Reducing nitrogen leaching‐losses from containerized plants: The effectiveness of controlled‐release fertilizers

Abstract

To evaluate the effectiveness of controlled‐release fertilizer (CRF) for reducing nitrogen (N) leaching‐losses from containerized greenhouse crops, three experiments were conducted where CRFs were applied in different ways and compared to water‐soluble fertilizer (WSF). In each experiment, ‘First Lady’ marigold (Tagetes erecta L.) plants in 0.5‐liter pots of a soilless growth medium were fertilized with the same amount of ? from 20N‐4.3P‐16.6K WSF, Osmocote 14N‐6.2P‐11.6K CRF, or Nutricote 14N‐6.2P‐11.6K CRF fertilizers. The volume of irrigation water applied to all treatments was the same in each experiment. Nitrogen content, as NH₄‐N and NO₃‐N in container leachates, and plant growth were measured and used to compare WSF with CRFs incorporated in the growth medium, or as applied to the surface, in either one large application or two small doses. A single large application of CRF at planting resulted in as much or more ? leaching than the regular application of WSF. Effectiveness of CRFs in limiting ? leaching was greatly increased by making two smaller applications, the first at planting and the second 15 to 35 days later. More ? was recovered in the leachate when CRFs were incorporated in the growth medium compared to surface application. Regardless of fertilizer type, application method, timing of application, or for each individual experiment, NO₃‐N was the predominant ? form found in the leachate and more than one‐half of the total amount of ? leached during each experiment was recovered within 30 days of planting.     

Effects of plant age on nitrogen uptake and distribution by greenhouse plants

Water‐soluble nitrogen (N) fertilizer is intensively used in greenhouse crop production. Any N not used by a crop is subject to leaching as nitrate (NO₃‐N), which may pollute groundwater. A close correlation between N supply and N uptake by plants would increase the efficiency of N fertilization and minimize the possibility of NO₃‐N pollution. The objectives of this study were to measure N uptake by American marigold (Tagetes erecta L. ‘First Lady') and New Guinea Impatiens (NGI) (Impatiens hawkeri Bull. ‘Selenia') during growth, to determine the effect of plant age on N uptake, to determine if the two species have a preference for NO₃‐N or ammonium (NH₄‐N), and to determine the total N required for 70 days of growth.The plants were grown in solution culture using solutions supplying 120 mg each of NO₃‐N and NH₄‐N. At ten day intervals, six cultures were chosen at random for nutrient solution analysis and plant sampling for dry weight and tissue analysis. Nitrate‐N uptake was greater than NH₄‐N uptake throughout the experiment for both marigold and NGI. Total N uptake by marigold was greater during the first 50 days after transplanting with maximum N uptake during the period 30 to 50 days. In contrast, N uptake by NGI was greater during the period 40 to 70 days after transplanting. Maximum N uptake for NGI occurred during the period 60 to 70 days. Results of this study suggest that early N fertilization of marigold could be more important for their growth and quality than N applied later. For NGI, N fertilization later in the crop's development appears to be more important than early on. The total N absorbed by marigold during the experiment was 1.1 gm N plant^‐1; for NGI the quantity was 0.5 gm N plant‐¹.     

Mineral‐nutrient synergism and dilution responses to nitrogen fertilizer in field‐grown maize

