Form Of Fertilizer Research Articles

Seasonal soil and foliage nutrient dynamics of a juvenile loblolly pine plantation: Impacts of fertilizer formulation and vegetation suppression

Understanding soil and foliage nutrient dynamics can enhance effectiveness and sustainability of forest nutrition improvement practices. Monthly soil and foliage nutrient concentrations were measured in a juvenile loblolly pine ( Pinus taeda L.) plantation in southeastern Oklahoma, USA, in response to: untreated control, herbaceous vegetation suppression (VS), urea and diammonium phosphate (DAP), urea and DAP with VS, and coated urea fertilizer (CUF) with VS. Fertilization treatments persistently increased soil NO 3 − and foliage N concentrations. All fertilization treatments also reduced foliage P:N and K:N ratios below optimum levels, suggesting that the fertilizer treatments used in this study (which are conventionally applied to mid-rotation loblolly pine plantations of the region) did not adequately match the nutrient demands of this juvenile plantation. Herbaceous vegetation suppression prolonged soil and foliage N increases, prolonged declines in P:N ratios, and increased foliage B and P concentrations in the second year of the study. Fertilizer formulations yielded similar foliage and soil N and P concentrations.

Effect of selenium fertiliser formulation and rate of application on selenium concentrations in irrigated and dryland wheat (Triticum aestivum)

Field trials were carried out on two wheat (Triticum aestivum) crops (one irrigated, one dryland) in Canterbury, New Zealand during the 2005–06 growing season to evaluate the effectiveness of two selenium (Se) fertilisers in raising grain Se levels. Both contained sodium selenate: “AgSel” is a fast release formulation (100% water‐soluble Se) whereas “Selprill Double” (76% water‐soluble Se) has been formulated to slow the release of Se. The fertilisers were broadcast in spring (Zadoks growth stage 32) at rates of 5 to 20 g Se/ ha. Grain Se increased linearly with application rate, but concentrations were higher with the fully‐soluble formulation. Mean Se concentration was significantly lower in irrigated (grain yield 9.1 t/ha) than dryland (yield 7.4 t/ha) wheat (0.17 versus 0.25 mg Se/kg), possibly owing to yield dilution. For the fully‐soluble Se fertiliser, grain Se increased by 0.018 mg/kg in irrigated wheat for each g/ha of applied Se. an application of 4–5 g/ha would raise grain Se to 0.1 mg/kg (approximate concentration in imported australian wheat), assuming natural levels in Canterbury wheat are c. 0.02 mg/kg. The water‐insoluble component of Selprill Double made little or no contribution to Se uptake when the fertiliser was applied in spring and therefore application rates should be c. 30% higher than those of the fully‐soluble fertiliser.

Evaluation of Slow-release Fertilizers on Bell Pepper

This study was conducted to compare different formulations of a slow-release fertilizer with a conventional fertilizer program to determine their impact on yield and growth of bell pepper (Capsicum annuum). Two formulations of a methylene-urea slow-release fertilizer (Nitamin®) were evaluated on drip-fertigated and plastic-mulched bell peppers during 2006 in the eastern coastal plain and western Appalachian mountains of North Carolina. Liquid slow-release formulations were applied the first 6 or 9 weeks of the growing season and a dry formulation was banded at planting. Treatments were compared with the extension-recommended rate of 200 lb/acre nitrogen (N) (NC-200) and a high-input fertilizer rate of 300 lb/acre N (HI-300) from calcium nitrate injected in 12 weekly applications of drip irrigation. Irrigation was applied twice per week. The slow-release granular formulation at 200 lb/acre N produced the highest marketable yield and better canopy quality in eastern soil. Early marketable yield for this treatment accounted for 46% of the total yield. All slow-release treatments had higher N use efficiency (NUE) values than NC-200 and HI-300 in the eastern study. In loam soil (western study), pepper yield was statistically similar among treatments. Lower rates (150 lb/acre N) of slow-release fertilizer performed as well as NC-200 and HI-300 for marketable yield. Low rates (150 lb/acre N) of one of the liquid formulations performed better in total and marketable NUE than NC-200 and HI-300 in Fletcher, North Carolina. Liquid and dry formulations of slow-release fertilizer showed a potential to be used on bell pepper production across the state at reduced N rates, with greater impact on yield in coarse-textured soils found predominantly in the eastern coastal plain region.

