EFFECT OF PETUNIA STOCK PLANT NUTRITIONAL STATUS ON FERTILIZER RESPONSE DURING PROPAGATION

Fertilization strategies during stock plant and cutting production are linked in terms of cutting nutrient levels and quality. Objectives were to evaluate (1) the effect of stock plant nutrition on tissue nutrient concentration and growth during vegetative propagation and (2) response to fertilizer during propagation for cuttings with 4 different initial tissue nutrient concentrations. ‘Supertunia Royal Velvet’ petunia stock plants were grown under constant fertigation of 0, 50, 100 or 200 mg nitrogen (N)^.L^?1 for 21 days. The 200 mg N^.L^?1 solution contained 150 nitrate (NO₃-N), 50 ammonium (NH₄-N), 24 phosphorus (P), 166 potassium (K), 40 calcium (Ca), 20 magnesium (Mg), 0.7 sulfur (S), 1.0 iron (Fe), 0.5 manganese (Mn), 0.5 zinc (Zn), 0.24 copper (Cu), 0.24 boron (B), and 0.1 molybdenum (Mo). Providing a complete fertilizer during propagation of petunia, beginning immediately after sticking of cuttings, reduces the risk of nutrient deficiency. Particularly in situations where fertilizer is not applied early during propagation, stock plants should be managed to ensure unrooted cuttings have adequate nutrient reserves.     

Wheat varietal response to sulfur 1

Abstract

A nutrient solution‐sand culture study was conducted in a greenhouse to evaluate the response of 35 soft red winter wheat varieties to S. Wheat seedlings were grown for 35 days in sand that was leached every other day with complete nutrient solution containing 0, 1 or 5 mg SO₄‐S L^‐1. Herbage yield of 5‐week‐old wheat plants was increased an average of fourfold as the level of s in solution was increased from 0 to 5 mg L^‐1. The concentration of S in the herbage was increased an average of three‐fold as the concentration of s was increased from 0 to 5 mg L^‐1. Differences were observed among varieties for both dry matter and the concentration of S in plant tissue. However, differences among varieties were not consistent at all three levels of s in solution. Sulfur concentration in wheat herbage explained only 24% of the variability in wheat herbage yield. The study did allow for a general grouping of varieties giving the highest, lowest and intermediate yields. Concentrations of Mg, Cu, P, Fe, Mn and Zn were also affected by the level of SO₄‐S.     

The response of a high-yielding canola hybrid to sulfur fertilization in three contrasting Saskatchewan soils

Abstract

Canola (Brassica napus) is the primary oilseed crop in western Canada; however, it is often grown on sulfur (S)-deficient soils. Moreover, canola has a high S demand compared to cereals and, therefore, is particularly sensitive to S deficiency. This study examined the growth and nutrient uptake responses of a high-yielding canola hybrid cultivar to S fertilization when grown on three contrasting soils differing in S fertility, with and without the addition of fertilizer S. The soils were collected from three soil-climatic zones within Saskatchewan (Brown, Black, and Gray) and three different fertilizer S forms were used: ammonium sulfate (AS); ammonium thiosulfate (ATS); and a composite fertilizer containing nitrogen (N), phosphorus (P), and S (NPS; 50-50 blend of sulfate (SO₄) salt and elemental S). Sulfur fertilization increased the canola biomass, along with plant uptake of N, P, and S on all three soils. Fertilizer S use efficiency (i.e. recovery) ranged from 11-75%. For all three soils, the general trend among fertilizer S forms for biomass, nutrient uptake, and fertilizer use efficiency was AS?>?ATS?>?NPS. The greatest differences were observed with the Gray soil, which had the poorest S fertility. Residual soil SO₄ after harvest was greater for ATS and NPS; reflecting continued oxidation of thiosulfate and elemental S to SO₄. Principal component analysis demonstrated the importance of tissue N:S ratio as a key diagnostic measurement related to canola growth and nutrient uptake in S-deficient soils.     

