Eric H. Simonne

Could the Dumas Method Replace the Kjeldahl Digestion for Nitrogen and Crude Protein Determinations in Foods

Increased demand for determinations of nitrogen (N), and hence crude protein (CP), has led to wider use of the Dumas method in place of the traditional Kjeldahl methods. Although Kjeldahl N (KN) and Dumas N (DN) represent different N fractions, published studies on infant formula, animal feed and meat products have indicated that DN could replace KN with little practical impact on the reliability of the N values obtained. This study was conducted to establish whether DN determination could replace that of KN in a broader range of foods for CP calculation. Statistical analysis was performed on in-house assayed KN and DN values together with published KN and DN values for selected food products. In the range 0.05-6.8% N, KN may be estimated from DN with the equation : KN = 1.00 (P<0.01) x DN - 0.09 (P=0.50) (n = 101, R 2 = 0.98, P-regression < 0.01). Because N levels in individual groups of food did not span the entire range of N contents, KN : DN ratios were calculated for each food group. KN : DN ratios differed significantly (R 2 = 0.25, P <0.01) from group to group. Ratios of 1.01 for dairy, 1.00 for oilseeds, 0.99 for feed, 0.98 for infant formulas, 0.95 for cereals, 0.94 for meats, 0.89 for vegetables, 0.80 for fish and 0.73 for fruits were valid for the estimation of KN and CP using DN data. CP was independently calculated as CP1 = H x KN or CP2 = H x KN : DN x DN, where H is the nitrogen to protein conversion factor for the food group. Mean differences between CPI and CP2 values were 0% for dairy, oilseeds, feed, infant formulas and baby foods, cereals, meat and meat products, vegetables and vegetable products and fruit, and 1% for fish. These results suggest that DN may replace KN for the determination of N and CP in selected food groups when appropriate coefficients are used.

Effects of irrigation and nitrogen rates on foliar mineral composition of bell pepper

Abstract Irrigation and nitrogen fertilization are two important aspects of bell pepper production. Yet, limited information is available on the effect of irrigation on foliar nutrient content. Bell pepper were grown on bare ground under two nitrogen fertilization rates (11 and 19 kg N week‐1) and irrigated according to an irrigation scheduling model based on weather data and crop age. Eight irrigation rates ranged between 36 and 148% of the model rate. Leaf samples were taken at first bloom (62 days after transplanting, DAT) and after final harvest (84 DAT). Yield response and the foliar content of all essential elements determined [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), copper (Cu), iron (Fe), molybdenum (Mo), manganese (Mn), zinc (Zn)] responded linearly or quadratically to irrigation rates and most foliar nutrient contents remained within or above the sufficiency range. Foliar mineral content tended to be lower at 84 DAT as compared to 62 DAT. Only Ca bec...

EFFECT OF CURRENT FERTILIZATION PRACTICES ON NUTRITIONAL STATUS OF DOUBLE-CROPPED TOMATO AND CUCUMBER PRODUCED WITH PLASTICULTURE

When vegetables are double-cropped on polyethylene mulch, fertilizer recommendations for each crop may need to be adjusted because liming and preplant applications are done prior to laying plastic. When current fertilizer recommendations for single crops were used for cucumber following tomato, the cucumber plants looked like green, indicating a nitrogen (N) and/or potassium (K) deficiency was developing, suggesting that nutrient availability for the second crop was not adequate for producing the highest yields. Therefore, the nutritional status of both crops was diagnosed using sufficiency range data and DRIS norms to determine which nutrient(s) was limiting crop nutrition. Regardless of N source used as a sidedress injection material (at a rate of 7 kg N ha−1wk−1 as ammonium nitrate or calcium nitrate) or liming material used to adjust soil pH to 6.5 (carbonate- or oxide-based calcitic or dolomitic lime), foliar levels of N and K, and possibly phosphorus (P) were found to be limiting factors according to sufficiency range data and DRIS norms. This study suggests that current fertility recommendations for tomato and cucumber grown as single crops in Alabama need to be reevaluated for double crops.

Adjustments of sufficiency ranges of selected ornamentals and turfgrasses for assessing nitrogen status with Dumas‐N data

Abstract With recent advances in nitrogen (N) analyzers, the Dumas method may replace the Kjeldahl method for the routine diagnosis of N in plants. Since these two methods recover different N fractions and no conversion factor is available to convert Dumas N (Dn) to Kjeldahl N (Kn) data, Kn:Dn ratios were determined for selected ornamentals (anthurium, Anthurium andraeanum Linden; orchid spp. Cattleya, Dendrobium, Oncidium, Phalaenopsis, and Vanda; leatherleaf fern, Rumohra adiantiformis (G. Forst) Ching; tree fern, Asparagus densiflorus (Kunth) Jessop) and turfgrasses (creeping bentgrass, Agrostis palustris Huds. cv. Penncross; bermudagrass, Cynodon dactylon L.). Samples were dried at 70°C for 72 hr and ground to pass a 20‐mesh sieve. Kn was determined by colorimetry after digestion of 0.4 g of tissue using a CuSO4/TiO/K2SO4 catalyst and 10 mL of H2SO4 at 450°C for 2 hr. Dn was determined using 0.2 g of sample and a LECO FP‐428 N Analyzer. Over the 0.4–6.6% N range, Dn was a good predictor of Kn; Kn = 0....

