不同浸提条件对包膜控/缓释肥水中溶出率的影响

以几种不同包膜材料控／缓释肥为供试肥料,研究不同肥(养分)水比、浸提方式(连续浸提和更换浸提液)、温度和pH条件对控／缓释肥水中溶出率的影响。结果表明,浸提液中肥料浓度是影响养分释放的重要因素,加大肥水比、更换浸提液可以显著减小这种影响。升高温度,有机和无机材料包膜控／缓释肥水中溶出率均显著加快。肥料类型、肥水比对浸提液的pH都有显著影响,但在连续浸提和更换浸提液方式下,7d内浸提液的pH有着不同的变化趋势。控／缓释肥在pH.5的磷酸盐缓冲液中的溶出率显著高于在pH.7的磷酸盐缓冲液中的溶出率。因此,对于不同包膜材料控／缓释肥以一定pH值的微酸性缓冲溶液作为浸提剂,定期更换浸提液或采用动态流法,相同的氮(或磷、钾)水比,30℃左右的浸提条件是较为合理的。     

包膜尿素养分释放特性测定方法的研究

分别以水、砂子、热硼酸溶液为介质,研究不同浸提方式对缓/控释肥养分溶出率的影响及两种缓/控释肥料的溶出特征。结果表明,同一种肥料在不同的介质中溶出率趋势无显著差异,以热硼酸溶液为介质,可提高检验速度,是检验长释放期控/缓释肥料产品质量的有效方法。     

不同土壤淋洗方式下有机—无机复合材料胶结包膜肥料钾素溶出速率比较

应用由水基成膜法研制的4种有机-无机复合材料胶结包膜肥料(B2、PS、F2、F2F)进行土柱淋洗试验,研究其在不同土壤类型条件下的钾素溶出规律。结果表明:4种胶结包膜肥料在48d内钾素累积溶出率为44.02%(红壤)>34.59%(褐土)>25.92%(黑土)。同一种胶结包膜肥料在红壤、褐土和黑土中的钾素瞬时溶出率峰值出现时间一致(以B2为例);钾素溶出峰值之前,瞬时溶出率在2~13 d内为红壤>褐土>黑土,钾素峰值溶出率为10.39%(红壤)>7.09%(褐土)>5.99%(黑土),而峰值过后,三土壤间瞬时溶出率差异不显著(P>0.05)。说明包膜肥料本身释放钾素的速率受不同质地的土壤影响较小,但其淋出量受土壤影响较大。     

肥料袋控缓释对桃树土壤酶活性及植株生长的影响

为探明袋控缓释肥对土壤酶活性的影响,以一年生‘夏红/毛桃’(Amygdalus persica Linn.)为试材,研究了沟施普通肥料和袋控缓释肥对盆栽桃树土壤酶活性、养分状况及植株生长的影响。结果表明:各施肥处理显著提高了土壤中蔗糖酶、脲酶、酸性磷酸酶、蛋白酶和过化氢氧酶活性;桃树生长前期袋控缓释处理土壤酶活性低于普通肥料处理,中后期袋控缓释处理土壤酶活性显著高于普通肥料处理。不同施肥处理提高了土壤养分含量,桃树生长前期,袋控缓释肥处理土壤有效养分低于普通肥料,但中后期始终高于普通肥料;可见袋控缓释肥处理可以在桃树整个生长季提供稳定的养分供应,维持较高的有效养分含量。土壤酶活性与土壤肥力之间有很好的相关性,其中土壤蔗糖酶、蛋白酶、酸性磷酸酶、过氧化氢酶、脲酶活性均与碱解氮含量呈显著正相关;过氧化氢酶、蔗糖酶活性与速效磷含量呈显著正相关;过氧化氢酶活性与速效钾含量呈显著正相关。不同施肥处理提高了桃树叶片中全氮、全磷和全钾的含量,袋控缓释处理效果优于普通肥料处理。袋控缓释处理桃树叶片叶绿素含量和净光合速率显著高于普通肥料和对照。袋控缓释肥处理桃树新梢生长量低于普通肥料处理,但干周粗度高于普通肥料处理,袋控缓释肥处理桃树生长健壮。不同施用量处理均以60g/棵效果较好。可见,袋控缓释肥处理能够保证养分的稳定供应,有效提高土壤酶活性,利于植株生长发育,且以60g/棵的施肥量效果较好。     