Uptake and nutrient balance of nitrogen,sulfur, and boron for optimal canola production in eastern Canada

Balanced plant nutrition is essential to achieve high yields of canola (Brassica napus L.) and get the best economic return from applied fertilizers. A field study was conducted at nine site‐years across eastern Canada to investigate the effects of nitrogen (N), sulfur (S) and boron (B) fertilization on canola nutrient uptake, nutrient balance, and their relationship to canola yields. The factorial experiment consisted of four N rates of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg ha^?1, two S rates of 0 (S0) and 20 (S20) kg ha^?1, and three B treatments of 0 (B0), 2 kg ha^?1 at preplant (B2.0P), and 0.5 kg B ha^?1 foliar‐applied at early flowering stage (B0.5F). Each site‐year used the same experimental design and assigned treatments in a randomized complete block design with four replications. Fertilizer S application greatly improved seed yields at six out of nine site‐years, and the highest N use efficiency was in the N150+S20 treatment. Sulfur application generally increased seed S concentration, seed S removal, and plant total S uptake, while B fertilization mainly elevated straw B concentration and content, with minimal effect on seed yields. At the early flowering stage, plant tissue S ranged from 2.2 to 6.6 mg S g^?1, but the N : S ratio was over or close to the critical value of 12 in the N150+S0 combination at five site‐years. On average across nine site‐years, canola reached a plateau yield of 3580 kg ha^?1 when plants contained 197 kg N ha^?1, 33 kg S ha^?1 and 200 g B ha^?1, with a seed B content of 60 g B ha^?1. The critical N, S, and B values identified in this work and their potential for a posteriori nutrient diagnosis of canola should be useful to validate fertilizer requirements for canola production in eastern Canada.     

The contribution of sulfate to rainfall pH around Kilauea Volcano,Hawaii

Between December 1986 and June 1987, the mean pH of rainfall downwind of the Kilauea main vent was found to be 4.5 (range 4.0 to 5.6), 1.2 units higher than the year before (1985-86), although 84% of the 12 sequential samples fell below pH 5.0. The SO₄ content, however, was 34% higher, averaging 18.5 mg L^?1. Upwind, in open forest the mean pH 4.7 was little changed from that measured before. Mean SO₄, however, has fallen to a low of 2.5 mg L^?1, but, more significantly, in 9 out of 12 sequential samples S04 was not detectable at all (i.e. < 0.5 mg L^?1). The calculated pH, assuming 100% H₂SO₄ would be 5.3 yet 58% of these samples fell below pH 5.0, the lowest being 4.0. Disparities between pH measured and calculated on the basis of SO₄ content indicated that other acid species were present in the precipitation. Oxidation of rain samples with H₂O₂ greatly increased SO₄ content and lowered pH downwind, but failed in most samples to alter either parameter in the upwind collections. These observations, together with the elimination of HCl and N03 by others, suggested that SO₂ contributes significantly to acidity downwind, but that in most upwind samples a source of H⁺ other than mineral acids, presumably organic compounds, must be of major importance.     

Assessment of Ionic Interferences to Nitrate and Potassium Analyses with Ion-Selective Electrodes

Ion-selective electrodes (ISEs) are simple tools used for rapid measurement of nitrate nitrogen (NO₃-N) and potassium (K) concentrations in plant sap. With the development of best management practices (BMPs), interest exists in using ISEs for soil leachate and soil and fertilizer solutions. Nitrate N and K concentrations in the 0 to 10,000 mg L^–1 ISE working range were measured in diluted solutions of common salts to assess ionic interference of calcium (Ca²⁺), ammonium (NH₄ ⁺), chloride (Cl^–), and sulfate (SO₄ ^2–). The effects of meter (replication) were unexpectedly significant in one out of three ranges for NO₃-N and K (P values of 0.50, 0.72, and 0.01 for NO₃-N and 0.99, 0.01, and 0.74 for K, for the 0–100, 100–1,000 and 1,000–10,000 mg L^–1 ranges, respectively). The responses of calculated NO₃-N and K concentrations to measured NO₃-N and K concentrations were linear, but slopes ranged from 0.85 to 1.54, from 0.24 to 2.72, and from 0.93 to 5.48 for NO₃-N and from 0.80 to 1.01, from 0.71 to 1.39, and from 0.93 to 2.21 for K for the 0–100, 100–1,000, and 1,000–10,000 mg L^–1 measuring ranges, respectively. All slopes were significantly different from zero, and several were significantly different from each other and the 1:1 line. Pairwise slope comparisons conducted with covariance analysis showed that SO₄ ^2– alone interfered with NO₃-N measurements at concentrations ranging from 34 to 171 mg L^–1, which was less than the manufacturer's information, and by its presence in combination with K⁺, NH₄ ⁺, Ca²⁺, and Cl^– within the medium and high concentration ranges. Potassium measurements were not subject to interference from the ions tested for all three concentration ranges. These results highlight the importance of using quality assurance / quality control (QA/QC) samples in the set of unknown samples to detect inacceptable departure from linearity in routine analysis. The increase in measurement variability from one range to the next showed the importance of keeping measurements within a single concentration range by using dilutions. Hence, ISEs may be used for field measurements of NO₃-N and K concentrations in soil leachate as well as soil and nutrient solutions and are therefore a practical BMP tool. However, ISEs should not be used as substitutes for the laboratory methods when official measurements are needed.     

