Effects of root‐zone acidity on utilization of nitrate and ammonium in tobacco plants

Abstract

Tobacco (Nicotiana tabacum L., cv. ‘Coker 319') plants were grown for 28 days in flowing nutrient culture containing either 1.0 mM NO₃ ^‐ or 1.0 mM NH₄ ⁺ as the nitrogen source in a complete nutrient solution. Acidities of the solutions were controlled at pH 6.0 or 4.0 for each nitrogen source. Plants were sampled at intervals of 6 to 8 days for determination of dry matter and nitrogen accumulation. Specific rates of NO₃ ^‐ or NH₄ ⁺ uptake (rate of uptake per unit root mass) were calculated from these data. Net photosynthetic rates per unit leaf area were measured on attached leaves by infrared gas analysis. When NO^‐ was the sole nitrogen source, root growth and nitrogen uptake rate were unaffected by pH of the solution, and photosynthetic activity of leaves and accumulation of dry matter and nitrogen in the whole plant were similar. When NH₄ ⁺ was the nitrogen source, photosynthetic rate of leaves and accumulation of dry matter and nitrogen in the whole plant were not statistically different from NO₃ ^‐ ‐fed plants when acidity of the solution was controlled at pH 6.0. When acidity for NH₄ ⁺ ‐fed plants was increased to pH 4.0, however, specific rate of NH₄ ⁺ uptake decreased by about 50% within the first 6 days of treatment. The effect of acidity on root function was associated with a decreased rate of accumulation of nitrogen in shoots that was accompanied by a rapid cessation of leaf development between days 6 and 13. The decline in leaf growth rate of NH₄ ⁺ ‐fed plants at pH 4.0 was followed by reductions in photosynthetic rate per unit leaf area. These responses of NH₄ ⁺ ‐fed plants to increased root‐zone acidity are characteristic of the sequence of responses that occur during onset of nitrogen stress.     

Effects of phosphate,nitrate and chloride on calcium,magnesium and manganese content of cigar‐wrapper tobacco

Abstract

Nutrient solutions containing three levels of phosphate, nitrate, and chloride were applied to cigar‐wrapper tobacco (Nicotiana tabacum L.) plants growing in sand culture for a period of 18 days. Concentrations of other nutrient elements in the nutrient solutions were held constant and the solutions were applied to pots as needed to maintain favorable moisture conditions for plant growth. Plants were in the two leaf stage when transplanted and were maintained on a single nutrient solution for 38 days before treatments were started. At the end of an eight weeks growing period, plant leaves were harvested and analyzed for Ca, Mg, and Mn. Dry matter yield was significantly (P=0.01) increased when 2 mM/1 of Ca(NO₃)₂ replaced an equivalent amount of Ca(H₂PO₄)₂ or CaCl₂ in the nutrient solution. Nitrate significantly (P=0.05) increased Ca and Mg content and decreased Mn concentration in leaf tissue in comparison to chloride. Calcium and Mg content were significantly (P=0.05) decreased and Mn content of tobacco leaves was increased by phosphate in comparison to nitrate and chloride.     

Effect of ammonium chloride,ammonium sulphate,and sodium nitrate on take‐all and grain yield of wheat grown on soils in South‐western Australia

Five field experiments are described which measured the effect of three sources of nitrogen (N) fertilizer, applied at 45 kg N/ha, on the incidence of take‐all and grain yield of wheat. The N fertilizers were ammonium sulphate, ammonium chloride, and sodium nitrate. Compared with the Nil N treatment, ammonium‐nitrogen fertilizer, either as ammonium sulphate (ASdr) or ammonium chloride (ACdr) drilled with the seed, lowered the severity of take‐all. Sodium nitrate topdressed (SNtd) to the soil surface reduced the severity of take‐all in three of five experiments, while ammonium sulphate topdressed (Astd) reduced the severity in four of the five experiments. Ammonium sulphate and ammonium chloride drilled with the seed were equally effective in reducing the severity of take‐all in three of the five experiments. However, ACdr was more effective than ASdr in reducing the severity of take‐all in one experiment whereas ASdr was more effective than ACdr in another experiment. In these two experiments (1 and 5), the effects of the reduction in take‐all severity between the ASdr and ACdr treatments did not affect grain yield. The results suggest that grain yield losses from take‐all are most severe where wheat plants are deficient in N. Chloride containing fertilizers are unlikely to control take‐all disease of wheat on soils of southwestern Australia.     

