Ten winter wheat (Triticum aestivum L.) lines selected from the 1982 International Winter Wheat Mildew and Rust Nurseries were studied to characterize gene number and mode of inheritance of powdery mildew resistance. Two experiments were conducted: 1) each of the lines was crossed to the susceptible cultivar Chancellor, which lacks any known’ gene _ for resistance, and seedlings of the parental lines, F₁, F₂, BC₁ (Chancellor X F₁), and F₃ populations were inoculated with isolate 127 of Blumeria graminis (DC.) E. 0. Speer f. sp. tritici Em. Marchal in the greenhouse and evaluated for powdery mildew reaction; 2) the ten lines were crossed with each other and to each of 13 host differential lines with known genes for powdery mildew resistance, and 300 to 800 F₂ seedlings from each cross were evaluated. All parents were resistant (Infection Type = 1-3), except for ST1-25, which had an intermediate (IT = 4-5) reaction type. Genetic analyses of crosses revealed that the resistance in C39 and SI5 is conferred by three dominant genes (Pm2, 4b, and 6), and resistance in A55-2, R107, and Bulk PV63-6 is governed by one partially dominant gene (Pm4b). Results from F₂, F₃, and BC₁ populations derived from crosses between ‘Armada’ and Chancellor, were inconsistent, but indicated that Armada has at least one dominant gene for resistance, which likely is Pm4b as suggested by others. The resistance gene in OK75R3645 most likely is an allele at the Pm3 locus, and it is probable that the resistance gene in GO4779 is Pm1. Single recessive genes were identified in VPM1 (Pm4b) and ST1-25 (Pm8). / Ph. D.

The Midwestern United States is a nationally and globally important producer of agricultural products and uses intensive practices to achieve high grain yields. However, intensive agriculture is a major contributor of nitrogen and phosphorus export to the Mississippi River and the hypoxic zone in the Gulf of Mexico. Cover cropping is a recommended conservation practice for providing soil cover throughout the winter and taking up nutrients that may otherwise be lost in bare fallow systems, but the associated costs limit widespread adoption of this practice. Double cropping, which involves growing two crops in one year, is functionally similar to cover cropping and can be harvested for an additional income, but the water quality impacts of applying fertilizer to maximize yields and the systemic impacts of intensification with another crop on corn-soybean rotations are not well understood. This two-year, plot scale study in Carbondale, Illinois was designed to assess nutrient leaching, referring to nitrate-N, ammonium-N, and dissolved reactive phosphorus (DRP), nutrient availability, and crop yields when using bare fallow, cereal rye (Secale cereale) cover crops, or winter wheat (Triticum aestivum) double crops with varying nitrogen fertilizer rates and timings in the winter seasons of corn-soybean rotations. Four blocks with randomly assigned treatments comprised of two treatment factors were used. These treatment factors included rotations with either bare fallow or cover crops in alternate winters and winter wheat fertilizer management intensity with a high fertilizer treatment level, grower recommended rates applied at planting, tillering, and jointing, a medium fertilizer treatment level, grower recommended rates applied at tillering and jointing, a low fertilizer treatment level, with reduced nitrogen rates applied at tillering and jointing, and a no fertilizer treatment level, which was used as either corn-soybean or corn-cover crop-soybean-cover crop control. Additional nutrient inputs from fertilizers in the winter wheat seasons did not significantly increase nitrate-N, ammonium-N, or DRP leaching in the 2021-2022 winter wheat sampling season and nitrate-N and ammonium-N leaching was significantly less in some or all the winter wheat plots compared to the control plots. Winter wheat yields and nitrogen uptake in 2022 were significantly greater in medium fertilizer plots while yield-based nitrogen leaching and partial nitrogen balances were significantly greater in high fertilizer treatments, indicating that delayed fertilization in winter wheat can improve nitrogen use efficiency and yields. Soybean yields were significantly greater in plots without winter wheat due to a longer growing season, but plant available ammonium-N concentrations, which were greater in winter wheat plots, also had a significant negative relationship with soybean yields, indicating that this may have impeded biological nitrogen fixation. Using cover crops in alternate winters reduced nitrate-N leaching by 106% and plant available nitrate-N concentrations by 107% in the season as well as the subsequent corn season by 66% and 90%, respectively, compared to the bare fallow plots, and the decreased plant available nitrate-N concentrations in cover crop plots caused a 6% yield penalty in the corn harvest. Despite yield penalties to cash crops from winter crops, the use of double crops was the only factor that significantly impacted total crop yields. The use of cover crops in alternate winters was the most significant factor in nutrient leaching, demonstrating that these practices can be used to increase total crop yields without contributing significantly to nutrient export. For farmers concerned with the costs of cover cropping, double cropping is a practice that can provide some of the same ecosystem services while also providing an additional financial incentive.