Soil nitrogen dynamics in irrigated maize systems as impacted on by nitrogen and stubble management

The soil nitrogen (N) dynamics of an irrigated maize system in which stubble retention and stubble burned treatments were superimposed over treatments of varying N fertiliser rate were studied. The field site was near Whitton, New South Wales, Australia, and the work described here is part a life cycle analysis of greenhouse gas emissions from maize project. The objective of this part of the work was to quantify the fate of fertiliser N applied at the site. Field measurements of denitrification, mineral N content and recovery of 15N-labelled urea from microplots with and without ammonium thiosulfate were complimented with laboratory studies of denitrification and nitrous oxide (N2O) flux. Significantly (P < 0.05) more fertiliser N was recovered in the grain from the stubble incorporated treatment than the stubble burned treatment and there was greater recovery of fertiliser N in the soil at the end of the experiment in the stubble burned treatment. This may indicate that fertiliser N applied to the stubble burned system may be more exposed to soil-N transformations. The reason for the difference in uptake and soil residual is not clear but may be related to soil structure differences leading to less plant accessibility of N in the burned treatment. This difference may lead to more nitrous oxide emission from soil in the stubble burned treatments. Short-term (1 h) static chamber measurements in the field found a strong N-rate dependence of N2O emission rate for fertiliser rates between 0 and 300 kg N/ha. Inclusion of ammonium thiosulfate in the fertiliser formulation did not appear to have a significant impact on fertiliser N recovery.

A novel challenge test incorporating irradiation (60Co) of compost sub-samples to validate thermal lethality towards pathogenic bacteria

Maturing compost heaps normally attaining temperatures ranging from 55 to 65°C is generally regarded to conform to recommended biological risks and sanitation standards for composts stipulated by either EU or US-EPA. Composted products derived from animal sources are further required by EU biohazard safety regulatory legislation that such composts either attain 70°C for over 3h during maturation or via treatment at 70°C for 1h before being considered for dispensation on land. The setting of the upper limit of thermal lethality at 70°C/1h for achieving biosecurity of the animal waste composted products (e.g. pelleted fertilizer formulations) is not properly substantiated by specific validation tests, comprising a ‘wipe-out’ step (usually via autoclaving) followed by inoculation of a prescribed bacterium, exposure to 70°C/1h and the lethality determined. Pelleted formulations of composts are not amenable for wet methods (autoclaving) for wipe-out sterilization step as this is detrimental to the pellet and compromises sample integrity. This study describes a laboratory method involving the employment of (60Co) irradiation ‘wipe-out’ step to: (a) compost sub-samples drawn from compost formulation heaps and (b) pelleted products derived from composted animal products while determining the thermal lethality of a given time/temperature (70°C/1h) treatment process and by challenging the irradiated sample (not just with one bacterium but), out with 10 potential food-poisoning organisms from the bacterial genera (Campylobacter, Escherichia, Listeria, Salmonella, Yersinia) frequently detected in pig and poultry farm wastes. This challenge test on compost sub-samples can be a useful intervention ploy for ‘inspection and validation’ technique for composters during the compost maturity process, whose attainment of temperatures of 55–65°C is presumed sufficient for attainment of sanitation. Stringent measures are further required by law for composted products arising from rural industrialists producing pelleted fertilizers from re-composted animal agriculture wastes comprising pig slurry solids, poultry litter and spent mushroom compost, which carry residual food-borne pathogens with implications to the food chain including humans. Environmentally, sustainable means of recycling farm wastes require that final composted products are free of pathogens in compliance with environmental safety legislation before their release to the market. This test developed provides a science-based risk characterization tool for sustainably managing environmental safety by ‘validating’ thermal lethality of a given composting process or their derivatives achieved without compromising the sample integrity or ambiguity attached to microbiological validation involving steam sterilization or autoclaving procedures and helps audit the resurgent bacterial populations from surviving non-pathogenic organisms in the end-products of animal waste compost formulations.

