Decrease In Total Nitrogen Research Articles

Effect of Potassium, Magnesium, and Calcium Deficiencies on Nitrogen Constituents and Chloroplast Components in Citrus Leaves

The chlorotic appearance of mineral-deficient citrus leaves presumably reflects degradative changes in chloroplast components, most of which have nitrogen as a principal constituent. To examine this assumption the size of some major nitrogen pools, the SDS-PAGE pattern of soluble and chloroplast membranal proteins, and the activities of nitrate reductase and ribulose bisphosphate carboxylase (RuBPcase) were determined in leaves of rough-lemon (Citrus volkameriana Ten. & Pasq) plants grown hydroponically for 3 to 10 months under K, Mg, and Ca deficiencies. Plants grown under minerally deficient conditions produced less biomass. Leaves developing under K, Mg, and Ca-deficient conditions had significantly reduced concentrations of the respective elements. Chlorophyll levels of the chlorotic Mg and Ca-deficient leaves were lower than those of control leaves but chlorophyll a/b ratios were not markedly different. Calcium deficiency caused significant decreases in total nitrogen, nitrates, and the free amino acid pool. Proline which is the major component of the free amino acid pool decreased by 82.5%. Calcium-deficient leaves had significantly lower nitrate reductase and RuBPcase activities. The level of RuBPcase holoenzyme and its subunits were also reduced. Protein levels of K, Mg, and Ca-deficient leaves were not significantly altered. The SDS-PAGE patterns of soluble and chloroplast membranal proteins did not reveal major qualitative changes. In conclusion, the data do not demonstrate a general close link between chlorosis of minerally deficient citrus leaves and nitrogen metabolism. Calcium deficiency seems to specifically interfere with early stages of nitrogen assimilation and free amino acid accumulation but the metabolic integrity of the leaf is apparently maintained even under severe nutritional stress conditions.

Some Observations on the Changes of Physico-Chemical and Biological Factors in Victoria Harbour and Vicinity, Hong Kong, 1988–1996

This study analysed monthly physico-chemical and biological data collected from 18 marine monitoring stations in Victoria Harbour and its vicinity in Hong Kong, from 1988 to 1996. Cluster analysis based on all water quality parameters measured shows that the 18 monitoring stations can be grouped into four clusters: Cluster I consists of stations located in the Harbour proper; Cluster II consists of stations located west of the Harbour and along the Rambler Channel; Cluster III consists of stations located east of the Harbour near Junk Bay and Cluster IV consists of stations located west of the Harbour and near the Ma Wan, Kap Shui Mun and Western Fairways. Factor analysis shows high positive loadings for nutrients in the first two factors of the four clusters. This suggests that effluents from the 11 outfalls of sewage screening plants influence the water quality of Victoria Harbour and its vicinity. Other factors such as storm water runoff, marine traffic, construction and industrial activities and the Pearl River discharges also appear to play an important role in determining local water quality. Five stations located along an east–west transect across the Harbour were selected for trend analysis. The three stations located in the Harbour exhibit an increasing trend for temperature and levels of total phosphorus (TP), ortho-phosphate phosphorous (PO 4-P) and faecal bacteria and a decreasing trend for pH and levels of total nitrogen (TN), total kjeldahl-nitrogen (TKN), 5-day biochemical oxygen demand (BOD 5) and chlorophyll a. For the station located east of the Harbour, an increasing trend is observed for levels of TP, PO 4-P, but no decreasing trend in TN and TKN is detected. For the station located west of the Harbour, no decreasing trend in TN, TKN and chlorophyll a is observed. Changes in levels of phosphorus and nitrogen in Victoria Harbour and the immediate vicinity have led to significant increases in the ratios of Total Silica (TSi) to TN, as well as a decrease in TN to TP and TSi to TP in most stations. Results of the present study show that Victoria Harbour and its immediate vicinity remain polluted.

