total-N Content Research Articles

The nitrogen composition of streams in upland Scotland: some regional and seasonal differences

The nitrogen (N) composition of streams draining four upland regions of Scotland was compared in samples collected monthly between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), dissolved organic N (DON) and dissolved organic carbon (DOC). Concentrations of TN were small, generally less than 1 mg l−1, dominated by dissolved forms of N, and varied significantly between upland regions. Nitrate accounted for most of the variability in TN; largest concentrations were observed in the Southern Uplands and smallest concentrations were observed in the Highlands. Nitrate concentrations were positively correlated with the percentage cover of improved grasslands and brown forest soils and negatively correlated with the percentage cover of peat. Concentrations of DON also varied between regions, but to a lesser extent than those of NO3. Largest concentrations occurred in SW Scotland and smallest concentrations in the Cairngorms. Although a significant positive correlation between DON and DOC was observed, stream water DON content was not related to the percentage cover of peat in the catchment, as was the case for DOC. The average DOC:DON ratio was narrower for streams in the Southern Uplands than for those in the Cairngorms and Highlands. Nitrate and DON displayed contrasting seasonal trends; NO3 concentrations were larger in the winter while DON concentrations were larger in the summer. Only a small proportion, <8% and <7%, of TN was PN and NH4, respectively, the majority of N was present as either NO3 or DON. Nitrate was the dominant fraction (58–65%) in all regions except the Highlands where DON accounted for 57% of TN. However, the relative importance of the DON component increased in the summer in all regions. This study has demonstrated that the DON fraction is an important component of the total N transported by streams from upland catchments in Scotland. Thus, assessments of anthropogenic impacts on N losses from upland ecosystems need to consider not only the dissolved inorganic species but also DON.

Inorganic and organic losses of nitrogen from upland regions of Britain: concentrations and fluxes.

The nitrogen (N) composition of streams draining eight upland regions of Britain was compared using monthly samples collected between April 1997 and April 1998. Stream samples were analysed for total N (TN), particulate N (PN), nitrate (NO3), ammonium (NH4), and dissolved organic nitrogen (DON). Concentrations of TN were small, generally less than 1.5 mg N l(-1), were dominated by dissolved forms of N, and varied significantly between regions. NO3 accounted for the majority of variability. Concentrations of DON also varied between regions but to a smaller extent than those of NO3. There were considerable variations in TN fluxes between upland regions, which ranged between 3.8 and 16.1 kg N ha(-1) year(-1). The majority of the variation was due to NO3 fluxes, which were largest in regions receiving largest inputs of atmospheric N deposition and ranged between 1.4 and 13.5 kg N ha(-1) year(-1). Fluxes of DON ranged between 1 and 3.5 kg N ha(-1) year(-1), while fluxes of PN were generally less than 0.5 kg N ha(-1) year(-1), and NH4 fluxes ranged between 0.1 and 0.4 kg N ha(-1) year(-1). NO3 was the dominant fraction (47–84%) of N exported from all upland regions except the Highlands, where DON accounted for 52% of the TN flux. This study has shown that the DON fraction is an important component of the total N transported by upland streams in Britain.

Effects of applied ABA on growth cessation, bud dormancy, cold acclimation, leaf senescence and N mobilization in apple nursery plants

SummaryCommercial tree fruit nurseries can promote aggressive tree growth by adding greater amounts of N than is necessary. Although this practice may produce the largest stock possible, it often causes physiological problems such as delays in growth cessation, bud dormancy development, and cold acclimation, especially in late apple cultivars. In this study, abscisic acid (ABA) was applied to Fuji/M.26 apple (Malus domestica Borkh.) nursery plants that had been growing into the late season with a high N supply. We tested the hypothesis that exogenously applied ABA enhances growth cessation and that this is related to the improvement of bud dormancy development and cold acclimation. We also studied the effects on leaf senescence and mobilization of leaf N into perennial woody tissues. In September 1996, ABA at 1000.mg l-1 plus 0.1% Tween 80 was sprayed twice, at 7.d intervals. ABA treatment significantly enhanced shoot growth cessation and advanced the early stages of bud endodormancy development; these effects were closely related. Maximum growth cessation and bud dormancy were attained in mid-December similarly in both control and ABA treatments. In early November, stem cold hardiness measured by the electrolyte leakage method was significantly greater in the ABA-treated plants than in the controls, but was similar in late December. This indicated that cold acclimation was related to the depth of bud endodormancy development. N mobilization from the senescing leaves into perennial woody tissues was significantly enhanced by ABA treatment. Therefore, autumnal increases in total-N and soluble-protein concentrations were significantly higher in the ABA-treated plants (especially in the stem bark), but both control and ABA-treated plants reached similar maximum levels later when plants were completely defoliated.

