Determination of nitrogen by microdiffusion in mason jars: III. Nitrogen and nitrogen‐15 in Kjeldahl digests

Abstract

Diffusion methods for quantitative determination and isotope‐ratio analysis of inorganic N in soil extracts were modified for use with Kjeldahl digests. The digest was diluted to 25 mL with deionized water, and an aliquot (to 6 mL) was transferred in a shell vial (17 mm dia., 60 mm long) to a 473‐mL (1‐pint) wide‐mouth Mason jar containing 15 mL of 8 M NaOH. The NH₃ liberated by overturning the vial inside the sealed jar was collected for 48 h at room temperature (24 h with orbital shaking) in 3 mL of boric acid‐indicator solution in a Petri dish, or in an acidified glass‐fiber disk, suspended from the Mason‐jar lid. Determinations of N and ¹⁵N by diffusion were in close agreement with analyses using conventional steam‐distillation and concentration techniques.     

Influence of Azospirillum inoculation and nitrogen supply on grain yield,and carbon‐ and nitrogen‐assimilating enzymes in maize

Nitrogen (N) supply increased yield, leaf % N at 10 days after silking (DAS) and at harvesting, the contents of ribulose‐1,5‐bisphosphate carboxylase (RUBISCO) and soluble protein, and the activities of phosphoenolpyruvate carboxylase (PEPC), and ferredoxin‐glutamate synthase (Fd‐GOGAT), but not of glutamine synthetase (GS) for six tropical maize (Zea mays L) cultivars. Compared to plants fertilized with 10 kg N/ha, plants inoculated with a mixture of Azospirillum sp. (strains Sp 82, Sp 242, and Sp Eng‐501) had increased grain % protein, and leaf % N at 10 DAS and at harvest, but not grain yield. Compared to plants fertilized with either 60 or 180 kg N/ha, Azospirillum‐inoculated plants yielded significantly less, and except for GS activity, which was not influenced by N supply, had lower values for leaf % N at 10 DAS and at harvest, for contents of soluble protein and RUBISCO, and for the activities of PEPC and Fd‐GOGAT. Yield was positively correlated to leaf % N both at 10 DAS and at harvest, to the contents of soluble protein and RUBISCO, and to the activities of PEPC and Fd‐GOGAT, but not of GS, when RUBISCO contents and enzyme activities were calculated per g fresh weight/min. However, when enzyme contents and enzyme activities were expressed per mg soluble protein/min, yield was correlated positively to RUBISCO and PEPC, but negatively to GS. These results give support to the hypothesis that RUBISCO, Fd‐GOGAT, and PEPC may be used as biochemical markers for the development of genotypes with enhanced photosynthetic capacity and yield potential.     

Quantification of the carbon and nitrogen cycles in long‐term field experiments in Prague

The oldest still existing long‐term field experiments in Czech Republic were founded in 1955. In Prague Ruzyné, there are five of nine experiments founded by ?karda. Data of two of these experiments (Block III and Block B) were used to evaluate the carbon and nitrogen cycles in time period 1966–1997. These two experiments have a similar design. They differ in the crop rotation. Four variants of organic and mineral fertilisation, receiving similar doses of fertilisers, have been selected. The same was calculated for the same time period for a mini‐plot bare fallow field experiment founded in 1958 by Novák.

The results of these experiments conducted in one locality (the same soil and climatic conditions) show the effect of the cultivated crops on the carbon and nitrogen cycles (comparing bare fallow experiment with the cropped ones), the effect of organic and mineral fertilisation (among all experiments), and the effect of crop rotation (comparing Block III to Block B) on these cycles.     

Determination of dissolved organic nitrogen using persulfate oxidation and conductimetric quantification of nitrate‐nitrogen

Abstract

Nitrogen (N) in forest soil extracts and surface waters may be dominantly in organic compounds as dissolved organic nitrogen (DON). Due to various difficulties associated with measuring total N (as TKN) by the Rjeldahl digest, this important vehicle for nutrient movement is rarely monitored. By coupling two relatively new methods and optimizing them for use in soil studies, we developed an alternative method for measuring DON. Analysis of pure compounds and field samples shows that persulfate oxidation combined with conductimetric quantification of nitrate (NO₃) provides a highly accurate measure of dissolved N content. With relatively inexpensive equipment and reagents, a single technician can digest and assay over a hundred samples a day. This rapid, simple, and accurate assay may make it possible to routinely monitor DON where it had previously been impractical. This in turn could substantially enhance understanding about the form and quantity of N involved in nutrient fluxes.     

