptilolite (NH4+/K+-CLI) and chabazite (NH4+/K+-CHA) as zeolitic nutrient sources (ZNSs). Comparison between the nutrient retention capabilities of these ZNSs was one of the main objectives of this study. The NH4+/K+-CLI and NH4+/K+-CHA were prepared by soaking the zeolites in NH4Cl and KCl solutions, respectively. Leaching tests were performed on a sandy soil amended with chemical fertilizers (CFs), NH4+/K+-CLI and NH4+/K+-CHA to evaluate the leaching properties of them. The results indicated that approximately 84% and 88% of the NH4+ and K+ of soils fertilized with CFs were lost during the experiment, respectively. While, the NH4+ and K+ losses from soils amended with NH4+/K+-CLI and NH4+/K+-CHA were 29%, 23%, and 14%, 24%, respectively. Despite of drastic changes in leaching behavior of CFs, nutrient losses from ZNSs were more uniform during the experiments. No significant difference was found between the two studied zeolites on reduction of K+ loss. However, CHA was more effective in preventing NH4+ loss during leaching.  相似文献   

2.
Leaching of nutrients in soil can change the surface and groundwater quality. The present study aimed at investigating the effects of raw and ammonium (NH4+)-enriched zeolite on nitrogen leaching and wheat yields in sandy loam and clay loam soils. The treatments were one level of nitrogen; Z0: (100 kg (N) ha?1) as urea, two levels of raw zeolite; Z1:(0.5 g kg?1 + 100 kg ha?1) and Z2: (1 g kg?1 + 100 kg ha?1), and two levels of NH4+-enriched zeolite; Z3: (0.5 g kg?1 + 80 kg ha?1) and Z4: (1 g kg?1 + 60 kg ha?1). Wheat grains were sown in pots and, after each irrigation event, the leachates were collected and their nitrate (NO3?) and NH4+ contents were determined. The grain yield and the total N in plants were measured after four months of wheat growth. The results indicated that the amounts of NH4+ and NO3? leached from the sandy loam soil were more than those from the clay loam soil in all irrigation events. The maximum and minimum concentrations of nitrogen in the drainage water for both soils were observed at control and NH4+-zeolite treatments, respectively. Total N in the plants grown in the sandy loam was higher compared to plants grown in clay loam soil. Also, nitrogen uptake by plants in control and NH4+-zeolite was higher than that of raw-zeolite treatments. The decrease in the amount of N leaching in the presence of NH4+-zeolite caused more N availability for plants and increased the efficiency of nitrogen fertilizers and the plants yield.  相似文献   

3.
The objectives of this article were to analyze the evolution of the nutrient parameters of the leachates collected from Syngonium podophyllum var. Silver plants cultivated for 20 weeks in a buried greenhouse with four methods of fertilization. The treatments were T1, standard liquid feeding (SLF) [7.0 mmol L?1 nitrate (NO3 ?) nitrogen (N), 0.3 mmol L?1 phosphorus (P), and 3.5 mmol L?1 potassium (K)] after transplanting; T2, liquid feeding soluble fertilizer (LFSF) [6.9% NO3 ? N, 11.1% ammonium (NH4 +) N stabilized by 3,4-dimethylpyrazole phosphate, 8.0% P2O5, and 14.0% K2O] after transplanting; T3, controlled release fertilizer (CRF I) (7.4% NO3 ? N, 8.6% NH4 + N, 8.0% P2O5, and 12.0% K2O) applied before planting and half concentration of SLF from 45 days after transplanting; and T4, controlled release fertilizer (CRF II) (8.5% NO3 ? N, 7.5% NH4 + N, 8.0% P2O5, and 12.0% K2O) applied before planting and half concentration of SLF from 45 days after transplanting. Solution pH, electrical conductivity (EC), NO3 ? N, NH4 + N, K, and P concentrations in the leachate were analyzed weekly. Plant quality was assessed at the end of the trial through objective and subjective parameters. Significant differences among the different fertilization methods were observed. CRF treatments resulted in the greatest nutrient leachate concentration during the first 6 weeks of the study, and afterward it decreased gradually until the end of the cultivation. CRF I showed greater leachate concentrations of N, P, and K than the others during the first half of the study. The concentrations of NO3 ? N and P from all the fertilizer types were often above the permissible levels cited in the federal Clean Water Act. The best-quality plants were obtained with CRF II, whereas the greatest height and Aerial Dry Weight (ADW) were obtained with CRF treatments and the greatest Root Dry Weight (RDW) was obtained with the NH4 + N treatments.  相似文献   