淀粉-聚乙烯醇包膜复合肥的评价方法研究

以淀粉和聚乙烯醇(PVA)为主要原料制备膜材料并包膜颗粒复合肥,通过膜吸水性和肥料抗压碎力试验筛选适合的原料比例制备不同粒径的供试肥料。采用水中溶出率与土壤培养两种测试方法研究了其氮素养分的释放规律,并对两种方法的测定结果进行了比较、分析与评价。结果表明:淀粉与PVA比例合适就会提高膜材料的耐水性和包膜肥料的抗压碎力。超过最佳配比量后的淀粉要比同质量PVA更耐水、更能提高肥料的抗压碎力。自制包膜处理土壤培养法中养分释放率普遍是水溶法中的1/3~1/4,这与介质环境和试验方法的差异有关。调节好淀粉与PVA用量比例或增加膜厚度会使养分释放更趋近于Logistic植物营养生长曲线,同时也使得水、土两介质中测定结果的相关性更好。受多种因素影响,用水溶法现有的一些指标评价包膜肥缓释性能带来误差较大,缓释肥料在水溶法中的释放规律不能真实的反映出其在土壤中的释放性能,对用淀粉、聚乙烯醇这类亲水材料包膜的肥料而言更是如此。     

醋酸酯淀粉及与抑制剂结合包膜尿素在棕壤中尿素溶出特征

在室内恒温培养条件下,以普通大颗粒尿素为对照,研究4种醋酸酯淀粉(SA)包膜及与生化抑制剂结合尿素肥料在草甸棕壤中尿素态氮溶出特征,以确定不同种SA包膜尿素在土壤中缓/控释效果及释放特征。研究表明,4种SA包膜尿素在土壤中尿素累积溶出量在28 d后达到最大值,接近100%,SA+UTRA、SA+DCD+UTRA、SA+NBPT+UTRA和SA+DCD+NBPT+UREA分别在12、16、12和16 d养分累积溶出量超过80%,是水中释放期的2倍左右,SA+UREA时段平均溶出率最高峰值出现在0～4 d,达到9.11%d-1,另3种包膜肥料均出现在5～8 d,为8.57%d-1～9.97%d-1。SA与DCD或NBPT结合包膜尿素对控制尿素释放作用效果十分显著,SA与DCD及NBPT结合型包膜尿素肥料对抑制尿素释放作用最强。     

包膜控释肥养分释放特性评价方法的研究进展

控释肥已成为国内外肥料研究的热点 ,但是评价控释肥养分释放特性的方法研究相对滞后 ,至今没有较为完善的方法和统一的测试标准。本文综述了包膜控释肥养分释放特性的现有评价方法 :水中 (或溶液 )溶出率法、土壤溶出率法、扩散率法、渗透率法、电超滤法和同位素示踪法等 ;评述了各种方法的优缺点及改进途径 ;并展望了今后评价方法的研究方向     

用缓释指数评价化学缓释肥的缓释特性及其生物效应

在实验室条件下,采用简化的工艺制备了对氮、磷、钾三元素均有部分缓释作用的复混肥(化学缓释肥),用特定淋洗装置测定肥料各养分随时间的溶出率,通过双曲线方程Xt=b-a/t对其养分累计溶出率与时间的关系进行拟合,以方程常数b和a计算出的缓释指数(SR I)来定量评价肥料缓释特性,同时进行盆栽试验,探讨了缓释指数与复混肥中相应缓释添加剂百分含量(X)之间、各复混肥处理的油菜产量与复混肥中缓释添加剂总含量(X')之间的关系。结果表明:各养分的缓释指数(SR I)与相应缓释添加剂含量(X)均有很好的线性正相关;各化学缓释肥处理的油菜产量随缓释添加剂总含量(X')增加而增加;化学缓释肥以较少的荚数获得更高的产量。这预示着通过肥料的室内淋洗试验得到的缓释指数SR I不仅可以用来评价肥料的缓释性能,且在一定程度上可预测肥料的增产效应。     

