Literature Review. Overview on research that has been conducted into the agronomic, horticultural and environmental applications of natural zeolites.

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1 Literature Review Zeolite (Clinoptilolite tuff) and it s beneficial effects in Horticulture to Increase Plant Growth Compiled by Michael Leu & Daniel FitzHenry Ming, D. W., Allen, E. R. (2001) Use of natural zeolites in agronomy, horticulture and environmental soil remediation: in Natural Zeolites, Occurrence, Properties, Applications, D. L. Bish and D. W. Ming, eds., Mineralogical Society of America, Reviews in Mineralogy and Geochemistry, Volume 45, 2001, pp Overview on research that has been conducted into the agronomic, horticultural and environmental applications of natural zeolites. In the next century it is possible that a huge industry will develop based on natural zeolites. Soil conditioning by zeolites might lead to greater agricultural production J. V Smith (1988). The authors agree with J. V. Smith that the potential applications for natural zeolites are huge, provided the proper research is conducted to fully utilise their unique properties. Discusses several commercial applications of zeolites in enhancing plant growth, viz. a) In-ground/field applications as slow-release fertilisers when loaded with Urea, potassium etc. High commercial potential because of demands for increased fertiliser-use efficiency and environmental protection. b) Substrates for plants in greenhouses. c) For use potting mixes for all plants. d) As fertilisers and soil conditioners on golf greens. e) As slow-release fertilsers, in areas where environmental issues are of concern. f) As remediation agents for environmental problems, e.g. heavy metal contamination. It is essential to develop products and formulations that meet a specific horticultural, or environmental use, instead of a one-size-fits all approach. Due to the arrangement of Al and Si in the three dimensional framework of SiO 4 and AlO 4 tetrahedra and the channels and cages that are created by this framework, each zeolite has unique selectivities for various cations. Clinoptilolite has a selectivity sequence of: Cs> Rb> K> NH 4 > Ba> Sr> Na> Ca> Fe> Al> Mg> L1 (Ames, 1960) Clinoptilolite-rich tuff added with N fertilisers to rice paddies in Japan improved the availability of N in paddy soils. Mazur et al. (1984): The addition clinoptilolite tuff to soils increased the soil s CEC and ph in most cases. Yields of potato, barley, and wheat increased from between 2.8% to 79% depending on the crop, fertiliser treatment, and clinoptilolite addition as compared with fertilised and unfertilised controls in a range of Ukrainian soils. 1

2 Suwardi et al. (1994) characterised the mineralogy and chemistry of 22 natural zeolites deposits from Japan and Indonesia for their potential as soil conditioners. An application of 50 Mg ha -1 of 1mm sieved clinoptilolite-rich tuff (approximately 82 wt% clinoptilolite) resulted in tomato plants producing 30% more above ground biomass compared to tomatoes grown in untreated soils. Petrovic (1990) determined the optimum particle size of clinoptilolite added to golf course sand was between 0.1mm to 1.0mm in order to maximise benefits for water infiltration, water availability, and aeration. Fertiliser-use Efficiency and Prevention of Nutrient Leaching The use of most natural zeolites increases fertiliser efficiency and reduces the leaching of nutrients. Fertiliser-use efficiency and reduced leaching are a function of each other. Plant essential nutrients (e.g. N in the form of NH 4 ) may be exchanged (by saturating the zeolite in an aqueous solution containing the soluble fertiliser) onto the zeolite exchange sites, where the nutrients can subsequently be slowly released (natural slow release fertiliser) for plant uptake. Volatilisation of gaseous N (e.g. as NH 3 or N 2 ) can also be reduced if NH 4 is exchanged onto zeolite exchange sites so that it is unavailable for conversion to these gaseous