Does the nitrate fraction account for differences between dumas‐N and Kjeldahl‐N values in vegetable leaves?

Abstract With recent advances in nitrogen (N) analyzers, the Dumas method may replace the traditional Kjeldahl method for the routine diagnosis of N in plants. Because of its nature, the Dumas method truly determines total N. The Kjeldahl method only converts protein N and some nitrate (NO3‐N) into ammonium. Therefore, the N‐NO3 ‐ fraction may explain the difference observed between Kjeldahl‐N (Kn) and Dumas‐N (Dn) values. This study was conducted to (1) determine the Kn:Dn ratio for vegetable crops and (2) evaluate the effect of the size of the nitrate fraction on the Kn:Dn ratio. Over the 0.9–7.0% N range, Dn was a good predictor of Kn in vegetable samples. The Kn may be estimated from Dn as Kn=0.68 Dn (n=134 obs., R2=0.71, p<0.01). For all vegetable crops combined, the mean Kn:Dn ratio was 0.75. This ratio suggests that approximately 25% of N in the samples was recovered by the Dumas method but not by Kjeldahl digestion. This percentage is much higher than the actual N‐NO3 foliar content. These results...

Laboratory and Greenhouse Evaluation of Quicklime Sources for Suitability as Agricultural Liming Materials

Abstract Quicklime or burnt lime (CaO), is a highly soluble liming material recognized as an acceptable means for neutralization of acid soils in the United States. Blending CaO and MgO with agricultural lime (CaCO3) may prove an alternative to ground agricultural limestone for raising soil pH and providing fertilizer Ca and Mg for crop growth. The objectives of this study were to determine the chemical properties of several CaO, MgO, and CaCO3 liming blends compared to carbonate limestones, and analyze their respective effects on soil solution chemistry and shoot yield of a sorghum-sudangrass hybrid grown under greenhouse conditions. Three formulations of oxide liming materials (CaO, CaO + CaCO3, and CaO + MgO + CaCO3) were evaluated in the laboratory to determine their respective effectiveness as soil amendments compared to two dolomitic limestones (ground and pelletized) and reagent-grade calcium hydroxide [Ca(OH)2]. A 150-day incubation study was conducted to determine the effects of liming materials on soil pH and extractable nutrients, and a greenhouse study was completed to observe the effects of liming materials and rates on the herbage yield of a sorghum-sudangrass hybrid. Oxide liming materials averaged higher calcium carbonate equivalence (CCE) than ground and pelletized dolomitic limestones. An incubation study found CaO, CaO + CaCO3, and CaO + MgO + CaCO3 resulted in rapid pH adjustments (from pH 4.1 and 4.4 to 6.0 +) at one day after test initiation for two soil types and gave higher mean pH values than carbonate limes when applied at equivalent rates based upon CCE. Oxide liming materials also resulted in higher concentrations of soil extractable calcium (Ca) and magnesium (Mg), and the use of all liming materials, regardless of chemical form, alleviated Al toxicity. In a nine week greenhouse bioassay, all oxide liming materials and reagent-grade Ca(OH)2 were applied at 1/2X, 1X, and 2X the recommended application rate of ground dolomitic limestone based on CCE, resulting in similar or higher shoot yields comparatively at conclusion of this study. Because oxide liming materials have higher CCE values and provide more water-soluble sources of fertilizer Ca and Mg compared to ground and pelletized limestone, producers have potential for obtaining a more complete neutralization of acid soil conditions and shoot yields similar to or higher than those obtained with dolomitic limestone, using less material in the process. This study did not determine if changes in current liming practices would result in reductions of total fertilizer costs per year using oxide limes in place of carbonate forms.