Nitrogen (N)‐fertilizer applications to field‐grown maize may result in a dilution response whereby essential mineral‐element concentrations in shoots would decrease as shoot‐dry‐matter accumulation increased. To investigate this, the effect of N‐fertilizer treatments (no N or fertilizer rate based upon 5.3 or 8.5 t ha^–1 yield goal) on maize (Zea mays L.) shoot dry weight and shoot mineral concentrations (N, P, K, S, Mg, Ca, and Mn) at the sixth leaf (V6), twelfth leaf (V12), and tassel (VT) development stages were investigated in a 2‐year study conducted at Brookings, South Dakota (USA). With increasing N‐fertilizer application rates, shoot dry weight was greater and shoot P and K concentrations decreased. A possible explanation of this dilution response is that planting‐time P and K fertilizers, which were applied in a band near the seed furrow, may have enhanced the uptake of P and K in a manner that was independent of N‐fertilizer treatments. Increased shoot‐dry‐weight production due to the application of N fertilizers, if P and K uptake were similar across N‐fertilizer treatments, would lead to decreased shoot P and K concentrations in N‐sufficient compared with N‐deficient plants. Conversely, N‐fertilizer‐induced increases in shoot dry weight were accompanied by increased shoot concentrations of N, Ca, and Mn. This synergistic response between dry‐weight accumulation and shoot N concentration was present at all leaf developmental stages studied, while that for Ca was present only at VT. Thus, N fertilizer applications that increase shoot dry weight can affect the dilution and synergistic responses of specific mineral nutrients in maize shoots. Crop developmental stage as well as the location of these specific mineral nutrients in the soil profile might play important roles in mediating these responses.     

Growth and nutrient content of poinsettia (Euphorbia pulcherrima Willd. ex Klotz) in a soilless growth medium containing sewage sludge pellet fertilizer

The effectiveness sewage sludge pellet fertilizer (SPF) as a nutrient source for containerized poinsettia (Euphorbia pulcherrima Willd. ex Klotz) was determined by comparing the growth and nutrient element content of ‘Eckespoint Celebrate 2’ plants grown with SPF in the growth medium versus plants fertilized with conventional water‐soluble fertilizer (WSF). Plants were grown in 1.6‐L pots of soilless growth medium with SPF incorporated at planting at the rates of 1.0, 1.5, 2.0, 2.5, or 3.0 gm nitrogen (N) pot^‐1. Sludge pellet fertilizer plants received either no WSF or a dilute solution of 2ON‐4.3P‐16.6 potassium (K) (50 mg N L^‐1) twice a week. Control plants had no SPF and were fertilized with WSF at 250 mg N L^‐1 twice a week. At the end of the experiment plant growth measurements were made, leaves were analyzed for their nutrient element content, and growth medium was analyzed for pH and electrical conductivity (EC). Plants grown with SPF, with or without dilute WSF, were of commercially acceptable quality, but were somewhat smaller than the control plants. Plants growing with SPF alone and no WSF developed a chlorosis suggestive of N deficiency which was largely prevented by the application of WSF. Foliar analysis revealed that N in the leaves of plants receiving SPF alone was at the critical level for deficiency established for poinsettia. In treatments where dilute WSF was applied, the N content of the leaves was within the normal range. The foliar levels of all other nutrients fell within the normal ranges established for poinsettia in all SPF treatments. In addition to N deficiency, high growth medium EC at planting and low EC by the end of the experiment might also explain the inhibition of growth with SPF versus the WSF control. Results of this study suggest that poinsettia can be successfully grown using SPF as the sole source of nutrition, however the best growth is possible only when a dilute solution of N‐containing WSF is applied on a regular basis.     

Tillering,nutrient accumulation,and yield of winter wheat as influenced by nitrogen form 1