phases via microbial processes. Rarely does the fertiliser-use efficiency of conventional fertiliser applications in field agriculture exceed 50% for most crops. Zeolites increase fertiliser-use efficiency. Zeolites exchange sites act as sinks for the dissolved cationic nutrients of soluble fertilsers such as anhydrous ammonia, urea, potash, and ammonium sulphate. Over time these nutrients are exchanged off zeolite sites where they become available for plant uptake. Minato (1968), Japan: Plant available nitrogen for growing rice increased by 63% when 80 tonnes ha -1 of clinoptilolite-rich tuff and a NH 4 -fertiliser were added to coarse-textured soil. Tsitsishvili et al. (1984), Georgia, Russia: The addition of clinoptilolite-rich tuff at a rate of 400 kg ha -1 (particle size 2mm to 5mm) along with NH 4 NO 3, superphosphate, and K fertilsers, increased fertiliser-use efficiency by 50% in the production of geraniums when compared with standard fertiliser practices. This paper contains numerous examples of growing trials with straight zeolite and fertiliserexchanged zeolite. The vast majority of trials show improvements in fertilsers efficiency and crop yields relative to controls. Variation was primarily due to soil type and application rates. Below is summary of some agricultural/horticultural trials results. Bouzo et. al. (1994), Cuba: Sugarcane yield doubled from 38 tonne ha -1 to 75.4 tonne ha -1 in soil banded with an application of 3 tonne ha -1 clinoptilolite-rich tuff. It was found that the amount of N fertiliser could be reduced by 50% for some soils without yield reductions. Huang and Petrovic (1994), Oregon, USA: The leaching of NO 3 - and NH 4 was 86% and 99% lower, respectively, in sand-based putting greens with the addition of 10 wt% clinoptilolite-rich tuff (Zeolite). 2

3 Slow-Release Fertilisation Slow-release fertilisation from zeolites involves the slow exchange of plant nutrients from exchange sites. Two primary mechanisms can be employed to achieve slow release of nutrients from zeolites. (1) slow-release fertilisation by ion exchange (Slow-release fertilisation by ion exchange involves exchange, nutrient loading, of a zeolite with a nutrient cation) and (2) slow-release fertilisation by a combination of mineral dissolution and ion exchange involves the addition of a mineral fertiliser (e.g. phosphate rock) that dissolves and releases cations that are available either for exchange at nutrient-loaded zeolite sites or for direct plant uptake. Many studies have been conducted exchanging a zeolite with a plant nutrient cation to be used as a slow-release fertiliser. Most studies have focused on loading clinoptilolite with NH 4 -N and K because of the zeolite s pronounced selectivity for those cations over Ca 2, Mg 2 and Na. Hershey et al. (1980): 50 grams of K -clinoptilolite per 1.5 litres of potting medium produced 3-month yields of chrysanthemums equal to those obtained in the potting medium without zeolite with a nutrient solution containing 234mg K /litre, which is 6.7 times more K than the potting medium fertilised with K -clinoptilolite. Over 90% of the K from the KNO 3 source leached out of the potting soil after 3 litres of leachate were collected; however, the clinoptilolite exhibited a slow-release of K and only 10% of the K on the zeolite exchange site had been leached. Williams and Nelson (1997), USA: 20 vol. % nutrient-treated (K or PO exchanged zeolite) clinoptilolite tuff was added to soilless medium for the growing of chrysanthemums and showed significantly reduced nutrient leaching compared to controls. Carlino et al. (1998) reported similar results for chrysanthemum growth and nutrient leaching in potting medium with the addition of N-, K- and P-treated clinoptilolite tuff. Perrin et al. (1998b), USA: Field agriculture, corn grown in sandy loamy soil amended with NH 4 -exchanged clinoptilolite-rich tuff (NH4-CEC 165 cmol c kg -1 ). Various particle sizes <0.25mm, 0.25mm 2.0mm, 2.0mm 4.0mm; application rates 112, 224, 336 kg N ha -1 of NH 4 -exchanged clinoptilolite-rich tuff. Nitrogen-use efficiency ranged from 95.2% to 72.0% in NH 4 -exchanged clinoptilolite amended soils after 42 days of plant growth, whereas the N-use efficiency in soils fertilised with (NH 4 ) 2 SO 4 ranged from only 29.7% to 76.3%. No significant differences in corn growth were observed among the N fertilisers. This study illustrates the potential of using NH 4 -exchanged zeolites as a slow-release N fertiliser to improve N-use efficiency, while sustaining normal corn production. The control leached 93% to 97% of total N applied (NH 4 ) 2 SO 4 to the quartz sand, whereas the NH 4 -exchanged clinoptilolite leached 24.9% to 72.1% total N. The particle size of the added clinoptilolite had a significant impact on the amount of N leached through the quartz sand. Large 2.0mm to 4mm particles and significantly less leaching of total N (24.9% to 32.5%%)than medium (0.25mm to 2.0mm) and small-sized (<0.25mm) that had leaching rates of 53.4% to 68.4% total N and 44.4% to 72.1% total N, respectively. These leaching rates reflect the expected lower exchange rates of larger particle sized clinoptilolite-rich tuff because more time is required for intra-particle diffusion. Zeolites may have the ability to protect NH 4 on zeolite exchange sites from microbial conversion of NH 4 to NO 3 because nitrifying bacteria are too large to fit into the channels and cages within the zeolite structure where the NH 4 resides. MacKown (1978) reported that nitrification rates decreased in a loamy sand by 11% and in a silty clay loam by 4% when using an equivalent rate of 30 tonne ha -1 of NH 4 -exchanged clinoptilolite-rich tuff. 3

4 Other plant-essential nutrients, secondary and micronutrient cations, may be exchanged onto zeolite exchange sites, e.g. Ca 2, Mg 2, Zn 2, Cu 2, Fe 2, and Mn 2. However, most natural zeolites are not particularly selective for these divalent cations and, as might be expected, they are usually more difficult to exchange. Comprehensive section on Fertilisation by Mineral Dissolution and ion exchange Slow-release fertilisation has been achieved by a combination of zeolite ion exchange and mineral dissolution (e.g. apatite-rich phosphate rock, (Ca 5 (PO 4 ) 3 F) to the slow-release of K, NH 4, and other cations exchanged onto zeolite exchange sites, the dissolution of apatite-rich phosphate rock, for example, is enhanced by the exchange of dissolve Ca 2 onto zeolite exchange sites. Significantly increases solution P concentrations compared to phosphate rock without zeolite additions. The dissolution and exchange reaction proceeds until an equilibrium state is approached, the reaction stops unless another sink, such as nutrient uptake by plant roots, removes some of the reaction products, again driving the dissolution and ion-exchange reactions. Exchange sites, Ca 2 sinks, drive the dissolution of the phosphate rock. Mnkeni et al. (1994), Tanzania: Growth of maize in greenhouse pot experiments. Triple superphosphate (40 mg P kg -1 ) was used a P source for the control. Plant uptake of P nearly doubled in the soil containing reactive phosphate rock and zeolite at a ration of 1:100. Other soluble minerals or phases may be precipitated along with zeolite (i.e. occluded salts) or phases may be precipitated by reactions with cations removed from zeolite exchange sites and other elements removed from waste streams. RIM-NUT process: developed as a method for reducing the eutrophic potential (i.e. potential for depletion of O 2 in water by microorganisms) of municipal and industrial wastewater by combining ion exchange from zeolites and precipitation processes to selectively remove ammonium NH 4 and/or phosphate ions, H 2 PO - 4. Wastewater is passed through columns of containing a zeolite or in a modified version zeolite plus an anion exchange resin. Exhausted columns are regenerated with 0.6m NaCl. Effluents from regeneration, containing NH 4 and/or phosphate ions, H 2 PO - 4, are then added to an Mg salt under controlled ph conditions to produce a