草莓干冰喷射速冻过程的数值模拟与优化

为了有效提高速冻后草莓的品质,该研究提出干冰喷射速冻草莓的方法,设计了干冰喷射速冻草莓的速冻间和干冰喷射装置,利用Comsol软件对速冻间内干冰喷射草莓速冻过程的温度场、速度场和压力场进行模拟,研究了不同干冰喷入速度(0.10、0.15、0.20、0.25、0.30、0.40、0.50m/s),喷入口半径(18、20、23、25、30mm),以及干冰喷入速度为0.20、0.30 m/s时模型内干冰体积分数变化对草莓速冻效果的影响。结果表明:随着干冰入口半径的增加和干冰喷入速度的提高,草莓会更快的冻结。在入口半径为25 mm,流速为0.30 m/s情况下,可以高效实现草莓速冻。对干冰速冻草莓降温性能进行分析,并与现有液氮喷淋速冻草莓降温性能进行比较,结果表明:干冰速冻草莓通过最大冰晶带和草莓完全冻结的时间分别减少63.9%和41.7%,草莓能最大限度地保持原有的新鲜状态和营养成分。对优化的结果进行试验验证,草莓表面温度和中心温度达到标准时误差分别为3.70%和6.03%,草莓干冰速冻前后的品质指标均优于草莓速冻标准。研究结果为进一步开发节能环保的干冰速冻草莓装置提供参考。     

冲击式速冻设备上下送风速度对虾仁冻结过程的影响

随着人们对速冻食品品质的要求不断提高,商家对食品速冻技术的要求也在不断提高,冲击式速冻技术作为目前先进的速冻技术之一成为研究热点。但由于其高速射流冲击导致的内部换热区流场的不均匀会造成设备换热效率差,能效比低等问题。为找到使得设备换热区流场最优的送风速度,该文以明虾虾仁为研究对象,利用数值模拟结合试验验证的方法研究了冲击式速冻设备中上下送风速度对虾仁冻结过程的影响,分为上下两侧风速保持一致且同时改变;上侧送风速度为15 m/s、下侧为0~15 m/s;以及下侧送风速度为15 m/s、上侧为0~15 m/s 3个试验组进行研究。研究结果为:当冲击式速冻设备两侧送风速度保持一致时,随着风速的增大,虾仁冻结时长缩短但减小幅度也会不断减小;当上下两侧送风速度大小相差悬殊时,两股冲击射流相对冲击会在低速侧形成促进虾仁表面流场流动的涡流,提高换热效率,减小虾仁冻结时长;当上下两侧送风速度大小相差不大时,两股冲击射流相对冲击会在虾仁表面形成流速较低的射流"真空区",降低虾仁换热效率,增大虾仁冻结时长;在试验的两侧送风速度范围内,当上侧送风速度为15 m/s,下侧送风速度为2 m/s时,虾仁对流换热强度最大,冻结时长最短。     

深松铲叶脉状内通道分支出口流速影响因素分析与试验

针对叶脉状内通道深松铲内部结构的液体流速变化会影响深松铲的自润减阻与改良液层施的效果的问题，该研究采用基于计算流体动力学的仿真分析并结合物理试验，研究了结构参数（内通道孔径、孔间距、孔数）和工作参数（主通道入口流速）对分支出口液体出流速度的影响。首先利用仿真方法开展单因素试验，优选出试验因素的水平范围值，其次开展Box-Behnken试验，以各分支出口液体出流速度最大值为目标值，对叶脉状内通道多分支出口管的结构参数和工作参数进行优化取值，建立各影响因素与分支出口流速之间的二阶回归模型，并对模型进行优化求解，进而得到最优参数组合为：内通道分支出口孔径为6 mm、孔间距为110 mm、孔数为4、主通道入口流速为7 m/s。在此工况下，内通道分支出口平均流速为3.264 m/s。按最优参数组合条件对叶脉状内通道进行设计加工并进行相应的物理试验，试验结果为内通道分支出口平均流速2.971 m/s，与仿真结果的误差为8.97 %。由此，检验了叶脉状内通道结构优化设计的效果，同时为具有自润减阻与改良液层施的深松铲叶脉状内通道结构的优化设计提供一定的理论基础。     