Effect of ammonium chloride,ammonium sulphate and sodium nitrate on take‐all and grain yield of wheat in southwestern Australia

Five field experiments measured the effect of three sources of nitrogen (N) fertilizer, applied at 45 kg N/ha, on the incidence of take‐all and grain yield of wheat. The N fertilizers were ammonium sulphate, ammonium chloride and sodium nitrate. Compared with the nil N treatment, ammonium nitrogen fertilizer, either as ammonium sulphate (ASdr) or ammonium chloride (ACdr) drilled with the seed, lowered the severity of take‐all. Sodium nitrate topdressed (SNtd) to the soil surface reduced the severity of take‐all in three of the five experiments, while ammonium sulphate topdressed (AStd) reduced the severity in four experiments. Ammonium sulphate and ammonium chloride drilled with the seed were equally effective in reducing the severity of take‐all in three of the five experiments. However, ACdr was more effective than ASdr in reducing the severity of take‐all in one experiment, whereas ASdr was more effective than ACdr in another experiment. In experiments 1 and 5, the reduction in take‐all severity between the ASdr and ACdr treatments did not affect grain yield. Results suggested that grain yield losses from take‐all are most severe where wheat plants are deficient in N. Fertilizers containing chloride are unlikely to control take‐all disease of wheat on soils of southwestern Australia.     

Tomato responses to ammonium and nitrate nutrition under controlled root‐zone pH

Tomato (Lycopersicon esculentum L. Mill. ‘Vendor') plants were grown for 21 days in flowing solution culture with N supplied as either 1.0 mM NO₃ ^‐ or 1.0 mM NH₄ ⁺. Acidity in the solutions was automatically maintained at pH 6.0. Accumulation and distribution of dry matter and total N and net photosynthetic rate were not affected by source of N. Thus, when rhizosphere acidity was controlled at pH 6.0 during uptake, either NO₃ ^‐ or NH₄ ⁺ can be used efficiently by tomato. Uptake of K⁺ and Ca²⁺ were not altered by N source, but uptake of Mg²⁺ was reduced in NH₄ ⁺‐fed plants. This indicates that uptake of Mg²⁺ was regulated at least partially by ionic balance within the plant.     

Comparison of ion chromatography and a continuous‐flow technique for analysis of chloride and sulfate in plant samples

Abstract

A comparison of ion chromatography and continuous‐flow colorimetry for the determination of chloride and sulfate content in water extracts of plants is presented. Results of the two methods correlate well. The relationships are linear, with a slope of 0.72 for sulfate and 0.73 for chloride. The correlations indicate that the techniques and instruments used are compatible so that the regression equations are satisfactory for conversion of data.     

Effect of N‐form on growth and nutrient content of creeping bentgrass 1

Abstract

The primary nitrogen forms utilized by plants are ammonium and nitrate. Although the importance of nutrients other than nitrogen for proper turfgrass growth is well established, the amounts of these nutrients in the plant tissue in relation to the use of different N‐forms has not been clearly documented. This study was conducted under greenhouse conditions to determine the effect of N‐form and cutting regime on growth, macronutrient, and micronutrient content of creeping bentgrass (Agrostis palustris Huds. ‘Penncross'). Treatments consisted of 100% NO3^? (calcium nitrate), 100% NH₄ ⁺ (ammonium sulfate), and a 50:50 ratio of NH₄ ⁺:NO₃ ^?. Half the turfgrass plants were maintained at a height of 1 cm (cut), while the other half of the plants were not cut until the end of the study (uncut). The uncut 50:50 treatment yielded the highest shoot, verdure, and total plant dry matter, while the uncut NO₃ ^? treatment produced the highest root dry matter. The uncut NH₄ ⁺ treatment yielded the least shoot, root, and total plant dry matter. Plants of the uncut NO₃ ^? treatment had greater accumulation of macronutrients in the shoot and root tissue compared to plants of the NH₄ ⁺ treatment. The uncut NO₃ ^? and 50:50 treatments had higher total accumulation of micronutrients compared to the uncut NH₄ ⁺‐treated plants. The cut NO₃ ^? treatment resulted in the highest macronutrient and micronutrient contents in the root tissue in comparison to other cut treatments. The cut treatments had the highest percentage accumulation of nutrients in the verdure tissue, while the uncut treatments had the highest percentage accumulation of nutrients in the shoot tissue.     

