High Nitrate Accumulation Research Articles

Effects of Nitrogen and Cycocel Application on Soil Nitrate Pollution and Agronomic Characters of Rice (Oryza sativa L.)

Nowadays, due to the effective role of nitrogen fertilizer in growth, yield and crop quality, farmers apply large amount of chemical fertilizers. High application of nitrogen fertilizers has caused soil and water pollution and environmental dangers, higher nitrate accumulation in plant, and different disease risks in human and livestock. In order to investigate the effects of nitrogen and cycocel application effects on soil nitrate pollution and agronomic traits of rice, an experiment was arranged in split plot based on a completely randomized block design with three replicates at Sari region (north of Iran) in 2010. The main factor was nitrogen in four levels and cycocel was considered as a sub factor in three levels. Results showed that maximum and minimum plant height and fourth internodes bending moment were obtained in 0 and 150 kg N ha, respectively. Higher filled spikelet percentage per panicle, grain yield and harvest index were obtained in 100 kg N ha application. Application of N up to 150 kg N ha increased soil nitrate by 44.7 percent. As cycocel application decreased, the plant height and panicle length were reduced, but tiller number per plant, filled spikelet percentage per panicle, and grain yield were increased.

Response of Nitrate Metabolism in Seedlings of Oilseed Rape (Brassica napus L.) to Low Oxygen Stress

In order to understand the response of nitrate metabolism in seedlings of oilseed rape (Brassica napus L.) to low oxygen stress (LOS), two cultivars were studied at different light, LOS time and exogenous nitrate concentrations under hydroponic stress. Results show that N-uptake and dry matter of rape seedlings were decreased after LOS stress while nitrate accumulation (NA) under LOS was induced by darkness. Nitrate accumulation peaked at 3 d while root activity (RA, defined as dehydrogenase activity) decreased with prolonged waterlogging exposure. Exogenous nitrate significantly elevated NA and RA. Tungstate (TS) and LOS inhibited nitrate reductase (NR) activity while NR transcription and activity were enhanced by exogenous nitrate. Low oxygen stress stimulated the activity of superoxide dismutase (SOD) and peroxidase (POD) slightly, but inhibited that of catalase (CAT). B. napus L. Zhongshuang 10 (ZS10), a LOS tolerant cultivar, displayed smaller decrease upon dry matter under LOS, higher NA in darkness and lower NA in light than B. napus L. Ganlan CC (GAC), a LOS sensitive variety. ZS10 had lower NA and higher RA after waterlogging and exogenous nitrate treatment, and higher NR activity under TS inhibition than GAC, but the activity of antioxidant enzymes did not change under LOS. The results indicate that nitrate metabolism involved tolerance of rape seedlings to LOS, with lower accumulation and higher reduction of nitrate being related to higher LOS tolerance of rape seedlings exposed to waterlogging.

Cover‐crop seeding‐date influence on fall nitrogen recovery

AbstractPlanting cover crops after corn‐silage harvest could have a critical role in the recovery of residual N and N from fall‐applied manure, which would otherwise be lost to the environment. Experiments were conducted at the University of Massachusetts Research Farm during the 2004–2006 growing seasons. Treatments consisted of oat and winter rye cover crops, and no cover crop, and four cover‐crop dates of planting. The earliest planting dates of oat and winter rye produced the maximum biomass yield and resulted in the highest nitrate accumulation in both cover‐crop species. The average nitrate accumulation for the 3 years in winter rye and oat at the earliest time of planting was 60 and 48 kg ha–1, respectively. In 2004 where the residual N level was high, winter rye accumulated 119 kg nitrate ha–1. While initially soil N levels were relatively high in early September they were almost zero at all sampling depths in all plots with and without cover crops later in the fall before the ground was frozen. However, in plots with cover crops, nitrate was accumulated in the cover‐crop tissue, whereas in plots with no cover crop the nitrate was lost to the environment mainly through leaching. The seeding date of cover crops influenced the contribution of N available to the subsequent crop. Corn plants with no added fertilizer, yielded 41% and 34% more silage when planted after oat and rye, respectively, compared with the no–cover crop treatment. Corn‐silage yield decreased linearly when planting of cover crops was delayed from early September to early or mid‐October. Corn‐ear yield was influenced more than silage by the species of cover crop and planting date. Similar to corn silage, ear yield was higher when corn was planted after oat. This could be attributed in part to the winter‐kill of oat, giving it more time to decompose in the soil and subsequent greater release of N, while the rapidly increasing C : N ratio of rye can lessen availability to corn plants. Early plantings of cover crops increased corn‐ear yield up to 59% compared with corn‐ear yield planted after no cover crop.

