bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield and Quality of Alfalfa as Influenced by Additions of S to P and K Fertilizations under Greenhouse Conditions1
Authors: Martel Y. A. , Zizka J.
Published: July 2010

Alfalfa (Medicago sativa L.) obtains sulfur from soil reserve, air, and rainfall. These sources of S may need to be supplemented with fertilizer S in normal superphosphate to produce optimum yields. The objective of this work was to determine the need of alfalfa in S fertilization in relation with the addition of P and K normally used on Quebec soils. Alfalfa ‘Rambler’ was grown in the greenhouse and supplied with P, K, and S. A total of 18 treatments and 3 replicates were used on two types of soils — a Humaquept (silty clay Kamouraska) and a Haplorthod (sandy‐loam St. André). Dry matter yields and uptake of N, P, K and S by the crop were significantly increased by the addition of S. The increases were more important on the silty clay than on the sandy loam soil. Responses of alfalfa to S were greater than to the addition of P and K. Critical concentrations of S in the crop were found to be 0.10% on the sandy loam and 0.12% on the silty clay soil and appear to be as good an index as N:S ratios to determine S deficiency in alfalfa. Results of this study showed the importance of S fertilization to improve the output of alfalfa on both clay and sandy soils. They suggest that the growing use of concentrated fertilizers containing little S can lead eventually to deficiencies in the plants if other sources of S are not added to normal P and K fertilization.
Effects of Deproteinized Alfalfa Juice Applied to Alfalfa ‐ Bromegrass, Bromegrass, and Corn1
Authors: Ream H. W. , Smith Dale , Walgenbach R. P.
Published: July 2010

Nutrient and dry matter losses when harvesting alfalfa Medicago sativa L.) in humid areas of the U.S. are often 15 to 30% or more. A harvesting system designed to minimize these losses, in which standing alfalfa is chopped in the field, pressed to reduce moisture, and the juice processed to extract protein, has been under investigation. When alfalfa is processed in this manner, the products are a pressed forage that is ensiled, a protein concentrate feed, and deproteinized alfalfa juice (DAJ). The DAJ constitutes over half of the weight of the harvested green alfalfa and must be disposed of to avoid pollution problems. Alfalfa requires a high level of soil fertility to produce maximum yields of forage. DAJ contains relatively large amounts of N and K, as well as smaller amounts of P, Ca, Mg, and micro‐elements. The objective of these field experiments was to determine the effects of DAJ from first crop alfalfa applied as a fertilizer. DAJ was applied at annual rates of 0, 0.625, 1.25, and 2.5 cm to an alfalfa‐bromegrass (Bromus inermis Leyss.) mixture, pure bromegrass, and corn (Zea mays L.). Increased yields of all three crops were obtained with the annual application of 1.25 cm of DAJ. Plant damage and yield reductions occurred to alfalfa and corn when DAJ was applied at rates of 2.5 cm, with only minor damage to bromegrass. Per hectare yields of crude protein were increased by fertilizing with DAJ. Available P and exchangeable K in the soil generally increased with each increment of DAJ applied, and pH was maintained at satisfactory levels as a result of Ca and Mg additions from DAJ. It was concluded that DAJ applied at rates up to 1.25 cm annually can increase production of alfalfa, bromegrass, and corn. Rates higher than this results in injury or damage to plants, the cause of which has not been ascertained.
Seedbed Requirements for Germination of Sandberg Bluegrass1
Authors: Evans Raymond A. , Young James A. , Roundy Bruce A.
Published: July 2010