Effect of zinc levels on phosphorous and zinc content in sand‐cultured soybeans

Soybeans (Glvcine max L.) cv. “Clark”; were grown in the greenhouse in sand‐filled plastic pots sub‐irrigated with Hoagland No. 1 solution to determine the possible inhibitory effects of Zn on the uptake of P. Zinc rates used were 0.05 (control), 0.25, 0.5 and 2.5 ppm. Yields equalled the control at Zn levels of 0.25 and 0.5 ppm, but plants grown in solutions containing 2.5 ppm Zn were stunted severely. Foliar Zn and P levels differed very little among Zn treatments. Zinc levels were highest and P levels were lowest, however, in the roots and stems of soybeans grown in solutions of 2.5 ppm Zn. Zinc and P uptake was significantly inhibited in the leaves, stems and roots of plants grown at the highest Zn rate. The recycling of wastes containing high Zn content could adversely affect plant growth by a suspected antagonism with P.     

Variability of soil water content controlled by evapotranspiration and groundwater–root zone interaction

The central moments of soil water content (SWC) variability at the field scale are determined by soil texture, considering both smooth topography and groundwater table position. The characteristics of variability are governed by other soil factors like soil structure, micro relief, preferred water flow paths, root system characteristics, rock content, etc. This paper shows the integral effect of all these hardly quantifiable factors on SWC variability simulated by the processes of evapotranspiration and groundwater–root zone interaction using the HYDRUS ET model. SWC and soil hydraulic characteristics were spatially determined over a 4.5 ha field during two sampling campaigns under different atmospheric and groundwater conditions, and data distributions were compared to SWC distributions provided by mathematical modeling. The entire spring–summer period of 2003 was then examined for changes of SWC spatial variability. It was found that evapotranspiration influences SWC spatial variability only if SWC is under the critical value when wetter parts of the field evaporate more water than drier parts, resulting in smoothed SWC variability. Under wet conditions the spatial variability of SWC increases by drainage, as those parts of the soil with coarser texture drain faster than finer-textured parts.     

Influence of nitrate‐nitrogen and ammonium‐nitrogen on calcium (45Ca2+) absorption in sorghum root tips

Abstract

Root‐tip, 1‐cm of Sorghum bicolor (L.) Moench cv SC283, SC574, GP‐10, and Funk G522DR were exposed to calcium (⁴⁵Ca²⁺) at pH 5.5 for 2‐hr in the presence of nitrate‐nitrogen (NO3^?‐N) or ammonium‐nitrogen (NH4+‐N). Nitrate (0.1 mM) induced significantly increased ⁴⁵Ca uptake in Funk G522DR, SC283, and GP‐10 while 0.01 mM NO₃ ^?‐N induced significantly increased ⁴⁵Ca'uptake in SC574, but ⁴⁵Ca absorption was significantly decreased at 1 mM NO₃—N. In the presence of the NH4⁺ ion, ⁴⁵Ca uptake was increased up to 8X that of the NH₄ ⁺‐N untreated roots. When ammonium chloride (NH₄CI) was used, the Cl^? tended to induce an increased ⁴⁵Ca uptake. Cultivar variation was present.     

