MODULATION OF MACRONUTRIENTS UPTAKE AND TRANSLOCATION IN Mn-TREATED RICE IN EARLY STAGES OF VEGETATIVE GROWTH

The effect of increasing manganese (Mn) concentrations on calcium (Ca), potassium (K), magnesium (Mg), sodium (Na), and phosphorus (P) absorption and translocation was studied in rice (Oryza sativa L. cv. Safari), before and after the end of mobilization of seed reserves. Rice plants were grown over a 15-, 21-, and 28-day period in nutrient solutions containing Mn concentrations varying between 0.125 and 32 mg L^?1. It was found that increasing Mn concentrations in the nutrient solution was coupled to an increasing net uptake, total shoot accumulation, and root and shoot contents of this metal during all the experimental periods. Concerning the translocation rates, in 15-day-old plants a decrease was found after the 2 mg L^?1 Mn treatment, but from the 21st day onward an increase was found until the highest treatment. The modulating action of Mn in macronutrient accumulation displayed different patterns among the experimental periods. In the root tissues of 15-day-old plants, Ca decreased significantly until the 2 mg L^?1 treatment and Na increased. In the shoots, the contents of P and Na decreased, but K and Mg showed significant increases. Until the 32 mg L^?1 Mn treatment, the ratio between root and shoot concentrations of K and Mg decreased in these plants. A similar pattern was also found for Ca until the 2 mg L^?1 Mn treatment. That ratio increased for Na. Plant total amount of Ca sharply decreased. Shoot total amount of Na and P also decreased, but the pattern of Ca increased until the 2 mg L^?1 Mn treatment. The concentrations of K increased in the root tissues 21 days after germination, but the levels of Ca, Mg, Na, and P decreased. In the shoots, the concentrations of Ca and Mg decreased significantly. Until the 32 mg L^?1 Mn treatment, the ratio between root and shoot concentration of Na and P increased, whereas those of Ca and Mg decreased. An increase was found for the plant and shoot total amount of Ca, K, and Mg until the last Mn treatment, but an opposite trend was found for Na and P. Additionally, until the 32 mg L^?1 Mn treatment, an increase was found for the proportions of Ca and Mg translocated to the shoot, but an opposite trend was detected for P. It was concluded that before and after the end of the mobilization of seed reserves, the net uptake rate of Ca is reversed, and, moreover, a similar trend is shown for the net translocation of Mg. A major implication of this process is the alteration of the related pattern for shoot accumulation. Eventually a different selectivity of the K⁺:Na⁺ ratio is also developed in the roots.     

Crop Residue Effects on Calcium,Magnesium, Potassium,and Sodium Runoff Losses from a Soil Prone to Crusting

In Galicia (northwestern Spain), cultivated soils developed on schists from the Ordenes series are susceptible to surface degradation, mostly when soil organic content decreases. Therefore, management systems that protect the soil and increase its organic-matter content should also improve its quality. However, tillage practices may cause crusting. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on the basic cation nutrient [calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na)] losses by runoff from a tilled soil with relatively low organic-matter content. Runoff and sediment yield were measured on 1-m² plots using a rainfall simulator with constant 65 mm h^?1 intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t ha^?1 in the five treatments studied. Total and dissolved concentrations of the elements studied showed a tendency to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L^?1, Mg from 20.81 to 148.90 mg L^?1, K from 14.20 to 35.17 mg L^?1, and Na from 14.99 to 23.41 mg L^?1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% for Na. The results confirm that corn residues applied to a degraded soil, with low structural stability, prevent cation nutrient losses.     

Determination of organic acid anions in precipitation by ion chromatography exclusion

A method for the determination of organic acid anions in precipitation samples is described. The technique of ion chromatography exclusion (ICE) is used to identify and quantify the more commonly found anions of the acids citric, formic and acetic in central Illinois rainwater. By using a two column system consisting of a separator and suppressor, method detection limits (MDL) of 0.03 mg L^?1 for each of the three anions are obtained. The total analysis time for quantitation is 24 min. Samples collected from early spring rains contained primarily formate and acetate ions with levels of concentration ranging from 0.03 to 0.44 mg L^?1. The organic acids formic and acetic contributed approximately 8% to the total acidity in the precipitation samples analyzed. Precision averaged 5% as the relative standard deviation (RSD) and analyte spikes of natural precipitation samples revealed a mean recovery of greater than 99%. A preservation technique using chloroform (CHCl₃) addition is discussed with results indicating its necessity in maintaining original organic anion concentrations.     