Crop yields are expected to face more threatening circumstances due to ongoing climatic and environmental change. The continued sustainability of crop production will depend on genetic capacity of crops to adapt to increased biotic and abiotic barriers induced by climate change. Historically, shoot-based traits were breeding targets for overcoming yield gaps between developed and undeveloped nations. However, the rate of genetic gain has stabilized with conventional breeding targets for indirect yield improvement. As the availability of mineral fertilizers is steadily declining and the occurrence of low-fertility soils has increased, reoccurring yield disparities worldwide are propelling us to evaluate new breeding targets. There is potential for plant breeders to shift their focus to the root system architecture (RSA) as a new target for indirect selection, enabled by the phenotypic plasticity of winter wheat (Triticum sp.), one of the main staple agronomic crops. Our current limited understanding of the dynamic nature of the root system architecture is due to the difficulties associated with in situ phenotyping and characterization of anatomical traits. The objectives of this thesis were to 1) review advancements in root phenotyping methodologies and past, present, and future predictions; 2) evaluate differences in root biomass accumulation and remobilization among 22 Virginia Tech-developed elite germplasm; 3) evaluate potential genetic variability for root biomass accumulation across breeding lines. Minimal genetic variation was observed for root biomass accumulation through time. Soil coring proved not to be a very effective method for capturing genetic variability of root biomass accumulation from a soil depth of 10 cm. However, a low genetic signal was also observed for shoot biomass, even though the entire field plot for each genotype was sampled. Yet, a considerably higher genetic signal was observed for plant height. These results suggest that both root and shoot biomass are complex, polygenic traits that require significantly more attention to evaluate genetic differences. / Master of Science / Climate change induces numerous abiotic and biotic barriers to our global cropping systems. Mineral fertilizer reserves are expected to deplete within the next 80 years while our agricultural lands continue losing fertility. This translates into increased yield discrepancies among the most prominent staple agronomic crops. Historically, crop improvement has been performed through indirect selection upon shoot-based traits for yield improvement. However, the capacity of genetic gain from these conventional selection criteria is projected to stabilize. Therefore, it would be beneficial for future global crop production if the initiative was taken to identify a new breeding target that can ensure climate resiliency in staple crops, such as winter wheat (Triticum). Root system architecture (RSA) is defined as the spatial distribution of embryonic and post-embryonic roots throughout a growth medium. This has the potential to become a new breeding target. However, there are numerous difficulties to overcome when evaluating roots in situ. In addition, there is no standardized root phenotyping method that can be implemented nationwide due to the variability in phenotypic response in various growing environments. The objectives of this thesis are to 1) reveal the advancements in root phenotyping and its legitimacy for standardization, 2) explore the genetic architecture of root system architecture, and 3) evaluate the genetic variability of root biomass accumulation for climate resiliency. Minimal genetic variation was observed for root biomass accumulation through time. Soil coring proved not to be a very effective method for capturing genetic variability of root biomass accumulation from a soil depth of 10 cm. However, a low genetic signal was also observed for shoot biomass, even though the entire field plot for each genotype was sampled. Yet, a considerably higher genetic signal was observed for plant height. These results suggest that both root and shoot biomass are complex, polygenic traits that require significantly more attention to evaluate genetic differences.