Sandberg bluegrass (Poa sandbergii Vasey) is an important range forage species in western North America. If a commercial source of seed were available, Sandberg bluegrass would be a valuable species for revegetating range‐lands. Our purpose was to investigate the germination of seeds (caryopses) of Sandberg bluegrass. Seeds were placed in petri dishes and germinated in incubators with constant and alternating temperatures ranging from −6, −4, −2, 0, 2, 5 C, and 5‐degree increments through 40 C. Each of 85 regimes consisted of 16 hours at cold and 8 hours at all possible warmer temperatures. Germination with and without soil and litter coverage was investigated in clay and sandy loam seedbeds in the greenhouse. Also, the effects of simulated litter on germination was investigated in saturated atmospheres in the laboratory. After a 6 months' afterripening requirement was satisfied, Sandberg bluegrass seeds germinated over a wide range of temperatures from −2 to 35 C. Optimum temperatures for germination, those giving maximum germination and not being significantly different (p = 0.01) from each other, varied among years, but 5, 10, and 15/20 C were consistent in this group. Most rapid germination occurred consistently at 15/15 and 15/25 C. Germination on the soil surface was limited unless coverage was provided. Burial greater than 3 cm inhibited emergence. Seeds of Sandberg bluegrass germinating in a simulated litter environment failed to develop roots although coleoptiles elongated normally. Germination requirements will not limit the usefulness of Sandberg bluegrass as a revegetation species as long as the constraints imposed by afterripening and soil or litter coverage are recognized.
Effect of Soil Al Saturation on Nutrient Concentration of Soybean Tops, Roots, and Nodules1
Authors: Sartain J. B. , Kamprath E. J.
Published: July 2010

A small amount of information is available on the effects of Al saturation on the nutrient concentration of different plant components. This manuscript presents data showing the former relative to the soybean [Glycine max (L.) Merr.]. To study the effects of varying exchangeable Al saturation on the concentration of P, Ca, Mg, and Al in the tops, primary roots, lateral roots, and nodules of soybeans, a randomized complete block greenhouse experiment using 12 soybean cultivars and three soil Al saturation levels was established. The soil was a Lynchburg sandy loam (Aeric Ochraquult). Soil Al saturation levels were established by adding various amounts of lime. Soil Al saturation had no effect on the P concentration of the tops. Root P concentration was significantly higher at 81% Al saturation than at 28 and 4%. Nodules had a much higher P concentration than the other plant parts. The calcium concentration of all plant parts was increased with increasing additions of CaCO3. Tops contained the highest Ca concentration and nodules the lowest. Aluminum saturation levels of 81 and 28% did not significantly affect the Mg concentration of the tops and primary roots. The Mg concentration of the nodules decreased as AI saturation decreased due primarily to a dilution effect. Tops and nodules contained approximately twice as much Mg as the root components. Top and root Al concentration was reduced by 53 and 30%, respectively, when the Al saturation was reduced from 81 to 28%. Aluminum concentration of tops was 6, 2, and 8% of the primary roots, lateral roots, and nodules, respectively at 81% Al saturation. Top growth and nodule number increased as the Al saturation was reduced from 28 to 4%, however, very little change occurred in the Al concentration of the tops over this range. Thus, growth responses of soybeans to reduction of soil Al saturation below 28% appears to be due to pH effects and/or Ca supply.
Effects of N, P, Liming, and Mo on Nutrition and Grain Yield of Pigeon Pea1
Authors: Dalal R. C. , Quilt P.
Published: July 2010

Pigeon peas (Cajanus cajan L. (Millsp.)) have considerable potential as a tropical legume. Intensive research work is underway to study the various aspects of pigeon peas production in the Caribbean region. This investigation was undertaken to study the response of N, P, and Mo fertilizers and liming to the grain yield of pigeon peas. The field experiment was conducted on a River Estate loam, a fluventic eutropept, at the University Field Station, Trinidad. The main treatments, N (0, 12, 20, and 30 kg N/ha), P (0, 50, 100, and 250 kg P/ha), and lime (0. 1,250, 2,500, and 5,000 kg CaCO3/ ha) were arranged in blocks in a modified central composite design. The subtreatment, Mo was applied at two rates (0 and 0.25 kg/ha) on two blocks each. Nitrogen fixation, as measured by acetylene reduction assay, nodule weight, dry matter and grain yield, and nutrient uptake by pigeon peas, were observed. Although the fertilizer N significantly reduced N fixation, the total K arid N uptake, grain yield, and Fe and Cu concentration in the plant were not affected. Applied Mo had no effect or any of the plant parameters considered, possibly because it was present in sufficient amounts in soil. Liming significantly increased total Ca, Mg, and P uptake by pigeon peas but significantly decreased Mn concentration in the plant by raising soil pH. Fertilizer P significantly increased dry matter yield (at 6 weeks of crop growth) and total P uptake but significantly decreased Zn concentration in the plant. The tendency for increasing grain yield with higher rates of liming and especially that of P suggested that the optimum rates of P and liming should be further studied.
Measurement of Radish Root Enlargement under Mechanical Stress1
Authors: Kibreab Tadesse , Danielson Robert E.
Published: July 2010