Aluminum retention in a man-made Sphagnum wetland

Runoff from a highway interchange in western Maryland had Al concentrations averaging about 50 mg L^?1, with a maximum of 206 mg L^?1. As an alternative to expensive chemical treatment of this Al-rich water, in August 1984, the drainage was diverted through a 500 m² man-made wetland, constructed from organic peat. For a 10 week period, Al concentrations in water leaving the wetland averaged 1.5 mg L^?1. as compared to Al concentrations at the two major inflows to the wetland of 35.3 and 6.6 mg L^?1. However, effective treatment of the drainage by the wetland was not observed over the entire 27 mo sampling period. Peat chemical analysis indicated that over the 27 mo, total Al concentration in the peat increased from 2375 μg g^?1 to 13 634 μg g^?1. Of this increase 5.5 % was contributed by exchangeable Al, 4.3% by adsorbed Al, 39.8% by organically bound Al, 33.1% by oxide bound Al, and 17.2% by precipitated and residual Al. Changes in Fe, Mn, Ca, Mg, K, and Na chemistry in the peat associated with Al retention are discussed.     

Growth and nutrient uptake of tomato in response to application of saline water,biological fertilizer,and surfactant

The importance of using low-quality water, such as saline waters, for food production has been increased in the recent decades. An experiment was conducted to evaluate the effect of diluted seawater (electrical conductivity (EC) of 6 dS m^?1) on growth and nutrient uptake of tomato. We examined if surfactant (0, 1, 2, 4 mg L^?1) and biological fertilizer (compost tea + arbuscular mycorrhizal fungi propagules) have potential to alleviate the adverse effects of salinity on tomato plant. Salinity stress significantly reduced all plant growth parameters. Under salinity stress, nitrogen (N) and potassium (K) contents in tomato shoot were lower, while phosphorus (P), sodium (Na), and calcium (Ca) contents were higher than non-salinized plants; showing ionic imbalance in this condition. Biological fertilizer improved root weight in saline condition. Under salinity stress surfactant application at the rate of 1 mg L^?1 helped tomato plants to maintain their ionic balance, especially declining Na uptake, and improved plant growth.     

TREATED EFFLUENT AND SALINE WATER IRRIGATION INFLUENCES SOIL PROPERTIES,YIELD, WATER PRODUCTIVITY AND SODIUM CONTENT OF SNOW PEAS AND CELERY

To determine the effects of irrigation water quality, plants were irrigated with normal potable water [0.25 dS m^?1 electrical conductivity (EC), 25 mg L^?1 sodium (Na), 55 mg L^?1 chloride (Cl)], treated effluent (0.94 dS m^?1 EC, 122 mg L^?1 Na, 143 mg L^?1 Cl) and saline water with low salinity (1.24 dS m^?1 EC, 144 mg L^?1 Na and 358 mg L^?1 Cl) and high salinity (2.19 dS m^?1 EC, 264 mg L ^?1Na and 662 mg L^?1 Cl) for snow peas, and high salinity (3.07 dS m^?1 EC, 383 mg L^?1 Na and 965 mg L^?1 Cl) and very high salinity (5.83 dS m^?1 EC, 741 mg L^?1 Na and 1876 mg L^?1 Cl) for celery. The greater salts build up in the soil and ion toxicity (Cl and Na) with saline water irrigation contributed to significantly greater reduction in root and shoot biomass, water use, yield and water productivity (yield kg kL^?1 of water used) of snow peas and celery compared with treated effluent and potable water irrigation. There was 8%, 56% and 74% reduction in celery yield respectively with treated effluent, high salinity and very high salinity saline water irrigation compared with potable water irrigation. The Na concentration in snow peas shoots increased by 54%, 234% and 501% with treated effluent, low and high salinity saline water irrigation. Similarly, the increases in Na concentration in celery shoots were 19%, 35% and 82%. The treated effluent irrigation also resulted in a significant increase in soil EC, nitrogen (N) and phosphorus (P) content compared with potable water irrigation. The heavy metals besides salts build up appears to have contributed to yield reductions with treated effluent irrigation. The study reveals strong implications for the use of saline water and treated effluent for irrigation of snow peas and celery. The salt build up within the root zone and soil environment would be critical in the long-run with the use of saline water and treated effluent for irrigation of crops. To minimize the salinity level in rhizosphere, an alternate irrigation of potable water with treated effluent or low salinity level water may be better option.     