Effect of nitrogen form ratio on pansy growth and nutrition and the palatability to white‐tailed deer

Abstract Pansies are one of the most popular annual bedding plants in the United States. Growth and uptake of essential nutrients as influenced by N‐form ratio was evaluated in pansy as well as what role pansy nutrition plays in the protection of pansy against feeding damage by white‐tailed deer provided by selected repellents. Plants were grown under three N‐form ratios: 100:0, 50:50, and 0:100NO3:NH4. Dry weight was highest for pansy treated with 100:0 and lowest for plants treated with 0:100 NO3:NH4 Mean quality ratings were 4.07 for pansies grown with 100:0,1.80 for pansies grown with 50:50, and 0.78 for pansies grown with 0:100. Potassium (K), magnesium (Mg), and manganese (Mn) content was lower in plants treated with 0:100 than in those treated with 100:0. Ammonium may have competed with these cations for uptake. Boron (B), copper (Cu), molybdenum (Mo), and aluminum (Al) content was highest in plants treated with N‐NH4. There was no significant difference shown in nutrient levels caused by repellent...

A simple format for reporting methods used in nutritional studies : Application with Loropetalum response to fertilizer rates

Abstract Loropetalum (L. chinense) cv ‘Blush’, ‘Burgundy’, and ‘Pizzazz’ were grown for 16 months using different rates and application schedules of a 17–7–12 slow‐release fertilizer. Rates were45,68,or 91 g pot1, each applied once in the Spring, or as a split application, half in the Spring, and half in the Fall. A simple format for reporting fertility, methodology used in tissue sampling, and analytical methodology was developed and used. Fertilizer treatments did not affect significantly growth and color ratings 4 and 12 months after potting (p>0.30). ‘Burgundy’ was significantly the fastest growing cultivar. Yet, all plants from all treatments and cultivars were of commercial quality 12 months after potting. Foliar nutrient content was significantly affected by fertilization treatment for most of the essential elements (p 0.10). However, differences due to fertilizer treatments were of limited practical importance as they did not follow the trends in fertilizer rates. Bas...

EFFECT OF LIMING MATERIALS ON MEDIA pH AND OVERALL GROWTH AND NUTRITION OF DWARF NANDINA

ABSTRACT Ground dolomitic limestone (CaCO3/MgCO3) is used throughout the southeastern United States as a fertilizer amendment to soilless media. In addition to neutralizing media acidity, carbonate-based limestone also provides a source of calcium (Ca) and magnesium (Mg) for growth of many woody ornamental species, among these dwarf nandina. This study was conducted to compare the effects of CaO and CaO/MgO/CaCO3 blends to ground dolomitic limestone on the growth, marketable quality, and foliar nutrition of Nandina domestica ‘Nana Purpurea’ grown in soilless media. Materials were preplant incorporated based on the calcium carbonate equivalence (CCE, or acid-neutralizing equivalence) of ground dolomitic limestone (CCE=63) and plants were arranged in a completely randomized design (CRD). Growth indices (GI) were determined and plants harvested for tissue dry matter weights and foliar nutrient content. Plants amended with CaO, agricultural gypsum (CaSO4ċ2H2O), or pelletized dolomitic limestone, were of similar or better quality than plants amended with ground dolomitic limestone. Greatest nutrient uptake [nitrogen (N), Ca, potassium (K), and phosphorus (P)] was likewise observed for these treatments. All liming materials resulted in higher nutrient uptake compared to the unlimed control and highest foliar Mg was reported for plants amended with ground and pelletized dolomitic limestones. In year 1, plants were of similar quality, with the exception of the Ca(OH)2 treatment, which gave the lowest foliar quality ratings. In year 2, all plants were of marketable quality. Throughout the study, and especially during year 2, many foliar nutrient levels fell below established survey averages for dwarf nandina, illustrating the need to supplement media mixes with additional fertilizers during the growing season. All liming materials raised media pH to within the target range for nursery crops (pH=5.5–6.5) within one month from initial application, but lost their most positive neutralizing effect by the end of the third month. Research conducted indicates that CaO, CaO/MgO/ CaCO3 blends, CaSO4ċ2H2O, or pelletized limestone may serve as suitable alternatives to ground dolomitic limestone for use in soilless media.

'Safety first': A simple and practical safety manual for the analytical laboratory

Abstract The emerging analytical laboratory of the late 1990s is based on the technical, quality assurance/quality (QA/QC) control, and safety manuals. While much emphasis has been placed on analytical techniques and QA/QC programs, laboratory safety should not be addressed only in cases of emergency. However, following safety guidelines may not be simple. In many cases in the United States, Federal or State laws, and city or county ordinances are not clear, or limited in scope. University‐affiliated laboratories can often rely on the office of safety and environmental health for university‐wide safety policies. Because these policies are often difficult to implement and because relying on common sense for laboratory safety is insufficient, we drafted ‘Safety First’, a simple and practical laboratory safety manual. Its objective is to highlight the ‘details’ that make the laboratory a safe and pleasant place to work in. It is not intended to replace any other official safety document. It is primarily inte...