Screening for rock phosphate solubilizing Actinomycetes from Moroccan phosphate mines

Three Moroccan phosphate mines, an original biotope rich in insoluble rock phosphate (RP), were explored for the presence of RP solubilizing Actinobacteria. Three hundred actinomycete isolates originating from these mines were tested for their ability to grow on a synthetic minimum medium (SMM) containing insoluble RP as unique phosphate source. Only 55 isolates (18.3%) were able to weather RP in SMM medium. Eight isolates showed the most active growth and solubilization capability. These isolates were shown to be able to solubilize RP in liquid cultures. The study of mechanisms involved in these weathering processes indicated that the isolates produce siderophores but not organic acids. Seven of these strains were shown to belong to the genus Streptomyces and one, to the genus Micromonospora. This study is expected to lead to the formulation of novel bio-phosphate fertilizers constituted by the association of pulverized RP and spores of the ad hoc actinomycete strains.

The Effect of Formulation and Amount of Potassium Fertilizer on Macromineral Concentration and Cation-Anion Difference in Tall Fescue

This study investigated the feasibility of altering the dietary cation-anion difference (DCAD) in grass by altering the grass variety and the amount and formulation of K fertilizer application. In experiment 1, treatments were combinations of 2 varieties (Barcel and Hi-Mag) of tall fescue (Festuca arundinacea Schreb); 2 rates of K (0 and 250kg/ha), supplied as KCl; and 2 rates of Mg (0 and 60kg/ha), supplied as MgO. In experiment 2, K fertilizer was applied at 0 or 125kg/ha as KCl or K2SO4. There was no difference between HiMag and Barcel tall fescue in the concentrations of Mg, S, and Cl. Application of K fertilizer decreased concentrations of Mg, but the magnitude of the decrease was not consistent across harvests. Conversely, application of Mg fertilizer increased Mg concentrations, but again, the magnitude of the increase was not consistent across harvests. The concentrations of Ca were higher in HiMag than in Barcel tall fescue, with the magnitude of the difference increasing from first to last harvest. Potassium fertilizer decreased Ca concentrations in the first, fourth, and fifth harvests only. Calcium concentration was decreased by a greater magnitude in HiMag tall fescue as a result of Mg fertilization. The HiMag tall fescue contained lower concentrations of K than did Barcel tall fescue in the first, second, and third harvests. Application of K fertilizer increased the K concentration in all 5 harvests but did not affect Na concentrations except in the last harvest. The HiMag tall fescue contained less Na than did Barcel, but the magnitude of the difference was affected by K and Mg fertilization. Application of K fertilizer decreased S concentrations in first-harvest grass, increased concentrations in second-and third-harvest grasses, and had no effect in fourth-or fifth-harvest grasses. Application of Mg fertilizer decreased S concentrations of tall fescue. Application of K fertilizer increased DCAD values for grass harvested from the second through fifth harvests. The increase in DCAD attributable to K fertilizer was less in HiMag than in Barcel tall fescue. Application of K fertilizer as K2SO4 increased dry matter yield and S concentrations of HiMag tall fescue, whereas K applied as KCl increased concentrations of K and Cl. There was no effect of fertilizer formulation on Na concentrations. The DCAD was lower in HiMag tall fescue fertilized with K2SO4 compared with that fertilized with KCl. This study showed that DCAD of grass can be manipulated by the choice of grass variety, fertilizer formulation, and fertilizer application rate.

