bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature Dependence of Water Uptake by Plant Roots1
Authors: Dalton F. N. , Gardner W. R. 
Published: July 2010

AbstractThe transport of water through root membranes is described in terms of equations which couple water and solute transport. The solute transport equation includes active as well as passive uptake. Temperature effects are manifested in the viscosity of water, the osmotic permeability coefficient of the membranes, and the rate constant for the active solute uptake. From standard reaction rate kinetics, reasonable estimates of the temperature coefficients of these three processes can be made. A general equation for the effect of temperature on the uptake rate for a given driving force is derived. This difference in flux between live and dead roots is adequately described by the model, indicating the significance of the active component of the uptake process.
Forage Yield and Quality of Phalaris as Affected by N Fertilization and Defoliation Regimes1
Authors: Saibro Joao C. , Hoveland Carl S. , Williams John C. 
Published: July 2010

AbstractPhalaris (Phalaris aquatica L., also referred to as P. tuberosa L.) is a winter productive cool‐season perennial grass species having potential in the southeastern U.S. The purpose of our study was to determine the effect of N fertilization rates and defoliation on forage yield, in vitro dry matter digestibility (IVDMD), total forage N and NO3‐N, and total non‐structural carbohydrates (TNC) stored in conns. The synthetic, ‘AP‐2’ phalaris, was fertilized at 100, 200, 300, and 400 kg N/ha/year and harvested at vegetative, inflorescence emergence, and seed stages of growth over a 2‐year period in the field.Forage yield, total N, and NO3‐N concentration increased linearly with increasing N fertilization. Maximum dry forage yield was 10 metric tons/ha annually. Total N concentration ranged from 2.8 to 4.0%. Forage NO3‐N concentration was highest in autumn but less than that considered potentially toxic to ruminants. Harvesting at more advanced plant maturity increased forage yield while reducing NO3‐N and IVDMD. The IVDMD was relatively high, averaging 63% over the year. Corm reserves of TNC decreased with N fertilization but increased with plant maturity. TNC in corms remained low throughout the active growing season. Results of this study indicate that AP‐2 phalaris can utilize up to 300 kg N/ha annually either under frequent defoliation or cutting at hay stage. This grass maintains relatively high IVDMD at a fairly advanced stage of maturity.
Quantitative Estimation of Living Wheat‐Root Lengths in Soil Cores1
Authors: Ward Kathy J. , Klepper Betty , Rickman R. W. , Allmaras R. R. 
Published: July 2010

AbstractA rapid, efficient method for separating living wheat (Triticum aestivum L.) roots from dead roots in field soil samples is needed to understand the dynamic nature of wheat root development, because the proportion of living roots is highly variable and often may constitute less than 20% of the estimated length. A soil core, wrapped in a cloth “root bag” with a weave comparable to a 100‐mesh screen (0.149 mm opening) was suspended in a container of water from a wrist‐action shaker. Roots, organic residues, and sand remained in the bag, but fine sand, silt, and clay washed out. Roots and organic material were then decanted from the remaining sand. A 1% aqueous solution of congo red stained the living roots red; nonliving roots remained unstained or were stained a brownish pink. After flotation separation of the stained roots from debris, living root length was estimated. Newman's grid method was modified to measure root length with an accuracy of ±9% as determined with known lengths of string. With these combined techniques of separation, staining, and length measurement, we could determine rooting density with an accuracy of ±9%. When incubated at 15 C, severed living wheat roots could be stained for up to 1 week, but stainability dropped to less than 35% after 5 weeks. Most monocot roots stained more intensely than dicot roots, indicating that monocot‐dicot root separation from the same root medium may faciliate studies of root competition.
Fertilizer Placement Effects on Soybean Seed Yield, N2 Fixation, and 33P Uptake1
Authors: Ham G. E. , Caldwell A. C. 
Published: July 2010