Influence of potassium and magnesium fertilizer application on the yield and nutrient accumulation of maize genotypes under field conditions

The use of maize (Zea mays L.) genotypes that are able to utilize nutrients efficiently is an important strategy in the management of plant nutritional status; it is of particular importance with regard to potassium (K) and magnesium (Mg), due to their high requirement and influence on plant growth. The influence of K and Mg fertilizers on certain growth parameters of maize genotypes TM.815 and KL.72.AA, including length, seed in ear, seed weight growth, and nutrient concentration, was determined under field conditions over two successive years. The aim of the experiment was to study the effect of different rates of K and Mg fertilizers on maize genotype plant growth parameters, grain yield, and nutrient accumulation under field conditions.

A split plot design with three replicates was used and each block contained three treatments of 0, 100, and 200 kg ha^?1 of K₂O and 0, 10, and 20 kg ha^?1 of Mg; K₂SO₄ was used to supply K, and MgSO₄ was used for Mg.

Plants that responded to the K fertilizer had an increase in height, yield, and the concentration of K in the leaves and seeds. The addition of K fertilizer increased the concentration of nitrogen (N), iron (Fe), zinc (Zn), manganese (Mn), and K in the plant leaves and increased seed K concentration. Mg fertilizer increased the concentration of N, Fe, copper, and Mn in the leaves; however, it exerted no significant influence on K concentration. The KL.72.AA maize genotype had a higher mean plant height, number of seeds in ear, yield, and N, K, Fe, and Zn concentrations compared to the TM.815 maize genotype. In the experiment, the K fertilizer exerted a statistically significant effect on the leaf and seed K concentration; however, on a statistical basis, the Mg fertilizer did not affect the Mg concentration.     

Throughfall Chemistry in a Sitka Spruce Plantation in Response to Six Different Simulated Polluted Mist Treatments

A mixed provenance Sitka spruce plantation, planted in 1986 on a drained deep peat, has been exposed to 6 different simulated mist treatments in 4 replicated blocks since 1996. Treatments provided N and/or S at a concentration of 1.6 mol m^?3, supplying ca. 50 kg S and/or N ha^?1 yr^?1 as N (NH₄NO₃), S (Na₂SO₄), NS Acid (NH₄NO₃ + H₂SO₄ at pH 2.5), 2NS Acid (double dose by application at twice frequency), a control treatment supplied with additional rainwater only and a 'no treatment' set of plots. Throughfall, preserved with thymol in the field, was collected using gutters with a surface area of 1 m² in all the replicate plots, and was analysed for all major ions. Prior to treatment in 1999, S deposition in throughfall exceeded that in rain because of dry deposition of SO₂ and SO₄ ^2? to the canopy; NH₄ ⁺ and NO₃ ^? ions were both retained in the canopy. During treatment, only 20–40% of the applied N in the high-N treatments was retained in the canopy. Acidity in the applied mist was partly neutralised by the canopy, but not primarily through exchange of base cations, leading to the conclusion that weak organic acids, in solution or in situ in the canopy, contributed to the buffering of the H⁺ ion deposition in the acid treatments.     