Comparison of slow‐release nitrogen yield from organic soil amendments and chemical fertilizers and implications for regeneration of disturbed sites

AbstractSoil amendments are commonly used to regenerate nutrient levels on disturbed construction sites or mined lands prior to revegetation. Management of nitrogen (N) inputs to the degraded substrates is difficult because the low level of ambient fertility on disturbed substrates requires large total N inputs to sustain revegetative growth, but it also requires low N bioavailability in order to avoid weedy invasion and eutrophication of local watersheds. Commonly available soil amendment materials have a wide variety of N contents and release rates, making specification of appropriate N amendments difficult. We compared N release rates of a variety of organic‐based soil amendments and chemical fertilizers in long‐term aerobic incubation chambers in the lab and at a field revegetation site. The N release rate from these amendments fell into four general groups: (1) rapid N release from soluble chemical fertilizer formulations, (2) longer, controlled N release from chemical‐based, slow‐release formulations, and a two‐phase release pattern (rapid initial phase, slower second phase) from (3) organic‐based blends, as well as (4) unsupplemented municipal yard‐waste composts. The release rates from organic‐based amendments were about three times faster in the 30°C laboratory incubations than in the cool, moist winter growing season at a field site in the Central Valley of California. Relative rates of N release can be compared between amendment materials to help guide selection of N amendments, according to the plant‐growth goals of the revegetation project. Copyright © 2006 John Wiley & Sons, Ltd.

Matrix Based Fertilizers Reduce Nitrogen and Phosphorus Leaching in Greenhouse Column Studies

We tested the efficacy of matrix based fertilizer formulations (MBF) that reduce NH4, total phosphorus (TP), total reactive phosphorus (TRP) and dissolved reactive phosphorus (DRP) in leachate. The MBF formulations cover a range of inorganic N and P in compounds that are relatively loosely bound (MBF1) to more moderately bound (MBF2) and more tightly bound compounds (MBF3) mixed with Al(SO4)3 H2O and/or Fe2(SO4)3 and with the high ionic exchange compounds starch, chitosan and lignin. Glomus interadicies, a species of arbuscular mycorrhizal fungal spores that will form mycorrhizae in high nutrient environments, was added to the MBF formulations to increase plant nutrient uptake. When N and P are released from the inorganic chemicals containing N and P the matrix based fertilizers likely bind these nutrients to the Al(SO4)3 H2O and/or Fe2(SO4)3 starch–chitosan–lignin matrix. We tested the efficacy of the MBFs to reduce N and P leaching compared to Osmocote® 14-14-14, a slow release fertilizer (SRF) in sand filled columns in a greenhouse study. SRF with and without Al and Fe leached 78–84% more NH4, 58–78% more TP, 20–30% more TRP and 61–77% more than MBF formulations 1, 2, and 3 in a total of 2.0 liters of leachate after 71 days. The concentration and amount of NO3 leached among SRF and MBF formulations 1 and 2 did not differ. The SRF treatment leached 34% less NO3, than MBF3. Total plant weight did not differ among fertilizer treatments. Arbuscular mycorrhizal infection did not differ among plants receiving SRF and MBF formulations 1, 2 and 3. Although further greenhouse and field testing are called for, results of this initial investigation warrant further investigation of MBFs.

Nitrogen Accumulation and Use by a Young Loblolly Pine Plantation in Southeast Oklahoma: Effects of Fertilizer Formulation and Date of Application

Abstract Practices that enhance crop tree nitrogen (N) accumulation and use improve the efficiency of forest fertilization operations. This study was established to explore the N accumulation and use by a young loblolly pine plantation in response to (1) season of fertilizer application, (2) herbaceous vegetation suppression, and (3) fertilizer formulation. Water-soluble and slow-release urea formulations were applied to single-tree plots in January/February, April, June, August, and October of 2001 and 2002. Herbaceous vegetation was suppressed where appropriate with glyphosate. Foliage N accumulation was measured 1 and 2 months after fertilization; N use efficiency was measured 1 year after fertilization. Between 0.3 and 8.0% of applied N was recovered by the foliage within 1 month of application and 7–26% of applied N was used for stem growth within 1 year of application. In both years of this study, summer and fall applications produced the highest N accumulation and use. Suppressing herbaceous vegetation enhanced N accumulation and use when the plantation was 3 years of age (with an average tree height of 6 ft in January 2001). N accumulation and use of slow-release urea was similar to or lower than that of water soluble urea in both years of the study.

