Nutrient uptake and yield of sweet pepper as affected by stage of development and N form

Uptake of NO₃ ^‐, NH₄ ⁺, P, K⁺⁺, Ca⁺⁺ and Mg⁺⁺, as influenced by the stage of plant development and three NO₃ ^‐: NH₄ ⁺ ratios (1: 0, 1: 1, and 0: 1), was determined for sweet pepper (Capsicum annuum L. cv. ‘California Wonder'). Uptake was highest during fruit development and immediately after fruit harvest, indicating that fruit removal promotes nutrient uptake. When NO₃ ^‐ and NH₄ ⁺ were supplied in equal concentrations, NO₃ ^‐ was absorbed more readily. Each increment in NH₄ ⁺ decreased the uptake of K⁺, Ca⁺⁺, and Mg⁺⁺ by fruit tissue, while no significant effect on the N and P content of the fruit was observed. Ammonium nutrition reduced plant dry weight and fruit yield in comparison to NO₃ ^‐. Results from this study suggest that NO₃ ^‐ is the preferred N form, and that fertilizer application should be scheduled according to specific physiological stages to maximize nutrient uptake. Nutrient content of vegetative tissue was not indicative of potential yield.     

Calcium uptake and concentration in bell pepper plants as influenced by nitrogen form and stages of development

Calcium uptake by bell pepper (Capsicum annuum L. cv. ‘California Wonder') varied by stage of plant development and N form supplied (NO₃ ^‐NH₄ ⁺ ratios: 1:0, 3:1, 1:1, 1:3, and 0:1) in a hydroponic study. Uptake of Ca⁺⁺ was highest at bloom and during fruit expansion, making the fruit development stage the highest demand period. Calcium uptake declined with each increasing increment of NH₄ ⁺ relative to NO₃ ^‐ supplied, although fruit yield was not significantly reduced until the ratio of NH₄ ⁺ to NO₃ ^‐ exceeded 50%. Tissue Ca⁺⁺ levels in the blossom‐end of the fruit were reduced whenever NH₄ ⁺ was included with N supplied. Vegetative yield of plants followed the same trend as that observed for total fruit dry weights. Our results indicate that pepper yields are higher when NO₃ ^‐ is the predominant form of N. Also, these results strongly suggest that Ca⁺⁺ fertilizer applications should precede the bloom period and continue during fruit development to ensure adequate Ca⁺⁺ availability for fruit development.     

Effect of nitrogen form during the flowering period on zucchini squash growth and nutrient element uptake

Zucchini squash (Cucurbita pepo L. cv. Green Magic) plants were grown hydroponically with nitrate (NO₃):ammonium (NH₄) ratio of 3:1 until the onset of flowering when the plants were assigned to four NO₃:NH₄ ratio (1:0, 1:1, 1:3, or 3:1) treatments. Changing the original nitrogen (N) form ratio significantly affected plant growth, fruit yield, nutrient element, and water uptake. Growth of plants was better when NO₃‐N (1:0) was the sole form of N than when NH₄‐N was part of the N treatment. Fruit yields for plants fertilized with 1:0 or 1:3 N‐form ratio were double those of plants grown continuously with 3:1 N ratio. The largest leaf area and plant water use were obtained with 1:0 N ratio treatment Total uptake of calcium (Ca), magnesium (Mg), and potassium (K) decreased with increasing NH₄‐N proportion in the nutrient solution which suggest NH₄‐N was competing with these cations for uptake. The results also demonstrated that growers may increase fruit yield by using a predominantly NO₃‐N source fertilizer through the vegetative growth stage and by shifting the NO₃:NH₄ ratio during the reproductive phase.     

PANSY FLORAL DEVELOPMENT AND NUTRIENT ABSORPTION AS INFLUENCED BY TEMPERATURE,NITROGEN FORM,AND STAGE OF PLANT DEVELOPMENT