The hydrochemical state of Lake Peipsi-Pihkva

The distribution and time dependence of total phosphorus (TP), dissolved inorganic phosphate (PO4P), total nitrogen (TN), chlorophyll a (Chl), dichromate oxidizability (CODCr), permanganate oxidizability (CODMn), water colour (Col) and transparency (SD), pH, dissolved oxygen (O2) and oxygen saturation (O2%) in the surface water of Lake Peipsi-Pihkva are studied by using 65-parameter regression models with the help of the SAS system. The yearly means, polarity and seasonal dependence of each investigated parameter during 1985–1994 are estimated from fitted models. The bulk of data consists of 456 to 1149 measurements per parameter. L. Peipsi-Pihkva appears to be polar with respect to the majority of the studied parameters. The content of TP, PO4P, TN, Chl, CODCr, CODMn, and Col decrease from south to north, while SD has an opposite trend. pH, O2, and O2% are quite uniform all over the lake. L. Peipsi is eutrophic, L. Pihkva is hypertrophic. The lake is influenced by significant yearly and seasonal changes. It is concluded that the Velikaja River is the main source of pollution for L. Peipsi-Pihkva.

Nutrient inputs from seabirds and humans on a populated coral cay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 124:189-200 (1995) - doi:10.3354/meps124189 Nutrient inputs from seabirds and humans on a populated coral cay Staunton Smith J, Johnson CR Inputs of inorganic nutrients in 1992 from seabirds (white-capped noddy and wedgetail shearwater, maximum of ca 80000 breeding pairs) are compared to inputs from humans (97700 person days) on Heron Island at the southern end of the Great Barrier Reef, Australia. We estimated that noddies deposited ca 107 t, and shearwaters ca 22 t, of fresh guano. The composition of fresh noddy guano was 7.3% nitrogen, 1.5% phosphorus, 60% moisture and 31.2% other substances. Assuming a similar composition for shearwaters, the total annual deposition of guano contained 9.4 t nitrogen and 1.9 t phosphorus. Experiments examining effects of ageing of guano indicated a large decrease in total nitrogen in guano under humid conditions over 4 d as a result of volatilisation of NH3. Under natural conditions most of the deposited nitrogen is likely to be lost as NH3 and a relatively small fraction of the soluble component leached into the cay, but the precise dynamics will depend on rainfall and wind patterns. Phosphorus was not volatilised from guano under any experimental conditions. Although inputs of nitrogen and phosphorus from human sewage into the cay system (ca 0.3 t of each) were much less than that from birds, all nutrients from humans are released in liquid form and percolate directly into the cay. Significant seasonal and tidal variations in standing concentrations of NH3, oxidised forms of nitrogen (NO2+NO3), and PO4 were detected in the water column around the island. Trends of higher mean concentrations of all nutrients in summer than in winter, and higher concentrations at low tide than at high tide except at sites close to the island where nutrient levels were high independent of tide, suggest that nutrients may be transported from guano on Heron Island into the water immediately surrounding the island. The exact fate and mechanisms of transport of all nutrients require further attention. Inorganic nutrients . Guano . Sewage . Great Barrier Reef Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 124. Publication date: August 10, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Carbon and nitrogen in arable soils as affected by supply of N fertilizers and organic manures

Results from a long-term, small plot field experiment, started in 1956, comparing different mineral N fertilizers and organic amendments are presented. Continuous bare fallow was included in the plan. The treatments resulted in large differences in soil organic carbon. No steady state was established. In spite of large additions of fresh organic matter with varying nitrogen content, the C/N ratio remained as a rule around 10. The only exception was peat. This is comparatively resistant against microbial decomposition. Therefore the C/N ratio was influenced by undecomposed peat, poor in nitrogen. Nitrogen balances covering the whole experimental period are presented. Crop residues poor in nitrogen and nitrogen uptake by the crop were found to decrease nitrogen losses. Where no organic amendment was added, there was a decrease in total nitrogen in soil. Addition of organic amendments resulted in the opposite situation. Farmyard manure caused a greater increase of total nitrogen in soil than green manure, demonstrating the importance of the quality of raw material for the yield of humus material.The sizes of soil organic matter fractions were estimated. The “old” humus fraction was estimated to 23.6 t ha−1 C. The “active” and “young” humus fractions accounted for 20–61% of the soil organic carbon depending on the level of fertilization and the supply of fresh organic matter. It was stated that those fractions are of great importance for the capacity of the soil to mineralize nitrogen.