4.
Abstract

This trial was carried out to establish an appropriate nutrient solution for Aglaonema commutatum and to investigate the nutritional effects generated by modifications in the solution. Six treatments were tested: control (T0; pH 6.5, E.C. 1.5 dS m?1, 6 mmol L?1 NO3 ?‐N, and 6 mmol L?1 K+); high nitrogen (N) level (T1; 9 mmol L?1 6:3 NO3 ?–NH4 +); N form (T2; 6 mmol L?1 N‐NH4 +); high K+ level (T3; 12 mmol L?1 K+); high electrical conductivity (T4; E.C. 4 dS m?1, 25 mmol L?1 NaCl), and basic pH (T5; pH 8). At the end of the cultivation, leaf, shoot, and root dry weights and elemental concentrations were determined. Nutrient contents and total plant uptake were calculated from the dry weights and nutrient concentrations. Plant K+ uptake increased with application of K+ or basic nutrient solution. The uptake and transport of calcium (Ca) were enhanced by the use of NO3 ?‐N and inhibited by the presence of other cations in the medium (NH4 +, K+, Na+) and by basic pH. Magnesium (Mg) uptake increased with NO3 ?‐N application and with pH. Sodium (Na) uptake was the highest in the saline treatment (T4), followed by the basic pH treatment. Sodium accumulation was detected in the roots (natrophobic plant), where the plant generated a physiological barrier to avoid damage. Dry weight did not differ significantly (p<0.05) among treatments except in the NaCl treatment. These results may help in the formulation of nutrient solutions that take into account the ionic composition of irrigation water and the physiological requirements of plants.  相似文献   

5.
Accurate estimation of the available potassium (K+) supplied by calcareous soils in arid and semi‐arid regions is becoming more important. Exchangeable K+, determined by ammonium acetate (NH4OAc), might not be the best predictor of the soil K+ available to crops in soils containing micaceous minerals. The effectiveness of different extraction methods for the prediction of K‐supplying capacities and quantity–intensity relationships was studied in 10 calcareous soils in western Iran. Total K+ uptake by wheat grown in the greenhouse was used to measure plant‐available soil K+. The following methods extracted increasingly higher average amounts of soil K+: 0.025 M H2SO4 (45 mg K+ kg?1), 1 M NaCl (92 mg K+ kg?1), 0.01 M CaCl2 (104 mg K+ kg?1), 0.1 M BaCl2 (126 mg K+ kg?1), and 1 M NH4OAc (312 mg K+ kg?1). Potassium extracted by 0.01 M CaCl2, 1 M NaCl, 0.1 M BaCl2, and 0.025 M H2SO4 showed higher correlation with K+ uptake by the crop (P < 0.01) than did NH4OAc (P < 0.05), which is used to extract K+ in the soils of the studied area. There were significant correlations among exchangeable K+ adsorbed on the planar surfaces of soils (labile K+) and K+ plant uptake and K+ extracted by all extractants. It would appear that both 0.01 M CaCl2 and 1 M NaCl extractants and labile K+ may provide the most useful prediction of K+ uptake by plants in these calcareous soils containing micaceous minerals.  相似文献   

6.
A greenhouse experiment was conducted with Lolium perenne to determine whether ammonium (NH4+-N) fixation by clay minerals can increase the recovery of nitrogen following application of 15N labelled urea. A silty loam subsoil, Bt horizon from an Alfisol derived from loess, pH (CaCl2) 7.9, was chosen for the experiment. The NH4+-N fixation capacity was altered by varying the distribution of potassium (K) in the upper and lower soil layer. In the K0 treatment (control), the upper soil layer fertilized with urea was not supplied with K, whereas the lower soil layer was fertilized with 300 mg K kg?1 soil. In the K1?, K2? and K3 treatment the upper soil was supplied with 100-, 200- and 300 mg K kg?1 soil, respectively. The soil in the lower layer of the K3 treatment was not supplied with K. The recovery of 15N from applied urea (15N uptake of Lolium perenne plus residual soil 15Nt) was 86.1% in the K0 treatment and 75.2%, 69.1% and 69.6% in K1-, K2- and K3 treatments, respectively, showing that 15N losses were smallest in the K0 treatment. Two weeks after applying 15N labelled urea the amounts of nonexchangeable 15NH4+-N in the upper soil layer were significantly higher in the K0 treatment than in the treatments with K application. Apparently, NH4+-N fixation by clay minerals can reduce NH3 volatilization after urea fertilization, if the amount of exchangeable K is low.  相似文献   