Foliar urea pretreatment tempers inefficient N recovery resulting from copper chelate (CuEDTA) defoliation of apple nursery plants

SummaryCopper chelate (CuEDTA) defoliation of deciduous fruit nursery plants, although effective in leaf removal, causes inefficient N recovery from leaves, which results in reduced reserve N levels in woody perennial tissues, compared with natural defoliation. To correct this problem, we sprayed spring bench-grafted Fuji/M.26 apple (Malus domestica Borkh.) nursery plants with 3% urea twice, at 5 d intervals, 13.d prior to 1% CuEDTA spray treatment on 31 October, 1997. The effects of urea and CuEDTA on defoliation, reserve N, and later regrowth were determined, as compared with those of hand- or natural-defoliation. CuEDTA resulted in >80% defoliation within 6 d of application. The abscission induced by the CuEDTA treatment, however, did cause significantly less N to be withdrawn from leaves compared with those plants undergoing natural defoliation. This inefficient N recovery was tempered by the foliar-urea pretreatment. The application of urea substantially increased the reserve-N level (total-N or soluble-protein concentrations) in all components of the tree without affecting the efficacy of CuEDTA on defoliation. The extent of regrowth in N-deficient medium was proportional to the reserve-N level. The urea-treated plants, whether hand- or CuEDTA-defoliated, showed better growth performance than the no-urea controls. Therefore, CuEDTA, in combination with pretreatments of foliar urea, proved effective for defoliating apple nursery plants, increasing reserve-N levels, and improving regrowth performance during tree establishment.

Impact of nitrogen cycling associated with production and consumption of food on nitrogen pollution of stream water

We evaluated the impact of nitrogen (N) cycling on N pollution of stream water, with emphasis on N disposed of (hereafter referred to as “disposal N”) from human and livestock excrement and the N surplus in cropland, compared to the total-N concentration of stream water, in seven zones of Asahikawa City characterized by various types of land use. In order to estimate N cycling, we used the Nitrogen Flow Model, composed of the N budgets of human, livestock, and cropland subsystems. The urban area with a population density of over 4,000 persons km-2 generated a very large amount of disposal N (about 2,700 kg N ha-1 cropland y-1). Based on the amount of disposal N and the volume of domestic sewage water used, the N concentration estimated for the urban area was 34 mg N L-1, which found in the effluent from the sewage treatment facility (24–28 mg N L-1), regardless of the season. Thus, it was indicated that most of the disposal N in the urban area was discharged directly to streams through the sewage treatment facilities, contributing to a point source of N pollution of stream water. In addition, the disposal N from livestock facilities was larger in pig and poultry farming areas than in other farming areas, contributing to some extent to a potential source of N pollution. As a result, the concentrations increased above 1 mg N L-1 in the urban and surrounding areas. On the other hand, the N surplus in cropland was practically determined by the N flows associated with chemical fertilizer, livestock excrement as manure, and crop uptake. The N surplus was similar among the seven zones, ranging from 69 to 99 kg N ha-1 y-1. The N concentration estimated from the amount of N surplus and 50% of mean annual precipitation as a discharge rate was 13.6–19.5 mg N L-1. Most of the surplus N was indicated to be leached out. However, the total-N concentration measured in the major streams flowing through Asahikawa City was mostly below 1 mg N L-1 except for the urban and surrounding areas. The surplus N in cropland may not reach the streams, even if N leaching occurs, probably due to N removal by plant uptake, denitrification, and sedimentation in the riparian zone and stream channels. Thus the effect of agricultural practices on N pollution of stream water was not appreciable.