When grown with mixtures of nitrate‐nitrogen (NO₃‐N) and ammonium‐nitrogen (NH₄‐N) (mixed N) spring wheat (Triticum aestivum L.) plants develop higher order tillers and produce more grain than when grown with only NO₃. Because similar work is lacking for winter wheat, the objective of this study was to examine the effect of N form on tillering, nutrient acquisition, partitioning, and yield of winter wheat. Plants of three cultivars were grown to maturity hydroponically with nutrient solutions containing N as either all NO₃, all NH₄, or an equal mixture of both forms. At maturity, plants were harvested; separated into shoots, roots, and grain; and each part analyzed for dry matter and chemical composition. While the three cultivars varied in all parameters, mixed N plants always produced more tillers (by a range of 16 to 35%), accumulated more N (28 to 61%), phosphorus (P) (22 to 80%), and potassium (K) (11 to 89%) and produced more grain (33 to 60%) than those grown with either form alone. Although mixed N‐induced yield increases were mainly the result of an increase in grain bearing tillers, there was cultivar specific variation in individual yield components (i.e., tiller number, kernels per tiller, and kernel weight) which responded to N form. The presence of NH₄ (either alone or in the mixed N treatment), increased the concentration of reduced N in the shoots, roots, and grain of all cultivars. The effect of NH₄ in either treatment on the concentrations of P and K was variable and depended on the cultivar and plant part. In most cases, partitioning of dry matter, P, and K to the root decreased when NH₄ was present, while partitioning of N was relatively unaffected. Changes in partitioning between the shoot and grain were affected by N treatment, but varied according to cultivar. Based on these data, the changes in partitioning induced by NH₄ and the additional macronutrient accumulation with mixed N are at least partially responsible for mixed‐N‐induced increases in tillering and yield of winter wheat.     

Some aspects of salinity,plant density,and nutrient effects on Cressa cretica L.

The effects of salinity, density, and nutrient on the growth, reproduction, and ecophysiology of a perennial halophyte, Cressa cretica L., were studied. Lower salinity concentration (425 mM) promoted the growth, but the highest salinity (850 mM) did not have a significant effect. Plants grew faster and were healthier at low density treatment. Lack of nitrogen (N) in the medium substantially inhibited shoot growth. Higher rhizome length and increased dry weight were some of the symptoms of N‐deficiency. Phosphorus (P)‐free plants also showed higher dry weight and higher ratio of rhizomes to shoots. Reproductive capacity of Cressa cretica plants was not affected by the absence of P. Growth and reproduction of Cressa cretica plants were significantly inhibited by potassium (K) deficiency. Optimal plant growth was recorded in complete nutrient solution. Higher concentrations of oxalate were found in plants growing under low density conditions and in non‐saline controls. Proline concentration increased with the increase in salinity of the medium. Chlorophyll a and b synthesis were inhibited by high salinity treatments whereas changes in density regimes did not have an effect.     

Phosphorus efficiency of ornamental plants in peat substrates

A pot experiment was conducted to investigate factors contributing to phosphorous (P) efficiency of ornamental plants. Marigold (Tagetes patula) and poinsettia (Euphorbia pulcherima) were cultivated in a peat substrate (black peat 80% + mineral component 20% on a volume basis), treated with P rates of 0, 10, 35, 100, and 170 mg (L substrate)^–1. During the cultivation period, plants were fertigated with a complete nutrient solution (including 18 mg P L^–1) every 2 d. Both poinsettia and marigold attained their optimum yield at the rate of 35 mg P (L substrate)^–1 and the critical level of P in shoot dry matter of both crops was 5–6 mg g^–1. After planting, plant‐available P increased at lower P rates to a higher level for poinsettia than for marigold, but no significant change was observed at higher P rates. Balance sheet calculations indicated that at lower P rates more P was fertigated than was taken up by the plants. Root‐length density, root‐to‐shoot ratio, and root‐hair length of marigold were doubled compared to that of poinsettia. Root‐length density increased with crop growth, and 10 d after planting the mean half distance between roots exceeded the P‐depletion zone around roots by a factor of 3 and 1.5 for poinsettia and marigold, respectively. Thus, at this early stage poinsettia exploited only 10% of the substrate volume whereas marigold utilized 43%. Later in the cultivation period, the depletion zones around roots overlapped for both crops. Taking into account P uptake via root hairs, the simulation revealed that this was more important for marigold compared to poinsettia especially at low P‐supply levels. However, increase of P uptake due to root hairs was only 10%–20% at optimum P supply. For the two lower P levels, the P‐depletion profile around roots calculated for 10 d after planting showed that after 2 d of depletion the concentration at the root surface was below the assumed K_m value (5 μM) and the concentration gradient was insufficient to fit the demand. A higher content of plant‐available P in the substrate was observed for poinsettia compared to marigold in the treatment with P application adequate for optimum growth, because more fertigated P was accumulated during early stages of cultivation due to lower root‐length density of poinsettia. The observed difference of root morphological parameters did not contribute significantly to P‐uptake efficiency, since P mobility in the peat substrate was high.     

