Slow-release urea fertilizer from sulfur,gypsum, and starch-coated formulations

To address nitrogen (N)-related environmental pollution, development of an economical, slow-release urea fertilizer is the need of the hour. A study was conducted on the reduction of nitrogen released from granular urea fertilizer by applying sulfur, gypsum, bentonite, and starch as coating material. Paraffin wax was used as a binder. The dissolution rates were studied by changing the composition of coating mixture using high-performance liquid chromatography. SEM was used to study the morphology of coated urea in terms of smoothness and uniformity. The ultraviolet spectroscopy analysis further authenticated the release behavior of coated urea in terms of nitrogen concentration. Coating material reduced the release rate of nitrogen from urea fertilizer, significantly. Mixture of sulfur and gypsum coating on urea gave slowest release rate of nitrogen from urea fertilizer, i.e., 37%, as compared to uncoated urea and thus seems to be the most promising binding material for product development.     

Nutrient Release Characteristics of Coated Fertilizers by Superfine Phosphate Rock Powder and its Effects on Physiological Traits of Chinese Cabbage

Four kinds of slow release fertilizers were prepared out by coating common compound fertilizer [nitrogen (N)-phosphorus pentoxide (P₂O₅)-potassum oxide (K₂O):15-15-15] with four kinds of superfine phosphate rock powder (SPRP) which accounting for 60% of the total coated materials in mass. Electronic microscope scanning, static water releasing test, soil incubation experiment, and a field experiment were conducted on their nutrient release mechanisms and their effects on physiologic traits of Chinese cabbage. The results showed that all these four kinds of SPRP could markedly improve microstructure and thus release rate. However, their capacity was inferior to controlled release fertilizer (CRF). The four homemade fertilizers increased chlorophyll content, photosynthetic rate, and transpiration rate in the leaves of Chinese cabbage during its late growth stage, and improve the superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) enzyme activities during its ball period. In addition, the four homemade fertilizers improved yield by 20.62%～33.41% and 18.94%～24.44%, respectively, over the common compound fertilizer during 2009 and 2010, and improved sugar-acid and soluble sugar and V_C contents of the head of Chinese cabbage at the harvest stage. There are not obvious differences of physiological traits between the J2 coated CCF fertilizer (JCRF2), Y2 coated CCF fertilizer (YCRF2), and Resin coated CCF fertilizer (CRF). Nutrient release characters and agricultural effect of four homemade fertilizers follow the order: JCRF2≈YCRF2>JCRF1≈YCRF1.     

In Situ Acidulation of Rock Phosphate

This study was undertaken to study the impact of adding <75 μm elemental sulfur (ES) on P availability from a range of <250 μm ground rock phosphates (RP) namely; Minjingu (Mi) from Tanzania, Khouribga from Morocco (Mo) and Duchess (D) from Australia. Italian ryegrass (Lolium multiflorum, Thumpa tetraploid) grown in a glasshouse was used as the test crop and tops were harvested 5 times over 27 weeks. Co-granulating RP and 10.7% ES yielded 30–70% more ryegrass tops than RP alone, with the greatest effect with Mi. Fertilizer P recovery in the tops from the RP was 5.2% with D and 6.5% and 7.8% from Mi and Mo, respectively. ES addition increased this by 51% from Mo, 98% from D and 194% from Mi. Co-granulation of RP with ES has been shown to be an effective means of releasing plant available P to crops from RP with minimal fertilizer processing.     

Field Evaluation of Ammonium Sulfate versus Two Fertilizer Products Containing Ammonium Sulfate and Elemental Sulfur on Soybeans