Effects of nickel concentration in the nutrient solution on the nitrogen assimilation and growth of tomato seedlings in hydroponic culture supplied with urea or nitrate as the sole nitrogen source

Both the beneficial and the adverse effects of nickel supplement on the N assimilation and growth of tomato plants were evaluated while either urea or nitrate was applied as the sole N source in the nutrient solution. The nickel concentration in the plant was related to that in the solution. Urea toxicity to the plants was reduced by the nickel supplement at 0.01 mgl –1, and no symptom of urea toxicity was observed in the plants when supplemented nickel was at 0.1 or 1 mg 1 –1. Both the plant growth and chlorophyll concentration in leaves of the urea-fed plants increased when nickel concentration in the solution was up to 0.1 mg 1 –1, but decreased by nickel at 1 mg 1 –1. The maximum growth of the urea-fed plants promoted by nickel supplement was still less than 80% of the nitrate-fed plants. Nickel supplement did not affect the growth of the nitrate-fed plants. The concentrations of leaf total-N in the urea-fed plants was enhanced by the nickel supplement, but was still lower than those in the nitrate-fed plants. At 0.1 mg 1 –1 nickel supplement, the concentrations of leaf urea-N and NH 4-N in the urea-fed plants were about one-sixth and four times, respectively, of those without nickel supplement. Urea assimilation increased with the nickel supplement up to 0.1 mg 1 –1. No effect of nickel supplement on the N assimilation in the nitrate-fed plants was found. Nickel supplement up to 0.1 mg 1 –1 reduced urea toxicity and enhanced chlorophyll concentration, plant growth, and urea hydrolysis. The symptom of nickel toxicity and the depression of plant growth were only observed with the nickel supplement up to 1 mg 1 –1.

Gypsum treatment as a restoration method for sediments of eutrophied lakes - experiments from southern Finland

The internal load of phosphorus can be treated with chemicals improving a sediment's phosphorus binding capacity. Gypsum (CaSO4⁎2H2O) is a novel material to be applied for this purpose. In the hypereutrophic Lake Enajarvi, southern Finland, sediments were treated with gypsum in test basins. The basins were isolated from open water to create artificial anoxia, which allowed the effects of the treatment on the internal load to be measured. The results indicate that gypsum treatment decreases the sediment's release of nutrients under anoxic conditions. This was demonstrated as less increased total-P and total-N concentrations and decreased chlorophyll-a concentrations in the water column of treated basins as compared with the control basins. Because the gypsum treatment prevents internal load, it has potential in lake restoration in cases where the internal load of phosphorus is accelerated by anoxic conditions at the sediment/water interface.

Sucrose and Nitrogen Supplies Regulate Growth of Maize Kernels

The growth of maize (Zea mays L.) kernels depends on the availability of carbon (C) and nitrogen (N) assimilates supplied by the mother plant and the capacity of the kernel to use them. Our objectives were to study the effects of N and sucrose supply levels on growth and metabolism of maize kernels. Kernel explants of Pioneer 34RO6 were culturedin vitro with varying combinations of N (5 to 30 m m) and sucrose (117 to 467 m m). Maximum kernel growth was obtained with 10 m m N and 292 m m sucrose in the medium, and a deficiency of one assimilate could not be overcome by a sufficiency of the other. Increasing the N supply led to increases in the kernel sink capacity (number of cells and starch granules in the endosperm), activity of certain enzymes (soluble and bound invertases, sucrose synthase, and aspartate aminotransaminase), starch, and the levels of N compounds (total-N, soluble protein, and free amino acids), and decreased the levels of C metabolites (sucrose and reducing sugars). Conversely, increasing the sucrose supply increased the level of endosperm C metabolites, free amino acids, and ADPG-PPase and alanine transaminase activities, but decreased the activity of soluble invertase and concentrations of soluble protein and total-N. Thus, while C and N are interdependent and essential for accumulation of maximum kernel weight, they appear to regulate growth by different means. Nitrogen supply aids the establishment of kernel sink capacity, and promotes activity of enzymes relating to sucrose and nitrogen uptake, while sucrose regulates the activities of invertase and ADPG-PPase.