7.
The effectiveness of eight chemical extraction methods was evaluated on 15 Indian soils for the prediction of plant-available potassium (K+) to Sudan grass (Sorghum vulgare var. sudanensis) grown in modified Neubauer technique. Average amounts of soil K+ extracted were in descending order: Morgan’s reagent > 0.5 M sodium bicarbonate (NaHCO3) > neutral 1N ammonium acetate (NH4OAc) > 1N nitric acid (HNO3) > 0.02 M calcium chloride (CaCl2) > 0.1N HNO3 > Bray and Kurtz No.1> distilled water. The highest simple correlation with plant K+ uptake was obtained with NH4OAc-K+ (r = 0.866**) and the lowest with CaCl2-K+ (r = 0.45*). To develop the predictive models using stepwise regression, plant K+ uptake was used as the dependent variable and the extractable soil K+, pH, sand, silt and organic carbon (C) contents as the independent variables. Based on the final R2, the NH4OAc model was found to be the best predictor of plant-available K+ in the soils when used along with sand and organic C.  相似文献   

8.
A greenhouse experiment was conducted to study and quantify the daily uptake rate of nitrate, ammonium, phosphoric acid, potassium, calcium, magnesium, and sulfate (NO3?, NH4+, H2PO4?, K+, Ca2+, Mg2+ and SO42?) and to characterize the uptake daily pattern at different plant ages in a lettuce crop. The uptake rates per gram of plant fresh weight were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by NO3?/NH4+ conductivity and inductively coupled plasma atomic emission spectrometry (ICP-AES). The uptake rate of nitrogen, phosphorus and potassium (N, P and K) per unit mass of plant decreased with plant age following a reduction in plant relative growth rate. No significant differences were found in the absorption of Ca, Mg and sulfur (S) between the different weeks of growth. The daily absorption patterns showed no preference for the absorption of any of the ions during the daytime. A significant reduction in the absorption peaks of all the ions with increasing plant age was observed.  相似文献   

9.
ABSTRACT

Interactions between nitrate (NO3 ?), potassium (K+), and ammonium (NH4 +) were investigated using hydroponically grown cucumber (Cucumis sativus L.) plants. Ammonium as the sole nitrogen (N) source at 10 mM was toxic and led to overall growth suppression, chlorosis, and necrosis of leaves. After 20 days, 50% of the plants were dead. However, when NO3 ? was supplied at very low concentration together with high NH4 + (only 1% of total 10 mM N) all seedlings survived and their growth was improved. High K+ concentration (5 mM) also alleviated NH4 + toxicity and increased plant growth several fold compared to intermediate concentration of K+ (0.6 mM). Leaf total N and 15N derived from 15N-labelled NH4 + increased in the presence of NO3 ?, but decreased at high K+ concentration. High K+ supply enhanced total carbon (C) and δ 13C and stimulated GS and PEPCase activities in leaves and roots. Nitrate supplementation had no effect on GS or PEPCase activities. It is concluded that K+ may alleviate NH4 + toxicity, partly by inhibiting NH4 + uptake, partly by stimulating C and N assimilation in the roots.  相似文献   

10.
Nitrogen (N) and potassium (K) fertilization play a key role in forage crops and can significantly increase yields of ‘Marandu’ palisadegrass [Brachiaria brizantha (Hochst. exA. Rich.) Stapf.], one of the most important forage crops in Brazil. This study aimed to identify the concentrations of total N and K, nitrate (NO3?), and ammonium (NH4+), chlorophyll meter readings (SPAD), and nitrate reductase activity (At-RNA) required to maximize yield. Plants were grown in quartz substrate and treated with nutrient solutions that ranged from 2 to 33 mmol L?1 for N and 0.5 to 11 mmol L?1 for K. Dry matter production and At-RNA increased with increasing N and K supplies. SPAD readings correlated strongly with N leaf concentration and dry matter production and can be used to assess the N status of this species. The supply of N and K in the fertilization promoted high yield and adequate N and K concentration for plant metabolism.  相似文献   