A re‐examination of exchangeable acidity as extracted by potassium chloride and potassium fluoride

Abstract

In order to better understand some of the factors likely to affect measurements of KC1 extractable acidity, experiments were conducted using synthetic solutions and extracts from a wide range of contrasting soils. The reagents used for measuring exchangeable acidity (i.e., KC1 and KF) were also examined to evaluate the effects of chemical impurities on acidity measurements. Two commonly used titrimetric methods were adapted and tested to determine the accuracy and precision of acidity measurements. The exchangeable acidity of soil extracts was investigated by extraction methods, extractant concentration, and extractant volume. Results from the soil extract experiments indicated that continuous shaking has no significant effect on acidity measurements. Filtration, however, is critical, especially for acidic organic‐rich soils, since aluminum (Al) ions can be lost during centrifugation. Extractant concentration and volume had variable effects on the acidity measurements for individual soils. In general, the modified Yuan's method is preferable to the modified Thomas’ method for estimating exchangeable Al. To ensure successful determination of exchangeable acidity, we recommend using a wider KCl:soil ratio (>15:1, v/w) for organic soils with low base saturation and allophanic Andisols. In sum, potassium chloride and potassium fluoride extraction for estimating exchangeable acidity is applicable for most soils.     

Nitrate versus chloride nutrition effects in a soil‐plant system on the growth,nitrate accumulation,and nitrogen,potassium, sodium,calcium, and chloride content of carrot

The experiment was conducted to evaluate the effects of various nitrate/ chloride (NO₃/Cl) ratios on growth, nitrate accumulation, and mineral absorption in carrot, Daucus carota L., plants in a controlled environment. The experiment included two Cl sources [potassium chloride (KC1) and calcium chloride (CaCl₂)] and five NO/Clratios at 100/0, 90/10, 80/20, 70/30, and 60/40 with total‐nitrogen (N) concentration of 400 mg NO₃ kg^‐1 soil in 100/0 treatment. Fresh and dry weights of shoots and storage roots, and length and diameter of storage roots increased significantly with mixed NO₃/C1 treatments with both Cl sources as compared to single NO₃ (100/0) treatment. Growth was enhanced up to the 80/20 NO₃/C1 treatments. With Cl present in the treatments, the concentration of total‐N unchanged and NO₃ decreased in plants, and Cl and potassium (K) increased with the Cl sources. In KC1 treatments, Na absorption decreased. Calcium (Ca) content of the plants significantly differed by the treatments. It was concluded that N fertilization provided with combined Cl forms and NO₃/Cl rates can enhance production of better quality carrot and at the same time decrease of the N fertilizer input.     

Effect of aluminum on soybean nodulation and nodule activity in a vertical split‐root system

Soybean plants (Glycine max L. cv Santa Rosa) grown hydroponically in nutrient solutions had reduced nodule mass and numbers in the presence of aluminum (Al). Reduced nodule number was attributed mainly to hydrogen (H) ion toxicity, whereas Al had a stronger effect on nodule growth. Using a vertical split‐root system with Al exclusively in the lower (hydroponic) layer also resulted in a significant reduction of nodulation and nodule growth in the surface compartment (vermiculite). This indirect effect could be attributed mainly to Al rather than H. Subsurface Al had no apparent effect on shoot growth or root growth of the upper compartment, but significantly limited root growth in the lower compartment where it was applied. The indirect effect of Al on nodulation could be a reflection of the abnormal root growth in the lower compartment. Split‐root experiments with a high Al soil, however, produced different effects. High Al in soil used exclusively in the lower compartment did not reduce nodule numbers or mass in the upper compartment despite being more harmful than the Al solutions to nodulation and growth of plants when used in a single compartment. Growth of roots in the subsurface compartment was also much less affected by the high soil Al compared with the Al‐containing nutrient solutions. Nodule activity, as estimated by xylem sap ureide levels, was only reduced after direct exposure of nodules to Al. A pronounced increase in the ratio of asparagine/glutamine occurred in all Al treatments where nodulation was reduced, and in some cases, there was an increase in total amino acid concentration of the xylem sap.     

