• Korean Journal of Environmental Agriculture
• /
• v.20 no.5
• /
• pp.340-345
• /
• 2001

High rates of nitrogen fertilization dangerously increase the nitrate content of vegetable crops, and the accumulation of nitrate in edible crops is undesirable because of potential risks to human health. Micronutrient solution containing Cu, Mn, Mo, Zn was tested for the suppression of nitrate accumulation in lettuce grown in pots treated with Mg fertilizer under a greenhouse condition. The micronutrient solution was sprayed on leaves at 3 and 4 weeks after transplanting of 20-day old seedlings. Plants were harvested after 5-week growth, and yield, contents of chlorophyll, sugar, micronutrient and nitrate, and also nitrate reductase activity were measured. Fresh weight of lettuce was significantly increased by the application of Mg and micronutrients, and the effect was the most significant in the Mg+micronutrient treatment. Also contents of chlorophyll and micronutrients were higher in the plants of micronutrient treatments. Contents of nitrate were reduced by about 14-18% in lettuce with Mg and/or micronutrient applications. Compared to the plants of control treatment, nitrate reductase activity was also higher in those plants treated with micronutrients, and in the treatment of Mg+micronutrients the enzyme activity was six times as high as that of control treatment. Although the effect of mineral nutrients on the suppression of nitrate accumulation in lettuce was relatively small in this study, an appropriate supply of mineral nutrients could be one of the solutions for the nitrate accumulation in vegetables.

• Korean Journal of Soil Science and Fertilizer
• /
• v.37 no.2
• /
• pp.91-96
• /
• 2004

Accumulation of nitrate in edible crops is undesirable due to potential risks to human health. Since nitrate has a role in the osmotic regulation of plants, salt accumulation in soil is expected to stimulate nitrate accumulation in plants. Lettuce (Lactuca sativa L.) was grown in soils of different salinities, 9.69 and $4.49dS\;m^{-1}$, in a greenhouse, and the effect of soil salinity on nitrate accumulation in lettuce was investigated. Content of nitrate in the lettuce increased significantly as soil salinity increased under low light intensity and ample supply of nitrate in root media. Soluble sugar and oxalate contents in lettuce were also significantly higher in the soil of higher salinity. Phosphate, Cl, and $SO_4$ contents in lettuce were not significantly different in soils of different salinities. Among the cations, K content in lettuce was significantly higher in the soil of higher salinity, but Na, Ca, and Mg comtents were not much influenced. Comparing to the lettuce grown in low salinity soil, although the growth of lettuce was decreased by 9% in the soil of higher salinity, nitrate accumulation in the lettuce was increased by 18.6%. These results indicate that higher nitrate content in lettuce of higher salinity soil is a positive accumulation to adapt to the water stress condition. The nitrate accumulation of vegetables grown in plastic film houses is known to be due to the heavy fertilization and low light intensity, but salt accumulation in the soil, which can lower soil water potential, is expected to stimulate the nitrate accumulation further.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.19 no.1
• /
• pp.81-88
• /
• 1999

A field experiment with 200, 400 and $600kg{\cdot}N/ha/year$ application levels was carried out to study the nitrate nitrogen accumulation and forage yield of sorghum sudangrass hybrid(Xtragraze II) at Iksan College Farm in 1995. The nitrate nitrogen contents were increased by the application of nitrogen and decreased as the plant matured, then the accumulation of nitrate nitrogen started from 200kg application, and exceeded the safe level of ruminants at the level of 400kg application during the whole growing period. In the early stage of growth, nitrate nitrogen contents of sorghum sudangrass hybrid were increased by rainfall during the dry season, but these contents are almost kept constantly at the low level in the later stage of growth. Accumulation of nitrate nitrogen in the morning had a greater tendency than that of the afternoon. A sum exceeding $200kg{\cdot}N$ does not necessarily result in increase the amount of nitrate nitrogen in sorghum sudangrass hybrid.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.7 no.3
• /
• pp.146-152
• /
• 1987