航空植保作业用喷头在风洞和飞行条件下的雾滴粒径分布

为了获得GP-81A系列航空喷头的雾滴粒径分布情况,该文针对GP-81A系列航空喷头进行了风洞条件和飞行条件下的雾滴粒径及分布测试,通过高速风洞测试系统模拟飞行时产生的高速气流开展了气流大小对雾滴粒径及分布的影响研究;基于农用航空常用的Y5B飞机开展了不同型号喷嘴航空喷雾时的雾滴粒径及分布研究;同时,比较了相近喷雾压力条件下,相同喷嘴在风洞条件和飞行条件下的雾滴粒径及分布差距。试验结果表明,风洞条件测试时,当风速小于33.8 m/s时,雾滴粒径随气流的增加而增大;而当风速大于33.8 m/s时,雾滴粒径随气流的增加而减小,足够大的气流可以使雾滴进一步雾化。当气流在33.8 m/s时,7#喷嘴雾滴粒径最大,为491.1μm;当气流在84.87 m/s时,2#喷嘴雾滴粒径最小,为202.1μm。该系列喷头的6种不同喷孔的喷头的雾滴粒径均大于150μm,说明该喷头航空喷雾时的飘移损失较小。在喷雾压力基本相同的条件下,风洞条件下的雾滴粒径测试结果略高于飞行试验结果,主要原因是距离喷头出口的测试位置不同。风洞条件和飞行条件下的雾滴谱相对宽度S值均较小,表明雾滴分布较均匀,而飞行条件下的雾滴分布更均匀些。该研究为进一步优化航空喷头的作业参数,开展减少雾滴飘移研究提供参考。     

喷嘴结构对气流冲击式速冻机钢带表面换热特性的影响

为了改善现有速冻机存在的效率低、能耗大等问题,该文对比了2种速冻机的喷嘴结构,以期找到提高设备内部换热强度和均匀性的最佳结构。由于速冻机模型较为复杂,为了简化试验模型,本文以冲击式速冻试验台为依托,在验证所建立模型的可靠性的基础上,利用计算流体力学(computational fluid dynamics,CFD)数值模拟分析比较了气流冲击式速冻机2种喷嘴的换热性能。从钢带表面Nu分布和传热均匀性2个角度出发,分析了不同喷嘴到钢带表面距离与出口直径的比值(H/DE)下圆孔和圆漏斗喷嘴结构的钢带表面换热特性。结果表明,当H/DE值在2~12时,圆漏斗喷嘴结构的钢带表面Nu比圆孔喷嘴结构的Nu高5.41%~15.10%。2种喷嘴结构的钢带表面Nu变化受H/DE值影响较大,受横流影响较小。圆漏斗喷嘴结构的钢带表面传热均匀性指标η值比圆孔喷嘴结构的η值低7.06%~34.52%,圆漏斗喷嘴结构的钢带表面传热更均匀。对比2种喷嘴结构,在冷却空气入口处质量流量相同情况下,圆漏斗喷嘴结构的钢带表面能得到更高的Nu值和传热均匀度,更有利于减少食品的冻结时间,提高速冻机产能以及食品的冻结品质。     

高压二氧化碳技术速冻双孢菇工艺优化

为解决果蔬速冻加工产品冻结时间长、易发生干耗的问题,该研究采用了高压二氧化碳技术（high pressure carbon dioxide,HPCD）对双孢菇进行了速冻。原料在热烫钝酶的基础上,通过单因素试验和正交试验,结合速冻产品感官评价试验对速冻工艺参数进行了优化。结果表明：HPCD速冻双孢菇最佳工艺参数为处理釜初温6℃、处理釜设定压力7 MPa、卸压时间4 min,且卸压时间为影响速冻产品品质最显著因素。HPCD速冻技术具有良好的工业化前景。     