ABSTRACT

Two separate field trials comparing three different commercial sulfur (S) fertilizers were conducted in 2016 and 2017, respectively, to evaluate their initial agronomic effectiveness in increasing soybean grain yield. The S compounds of these products were elemental S (ES) and ammonium sulfate (AS). The fertilizer sources were (1) AS, (2) granular MAP-10 S (5% ES + 5% AS-S) and (3) bulk-blend (bentonite-ES) + (AS) containing 25% ES + 25% AS-S. Rates of total S applied were 0, 5.6, 11.2, 22.4 and 33.6 kg S ha^?1. A significant S response in grain yield was observed with all S sources. The grain yield was significantly higher with AS than with the other two S sources at S rates ≤22.4 kg S ha^?1 of total S applied but equal for all sources above this rate. All data points for the three S sources followed the same S response function based on a quadratic plateau model when the grain yield was plotted versus AS-S rate applied. This suggests that there was no significant ES oxidation from MAP-10S and (ES) + (AS) products to provide soybean crop growth to maturity. The experimentally observed AS-S rate at which the maximum grain yield was attained in the 2 years of fieldwork was 11.2 kg S ha^?1 while the calculated average AS-S rate based on a quadratic plateau model was 13.4 kg S ha^?1.

Abbreviations: AS: ammonium sulfate; ES: elemental S; MAP: monoammonium phosphate; DAP: diammonium phosphate; TSP: triple superphosphate.     

Assessment of urea coated with pomegranate fruit powder as N slow-release fertilizer in maize

It has been hypothesized that plant polyphenol plus lignin, cellulose, and hemicelluloses can immobilize/remineralize inorganic fertilizers, such as urea, better than polyphenol alone. To test this hypothesis, urea was coated with pomegranate (Punica granatum L.) fruit powder (containing polyphenol+lignin+cellulose) at rates of 0%, 30%, 70%, and 100% (w/w) of fertilizer urea. Fertilizer nitrogen was applied at 100 and 200 mg kg^?1 soil in a clay loam soil. This natural coating material, particularly at the rate of 100% (w/w), improved the distribution of mineral nitrogen (N) and available phosphorus (P) in soil during both early and advanced growth stages of maize and significantly increased total crop N and P uptake at both rates of fertilizer nitrogen compared to urea alone. The results suggest that urea coated with the powder of pomegranate fruit could potentially be an N slow-release fertilizer for use in better synchronizing crop N demand with soil N supply.     

Phosphorus bioavailability of sewage sludge‐based recycled fertilizers

Six phosphorus (P) fertilizers recycled from sewage sludge [Struvite SSL, Struvite AirPrex®, P‐RoC®, Mephrec®, Pyrolysis coal and Ash (Mg‐SSA)] were tested for their plant availability in potted soil of pH 7.2 under greenhouse conditions. The crop sequence simulated a rotation of red clover (Trifolium pratense L.), maize (Zea maize L.), and ryegrass (Lolium perenne L.). Other P fertilizer treatments included: Phosphate Rock (PR), Calcium dihydrogen phosphate [Ca(H₂PO₄)₂], and an unfertilized control. Additionally, soil was regularly inoculated with two strains of plant growth‐promoting rhizobacteria (PGPR; Pseudomonas sp. Proradix, and Bacillus amyloliquefaciens) to test their ability to increase P availability to plants. Sequential P fractionation was conducted to link the amount of readily available P in fertilizers to plant P acquisition. Shoot P content and dry matter of maize decreased in the following order: Struvite SSL ≥ Ca(H₂PO₄)₂ > P‐RoC® ≥ Struvite AirPrex® ≥ Mephrec® > Pyrolysis coal ≥ Mg‐SSA ≥ PR ≥ unfertilized. Rhizobacteria did not affect shoot biomass or P content. The results show that red clover might have mobilized substantial amounts of P. Sequential P fractionation was not suitable to predict the efficacy of the fertilizers. Generally, the sewage sludge‐based fertilizers tested proved to be suitable alternative P sources relevant to organic farming systems. However, the efficacy of recycled fertilizers is strongly dependent on their specific production conditions.     