Production temperatures can affect the marketability of pansies (Viola × wittrockiana Gams.) by influencing plant growth, the presence of nutrient disorders, and the rate of floral development. The choice of nitrogen (N) form in fertility can also influence pansy growth and nutrition, but the effect of fertility on pansy flowering is not clear. Whether or not temperature and N fertility work together to influence nutrient absorption at different stages of the pansy life cycle is unknown. Our objectives were to determine the influence of temperature and N form on pansy floral development, and to identify the peak nutrient demand periods at different temperatures and ratios of NO₃ ^? to NH₄ ⁺ in fertility. Pansies cv. ‘Crown White’ were grown in nutrient solution cultures until lateral branches had open flowers. Treatments consisted of two temperatures (12°C and 22°C) and three stages of floral development (five true leaf stage until visible bud, visible bud until first flower, first flower until flowering on lateral branches), and three NO₃ ^? :NH₄ ⁺ molar % ratios (100:0, 62:38, 25:75) with a total concentration of 100 mg N L^?1. A modified Hoagland's solution was used with NO₃ ^??N supplied as Ca(NO₃)₂ and KNO₃ and with NH₄ ⁺?N as (NH₄)₂SO₄. The effects of temperature and N form on the time required for development of different floral stages were assessed. In addition, the influence temperature and N form on nutrient absorption was determined for three pre‐determined stages of floral development to identify peak nutrient demand periods. The timing of flower bud development and first flower was not influenced by treatments. At 22°C, pansies flowered earlier on lateral branches than at 12°C, but these plants also suffered a loss in quality due to unfavorable growth characteristics and the development of nutritional disorders. Individual absorption of plant nutrients at different stages of development varied with temperature and N regime. Overall, pansies absorbed the greatest quantity of magnesium (Mg) before flower bud development, calcium (Ca) after flower bud development, and NH₄ ⁺, NO₃ ^? phosphorus (P), and potassium (K) after anthesis. In addition, pansies absorbed more NO₃ ^?, Ca, Mg, and P at 12°C than at 22°C. At times, the absorption of NO₃ ^? was dramatically decreased with increasing NH₄ ⁺ in solutions. Results suggest that nutrient absorption by pansy in different stages of development is influenced by production temperatures and the choice of N form in fertilization. Adjusting fertility programs according to peak demand periods and production temperatures will help prevent periodic nutrient disorders during the life cycle, and may reduce fertilization costs.     

Influence of ammonium: Nitrate ratios on the growth and nitrogen uptake of pearl millet

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a potentially high‐yielding grain crop for the Southern Coastal Plain region of the USA. Information on the growth and N nutrition of pearl millet is limited; therefore, this study was initiated with the objective of studying pearl millet growth, N content, N uptake patterns and N‐form preference. Plants were grown in solution culture using a modified Hoagland's solution. Solutions were changed weekly and transpirational losses replaced daily. The N‐form ratios were 1:0, 3:1, 1:1, 1:3 and 0:1 NH₄ ⁺ to NO₃ ^‐ Uptake was determined by difference between the initial and final solutions. Nitrate and NH₄ ⁺ uptake patterns were different from each other and were influenced by the ratio of NH₄ ⁺ to NO₃ ^‐. After the plants had been transferred to the solutions, ammonium was preferred for the first two weeks, with NO₃ ^‐ preferred thereafter. Nitrate uptake was highest during the grain filling period. Plant growth as measured by leaf, stem, root, and seed weight, plant height, average seed weight, and head length was generally reduced as NH₄ ⁺ increased. The largest reduction was observed between the 3:1 and 1:0 ratios. Ammonium nutrition had an overall negative effect on pearl millet growth. Ammonium fertilization of pearl millet under conditions that increase absorption of NH₄ ⁺ over NO₃ ^‐ may have a negative effect on pearl millet growth and development.     

Influence of plant age on calcium stimulated ammonium absorption by radish and onion