Nitrogen application rates for greenhouse tomato based on real-time diagnosis of petiole sap: Effects of soil nitrate contents before cultivation

(pp. 825–831)

This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L^?1.

For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg^?1 dry soil or higher in the 0–30 cm layer; 38 kg ha^?1 of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg^?1 dry soil; 75 kg ha^?1 of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg^?1 dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L^?1 from early harvest time to topping time under these conditions.     

Fertigation rate,leaching fraction,and growth of potted poinsettia

Single‐pinched poinsettia (Euphorbia pulcherrima ’V‐14 Glory') in 15‐cm pots received constant fertigation with 50, 100, 200, and 300 mg.L^‐1 nitrogen (N) from a 20N‐4.4 phosphorus (P)‐16.6 potassium (K) fertilizer with a leaching fraction (LF) of 0, 0.2, or 0.4. Plants received 25 irrigations during the 13‐week study. The shoot fresh and dry masses with 50, 100, and 300 mg.L^‐1 N at the 0.4 LF were 30% larger than at the 0 LF. The 300 mg.L^‐1 N fertigated plants had approximately 15% more leaf area and almost 122% more bract area than the 50 mg.L^‐1 N fertigated plants. The leaf N concentration of plants fertigated with 100, 200, and 300 mg.L^‐1 N was near or in the normal range of 4 to 6%, but was below the critical level of 3.5% with 50 mg.L^‐1 N fertigation. In contrast, the leaf P concentration approached or exceeded the toxic level of 0.9% with 100 to 300 mg.L^‐1 N. The N fertigation of 100 to 200 mg.L^‐1 is adequate for producing a quality poinsettia crop. Quality poinsettias can be grown at a 0 LF if quality irrigation water is available. With 11 mg.L^‐1 P via fertigation, the leaf P concentration was in the acceptable range. The P concentration in the 20N‐4.4P‐16.6K complete fertilizer was excessive for poinsettia and would contribute to unnecessary P leaching.     

Fertilizer Concentration Affects Growth Response and Leaf Color of Tradescantia virginiana L.

ABSTRACT

A pot experiment was conducted out to investigate the yield and pungency of spring onion (Allium fistulosum L.) as affected by inoculation with arbuscular mycorrhizal (AM) fungi and addition of nitrogen (N) and sulfur (S) fertilizers. Plants were inoculated with either Glomus mosseae or Glomus intraradices or grown as uninoculated controls. Two levels of N and S were applied to the soil in factorial combinations of 50 and 250 mg N kg^?1 soil and 0 and 60 mg S kg^?1 soil. Plants were grown in a greenhouse for 25 weeks and then harvested. Mycorrhizal colonization resulted in increased shoot dry weight, shoot-to-root ratio, shoot length, sheath diameter, and phosphorus (P) concentrations. Shoot dry-matter yield was significantly affected by added N, but not by S. Shoot dry weight increased with increasing N supply (except for non-mycorrhizal controls without additional S fertilizer). Shoot total S concentration (TSC), enzyme-produced pyruvate (EPY), and organic sulfur concentration (OSC) in plants inoculated with Glomus mosseae were significantly lower than those of non-mycorrhizal controls, while these parameters in plants inoculated with Glomus intraradices were comparable to or higher than in the controls. Neither N nor S supply affected shoot EPY or OSC, whereas shoot TSC (except in plants inoculated with Glomus mosseae) and SO₄ ^2? concentrations were usually significantly increased by S supply. In soil of high S and low P availability, mycorrhizal colonization had a profound influence on both the yield and the pungency of spring onion.     