The Effect of Chloride on Yield and Nutrient Interaction in Greenhouse Tomato (Lycopersicon Esculentum Mill.) Grown in Rockwool

The effect of increasing chloride content in nutrient solution on nutrient composition in root environment, interaction of nutrients in leaves and yield of greenhouse tomato cv. ‘Grace F₁’ grown in rockwool were searched. In Experiment I (2004–2005) the levels of 15, 30, 60, and 90 mg Cl·L^?1 but in Experiment II (2006) 30, 60, 90 and 120 mg Cl·L^?1 of nutrient solution were tested. The sources of chloride were water (9.6–10.7 mg Cl·L^?1) and calcium chloride (CaCl₂·2H₂O) but the rest of nutrients and sodium in all treatments were on the same levels. It was found that increasing content of chloride from 15 to 60 mg Cl·L^?1 enhanced the total and marketable fruit yield. Within the range of 60 to 90 mg Cl·L^?1 the yield was on the optimum level but the content of 120 mg Cl·L^?1 declined it. Increasing chloride content in the nutrient solutions was reflected in rising of chlorine content in leaves. The concentration of chloride above 60 mg C·L^?1 reduced the content of nitrogen but above 90 mg C·L^?1 declined the content of calcium, sulfur and zinc in leaves. The antagonism between Cl:N, Cl:Ca: Cl:S and Cl:Zn was appeared. More variable interaction were between Cl:K and Cl:B. At the low levels of chloride, from 15 to 60 mg Cl·L^?1, potassium and boron content were decreased but at the higher ones, from 90 to 120 mg·L^?1, these nutrients had increasing course. It was not found out the effect of chloride contents on macro and microelement contents in nutrient solution emitted from drippers however their content upraising in root medium (rockwool). The highest increase was found out for Na 95.1 and 64.9 % (Exp. I and II - respectively), next for Ca (76.0, 70.1 %), Cu (62.5 and 71.0 %), Cl (43.6, 24.4), B (33.3, 21.0 %), N-NO₃ (30.4, 49.6 %), Zn (29.5, 32.8 %), S-SO₄ (25.9, 25.5 %), K (24.5, 24.1 %), Fe (19.8, 19.2 %), Mn (17.5, 21.3 %) and Mg (14.9, 11.7). Advantageous effect of chloride on tomato yield justified the need to introduce for the practice adequate chlorine nutrition, and recommend to maintain 60 to 90 mg Cl·L^?1 in nutrient solution. The best yield appeared when content of chlorine in leaves (8th or 9th leaf from the top) was in the range 0.48-0.60 % of Cl in d. m.     

Nutrient leaching losses from a sandy soil in lysimeters

Abstract

Two lysimeter experiments were conducted on annual leaching losses of calcium (Ca), potassium (K), sodium (Na), chloride (Cl), sulphate‐sulphur (SO₄‐S), and magnesium (Mg) (one experiment only) from a sandy soil in central England during 1988–1995 to provide information on typical nutrient losses under arable agriculture below 1.2 m (Experiment 1) or 1.5 m (Experiment 2). Total annual losses, in the absence of manure additions, were highly dependent on the amount of drainage; flow‐weighted average concentrations were similar between years within experiments. Concentrations, averaged over the duration of the experiments were 74 and 78 mg L^‐1 Ca, 17 and 27 mg L^‐1 Na, 11 and 8 mg L^‐1 K, 74 and 77 mg L^‐1 Cl, and 57 and 38 mg L^‐1 SO₄‐S for the two experiments respectively; Mg concentration was 17 mg L^‐1. Applications of chicken litter were made to some of the lysimeters in the last three years, and all nutrients showed increased leaching as a result. Application rates akin to disposal (rather than for crop fertilization) produced the largest losses. Following a total application of 125 t ha^‐1 over three years, average concentrations in water draining below 1.5 m in the final year were 57 and 277 mg L^‐1 Ca, 22 and 75 mg L^‐1 Cl, 7 and 14 mg L^‐1 K, 22 and 57 mg L^‐1 Na, 27, and 125 mg L^‐1 SO₄‐S for the untreated and manured soils, respectively.     