Carbon and nitrogen turnover in response to warming and nitrogen addition during early stages of forest litter decomposition—an incubation experiment

Purpose

Little is known about the interactive effects of temperature, nitrogen (N) supply, litter quality, and decomposition time on the turnover of carbon (C) and N of forest litter. The objective of this study was to investigate the interactive effects of warming, N addition and tree species on the turnover of C and N during the early decomposition stage of litters in a temperate forest.

Materials and methods

A 12-week laboratory incubation experiment was carried out. The leaf litters including two types of broadleaf litters (Quercus mongolica and Tilia amurensis), a needle litter (Pinus koraiensis), and a mixed litter of them were collected from a broad-leaved Korean pine mixed forest ecosystem in northeastern China in September 2009. Nine treatments were conducted using three temperatures (15, 25, and 35 °C) combined with three doses of N addition (equal to 0, 75, and 150 kg?·?ha^?1?a^?1, respectively, as NH₄NO₃).

Results and discussion

After 12 weeks of incubation, the mass loss ranged between 12 and 35 %. The broadleaf litters had greater mass loss and cumulative CO₂–C emission than the needle litter. Temperature and N availability interacted to affect litter mass loss and decomposition rate. The dissolved organic carbon (DOC) and nitrogen (DON) concentrations in litter leachate varied widely with litter types. DOC increased significantly with increased temperature but decreased significantly with increased N availability. DON increased significantly with increased N availability but showed a higher level at the moderate decomposition temperature. The amounts of CO₂ and N₂O emission were significantly higher at 25 °C than those at 15 and 35 °C, and were significantly increased by the N addition.

Conclusions

The present study indicated relatively intricate temperature and N addition effects on C and N cycling during early stages of litter decomposition, implying that future increases in temperature and N deposition will directly affect C and N cycling in broad-leaved Korean pine mixed forest ecosystem, and may indirectly influence the ecosystem composition, productivity, and functioning in NE China. It is, therefore, important to understand the interactive effects of biotic and abiotic factors on litter decomposition in field conditions in order to assess and predict future ecosystem responses to environmental changes in NE China.     

Time of availability influences mixed‐nitrogen‐induced increases in growth and yield of wheat 1

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.     

Relationships between nitrogen rate,plant nitrogen concentration,yield and residual soil nitrate‐nitrogen in silage corn

Abstract

Nitrogen (N) fertilizer is a key factor of yield increase but also an environmental pollution hazard. The sustainable agriculture system should have an acceptable level of productivity and profitability and an adequate environmental protection. The objectives of this study were to determine the relationships between N rate, DM yield, plant N concentration (NC) and residual soil nitrate‐nitrogen in order to improve the predicted N rate in corn (Zea mays L.) silage. The experiment was conducted over a period of three years in the province of Quebec on three soil series in a continuous corn crop sequence. Treatments consisted of six rates of N: O, 40, 80, 120, 160, and 200 kg N ha^‐1 as ammonium nitrate applied at planting: broadcast and side banded. Four optimum N rates were calculated using different models: (i) economic rate base on fertilizer and corn price using the quadratic model (E); (ii) economic rate based on fertilizer and corn price using the quadratic‐plus‐plateau model (QP); (iii) critical rate based on linear‐plus‐plateau model (P); (iv) lower than maximum rate (L) corresponding to 95% of maximum yield. The optimum plant NC at all growing stages and the N uptake at harvest were calculated depending on these N rates and yields.

The NC of whole plant at 8‐leaf stage (25–30 cm plant height) of ear leaf at tasselling and of whole plant at harvest stage, the N rate, the N uptake at harvest and the DM yield were all significantly intercorrelated and affected by soils and years, but not affected by N fertilizer application method. The DM yield was linearly and significantly related to NC of whole plant at 8‐leaf stage (rv = 0.932**). At this stage, the average NC corresponding to the optimum N rate and yield was of 3.71, 3.68, and 3.66% as calculated with E, L, and P model, respectively. Our data suggest that the NC of whole plant at 8‐leaf stage may be used to evaluate the N nutrition status of plant and the required optimum N fertilizer rate. The NC of ear leaf at tassel stage was also significantly correlated to corn yield (r = 0.994**). It may be used as an indicator to evaluate the near‐optimum N rate in the subsequent years.