Isotope ratios and concentrations of sulfur and nitrogen in needles and soils of Picea abies stands as influenced by atmospheric deposition of sulfur and nitrogen compounds

Concentrations and natural isotope abundance of total sulfur and nitrogen as well as sulfate and nitrate concentrations were measured in needles of different age classes and in soil samples of different horizons from a healthy and a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), in order to study the fate of atmospheric depositions of sulfur and nitrogen compounds. The mean δ15N of the needles ranged between −3.7 and −2.1 ‰ and for δ34S a range between −0.4 and +0.9 ‰ was observed. δ34S and sulfur concentrations in the needles of both stands increased continuously with needle age and thus, were closely correlated. The δ15N values of the needles showed an initial decrease followed by an increase with needle age. The healthy stand showed more negative δ15N values in old needles than the declining stand. Nitrogen concentrations decreased with needle age. For soil samples at both sites the mean δ15N and δ34S values increased from −3 ‰ (δ15N) or +0.9 ‰ (δ34S) in the uppermost organic layer to about +4 ‰ (δ15N) or +4.5 ‰ (δ34S) in the mineral soil. This depth-dependent increase in abundance of 15N and 34S was accompanied by a decrease in total nitrogen and sulfur concentrations in the soil. δ15N values and nitrogen concentrations were closely correlated (slope −0.0061 ‰ δ15N per μmol eq N gdw −1), and δ34S values were linearly correlated with sulfur concentrations (slope −0.0576 ‰ δ34S per μmol eq S gdw −1). It follows that in the same soil samples sulfur concentrations were linearly correlated with the nitrogen concentrations (slope 0.0527), and δ34S values were linearly correlated with δ15N values (slope 0.459). A correlation of the sulfur and nitrogen isotope abundances on a Δ basis (which considers the different relative frequencies of 15N and 34S), however, revealed an isotope fractionation that was higher by a factor of 5 for sulfur than for nitrogen (slope 5.292). These correlations indicate a long term synchronous mineralization of organic nitrogen and sulfur compounds in the soil accompanied by element-specific isotope fractionations. Based on different sulfur isotope abundance of the soil (δ34S=0.9 ‰ for total sulfur of the organic layer was assumed to be equivalent to about −1.0 ‰ for soil sulfate) and of the atmospheric SO2 deposition (δ34S=2.0 ‰ at the healthy site and 2.3 ‰ at the declining site) the contribution of atmospheric SO2 to total sulfur of the needles was estimated. This contribution increased from about 20 % in current-year needles to more than 50 % in 3-year-old needles. The proportion of sulfur from atmospheric deposition was equivalent to the age dependent sulfate accumulation in the needles. In contrast to the accumulation of atmospheric sulfur compounds nitrogen compounds from atmospheric deposition were metabolized and were used for growth. The implications of both responses to atmospheric deposition are discussed.

Caesium-137 estimates of erosion in agricultural areas

Sediment redistribution within near-level agricultural fields in the Gray Wooded soil zone of Saskatchewan was studied using the artificial environmental tracer caesium-137 (137Cs). the objective of this study was to estimate erosion rates caused by wind erosion, and land clearing techniques (i.e. bulldozing). Net rates of erosion and deposition were quantified over the past 30 years on three fields. Wind erosion was estimated to be approximately 1.0 t ha−1 y−1 on a near-level field, with 50 per cent of the sampling sites having erosion rates in excess of soil formation. Bulldozing produced median net sediment flux values of between 40 and 90 t ha−1 y−1. in addition, between 65 and 85 per cent of the sampling sites had erosion rates in excess of the maximum tolerable limit (i.e. 11.0 t ha−1 y−1). These results indicate significant accelerated erosion results from land clearing techniques used in central Saskatchewan. Bulldozing of the fields removed the LFH-horizon and exposed the underlying mineral horizon. Bulk densitites of the 0 to 15 cm layer in the cleared fields were 27 to 55 per cent greater than the comparable depth increment within the undisturbed forest site. Organic carbon concentrations within the 1930s, 1979, and 1987 fields were decreased by 47, 42, and 37 per cent, respectively following cultivation and bulldozing. Decreases in total nitrogen for the cultivated fields ranged from 33 to 38 per cent.