气液两相流流型影响喷嘴喷雾形态及液滴粒径分布

为了获得气泡雾化喷嘴内不同气液两相流流型对喷雾形态及液滴粒径分布的影响规律,该文建立了气泡雾化喷雾可视化试验系统,采用试验方法获得喷嘴内气液两相流流型及宏观喷雾形态;该文建立了喷嘴内和喷雾场中气液流动模型。研究结果表明,泡状流时喷孔出口含气率呈周期振荡衰减且含气率较低,搅拌流时喷孔出口截面含气率脉动幅度及其变化较小且含气率较高(较泡状流高1倍);搅拌流时喷雾形态脉动不明显,喷雾半锥角分布比较集中,而泡状流时正好相反,搅拌流时喷雾半锥角在8°~14°范围内的占比超过70%,而泡状流不到40%。搅拌流时喷孔出口附近液滴粒径分布更加集中且随轴向距离增加分布范围变化更大,液滴平均粒径比泡状流小4%左右;在喷孔出口附近,搅拌流时液滴粒径标准差明显小于泡状流时液滴粒径标准差,较泡状流小30%以上;不同气液两相流流型时液滴粒径分布的差异随轴向距离的增加而减小。研究结果可为气泡雾化喷射技术的发展以及不同领域喷嘴内流型的合理选择提供一定的理论和试验依据。     

不同冻结速率对脆肉鲩鱼片冻结特性的影响研究

为了研究不同冻结速率对鱼片冻结品质的影响程度、产生原因及其机理,该文以脆肉鲩鱼片为对象,研究了4种不同冻结速率(3.69、2.64、0.60、0.34 cm/h)对鱼片冻结曲线及其品质(理化特性和质构特性)的影响.试验结果表明,脆肉鲩鱼片的冻结点为(-0.6±0.1)℃;随着冻结速率的增加,汁液流失率减少,盐溶蛋白含量的降低率以及Ca2 -ATPase活性的损失率都有不同程度的降低,但冻结过程提高风速则导致干耗增加;与新鲜鱼片相比,速冻样解冻后硬度与耐咀性无变化,而慢冻样解冻后硬度与耐咀性却有所下降;4种冻结速率下解冻样的回复性均有不同程度的下降.综合理化指标和质构特性的检测结果,在注意减少干耗影响的前提下,提高冻结速率有利于保持脆肉鲩鱼片的品质.     

高温射流冲击苎麻开纤脱胶的压力和温度场数值模拟与试验

为了研究苎麻纤维残留胶质的射流冲击分纤脱胶机理,设计试制了高温射流冲洗试验装置,开展了单喷嘴和双喷嘴开纤脱胶试验,数值模拟了单喷嘴和双喷嘴射流冲击壁面的表面温度场、压力场分布及有效的作用区域。结果表明,当喷嘴直径为2.0 mm,进口温度为373 K时,单喷嘴射流冲击试验的较佳组合参数喷距为30 mm,进口压强为1.2 MPa,时间为16 min,测得残胶率为3.1%;以单喷嘴相同设定参数模拟了双喷嘴较佳喷嘴间距为30 mm,冲击压力范围为0.2~0.3 MPa,温度范围为320~334 K,该试验测试的喷嘴间距与数值模拟相符合,测试残胶率为3.1%,单纤维断裂强力为51.71 c N。该技术为开发新型苎麻纤维分纤洗脱设备提供技术参数。     

液氮冷媒介质对速冻饺子冻裂率的影响

研究饺子新型冻结技术,探索液氮速冻工艺对调理食品品质的作用规律。该文以饺子为研究对象,和面水面质量比、皮馅质量比、面粉品质、馅料配比、产品规格、冻结时间、冻结方式、冻结介质等诸多因素对饺子冻裂率都有重要影响。该试验以猪肉、香菇、大豆组织蛋白为饺子馅主要原料,研究了和面时的水面质量比、面团的静置时间、皮馅比、饺子在液氮池中的沉浸时间对饺子冻裂率的影响。结果表明:以上四因素对饺子的冻裂率都有不同程度的影响。和面水面质量比为56∶100、面团静置时间在10 min、皮馅质量比在1∶1.3、液氮池沉浸时间为40 s,制作好的饺子在立即速冻后的冻裂率为37%,感官评定得分为77.6。该研究为液氮沉浸速冻工艺在调理食品的应用提供了一定的理论参考。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.