Effect of different concentrations of urea with or without nickel addition on spinach (Spinacia oleracea E.) growth under hydroponic culture

To improve the growth of spinach (Spinacia oleracea cv, Okarne) and to decrease shoot nitrate contents, different concentrations of urea were used as a source of nitrogen in the nutrient solution For hydroponically grown plants. Spinach was grown in a hydroponic got culture amended with 0,20, or 58% urea with or without nickel addition (Ni; 0.05 mg L-1) while the dotal concentration of N (17.33 mmol L-1) remained constant in all the cases. In order to identify the most eEective conceniration of Ni for the growth of spinach, another experiment was conducted using various concentrations sf Ni in a 50% urea solution. Addition of 0.05 mg Ni L-1 to the nutrient solution gave the best results in terms of qualitative and quantitative charaeteristies Naximuna vegetative production was achieved with a 28% urea solution contaimnang Ni. Shoot NO3-N content significantly decreased with increasing level sf urea in the solution. The urea-N content in the shoots was significantly inc~easedw ith both 20 and 50% urea solution without Ni addition. The total-N content in the shoots was almost the same in all the experimental treatments except those utilizing 50% urea solution without Ni addition. The content of Ca in the shoots increased by the addition of Ni with urea in the nutrient soleation, Fe eontent in the shoots was slightly affected by nrea nutrition, except for the treatment utilizing 20% urea solution with Ni addition. The contents of K, Mg, and Zn were significantly agected by urea in the nutrient solution. Ni in the shoots was not detected when it was not supplied in the nutrient solution. Also, the Ni content in the shoots was within the range of natural abundance when Ni was added to the 20 and 50% urea solutions.

Relationships of Nitrogenous Compounds in Petiole Sap of Tomato to Nitrogen Fertilization and the Value of these Compounds as a Predictor of Yield

`Colonial' tomato (Lycopersicon esculentum Mill.) plants were grown on raised beds with black polyethylene mulch, drip irrigation, and preplant-N rates of 0, 67, 134, 202, or 269 kg·ha-1. Petiole sap was collected 7 and 13 weeks after transplanting. Concentrations of NO3-N, free amino acids, total amino acids, and total-N (the sum of NO3-N and amino acid-N) were examined as functions of the rate of N fertilization. Also, each of these compounds was used as an independent variable as a predictor of fruit yield. Seven weeks after planting, the concentrations of NO3-N and 15 of 18 of the free amino acids were correlated with the rate of N fertilization, but concentrations of bound or total amino acids were not. The amount of NO3-N accounted for 37% of the total-N in the 0 kg·ha-1 treatment, and up to 83% in the 202 kg·ha-1 treatment. NO3-N was highly correlated with total-N for both nonhydrolyzed and hydrolyzed sap (R2 = 0.98). Thirteen weeks after transplanting, neither the concentration of NO3-N nor that of amino acids, other than asparagine, glutamine, and proline, were significantly related to the rate of N fertilization. On both dates, concentrations of glutamine plus glutamic acid were correlated with rate of N fertilization whether expressed as absolute values or as percentage values. N fertilization rate and the concentration of NO3-N or total-N were related to total fruit yield (R2 = 0.69 to 0.74), and marketable fruit yield (R2 = 0.78 to 0.82). N-fertilization rate and petiole sap concentrations of NO3-N or total-N were also correlated with the N contained in total or marketable yield. Petiole sap variables measured 13 weeks after transplanting were not significantly correlated with fruit yield or the quantity of N contained in the fruit. Free, bound, or total amino acids in petiole sap were not as well correlated with fruit yield parameters as were N-fertilization rate, NO3-N, or total-N in petiole sap.

Influence of Site and Fertiliser Addition on Nutrient Cycling in Eucalyptus globulus Plantations in Gippsland, South-eastern Australia. I. Foliage and Litter Quality