Non-biotic synthesis of organic polymers on H 2S-rich sea-floor: a possible reaction in the origin of life

In continuous observations of the anoxic, H 2S-rich floor of the brackish Lake Nakanoumi, ammonia alone was observed to decrease remarkably without a corresponding decrease of total nitrogen or increase of nitrite and nitrate. This newly observed phenomenon cannot be interpreted by conventional physical or biological reactions; it possibly suggests a new chemical synthesis of particulate amino acid on the anoxic lake floor in the presence of hydrogen sulphide. To understand the mechanisms of these results, we carried out some model experiments using hydrogen sulphide as a reagent. In these experiments, we found a new non-biotic synthesis of organic polymers containing amino acids from the reaction of hydrogen sulphide and a mixture of ammonium formate, formaldehyde and magnesium chloride in water at room temperature. This reaction is possibly based on the reduction and dehydration by hydrogen sulphide. This entirely new non-biotic synthesis is an important reaction to consider as the first stage of the origin of life.

Twospotted Spider Mite (Acari: Tetranychidae) Infestations on Soybeans: Effect on Composition and Growth of Susceptible and Resistant Cultivars

Effects of feeding of the twospotted spider mite, Tetranychus urticae Koch, on leaf and seed composition and dry matter accumulation in two soybean, Glycine max (L.) Merr., cultivars previously found to respond differently to mite infestation were investigated to gain a greater understanding of resistance mechanisms in soybeans to this wide host range plant pest. The two soybean cultivars, ‘Bonus’ and ‘Williams’, were infested with mites at the V3, V6, and R2 stages of development with 0, 10, and 200 mites per first fully expanded trifoliolate leaf. A relatively greater reduction in dry matter accumulation was seen in ‘Williams’ than in ‘Bonus’ at the same mite population level on the foliage. However, mite population increase was significantly lower on ‘Williams’ than on ‘Bonus’. Increasing mite infestation levels caused a slight increase in total soluble sugars and starch and a small decrease in total nitrogen and phosphorus levels of the leaves of both cultivars. Mite infestation had no effect on composition of seeds. Increasing mite damage caused a large reduction (55.26%) in leaf chlorophyll content and an even more dramatic loss (79.3%) in leaf carotenoid content with a greater loss in ‘Williams’ at the low mite infestation level. Results of these studies indicated that at least part of the increased resistance of ‘Williams’ to damage from T. urticae was due to a greater hypersensitive response of ‘Williams’ to mite attack. This response increased oxidizing conditions in the leaves, resulting in an extensive loss of carotenoids and chlorophyll. Increased oxidizing conditions in ‘Williams’ decreased mite population increases to a greater extent than it decreased net photosynthesis (dry matter accumulation).

Total nitrogen and free amino acids in Morus alba stems from autumn through spring

During leaf senescence and abscission, total nitrogen in leaves of mulberry (Morus alba L. ev. Shin‐ichinose) declined substantially whereas total nitrogen in buds, bark and stem wood increased markedly, suggesting translocation of nitrogen from senescent leaves in the autumn. After leaf abscission the winter buds and stems remained almost unchanged with respect to fresh and dry weight and total nitrogen until bud break in spring. In burst buds these parameters then increased drastically during the new growth while they decreased markedly in stems. Free arginine in the stem bark accumulated in parallel with the accumulation of total nitrogen in buds and stems in the autumn. Accumulation of proline in the wood, bark and buds also started in October but continued even after leaf‐fall, increasing until mid‐January (wood), mid‐February (bark) and the new growth (buds). Prior to and in the early stage of bud break, proline in bark and wood decreased significantly and arginine in stem bark decreased slightly. Simultaneously, proline and arginine in the dormancy‐releasing buds and asparagine, aspartic acid and glutamic acid in the buds and stems increased appreciably, suggesting that this increase in free amino acids was mainly derived from free amino acids (proline and arginine) stored in stems. The resulting marked decrease in total nitrogen and the drastic increase in asparagine in the stems and sprouting buds/new shoots were primarily due to a breakdown of protein stored in stems.