Comparison of mehlich 3, mehlich 1, ammonium bicarbonate‐DTPA, 1.0M ammonium acetate,and 0.2M ammonium chloride for extraction of calcium,magnesium, phosphorus,and potassium for a wide range of soils

Abstract

Extractants employed for routine soil analysis vary from one laboratory to another. Lack of a universal soil extractant is a serious limitation for interpretation of analytical results from various laboratories on nutritional status of a given soil. This limitation can be overcome by developing functional relationships for concentrations of a given nutrient extractable by various extradants. In this study, extractability of Ca, Mg, P, and K in a wide range of soils (0–15 cm) from citrus groves in Florida representing 21 soil series, with varying cultural operations, were compared using Mehlich 3 (M3), Mehlich 1 (M1), ammonium acetate (NH₄AOc), pH = 7.0 (AA), 0.2M ammonium chloride (NH₄Cl), and ammonium bicarbonate‐DTPA (AB‐DTPA) extractants. Soil pH (0.01M CaCl₂) varied from 3.57 to 7.28. The concentrations of Ca or Mg extractable by M3, M1, AA, and NH₄Cl were strongly correlated with soil pH (r² = 0.381–0.482). Weak but significant correlations were also found between AB‐DTPA extractable Ca or Mg and soil pH (r² = 0.235–0.278). Soil pH relationships with extractable K were rather weak (r² = < 0.131) for M1 and NH₄Cl but non‐significant for M3, AB‐DTPA, and AA. Concentrations of Ca, Mg, and K extractable by M3 were significantly correlated with those by either M1, AA, or NH₄Cl extractants. Mehlich 3‐P was significantly correlated with P extractable by M1 extractant only. Mehlich 3 versus AB‐DTPA relationship was strong for K (r² = 0.964), weaker for Mg and P (r² = 0.180–0.319), and non‐significant for Ca. With the increasing emphasis on possible use of M3 as an universal soil extractant, data from this study support the hypothesis that M3 can be adapted as a suitable extractant for routine soil analysis.     

Simultaneous determination of soil aluminum,ammonium‐ and nitrate‐nitrogen using 1 M potassium chloride extraction

Abstract

Determination of soil aluminum (Al), ammonium‐nitrogen (NH₄‐N), and nitrate‐nitrogen (NO₃‐N) is often needed from the same soil samples for lime and fertilizer recommendations, but Al has to be extracted and quantified separately from NH₄‐N and NO₃‐N according to present methods. The objective of this study was to develop a reliable method for simultaneous analyses of soil Al, NH₄‐N and NO₃‐N using a Flow Injection Autoanalyzer. Thirty‐five soil samples from different locations with wide ranges of extractable Al, NH₄‐N and NO₃‐N were selected for this study. Aluminum, NH₄‐N and NO₃‐N were extracted by both 1 M and 2 M potassium chloride (KCl), and quantified using a LACHAT Flow Injection Autoanalyzer simultaneously and separately. One molar KCl was found to be a suitable extractant for all three compounds when compared to 2 M KCl. The 1 M KCl extract proposed could aid in decreasing the costs associated with simultaneous NH₄‐N, NO₃‐N, and Al analyses. Results of those three compounds analyzed simultaneously were not statistically different from those analyzed separately in 1 M KCl solution. This new procedure of simultaneous determination of NH₄‐N, NO₃‐N, and Al increases efficiency and reduces cost for soil test laboratories and laboratory users.     

Effect of sulfur and molybdenum levels on growth,nitrate‐assimilation,and nutrient con‐tent of Phalaris

An experiment was conducted with Phalaris aquatica L. cv. Sirolan under hydroponic conditions in the glasshouse at constant temperature of 25°C and natural sunlight. Plants were grown in double pot system with four sulfur and three molybdenum levels along with all the major‐ and micro‐nutrient elements. There was increase in growth, nitrate‐reductase activity and contents of most of the nutrient elements at all levels of sulfur and 1.68 μ/L molybdenum. Molybdenum at 3.36 μg/L level inhibited growth and nitrate‐reductase activity and decreased concentration of nutrient elements in plant. The inhibitory effect of higher level of molybdenum is perhaps mediated through its role in the nitrate‐reductase.     