high-grade MgNH 4 PO 4.6H 2 O fertiliser. Am 11,000m 3 per day plant has been commissioned in Italy. Sow-release fertilisation may also be obtained by zeolite ion exchange and mineral dissolution of nutrient salts precipitated on the zeolite. The salt phase either precipitates on zeolite crystal surfaces or precipitates as an occluded salts in the channels of cavities of the zeolite crystal. Plant essential elements are released into solution as the precipitated salts begin to dissolve and additional plant-essential cations (e.g. K, NH 4 ) are slowly released into solution via ion exchange from zeolite exchange sites. Zeolite can be treated in a reactor to precipitate KH 2 PO - 4. Park and Komarneni (1997, 1998), California: Used molten salt treatments of KNO 3 and NH 4 NO 3 to occlude these salts in zeolite, the salts precipitated in the zeolite. They examined the total uptake of N for occluded and exchanged NO 3 and, exchanged NH 4. They determined the total N content for the molten NH 4 NO 3 -treated zeolite was considerably higher than the total N content of NH 4 -exchanged zeolites. Both types of treated zeolite exhibited similar NH 4 release rates, where was NH 4 was slowly and steadily released over a 30 leaching experiment. A greater percentage of total occluded NO - 3 was released compared with the percentage of NH - 4, which suggested that occluded NO 3 is more readily available for release than 4

5 exchangeable NH 4. Zeolite s nutrient content (N) can be significantly increased by the addition of occluded salts. Zeoponic Plant-Growth Substrates. The cultivation of plants in artificial soils having zeolites as a major component, e.g. zeolite, peat and vermiculite. Research has been focused on developing synthetic soils/potting mixes with desirable physical properties that supply a balanced diet of plant nutrients for many growth cycles without fertiliser additions. Some mixtures consist of phosphate rock, NH 4 and K-exchanged zeolite, and quartz sand. Many successful growing trials and some commercial products. Zeolites as Carriers for Herbicides, Pesticides and other Organic Compounds. Research into this application has increased in recent years because of concern for protecting the environment from chemicals migrating into groundwater and runoff. Zeolites have potential as carriers for herbicides, pesticides and other organic compounds, although most of these compounds are too large to access the channels and cages of natural zeolites. Organic molecules too large to fit into zeolite channels can be absorbed onto charged sites on the crystal s surface. Adsorption is dependent on many factors, especially ph. Some bio-insecticides are not stable and degrade rapidly in UV radiation. Zeolites can be used as a photostabiliser for bio-insecticides (e.g. bacteria to control moth larvae). Environmental Soil Remediation Summary on research conducted in to using zeolites to treat soil contaminated with heavy metals a(e.g., Cu, Cd, Pb, Zn) and radionuclides (e.g. 137 Cs, 90 Sr 2 ). Commercial applications of Natural Zeolites The current world-wide commercial market for natural zeolites in agricultural and environmental is relatively small compared to its potential. Many factors control a zeolites performance e.g. many soils have distinct and complex chemical and physical properties. A major commercial focus has been selling natural zeolites to the turfgrass industry as it is high-cash crop and the industry is driven by environmental demands to reduce fertiliser runoff and increase fertiliser-use efficiency. Nutrient-enriched clinoptilolite-rich tuff is sold as a slow release fertilsers and soil conditioner for the turfgrass and horticultural industries. ZeoPro TM consists of K and NH4-exchanged clinoptilolite-rich tuff and a synthetic hydroxyapatite that supplies Ca and P (micronutrients may also be supplied by the synthetic hydroxyapatite). The nutrient content of ZeoPro TM is 0.1wt%N, 0.05wt% P, 0.6wt% K; low compared to conventional fertilisers. Grass clippings (Penncross creeping grass) from sand amended with ZeoPro TM showed an 81% increase in dry weight compared to the control grass fertilised with 1lb/1000ft 2 of N as (N-P-K). Zeoponic applications have been commercialised for growing flowers and vegetables. Lewis, M. D., Moore, F. D., and Goldsberry, K. L. (1984) Ammonium-exchanged clinoptilolite and granulated urea as nitrogen fertilisers: in Zeo-Agriculture: Use of 5