Density Changes around Phosphorus Granules and Fluid Bands in a Calcareous Soil

We employed x‐ray computed microtomography (X‐ray CT) to observe differences in moisture around fertilizer P granules (monoammonium phosphate, MAP) versus injection zones of fluid P fertilizer (technical grade monoammonium phosphate, TG MAP) in a calcareous soil over time. X‐ray CT allows nondestructive visualization of small columns containing soils and fertilizers. We were able to visualize the increase in density around the highly hygroscopic fertilizer granule over time. It appeared that both water flow toward the granule and precipitation of P could be responsible for the development of about 1 mm thick high density zone immediately adjacent to the granule. The mass flow of water toward the granule may have slowed or restricted the diffusion of fertilizer P from the granule, thus increasing the chances for P fixation through precipitation reactions. Also, the granule became less dense with time indicating the progress of granule dissolution. In contrast, injection of fluid fertilizer (TG‐MAP) in soil did not result in moisture changes over time as evidenced by a lack of X‐ray CT detectable density differences in the soil column. These data support previous findings that, when P is supplied in granular form, P diffusion and isotopic lability in calcareous soils are reduced compared with equivalent liquid fertilizer formulations, probably due to precipitation reactions induced by osmotically induced flow of soil moisture into the fertilizer granule.

Desenvolvimento e avaliação de um controlador eletrônico para equipamentos de aplicação de insumos

Com este trabalho, objetivou-se o desenvolvimento e avaliação de um sistema de controle para compensar a variação na rotação de acionamento dos dosadores de fertilizantes sólidos de um equipamento para formulação, dosagem e aplicação de fertilizantes sólidos no sulco, a taxas variáveis, em função da alteração da temperatura do óleo hidráulico. Desenvolveram-se controladores do tipo PID, para assegurar a manutenção precisa das rotações desejadas nos motores hidráulicos de acionamento dos dosadores de fertilizante. O equipamento foi testado em laboratório, utilizando-se sinais de testes padronizados, onde foi avaliado o seu comportamento em função do aquecimento do óleo hidráulico. Os testes realizados mostraram que o sistema de controle de rotação implementado foi adequado, mantendo inalterado o comportamento do sistema hidráulico, mesmo na ocorrência de variação da temperatura do óleo hidráulico.

Gamaespectrometria, resistividade elétrica e susceptibilidade magnética de solos agrícolas no noroeste do estado do Paraná

Gamma-ray spectrometry, electrical resistivity, and magnetic susceptibility measurements were taken from agricultural areas near the City of Maringa, in the Northwest region of the Parana state, south Brazil, in order to characterize the spatial distribution of radionuclides (K, eU, and eTh), the apparent resistivity, and the magnetic susceptibility determined for soils. Three different types of soils are present in this agricultural area: Alfisoil, clayey texture Oxisoil, both deriving from Lower Cretaceous basalts of the Serra Geral Formation; and medium texture Oxisoil from reworked Serra Geral and Goio-Ere formations, the latter deriving from sandstones of the Upper Cretaceous Caiua Group. It could be observed that in more clayey soils both concentration of radionuclides and susceptibility values are higher than in more sandy soils, especially due to the higher adsorption in the former and to the higher availability of magnetic minerals in the latter. The average ppm and Bq Kg-1 grades for K, eU, and eTh in the areas under anthropic activity are of 1766-54.75, 0.83-10.22, and 1.78-7.27, respectively. These grades are significantly higher than those of non-occupied or non-fertilized areas (1101-34.15 K, 0.14-1.69 eU, and 1.31-5.36 eTh in ppm and Bq Kg-1, respectively.) Correlations were observed between uranium and clay, uranium and magnetic susceptibility, uranium and organic matter, and between electric resistivity and clay grades. Varied concentrations of radionuclides were also observed in different fertilizer formulations applied to soy and wheat cultures. Apparent electric resistivity values between 25 and 647 Ohm.m and magnectic susceptibility values between 0.28 e 1.10 × 10-3 SI due to clay and magnetic minerals represented important soil discrimination factors in the study area that can be incorporated as easy, low-cost soil mapping tools.