Abstract

The efficient use of N for crop production is important because N is normally the most expensive fertilizer input. Past research has suggested that Ca⁺⁺ can be used to stimulate NH₄+ absorption by plants. The importance of plant growth stage in relation to this phenomenon has not been examined previously. The objectives of this study were to examine Ca⁺⁺ ‐ stimulated NH₄ ⁺ absorption and to examine the effect of Ca⁺⁺ concentration on N content and growth in plant tops, bulbs and roots at different growth stages. Ammonium absorption experiments were conducted in the greenhouse in 4‐L pots containing 3.5 kg of calcareous Gila sandy loam (Typic Torrifluvents) (CEC <1 cMol kg^?1). Plants (Radish, Raphanus sativas L., and onion, Allium cepa L.) were grown with a uniform nutrient solution (1/2 strength nutrient solution, all N as NO₃) to the desired growth stage at which time the soil was leached with deionized water. Afterwards, the soils were fertilized with 1/2 strength nutrient solutions (5 mol m^?3 NH₄) with Ca⁺⁺: NH₄ ⁺ molar ratios of 0, 0.25, 0.50, 1.00, and 2.00 for a period of 30 h. As Ca⁺⁺ concentration increased, NH₄ ⁺ absorption and plant growth increases were greatest with young seedlings. In the intermediate and mature growth stages, Ca⁺⁺ stimulated ¹⁵NH₄ ⁺ absorption was less rapid than in the earlier growth stages but frequently exhibited a different response (i.e., altered metabolite translocation) to the added Ca⁺⁺ ‐ concentration. However, at the intermediate and mature growth stages significantly increased N contents and plant growth also were noted in most cases. The Ca⁺⁺ ‐ increased N content in leaves and bulbs of the older plants had much less ¹⁵N suggesting that the newly absorbed ¹⁵NH₄ ⁺ was being deposited in the roots replacing older N forms that were then translocated to the bulbs or leaves. Thus, increasing Ca⁺⁺ appeared to have anadditional function of increasing the mobility of metabolites (dry matter) from the roots. Since more above‐ground plant products were produced with the same amount of N, plant N use efficiency was increased.     

Influence of ammonium,nitrate, and chloride on solution pH and ion uptake by ageratum and salvia in hydroponic culture

The influence of nitrogen (N) forms and chloride (Cl) on solution pH and ion uptake in the hydroponic culture of Ageratum houstonianum [ammonium (NH₄ ⁺)‐tolerant] and Salvia splendens (NH₄ ⁺‐sensitive) for a period of 216 hours was investigated. The pH of the hydroponic solution (initially 6.50) containing either NH₄ ⁺ or NH₄ ⁺+nitrate (NO₃ ^‐) was drastically lowered (3.08), whereas that of the same solution containing NO₃ ^‐ was raised (7.74). Solution pH changed more by ageratum than by salvia. The solution Cl^‐ concentration did not influence pH significantly. However, addition of Cl^‐ in the solution lowered transpiration rate in both NH₄ ⁺ and NO₃ ^‐ treatments. Total N uptake was the greatest in the NH₄ ⁺ + NO₃ ^‐ treatment and the lowest in the NO₃ ^‐treatment. In the NH₄ ⁺ + NO₃ ^‐ treatment, NO₃ ^‐ uptake was suppressed by NH₄ ⁺ (to about 50%), while NH₄ ⁺ uptake was not affected by NO₃ ^‐. The rate of Cl^‐ uptake was the lowest in the NH₄ ⁺ treatment, but was similar in the NH₄ ⁺ + NO₃ ^‐ and NO₃ ^‐ treatments. Uptake of potassium (K⁺), dihydrogen phosphate (H₂PO₄ ^‐), sulfate (SO₄ ^‐2), manganese (Mn⁺²), and zinc (Zn⁺²) was significantly enhanced in the NH₄ ⁺ treatment. The uptake rate of calcium (Ca⁺²) and magnesium (Mg⁺²) was the highest in the NO₃ ^‐ treatment. Absorption of copper (Cu⁺²) and boron (B) was not affected by N source. Ion uptake was more stable in the solution containing both NH₄ ⁺ and NO₃ ^‐ than in the solution containing either NH₄ ⁺ or NO₃ ^‐. The uptake rate of total N, NH₄ ⁺, NO₃ ^‐, Mn⁺², Cu⁺², and Zn⁺² was higher, whereas that of Cl^‐ and molybdenum (Mo) was lower in ageratum than in salvia. Amounts of total anion (TA) and total cation (TC) absorbed, the sum of TC and TA, and the difference between TC and TA (TC‐TA) were affected by N source, Cl^‐ level, and their interactions. The NO₃ treatment, as compared to the NH₄ ⁺ or the NH₄ ⁺ + NO₃ ^‐treatment, reduced total cation and anion uptake while increasing TC‐TA, especially in the absence of Cl^‐. Plant tissue ion contents were also affected by N source and Cl^‐ level.     