EFFECT OF LANTHANUM ON RICE PRODUCTION,NUTRIENT UPTAKE,AND DISTRIBUTION

ABSTRACT

Split root solution culture experiments were conducted to study the effects of the rare earth element lanthanum (La) on rice (Oryza sativa) growth, nutrient uptake and distribution. Results showed that low concentrations of La could promote rice growth including yield (0.05 mg L^?1 to 1.5 mg L^?1), dry root weight (0.05 mg L^?1 to 0.75 mg L^?1) and grain numbers (0.05 mg L^?1 to 6 mg L^?1). High concentrations depressed grain formation (9 mg L^?1 to 30 mg L^?1) and root elongation (1.5 mg L^?1 to 30 mg L^?1). No significant influence on straw dry weight was found over the whole concentration range except for the 0.05 mg L^?1 treatment. In the pot and field experiments, the addition of La had no significant influence on rice growth.Lanthanum had variable influence on nutrient uptake in different parts of rice. Low concentrations (0.05 mg L^?1 to 0.75 mg L^?1) increased the root copper (Cu), iron (Fe), and magnesium (Mg), and grain Cu, calcium (Ca), phosphorus (P), manganese (Mn), and Mg uptake. High concentrations (9 to 30 mg L^?1) decreased the grain Ca, zinc (Zn), P, Mn, Fe and Mg, and straw Ca, Mn, and Mg uptake. With increasing La concentration, root Zn, P, Mn, Cu, and Ca concentrations increased, and grain Ca and Fe, and straw Mn, Mg, and Ca concentrations decreased. Possible reasons are discussed for the differences between the effects of La in nutrient solutions and in pot and field experiments.     

Base additions to flowing acidic water: Effects on smolts of Atlantic salmon (Salmo salar L.)

Acidic, Al-rich soft water (pH=5.1, Ca=1.0 mg L^?1 and labile Al=160 μg Al L^?1) was treated by addition of soda (Na ₂Co₃) and lime slurry (CaCO₃). Seven different water qualities of each type of treatment, covering the pH-range 5.1 to 8.2, were prepared in a flow-through system. Smolts of Atlantic salmon (Salmo salar L.) were used as test fish. In both types of treatment, mortality occurred at all pH-levels below 6.05. Above pH 6.05 no mortality occurred using lime slurry. Using soda, 10 % mortality occurred within 48 hr at pH above 7 due to the toxicity of aluminate at low levels of Ca. Plasma chloride levels indicated no physiological stress in the pH-range 6.45 to 7.0.     

Characterization of nutrients uptake and enzymes activity in Khatouni melon (Cucumis melo var. inodorus) seedlings under different concentrations of nitrogen,potassium and phosphorus of nutrient solution

A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210?mg L^?1 N; 0, 8, 16, 23 and 31?mg L^?1 P; 0, 59, 118, 176 and 235?mg L^?1 K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8?mg L^?1 P, 59?mg L^?1 K and 158?mg L^?1 N. The leaf catalase activity was highest at zero concentration of P, 158?mg L^?1 N and 176?mg L^?1 K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210?mg L^?1 N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105?mg L^?1 N, 176?mg L^?1 K and 23–31?mg L^?1 P. The highest iron concentration of leaves was obtained from 23 to 31?mg L^?1 P, 176?mg L^?1 K and 210?mg L^?1 N.     

Using Soil Potassium Adsorption and Yield Response Models to Determine Potassium Fertilizer Rates for Potato Crop on a Calcareous Soil in Pakistan

Ustochrept soil was collected from a major potato-growing area in Pakistan for a potassium (K) adsorption isotherm experiment. Adsorption data were fitted to Freundlich and Langmuir adsorption models. Results showed that the Freundlich model (R²?=?0.96**) fit the data better than did the Langmuir model. Fertilizer rates were calculated based on the Freundlich model and targeted solution K levels at 0, 3, 6, 9, 12, 15, 18, 21, 24, and 27 mg K L^?1. A field experiment was then conducted on the soil to assess the effect of various soil solution K levels (0–27 mg L^?1, with K fertilizer rates at 0, 24, 49, 75, 101, 128, 155, 182, 210, and 237 kg ha^?1), on tuber yield and quality along with 300 kg N and 250 kg P₂O₅ ha^?1 as basal doses. Yield response models (linear plus plateau, quadratic, square root, quadratic plus plateau, and exponential) were used to calculate the optimal fertilizer rate for potato crop. Linear plus plateau model fit the data with less bias than the other models. There was a significant effect of K use on the yield and quality of potatoes. Potassium fertilizer application at 130 kg K ha^?1, which is equivalent to a soil solution level of 12 mg K L^?1, maximized the tuber yield of potato. However, for the improvement in tuber dry matter, reducing sugars, protein contents, and starch contents, the soil solution K level required was as high as14.62 mg L^?1 (157 kg ha^?1). Even greater rate of K, 17.74 mg L^?1 (190 kg ha^?1), was needed to maximize vitamin C content in potato.     