Master of Science / Department of Agronomy / P. V. Vara Prasad, / Kraig L. Roozeboom / Replacing fallow with cover crops can provide many benefits, including improved soil quality and reduced nitrogen fertilizer requirements. The addition of cover crops into no-till systems has become popular in recent years as a means of increasing cropping system intensity and diversity. A primary concern of producers in the Great Plains is the possibility that cover crops may reduce the amount of soil water stored in the profile for the next grain crop, potentially reducing yields. Multi-species cover crop mixtures that enhance the ecological stability and resilience of cover crop communities may produce greater and more consistent biomass than single species. Field experiments were established in 2013 and 2014 near Belleville and Manhattan, KS following winter wheat (Triticum aestivum L.) harvest to evaluate the effect of cover crop species and species complexity on changes in soil profile water content and water use efficiency. Along with a chemical fallow control, ten cover crop treatments were tested: six single species, two-three component mixes, a mix of six species, and a mix of nine species. Volumetric water content was measured using a neutron probe and a Field Scout TDR 300. Similar data were collected in 2014 from an experiment established in 2007 comparing fallow, double-cropped soybean, and four cover crop types (summer and winter legumes and non-legumes) in a no-till winter wheat-grain sorghum-soybean cropping system near Manhattan, KS. Results from both studies showed that grasses produced the most dry matter with the highest water use efficiency (up to 618 kg cm-1). Fallow lost up to 7.9 cm less water than all cover crop treatments throughout cover crop growth and in the fall, but captured up to 3.4 cm less moisture in the spring than the cover crops that added residue to the soil surface. Brassica species extracted water from deeper in the soil profile than the other cover crop species. Species complexity affected water use only relative to the proportions and productivity of their individual components, with no advantage in water use efficiency for the more complex mixtures.

Nitrogen use efficient (NUE) wheat varieties have potential to reduce input costs for growers, limit N runoff into water ways, and increase wheat adaptability to warmer environments. Previous studies have done little to explain the genetic basis for NUE and components, nitrogen uptake efficiency (NUpE) and nitrogen utilization efficiency (NUtE). Four studies were conducted to 1) determine genotypic stability of NUE under high and low N regimes and under warming 2) determine effect of warming on NUE 3) indentify QTL associated with NUE components 4) assess the utility of canopy spectral reflectance (CSR) as a high-throughput phenotyping device for NUE. Genotypic response to N stress or warming varied. Uptake efficiency was found to be more important than utilization efficiency to genotypic performance under high and low N environments and under warming. Selection under low N for NUpE and under high N for NUtE most efficiently identified NUE varieties. Uptake and utilization were lower under warming due to quickened development. No strong correlations between the CSR indices and NUE existed. No QTL were found to be significantly associated with NUE components. Further research into the mechanisms controlling NUE and to reveal plant response to N stress and under warming is necessary.

Lietuvos žemdirbystės instituto Javų selekcijos skyriaus devynlaukėje sėjomainoje 2008 - 2009 metais buvo atlikti žieminių kviečių ( Triticum aestivum. L) konkursiniai bandymai, kuriuose buvo tirta 18 perspektyvių selekcinių linijų ir palyginta su standartine veisle Zentos. Atlikus šiuos bandymus nustatyta, kad didžiausią derlių išaugino Flair/Ansgar (8,03 t ha-1) ir Flair/Lut 9-329 DH (7,84 t ha-1) selekcinių linijų kviečiai atitinkamai 17,2 ir 14,4 proc., lyginant su kontroline Zentos (6,85 t ha-1) veisle. Žieminių kviečių, skirtų krakmolo gamybai, atrinktos mažiausiai baltymingos, kurių grūduose baltymų kiekis buvo atitinkamai 8,5 proc. ir 8,7 proc., lyginant su Zentos (10.8 proc.) veisle. Daugiausiai krakmolo, lyginant su kontroline Zentos (70,2 proc.) veisle, sukaupė Olivin/Cubus DH (73,3 %), Biscay/Dream (73 %.), Dream/Bill (72,6 %) selekcinės linijos. Selekcinės linijos Tarso / Lut 96-3 (68,8 proc.) ir Dream / 91002 G 2.1 (70,1 proc.) brokuotinos dėl mažo krakmolo kiekio grūduose. Optimalus produktyvių stiebų skaičius 170,3; 179,0 ir 200 vnt m-2 išauginęs krakmolingiausius grūdus yra atitinkamai Dream/Bill, Olivin/Cubus DH ir Biscay/Dream selekcinių linijų. / In 2008-2009 a 9-field crop rotation of the Grain Crop Selection Department of the Lithuanian Institute of Agriculture was used for the purpose of carrying out experimentations with winter wheat (Triticum aestivum. L) that involved a research of 18 prospective breeding lines and their comparisons with the standard breed Zentos. Experimentations showed that maximum yield was obtained from Flair/Ansgar (8,03 t ha-1) and Flair/Lut 9-329 DH (784 t ha-1) breeding lines amounting for 17,2 percent and 14,4 percent respectively, when compared to the control breed Zentos (6,85 t ha-1). Breeding lines (Flair/Ansgar, Olivin/Cubus DH) with the least protein content were selected from the winter wheat breeds particularly intended for the purpose of starch production; their protein content was 8,5 percent and 8,7 percent, respectively when compared to Zentos breed (10,8 percent). The highest starch content was found in wheat of breeding lines Olivin/Cubus DH (73,3 percent), Biscay/Dream (73 percent), Dream/Bill (72,6 percent) when compared to the control breed Zentos (70,2 perent). Breeding lines Tarso / Lut 96-3 (68,8 percent) and Dream / 91002 G 2.1 (70,1 percent) were considered to be worth discarding due to the low starch content in grain. The optimum number of productive stems was obtained from breeding lines Dream/Bill, Olivin/Cubus DH and Biscay/Dream and amounted for 170,3, 179,0 and 200 stem units per m-2, respectively.