Potassium,nitrogen, ammonium/nitrate ratio,and sodium chloride effects on wheat growth

Fertigation with KNO₃ as a means of reducing salinity hazards was tested with peanut (Arachis hypogaea) plants grown on dune sand, resulting in a reduction of plant growth and yield. The objective of this work was to study the interactions between N, K⁺ and NaCl as well as the effects of the NH₄ ⁺/NO₃ ^‐ ratio on vegetative and reproductive growth. Wheat (Triticum aestivum L.) plants were grown in polyethylene pots with fine calcareous dune sand with different proportions of NH₄ ⁺ and NO₃ ^‐, under saline (60 mM NaCl) and non‐saline conditions. Three replicates were harvested at the beginning of flowering, and one was grown to grain maturity. NaCl reduced shoot dry weight in all the treatments. Increasing the NH₄ ⁺ proportion in the total of 6 mM N in the nutrient solution, increased shoot dry weight, did not change nitrogen concentration in the dry mass but increased P percentage, either with or without 60 mM NaCl. The number of tillers produced in each treatment was correlated with dry matter yield. The effect of the NH₄ ⁺/NO₃ ^‐ ratio may be explained by alteration of the cation‐anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH₄ ⁺ concentration, by alteration of the cation‐anion balance on the nutrient uptake by roots, which lowered pH of the nutrient solution with increasing NH₄ ⁺ concentration.     

Influence of nitrogen forms and levels on the growth and nutrition of cacao

Ammonium and nitrate are the major forms of nitrogen (N) present in tropical soils. An experiment was conducted to assess the influence of nitrate and ammonium forms (NO₃^?, NH₄⁺, and mix of NO₃^? + NH₄⁺), and levels (1.5–12.0 mM) of N on the growth and nutrition of cacao (Theobroma cacao L). Growth parameters were significantly influenced by N forms, and nitrogen supplied as NH₄⁺ proved better for the growth of cacao compared with NO₃^? form and mixtures of these two forms. Irrespective of the forms of N, levels of N had no significant effect on plant growth parameters. Nutrient efficiency ratios (NERs) (shoot dry matter produced per unit of nutrient uptake) for macronutrients were sulfur>phosphorus>calcium>magnesium>nitrogen>potassium (S>P>Ca>Mg>N>K) and for micronutrients NERs were in the order of copper>boron>zinc>iron>manganese (Cu>B>Zn>Fe>Mn).     

Nitrate/ammonium ratio effects on nutrient solution pH,dry matter yield,and nitrogen uptake of sorghum 1

Abstract

Sorghum [Sorghum bicolor (L.) Moench] seedlings were grown in nutrient solutions in a growth chamber to investigate the effects of different ratios of NO₃ ^– and NH₄ ⁺ on nutrient solution pH, dry matter yield, and N uptake. Nutrient solutions and plant tissues were assayed throughout the time plants grew in the nutrient solutions.

Nutrient solution pH depended on source of N. The pH rose to near 8 with NO₃ ^– as the sole source of N and decreased to near or below 4 with NH₄ ⁺ added to the solutions. Upon depletion of NH₄ ⁺ from solution, pH values rose abruptly to near 8 and remained near this value throughout the duration of the experiments. Dry matter yield was generally higher for plants grown with some NH₄ ⁺ compared to plants grown with NO₃ ^– alone. Nitrogen uptake was generally higher in plants grown with the higher proportions of NH₄ ⁺. Nitrogen concentrations remained unchanged with plant age as NO₃ ^–/ NH₄ ⁺ ratio varied. For solutions low in NH₄ ⁺, N concentrations in roots increased with plant age. Severe Fe deficiency appeared in plants when solution pH reached and remained above 7.     

Effects of ammonium and inorganic carbon enrichment on growth and yield of a hydroponic tomato crop

Effects of varying the proportions of NO₃^— and NH₄⁺ in the growth medium on seedling growth and tomato fruit yield (Lycopersicon esculentum L. cv. Trust F1) were investigated in greenhouse hydroponic experiments. The presence of NH₄⁺ as the sole N source (11 mM) was toxic: it curtailed growth and decreased chlorophyll content of the leaves. However, at low concentration (10 % of total N), the presence of NH₄⁺, with or without added dissolved inorganic carbon (DIC), increased vegetative growth and fruit yield by ˜ 15 %, and enhanced taste/flavor of the fruits. In DIC‐enriched treatment, pH was maintained at 5.8 by addition of KHCO₃ or as CaCO₃. The presence of NH₄⁺, at 10 % of total N, inhibited NO₃^— uptake rates by ˜ 27 %. The rates of uptake of NO₃^— and NH₄⁺ were comparable (13.3 and 14.2 mmol plant^—1 d^—1, respectively, in the presence of DIC, and 14.7 and 14.0 mmol plant^—1 d^—1, respectively, in the absence of DIC), despite such a large difference in their concentrations in the nutrient feed solution. A higher proportion of NH₄⁺ (up to 50 % of total N) had no further significant effect upon early vegetative growth, but in a long‐term experiment resulted in a high incidence of blossom end‐rot (BER) disease, thereby severely curtailing fruit yield. The presence of even 1.1 mM NH₄⁺ reduced Ca²⁺ and Mg²⁺ accumulation in the leaves as well as in fruits.     