Water flow paths in soil control element exports in an Andean tropical montane forest

We tested the hypothesis that concentrations of chemical constituents in stream water can be explained by the depth of water flow through soil. Therefore, we measured the concentrations of total organic carbon (TOC), NO₃‐N, NH₄‐N, dissolved organic nitrogen (DON), P, S, K, Ca, Mg, Na, Al and Mn in rainfall, throughfall, stemflow, litter leachate, mineral soil solution and stream water of three 8–13 ha catchments on steep slopes (1900–2200 m above sea level) of the south Ecuadorian Andes, from April 1998 to April 2003. Peak C (14–22 mg litre^?1), N (0.6–0.9 mg litre^?1), K (0.5–0.7 mg litre^?1), Ca (0.6–1.0 mg litre^?1), Mg (0.3–0.5 mg litre^?1), Al (110–390 μg litre^?1) and Mn (3.9–8.4 μg litre^?1) concentrations in stream water were associated with lateral flow (fast near‐surface flow in saturated topsoil) while the greatest P (0.1–0.3 mg litre^?1), S (0.3–0.7 mg litre^?1) and Na (3.0–6.0 mg litre^?1) concentrations occurred during low baseflow conditions. All elements had greater concentrations in the organic layer than in the mineral soil, but only C, N, K, Ca, Mg, Al and Mn were flushed out during lateral‐flow conditions. Phosphorus, S and Na, in contrast, were mainly released by weathering and (re‐)oxidation of sulphides in the subsoil. Baseflow accounted for 32% to 61% of P export, while > 50% of S was exported during intermediate flow conditions (i.e. lateral flow at the depth of several tens of cm in the mineral soil). Near‐surface water flow through C‐ and nutrient‐rich topsoil during rainstorms was the major export pathway for C, N, Al and Mn (contributing > 50% to the total export of these elements). Near‐surface flow also accounted for one‐third of total base metal export. Our results demonstrate that near‐surface flow related to storm events markedly affects the cycling of many nutrients in steep tropical montane forests.     

Throughfall quality and quantity in polluted and damaged ecosystems in Northern Bohemia

The interaction between high concentrations of polluting gases (SO₂ and NO_x) and damaged forest ecosystems was observed by studying throughfall precipitation in the Erzegebirge Mountains, Northern Bohemia. Qualitative and quantitative data on throughfall for the period November 1989–October 1990 are presented. Weighted averages of SO ₄ ^2? and NO ₃ ^? concentrations in the throughfall were 23.05 mg L^?1 and 13.61 mg L^?1 in a beech and 34.41 mg L^?1 and 11.03 mg L^?1 in a spruce forest respectively. Three variables (the molar ratios of K/Na, N_tot/S and N-NO₃/N-NE₄) were used to compare the spruce throughfall quality to that observed in areas with similar however, less damaged spruce stands. Both K/Na and N-NO₃/N-NH₄ ratios clearly decreased with increasing tree damage, the N_tot/S ratio increased. The results suggest that the throughfall in damaged ecosystems of the Erzegebirge region becomes more like a wet precipitation as the tree canopies get sparser and the trees reduce canopy leaching.     

Temporal Oscillations of Calcium,Magnesium, Potassium,and Sodium Dissolved Contents in an Agroforestry Catchment from the Atlantic Galicia

There is an increasing awareness worldwide of the conveyance of sediment-associated nutrients across eroding soil surfaces into receiving waters. The objective of this study was to analyze the temporal oscillations of concentrations as well as the exportation of calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) at the outlet of an agroforestry catchment. These macronutrients were measured in the drainage waters of a 36.3-km² catchment located at the Valiñas River (Coruña, northwest Spain), where 560 samples were taken from 2003 to 2007. The water collection strategy was a stratified point sampling involving more frequent collections when flow was high. Element contents in the water were analyzed by inductively coupled argon plasma–mass spectrometry (ICP-MS). The dissolved content ranges were as follows: Ca between 4.47 and 20.7 mg L^–1, Mg between 2.4 and 7.3 mg L^–1, K between 1.13 and 8.6 mg L^–1, and Na between 8.9 and 27.2 mg L^–1. Significant correlations among all the analyzed elements were observed during the entire study period. Mostly, nutrient losses were related to degradation induced by soil erosion on the cultivated land portion of the catchment.     