Nutrient uptake in vegetative poinsettias grown with two fertilizer concentrations and two pinching dates 1

The effects of varying fertilizer application rates [100–15–100 or 300–46–300 mg L^‐1 of nitrogen (N)‐phosphorus (P)‐potassium (K)] and pinching dates on nutrient uptake patterns of poinsettias were studied. During the first seven weeks after potting, varying the N‐P‐K fertilization rate from 100–15–100 to 300–46–300 mg L^‐1 N‐P‐K had no effect on plant height, dry weight, nutrient concentration, or nutrient content of poinsettias. The uptake ratios for NO₃‐N, K, calcium (Ca), and magnesium (Mg) all were <40% of the amount that was available at the 100 mg L"¹ N and K fertilization rate, indicating that poinsettias require lower levels of NO₃‐N, K, Ca, and Mg than what was available from the 100–15–100 mg L"¹ N‐P‐K fertilization rate. The higher uptake ratios of >60% and >70%, respectively, for NH₄‐N and P at the 100 mg L"¹ N and K fertilization rate indicated the plants utilized a higher percentage of the available NH₄‐N and P, indicating that an application rate >18 mg L^‐1 NH₄‐N and >15 mg L^‐1 P would be required by poinsettias from the week before the plants were pinched through three weeks after pinching. The 300–46–300 mg L^‐1 N‐P‐K fertilization rate provided excessive nutrients that were not utilized by the plants during the early stages of plant growth.     

Supplements of Nickel Affect Yield,Quality, and Nitrogen Metabolism When Urea or Nitrate is the Sole Nitrogen Source for Cucumber

ABSTRACT

Influences of nickel (Ni) concentrations in the nutrient solution on yield, quality, and nitrogen (N) metabolism of cucumber plants (Cucumis sativus cv ‘RS189’ and ‘Vikima’) were evaluated when plants were grown either with urea or nitrate as the sole N source. The cucumber plants were treated with two N sources, urea and nitrate as sodium nitrate (NaNO₃) at 200 mg L^?1, and three concentrations of Ni as nickel sulfate (NiSO₄·6H₂O; 0, 0.5, and 1 mg L^?1). Treatments were arranged in a randomized block design with six replicates. The highest concentration of Ni in the leaves (1.2 mg kg^?1 Dwt) was observed in the urea-fed plants at 1 mg L^?1 Ni concentration. Additions of Ni up to 0.5 mg L^?1 had no effect on the fruit Ni concentration in the both urea and nitrate-fed plants. Yield significantly (p < 0.05) increased with the Ni supplements from 0 to 0.5 mg L^?1 (10 and 15% in ‘RS189’ and ‘Vikima’, respectively), but decreased when 1 mg L^?1 Ni applied to the solutions in urea-fed plants. Nitrate-fed plants had a higher percentage of total soluble solids compare to those urea-fed plants. Nitrate concentrations of the fruits in urea-fed plants in both cultivars were reduced by approximately 50% compared to those nitrate-fed plants. The reduction of nitrate concentration in the fruits became more pronounced as the Ni concentration increased in the solution. The rate of photosynthesis (Pn) increased with the increase of the Ni concentration in the solution with urea-fed plants. Both N concentration and nitrate reductase (NR) activity of young leaves were higher in urea-fed plants at 0.5 mg l^?1 Ni concentration. Ni supplements enhanced the growth and yield of urea-fed plants by increasing Pn, N concentration and NR activity. It can be concluded that Ni supplements (0.5 mg l^?1) improve yield, quality, and NR activity in urea-fed cucumber plants.     

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.     

Comparative Study of the Leachates from Syngonium podophyllum using Different Fertilization Techniques and Nitrogen Forms