N form and concentration: Effects on reproductive development,growth and N content of southern peas 1

Southern peas [Vigna unguiculata, (L.) Walp.] cultured with 100% NH⁺ ₄ produced no viable flowers, while treatments in which NO^‐ ₃ composed 50% or more of the N form were not significantly different in the number of flowers formed. Flower abortion was least with 100% NO^‐ ₃ at the lower N concentration and with 75% and 100% NO^‐ ₃ at the higher N concentration. Further increments of NH⁺ ₄ resulted in greater flower abortion. The trends in flower survival were reflected in the number of pods and number of seed/plant. At the lower N concentration, the addition of NH⁺ ₄ slowed pod maturity, while at the higher N concentration pod maturity was hastened with the addition of up to 50% NH⁺ ₄. The dry weight and N content of tissues were generally greater with the higher N concentration and with N combinations containing predominantly NO^‐ ₃, but trends varied with the plant part being analyzed. Ammonium appears to adversely influence reproductive development and/or NO^‐ ₃ is essential to complete the reproductive development of southern peas. The observed differences in the response of southern peas to N form may account for previously reported discrepancies concerning the effectiveness of N fertilization on growth and yield parameters. Also, vegetative growth and vegetative N content appear to be poor indicators of final seed yields of southern peas if NH⁺ ₄ supplies a significant portion of the N form utilized by the plant.     

Effects of solution pH,temperature, nitrate/ammonium ratios,and inhibitors on ammonium and nitrate uptake by Arabica coffee in short‐term solution culture

Solution pH, temperature, nitrate (NO₃ ^‐)/yammonium (NH₄ ⁺) ratios, and inhibitors effects on the NO₃ ^‐ and NH₄ ⁺ uptake rates of coffee (Coffea arabica L.) roots were investigated in short‐term solution culture. At intermediate pH values (4.25 to 5.75) typical of coffee soils, NH₄ ⁺ and NO₃ ^‐ uptake rates were similar and nearly independent of pH. Nitrate uptake varied more with temperature than did ammonium. Nitrate uptake increased from 0.05 to 1.01 μmol g^‐1 FWh^‐1 between 4 and 16°C, and increased three‐fold between 16 to 22°C. Between 4 to 22°C, NH₄ ⁺ uptake rate increased more gradually from 1.00 to 3.25 μmol g^‐1 FW h^‐1. In the 22–40°C temperature range, NH₄ ⁺ and NO₃ ^‐ uptake rates were similar (averaging 3.65 and 3.56 umol g^‐1 FW h^‐1, respectively). At concentrations ranging from 0.5 to 3 mM, NO₃ ^‐ did not influence NH₄ ⁺ uptake rate. However, NO₃ ^‐ uptake was significantly reduced when NH₄ ⁺ was present at 3 mM concentration. Most importantly, total uptake (NO₃ ^‐+NH₄ ⁺) at any NO₃ ^‐/NH₄ ⁺ ratio was higher than that of plants fed solely with either NH₄ ⁺ or NO₄ ^‐. Anaerobic conditions reduced NO₃ ^‐ and NH₄ ⁺ uptake rate by 50 and 30%, respectively, whereas dinitrophenol almost completely inhibited both NH₄ ⁺ and NO₃ ^‐ uptake. These results suggest that Arabica coffee is well adapted to acidic soil conditions and can utilize the seasonally prevalent forms of inorganic N. These observations can help optimizing coffee N nutrition by recommending cultural practices maintaining roots in the temperature range optimum for both NH₄ ⁺ and NO₃ ^‐ uptake, and by advising N fertilization resulting in a balanced soil inorganic N availability.     