Laboratory Evaluation on Ammonia Volatilization from Coated Urea Fertilizers

Coated urea fertilizers are assumed to enhance crop yield and reducing the environmental pollution. Nevertheless, many of the coated urea fertilizers are expensive, thus not readily available for most farmers. In addition, many of these fertilizers release N not in tandem with the plant’s need, thus retard growth. Therefore, a laboratory study was conducted to evaluate effects of coated urea fertilizers on N losses via volatilization. Measurement of ammonia volatilization was carried out using the closed-dynamic air flow system. The study for ammonia volatilization was conducted using different rates of fertilizer (50, 100, and 200 kg N ha^?1) with different types of fertilizer (Urea, Sulfur-coated urea; SCU and Gypsum sulfur coated urea using rotating drum; GSCUD) in 37 days of incubation. The results indicate that SCU represents the best fertilizer which decreases the amount of ammonia volatilization at each rate of fertilizer. Besides, the rate of 50 kg N ha^?1 has the lowest percentage of ammonia volatilization. Moreover, the result proved the effectiveness of coating urea fertilizer may reduce the ammonia loss to the environment and new product which GSCUD can be comparable to the commercial product.     

Use of ammonium sulphate as a sulphur fertilizer: Implications for ammonia volatilization

Ammonium sulphate is widely used as a sulphur (S) fertilizer, constituting about 50% of global S use. Within nitrogen (N) management, it is well known that ammonium-based fertilizers are subject to ammonia (NH₃) volatilization in soils with pH > 7, but this has been overlooked in decision making on S fertilization. We reviewed 41 publications reporting measurements of NH₃ loss from ammonium sulphate in 16 countries covering a wide range of soil types and climates. In field experiments, loss was mostly <5% of applied N in soils with pH (in water) <7.0. In soils with pH > 7.0, there was a wide range of losses (0%–66%), with many in the 20%–40% range and some indication of increased loss (ca. 5%–15%) in soils with pH 6.5–7.0. We estimate that replacing ammonium sulphate with a different form of S for arable crops could decrease NH₃ emissions from this source by 90%, even taking account of likely emissions from alternative fertilizers to replace the N, but chosen for low NH₃ emission. For every kt of ammonium sulphate replaced on soils of pH > 7.0 in temperate regions, NH₃ emission would decrease from 35.7 to 3.6 t NH₃. Other readily available sources of S include single superphosphate, potassium sulphate, magnesium sulphate, calcium sulphate dihydrate (gypsum), and polyhalite (Polysulphate). In view of the large areas of high pH soils globally, this change of S fertilizer selection would make a significant contribution to decreasing NH₃ emissions worldwide, contributing to necessary cuts to meet agreed ceilings under the Gothenburg Convention.     

复合控释材料的控释性能、肥效及其成膜特性研究

膨润土和木素制成复合控释材料用于包膜控释肥。电镜扫描研究表明,复合材料包膜厚度明显比单用膨润土处理薄,且膜孔隙量少,粒间堆积较紧密。土柱淋溶试验表明,膨润土及其复合材料包膜尿素50 d的氮素累积溶出率远低于普通尿素,三种包膜尿素处理分别比普通尿素降低8.61、14.01、15.22个百分点。两种复合材料包膜处理氮素累积溶出量分别比单用膨润土包膜处理降低11.31%、13.83%。盆栽、大田小区试验表明,复合材料包膜尿素可明显提高作物产量及氮肥利用率。膨润土与木素复合用作控释材料在研制适合我国国情的农用控释肥方面是可行的。     

Use of polysulfone in controlled-release NPK fertilizer formulations

Encapsulation of fertilizers in polymeric coatings is a method used to reduce fertilizer losses and to minimize environmental pollution. Polysulfone was used for a coating preparation for soluble NPK granular fertilizer in controlled-release fertilizer formulations. The coatings were formed by the phase inversion technique (wet method). The influence of the polymer concentration in the film-forming solution on the physical properties of the coatings was examined. The coating structure controls the diffusion of the elements from the interior of the fertilizer granule. It was experimentally confirmed that the use of polysulfone as a coating for a soluble fertilizer decreases the release rate of components. Moreover, the release rate of nutrients from coated granules decreases with the decrease of the coating porosity. In the case of coating with 38.5% porosity, prepared from 13.5% polymer solution after 5 h of test, 100% of NH(4)(+) was released, whereas only 19.0% of NH(4)(+) was released after 5 h for the coating with 11% porosity. In addition, coating of fertilizers leads to improvement of handling properties, and the crushing strength of all coated fertilizers was an average 40% higher than that for uncoated NPK fertilizer.     