The objectives of this article were to analyze the evolution of the nutrient parameters of the leachates collected from Syngonium podophyllum var. Silver plants cultivated for 20 weeks in a buried greenhouse with four methods of fertilization. The treatments were T₁, standard liquid feeding (SLF) [7.0 mmol L^?1 nitrate (NO₃ ^?) nitrogen (N), 0.3 mmol L^?1 phosphorus (P), and 3.5 mmol L^?1 potassium (K)] after transplanting; T₂, liquid feeding soluble fertilizer (LFSF) [6.9% NO₃ ^? N, 11.1% ammonium (NH₄ ⁺) N stabilized by 3,4-dimethylpyrazole phosphate, 8.0% P₂O₅, and 14.0% K₂O] after transplanting; T₃, controlled release fertilizer (CRF I) (7.4% NO₃ ^? N, 8.6% NH₄ ⁺ N, 8.0% P₂O₅, and 12.0% K₂O) applied before planting and half concentration of SLF from 45 days after transplanting; and T₄, controlled release fertilizer (CRF II) (8.5% NO₃ ^? N, 7.5% NH₄ ⁺ N, 8.0% P₂O₅, and 12.0% K₂O) applied before planting and half concentration of SLF from 45 days after transplanting. Solution pH, electrical conductivity (EC), NO₃ ^? N, NH₄ ⁺ N, K, and P concentrations in the leachate were analyzed weekly. Plant quality was assessed at the end of the trial through objective and subjective parameters. Significant differences among the different fertilization methods were observed. CRF treatments resulted in the greatest nutrient leachate concentration during the first 6 weeks of the study, and afterward it decreased gradually until the end of the cultivation. CRF I showed greater leachate concentrations of N, P, and K than the others during the first half of the study. The concentrations of NO₃ ^? N and P from all the fertilizer types were often above the permissible levels cited in the federal Clean Water Act. The best-quality plants were obtained with CRF II, whereas the greatest height and Aerial Dry Weight (ADW) were obtained with CRF treatments and the greatest Root Dry Weight (RDW) was obtained with the NH₄ ⁺ N treatments.     

Dynamics of aqueous aluminum species in a podzol affected by experimental MgSO4 and (NH4)2SO4 treatments

Chemistry of aqueous Al in a podzol on a Norway spruce (Picea abies [L.] Karst.) site in the Black Forest (SW Germany) and changes induced by experimental applications of MgSO₄ were studied. Soil solution taken from the O, E and BC horizons were analyzed for the fractions ‘labile monomeric Al’, ‘non-labile monomeric Al’, and ‘acid-reactive Al’. The activities of ‘inorganic monomeric Al’ species and the saturation indices (SI) of the soil solution with respect to Al-bearing minerals were calculated using the equilibrium speciation model WATEQF. On the untreated plot, soil leachates are characterized by Al_tot concentrations of 0.1 mg L^?1 (mineral soil). In the O horizon, the fractions ‘acidsoluble Al’ and ‘non-labile monomeric Al’ (mainly organically complexed Al) together comprise 80% of Al_tot. In the leachates from the mineral soil Al³⁺ prevails, being 50% of Al_tot. Al-F-complexes make up 5 to 10% in all horizons. MgSO₄ and (NH₄)₂SO₄ treatments resulted in an intense Al mobilization up to 50 mg L^?1. In this situation, 60% of Al_tot is covered by Al³⁺ and 40% by non-phytotoxic Al-SO₄-complexes. After rainfall events, mobilized Al is quickly translocated into the subsoil, with water flow through macropores then appearing to be an important mechanism. In both treatments, soil solution chemistry was favorable for the precipitation of the Al(OH)SO₄-type minerals alunite and jurbanite. However, a control of Al solubility by this process is not likely due to kinetic restraints. Application of MgSO₄ was followed by an increase of the Mg/Al molar ratio in the soil solution, whereas the Ca/Al ratio decreased. After treatment with (NH₄)₂SO₄ both the Ca/Al and the Mg/Al ratios deteriorated.     

伴随阴离子对马铃薯种植冲击土中钾素固持与淋溶的影响

A column study was carried out to assess the influence of accompanying anions on potassium (K) leaching at potato growing sites with different soil textures (sandy loam and clay loam) in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg^-1 through different sources having different accompanying anions (Cl^-, SO₄^2-, NO₃^- and H₂PO₄^-). Maximum K was retained in the top 0--15 cm layer with a sharp decrease in K content occurring in 15--30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg^-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO₄^2- ≤ H₂PO₄^2- < NO₃^- = Cl^-. Highest 1 mol L^-1 CH3COONH4-extractable K was retained when K was applied along with SO42- and H2PO4- anions, and the least was retained when accompanying anion was Cl^-1. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KCl. After four leachings, the maximum amount of K leached out was 6.40 mg L^-1 in Hundowal clay loam and 9.29 mg L^-1 in Khanaura sandy loam at 60 mg K kg^-1 of soil application through KCl. These concentrations were lower than the recommended guideline of the World Health Organisation (12.00 mg L^-1).     