Spatiotemporal changes of nitrate and Vc contents in hydroponic lettuce treated with various nitrogen-free solutions

Nowadays, off-season leafy vegetables are generally characterized by low vitamin C (Vc) content and high nitrate accumulation due to low light intensity inner protected systems and high-level nitrogen supply. A glasshouse experiment was conducted to investigate the effects of three kinds of nitrogen-free solution treatments before harvest on Vc and nitrate contents in expanded leaf blades, expanded leaf petioles and old leaves of hydroponic lettuce. The results showed that using nitrogen-free solutions could decrease nitrate contents of expanded leaf blades, expanded leaf petioles and old leaves, also nitrate contents in above parts reduced increasingly with treatment time extending. In addition, three nitrogen-free solution treatments increased the Vc content of expanded leaf blades instead of expanded leaf petioles and old leaves. There were instead of significant positive correlations between nitrate contents but Vc contents of expanded leaf blades, expanded leaf petioles and old leaves. To conclude, nitrogen disruption treatment before harvest could effectively reduce nitrate contents in edible parts of lettuce, and also improve Vc content in expanded leaf blade.

Influence of nitrogen form, growing season and sulfur fertilization on yield and the content of nitrate and vitamin C of broccoli

The objective of this study was to determine the effects of nitrogen (N) sources, sulfur (S) and growing seasons on yield and the content of nitrate and vitamin C of broccoli ( Brassica oleracea L. spp. Italica). Three N fertilizers (ammonium sulfate, ammonium nitrate and urea) were side-dressed while two levels of sulfur (0.0 and 0.5%) were sprayed on broccoli plants grown in both spring and fall-winter seasons. Here, we report on the interaction between N-source and S supply, yield, and nitrate content and discuss the relevance of this interaction in relation to crop-management strategies under different growing seasons. In the fall-winter season, broccoli yield of “Sultan F1”, “Majestic F1” and “Marathon F1” were 21.23%, 128.52% and 88.53% higher than spring season. Furthermore, S application increased the yield by 9% average over growing seasons, cultivars and N-forms. Also, application of urea as N-source decreased the yield by approximately 13–15% than other N-sources. High curd nitrate accumulation was attributed with spring season and “Marathon F1”, however, less accumulation was found in fall-winter season and “Majestic F1”. Fertilizers containing N forms that not ready available to the crop, i.e. ammonium sulfate and urea, decreased nitrate than fast N-release fertilizer (ammonium nitrate), but their effect on the yield was different. Highest yield with low content of nitrate was achieved when ammonium sulfate combined with sulfur were used during fall-winter season, especially in cv. “Marathon F1”. N-source and sulfur application had no effect on vitamin C, conversely, it was affected by growing season and tested genotypes. Therefore, additions of ammonium sulfate and sulfur application in the field of broccoli were essential to produce higher yield with good quality curds that pose minimum health risk to human.

Impact of protozoan grazing on nitrification and the ammonia- and nitrite-oxidizing bacterial communities in activated sludge

In activated sludge, protozoa feed on free-swimming bacteria and suspended particles, inducing flocculation and increasing the turnover rate of nutrients. In this study, the effect of protozoan grazing on nitrification rates under various conditions in municipal activated sludge batch reactors was examined, as was the spatial distribution of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) within the activated sludge. The reactors were monitored for ammonia, nitrite, nitrate, and total nitrogen concentrations, and bacterial numbers in the presence and absence of cycloheximide (a protozoan inhibitor), allylthiourea (an inhibitor of ammonia oxidation), and EDTA (a deflocculating agent). The accumulations of nitrate, nitrite, and ammonia were lower in batches without than with protozoa grazing. Inhibition of ammonia oxidation also decreased the amount of nitrite and nitrate accumulation. Inhibiting protozoan grazing along with ammonia oxidation further decreased the amounts of nitrite and nitrate accumulated. Induction of deflocculation led to high nitrate accumulation, indicating high levels of nitrification; this effect was lessened in the absence of protozoan grazing. Using fluorescent in situ hybridization and confocal laser scanning microscopy, AOB and NOB were found clustered within the floc, and inhibiting the protozoa, inhibiting ammonia oxidation, or inducing flocculation did not appear to lower the number of AOB and NOB present or affect their position within the floc. These results suggest that the AOB and NOB are present but less active in the absence of protozoa.