EFFECT OF COTTONSEED MEAL WITH OR WITHOUT SOAPSTOCK,CANOLA MEAL,OR UREA ON SOIL FERTILITY AND GROWTH OF MARIGOLD AND REDBUD

The effects of incorporating or topdressing with cottonseed (Gossypium hirsutum L.) meal with or without soapstock, canola (Brassica rapa L.) meal, urea, or no amendment (control) were investigated using plants of marigold (Tagetes erecta L. ‘Inca II Gold’ or ‘Inca II Yellow’) and redbud (Cercis canadensis L.) in a Norge loam (fine-silty, mixed, thermic Udic Paleustolls) at Stillwater, OK in 2008 and 2009. Fertilizers were applied in May at 4.9 g?m^?2 N based on soil test results prior to the study and nitrogen (N) recommendations for turfgrass. Soil nitrate-nitrogen (NO₃-N) and phosphorus (P) increased from 2008 to 2009 in marigold plots into which cottonseed meal with soapstock was incorporated, and boron (B) increased in all marigold plots regardless of treatment. In 2009, marigolds grown in plots into which cottonseed meal was incorporated were taller than plants in other treatments except the untreated control. Marigolds in plots in which cottonseed meal was topdressed, cottonseed meal with soapstock was incorporated, or urea was topdressed grew less in height than plants in plots with cottonseed meal incorporated or control plots. Shoot dry weights of marigold plants in plots topdressed with cottonseed meal with or without soapstock, urea, or control plots were lower than those of plants in other treatments. Visual ratings of marigold plants receiving a topdress of urea or no treatment were lower than visual ratings of plants in any other treatment in July, but similar in August to those of marigold plants in plots in which cottonseed meal was topdressed. Some differences within fertilizer treatments occurred between 2008 and 2009 in redbud soil concentration of NO₃-N, calcium (Ca), magnesium (Mg), sulfate-sulfur (SO₄-S), iron (Fe), B, and copper (Cu). Leaf P concentration differed among fertilizer treatments in 2009. Leaf and total dry weight of redbuds grown in soil incorporated with urea was greater than that of plants in any other treatment. Results indicate that cottonseed and canola meals provide N and other nutrients for growth of landscape plants. Soil incorporated cottonseed meal encouraged more growth of marigold than soil incorporated urea but less growth of redbud.     

Using Commercially Available Ion‐Exchange Membranes to Monitor Plant‐Available Nutrients in Cranberry

Abstract

Monitoring in‐season nutrient availability in cranberry (Vaccinium macrocarpon Ait.) is hampered by tissue sampling being limited to a short, late‐summer period, and a low‐pH, high‐iron (Fe) soil environment limits soil‐test result interpretation. To evaluate monitoring available in‐season nitrogen (N), phosphorus (P), and potassium (K), commercially available ion‐exchange membranes (PRS?) were placed in plots where standard fertilizer practices were supplemented with the controlled‐release fertilizer (CRF) Osmocote? 14–14–14 at 0, 112, 224 or 336 kg/ha rates. PRS? nitrate (NO₃)‐N was related only to CRF fertilizer, whereas PRS? ammonium (NH₄)‐N reflected both the CRF and in‐season fertilizer applications. Large increases in PRS? NH₄‐N with increasing CRF rates suggested a synergistic effect of CRF on fertilizer NH₄‐N availability. PRS? P was positively correlated with CRF P but negatively to in‐season P applications, whereas PRS? K was related to in‐season fertilizer applications but not to CRF, suggesting poor plant P availability in the soil environment and relatively little K contribution from CRF, respectively. These results show promise for using PRS? in cranberry.     