Sorghum cv. Pioneer 93 1, sorghum-sudangrass hybrid cv. Sioux and maize plant cv. Blizzard were assayed for toxic concentrations of nitrate-nitrogen ($NO_3$-N) and their relationship to morphological characteristics and environmental temperature in a field and phytotron trial. In the phytotron, sorghum and maize plants ranging from emergence to heading stage, were grown under different day/night temperatures of 30125, 25/20,28/18 and 1818 degree C. Nitrate-nitrogen in sorghum and maize plants was accumulated mainly in stems. Therefore nitrate concentration in the young plants was increased as development of stalks advanced and was highest at the stage of 3-4 leaves, when the plants had a leaf weight ratio 0.78-0.80 g/g plant weight. However, nitrate concentrations of the plant decreased as morphological development progressed, especially from the stage of growing point differentiation. Correlation coefficients showed a positive correlation of nitrate concentration with leaf weight ratio, leaf area ratio and specific leaf area, while plant height, dry matter percentage and absolute growth rate showed a negative association with TEX>$NO_3$-N ($P{\le}0.1$%). Cyanogenic glycosides, total nitrogen and crude protein were close associated with nitrate accumulation, and positively significant ($P{\le}0.1$%). High temperature over 30/25^{\circ}C.$ for 3 weeks increased N-uptake and dry matter accumulation, but reduced nitrate concentration. Under cold temperature below 18/8^{\circ}C.$ concentration of nitrate-N was increased in spite of its limited nitrogen uptake and plant growth.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.38 no.2
• /
• pp.196-200
• /
• 1993

A full understanding of the interdependence of leaf nitrate (($No_3$￣) metabolism and symbiotic nitrogen($N_2$) fixation in legume crops is needed to help maximize the use of both N sources as well as to improve forage quality through the inhibition of leaf nitrate accumulation. The present work examines the effects of added nitrate, the level of which are 0,2,4,8 and 12mM, on the nodule formation and leaf nitrate utilization and on the possibility of inducing nitrate-toxicity to livestocks in two alfalfa varieties, ' Vernal ' of grazing type and ' Victoria ' of hay type. Higher level of exogeneous nitrate resulted in the increased above-ground dry weight. Nodulation was inhibited severely when more than 8mM NO$_3$￣ was supplied to alfalfa plants, and leaf nitrate reductase reached a maximunm at 4mM nitrate supply. The $V_{max}$of nitrate reductase in leaves of Vernal was similar to that of Victoria, whereas the $K_m$ of Vernal was higher than that of Victoria. High accumulation of leaf nitrate, $4{\times}10^{-5}$ g/g leaf fresh weight, was shown at 12mM nitrate supply, which was thought to be not enough to induce nitrate-toxicity to livestocks.icity to livestocks.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.51 no.1
• /
• pp.107-111
• /
• 2006

This study was to verity that the uptake inhibition and accumulation of nitrogen in different potassium levels. Lettuce was used as model plant in this study and grown in pot of 10cm's in diameter and depth with mixture media of vermiculite and perlite under supply of different culture solution for three weeks. Nitrogen absorption at root was inhibited by increased potassium concentration in nutrient solution, and nitrate accumulation of plant was depended on absorption of nitrogen because nitrate content of 0 K level was 4-5 times higher than that of 2 K level, Concentration of ascorbic acid was decreased by increasing the nitrogen absorption, since ascorbic acid (AsA) content of 2K level was higher than those of OK level in both of old leaf and flesh leaf.

• Korean Journal of Soil Science and Fertilizer
• /
• v.38 no.1
• /
• pp.38-44
• /
• 2005

In addition to the variation in nitrate accumulation of vegetables due to environmental conditions, there is also a distinct genetic variation. The variation of nitrate accumulation in some cultivars of lettuce and spinach commonly cultivated in Korea was investigated. Ten cultivars for both lettuce and spinach were grown in plastic containers filled with a 1:1 mixture of perlite and vermiculite with application of Hoagland No. 2 nutrient solution of high nitrate content (17.3 mM N) in a greenhouse condition. Plants were harvested four weeks after transplanting four-leaf stage seedlings. Plant growth was measured by fresh and dry matter of shoot, and contents of nitrate and other inorganic ions and organic solutes including sugar, amino acids and organic acids were measured. Large and significant genotypical variations in the nitrate content of the plants were found for both lettuce and spinach, and high negative correlations between nitrate content and fresh or dry weight were found in lettuce and spinach. Variation in nitrate accumulation of lettuce and spinach cultivars was not directly related to the differences in contents of organic and inorganic solutes, and this result indicates that photosynthesis and osmotic regulation are not directly related with the nitrate accumulation. Considering the correlations between nitrate content and plant growth of this study, it can be simply suggested that different cultivars of lettuce and spinach have their own inherited growth and physiological characteristics and also optimum nitrogen level required for the growth. Therefore when available nitrogen in root media is higher than the optimum level required for the inherited growth potential, some of the excess nitrate supplied can be accumulated in plants.