AbstractVarious recommendations on placement of fertilizer for soybeans [Glycine max (L.) Merrill] have been made (banded near the seed or midway between the rows and surface broadcast and left on the surface or incorporated). Because P is an immobile element in the soil, placement may be critical.This study was planned to evaluate the efficiency of P fertilizer utilization by field‐grown soybeans with different fertilizer placements using 33P labelled fertilizer (35 kg P/ha) on a Waukegan silt loam soil (Typic Hapludoll) low in plant available N and P. In addition, urea (30 kg N/ha) labelled with 15N was added to measure the effect of P fertilizer placement on N uptake and N2 fixation using the ‘A’ value concept. The ‘A’ value is a mathematical expression for calculating the amount of available nutrient element in a soil in terms of a fertilizer standard provided that the proportion of the nutrient in the plant derived from this standard is determined (usually by isotope labelling).Fertilizer placement was evaluated in the field by using unlabelled urea N and P (concentrated superphosphate) in plot areas 2.25 × 10 m; a sub‐plot within the larger plot received applications of 15N labelled urea and 33P labelled concentrated superphosphate. Total plant samples for 15N and 33P analysis were obtained with special precautions to recover all leaves. Analysis of 15N was performed with photospectrometry methods; 33P was measured using a liquid scintillation technique.Soybean seed yield and total P uptake were increased significantly by adding P fertilizer with no differences among the fertilizer placements (seed yield ranged from 3,811 to 4,035 kg/ha compared to 3,200 kg/ha for the control). The 33P labelled fertilizer provided a direct, quantitative measure of the efficiency of plant use of the added P and provided a basis of evaluating the fertilizer placements without the hazards associated with 33P over the 149‐day experiment.The ‘AN’ value concept (based on ‘A’ value procedures using a nodulating and nonnodulating crop) provided a reliable estimate of N2 fixation which agreed with Kjeldahl measurements.
Effect of N Fertilization on Sugarbeet Crown Tissue Production and Processing Quality1
Authors: Halvorson A. D. , Hartman G. P. , Cole D. F. , Haby V. A. , Baldridge D. E. 
Published: July 2010

AbstractOver the past 4 decades, sucrose content of sugarbeets (Beta vulgaris L.) has decreased while root yield has increased. Reasons reported include processing of more crown material, because mechanical harvesting removes less crown tissue than hand‐topping methods, and incre ased use of N fertilizer. Our objective was to determine the relationship between N application rate and sugarbeet crown tissue production, and its effects on processing quality of sugarbeets. Reported are the results of two studies conducted in 1975 and one in 1976, each using a different sugarbeet cultivar and seven N rates. Green petiole material was removed before each sugarbeet was sectioned into root and crown tissues for yield and quality analyses. Crown tissue increased linearly as rates of N application increased. Root tissue and recoverable sucrose yields were near maximum when spring soil NO3‐N or soil NO3‐N plus added N reached 200 to 225 kg/ha. At higher N levels, crown tissue yield increased and sucrose content in both root and crown tissues decreased, offsetting any potential benefits from increased whole beet yield. When N was adequate for maximmn sucrose production, crown tissue contributed approximately 20% of the total recoverable sucrose per ha. As N rate increased, sucrose concentration, extractable sucrose per metric ton, and purity decreased whereas Na, K, amino‐N, invert sugar, and imaturity index values increased for both root and crown tissues. Root tissue always had higher levels than crown tissue of extractable sucrose and purity and lower levels of Na, amino‐N, invert sugar, and impurity index. Crown tissue production can be minimized, and processing quality of sngarbeets can be improved by conservative use of N fertilizer.
Wheat Responses to Seminal Root Geometry and Subsoil Water1
Authors: Meyer Wayne S. , Alston A. M. 
Published: July 2010