11.
Zeolitites (ZTs) are rocks containing more than 50% of zeolite minerals and are known to be a suitable material for agricultural purposes by improving soil physicochemical properties and nitrogen (N) use efficiency. However, little is known about their effects on soil microbial biomass. This study aimed to evaluate short-term effects of different chabazite-rich ZT (CHAZT) amendments on soil microbial biomass and activity. A silty-clay agricultural soil was amended in three different ways, including the addition of natural (5% and 15%) and NH_4~+-enriched (10%) CHAZT. Soil dissolved organic carbon (C), total dissolved N, NH_4~+, NO_3~-, NO_2~-, microbial biomass C and N, and ergosterol were measured periodically over 16 d in a laboratory incubation. To verify the microbial immobilization of the N derived from NH_4~+-enriched CHAZT, a high15N source was used for enriching the mineral to measure the microbial biomass δ15N signature. An increase in the ergosterol content was observed in the soil amended with 5% natural CHAZT. However, no similar result was observed in the soil amended with 15% natural CHAZT, suggesting that the fungal biomass was favored at a lower CHAZT application rate. In the soil amended with NH+ 4-enriched CHAZT, microbial biomass N was related to NO_3~-production over time and inversely related to NH_4~+, suggesting high nitrification process. Isotopic measurements on microbial biomass confirmed immediate assimilation of N derived from NH_4~+-enriched CHAZT. These results suggested that the NH_4~+-enriched CHAZT used in this study supplied an immediately available N pool to the microbial biomass.  相似文献   

12.
Nitrogen is taken up by most plant species in the form of nitrate and ammonium. The objective of this study was to investigate the effect of different nitrogen forms on the growth of watermelon seedlings. Plants were grown in hydroponic culture with five nitrate (NO3?)/ammonium (NH4+) ratios (100/0, 75/25, 50/50, 25/75, 0/100). When the proportion of NH4+ was increased, the leaf number, leaf area, shoot height, net photosynthesis, biomass, and root growth were significantly decreased. Higher concentrations of nitrogen (N) and phosphorus (P) were observed when plants were supplied with mixed NO3? and NH4+ compared to NO3? or NH4+ alone, whereas the concentrations of potassium (K), calcium (Ca), and magnesium (Mg) were decreased with increasing NH4+. The microelements concentrations were generally increased with more NH4+ added. In addition, plants fed with higher NO3?/NH4+ ratios resulted in more minerals accumulation.  相似文献   

13.
Ion exchange preferences for NH4+ and K+ by soil exchanger surface can greatly affect the NO3? leaching into groundwater and nitrogen-use efficiency in agricultural production. Since NH4+ and K+ salts are usually applied together as fertilizers, the binary K→NH4 exchange of two benchmark Botswana soils, Pellustert and a Haplustalf, was studied to determine the selectivity coefficients and the thermodynamic exchange constant with special reference to N economy. The Vanselow and the Gaines and Thomas coefficients indicated preference for NH4+ by the Pellustert and K by the Haplustalf across the exchanger phase composition. The equilibrium constant (Kex) was 1.807 for the Pellustert and 0.174 for the Haplustalf. The exchange free energy (ΔGex0) was ?1.467 kJ mol?1 for the Pellustert and 4.334 kJ mol?1 for the Haplustalf. Negative ΔGex0 for the Pellustert is consistent with preference for NH4+ to K+ in contrast to positive ΔGex0 for the Haplustalf. The greater stability of NH4X than KX complex in the Pellustert, and KX than NH4X in the Haplustalf, would mean increased residence time of NH4+ in the Pellustert than the Haplustalf. The implication of short residence time of NH4+ in soil is rapid nitrification, thereby leading to NO3??N leaching losses and possible groundwater contamination.  相似文献   

14.
High concentrations of bicarbonate (HCO? 3) cause alkalinity of irrigation water and are associated with suppression in plant growth and micronutrient deficiencies, such as iron (Fe) and zinc (Zn). Because reports indicate that the deleterious effects of alkalinity may be counteracted partially by supplementary potassium (K+) or ammonium (NH4 +) an experiment was designed to evaluate the response of bean plants (Phaseolus vulgaris L.) grown in high alkalinity conditions to varying proportions of NH4 +, K+, or sodium (Na+) (as a potential substitute for K+). Plants established in a growth chamber were grown in hydroponics for 21 days in solutions containing 5 mM HCO? 3 and a total of 5 mM of a mixture of NH4 +, K+, and Na+. The proportions of NH4 +, K+, and Na+ were designed according to mixture experiment methodology. Total N in all the mixture treatments was maintained at 10 mM by using nitrate (NO? 3)-N, thus the NH4 +:NO? 3 ratio varied according to the proportion of NH4 + in the mixtures. Alkalinity caused suppression in plant growth and chlorophyll concentration in the younger leaves, whereas excessive NH4 + was associated with leaf scorching and decreased leaf expansion. High proportions of K+ alleviated alkalinity symptoms and produced higher shoot and root dry mass provided that NH4 + was included in the mixture. However, a proportion of NH4 + higher than 0.333 in the mixture (>1.66 mM NH4 +) induced toxicity. The highest shoot dry mass occurred if the NH4 +:NO? 3 ratio was 0.19:0.81 and the NH4 +:K+:Na+ proportion was 0.38:0.38:0.24 (1.9 mM NH4 + + 1.9 mM K+ + 1.2 mM Na+). Thus, an improvement in plant growth is achieved when NH4 +, K+, and Na+ are blended together, in spite of the high alkalinity treatment imposed. Optimum NH4 + was associated with a decrease in solution pH and an increase in shoot Fe and Zn concentration.  相似文献   