Soil Nitrogen and Nutrient Dynamics after Repeated Application of Treated Dairy‐Waste

Improved understanding of the effects of dairy‐waste treatment and land application on microbial processes and products is required to predict the outcome of waste applications and avoid undesirable environmental impacts. Our objective was to assess effects of treated dairy‐waste on soil N pools, nitrification, plant N availability, and yield in a silage cornfield (Zea mays L.) treated with ammonium sulfate (AS), dairy‐waste compost (DC), or liquid dairy‐waste (LW) as N sources at two levels of application over 5 yr. Increases in soil C and N, nitrate, and available P and K were observed for the DC treated soils throughout the 5‐yr period. Soil organic C increases for the high‐level DC treated soil doubled the C pool resulting in an increase of 14 Mg C ha−1 The highest nitrate accumulation was at the 60‐ to 90‐cm depth for soils receiving high level of DC (200 kg N ha−1), which moved to lower depths in subsequent years. Soils receiving a high‐level of DC or LW showed a three‐fold increase in nitrifier activity compared with the control. There was a positive silage corn yield response with all the treatments, with DC having the highest yields. While N from AS and LW are available for plant uptake almost immediately, the organic N in compost continued to mineralize throughout the growing season, after harvest and in subsequent years. Careful management of application rates to optimize the timing of N release versus plant demand and of post‐harvest nutrient pools are suggested for the prevention of excessive nitrate accumulations and movement from repeated dairy‐waste applications.

The Mechanism of Nitrate Accumulation in Pakchoi [Brassica Campestris L.ssp. Chinensis(L.)

Decreased nitrate in vegetables can improve crop nitrogen utilization efficiency and lessen the human health risk caused by the reduction of nitrate to nitrite in vegetables. This paper studied the mechanisms of differences in nitrate accumulation and distribution within organs of two cultivars of pakchoi (Brassica campestris L.ssp. Chinensis (L.) previously screened in hydroponic experiments from 12 cultivars popularly grown in China at present. The two typical cultivars used in this experiment were Shanghaiqing with low nitrate accumulation and Liangbaiye 1 with high nitrate accumulation. There was no significant difference of total nitrate uptake but a significant difference in nitrate content existed between the two cultivars. Compared with Liangbaiye 1, Shanghaiqing showed a significantly higher photosynthetic rate and nitrate reductase activity. Determination of nitrate concentration (activity) in vacuoles with double-barrelled nitrate-selective microelectrodes showed that Shanghaiqing had lower vacuolar nitrate activity than Liangbaiye 1. Two putative nitrate reductase genes, nia1 and nia2, were amplified from the leaf blades of these two cultivars. Nia1 mRNA fragments (887 bp, accession numbers DQ082868 and DQ082869) were amplified using degenerate primer and nia2 mRNA fragment was amplified using one pair of generate primers designed according to DQ001901. Sequence analysis of DQ082868 and DQ082869 both showed 97% and 87% similarity with two nitrate reductase mRNA sequences of Brassica napus, accession numbers D38219 and D38220, respectively. The results of real time PCR to compare the relative expression of the putative nitrate reductase genes (nia1 and nia2) showed that Shanghaiqing had significantly higher expression level than Liangbaiye 1 and nia2 was significantly higher than nia1 in leaf blade and petiole. Both the nitrate reductase activity and the relative expression level of nia1 were in the order of leaf blade > root > petiole, while that of nia2 was leaf blade > petiole > root. There was no statistically significant difference of nitrate activity stored in vacuoles between the different organs of the two cultivars. It can be concluded that Shanghaiqing took up slightly less nitrate, but had significantly higher nitrate reductase activity in cytosol and had a higher relative expression of the putative nitrate reductase genes than Liangbaiye 1; this leads to the fact that Shanghaiqing has a lower nitrate content than Liangbaiye 1.