EVALUATION OF SLOW-RELEASE FERTILIZER MATERIALS ON SELECTED VEGETABLE CROPS

Despite some advantages, adoption of slow-release fertilizers in vegetables has been slow primarily due to cost. In crops fertilized with ground equipment, growers can make fewer trips through the field and assure fertilizer is present when conditions prevent application. With drip irrigation, some materials are difficult to inject, however, Nitamin is a new injectable liquid produced by Georgia Pacific. Thus, with plasticulture, growers can inject less frequently and potentially use lower rates. Granular and liquid formulations of slow-release fertilizer were tested on onions (Winter 2003–04), cabbage (Winter 2003–04) and pepper (Spring 2004) in Georgia. Combinations of traditional fertilizer with slow-release formulations and various rates of slow-release fertilizer alone were compared to a standard fertilizer program on these crops in separate experiments. The slow-release contains only N. So, other nutrients were held constant. Otherwise normal cultural practices were employed. Crops were harvested at maturity and data collected on yield and quality. In cabbage, with at least 50% of the standard N rate using the slow-release fertilizer, yields were comparable to the standard. Results on onions were similar with N rates of at least 75% of the standard for the liquid material; the granular formulation did not perform well. Split applications of slow-release fertilizer and combinations with standard fertilizer worked well for cabbage, but not for onions. Results on pepper, although inconclusive, indicated it was possible to get comparable yields at lower N rates with the slow-release material. Based on these results, lower N rates are possible on cabbage and onions with slow-release fertilizers which may make them economically feasible while providing application advantages to growers.

EFFECT OF FOLIAR FERTILIZATION OF CA, B AND ZN IN THE QUALITY OF PEACH (PRUNUS PERSICA L. BATSCH) ´DIAMANTE´

The nutrition during fruit development in the most important factor that influences quality and postharvest behaviour. The objective of this study was to evaluated the relationship between foliars fertilizers and refrigerated storage conditions and quality in 'Diamante' peach. Four formulations of foliars fertilizers were evaluated; Tl= Sagaquel-calcio®; T2=Nutriboro®; T3=Nutrizinc® and T4= Sagaquel-calcio + Nutriboro + Nutrizinc. The criterion used for fruit harvest was external coloring. In this case, fruits were harvested when one fourth of the fruit was yellow. For the postharvest analyses, four periods of storage were evaluated: 1 (initial), 2 (1 week at 5°C), 3 (2 weeks at 5°C), 4 (3 weeks at 5°C + 3 days at 20°C). On each sampling date the following variables were determined: pulp firmness, tritatable acidity, total soluble solids, vitamin C; and weight loss. At the beginning of storage, the fruits of the trees fertilized with Nutriboro had the highest content of total soluble solids. Successively, the highest content of total soluble solids was found in the fruits of the trees fertilized with Sagaquel-calcio + Nutriboro + Nutrizinc had the highest content of total soluble solids. At the beginning of storage the fruits of the trees fertilized with Sagaquelcalcio + Nutriboro + Nutrizinc had the highest fruit firmness Successively, no statistically significant differences were found. In general the fruits of the trees fertilized with Nutriboro had the highest titratable acidity. After tree weeks of storage at 5°C + 3 days at 20°C, the fruits of the trees fertilized with Nutrizinc and Sagaquel-calcio + Nutriboro + Nutrizinc had the highest vitamin C. The fruits that had the lowest weight loss were those fruits from trees fertilized with Nutrizinc.