15.
Potassium (K) and nitrogen (N) are essential nutrients for plants. Adsorption and desorption in soils affect K+ and NH + 4 availabilities to plants and can be affected by the interaction between the electrical double layers on oppositely charged particles because the interaction can decrease the surface charge density of the particles by neutralization of positive and negative charges. We studied the effect of iron (Fe)/aluminum (Al) hydroxides on desorption of K+ and NH + 4 from soils and kaolinite and proposed desorption mechanisms based on the overlapping of diffuse layers between negatively charged soils and mineral particles and the positively charged Fe/Al hydroxide particles. Our results indicated that the overlapping of diffuse layers of electrical double layers between positively charged Fe/Al hydroxides, as amorphous Al(OH) 3 or Fe(OH) 3 , and negatively charged surfaces from an Ultisol, an Alfisol, and a kaolinite standard caused the effective negative surface charge density on the soils and kaolinite to become less negative. Thus the adsorption affinity of these negatively charged surfaces for K+ and NH + 4 declined as a result of the incorporation of the Fe/Al hydroxides. Consequently, the release of exchangeable K+ and NH +4 from the surfaces of the soils and kaolinite increased with the amount of the Fe/Al hydroxides added. The greater the positive charge on the surfaces of Fe/Al hydroxides, the stronger was the interactive effect between the hydroxides and soils or kaolinite, and thus the more release of K+ and NH + 4 . A decrease in pH led to increased positive surface charge on the Fe/Al hydroxides and enhanced interactive effects between the hydroxides and soils/kaolinite. As a result, more K+ and NH + 4 were desorbed from the soils and kaolinite. This study suggests that the interaction between oppositely charged particles of variable charge soils can enhance the mobility of K+ and NH + 4 in the soils and thus increase their leaching loss.  相似文献   

16.
In this paper, the uptake kinetics of various nitrogens (nitrate (NO3?), ammonium (NH4+), urea, amino acid) by Chinese kale (Brassica oleracea L. var. Bailey) were studied under hydroponic condition. The results indicated that the uptake kinetics of organic and inorganic nitrogen (N) by Chinese kale conform to the Michaelis–Menten equation, and the maximum uptake rate (Vmax) and affinity index (1/Km) showed nitrate (NO3—N) > ammonium (NH4+-N) > urea-N > Gly-N, with significant differences between treatments (p < 0.05). Adding different types of N to NO3? nutrient solution had little impact on its affinity, but significantly decreased the NO3? Vmax, which showed NO3–N > NO3? + NH4+ > NO3? + urea > NO3? + Gly. Chinese kale preferred inorganic N to organic N, with NO3? preceding NH4+. Adding organic and NH4+ N to nutrient solution reduced the NO3? uptake capacity by the plant.  相似文献   

17.
Abstract

Clinoptilolite, a zeolite mineral with a high cation exchange capacity and surface area, has ion‐exchange properties that can be utilized to adsorb NH4 +, protecting it from losses during composting of N‐rich animal manures. Ammonium adsorption by the natural zeolite clinoptilolite was studied to ascertain the effectiveness of the zeolite as an NH4 + adsorbent at pH 4, 5, 6, and 7. The NH4 + adsorption data were fitted to the one‐ and two‐surface Langmuir, Freundlich, and Temkin isotherms. All models described the NH4 +adsorption data successfully (r2≥0.939). The one‐surface Langmuir, Freundlich, and Temkin were converted to pH‐dependent forms. The amount of NH4 + adsorbed increased as pH and initial NH4 +concentration increased. From the one‐surface Langmuir isotherm, the NH4 +adsorption capacity (Xm) of the zeolite increased linearly with pH (r2=0.994), and was estimated to be 9,660 mg N kg‐1 at pH4, 11,220 mg N kg‐1 at pH 5, 12,720 mg N kg‐1 at pH 6, and 13,830 mg N kg‐1 at pH 7. The adsorption of higher amounts of NH4 +with increasing pH and initial NH4 +concentration is an important characteristic of the zeolite that can be beneficial to minimizing N‐losses via NH3volatilization during composting of N‐rich animal manures.  相似文献   