The productivity of Eucalyptus plantations on many sites in south-eastern Australia is limited by nitrogen and phosphorus supply. Therefore, after canopy closure, nutrient return and decomposition are key processes maintaining productivity. To gain a better understanding of the effects of site and fertilisers on these processes, foliage and litter quality in E. globulus (Labill.) plantations in Gippsland, south-eastern Australia were characterised on three sites covering a range of soil types, inherent soil fertility and fertiliser treatments. Foliage and litter quality were estimated by sequential extraction of labile forms of N, P and C with cold, then hot, trichloroacetic acid (TCA). Selected treatments were sampled in N × P factorial fertiliser trials of 6-year-old trees where nutrients were added up to 2 years of age. Foliage and litter were categorised as recent or old depending on sampling position. Site significantly influenced concentrations of total and labile N and P (P &lt; 0.0001) in foliage and litter. Phosphorus fertiliser increased total P concentrations in old foliage at two sites, with the greatest absolute and relative increases at the least fertile site (Glencoe). Inorganic P extracted by cold (4°C) TCA accounted for 30-55% of total leaf and litter P and was the fraction most responsive to P fertiliser addition. Total N concentration and N fractions in foliage and litter were not influenced by N fertiliser addition. Inorganic N extracted by cold and hot (90°C) TCA accounted for less than 2% of total N and was not significantly different among fertiliser treatments. Both sugar and phenol concentrations in foliage and litter varied significantly between sites, with the least fertile site showing significantly higher concentrations of phenols in recent litter. Sugars and phenols extracted in cold TCA decreased from old foliage to litter at all sites and were not influenced by N and P fertiliser addition. The results show that additions of 200 kg ha-1 of P cause perturbations in P cycle that are bigger in magnitude and are sustained for longer periods of time compared to changes in N cycle with 400 kg ha-1 of N additions.

Chemical changes during ensiling of sudax fodder with broiler litter

Sudax fodder was ensiled in large trench silos with or without the addition of 30% broiler litter and 6% molasses. The samples were analysed for pH, lactic acid, nitrogen and fiber fraction at 0- and 5-day interval till 40 days. The silage containing broiler litter had higher initial and subsequent pH due to high ammonia concentration. pH of both silages had the largest drop during the first 5 days of ensiling, with corresponding increase in lactic acid. pH continued decreasing until 10 days in silage without litter and 15 days in silage containing litter. Lactic acid continued increasing in silage without litter until 15 days and with litter until 25 days of ensiling. The addition of broiler litter resulted in significantly decreased content of NDF, hemicellulose and cellulose and increased content of ADF. Ensiling period had significant effect on all the fiber fractions. Total-N content increased slightly during the ensiling process but protein-N decreased considerably at the fifth day of ensiling with simultaneous increase in ammonia-N. Later on, there was a slight reversal but it never corresponded with the initial values.

Trend-analysis of eutrophication variables in lakes in The Netherlands

A trend-analysis of eutrophication variables was performed for a large number of lakes in The Netherlands. Data of in total 231 lakes were available. Data on chlorophyll-a, total phosphorus (total-P) and total nitrogen (total-N) were analysed over the period 1980-1996. Summer-averaged concentrations for chlorophyll-a, total-P and total-N decreased in respectively 65%, 73% and 75 of the lakes with at least eight years data between 1980 and 1996. Results for winter means were comparable (a negative trend in 54%, 77% and 69% for concentrations of chlorophyll-a, total-P and total-N respectively). Since 1980 the median decrease in the summer averaged concentrations of chlorophyll-a, total-P and total-N is 2.61 μg l−1 y−1, 0.008 mg l−1 y−1 and 0.046 mg l−1 y−1, respectively, illustrating the effects of (inter)national and regional measures to combat eutrophication.

Activities of some soil enzymes in different land use systems after deforestation in hilly areas of West Lampung, South Sumatra, Indonesia

The activities of acid and alkaline phosphatases, β-glucosidase and urease were determined in soils under different land-use systems after deforestation in hilly areas of West Lampung, South Sumatra, Indonesia. Soil samples (topsoils, 0–20 cm and subsoils, 20–40 cm) were collected from 5 different locations, each consisting of 4 different land-use systems: i.e. primary forests, secondary forests, coffee plantations, and cultivated lands (upland fields and paddy fields). Enzyme analyses showed that the activities of phosphatases, β-glucosidase, and urease were significantly higher in most cases in the primary forests or in the secondary forests than in the other two land-use systems, indicating that clearing the forests and converting them to other land-use systems significantly disturbed the growth of enzyme-producing organisms. There was no significant difference in the enzymatic activities between cultivated upland fields and paddy fields. The activity of alkaline phosphatase showed the most drastic decrease after the conversion to the other land uses. Laboratory experiment showed that the optimum pH for phosphatases shifted to higher values due to the land-use conversion from the primary forests to the other land use systems. Analysis of subsoils showed significantly lower enzymatic activities compared to those in the topsoils. The activities of all soil enzymes in the topsoil were closely related to the soil organic-C and total-N contents, indicating that these properties are important for maintaining the soil enzymatic activities. Based on the land use change from 1978 in the study area (27 km x 27 km), the land conversion was estimated to have decreased the activities of the soil enzymes tested by 4–12% by 1984 and by 7–20% by 1990 in the uppermost 0–20 cm layers, and by 6–12% by 1984 and by 6–18% by 1990 in the next 20–40 cm layers from the levels in 1978, respectively.