Effect of nitrate/ammonium ratio on biomass production,nitrogen accumulation,and use efficiency in sorghums of different origin

Plant nitrogen (N) uptake, growth, and N use efficiency may be affected by N form (NO₃ ^‐or NH₄ ⁺) available to the root. The objectives of this study were to determine the effect of mixed N form on dry matter production and partitioning, N uptake, and biomass N use efficiency defined as total dry matter produced per unit plant N (NUE₁) in U.S. and tropical grain sorghums [Sorghum bicolor (L.) Moench]. The U.S. derived genotype CK 60 and three tropical genotypes, Malisor‐7, M 35–1, and S 34, were evaluated in a greenhouse trial using three nutrient solutions differing in their NO₃ ^‐/NH₄ ⁺ ratio (100/0, 75/25, 50/50). Shoot and root biomass, N accumulation, and NUE, were determined at 10‐leaf and boot stages. Averaged over all genotypes, shoot and root biomass decreased when NH₄ ⁺ concentration was increased in the solution. Shoot biomass was reduced by 11% for 75/25 and 26% for 50/50 ratios, as compared to 100/0 NO₃ ^‐/NH₄ ⁺. Similarly, root biomass reduction was about 34% and 45% for the same ratios, respectively. Increasing NH₄ ⁺ concentration also altered biomass partitioning between shoot and root as indicated by decreasing root/shoot ratio. Total plant N content and NUE₁ were also reduced by mixed N source. Marked genotypic variability was found for tolerance to higher rates of NH₄ ⁺. The tropical line M 35–1 was well adapted to either NO₃ ^‐ as a sole source, or to an N source containing high amounts of NH₄ ⁺. Such a characteristic may exist in some exotic lines and may be used to improve genotypes which do not do well in excessively wet soil conditions where N uptake can be reduced.     

The response of pearl millet to changes in nitrogen concentration or form during grain fill

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a potentially productive, high‐yielding grain crop in the southeastern USA. A lack of response in pearl millet grain yield to fertilizer N in field studies indicates pearl millet may be able to remobilize N from vegetative to reproductive tissue. The N remobilization capabilities of a plant can be affected by the form of N supplemented. The objectives of this study were to evaluate the effects of N‐form ratio (NH₄ ⁺ : NO₃ ^‐) on the N remobilization capabilities of pearl millet when N is removed from the nutrient solution at the boot stage and to evaluate the effects of changing N‐form ratios at the boot stage on the seed yield and N content of pearl millet. Pearl millet was grown in solution culture under greenhouse conditions. There were 10 treatments: an initial NH₄ ⁺ : NO₃ ^‐ ratio of 3:1 followed by a change at the boot stage to either all NO₃ ^‐, no N, or a continuation of the initial ratio; an initial NH₄ ⁺ : NO₃ ^‐ ratio of 1:1 followed by a change at the boot stage to either all NO₃ ^‐, all NH₄ ⁺ no N, or a continuation of the initial ratio; and an initial NH₄ ⁺ : NO₃ ^‐ ratio of 1:3 followed by a change at the boot stage to either all NH₄ ⁺ no N, or a continuation of the initial ratio. Pearl millet dry matter accumulation was insensitive to changes in N‐form ratio or N removal at the boot stage. The lack of seed yield response to removal of N was a result of pearl millet utilizing N present in culms and leaves for seed production. Applications of N after the boot stage did not increase seed yield, but led to luxury consumption of N.     

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.     

Review of beneficial uses of calcium and ammonium salts for stimulating plant growth and metabolite translocation

Abstract

Numerous investigations have been conducted to quantify Ca‐stimulated ammonium (NH₄ ⁺) absorption by plants [this technology is covered under U.S. patent 4,500,335, patent licensee is Tetra Technologies, 250251–45 North, The Woodlands, TX 77380]. Greenhouse and field studies on vegetable crops, field crops and ornamental foliage crops show significant growth increases from increasing Ca⁺⁺:NH₄ ⁺ ratios in the growth media. Increased root growth was normally the first plant response, with especially large root and bulb responses observed in onion (Allium cepa L.), beets (Beta vulgaris.), radish (Raphanus sativus L.), and bermudagrass (Cynodon dactylon Pers.). Direct measurements of Ca‐stimulated NH₄ ⁺ absorption were obtained with isotopic nitrogen (¹⁵N) in greenhouse trials. As Ca⁺⁺ concentrations were increased an increase in ¹⁵NH₄ ⁺ absorption was obtained in all plant species tested. The Ca⁺⁺ stimulated NH₄ ⁺ absorption phenomenon in plants is best explained by the “Viets Effect”;, which describes the use of Ca⁺⁺ or magnesium (Mg⁺⁺) to increase plant absorption of potassium (K⁺). Although, increased NH₄ absorption effectively increases plant growth, increasing K⁺ absorption does not. Increased NH₄ ⁺ absorption has been associated with enhanced photosynthetic rates as well as increased proportions of new metabolites (compounds initially produced from newly captured carbon dioxide) translocated to the nutrient sinks (seeds, bulbs, roots, etc.). The integrity of the plasmalemma is maintained by the presence of extra Ca⁺⁺, leading to greater turgor pressure (higher water content) and nutrient retention in cells which produce greater growth potential in plants.     