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.     

Yield and nitrogen use efficiency of wheat increased with root length and biomass due to nitrogen,phosphorus, and potassium interactions

Balanced applications of nitrogen (N), phosphorus (P), and potassium (K) are known to increase grain yield of wheat but the impact of the interactions among N, P, and K on root growth and nitrogen use efficiency (NUE) have not been proven. The aim of this study was to investigate the effect of balanced applications of N, P, and K on the rooting patterns and NUE of wheat. Two glasshouse experiments were conducted. A rhizobox study was used to assess the impact of interactions among N, P, and K fertilisers on total root length, biomass, specific root length, root length density, N use efficiency (NUE), and N uptake efficiency of the shoots (NUpE_shoot) and N nutrition index. In a separate pot study, plants were grown to maturity to confirm the effect of the observed changes in root growth on NUE, NUpE_grain, and grain/biomass yield. In the rhizobox experiment when plants were supplied with N+P+K, total root biomass increased approximately six‐fold relative to plants grown with N alone or with no fertiliser. Plants exposed to N+P+K had NUpE_shoot and NUE values that were five and ten times higher, respectively, than plants that received just fertiliser N. Plants supplied with N+P or N+P+K had N nutrition indices close to one (N‐adequate), while plants that only received N had an index of 0.62 (N‐deficient). The pot study confirmed that the changes in root length and biomass in plants exposed to N+P+K resulted in significant increases in NUE, NUpE_grain, shoot biomass, and grain yield at maturity. Interactions among fertiliser N, P, and K played a critical role in influencing root biomass and length, which was associated with increases in NUE, NUpE_shoot and NUpE_grain.     

Effects of Plant Growth-Promoting Rhizobacteria and N Source on Plant Growth and N and P Uptake by Tomato Grown on Calcareous Soils

Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency. Two pot experiments were conducted in the greenhouse from December 3, 2012 to January 25, 2013 (Experiment 1) and March 11 to April 23, 2013 (Experiment 2) to evaluate the effect of nitrogen (N) source and inoculation with plant growth-promoting rhizobacteria (PGPR) on plant growth and N and phosphorus (P) uptake in tomato (Lycopersicon esculentum Mill.) grown on calcareous soils from South Florida, USA. Treatments included urea, controlled release urea (a controlled release fertilizer, CRF) each at low and high N rates and with or without inoculation of PGPR. A mixture of PGPR strains Bacillus amyloliquefaciens IN937a and Bacillus pumilus T4 was applied to the soil during growing periods of tomato. Treatments with PGPR inoculation increased plant height compared to treatments without PGPR in both experiments. Inoculation with PGPR increased shoot dry weight and shoot N uptake for the same N rate and N source. In both experiments, only at high N rate, CRF and urea treatments with PGPR had significantly (P < 0.05) greater shoot biomass than those without PGPR. Only at high N rate, CRF treatment with PGPR significantly increased shoot N uptake by 39.0% and 10.3% compared to that without PGPR in Experiments 1 and 2, respectively. Meanwhile, presence of PGPR in the soil increased shoot P uptake for all treatments in Experiment 1 and for most treatments in Experiment 2. In Experiment 1, only at low N rate, CRF treatment with PGPR significantly increased shoot P uptake compared with that without PGPR. In Experiment 2, a significant increase in shoot P uptake by inoculation of PGPR was only observed in CRF treatment at high N rate. Results from this study indicate that inoculation with PGPR may increase plant growth and N and P uptake by tomato grown on calcareous soils. However, the effect of PGPR varied and was influenced by many factors such as N source, N rate, and soil fertility. Further investigations are warranted to confirm the effect of PGPR under different soil conditions.     