Changes in nitrogen levels and free amino acids in rooting cuttings of mulberry (Moms alba)

Total and protein nitrogen in bark and wood of parent stems of mulberry (Morns alba L. cv. Ichinose) decreased readily and to the same extent during leafing‐out of the buds, but the decrease in wood was less marked than in bark. Simultaneously, soluble nitrogen in both bark and wood also declined but the depletion was less marked than that of total and protein nitrogen. During the same period total nitrogen in the new shoots and adventitious roots increased drastically; however, the increase in total nitrogen in the growing parts during rooting was almost the same as the decrease in total nitrogen in the parent stems. Proline, the prevalent amino acid in wood and bark of the parent stems, decreased drastically during rooting, whereas during the same period asparagine in the developing buds, callus and adventitious roots increased markedly and became the predominant amino acid. The amount of arginine was relatively high in bark of the parent stems but Low in wood and the buds. The level of arginine in bark decreased considerably during the experiments (as did that of proline). The results suggest that the nitrogen required by the growing parts (sinks) in the rooting cuttings comes mainly from protein breakdown in bark of the parent stems (source), although stored protein in wood (source) and soluble nitrogen in bark and wood (sources) also play a part in storage of nitrogen. Asparagine is suggested to be the main nitrogen transport compound in the new growth of the tree and the initiating roots of cuttings.

Der Abbau der Epidermis-Proteine der Raupe Galleria mellonella mittels der durch den entomophagen Pilz Beauveria bassiana sezernierten toxischen proteolytischen Enzyme : The Degradation of the Cuticle Proteins of Greater Wax Moth Larvae ( Galleria mellonella) by Toxic Proteolytic Enzymes, Secreted by the Entomophagous Fungus Beauveria bassiana

Summary Cultivation media of the entomophagous fungus Beauveria bassiana, containing two proteolytic enzymes, were applied to purified cuticles of Galleria mellonella larvae. As seen from the results, the proteolytic enzymes (with the pH. optima 5 and 8) acted as toxins to Galleria mellonella larvae, on the one hand, and on the other hand, as enzymes which degrade the cuticle proteins. This was demonstrated both qualitatively by staining in situ the individual cuticle components and quantitatively by the decrease of total nitrogen in the substrate in dependence on time, as well as by the increase in amino nitrogen in the reaction medium.

The Change in Arginine Levels and the Metabolism of Urea and Ornithine in Cucurbita moschata Seedlings

AbstractDuring germination a decrease in both soluble and protein argmine occurs in pumpkin cotyledons (Cucurbita moschata Poir.) and this decrease parallels the decrease in total nitrogen. Arginine is readily metabolized to urea and ornithine and the metabolism of the latter compounds were studied by allowing cotyledons of intact plants to absorb urea−14C and by incubating cotyledon discs with ornithine‐2−14C. Of the urea absorbed, 90 % of the label was metabolized to 14CO2 with little free urea remaining in the plant. Urease activity in the cotyledons reached a maximum at 4 to 6 days of germination. Ornithine was extensively metabolized with 37 % of the label being incorporated into protein by 3 h. Soluble and protein arginine accounted for 23 % of the label suggesting that Krebs‐Henseliet cycle enzymes were present.

Alterations in tissue and serum aldolase in rabbits due to vitamin E deficiency.