The N uptake by whole above‐ground plant at harvest was quadratically related to corn yield. Data show that at high fertilizer N rate, the N uptake still increased without significantly increasing yield. The N uptake was of 176.5, 163.0, and 155.0 kg N ha^‐1 using the E, L and P rates of 146, 126, and 115 kg N applied ha^‐1, respectively. The optimum N rate and yield were affected by soil type and year, but not by the method of N fertilizer application. The yield increased rapidly up to a N rate of about 120 kg N ha^‐1 and then quite slightly to a maximum N rate of 192 kg N ha^‐1. The optimum N rate was of 115 and 126 kg N ha^‐1 using the P and L model respectively and as high as 146.8 kg N ha^‐1 using the E model. The L model, using a much smaller N rate, gave a reasonably high yield compared to E rate (12.2 and 12.5 Mg ha^‐1, respectively). The data show that a relatively much lower N rate than maximum did not proportionally diminish the yield. Thus, for a difference of 40.4% between maximum N rate and P rate a difference of only 7.4% in yield was observed. Using the L model the differences in rate and yield were of 34.4% and 4.7%, respectively. The QP model gave no significant difference compared to E model.

At harvest the residual soil NO₃‐N increased significantly with increasing N fertilizer rate in whole of the 100 cm soil profile, but mainly in the top 40 cm soil layer. The total NO₃‐N found in 0–100 cm profile at rate of 0, 120 and 200 kg applied N ha^‐1 at planting was as high as 33.7, 60.5, and 74.5 kg N ha^‐1 respectively in a light soil and 37.5, 97.5, and 145.5 kg N ha^‐1 in a heavy clay soil. The difference in NO₃‐N content in the 60–100 cm layer between different applied N rate suggests that at harvest, part of fertilizer N applied at planting was already leached below the 100 cm soil layer. Results, thus, show that reasonably high corn yields can be obtained using more adequate N fertilizer rates which avoid the overfertilization and are likely to reduce the air and ground water pollution.     

Effects of supplemental nitrogen on nitrogen‐assimilation enzymes,free amino nitrogen,soluble sugars,and crude protein of rice

Abstract

An upland rice variety IAC‐47 was grown in a greenhouse to determine the effect of foliar nitrogen (N) supplementation during grain development on the activity of the N assimilation enzymes, nitrate reductase (NR) and glutamine synthetase (GS), on free amino‐N content and leaf soluble sugars, and on grain crude protein content. At 10 and 20 days after anthesis (DAA), the leaves were fertilized with a liquid fertilizer containing 32% N as 12.8% urea, 9.6% ammonium (NH₄), and 9.6% nitrate (NO₃) in increasing rates corresponding to 0,20+20, 40+40, and 60+60 kg N ha^‐1. Leaves were collected twice (at 12 DAA and 14 DAA for GS activity, sugar and amino‐N content, and at 11 and 13 DAA for NRA) after each application of leaf N. The late foliar application of N increased significantly grain crude protein without a corresponding decrease in grain weight. The NR activity (NRA) increased after the foliar application of N. In the flag leaf, 60+60 kg N ha^‐1 (21 DAA) resulted in higher NRA (20x over the control), while GS activity was smaller than the control. At 22 DAA there was an increase in GS activity in the flag leaf at 20+20 N level. However, the GS activity decreased as applied N levels increased. Also at the 20+20 level, there were increases in free amino‐N in the flag leaf and second leaf at the final harvest. Throughout the experiment, plants at the 60+60 N level had the lowest levels of soluble sugars. Increases in crude protein were highest at 40+40 N level (27.9%), followed by 60+60 (18.7%).     

Influence of nitrate‐nitrogen and ammonium‐nitrogen on calcium (45Ca2+) absorption in sorghum root tips

Abstract

Root‐tip, 1‐cm of Sorghum bicolor (L.) Moench cv SC283, SC574, GP‐10, and Funk G522DR were exposed to calcium (⁴⁵Ca²⁺) at pH 5.5 for 2‐hr in the presence of nitrate‐nitrogen (NO3^?‐N) or ammonium‐nitrogen (NH4+‐N). Nitrate (0.1 mM) induced significantly increased ⁴⁵Ca uptake in Funk G522DR, SC283, and GP‐10 while 0.01 mM NO₃ ^?‐N induced significantly increased ⁴⁵Ca'uptake in SC574, but ⁴⁵Ca absorption was significantly decreased at 1 mM NO₃—N. In the presence of the NH4⁺ ion, ⁴⁵Ca uptake was increased up to 8X that of the NH₄ ⁺‐N untreated roots. When ammonium chloride (NH₄CI) was used, the Cl^? tended to induce an increased ⁴⁵Ca uptake. Cultivar variation was present.     