Tyrimai, siekiant išsiaiškinti, kaip keičiasi fotosintetinių rodiklių intensyvumas ir grūdų kokybė bei derlingumas priklausomai nuo augimo tarpsnio bei tręšimo azotinėmis trąšomis, atlikti 2009-2010 metais. Pigmentų ir tirpiųjų sacharidų kiekis tirtas Agrobiotechnologijos laboratorijoje, o grūdų kokybės rodikliai ištirti AB „Kauno grūdai“ laboratorijoje. Žieminiai kviečiai auginti Lietuvos žemės ūkio universiteto Bandymų stotyje, kur dirvožemis IDg8-k (LVg-p-w-cc) – karbonatingas sekliai glėjiškas išplautžemis (Calc(ar)i-Epihypogleyic Luvisols). Tyrimamas pasirinktos dvi žieminių kviečių veislės: labai gerų kepimo savybių ’Ada’ ir gerų kepimo savybių ’Tauras DS’. Buvo tiriama, kaip vegetacijos metu kinta pigmentų ir sacharidų kiekis augalų lapuose ir kaip azoto trąšos įtakojo baltymų, šlapiojo glitimo, sedimentacijos, krakmolo, kritimo skaičiaus pokyčius grūduose ir grūdų derlingumą. Azoto trąšos augaluose skatino bendrą pigmentų kiekio didėjimą, o tirpiųjų sacharidų kaupimuisi esminės įtakos neturėjo. Taip pat azoto trąšos beveik visuose variantuose patikimai skatino baltymų kaupimąsi grūduose, didino sedimentaciją ir šlapiojo glitimo kiekį, o krakmolo kiekis mažėjo atvirkščiai proporcingai baltymų kiekiui. Tręšimas azoto trąšomis visuose variantuose patikimai didino derlingumą. / The research was carried out in the period from 2009 to 2010 to determine the changes in the intensity of photosynthetic characteristics ,grain quality and yield, depending on the growth phase and fertilization with nitrogen fertilizer. The amount of pigments and soluble sugars was investigatd in the laboratory of Agrobiotechnology and the indicators of grain quality were explored in the laboratory of JSC „Kauno grūdai“. Winter wheat were grown in the Experimental Station of Lithuanian University of Agriculture, where the soil is IDg8 k (LVD-pw-cc) - calcareous shallow Luvisols (Calc (or) i Epihypogleyic Luvisols). Two varieties of winter wheat were selected for the experimental study: ’Ada’ with a very good baking properties and ’Tauras DS’ with good baking properties. The research focused on how vegetation changes affect the pigment and sugars content in the plant leaves, as well as the influence of nitrogen fertilizers on the grain yield and changes in content of protein, wet gluten, sedimentation and starch in the investigated grain. The results suggest that the nitrogenous fertilizers stimulated the overall growth of the cultivar, the pigment content but it had no significant effect on the accumulation of soluble sugars .Moreover, almost in all cases of the nitrogen fertilizer treatments it significantly promoted the accumulation of grain protein, increased sedimentation and wet gluten content however the starch content decreased inversely with the protein. The grain... [to full text]

Siekiant įvertinti supaprastinto žemės dirbimo ir tiesioginės sėjos įtaką žieminių kviečių agrofitocenozei ir dirvos fizikinėms savybėms atlikti tyrimai 2009-2010 m. ilgalaikiame eksperimente, kuris įrengtas 1988 m. Lietuvos žemės ūkio universiteto Bandymų stotyje giliau karbonatingame giliau glėjiškame išplautžemyje – IDg4-k2 (Endocalc(ar)ic Endohipogleyic Luvicol – LWg-n-ww-cc) FAO, vidutinio sunkumo priemolyje ant smėlingo lengvo priemolio. Lauko eksperimento variantai: 1. Įprastinis arimas 23-25 cm gyliu (IA); 2. Seklusis arimas 12-15 cm gyliu (SA); 3. Gilusis purenimas (kultivavimas strėliniais noragėliais 23-25 cm gyliu) (GP); 4. Seklusis purenimas 12-15 cm gyliu (SP); 5. Tiesioginė sėja į neįdirbtą dirvą (glifosatu purškiama pagal reikalą) (ND). Nustatyta, kad žemės dirbimo supaprastinimas bei tiesioginė sėja ženkliai padidino trumpaamžių ir daugiamečių piktžolių daigų tankumą žieminių kviečių krūmijimosi