EVALUATION OF FERTILITY PRACTICES FOR VIDALIA ONIONS

Fertilizer rates of N, P, K were evaluated over 4 years (2000–03) as were different sources of experimental and commercial fertilizers. The highest total yields and yields of jumbos (≥7.6 cm) occurred with nitrogen rates of 140–168 kg·ha–1. Neither phosphorus nor potassium rates had an affect on total yield. Phosphorus rates of 0-147 kg·ha–1 and potassium rates of 0–177 kg·ha–1 were evaluated. Increasing nitrogen fertilizer resulted in increasing leaf tissue nitrogen, but did not affect P, K, Ca, or S. Increasing phosphorus fertilizer increased leaf tissue phosphorus only slightly (p = 0.060) with no affect on other leaf nutrient levels. Increasing potassium fertilizer did affect leaf tissue potassium 2 out of 4 years with none of the other leaf nutrient levels affected. Several fertilizers were also evaluated including an experimental fortified peat (10%N), calcium nitrate, ammonium nitrate, diammonium phosphate, 5–10–15 (56 kg·ha–1 N), 18-6-8 liquid, 14–0–12 8%S liquid, 19–8–19 slow-release at rates of 140 and 168 kg·ha–1 nitrogen. All were used to supply 168 kg·ha–1 nitrogen unless noted otherwise. P and K were supplied according to soil test recommendations unless they were part of the fertilizer formulation. There were no differences between the different fertilizer sources for total yield and differences in jumbo yields only occurred one year out of three years of testing and for medium (≥5.1 and <7.6 cm) yields there were differences two years out of three years of testing.

Source, Application Method, and Cultivation Effects on Recovery of Elemental Sulfur as Sulfate‐S in Incubated Soils

Elemental sulfur (S) may have lower costs, but lack of its availability as plant‐available sulfate‐S (SO4‐S) at the time of crop uptake may render it ineffective as an S fertilizer. Four incubation experiments were conducted to investigate the comparative effects of particle size of elemental S and fertilizer products, application methods, and cultivation techniques on the recovery of elemental S as SO4‐S in four soils. Fertilizer products with fine elemental S particles (Flowable S, Fine S) or granules (crushed Bentonitic S) showed much higher recovery than those with large elemental S particles and granules (Urea S and Bentonitic S). Recovery of SO4‐S from different application methods followed a sequence of incorporation<broadcasting<banding<nesting. Cultivation generally increased recovery and the more thorough the cultivation, the greater the impact was. Immobilization of SO4‐S by microbes was not evident during first 6 wk of incubation, but it became evident in some soils and treatments after 6 wk of incubation period. Soils with high initial N and S concentrations showed more recovery. Overall, recovery was reduced by any factor that restricted mixing of elemental S particles into soil or reduced their exposed surface area for microbial action. Thus, appropriate fertilizer formulation as well as application and cultivation techniques to promote thorough mixing of elemental S particles into soil were critical to improve oxidation of elemental S to plant‐available SO4‐S.

Anion Species in Fertilizers Affect Growth and Development in Bedding Plants

Currently, formulation of inorganic fertilizers is based on cation amounts such as NH4, K, Mg, Ca, Fe, MN Cu, and Zn, whereas anion species and amounts are viewed, with few exceptions, as necessary fillers. The delivery of cations in the nutrient solution is associated with an anion such as Cl, SO4, NO3, PO4 or CO3. These anions at higher concentrations can result in different growth responses by altering the rhizosphere pH, soluble salts, and influencing the uptake of both cations and anions. The impact of these anions has not been extensively studied in the formulation of inorganic fertilizers. Several experiments assessed the effect of SO4 and Cl on root and shoot growth and development of bedding plants represented by petunia, impatiens, and vinca. In all treatments, plant height, shoot and root dry weight, and flower number decreased with an increase in Cl concentration. Root morphology was marked by fewer total roots and shorter primary and secondary roots when grown with Cl anions compared to the plants grown with SO4 anions. This indicates that anions have a larger role in determining optimum fertilizer formulation than previously believed. This information provides an additional tool in formulating fertilizers for greenhouse bedding plant production.