Effects of solid phase from pig slurry on soil chemical characteristics,nitrate leaching,composition, and yield of wheat

A two years lysimeter experiment was carried out using wheat plants (Triticum aestivum L. cv. Lotti) on two texturally contrasting soils. The main purpose of this study was to evaluate the influence of increasing applications (5,10, 15,20, and 25 t.ha^‐1) of solid phase (SP) from pig slurry on soil nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sodium (Na) content, nitrate‐N (NO₃‐N) leaching as well as on wheat composition and yield. As the control, a basic dressing of NPK fertilizer was applied. Results showed that plant growth was stimulated by increasing amounts of SP, yet the additions of 15 to 20 t SP ha^‐1 led to similar effects on yield as that for the control. An accumulation of P on both soils was observed as well as a significant increase on NO₃‐N leaching due to increasing rates of SP added to the soils. The N and P content in wheat plants (straw and grain) increased with increasing rates of applied SP.     

Growth and macronutrient contents of faba bean plants: Effects of salinity and nitrate nutrition

The effects of the interaction between sodium chloride, nitrate, and concentrations on growth and internal ion content of faba bean (Vicia faba L.) plants were studied, to understand the relationship between the above parameters and salt tolerance. Increased salinity substantially reduced the dry weight of roots and shoots and increased the root/shoot biomass ratio. Additional nitrate‐N considerably moderated the salinity effects on these parameters. The promotive effects of nitrate‐N were more pronounced on shoot dry weight. These results suggest that an exogenous supply of nitrate‐N would improve the vegetative growth of V. faba plants by moderating the suppresive effects of salinity. The evolution of the root and shoot content in potassium (K), sodium (Na), magnesium (Mg), calcium (Ca), and nitrogen (N) was monitored during vegetative growth. A high correspondence between total N and Ca content was found. The acquisition of Ca and K in response to salt and nitrate was similar in shoots and roots, whereas Mg uptake showed notable differences in the two organs. In salt‐affected plants, the roots were found to be high in accumulated Na while the shoots exhibited the lowest Na concentration. Potassium accumulation was higher in the shoots. In this way, there was an antagonistic effect between Na and K uptake. Analyses of the nutrient contents in plant organs have provided a data base on salt‐tolerance mechanisms of V. faba plants.     

Overcoming Fe deficiency in guava (Psidium guajava L.) by co-situs application of controlled release fertilizers

Abstract

Among micronutrient deficiencies, Fe deficiency is the most difficult nutritional disorder to prevent in the fruits of trees growing on calcareous soils. In this study, a pot experiment was carried out to evaluate the potential of co-situs application of controlled release fertilizers (CRF) in alleviating Fe deficiency and improving the growth of fruit trees growing on calcareous soil (pH 9.3). Guava (Psidium guajava L.) seedlings were used as test plants because of their sensitivity to Fe deficiency. Treatments consisted of the following: (1) broadcast application of readily soluble Fe, Zn, Cu, B and Mn fertilizers (Control) or (2) co-situs application of CRF containing N, P, K, Mg, Fe, Zn, B, Cu and Mn (Co-situs). For the Control treatment, CRF containing only N, P and K was used. Both treatments received the same amount of all nutrients. Plants were more chlorotic in young leaves under the Control treatment and the Fe content of young leaves was significantly (least significant difference [LSD_0.05]) higher under the Co-situs treatment. Dry matter production of shoots under the Co-situs treatment was 5.2-fold higher than under the Control treatment, and the total accumulations of macro and micronutrients were much higher under the Co-situs treatment than the Control treatment. Total accumulations of N, P, K, Ca and Mg were 5.0, 4.1, 9.6, 3.2 and 2.2-fold higher, respectively, under the Co-situs treatment compared with the Control treatment, and Fe, Zn, Cu and Mn accumulations were 3.2, 4.1, 6.0 and 3.7-fold higher, respectively. Iron deficiency in guava seedlings was successfully alleviated by the co-situs application of controlled fertilizer, proving the high potential of this method in alleviating Fe deficiency in fruit trees growing on calcareous soils.     