18.
应用离子交换树脂膜法评价缓释复合肥料供肥特性的研究   总被引：1，自引：0，他引：1  
在25℃连续恒温培养条件下,采用离子交换树脂膜(IERM)提取,测定了不同缓释复合肥料(SRCF)在土壤中的氮、磷、钾养分的供肥特性,并与盆栽水稻的养分吸收进行比较。结果表明:56.d内2种SRCF在土壤中NO3--N和NH4+-N养分的日均供应量占普通复合肥(NCF)的3.3%～58.1%,并以NH4+-NNO3--N;2种SRCF的H2PO4-和K+的日均供应量占磷、钾施用量分别为NCF的14.9%、23.2%和92.7%、64.5%。与NCF相比,SRCF氮素和磷素养分在土壤中释放具有明显的缓释作用。Elovich和抛物线扩散方程的b值可分别用来表征SRCF的NO3--N、H2PO4-和NH4+-N、K+养分在土壤中释放后被吸收的日均供肥量。用离子交换树脂膜法提取测定的SRCF养分在土壤中的供肥特性与该法测定的土壤本身养分的供肥特性相似。SRCF氮、磷、钾养分累积释放量与盆栽水稻氮、磷、钾养分吸收量呈显著或极显著的正相关(r=0.869～*0.994**)。用离子交换树脂膜提取测定和评价缓释复合肥料在土壤中养分的供肥特性是一种比较理想的方法。  相似文献   

19.
The effectiveness of lime-ammonium-nitrate (LAN) as a nitrogen (N) fertilizer in weathered soils depends on the respective selectivity for ammonium (NH4) and calcium (Ca) by the soils. The study assessed Ca2+/NH4+ exchange selectivity of two benchmark soils from Botswana and examined the soil fertility management implications. Surface horizons (0–20 cm) of Pellustert and Haplustalf were equilibrated with 50 ml stock solution containing variable concentrations of Ca2+ and NH4+. The Ca2+/NH4+ exchange data were fitted into the Vanselow (KV), Gaines and Thomas (KGT), Davies (KD), and the regular solution (KRS) equations. The selectivity coefficients for the Ca2+/NH4+ exchange reactions varied widely with the soil exchanger composition except for the relatively stable KRS. The selectivity coefficients indicated strong preference for NH4+ to Ca2+. The thermodynamic exchange constant, Kex, was 5.75 ± 1.24 in the Pellustert, indicating preferential adsorption of NH4+, but not in the Haplustalf with Kex = 0.92 ± 0.27. The free energy for Ca2+/NH4+ exchange (ΔG°ex) was negative (?4.26 ± 0.59 kJ mol?1) in the Pellustert but slightly positive in the Haplustalf (0.34 ± 0.87 kJ mol?1). In conclusion, the soil-NH4 complex was more stable than soil-Ca complex in the Pellustert, indicating LAN as a N fertilizer would have greater potential effectiveness in the Pellustert than in the Haplustalf.  相似文献   

20.
Abstract

Very low recovery of NH4+‐N was observed in total N determination of (NH4)2SO4 in KC1 solutions by a semimicro Kjeldahl method using permanganate and reduced iron to recover NO3‐ and NO2‐, whereas complete recovery was obtained in analysis of NH4+‐N in water, and of NO3 ?‐N or NO2 ?‐N in either water or KC1 solutions. The loss of NH4 +‐N observed with KC1 was attributed to the formation of NCl3 upon reaction of NH4 + with Cl2 generated during oxidation of Cl? by MnO4 ?. This difficulty is avoided by using K2SO4 instead of KC1 for extraction of inorganic N from soil. Complete recovery was obtained by adding 15N‐labeled NH4+, NO3‐, or NO2‐ to 0.5 M K2SO4 soil extracts, and total 15N analyses of the labeled extracts were in good agreement with values calculated from the additions of 15N and the total N contents of the soil extracts.  相似文献   

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