The relationship between applied nitrogen and the concentration of nitrate‐N in cotton petioles

Abstract

Cotton petioles from irrigated plants grown under varying nitrogen regimes were analyzed for nitrate‐N (NO₃‐N). The most recent, fully matured petioles were selected. The concentration of NO₃‐N in the petioles was related to applied N rates and the yields of lint obtained. The concentration of NO₃‐N for any given N application declined as the season progressed. The concentration of petiole nitrate increased at all sampling dates as the rate of applied N increased. The relationship between applied N and NO₃‐N concentrations was most predictable when samples were collected two weeks after the initiation of squaring. The influence of applied N on the concentration of petiole nitrate was also greatest at this stage. The diagnosis of either N deficiency or excess N would be feasible by petiole analysis when the effects of stage of growth could be separated from the effects of soil N.     

Photosynthesis acclimation,leaf nitrogen concentration,and growth of four tree species over 3 years in response to elevated carbon dioxide and nitrogen treatment in subtropical China

Purpose  

Up to date, most studies about the plant photosynthetic acclimation responses to elevated carbon dioxide (CO₂) concentration have been performed in temperate areas, which are often N limited under natural conditions and with low ambient N deposition. It is unclear whether photosynthetic downregulation is alleviated with increased N availability, for example, from increased N deposition due to fossil fuel combustion in the tropics and subtropics. Awareness of plant photosynthetic responses to elevated CO₂ concentration will contribute to the better understanding and prediction of future forest productivity under global change.     

Evaluation of in‐season nitrogen tissue tests for drip irrigated leaf and romaine lettuce

Abstract

Chemical analysis of selected plant tissues as a nitrogen (N) fertility diagnostic technique has been established for many irrigated horticultural crops, but not for recently popular high value specialty vegetables such as leaf and romaine lettuce (Lactuca sativa L.). Three field experiments were conducted in southern Arizona during three years to determine the plant part and N form that is most responsive to soil N supply, and to formulate in‐season N status interpretations based upon appropriate tissue tests. Fertilizer N treatments were applied through subsurface drip irrigation tubing at scheduled intervals to leaf and romaine lettuce to provide N levels ranging from deficient to excessive. Plant samples, which included the midrib or leaf blade from the youngest full‐sized leaf and whole plant tissues were collected throughout the growing season with midribs tested for NO₃‐N and the remaining tissues for total nitrogen content Marketable fresh weight yields were recorded at harvest for all N treatments in each experiment. In Experiment 1, it was determined that of the plant N testing methods evaluated, midrib NO₃‐N concentration in the youngest mature leaf was the most responsive to differences in soil N supply. Experiments 2 and 3 focused on the midrib NO₃‐N method of testing to develop season‐long interpretations for evaluating the N fertility status of both crops. The slow root and shoot development inherent in each lettuce type and the minimal uptake of N through mid‐season did not contribute to well‐defined differences between deficient, sufficient, and excessive midrib NO₃‐N levels. Resulting interpretations of midrib NO₃‐N concentrations for leaf and romaine lettuce feature a greater sensitivity and practicality as a N fertility diagnostic tool during the latter one‐half of the growing season.     

Effects of autumn foliar application of 15n‐urea on nitrogen storage and reuse in apple 1

Effects of autumn foliar application of N‐urea on N storage and reuse in young apple seedling (Malus Pumila Mill.) were studied. Foliar application of urea^‐15 N (3.5%) during autumn enhanced the retranslocation of leaf N to other plant parts and increased stored N. Foliar N sprays increased the proteolytic activities of the leaves; therefore, such activities appear to be a major mechanism of retranslocation of leaf N. Foliar applied N enabled the plant to produce more growth during the following seasons. A considerable portion of the plant total N during second and third years was attributable to the foliarly applied N during the first year.     

Recent advances in the chemistry of nitrogen,phosphorus and potassium as fertilizers in soil: A review

The advent of civilization has made humans dependent on plants for food and medicine, leading to the intensification of agricultural production. The intense cultivation of crops has resulted in the depletion of available nutrients from soil, thereby demanding the application of excess nutrients to soil to improve yield. Thus, mineral fertilizer discovery and application have, in many ways, contributed greatly to meeting global food demands. However, aside from the positive effects of mineral fer...     