Evaluation of Controlled-Release Fertilizers for Northeast Florida Chip Potato Production

ABSTRACT

Controlled-release fertilizers (CRF) were compared with ammonium nitrate (AN) in a potato (Solanum tuberosum L.) production study at the University of Florida farm in Hastings, FL, in 2002. Treatments were no nitrogen (No-N), AN, and nine CRFs at 146 kg ha^?1 N and 225 kg ha^?1 N. CRF7 (146 kg ha^?1 N) resulted in highest total and marketable yields at 33.7 MT ha^?1 and 29.4 MT ha^?1, respectively. Tubers from the AN (225 kg ha^?1 N) and CRF9 (225 kg ha^?1 N) treatments had the highest specific gravity at 1.073. Nitrogen removal efficiency was highest in plants in CRF1 (43.0%) and CRF7 (47.3%) plots. Both were significantly higher than AN-treated plants. At 39 days after planting, NO₃-N and NH₄-N concentrations in lysimeter water samples were significantly higher in AN treatments. Leaf tissue N concentrations were sufficient throughout the growing season in all treatments except No-N.     

Influence of phosphorus on nitrogen fixation in chickpea cultivars

Phosphorus (P) is a major nutrient factor influencing nitrogen (N) accumulation and partitioning of photosynthates in plants, especially the symbiotic N₂‐fixation in legumes. This study was conducted to investigate how P application (0, 20, 40, and 60 kg P₂O₅/ha) affects symbiotic N₂‐fixation of three cultivars (C 235, Pusa 408, and Pusa 417) of chickpea (Cicer arietinum L.). Application of P in general significantly increased leaf area, shoot dry weight, and the rate of acetylene (C₂H₂) reduction. Phosphorus concentration of shoots and roots, soluble sugar content of nodules, and shoot N accumulation were also significantly increased, especially by P at the 40 kg P₂O₅/ha rate. The P concentration in nodules was, however, not affected by different levels of P. The Pusa 417 cultivar responded better than the others to the P treatments. Phosphorus‐deficient plants accumulated sugar in their leaves. The interaction effect was found significant on leaf area, shoot dry weight, nodule number, and shoot N accumulation. Pusa 417 gave greatest response to 40 kg P₂O₅/ha but Pusa 408 and C 235 interacted best with the 20 kg P₂O₅/ha rate only. The increased nodulation and symbiotic N₂‐fixation on P application seem to be the result of morphologically advanced shoots which are making more photosynthates for transport to nodules and not the direct effect of P on the nodules.     

Determination of a critical dilution curve for nitrogen concentration in cotton

Several nitrogen (N)‐rate field experiments were carried out in cotton to define dilution curves for critical N concentrations in individual plants (i.e., the minimum N concentration required for maximum growth at any growth stage). Nitrogen application rate had a significant effect on aboveground dry matter, N accumulation, and N concentration. As expected, shoot N concentration in plants decreased during the growing period. These results support the concept of critical N concentration in shoot biomass of single plants as described by Lemaire et al. (2007) and reveal that a dilution curve for critical N concentrations in cotton plants can be described by a power equation. The pattern of critical–N concentration dilution curves was consistent across the two sites. Nitrogen concentration for a given biomass varied greatly with the supply of N. After initial flowering, the N‐nutrition index (NNI) for aboveground biomass of individual plants increased with increasing N rates. Relationships between plant total N uptake and accumulated dry matter in the aboveground biomass can be described by the allometric‐relation equations for each dose of N. Nitrogen‐dilution curves can be used as a tool for diagnosing the status of N in cotton from initial flowering to boll opening. The relationship can also be used in the parameterization and validation of growth models for predicting the N response and/or N requirement of cotton.     