AbstractRapid drying of the topsoil following germination has been shown to restrict the depth of penetration of the nodal roots of wheat (Triticum aestivum L.). In such instances, the supply of subsoil water to the plant through the seminal root system assumes great importance.A glasshouse experiment was designed to assess the effects of altering the number of seminal root axes of wheat plants dependent on subsoil water and to examine characteristics of the metaxylem vessels in the seminal axes of two cultivars. Deep pots (12.7 ✕ 12.7 ✕ 120 cm) containing soil with a partially reconstructed profile were planted with seedlings of ‘Warimek’ and ‘Manitou’. Plants grew normally in a fully watered soil profile for 5 weeks; thereafter only the subsoil was watered. At stemelongation, all roots other than one, three, or five seminal roots on each plant were severed just below the crown. One set of plants was harvested 10 days after the treatments began and two additional sets, one with the subsoil water maintained at field capacity and the other with a subsoil that received no further water, were harvested at maturity.Five days after the root treatment was imposed, Warimek plants with one, three, or five seminal axes had lost 28, 26, and 17% of their leaves, respectively; corresponding values for Manitou were 40, 31, and 24%. Plants with fewer seminal roots had lower water potentials 4 days after the roots were cut. The rate of water use was greater for plants with more seminal roots. The different rates of water use resulted in leaf water potentials of −29, −39, and −43 bar for plants with one, three, or five seminal roots, respectively, in the drying subsoil 26 days after the treatments began. Grain yield was positively related to the amount of water available after anthesis. With the wet subsoil, yield increased with increasing number of seminal roots per plant; with the drying subsoil, yield decreased. The results showed that the yield response of wheat plants depended on the interaction of the root geometry and the availability of the subsoil water. It was also shown that the metaxylem vessel increased in radius along the seminal axis towards the apex and that all seminal axes within a cultivar had similar vessel radii.
Field Studies and Model Simulation of the First Square Event in Cotton1
Authors: Wanjura D. F. , Jones J. W. , Hesketh J. D. 
Published: July 2010

AbstractThe ability of cotton (Gossypium hirsutum L.) production models to accurately predict the first‐square event is essential for estimating square and boll production rates. A first‐square model was formulated which requires three plant character inputs: 1) mainstem node number limits for first‐square positions, 2) characterization of fist‐square distribution between the mainstem node limits, and 3) a measure of the variability of mainstem node generation times and one environmental parameter—mean daily air temperature.Observations were made in field populations of 200 plants grown in rows spaced 101.6 cm at population densities of 98,900 plants/ha. Canparison of model simulations with the field observations in which the cultivars ‘Paymaster 909,’ ‘Paymaster 303,’ and ‘Acala 3080’ were used indicated close agreement between simulated and observed cumulative first‐square curves. The firstsquare characteristics of subpopulations of plants that emerged on the same day (Day 2 or Day 4) were most accurately simulated by beginning the simulation on the day of initial emergence for the total population. This result suggested that germination and development of seedlings that emerged as late as 3 days after the earliest plants probably began simultaneously with the earliest seedlings.Sensitivity analysis was utilized for examination of the relative influence of model parameters on the firstsquare event. Raising the position limits of the first‐square node from the interval 4 and 9 to the interval 6 and 11 increased the length of the first‐squaring period from 22 to 25 days. Changing the distribution of limit squares between the node position limits by doubling the value of the binomial distribution parameter p from 0.3 to 0.6 caused the firstquaring period to increase from 20 to 23 days. Inoreasing the mean variance of mainstem‐node generation time from 0.1 to 0.4 increased the first‐squaring period from 22 to 23 days. Mean daily air temperature had the greatest effect on the first‐squaring period; a decrease in temperature from 27 to 21 C increased the length of the first‐squaring period from 15 to 35 days.
An Alfalfa Protein Concentrate from Four Cultivars at Three Growth Stages1
Authors: Kehr W. R. , Ogden R. L. , Satterlee L. D. 
Published: July 2010