Fertilizer ammonium : nitrate ratios determine phosphorus uptake by young maize plants

We investigated the interacting effects of inorganic nitrogen and the main inorganic phosphorus form in dairy manure (dicalcium phosphate, CaHPO₄) on growth, nutrient uptake, and rhizosphere pH of young maize plants. In a pot experiment, three levels of CaHPO₄ (0, 167, and 500 mg P pot^?1) were combined with nitrogen (637 mg N pot^?1) applied at five NH₄‐N : NO₃‐N ratios (0 : 100, 25 : 75, 50 : 50, 75 : 25, and 100 : 0) and a nitrification inhibitor in a concentrated layer of a typical acid sandy soil from Denmark. ¹⁵N‐labeled NH₄‐N was applied to differentiate the role of nitrification and to partition nitrogen uptake derived from NH₄‐N. Among treatments including nitrogen, shoot biomass, rooting and phosphorus uptake were significantly higher at the five‐leaf stage when CaHPO₄ was applied with NH₄‐N : NO₃‐N ratios of 50 : 50 and 75 : 25. In these treatments, rhizosphere pH dropped significantly in direct proportion with NH₄‐N uptake. The fertilizers in the concentrated layer had a root‐inhibiting effect in treatments without phosphorus supply and in treatments with pure NO₃‐N or NH₄‐N supply. Increased nitrogen uptake as NH₄‐N instead of NO₃‐N reduced rhizosphere pH and enhanced acquisition of applied CaHPO₄ by young maize plants, which may have positive implications for the enhanced utilization of manure phosphorus.     

Tomato growth and mineral composition as influenced by nitrogen form and light intensity

Abstract

Tomato plants were grown in sand culture with NH⁺ ₄, and NO^? ₃, forms of N and three levels of light. Plants supplied with NH⁺ ₄, nutrition under high light intensity had symptoms of stunting, leaf roll, wilting, interveinal chlorosis of the older leaves, and one third the dry weight of N0₃‐fed plants. In contrast, growth of plants receiving NH⁺ ₄, nutrition under shade appeared normal although dry weight was reduced. NH₄‐N nutrition suppressed K, Ca and Mg accumulation in tissues and increased P contents as compared to NO₃‐N nutrition.     

Influence of Nitrate:Ammonium Ratios on Growth and Elemental Concentration in Two Azalea Cultivars

Abstract

Rooted cuttings of Rhododendron canescens “Brook” and Rhododendron austrinum were grown in sand culture with a modified Hoagland's solution under greenhouse conditions. The effect of varying ammonium:nitrate (NO₃ ^?:NH₄ ⁺) ratios (100:0, 75:25, 50:50, 25:75, 0:100) on growth, chlorophyll content, plant quality, and elemental tissue concentration were determined. With NO₃ ^? as the nitrogen (N) form, both azalea cultivars exhibited less vegetative growth, lower overall plant quality, with leaves showing visual chlorotic symptoms in comparison to plants receiving NH₄ ⁺ as the N‐form. Leachate pH was highest with NO₃ ^? as the predominate N‐form and decreased significantly with each increment of NH₄ ⁺. With both azalea cultivars, N‐form significantly influenced uptake and utilization of essential plant nutrients. Leaf concentrations of N, potassium (K), calcium (Ca), sulfur (S), boron (B), and molybdenum (Mo) were highest with NO₃ ^?‐N. Leaf elemental concentrations of phosphorous (P), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) increased as NH₄ ⁺ supplied more of the N‐ratio. Significant differences in Mg, Mn, and Zn were observed between species. Results from this study show that foliar N concentration is not an accurate indicator of plant growth response. Further investigations are needed to determine if foliarchlorosis and low growth rates observed with NO₃ ^? fed plants due to an Fe deficiency, to low nitrate reductase (NR) activity in the leaves, or to a combination of these factors.