Arsenic Concentrations in Groundwater,Soils, and Irrigated Rice in Southwestern Bangladesh

Arsenic (As) poisoning of groundwater in Bangladesh has become a major environmental and health issue. The extensive use of groundwater in irrigation of rice has resulted in elevated As in soils and crops. A study was undertaken to determine As concentrations in groundwater, soils, and crops in 16 districts of southwestern Bangladesh. Groundwater samples were collected from shallow-tube and hand-tube wells (STW and HTW) used for irrigation and drinking water. Soil and rice plants were sampled from the command area of the tube wells. Arsenic concentrations were determined using an atomic absorption spectrometer equipped with flow injection hydride generator. Groundwater samples contained <10 to 552 μg As L^?1. Arsenic concentrations in 59% of STW samples exceeded 50 μg As L^?1, the national standard for As in drinking water. Unlike groundwater, most of the surface water samples contained <10 μg As L^?1. Concentrations of As in the soils from the command area of the tube wells ranged from 4.5 to 68 mg kg^?1. More than 85% of the soils contained <20 mg As kg^?1. The mean As concentration in the rice grain samples was 0.23 mg kg^?1, which is much less than the maximum food hygiene standard. A positive relationship was observed between groundwater and soil As, implying that soil As level increases as a result of irrigation with contaminated water. However, irrigation water As did not show any relation with rice grain As. The findings suggest that surface water bodies are a safe source of irrigation water in the As-contaminated areas.     

The effects of low pH,low calcium concentrations and elevated aluminium concentrations on sodium fluxes in brown trout,Salmo Trutta L.

The effects of pH (c. 7.0, 5.4, 4.5 and 4.0), nominal Al levels (0 and 8 μmol L^?1) and Ca levels (10 and 50 μmol L^?1) on Na influx, efflux and netflux of brown trout have been investigated using artificial lake water of known composition. Low pH had little effect on influx, but tended to increase efflux, particularly in the low Ca treatments. A nominal addition of 8 μmol Al L^?1 at pH 4.5 and 4.0 reduced influx significantly. Efflux was unaffected. Aluminium addition at pH c. 7.0 and 5.4 had no such effect. The measured Al concentrations at the end of the static 8 hr flux measuring experiments were markedly lower than the nominal amount of A1 added to the start.     

Calcium and humic acid affect seed germination,growth, and nutrient content of tomato (Lycopersicon esculentum L.) seedlings under saline soil conditions

The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg^?1) and calcium (0, 100, 200 and 400 mg kg^?1) were applied to growth media treated with 50 mg NaCl kg^?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg^?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg^?1 Ca²⁺ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.     

Effect of Excessive Calcium Applications on Growth and Postharvest Performance of Bedding-plant Impatiens

ABSTRACT

Application of excessive amounts of calcium (Ca) during the production cycle improves the quality and postharvest life of several florist crops. Most bedding plants are fertigated with Ca at 100 to 200 mg L^{? 1}throughout the production cycle, but we do not know the effects of higher Ca concentrations. The objective was to evaluate the effect of application of excessive Ca (≥ 280 mg L^?1) supplied during the production cycle on the growth, development, and subsequent postharvest performance of bedding-plant impatiens (Impatiens wallerana Hook. f. ‘Super Elfin White’) under simulated retail conditions. Calcium was applied at 120, 200, 280, 360, and 440 mg L^?1 during each fertigation during the growing cycle. The total nitrogen (N) concentration was 150 mg L^?1, and the nitrate (NO₃ ^?)-N to ammonium (NH₄ ⁺)-N ratio was 1:1. Application of excessive Ca began 30 d after sowing (22 d after germination) and continued until 60 d after sowing. From day 60 to day 65 only deionized water, as a leach, was applied. From day 65 to day 90, plants were held under shade cloth and irrigated with tap water. Excessive Ca applied during the production cycle decreased shoot dry weight, shoot fresh weight, leaf number, and shoot tissue K concentration at the end of the production cycle. Excessive Ca applied during the production cycle also decreased shoot dry weight, leaf number, and shoot tissue potassium (K) concentration at the end of the postharvest period. Plant height, plant diameter, number of open flowers, and number of unopened flower buds at the end of the production cycle and at the end of the postharvest period were not affected by the amount of Ca applied during the production cycle. It was concluded that excessive Ca applied to bedding-plant impatiens during the production cycle did not benefit plant performance during either the production cycle or the postharvest period.