SummaryDystrophic rabbit muscle showed a decrease in total nitrogen, noncollagen nitrogen (NCN), dry weight and dry fat-free weight (DFF wt). Collagen nitrogen and the fat content of the tissue were found to be increased over that seen in the controls. Livers of E-deficient animals displayed a 40% rise in total nitrogen and NCN versus normals. Aldolase activity was markedly decreased in dystrophic muscle, but liver revealed an elevation in its enzyme concentration compared to controls. The elevation of serum aldolase in E-deficient rabbits preceded and paralleled the creatinuria associated with the development of dystrophy by a period of 1 to 2.5 weeks. These conclusions were compared to those observed in other forms of muscle wasting.

Proline Accumulation in Wilted Ladino Clover Leaves1

Ladino clover plants were allowed to wilt in the field and in the greenhouse to determine the effects of wilting on soluble nitrogen compounds. Wilting caused a slight decrease in total nitrogen but little change in amount of soluble nitrogen. A large increase in free proline occurred in all wilted leaves. Free asparagine was abundant in unwilted leaves but varied considerably during wilting. Other free amino acids occurred in small amounts. Only traces of glutamine were found.Two light intensities were used in the greenhouse experiment. During severe wilting, the higher intensity stimulated proline synthesis. The results suggest that proline accumulation during wilting is influenced by available carbohydrate.The results of these experiments show that marked changes in free nitrogen compounds occur during wilting. These changes may aid in conserving nitrogen and carbon during moisture stress.

SIGNIFICANCE OF CHANGES IN HEXOSAMINE AND IN NITROGEN IN THE DIGESTA OF THE ALIMENTARY TRACT OF THE SHEEP.

Previous work had shown that the method of killing an animal affected the integrity of the mucosa of its digestive tract and as a consequence the content of nitrogen in the digesta.In the contents of the abomasum and the small intestine (divided into 4 equal lengths) of a group of sheep shot and bled and in another group anæsthetized and bled it was found that total nitrogen and hexosamine concentrations in the dry matter of the digesta or in relation to the dietary lignin as a marker rose considerably from the abomasum to the first quarter of the small intestine. The increase in hexosamine was less than that of total nitrogen. After the first quarter of the small intestine a decrease in total nitrogen was observed distally, but the proportion of hexosamine increased. In a third group of sheep from which the contents were obtained under anæsthesia alone the increments, both of total nitrogen and hexosamine, were less. In conscious sheep on the same kind of diet and fitted with cannulas, similar but smaller changes were found.Mucoprotein is probably the main source of hexosamine in the proximal zone of the small intestine but distally microbial cell wall polysaccharides containing glucosamine become a considerable source.The condition of the animal at the time of sampling greatly affects the significance to be attached to the nitrogenous constituents of the digesta.

Extraction of Fibrillar and Sarcoplasmic Proteins of Turkey Musclea

SUMMARYProtein extraction and fractionation was carried out on samples of breast and leg muscles of turkey males 11–32 weeks old. Nitrogen determinations were made on the total, extractable, coagulable, actomyosin, myosin, and sarcoplasmic protein fractions. These components respectively contained 4.27, 2.57, 1.96, 0.53, 0.09, and 1.36 g nitrogen per 100 g of muscle (wet weight). Nitrogen values were higher for light muscle than for dark muscle.Muscle samples were taken from 21–36‐week‐old turkey males both before and after 48 hr at 5–10°C. Results showed a 4.9% decrease in total nitrogen and a 3.4% increase in non‐protein nitrogen.Amounts of protein fractions were compared between birds of three age groups. Birds within the 25–32‐week‐old group gave highest values for all fractions estimated with the exception of total nitrogen. Turkeys ranging in age from 21–26 weeks gave the highest values for this component. Extractable, coagulable, and nonprotein values increased with increasing age; the 11‐week‐old turkeys gave the lowest values.