Ecosystem recovery after a decrease in nitrogen input to a Scots pine stand at Ysselsteyn, the Netherlands

In a highly N-saturated Scots pine stand atmospheric N input to the forest floor was reduced to pre-industrial levels by means of a transparent roof and application of clean, artificial throughfall water. The N input was reduced from ≈ 60 kg N ha −1 yr −1 to <5 kg N ha −1 yr −1. The experiment began in 1989 and is part of the NITREX project. The aim is to assess the reversibility of N saturation. The results showed a close correlation between the input and output of N. The timing of this response is fast in contrast to the vegetation response which lags for some years. After this lag-phase signs of ecosystem recovery were noticed. The N concentration in the needles declined and the nutritional balance improved. Free arginine-N concentrations in the needles may be indicative of tree response to changes in N input. Although the total-N concentration in the needles is still high, the rapid drop in arginine-N concentrations may be the first sign of recovery. The trees have reacted with a growth improvement which is significantly correlated to decreasing arginine-N concentrations. The above-ground biomass of the nitrophilous ground vegetation decreased markedly during the experimental period, whilst there was a re-colonization and increase of fruitbodies of mycorrhizal fungi.

Trend-analysis of eutrophication variables in lakes in The Netherlands

Abstract A trend-analysis of eutrophication variables was performed for a large number of lakes in The Netherlands. Data of in total 231 lakes were available. Data on chlorophyll-a, total phosphorus (total-P) and total nitrogen (total-N) were analysed over the period 1980–1996. Summer-averaged concentrations for chlorophyll-a, total-P and total-N decreased in respectively 65%, 73% and 75% of the lakes with at least eight years data between 1980 and 1996. Results for winter means were comparable (a negative trend in 54%, 77% and 69% for concentrations of chlorophyll-a, total-P and total-N respectively). Since 1980 the median decrease in the summer averaged concentrations of chlorophyll-a, total-P and total-N is 2.61 μg l−1 y−1, 0.008 mg l−1 y−1 and 0.046 mg l−1 y−1, respectively, illustrating the effects of (inter)national and regional measures to combat eutrophication.

Carbon, Nitrogen, and Sulfur Pools in Particle‐Size Fractions as Influenced by Climate

AbstractThe response of soil organic matter (SOM) dynamics to climate change may be deduced from changes in the distribution of SOM among different C pools. The distribution of soil organic carbon (SOC), total N, and total S in particle‐size fractions were measured to assess the influences of climate. Clay (&lt;2 µm), silt (2–20 µm), fine sand (20–250 µm), and coarse sand (250–2000 µm) fractions were obtained from composite soil samples from the top 10 cm of 21 native grassland sites along temperature and precipitation transects from Saskatoon, Canada, to southern Texas, USA. The clay fraction contained about 43% of the total SOC, 56% of the total N, and 62% of the total S. The SOC and total‐N concentrations in the clay fraction, relative to those in the bulk soil, increased significantly across sites with increasing annual temperature, decreasing annual precipitation, and decreasing clay content (multiple R2 = 0.80*** [significant at P = 0.001] for SOC and 0.83*** for N); the concentration of SOM in the fine sand fraction showed the opposite trends. Principal axis component analyses confirmed that both clay and fine sand fractions comprised sensitive SOC and N pools related to climate, whereas S seemed to be controlled by factors other than those regulating the dynamics of SOC and N. These results suggest that SOM is preferably decayed from pools of the fine sand fractions with increasing temperature, resulting in a relative enrichment of SOM stabilized on clay.