袋控缓释肥对日光温室番茄生长发育及土壤氮素淋失的影响

采用田间小区试验法研究袋控缓释肥对设施番茄生长发育和土壤氮素淋失的影响,对不同施肥方式下番茄关键生育阶段番茄生长指标和土壤氮素淋失进行比较。结果表明:袋控缓释肥施肥处理(BCRF)与传统施肥处理(TF)相比在株高、茎粗、叶片数和叶绿素等生长指标方面没有显著差异,等量袋控缓释肥处理(BCRF1)植株生长优于传统施肥处理,半量袋控缓释肥处理(BCRF2)施肥量减半后仍能保持良好长势。番茄根系45%以上都分布在0—15cm土层中,30—45cm土层在17%以下。BCRF处理根系长度、表面积和体积方面明显优于TF处理,BCRF1和BCRF2之间差异不显著。BCRF处理显著提高番茄生长后期根系活力,并一直维持在较高水平上,TF处理根系活力在取样期间下降30%。从产量上看,BCRF1处理最高,达72.1t/hm2,BCRF2处理其次,达67.8t/hm2,TF处理为66.5t/hm2,CK处理最低为46.1t/hm2,BCRF1、BCRF2和TF差异不显著。BCRF处理明显降低0—20cm和20—40cm土层硝态氮浓度,BCRF1和BCRF2之间差异很小。40—60cm土层和60—100cm土层中硝态氮浓度TF处理分别从146.7μg/g上升到164.3μg/g和84.2μg/g上升到96.8μg/g,BCRF处理变化很小,明显降低了硝态氮的渗漏。BCRF处理,0—20cm和20—40cm土层铵态氮浓度显著高于TF处理,0—20cm土层土壤溶液铵态氮浓度可达46.5μg/g以上,是TF处理2倍多。     

淋洗法测试肥料氮素释放性能研究

分别采用水浸泡法、间歇淋洗法和连续淋洗法测试肥料氮素释放性能,考察了不同模拟土壤介质的淋洗结果,并从介质饱和含水率、水分张力和阳离子交换量等方面综合分析了模拟土壤效果。实验表明:水浸泡法与无介质连续淋洗法结果具有良好的相关性,都符合y=ax+b释放模型;相同介质间歇淋洗法和连续淋洗法结果具有良好的相关性,都符合N=N0/[1+exp(A-kt)]释放模型;蛭石+土壤(体积比1∶1)能更好地模拟土壤性能。模拟土壤连续淋洗法可用于肥料生产企业在线检测。     

几种包膜缓控释肥粒养分释放特征的研究

采用水浸泡法对国内外4种包膜控释肥料的养分释放特性进行了系统的研究。结果表明,4种缓控释肥料的初期溶出率均小于12%,微分溶出率在0.4%～1.5%之间,这符合国际上公认的缓/控释肥的评价标准,初期溶出率小于15%、微分溶出率在0.25%～2.5%之间。采用水浸泡法测定包膜控释肥料养分释放特征,简便快速,检测时间短,重复次数少,养分浓度变化直接反映出包膜控释肥料的释放速率特性,还可以定量的测定其供肥性能,控释肥料有控制养分释放、延长供应时间的作用;其中腐殖酸和炭基有利于提高肥料颗粒的水稳定性,减缓养分的释放速率。     

控释肥在基质栽培中的养分淋溶及其对基质理化性质的影响

无土栽培是设施农业中广泛采用的先进技术,能有效克服土壤连作障碍,具有省水、省肥、省工等土壤栽培难以比拟的优势,控释肥在基质栽培中的应用,使无土栽培技术的发展前景更加广阔。本文通过无土栽培试验,研究了控释复合肥在基质中的养分变化规律及其对基质理化性质的影响。研究结果表明,控释肥氮、磷、钾、铁和锌的释放规律基本一致,且养分的控制释放减少了养分流失,降低了基质中的盐分浓度,与普通速效肥相比更具有安全性;控释肥明显改变了基质的容重、孔隙度,改善了基质的水气状况,从而为作物的生长提供了良好的生长环境。     

保水包膜尿素肥料理化特征

保水肥料是缓/控释肥料剂一个新的发展方向。本文中作者对研发的一种保水缓释包膜尿素肥料的包膜物理化学特征,养分缓释机制进行了研究。电镜观察显示,保水材料包膜上存在网状孔隙,膜厚度0.12mm~0.30mm,是水分贮存的物理空间。红外光谱分析表明,保水材料与尿素表面存在着氢键作用,这种氢键作用使保水包膜材料对尿素有一定吸附作用,这是保水包膜尿素具有养分缓释的一种机制。吸水倍率测定表明,保水包膜材料吸水倍率在70倍以上,吸水达饱和的时间为1.4小时,在盐水中还有一定的吸水倍率,pH为6.87。因此,保水包膜尿素肥料是水肥复合一体化的缓释肥料。     

保水剂包膜尿素的特征与性能

保水肥料是缓/控释肥料研究的新方向,本文利用聚合化学反应制备出了一种保水剂包膜尿素肥料,并对该肥料的包膜特征、养分控释性能及其对土壤水分的影响进行了研究。结果表明:保水剂包膜尿素的实际包膜量低于设计包膜量,一般低10%～12%。扫描电镜成像图显示:保水剂包膜尿素包膜上存在纤维网状孔隙,膜厚度为0.15～0.25mm。7d水溶出率的实验结果表明,保水剂包膜尿素养分控释效果低于塑料包膜尿素,保水剂包膜尿素的养分缓释作用主要来自包膜对尿素的吸附作用。保水剂包膜尿素处理土壤的土壤水分脱水曲线测定结果说明,保水剂包膜尿素可提高土壤水分含量,增加土壤水分的有效性,改善土壤的保水、释水性能。因此,保水剂包膜尿素肥料是具有开发应用前景的新型缓/控释肥料。     