Potassium and nitrogen effects on carbohydrate and protein metabolism in alfalfa roots

An investigation was conducted to determine the effect of potassium (K) nutrition on alfalfa (Medicago sativa L.) growth and metabolism of root total nonstructural carbohydrates (TNC) and proteins, and to study whether nitrogen (N) fertilization overcomes N deficiency and low root protein concentrations caused by K deficiency. In Experiment 1, nodulated alfalfa plants were grown in plastic pots containing washed quartz sand and provided minus‐N Hoagland's solution containing 0, 0.6, or 6.0 mM K. Shoot and root K concentrations increased with increasing solution K. Root N concentrations were higher in plants receiving 6.0 mM K than in plants receiving 0.6 or 0 mM K, but shoot N concentrations were similar for all treatments. Plant persistence, shoots per plant, and shoot mass increased as solution K levels increased. Root starch concentration and utilization were positively associated with K nutrition. Total amylase activity was higher, but endoamylase activity was lower in roots of plants receiving 6.0 mM K compared to plants receiving 0.6 or 0 mM K. Root soluble protein concentrations were significantly higher in plants receiving 6.0 mM K than in plants receiving 0 or 0.6 mM K. In Experiment 2, plants were supplied with Hoagland's solution containing 10 mM N as ammonium (NH₄ ⁺) or nitrate (NO₃) with 0,3, or 6.0 mM K. The addition of N increased root N concentrations only in plants receiving 0 mM K. Plant persistence was reduced by NH₄ ⁺ application, especially in plants receiving 0 or 3 mM K. Root starch concentrations were markedly reduced in plants receiving NH₄ ⁺ at all K levels. The addition of NO₃ ^‐ had little effect on alfalfa root carbohydrate and protein metabolism and subsequent shoot growth. Potassium deficiency reduced starch and protein concentrations in roots; factors that were associated with poor persistence and slow shoot regrowth of alfalfa.     

Slow release versus water soluble fertilization affects nutrient leaching and growth of potted chrysanthemum

In two experiments, ‘Charm’ and ‘Delano’ chrysanthemum [Dendranthema x grandiflorum (Ramat.) Kitamura] were grown in a peat‐based root medium using standard greenhouse cultural practices. Fertilization treatments included (1) alternate liquid fertilization (ALF): water‐soluble formulation of 15N‐4.3P‐24.9K (15–10–30) at 536 mgL^‐1 N alternated with tap water irrigation; (2) Constant Liquid Fertilization (CLF): 15N‐4.3P‐24.9K(15–10–30)at268 mgL^‐1 Napplied at each irrigation; (3) slow release resin‐coated fertilizer (SRR): slow release formulation of 12N‐4.3P‐14.1K(12–10–17); and (4) slow release tablets (SRT): slow release formulation of 14N‐1.7P‐4.9K (14–4–6). Irrigation volume and timing of application were arbitrary for all plants in the first experiment, but they were determined gravimetrically for each treatment in the second experiment. Irrigation volumes exceeded container capacity by 20 to 30% (leaching fractions of 0.2 to 0.3). Leachate had lower electrical conductivity and higher pH with the slow release products than with liquid fertilizer. All treatments except SRT produced plants which met commercial crop standards and had adequate nutrient levels in shoot tissue. However, root dry mass was higher with slow release fertilizer than with liquid fertilizer. Rootrshoot ratios were ranked SRT>SRR>ALF=CLF. Root data suggest that an advantage of SR fertilization over LF fertilization is that greater root mass will develop. Estimations of nitrogen (N) recovery in Experiment 2 suggest that chrysanthemums grown with SRR resulted in most efficient uptake of fertilizer with 64 to 68% of applied N recovered in plant tissue (compared to 41 to 46% from LF treatments) and 18 to 21 % recovered in container leachate (compared to 32 to 41% from LF treatments).