Growth Response of Hakonechloa macra (Makino) `Aureola' to Fertilizer Formulation and Concentration, and to Dolomitic Lime in the Potting Mix

The shade-tolerant, variegated grass Hakonechloa macra `Aureola' is a valuable ornamental. In an experiment replicated in two growing seasons, Hakonechloa plants were fertilized at each irrigation (fertigation) with factorial combinations of three fertilizer formulations (N:P molar ratios 5:1, 10:1, and 20:1) at five N concentrations (2, 4, 8, 16, and 32 mmol·L-1), along with an unfertilized control, to determine the effect of N:P ratio and N concentration on vegetative growth and to establish fertility guidelines for production. Root dry weight and tiller bud growth increased slightly as N:P ratio increased. Fertilizer N concentration of 16 mmol·L-1 promoted the most shoot growth, whereas the number of tiller buds and root growth were greatest at 2 and 4 mmol·L-1 N. No interaction occurred between N:P ratio and fertilizer concentration. Results indicate that an N concentration of 8 mmol·L-1, with an N:P ratio of 10:1 or 20:1 is optimal for production of Hakonechloa. At this fertilizer concentration, the mean electrical conductivity of extracts obtained by a solution displacement extraction (pour-through) procedure was 2.3 ± 0.45 dS·m-1 (mean ± standard deviation). Tissue nutrient concentrations of N, P, K, Ca, and Mg were (in mg·g-1): 24.0, 2.8, 14.3, 2.1, and 2.1, respectively. In a concurrent study, Hakonechloa plants were grown in pine bark: peat: sand mix with dolomitic lime added at 0, 1.2, 3.6, and 9.5 kg·m-3 producing pH ranging from ≈4.5 to 7.2. Growth of Hakonechloa was greatest with no lime (pH 4.5) and declined markedly as the rate of lime increased. Concentrations of N, P, and K in shoot tissue were greatest at a pH between 4.5 and 5.6 (0 and 1.2 kg·m-3 dolomitic lime). These findings clearly support recommending production of Hakonechloa in soilless potting mix with pH ≈4.5 and constant fertigation with N at 8 mmol·L-1.

Progress in Mineral Nutrition and Nutrient Management for Vegetable Crops in the Last 25 Years

K. Early manufactured fertilizers were mostly solid materials, but in the middle part of the 20th century, liquid versions of fertilizer materials, particularly N, became available and their use increased rapidly in the latter quarter of the 20th century. The liquid materials, containing N and P, were very useful as vegetable transplant starter fertilizers, and the liquid N materials were used as easily-applied sidedress fertilizers. During the last 25 years, many advances have been made in the formulation of mixed-nutrient liquid fertilizers, many containing most of the essential nutrients for plant growth. The major factors driving the development of liquid fertilizers include the ease and uniformity of application, the advent of drip irrigation and fertigation (the application of nutrients with the irrigation system), and the development of modern hydroponic and greenhouse vegetable production systems. Drip irrigation and greenhouse vegetable production will be discussed later in this paper. FERTILIZER SOURCES. Over the last 25 years there were numerous researchers evaluating fertilizer sources for specific nutrients for vegetable crops, for example the work by Locascio et al. ( 1981) and Locascio and Martin (1985). Much of the work focused on N fertilizers, but there also has been considerable work on P, K, and micronutrient sources. The researchers had to account for the possibility of responses to associated nutrients supplied with the nutrient of interest. For example, potential crop responses to S, Ca, or K had to be considered in N-source studies involving CaNO 3 , NH 4 SO 4 , and KNO 3 . In most studies with most vegetables, there were negligible crop responses to N source so that most sources can be recommended for vegetable culture and the choice may depend on cost. CONTROLLED-RELEASE FERTILIZERS AND NITRIFICATION INHIBITORS.