不同粒径生物炭包膜尿素缓释肥性能及缓释效果

为探究生物炭粉包膜处理对尿素缓释效果的影响,该研究以不同粒径稻壳生物炭粉为包膜材料,对尿素颗粒进行不同层数包膜处理,分别制备了3种生物炭包膜尿素缓释肥C_1(0.15 mm生物炭粉包膜)、C_2(内层0.15 mm,外层0.25 mm生物炭粉包膜)和C_3(内层0.15 mm,中层0.25 mm,外层0.425 mm生物炭粉包膜),并对生物炭包膜尿素缓释肥性能及缓释效果进行了分析研究。研究结果表明3种生物炭包膜缓释肥粒径主要分布在2.90～4.80 mm,随着包膜层数的增加,包膜缓释肥粒径随之增大,C_2和C_3粒径显著高于C_1(P0.05)。C_1、C_2和C_3的抗压强度为20.40～48.00 N,满足工业生产需求。与C_1和C_2相比,C_3颗粒表面较光滑,切面具有致密且孔隙结构丰富的层状结构,吸水倍率最小(1.69),耐水性也显著优于C_1与C_2(P0.05),氮元素缓释效果优于C_1与C_2。综上可以看出,3层包膜尿素缓释肥膜壳强度高于单层和双层包膜尿素缓释肥,通过控制不同膜层生物炭的孔隙结构和孔径,减缓水分的渗入及养分的流出过程,缓释效果突出,为生物炭包膜缓释肥的开发应用提供一个新技术路径。     

Dissolution kinetics of macronutrient fertilizers coated with manufactured zinc oxide nanoparticles

The solubility of Zn in Zn fertilizers plays an important role in the agronomic effectiveness of the fertilizer. On the basis of thermodynamics, zinc oxide (ZnO) nanoparticles (NPs) should dissolve faster and to a greater extent than bulk ZnO particles (equivalent spherical diameter >100 nm). These novel solubility features of ZnO NPs might be exploited to improve the efficiency of Zn fertilizers. In this study, we compared the Zn solubility and dissolution kinetics of ZnO nanoparticles and bulk ZnO particles coated onto two selected granular macronutrient fertilizers, urea and monoammonium phosphate (MAP). The main Zn species on coated MAP and urea granules were zinc ammonium phosphate and ZnO, respectively. Coated MAP granules showed greater Zn solubility and faster dissolution rates in sand columns compared to coated urea granules, which may be related to pH differences in the solution surrounding the fertilizer granules. The kinetics of Zn dissolution was not affected by the size of the ZnO particles applied for coating of either fertilizer type, possibly because solubility was controlled by formation of the same compounds irrespective of the size of the original ZnO particles used for coating.     

长期不同施肥条件下土壤微生物量及 土壤酶活性的季节变化特征

研究长期不同施肥条件下褐潮土微生物量碳（SMBC）、微生物量氮（SMBN）和土壤酶活性随季节的变化特征。结果表明,长期施肥条件下土壤SMBC、SMBN含量及土壤酶活性均表现出一定的季节变化。SMBC、SMBN含量在各施肥处理中的顺序为:化肥与猪厩肥配施处理（NPKM）化肥配施玉米秸秆处理（NPKS）单施化肥处理（NPK）不施肥处理（CK）,各处理之间差异显著(P0.05);施肥还显著提高了土壤脲酶、转化酶、碱性磷酸酶活性,有机无机配施的高于单施化肥的。除过氧化氢酶活性随季节变化显著下降外,SMBC、SMBN、酶活性的值一般在夏季（6月到8月）较高。通过双因素单变量方差分析表明,不同施肥制度与季节变化对SMBC、SMBN与酶活性的影响分别达极显著水平（P0.01）,不同施肥制度的SMBC、SMBN与酶活性的季节波动有极显著不同（P0.01）。     

Transmission and storage properties of a tropical loamy sand soil as influenced by organic-based and inorganic fertilizers