6 Natural Zeolite in Agriculture and Aquaculture, W. G. Pond and F. A. Mumpton, eds., Westview Press, Boulder Colarado, pp These trials demonstrated significant increases in plant growth and fertiliser retention. Ammonium-exchanged clinoptilolite acts as a slow-release fertiliser increasing N availability in medium-textured soils and decreasing NO 3 - N loss due to leaching in a coarse, porous soil. Untreated clinoptilolite acts as a protectant against the deleterious effect of urea. Tests Trials were conducted using NH 4 -exchanged clinoptilolite and granulated clinoptilolite mixed with urea. Evaluated as slow-release N fertilisers in greenhouse radish experiments. Coarse-textured porous soils permit free water movement and leaching of nitrate; an effective slow release fertiliser will alleviate this problems. Methods Particle size <325 mesh (<44 microns). The ammonium-exchanged clinoptilolite contained 2.99% N by weight. The exchangeable NH 4 content was 128 meq/100g. The untreated clinoptilolite granules urea mixture provided 2.34% N by weight. The cation exchange capacity of the clinoptilolite was reported to be 193 meq/100g. The N fertilisers were added to provide 150mg and 200mg N/kg of dry soil. The NH 4 (ammonium)-exchanged clinoptilolite:soil ratios were 5.0 and 6.7 grams/kg; 5.0 and 6.7 kilograms per tonne of soil, i.e. 0.5% and 0.67% by weight of soil. Clinoptilolite urea: soil ratios were 6.4 and 8.6grams/kg; 6.4 and 8.6 kilograms per tonne of soil. Each treatment was placed as a layer 2.5cm below the soil surface. Controls were straight ammonium sulphate and urea fertilisation. Results Nitrogen uptake by plants grown in the NH 4 (ammonium)-exchanged clinoptilolite was far greater than that of the ammonium sulphate control. NH 4 -exchanged clinoptilolite resulted in increases in plant growth (leaf area, plant dry weight, root fresh weight), NO 3 - uptake, and residual soil NH 4. An increase in residual soil NO 3 - and a reduction in leachate NO 3 - in coarse-textured soil indicated that the NH 4 -exchanged clinoptilolite behaved like a slow-release N fertiliser. The clinoptilolite urea mix did not suppress growth as did the straight urea treatment. Free NH 3, liberated by the urea was probably exchanged as NH 4 by the clinoptilolite, thus preventing injury of radish plants. When urea was applied in the absence of clinoptilolite to the coarse-textured soil, toxicity symptoms became evident and the dry weight of the plant was greatly reduced. The clinoptilolite provided a high level of seedling protection. The benefits of adding clinoptilolite to a large amount of urea in a coarse-textured soil were demonstrated by significant increases in leaf area, whole plant dry weight, root fresh weight, and N uptake. It was apparent that only after exchange from the zeolite is NH 4 available for nitrification, thereby slowly releasing the N for oxidation at a rate beneficial for plant 6

7 uptake whilst simultaneously retarding overproduction and concomitant losses through leaching. Plant responses to NH 4 -exchanged clinoptilolite were greater in the medium-textured soil than the coarse-textured soil. This was possibly due to increased NH 4 fixation and a relative lack of O 2 to promote nitrification resulting from the higher clay content of the medium-textured soil. Eberl, D. D., Barbarick, K. A., and Lai, T. M. (1995) Influence of NH4-exchanged Clinoptilolite on nutrient concentrations in Sorghum-sudangrass: in Natural Zeolites 93: Occurrence, Properties, Use, D. W. Ming and F. A. Mumpton, eds., International Committee on Natural Zeolites, Brockport, New York, pp