The influence of solid urban waste compost and nitrogen‐mineral fertilizer on growth and productivity in potatoes

Abstract

The influence of solid urban waste (SUW) compost and nitrogen (N)‐mineral fertilizer on the growth and productivity in semi‐early harvest potatoes (Solanum tuberosum L, var. ‘Edzina') was studied over a period of three years. Nine treatments derived from a factorial combination of 3 levels of SUW compost (0, 18, 36 T#lbha^‐1) and 3 levels of N‐mineral fertilizer (0, 125, 250 Kg N ha^‐1) were carried out on a sandy, moderately fertile plot. The applications of SUW compost and N‐mineral fertilizer showed a stimulation in plant development with respect to the non‐treated controls. The mineral fertilizer treatment gave markedly higher results. Plant response to the combined mineral fertilizer‐compost treatments demonstrated a tendency towards saturation within each level of application. Potato productivity results indicated that this crop reacts strongly and positively to an application of N‐mineral fertilizer, but only slightly to the treatment levels of compost considered in the study. As a consequence of the application of SUW compost, the application‐response graphs reveal a reduction in the optimal levels of N‐mineral fertilizer application and an increase in the efficacy of the mineral fertilizer.     

Use of reflectometry for determination of nitrate‐nitrogen in well water

Recurrent monitoring of water wells is necessary to ensure that nitrate‐nitrogen (NO3‐N) concentrations in groundwater do not exceed 10 mg/L, the maximum contaminant level set by the U.S. Environmental Protection Agency. Continuous chemical analysis is often a time consuming and expensive process. A recently developed ‘Reflectoquant Analysis System’, which employs reflectometry techniques, may offer a simple and accurate method for NO3‐N analysis. The objective of this study was to evaluate the ‘Reflectoquant Analysis System’ as an alternative method for determination of NO3‐N in well water. Water samples were collected from 42 wells in Oklahoma. The samples were analyzed using the ‘Reflectoquant Analysis System’, automated cadmium reduction (Griess‐Ilosvay), ion chromatography, and phenoldisulfonic acid procedures. The linear range of the ‘Reflectoquant Analysis System’ is 1.1 to 50.6 mg/L NO3‐N. Samples exceeding this range must be diluted before analysis is performed. Excluding two wells where NO3‐N was >50.6 mg/L, simple correlation was high (r > 0.91) among the four procedures evaluated. In addition, slopes and intercepts from linear regression of NO3‐N among procedures were not significantly different. Population means obtained using the four methods were very similar. For this sample of wells, the ‘Reflectoquant Analysis System’ was precise and provided NO3‐N analysis of water samples equivalent to standard methods. Other advantages of the ‘Reflectoquant Analysis System’ are short analytical times, reduced operator training period, and competitive costs compared to standard methods.     

Changes in nitrogen and phosphorus concentrations of silicon‐fertilized rice grown on organic soil 1

Rice grown on the organic soils of the Everglades is routinely fertilized with silicon (Si). The objective of this research was to investigate changes in nitrogen (N) and phosphorus (P) concentration in various plant parts in response to Si fertilization. Two cultivars were grown in lysimeters filled with low‐Si soil. Half the lysimeters were fertilized with calcium silicate to provide 2Mg Si ha^‐1 and the other lysimeters remained unfertilized as a control. Nitrogen concentration decreased in all plant parts with Si fertilization. Phosphorus concentration increased with Si. Maturity was earlier in the Si fertilized rice.     

Concentrations of total nitrogen in squash,cucumber and melon in relation to growth,and to a piper‐steenbjerg effect

Abstract

Squash (Cucurbita pepo), cucumber (Cucranis sativus), and sweet melon (Cucumis dudain) were grown in sand cultures with N supply concentrations as the variable. For several reasons, total‐N values were found to be less satisfactory than NO ‐N for the purpose of determining the critical nitrogen concentration for maximum growth. Concentrations of total‐N in mature petioles were higher in plants severely deficient in N than in less deficient plants, characteristic of a Piper‐Steenbjerg effect.     

Release and recovery of nitrogen from winter annual cover crops in no‐till corn production

Abstract

Soil bulk density markedly influences hydrolysis of surface‐applied granular urea that is vulnerable to serious ammonia volatilization losses. In order to decrease the ammonia losses by retarding urea hydrolysis, several chemicals have been tested for their soil urease inhibition properties. Phenyl phosphorodiamidate (PPDA) is a potent soil urease inhibitor. Laboratory studies using soil column incubations were conducted to investigate the effect of soil bulk density on inhibition of hydrolysis of surface‐applied urea granules (=20 mg of urea/granule) containing 1% PPDA in unsaturated soils. The increase in soil bulk density (from 0.69 to 1.50 Mg/m³) markedly increased the rate of hydrolysis of surface‐applied urea granules and significantly decreased the apparent urease inhibition by PPDA present in the granules. These results are attributed to the probable spatial separation of urea and PPDA because of the differences in diffusive transports in unsaturated soils caused in part by differences in their solubilities in water.