Short-term effect of organic and inorganic amendments on soil physical quality (SPQ) is marked when dealing with tropical soils which are naturally exposed to a high risk of water erosion. This study assessed the suitability of Tithonia diversifolia (Mexican Sunflower) when incorporated as green manure (GM) and also composted with poultry manure (PM) and other organic-based and inorganic fertilizers to improve some hydraulic properties of an Alfisol subject to excessive drainage. Treatments applied include fresh T. diversifolia (GM), PM, T. diversifolia composted with PM, organo-mineral fertilizers (OMF), neem fertilizer (NF), inorganic fertilizer (20-10-10 NPK), and control in a randomized complete block design and replicated four times. Soil samples were collected at 0–20 cm depth to determine near steady-state infiltration rates (I_s), sorptivity, transmissivity, saturated hydraulic conductivity (K_s), macroporosity (MacP), microporosity (MicP), air capacity (AC), and relative water capacity (RWC). The I_s rates were significantly (P ≤ 0.05) reduced to optimum range with the addition of the organic fertilizers over very high value (128.7 cm hr^?1) observed for control. Whereas, K_s was enhanced in the order: GM > compost (CP) > NF > inorganic fertilizer > control > organo-mineral fertilizer > PM. Sorptivity and transmissivity were highest in control and inorganic fertilizer plots, indicating that the addition of organic fertilizers lowered these parameters while MacP, MicP, AC, and RWC were generally increased with the addition of organic-based and inorganic fertilizers. Specifically, NF increased MicP by 34% over control. Values for RWC which were within the optimum range (0.60–0.70) were only obtained with NF (0.74), OMF (0.72), NPK (0.70), and GM (0.60). The SPQ parameters assessed in this study were enhanced by the addition of fresh T. diversifolia applied as GM and CP compared to other treatments. Therefore, T. diversifolia usually burned by farmers should instead be incorporated into the soil as manure.     

Nitrogen use efficiency with the application of controlled release fertilizers coated with Kraft pine lignin

The aim of the present paper is to assess the efficiency of several experimental fertilizers in a soil-plant system. The laboratory-prepared fertilizers consisted of granular urea coated with Kraft pine lignin. Five fertilizers were used with coatings differing in thickness and/or the addition of linseed oil as a sealing agent. The experiment was carried out in pots inside a glasshouse. The crop used was rye-grass. Results were compared with those from a urea control treatment without coating and a soil without fertilizer application.

The dry matter yield and the N uptake by the plant were higher in the treatments with coated controlled release fertilizers (CRF) than in those with uncoated urea. There was a lower nitrogen loss through leaching when using CRF (34 to 68%) was used than when using uncoated urea (over 74%) was used. The N use efficiency was lower for urea than for coated fertilizers. This index increased with the thickness of the coating and the addition of the sealing agent.     

CONTROLLED RELEASE OF FERTILIZER MICROCAPSULES USING ETHYLENE VINYL ACETATE POLYMER TO ENHANCE MICRONUTRIENT AND WATER USE EFFICIENCY

There have as yet been no detailed studies of micronutrient release from polymer coated fertilizers (PCFs). In this research, slow release microcapsules containing iron fertilizer was made and its release pattern evaluated. Three polymers ethyl cellulose (EC), glycerol mono stearate (GMS) and Compritol 888 ATO, were mixed with avicel and lactose and the microcaopsules were made by extrusion/spheronization method. The dissolution test carried out to determine the Fe release rate versus time. The results showed that, microcaopsules containing Compritol 888 ATO, released iron ions slower than that of EC and GMS. The release rate reached 85% after 7 days. In order to reduce the release rate, these microcaopsules were coated with ethylene vinyl acetate (EVA) polymer by dip coating method. It is concluded that the combination of matrix type formulation and the coating with EVA polymer caused a significant decrease in the release rate of iron.     