• Korean Journal of Environmental Agriculture
• /
• v.25 no.4
• /
• pp.339-345
• /
• 2006

Accumulation of nitrate in green vegetables is undesirable due to potential risks to human health. Lettuce was cultivated in pots under greenhouse conditions with compost applications of 2,000 and 4,000 kg/10a, and the growth and nitrate accumulation of lettuce were compared with those found in the lettuce cultivated with chemical fertilizers of recommended levels. Content of $NH_4-N$ in the soils of compost applications were much lower than those found in the soil of chemical fertilizer application. Two weeks after lettuce transplant $NH_4-N$ was not found in the soils of compost applications, and in the soils of chemical fertilizers application $NH_4-N$ was not found three weeks after lettuce transplant. One week after lettuce transplant content of $NO_3-N$ was much higher in the soils of compost applications, and the contents were rapidly decreased. While, the content of $NO_3-N$ in the soil of chemical fertilizers application was rapidly increased due to the nitrification of $NH_4$ released from the applied urea. At the time of harvest contents of $NO_3-N$ in the soils of compost applications were less than 1.4 mg/kg, but in the soil of chemical fertilizers application the content of $NO_3-N$ was 54.2 mg/kg. Contents of $NH_4$ in lettuce were about 20 mg/kg FW and were not much different among the treatments. However, contents of $NO_3$ in lettuce were significantly different between the treatments of chemical fertilizer and compost. There were significant differences in fresh and dry weights, and growth of lettuce in the compost treatment of 4,000 kg/10a was highest among the treatments. These results indicate that the cultivation with compost only as N source can produce higher yield of lettuce and significantly reduce nitrate accumulation as compared to the conventional cultivation with chemical fertilizers.

• Applied Biological Chemistry
• /
• v.44 no.4
• /
• pp.240-245
• /
• 2001

Suppression of nitrate accumulation in vegetables through foliar application of micronutrients was investigated. Spinach and lettuce were grown in pots under greenhouse condition. Micronutrient solutions containing Cu, Mn, Mo, and Zn were used; chitosan was added into one and the other contained chitosan oligomers. The micronutrient solutions were sprayed on the leaves at 3 and 4 weeks after transplanting of 20-day-old seedlings. Plants were harvested at 5-weeks after transplanting. Yield, contents of chlorophyll, Brix value, micronutrient, and nitrate, and nitrate reductase activity were measured. Fresh weights of lettuce and spinach were significantly increased by the foliar application of micronutrients. Contents of chlorophyll and micronutrients were higher in micronutrient-treated plants, while those of nitrate were reduced by about 10 and 14-23% in lettuce and spinach, respectively. Compared to the control plants, nitrate reductase activity was higher in plants treated with micronutrients. Results of this study indicate the effect of micronutrients on the suppression of nitrate accumulation was relatively small in comparison to the contents of nitrate in leaves of spinach and lettuce. To maximize the effect, nutrient composition in solution, application time, and frequency should be further examined, taking into consideration nitrogen level in soil and other environmental factors including light condition.

• Journal of Applied Biological Chemistry
• /
• v.48 no.1
• /
• pp.11-15
• /
• 2005

Salinity of soils in greenhouse has been increased by massive application of fertilizers. Nitrogen fertilizer was most popular, and thus nitrate became the majority of soil salinity. Accumulation of nitrate led to deleterious effects on the growth and development of crops and vegetables. Microbial strains able to utilize nitrate and thus remove excess nitrate from farm land soils were isolated from 15 different soils of greenhouses and plastic film houses. Four strains able to grow in medium containing 50 mM $KNO_3$ were isolated, among which only E0461 showed high capacity of nitrate uptake. Nitrate uptake by E0461 was dependent on culture medium and was increased by addition of tryptone and peptone. Although E0461 was able to grow without tryptone and peptone, growth was slow, and no nitrate uptake was observed. Nitrate appeared to facilitate E0461 growth in the presence of tryptone and peptone. Through kinetic analysis, nitrate uptake was measured at various concentrations of nitrate, and half-life was calculated. Nitrate concentration decreased with increasing incubation period, and plot between half-lives and initial concentrations of nitrate fitted to single exponential function. These results suggest one major factor plays an important role in microbial nitrate uptake.