AbstractNew sources of high quality protein are needed for human consumption. Alfalfa (Medicago sativa L.) is well known for its high yield of protein. Knowledge of genetic variation for protein concentrate yield among cultivars is needed.The alfalfa cultivars ‘Dawson’, ‘Kanza’, ‘Team’, and ‘Weevlchek’ were planted in field plots at the Mead Field Laboratory, Lead, Nebr., in 1972. Forage of the cultivars was harvested and sampled as three growth stages, bud, one‐tenth bloom, and full bloom, in the first and second cuttings of 1973. Forage samples were used for chemical analyses of fresh forage, pressing juice in the laboratory, protein extraction, and subsequent chemical analyses. The purposes of the study were to determine the yield of an alfalfa protein concentrate (without chloroplasts) (APC) from four cultivars at three growth stages, the forage yield and quality of fresh forage, and to determine the recovery and nutrient levels in the residue of processed forage.The cultivars did not differ in dry matter,protein,and carotene levels of fresh forage at any growth stage in either the first or second cutting. The percentage of protein in APC's did not differ among cultivars at any growth stage in either cutting and averaged 76%. Forage and APC yields differed among Cultivars. The lowest forage and APC yields were obtained from Kanza. About 1% of the fresh weight of alfalfa was recovered as APC. APC yield averaged about 200 kg/ha over cultivars and cuttings. APC recovery percentages differed among cultivars and the lowest recovery was from Kanza. Protein recovery decreased as physiologic mauturity increased.At one‐tenth bloom, average protein level of fresh forage was 18.6% compared with 16.4% protein in the residue after pressing (juice extraction), a 12% reduction due to processing. Average carotene level of fresh forage was 190 mg/kg, and carotene level of the residue was 145 mg/kg at one‐tcnth bloom, a 24% reduction.The yield of an alfalfa protein concentrate that contained 76% protein, potentially suitable for human consumption, vaned among cultivars as shown in this preliminary study.
Fitting the Law of the Minimum to Fertilizer Applications and Crop Yields1
Authors: Waggoner P. E. , Norvell W. A. 
Published: July 2010

AbstractLiebig's Law of the Minimum is a simple, logical, and successful predictor of crop response to fertilization. A statistical method is reported for fitting the Law by least squares regression to yield responses to two essential factors, with optional inclusion of a limit to maximum yield.The Law maybe written:y = MIN(a+bz2, c+dz2 m);where y is yield, z1 and z2 are two essential nutrients, and m is a maximum imposed by another factor. The expression MIN( ) defines y as the minimum of the specified values; and a,b,c and d are the intercepts and slopes relating y to z1 and z2. The parameters were estimated from crop responses to fertilizer by searching for the minimum residual sum of squares: where for each treatment with yield y1, X1 = z2 if c+dz2 ≤ a+bz1 and m, X1 = (a−c+bz1/d if a+bz1 < c+dz2 and m, X1 = (m−c)/d If m < a+bz1 and c+dz2.This logical law fit yields of corn that received N and P fertilizer more closely than three empirical functions, and the standard error of estimate for the law was within 14% of that of the most closely fitting function for two legumes that received K and P. Where the Law of the Minimum is logical, it can now be fitted statistically to observations, identifying nutrients limiting each yield and estimating the return from added nutrient.
Apparent Recovery of Fertilizer N by Coastal Bermudagrass on a Swelling Clay Soil1
Authors: Kissel D. E. , Bartek Larry , Zatopek L. J. 
Published: July 2010

AbstractThe apparent recovery of N fertilizer by Coastal bermudagrass [Cynodon dactylon (L.)] growing on swelling clay soils has usually been quite low (approximately 40 to 50%), possibly due to biological immobilization of large quantities of applied N fertilizer. The objective of this study was to determine if the net immobilization might be reduced after several years of continued fertilization, thereby improving the recovery of N by Coastal bermudagrass.The 6‐year study was set up with variable N rates (NH4NO3 was the N source), some applied only the first 3 years of the study, some applied only the last 3 years and some fertilized throughout the study. Measurements were taken of N removed in forage, soil NO3−‐N at the 504 kg N/ha rate, and soil organic N at the end of the study.Immobilization (as determined by the increase in soil organic N) accounted for over 50% of the applied N, about equal to the amount of N going into the harvested portion of the grass. Other potential losses of N such as leaching and denitrification were apparently insignificant. There was no indication of inorganic N accumulation in the later years of the study. However, some improvement in N availability was noted in the last three years of the study on those plots receiving fertilizer throughout the 6‐year study. The results from this study suggest that immobilization of fertilizer N on Coastal bermudagrass pastures would be a substantial sink for applied N fertilizer for an unknown but large number of years. Continuous generous fertilization programs would result in a gradual buildup of soil organic N with a resulting gradual improvement in N recovery by forage.
Cation Concentration of N‐ and K‐fertilized Smooth Bromegrass During the Spring Grass Tetany Season1
Authors: George J. Ronald , Thill James L. 
Published: July 2010