Corn biomass,uptake and fractionation of soil phosphorus in five soils amended with organic wastes as P fertilizers

Abstract

Sustainable food production includes mitigating environmental pollution and avoiding unnecessary use of non-renewable mineral phosphate resources. Efficient phosphorus (P) utilization from organic wastes is crucial for alternative P sources to be adopted as fertilizers. There must be predictable plant responses in terms of P uptake and plant growth. An 18-week pot experiment was conducted to assess corn (Zea mays L.) plant growth, P uptake, soil test P and P fractionation in response to application of organic P fertilizer versus inorganic P fertilizer in five soils. Fertilizers were applied at a single P rate using: mono-ammonium phosphate, anaerobically digested dairy manure, composted chicken manure, vegetable compost and a no-P control. Five soils used varied in soil texture and pH. Corn biomass and tissue P concentrations were different among P fertilizers in two soils (Warden and Quincy), with greater shoot biomass for composted chicken manure and higher tissue P concentration for MAP. Plant dry biomass ranged from highest to lowest with fertilizer treatment as follows: composted chicken manure?>?AD dairy?=?MAP?=?no-P control?=?vegetable compost. Soil test P was higher in soils with any P fertilizer treatment versus the no-P control. The loosely bound and soluble P (2.7?mg P kg^?1) accounted for the smallest pool of inorganic P fractions, followed by iron bound P (13.7?mg P kg^?1), aluminum bound P (43.4?mg P kg^?1) and reductant soluble P (67.9?mg P kg^?1) while calcium bound P (584.6?mg P kg^?1) represented the largest pool of inorganic P.     

基于水基反应成膜技术的聚合物包膜肥料的研制

以3种水基硅丙乳液(SD-528、SD-5281和GA-1710)为材料,利用水基反应成膜技术对这3种材料进行化学改性,制备了聚合物包膜肥料模型膜;研究了模型膜的养分扩散性能,在此基础上研制了水基聚合物包膜肥料;测定了包膜肥料养分释放曲线,并利用红外光声光谱对聚合物膜进行原位表征.结果表明,通过化学交联改性,硅丙基模型膜具有优良的成膜性和扩散性能,不同的乳液对包膜尿素的缓释效果影响显著;GA-1710和SD-528的缓释效果较好,在静态水中的释放时间可达到30 d,而SD-5281缓释性能较差,需要做进一步的化学改性;不同的乳液类型制备的包膜尿素的释放模式也不同,GA-1710累积释放曲线为"S"型,而SD-528为"L"型.因此,利用反应成膜技术,硅丙乳液在水基包膜肥料的研制中具有广阔的应用前景.     

聚合物包膜肥料硝态氮释放特征研究

采用不同养分组成(单一组分和复合组分)聚合物包膜肥料(Multicote)和水中静态溶出的方法,研究了不同温度和半径处理下聚合物包膜肥料NO3-N释放特征.结果表明,温度升高显著促进NO3-N的释放;肥料颗粒半径差异显著影响NO3-N释放,小半径的肥料颗粒NO3-N释放明显比大半径颗粒快,且小半径肥料颗粒NO3-N释放的活化能较低;肥料颗粒内离子间存在明显的交互作用,与单一组分聚合物包膜肥料相比,复合组分聚合物包膜肥料NO3-N释放的线性期明显缩短,NO3-N释放速率增加,且NO3-N释放的活化能明显增大.聚合物包膜肥料中NO3-N的释放特征直接与聚合物膜的扩散系数、扩散面积、膜厚度以及伴随离子的种类和浓度相关.养分释放时期以及活化能的定量化表征为全面评估聚合物包膜肥料养分释放特征提供了参考.     

丙烯酸树脂包膜尿素肥料研制及其控释效果

采用丙烯酸树脂为包膜材料,以NBPT（N-丁基硫代磷酰三胺）和DCD（双氰胺）为生化抑制剂,利用流化床对尿素进行涂层生化抑制剂及包膜,制备4种包膜肥料,对这些包膜肥料在水中的控释效果进行了研究。结果表明,采用此技术制备的包膜肥料,表面成膜完整,包膜物质在成膜时分布均匀、与尿素肥心接合紧密,表面光滑。NBPT和DCD与肥心结合严密,包膜层紧覆于抑制剂的外表。包膜可有效控制尿素的溶出,在水中的控释时间为19～30d。初期溶出率远远小于15％,微分溶出率基本上在0．25％～2．5％之间;在水中尿素累积溶出特征符合一元二次方程模型,尿素释放曲线呈“S”形。