Over-expression of potato virus X TGBp1 movement protein in transgenic tobacco plants causes developmental and metabolic alterations

Transgenic Nicotiana tabacum plants expressing the TGBp1 movement protein of potato virus X (PVX) were studied to investigate the effects caused by this protein on plant physiology and development. TGBp1 caused consistent reductions of size and weight in different organs of these plants; however shoot-to-root ratios were similar to those of control plants. Transgenic seedlings showed smaller root meristems and calli derived from TGBp1 leaves grew at a slower rate through successive subcultures. Microscopic observations of TGBp1 plants revealed flattened chloroplasts containing plastoglobuli-like bodies. Further analyses showed a considerable reduction in photosynthetic rate, lower starch levels in leaves and roots, higher nitrate accumulation in leaves and induction of pathogenesis-related (PR) protein genes. Since these changes were not observed when other PVX sequences were expressed in tobacco, we postulate that TGBp1 is an important symptom contributor in PVX infections.

Nitrification and Nitrobacter in coniferous forest soils.

The nitrification of three coniferous forest soils was investigated: a podzol (Fontainebleau, France) with low N deposition and no nitrate accumulation, an acid mull (Haldon, UK) with low N deposition and moderate nitrate accumulation, and a podzol (Wekerom, The Netherlands) with high N deposition and high nitrate accumulation. Twenty-one months in situ lysimeter experiments and short-term and long-term in vitro incubations were performed to respectively establish the status of NO 3 - accumulation and potential nitrification of these soils. These complementary approaches allowed to conclude that the absence of NO 3 - accumulation in Fontainebleau soil was effectively due to a lack of nitrifing activity in the whole profile while the high NO 3 - accumulation observed in the Wekerom soil essentially resulted from an active nitrifying activity in the Oh horizon of this soil. For the Haldon soil, the inadequacy between the lysimeter and the short-term in vitro experiment was discussed. Surprisingly, relatively high densities of the nitrite-oxidiser Nitrobacter (enumerated by PCR-MPN technique) were found in all the studied horizons of the three soils. Moreover, a long-term incubation experiment showed that inhibition of nitrification in the Oh Fontainebleau soil could be removed after submitting the soil samples to constant conditions during 82 days. This demonstrates that in these soils, ammonium-oxidisers (as well as nitrite-oxidisers) are present and that extrinsic factors were involved in the inhibition of nitrification.

Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.

Five genotypes of Brachiaria spp. were planted in a field experiment with and without nitrate fertilization. Nitrogen metabolism was evaluated by measurements of nitrate reductase (NR) activity in leaves, nitrate accumulation in stems, and nitrogenase activity and dentrification in intact soil–plant cores. There were differences between genotypes in all parameters and a tendency was observed for genotypes with high NR activity and nitrate accumulation to have low nitrogenase activity and vice versa. Brachiaria radicans (Tanner grass) was representative for the first type and B. ruziziensis (CPI 30623) for the second. Denitrification reached 7% of the applied N within 63 h and was lowest in Tanner grass and highest in B. brizantha (FL 902-4). Brachiaria ruziziensis (CPI 30623) plants were able to withstand N stress better than B. radicans as a consequence, possibly, of differences in nitrogenase activity.

Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.

Five genotypes of Brachiaria spp. were planted in a field experiment with and without nitrate fertilization. Nitrogen metabolism was evaluated by measurements of nitrate reductase (NR) activity in leaves, nitrate accumulation in stems, and nitrogenase activity and dentrification in intact soil–plant cores. There were differences between genotypes in all parameters and a tendency was observed for genotypes with high NR activity and nitrate accumulation to have low nitrogenase activity and vice versa. Brachiaria radicans (Tanner grass) was representative for the first type and B. ruziziensis (CPI 30623) for the second. Denitrification reached 7% of the applied N within 63 h and was lowest in Tanner grass and highest in B. brizantha (FL 902-4). Brachiaria ruziziensis (CPI 30623) plants were able to withstand N stress better than B. radicans as a consequence, possibly, of differences in nitrogenase activity.

Inheritance of Nitrate Accumulation in Lettuce1

Abstract F2 generation of lettuce crosses (Lactuca sativa L.) involving 2 low and 3 high nitrate accumulating cultivars indicated a few major genes were responsible for the control of high or low nitrate accumulation. The segregation of low × high crosses suggested that the 2 low accumulators had different genotypes. Low nitrate accumulation could be explained by dominant complementary epistasis in ‘Valmaine’ and a single dominant gene in ‘Wonder Van Voor-burg’. The F2 segregation of ‘Valmaine’ × ‘Wonder Van Voorburg’ cross confirmed the geno-typic differences. Recessive genes controlled high nitrate accumulation.