STUDIES ON THE INTRACELLULAR WATER, SODIUM AND POTASSIUM IN THYROTOXIC MYOPATHY AND IN THYROTOXIC PERIODIC PARALYSIS

Biochemical analysis of intracellular water, sodium, potassium and nitrogen in biopsied muscle was attempted in 24 thyrotoxic myopathy, in 10 thyrotoxic periodic paralysis and in 19 control subjects. Water and electrolytes studies were done by chloride assumption.1. Serum electrolytes in all groups remained in normal range except remarkable fall of potassium during paralytic attack of thyrotoxic periodic paralysis.2. In thyrotoxic myophathy, total and intracellular water in solid tissue basis decreased by 11.6% and 12.9% respectively, through no significant alteration was observed in thyrotoxic periodic paralysis during either paralytic or non-paralytic state.3. Intracellular sodium content and concentration in muscle specimen increased in thyrotoxicosis and in thyrotoxic periodic paralysis during non-paralytic state. Intracellular potassium, in reverse, decreased significantly in either thyro toxicosis or during paralytic attack of thyrotoxic periodic paralysis. However in non-paralytic state intracellular potassium concentration did not differ significantly from control subjects.4. Since decrease of total nitrogen in biopsied specimen (10.4%) limited by half of the decrease of intracellular potassium (20.8%), this potassium depletion was not the result by muscle destruction.5. Linear correlation between grip strength and intracellular potassium concentration of biopsied muscle was proved in thyrotoxic myopathy.

Studies on Nitrogen Tie‐Up as Influenced by Location of Plant Residues in Soils

AbstractIn field experiments it has been observed that nitrogen availability to corn is frequently depressed where crop residues low in nitrogen remain on the soil surface as compared to where the residues are incorporated in the soil. The purpose of this investigation was to evaluate the immobilization of soil nitrogen as influenced by position of crop residue with reference to the soil.In greenhouse experiments nitrogen uptake by Sudangrass was significantly greater when cornstalk residue was applied to the soil surface than when it was incorporated in the soil. By comparison with a treatment receiving no residue it was concluded that considerable nitrogen was immobilized by cornstalk residue incorporated in the soil, whereas no immobilization occurred with cornstalk residue on the soil surface.On the other hand, in laboratory experiments it was demonstrated that soil nitrogen could be moved to and immobilized in low‐nitrogen residue on the soil surface and that the movement of nitrogen into surface residue was enhanced in treatments which were subsurface irrigated and in treatments held at a low‐air humidity. Also it was found in laboratory experiments that subsurface residue decomposed more rapidly than did surface residue and that this more rapid decomposition resulted in an increase in percent nitrogen but in a decrease in total nitrogen of the residue. Likewise, percent nitrogen of surface residue increased, but total nitrogen increased or decreased, depending upon the conditions of the experiment.The results of a field experiment demonstrated that surface applications of low‐nitrogen residue without added nitrogen fertilizer resulted in decreased nitrogen uptake by corn and yield of corn. However, when nitrogen fertilizer was added along with the residue, yields were increased above the unmulched check.

Nitrogen Loss in Gaseous Form from Soils as Influenced by Fertilizers and Management

AbstractThe experiments reported here were aimed to ascertain the magnitude of gaseous loss of nitrogen in Spencer silt loam under greenhouse conditions, as affected by pH, form of nitrogenous fertilizer, energy material, and cropping. Four additions of 150 ppm. nitrogen each were made to both cropped and uncropped soils; four successive oat crops were grown on the former.At field moisture levels large volatile losses of nitrogen occurred from the uncropped soil regardless of treatment. Over an 11‐month period these losses ranged from 35% in the soil at pH 5.5 amended with straw and nitrogen as (NH4)2SO4 to 72% in the soil at pH 6.5 with (NH4)2SO4 but no straw. In soils similarly treated and subsequently cropped with oats, the losses were between 7 to 8%.In other experiments the levels of NO3, NH4, and total N in the uncropped Spencer silt loam at pH 6.5 were measured 8 times during a 1‐year period. Irrespective of the form of nitrogen added, presence or absence of straw, and whether liming occurred at the time of fertilization or 12 weeks earlier, the greatest decrease in total nitrogen occurred during the first 6 weeks after fertilization and thereafter remained more or less constant over the year. Approximately one‐half of the 300 ppm. nitrogen added was volatilized from the soil under each treatment. Concurrent increases in nitrate nitrogen levels occurred without exception.