ＮＦＴ栽培におけるイチゴの養水分吸収に及ぼすＣＯ２施用の影響

This experiment was carried out to investigate the effects of CO2 enrichment (700-800 ppm in the day time) on the absorption of water and mineral nutrients in strawberry (Fragaria × ananassa Duch. cv. Nyoho) grown by nutrient film technique. The concentration of major elements in the nutrient solution were NO3- : 5, NH4+ : 1, H2PO4- : 1, K+ : 3, Ca2+ : 1, Mg2+: 1 mmol·L-1. Vigorous growth and high yield were obtained by CO2 enrichment. In control (ambient CO2, 200-400 ppm), the uptake concentration (each mineral absorbed per unit volume of water absorbed, n/w) was almost equal to the concentration of the solution, throughout growing period. However, under CO2 enriched condition, n/w and total uptake amount of minerals increased by 30-60% compared to control, especially, from November to February when the temperature and light intensity were low. The n/w of minerals were also 50-100% higher than the concentration of the nutrient solution. Total-N concentration in leaves was markedly decreased by CO2 enrichment, while there was little difference in P, K, Ca and Mg. To keep the concentration of nutrients in the solution, the concentration of nutrients should be kept 50-100% higher than those previously reported, when strawberry plants are grown with CO2 enrichment.

Nitrogen management and biological nitrogen fixation in sorghum/pigeonpea intercropping on Alfisols of the semi-arid tropics

Pigeonpea (Cajanus cajan L. Millsp) and sorghum (Sorghum bicolor L. Moench). are grown as intercrops on soils typified by low nitrogen (N). particularly Alfisols and Vertisols of the semi-arid tropical areas of India and East Africa. Proper management of fertilizer N in sorghum/pigeonpea intercropping systems is essential to enhancing biological nitrogen fixing ability of pigeonpea, and to increasing grain yields of sorghum.In a 3-year study, we examined the effect of time and rates of fertilizer N application on biological N fixation (BNF) and fertilizer N recovery by pigeonpea and sorghum grown as a sole crop, and as an intercrop on an Alfisol in India. In 1993, N (50 kg N ha−1) was all applied at planting (basal) or at 40 days after sowing (delayed). During 1994–1995, four N rates 0, 25, 50, and 100 kg ha−1 were applied (i) 100% at planting (basal) or (ii) 67% at 40 days, and 33% at 60 days after sowing (delayed).Delaying N fertilization until 40 days after sowing (DAS), rather than applying at sowing significantly increased (p < 0.001) total dry matter, grain yield (GY) and total N content (TNC) of the sorghum, but not of pigeonpea. Highest GY and TNC was recorded at an N rate of 50 kg ha −1 with sole crop sorghum, and at 25 kg ha−1 for intercrop sorghum. Delaying N fertilization to sorghum significantly (p < 0.001) increased 15N recovery in the shoot from 15 to 32% in sole crop, and 10 to 32% in intercrop. Similarly, there was a significant (p < 0.001) increase in N recovery (calculated without 15N, but by the difference between the nonfertilized N and fertilized plots) from 43–59% in sole crop and from 28–71% in intercrop sorghum. Pigeonpea fixed between 120–170 kg ha−1 of atmospheric N throughout the cropping season. Nitrogen application to the sorghum row, but not to the pigeonpea, enhanced BNF by pigeonpea and maximized fertilizer recovery by sorghum in a sorghum/pigeonpea intercropping.

Effect of Various NaCl Levels on the Growth, Chlorophyll, Proline and Mineral Compositions of Tomato (Lycopersicon esculentum L.) Grown on Peat-Perlite Medium with Nutrient Solution

The effect of increasing levels of NaCl (0, 50, 75 and 100 mM) on the fresh and dry weight, chlorophyll, proline and mineral constituents of tomato (Lycopersicon esculentum L.) grown on peat-perlite medium with nutrient solution under greenhouse conditions was investigated. According to experimental results, fresh and dry weight of the plants were decreased by NaCl treatments. Sodium and Cl content of the plants were increased, while K and total-N contents were decreased by NaCl treatments. Chlorophyll and proline content of the plants were increased by NaCl applied to the nutrient solution.