Using forage crops to reduce nitrate accumulation in hula peat soils

A two-year field experiment was made of growing Rhodes grass and alfalfa on peat soil of the Hula Valley, where high nitrate accumulation occurs under row crops or plantless soil and leads to the danger of contamination of Lake Kinneret. The aime of the investigation was to use these perennial high-nitrogen-consumer crops to prevent the nitrate accumulation in the peat soil. The results showed a drastic decrease in soil N-NO3 under both species in two irrigation systems obtaining high dry matter yields with high plant nitrogen content without the use of any nitrogen fertilizer.

Nitrate Accumulation in Rye, Tall Fescue, and Bermudagrass as Affected by Nitrogen Fertilization1

AbstractThis study was undertaken because of the need for additional information on nitrate accumulation in bermudagrass (Cynodon dactylon), tall fescue (Festuca arundinacea), and rye (Secale cereale) grown under comparable field conditions with varying rates of N fertilizer. Nitrogen levels employed were 0, 100, 200, 300, and 400 kg/ha/year, applied at several dressings throughout the growing season. Nitrate content in the herbage, determined by an enzymatic method, was studied during two growing seasons to ascertain whether potentially toxic levels are likely to occur under pasture conditions.Provided that as much as 30 days elapsed between fertilization and harvest, NO3‐N levels were low at all rates of N from 0 through 67 kg/ha per application. Higher rates and/or shorter growth intervals frequently resulted in levels in the 700 to 2,000 ppm range or higher for rye and tall rescue, but not for bermudagrass.Tall rescue accumulated more nitrate than did bermudagrass, both in association and when they were in pure stands. Rye also contained more nitrate than did bermudagrass. High nitrate content occurred only with high total‐N levels, but high total‐N did not always lead to excessive nitrate accumulation. The likelihood of high nitrate accumulation appears less likely with the passage of time after fertilization, indicating the need to appropriately harmonize fertilization and grazing schedules.

Relations between soil management and the quality of surface- and groundwater supplies

1. Urban and industrial waste waters, farm effluents, soil and fertilizer born nitrate and phosphate may impair the water quality in streams, groundwater bodies and lakes by oxygen deprivation and high salt contents, nitrate accumulation and eutrophication. In this paper the hygienic aspect as well as the problem of urban waste disposal were left aside, only the influence of farming upon the water quality has been discussed. 2. Farm effluents include liquid manure, manure piles runoff and silo effluents which are too concentrated and carry too high a BOD load to allow processing in treatment plants. Parts of these liquids may contaminate water courses, and enter sewage systems. Improved technology and economical help will be required to foster the safe utilization of these liquids on the land. 3. High nitrate contents in drinking water are known to have caused sometimes fatal methemoglobinemia in infants. In the Federal Republic 3.7% of the public water works supply water that contains more than 50 mg/l NO3. 4. Sources of nitrate are: urban and industrial waste waters, cesspools, farm effluents and the toplayer of cropland. Annual leaching losses of a few to 40 and more kg/ha N(NO3−) from the soil have been reported. The soil solution frequently contains nitrate concentrations in excess of the drinking water standard. 5. However, whether this will cause objectionable concentrations in drinking water supplies depends upon the share of cropland in an area and upon the local hydrological conditions. Management measures are available to partially cut nitrate leaching. 6. Phosphorus is the critical factor for eutrophication. In the watershed area of the Stockacher Aach which empties into the Lake Constance, the amount of phosphorus that originates from soils and fertilizers depends on petrographical and pedological conditions rather than upon management. Soil born phosphorus plays only a minor role in enhancing the eutrophication of the Lake. This may be different in other areas where rocks and soils do not contain limestone or where erosion is higher. 7. Nitrogen presently is not considered to be a limiting factor for the eutrophication of the Lake Constance, although the element is required for production. From a predominantly rural area most of the nitrogen input into the Lake is soil born. In 1963 it amounted to 112 t N(NO3−) from 242 km2. However there are also tributaries which carry high amounts of nitrogen that originates from urban wastes. 8. There exists no general answer as to the influence upon the quality of water supplies of farm effluents; soil born nitrate and phosphate. This rather has to be assessed according to the local conditions (share of cropland, types of soils and rocks, management, handling of farm wastes etc.) within a watershed area.