Comparison of ammonium bicarbonate‐DTPA,ammonium carbonate,and ammonium oxalate to assess the availability of molybdenum in mine spoils and soils

Abstract

A variety of extractants has been used to assess the availability of molybdenum (Mo) in soils. Most of the extractants have been studied from a deficiency aspect rather than for soils with Mo toxicity, and none of them have been used to extract available Mo from mine spoils. The purpose of this study was to examine the potential of different chemical extractants for assessing the availability of Mo in mine spoils and soils. One mine spoil and three soils were treated with sodium molybdate and then subjected to wetting and drying cycles for two months. These spoil/soils were extracted with ammonium bicarbonate DTPA (AB‐DTPA), ammonium carbonate, and ammonium oxalate solution for available Mo. Crested wheatgrass (Agropyron cristatum) and alfalfa (Medicago sativa) were grown in the spoil/soils in a greenhouse to determine plant uptake of Mo. Additionally, four mine spoils and six soils were extracted and analyzed for available Mo as mentioned above. The results obtained by these three extractants were highly correlated. It was found that ammonium oxalate extracts the greatest amount of Mo among the three extractants from spoil/soils since it dissolves some adsorbed Mo from Fe‐oxide and Al‐oxide. The changes in pH of spoil/soils did not have a significant effect on the amount of Mo extracted by any of these methods. The relationships between Mo uptake and Mo extracted by each method were all significant at 1% level. None of the extractants were clearly better or worse than the others. All three methods can be used to assess Mo availability, and potential toxicity from plant uptake of Mo from reclaimed spoils.     

Proton consumption and release of organic‐cabon,silicate, and sulfate by anion sorption on andosols

Abstracts

Three anion (selenite, phosphate, and fluoride) sorption, and the concomitant release of silicate, sulphate, and organic matters from soils, and proton consumption with sorption were investigated using two andosols in Japan. The following sequence of sorption by the andosols was, fluoride (F) >> phosphate (P) > selenite (Se); concomitant proton consumption with sorption, F >> P > Se; organic matter released, P > Se > F; and sulfate released, P > Se >> F. There was quite a difference between an allophanic and a non‐allophanic andosols in silicate released with anion sorption. Our results suggest that the fluoride sorption mechanism is different from the others and that surface sites with OH groups for inner‐sphere complexes with selenite on soil particles which are restricted as compared to phosphate and fluoride.     

Element absorption by sorghum root tips as influenced by multiple ion‐channel and ion‐pump inhibitors

Mineral nutrient absorption by 1‐cm root tips of Sorghum bicolor (L.) Moench. cv GP‐10, SC283, SC574, and/or Funk GS22DR from a 1‐hr exposure to Hoagland and Arnon complete mineral nutrient solution in the presence of diltiazem (0,10 mM), nifedipine (0,10 mM), or SITS (0, 1 mM) was evaluated using inductively coupled plasma emission photometry (ICP). Calcium (Ca²⁺) ‐ channel blockers (i.e. ‐ diltiazem, nifedipine, and verapamil) and PCMBS induced significantly decreased quantities of Ca²⁺ in root tips but the anion channel blocker, SITS, did not induce any response in Ca²⁺ uptake. Responses of phosphorus (P), zinc (Zn), boron (B), manganese (Mn), iron (Fe), magnesium (Mg), and copper (Cu) to all of the ion uptake modifiers were highly variable between the cultivars with increased, decreased, or no influence on ion uptake. As yet unrecognized multiple mechanisms of ion uptake through the root plasma membrane are necessary to explain the date.     

Cobalt‐induced stress in tomato plants: Effect on yield,chlorophyll content,and nutrient evolution

An experiment developed in soilless culture was used to study the effect of several levels of cobalt (Co) (0, 5, 15, and 30 mg.L^‐1) on yield and nutrient evolution of the tomato fruits (Lycopersicon esculentum M. cv. Ramy). The incidence of this pollutant in leaf chlorophyll contents was also studied. Increasing concentration of Co in nutrient solution reduced drastically yield in tomato plants. Total, a and b chlorophyll contents were affected by Co level in nutrient solution. A significant increase of nitrogen (N), phosphorus (P), calcium (Ca), and copper (Cu) in the fruit in function of Co treatments were observed. Similar evolution in iron (Fe) and manganese (Mn) fruit content affected by Co presence in higher treatment were obtained. No significant effect of Co presence on potassium (K), magnesium (Mg), sodium (Na), and zinc (Zn) fruit contents were observed. Cobalt absorption was very high, with values of Co in fruit around 250 μg Co g^‐1.