tarpsnyje, lyginant su įprastiniu arimu. Taikant ilgalaikę tiesioginę sėją žieminių kviečių agrofitocenozėje krūmijimosi tarpsnyje daugiau išplito bekvapis šunramunis, mažoji strugena, dirvinis garstukas ir trikertė žvaginė, lyginant su kitais žemės dirbimo būdais. Bekvapių šunramunių gausumas žieminių kviečių pieninės brandos tarpsnyje buvo taip pat ženkliai didesnis tiesiogiai javus sėjant į ražienas, negu taikant įprastinį ir supaprastintą žemės dirbimą. Didesnis trumpaamžių piktžolių skaičius rastas kviečių pieninės brandos tarpsnyje giliai ir sekliai... [toliau žr. visą tekstą] / In order to evaluate the effect of reduced tillage and direct seeding on agrophytocenosis of winter wheat and physical properties of soil, tests were carried out. In a long-term experiment conducted in the period between 2009 and 2010, which was installed in 1988 in Experimental Station at Lithuanian University of Agriculture in calcarous and endohypogleyic luvisol – IDg4-k2 (Endocalc(ar)ic Endohipogleyic Luvicol – LWg-n-ww-cc) FAO, in medium loam on sandy light loam. Field experiment options: 1. Routine Plowing depth of 23-25 cm (RP) 2. Shallow Plowing depth of 12-15 cm (SP); 3. Deep Hoeing (cultivation with arrow-type ploughshare, depth of 23-25 cm) (DH); 4. Shallow Hoeing depth of 12-15 cm (SH); 5. Direct Seeding in uncultivated soil (sprayed with glyphosate if necessary) (US). The results show that when compared with conventional tillage, the reduced tillage and direct seeding have significantly increased the density of seedlings of short-lived perennial weeds at the stage of tillering of winter wheat. When compared with other methods of tillage, during long-term direct seeding, at the stage of agrophytocenosis and tillering of winter wheat, the scentless false mayweed, mouse-tail, wild mustard and shepherd's purse were more widespread. Abundance of scentless false mayweed at the stage of lactic ripeness of winter wheat was significantly greater when grains were directly sown in the stubble than using conventional and reduced tillage. A larger number of short-lived... [to full text]

Lauko bandymas tiriant biologinių preparatų Fosfix ir NPK Magic įtaką žieminių kviečių produktyvumui skirtinguose azoto trąšų fonuose atliktas 2013 m. ASU Bandymų stotyje. Dirvožemis IDg8-k (LVg-p-w-cc) – karbonatingas sekliai glėjiškas išplautžemis (Calc(ar)i-Epihypogleyic Luvisols). Tyrimo objektas: Žieminių kviečių (Triticum aestivum L.) veislė ʽAdaʼ. Darbo metodai: Derliaus nuėmimo metu kiekviename bandymo laukelyje buvo išpjauti 4 – iose vietose 0,25 m2 apskaitiniai ploteliai. Kiekvieno laukelio kviečių pėdai atnešti į laboratoriją. Nustatyti derliaus struktūros elementai. Po to apskaičiuoti vidutiniai rodikliai. Tyrimų duomenys statistiškai įvertinti vieno veiksnio kiekybinių požymių dispersinės analizės metodu, taikant kompiuterinę programą ANOVA (Tarakanovas, Raudonius, 2003). Darbo rezultatai: NPK magic esmingai didino žieminų kviečių derlingumą, grudų skaičių varpose bei varpos produktyvumą visuose tręšimo fonuose. Atitinkamai derlingumo skirtumas lyginant su kontrole panaudojus NPK Magic 1,5t/ha. Pasėlio tankumui ir 1000 grudų masei NPK Magic esminiai pokyčiai nepastebėti. Išpurškus tuo pačiu metu preparatą Fosfix jo veiksmingumas pastebėtas mažesnis, tačiau visuose rodikliuose neesmingas lyginant su NPK Magic. Panaudojus Fosfix ir patręšus N140 ir N180 gautas esminis žieminų kviečių derlingumas (7,32 t/ha) lyginant su kontrole. / Field testing for biological agents Fosfix and NPC Magic on winter wheat productivity of different nitrogen fertilizer backgrounds were made in 2013 ASU test station. Soil IDg8 -k (LVg - pw - cc ) - shallow calcareous luvisol ( Calc ( ar) i - Epihypogleyic Luvisols) . Object of the work: winter wheat ( Triticum aestivum L. ) variety ʽAdaʼ. Method of the work: on harvest time for each test field was cut in 4 different places of 0.25 m2 plots accounting. Each box of wheat sheaves were bringed to the laboratory. Set vintage structure elements. Research data to statistically assess the quantitative characteristics of a factor analysis of variance method using a computer program ANOVA ( Tarakanovas, Red, 2003) . The results of the work: NPK magic substantially increased winter wheat yield, grain number per ear and ears productivity in all fertilization backgrounds. Accordingly yields compared to the control using NPK Magic 1.5 t / ha. Stand density and weight of 1000 grains NPK Magic fundamental changes were not noticed. Droplets at the same time with the product Fosfix efficacy had lower, but not essential in all indicators compared with NPK Magic. Using Fosfix and N140 and N180 fertilized received substantial winter wheat yield ( 7.32 t / ha) compared to the control.

Rotating wheat with other crops is a common practice in the Willamette Valley of western Oregon. Depending upon previous crop and soil type, current N fertilizer recommendations for wheat in the Willamette Valley vary widely. Excessive fertilizer poses environmental risk, whereas lower N inputs than required by the crop represent economic losses to growers. Growers and their advisors face the challenge to minimize the environmental risk, and at the same time to maintain or increase economic returns. Questions are often raised concerning the efficient use of N fertilizer and accurately predicting the amount of N needed by wheat following different crops. The first study measured growth, N uptake and N use efficiency (NUE) of winter wheat grown after either a legume or oat for three years. In all three growing seasons, winter wheat showed higher biomass, N uptake and NUE when grown after a legume than after oat. The contribution of legume was evident before the wheat was fertilized in spring, indicating that legume N had mineralized in fall or winter. Contribution of soil N to wheat suggested that fertilizer N can be reduced by 44 kg N ha����� if a legume is grown previously. Nitrogen use efficiency estimated 50 to 70 days after N application by isotopic method (24 to 94%) was comparable with that estimated simply by difference (21 to 94%) at the same time. The second study predicted gross mineralization rates using analytical models. Comparable N mineralization was predicted by a model assuming remineralization and a model assuming no remineralization, suggesting that remineralization was negligible. In the spring, mineralization-immobilization turnover was at a lower pace than expected in both rotations. In two growing seasons, gross mineralization rates were higher where the previous crop was legume (0.37 to 0.74 kg����� ha����� day�����) as compared to where oat was grown previously (0.14 to 0.6 kg����� ha����� day). Negative net mineralization indicated that fertilizer N was immobilized in the oat-wheat rotation. The third study evaluated calibration and digestion techniques used to determine elemental concentration in grasses. Use of a dry ashed standard to calibrate the ICP spectrometer generated highly variable calibration curves and was not a viable calibration method. Good agreement was found between chemical and microwave digested standards. Dry ashing resulted in considerable S and Mn losses, whereas, perchloric acid digestion and microwave digestion showed similar results. Our study suggests that if routine analysis are to be performed for macro nutrients or involve trace level work, the best method is microwave digestion with chemical standard calibration of ICP spectrometer. / Graduation date: 1999