Partitioning of Newly Absorbed and Previously Stored Nitrogen and Sulfur Under Sulfate Deficient Nutrition

Sulfur (S) deficiency effects on nitrogen (N) and S fluxes during vegetative growth of Brassica napus was investigated by tracing ¹⁵N and ³⁴S for 9 d of S-sufficient [1.5 mM sulfate (SO₄^2-)] and S-deficient (0.05 mM SO₄^2-) condition. A significant decrease in leaf osmotic potential and chlorophyll content was apparent after 9 d of S-deficiency. Sulfur uptake during 9 d was remarkably decreased by 94.3% by S-deficiency, whereas no significant change occurred for N uptake. The N and S deriving from uptake were mainly allocated to the leaves in control plants, but the S flow into leaves was largely restricted under S-deficient condition. The remobilization of stored N and S were mainly issued only from leaves in control plants, while from leaves and petiole in S-deficient ones. The remobilization of N and S mainly issued from leaves flows into the roots both in control and S-deficient plants.     

Nitrite and Ammonium Toxicity on Lettuce Grown under Hydroponics

Abstract

Nitrite (NO₂ ^?‐N) toxicity symptoms have been observed on lettuce (Lactuca sativa) at various locations in California. The objective was to evaluate the symptoms of ammonium (NH₄ ⁺‐N) and nitrite (NO₂ ^?‐N) toxicity on Sundevil iceberg lettuce and Paragon romaine lettuce and to determine lettuce growth and biomass production under different levels of NO₂ ^?‐N. Hydroponic studies under greenhouse conditions were conducted using nutrient solutions containing nitrate (NO₃ ^?‐N) and two other forms of nitrogen (NO₂ ^?‐N and NH₄ ⁺‐N) applied at a constant concentration (50 mg NL^?1) or using different NO₂ ^?‐N levels (0, 5, 10, 20, 30, and 40 mg N L^?1) and a constant NO₃ ^?‐N level (30 mg N L^?1). Crown discoloration (brownish color) was observed for lettuce grown in both NO₂ ^?‐N and NH₄ ⁺‐N solutions approximately 3 weeks after transplanting into the hydroponic systems. Lettuce grown in NO₃ ^?‐N solution produced larger biomass and greater number of leaves per plant than lettuce grown in NO₂ ^?‐N or NH₄ ⁺‐N solutions. Increasing the concentration of NO₂ ^?‐N suppressed plant height, fresh and dry biomass yield, and number of leaves and increased the root vascular discoloration. Lettuce growth was reduced more than 50% at NO₂ ^?‐N concentrations greater than 30 mg N L^?1. Even at 5 mg NO₂ ^?‐N L^?1, growth was reduced 14 and 24% for romaine and iceberg lettuce, respectively, relative to that obtained in nitrate solution. Although concentrations between 5 and 40 mg NO₂ ^?‐N L ^?1 reduced dry biomass similarly for both lettuce types, toxicity symptoms were more severe in iceberg lettuce than in romaine.     

Simultaneous nitrification and diffusion in soil. III. The effects of the addition of ammonium sulphate

The simultaneous nitrification and diffusion of NH₄⁺, applied as ammonium sulphate to laboratory columns, was followed experimentally and with a simulation model. Ammonium was applied as a fertilizer band at levels equivalent to 69 kg N ha^?1 to a 1 cm depth. The concentration profiles of NH₄⁺, NO₃^?, SO^2?₄ and pH were measured in two columns for incubation times of 214 and 286 h. The simulation model provided for the precipitation and ion pair formation of CaSO₄, the adsorption equilibria of NH₄⁺ and soil acid with the soil solid phase, and nitrifier growth and activity. In general, good agreement was found between the experimental and simulated concentration profiles. The effect of CaSO₄ precipitation on the diffusion of N was investigated using model simulations of the diffusion of NH₄⁺ in the absence of nitrification. The simulations suggested that the reactions of SO^2?4 in the soil could markedly affect the spread of NH₄⁺ from a band of (NH₄)₂SO₄.