A column perfusion test to assess the kinetics of nutrient release by soluble,sparingly soluble and coated granular fertilizers

In recent years, innovations in fertilizer research have principally been in the design of products to supply more timely plant nutrients and mitigate detrimental losses to the environment. In the development of these fertilizers, a laboratory method to comparatively screen a large number of formulations for the rate of nutrient release is a critical first step in formulation optimization to significantly reduce time spent on pot and field trials, reducing costs considerably. Currently, given the absence of a standard laboratory method for all fertilizers, adaptions of a method for coated fertilizers from the International Organization for Standardization (2017) ISO 21263 and other column tests are being used which are often complex and/or require manual sampling which can be laborious, time consuming and costly. The method presented here evaluates the dynamic release in real time by continuously perfusing samples in columns utilizing an automated sample accumulation system for short‐term and long‐term release studies and eliminates the need for soil/sand packing of columns. Mass balance is accounted for by analysing the residue after dissolution and the amount released is expressed as a % of the total nutrient content in the product. This method is reliable, uncomplicated and cost‐effective and has been used to test uncoated soluble fertilizers, nanofertilizers, fertilizers with newly developed coating technologies and other slowly soluble fertilizers, to assess the effect of variables like coating chemistry and thickness, fertilizer composition or fertilizer particle size on release rate.     

Nitrogen Recovery and Transformation from a Surface or Sub-Surface Application of Controlled-Release Fertilizer on a Sandy Soil

ABSTRACT

Controlled-release fertilizers (CRF) are used to reduce leaching of nutrients, especially nitrate-nitrogen (NO₃ ^?-N) to groundwater, caused mainly by application of soluble N fertilizers to sandy soils in Florida. A leaching column study was conducted to evaluate N release and transformation from a CRF (CitriBlen) over a 16-week period when it was applied on the soil surface or incorporated into the soil. When one pore volume of water was applied to column weekly or biweekly, the CRF released urea-N slowly over time with three peaks of release on 3–4, 8, and 12 week after application. Both ammonium-nitrogen (NH₄ ⁺-N) and NO₃ ^?-N were leached in large amounts on week 2, likely from soluble forms of N. Cumulatively, the most leached N at the end of study was in the NH₄ ⁺ form, followed by the NO₃ ^? form. The sum of all N forms leached and volatilized accounted for 53–69% of total N applied. Total N recovery was 70% and 93% of total N applied for surface and sub-surface application of the fertilizer, respectively. It was indicated that the better recovery rate found with sub-surface application may have been due to minimized N loss by volatilization. Sub-surface application of fertilizer resulted in more than three times NH₄ ⁺-N remained in soil, compared with surface application. On average for both application treatments throughout 16-week period, 5.8 h was required for ammonification and 4.7 d for nitrification to occur after N release from the fertilizer. Characterization of CRFs for specific soil type, leaching volume and cycle, and application manner as well as knowledge of N requirement of the crop will allow for the Best Management Practices of these fertilizers, thus obtaining optimum yields and minimizing nutrient losses from CRFs.     

Materials for sustained and controlled release of nutrients and molecules to support plant growth

Controlled release fertilizers (CRFs) are a branch of materials that are designed to improve the soil release kinetics of chemical fertilizers to address problems stemming losses from runoff or other factors. Current CRFs are used but only in a limited market due to relatively high costs and doubts about their abilities to result in higher yields and increased profitability for agricultural businesses. New technologies are emerging that promise to improve the efficacy of CRFs to add additional functionality and reduce cost to make CRFs a more viable alternative to traditional chemical fertilizer treatment. CRFs that offer ways of reducing air and water pollution from fertilizer treatments, improving the ability of plants to access required nutrients, improving water retention to increase drought resistance, and reducing the amount of fertilizer needed to provide maximum crop yields are under development. A wide variety of different strategies are being considered to tackle this problem, and each approach offers different advantages and drawbacks. Agricultural industries will soon be forced to move toward more efficient and sustainable practices to respond to increasing fertilizer cost and desire for sustainable growing practices. CRFs have the potential to solve many problems in agriculture and help enable this shift while maintaining profitability.