Investigation undertaken to study how NH4-exchanged clinoptilolite can influence plant uptake of a variety of chemical elements, including P, K, Cu, Mn, Zn, Mg, Ca, Fe, and Cd. Refer to paper for details of soils types used. Tests The ability of NH 4 -exchanged clinoptilolite to influence the uptake of nutrients by sorghum-sudangrass was tested in greenhouse experiments in soil-phosphate rock (Prock)-ammonium (NH 4 )-zeolite systems. Methods Clinoptilolite-rich tuff (<100 mesh, <160 microns, <0.16mm) were exchanged with NH 4 by shaking equal volume of clinoptilolite and 0.5 M NH 4 Cl solution overnight and then washing several times with distilled water to remove excess salt. Clinoptilolite-P-rock ratios of 0 to as much as 7.5 were used, with P rates of 100 to 400 mg P/kg soil. Top growth was harvested at 3 to 6 week intervals to study nutrient uptake. The available nutrients remaining in the soil were determined. Some clinoptilolite/p-rock mixtures were ground to <100 mesh. Results The NH 4 -clinoptilolite increased yields by as much as 65% over control experiments and significantly increased the concentrations of nutrient elements in plant matter. For example, P was increased by as much as 100%, Cu by 100%, Mn by 450%, Ca by 50%, Mg by 30%, and Zn by 70%. NH 4 -clinoptilolite can mobilise some nutrients and trace elements (particularly Cu and Mn), thereby rendering them more available for uptake by plants. At least two mechanisms appear to be involved in this mobilisation: (1) a lowering of soil ph caused by nitrification of NH 4 ions from the clinoptilolite; and (2) enhanced availability of nutrients in exchange sites, from which they were made available by dissolution by ion-exchange from sparingly soluble minerals. Uptake of some nutrients may have been enhanced by an increase in their solubility due to a lowering of ph in some soil types by as much a 2 units caused by nitrification of NH 4 ions with time or by plant uptake of NH 4 in exchange for H. The ph of the Keith soil system was insensitive to the clinoptilolite/phosphate rock ratio, probably because the clinoptilolite used in this soil contained calcite that would buffer system ph. 7

8 The concentrations of Cu and Mn in sudangrass increased by 23% and 12% with increasing NH 4 -clinoptilolite application rate independent from a ph effect for the Keith soil, suggesting an ion-exchange mechanism may have enhanced availability. This concept is supported by the increase in extractable soil elements (e.g. as much as 250% increase for Cu) with increasing clinoptilolite/p-rock ratio (0 to 6) for the Keith soil-prock system. Extraction experiments using NH 4 -clinoptilolite and P-rock without soil at constant ph demonstrated an increased availability of nutrients over that expected from simple mixtures (e.g. a two orders of magnitude increase in extractable Cu over that of simple mixing of P-rock and zeolite), further emphasizing the importance of chemical reaction (i.e. such as dissolution by ion-exchange) to nutrient release. Some experiments show that clinoptilolite saturated with monovalent cations was effective in releasing phosphate from rock phosphate exchanging Ca 2 into zeolite exchange sites. Lack of P-response in the Keith soil-system may be related to the presence of calcite, anhydrite and gypsum in the NH 4 -clinoptilolite used. These Caminerals are more soluble than apatite in P-rock, Ca 2 exchange in the zeolite came mostly from their dissolution, thereby releasing carbonate and sulfate, rather than phosphorus to the soil solution. For Further Information Contact Daniel FitzHenry Horticulturist C/- PlantNet P/L Mobile Or plantnet@bigpond.net.au 8

Soil Fertility. Fundamentals of Nutrient Management June 1, Patricia Steinhilber

Soil Fertility. Fundamentals of Nutrient Management June 1, Patricia Steinhilber Soil Fertility Fundamentals of Nutrient Management June 1, 2010 Patricia Steinhilber Ag Nutrient Management Program University of Maryland College Park Main Topics plant nutrition functional soil model