AbstractThe variable incidence of grass tetany in cattle within the spring tetany season suggests that considerable day‐to‐day change may occur in forage cation concentrations. An awareness for these fluctuations would seem to be important as research scientists attempt to understand the tetany syndrome. The objectives of this study were to observe changes in forage K, Ca, and Mg concentrations and the K/(Ca + Mg) milliequivalent ratios of smooth bromegrass (Bromus inermis Leyss.) at 2‐day intervals during the spring tetany season. An established stand of grass which had received N rate (0, 125, and 500 kg N/ha in 1970 and 0,250, and 500 kg N/ha in 1971 and one‐half the latter amounts in early 1972) and K source (0 and 125 kg K/ha annually as KCl, K2SO4,, and K2SO4,‐MgSO4) treatments was used for the spring of 1972 sampling. Fluctuations in forage cation concentrations were related to N and K fertilizer treatments, existing differences in soil exchangeable bases and pH due to previous fertilization and cropping, precipitation patterns, and changes in mean daily air temperature.Acidic soils resulting from previous N fertilization were associated with a 20 to 48% increase in bromegrass Mg concentrations.Mean soil Mg/K ratios of 2.8, 6.1, 7.6, and 7.8 for the 0–2.5, 2.5–5.0, 5.0–7.5, and 7.5–15 cm soil depths did not seem to result in higher forage Mg and lower K as the growing season progressed and root activity presumably increased at deeper soil depths.Potassium fertilizer significantly increased forage K concentration and decreased forage Ca and Mg. Forage Ca was decreased more by K2SO4,‐ MgSO4 than by KCl or K2SO4 fertilization. Significant but relatively small increases in forage Mg resulted for K2SO4,‐MgSO4, fertilization compared with other K sources.Increases in K/(Ca + Mg) cation ratios suggest a greater grass tetany risk for the intermediate level of N fertilization, followed closely by the high level of N. Nitrogen fertilization in the absence of K generally produced less risk compared with N check with or without K fertilization. Fertilization with K produced a relatively large increase in cation ratios at intermediate and high N levels, with values near 2.2 during late April and exceeding 2.2 during early to mid‐May.These data illustrate a simultaneous shift in two indices of grass tetany risk; that is, an increase in cation ratio above 2.2 and a decrease in forage Mg concentration below 0.20%. Both indices of risk became more serious during rainy periods and following a temperature rise above 14 C. Also, both are more serious with NK fertilization, whereas, N fertilization without K reduced the apparent risk.
Transpiration of Soybeans as Related to Leaf Area, Root Length, and Soil Water Content1
Authors: Eavis B. W. , Taylor H. M. 
Published: July 2010

AbstractSoybeans [Glycine max (L.) Merr. ‘Corsoy’] were grown in 100 or 162 liter containers located in a field environment near Ames, Iowa, in order to determine the effects on transpiration rates and leaf water potentials of varying the root length (RL) to leaf area (LA) ratios during a water extraction cycle.The RL/LA ratios were varied by combining two fertility levels with two watering history treatments using Clarion clay loam topsoil (Typic Hapludoll). Two container sizes provided two different quantities of water storage at the start of the drying cycle. The containers were sealed around the plant stems to prevent evaporation during the drying cycle.Transpiration rates were determined from differences in total container weights at known times. Leaf areas were estimated on several days from length‐width measurements on all terminal leaflets of a plant. Leaf water potentials were estimated by the pressure chamber technique. Root lengths were determined at harvest.Total transpiration (cm3/day) from the container increased linearly with leaf area. Transpiration rate (cm3/cm2/day) decreased linearly as soil water content deceasedb ut at any particular soil water content, root length had no significant (P = 0.95) effect on transpiration rate. When a particular treatment increased the RL/LA ratio, water uptake rate per m of root decreased proportionately. This inverse relationship between total root length on the plant and uptake rate per m of roots enabled the plants to maintain equal leaf water potentials (regardless of the RL/LA ratios) when the roots were located in soils of equal water contents.