Evaluation of the force that can be exerted by enlarging plant roots, and comparison with that required to deform the soil, will help to identify the influence of soil mechanical properties on plant growth. A growth chamber study was made to evaluate the rate of enlargement of radish (Raphanus sativus L.) roots as influenced by level of applied pressure and to determine the maximum pressure against which the roots could expand.

Special cells were designed to measure the growth rate of the roots against the applied pressure. The procedure involved compressing the storage root by gas pressure against a liquid; and the liquid and root being separated by a membrane. The storage root enlarged against the membrane. The secondary roots extended outside of the pressure cell into an aerated nutrient solution and the leaves were exposed to light and air under controlled conditions of an environmental chamber. Volume change of the roots was periodically determined and after harvest the final volume and weight was obtained. Osmotic potential of root extracts was also determined.

The rate of root enlargement decreased with applied stress. Volume and weight at harvest decreased in a logarithmic manner with applied pressure. The limiting pressure for radish root enlargement was estimated to be about 8.5 bars. Osmotic potential of root extract was closely related to applied pressure. It is suggested that the origin of forces exerted by the root is from higher turgor pressure induced by osmotic concentration of sap.
Potassium Influx Characteristics of Corn Roots and Interaction with N, P, Ca, and Mg Influx1
Authors: Claassen N. , Barber S. A.
Published: July 2010

At K levels usually found in soil solution, K influx characteristics of plant roots can be described by Michaelis‐ Menten kinetics. When only part of the roots are supplied with K, plant uptake of K may be reduced, causing a reduction in K concentration in the plant and this, in turn, may also reduce plant growth. Knowledge of how K distribution in the root zone influences K uptake by the plant is important in developing efficient practices of K fertilization. The objective of this research was to determine the K influx characteristics of corn (Zea mays L.) roots and investigate how supplying only part of the roots with K influences both K influx and N, P, Ca, and Mg influx. Four split‐root experiments were conducted in solution culture. Corn was grown from 7 to 17 days with varying proportions of the root system supplied with K. Reducing the proportion of roots in K reduced K uptake by the plant; however, the K influx of the K‐supplied roots increased up to 2.6 times that of roots on plants where all roots were supplied with K. Presence or absence of K in the solution bathing the roots did not affect root growth in these experiments. Two additional experiments were conducted to produce plants having varying shoot K levels for use in measuring K. influx characteristics. Analysis of all six experiments showed an inverse curvilinear relation between %K in the shoot and maximum K influx into the root (R2= 0.74). Comparison of K influx by K‐supplied‐roots and roots originally in solution without K that were attached to the same shoot indicated the K level in the shoot had a greater effect on K influx than K level of the root. Magnesium influx increased as K concentration in the plant decreased. Magnesium influx was much greater on the K‐absent side than on the K‐present side of the split‐root system. Nitrogen influx was greater on the K‐present than on the K‐absent side.
Sensitivity Analysis of SIMED1
Authors: Schreiber M. M. , Miles G. E. , Holt D. A. , Bula R. J.
Published: July 2010

SIMED, a basic crop growth model for alfalfa (Medicago sativa L.), uses weather data to predict the physiological rates which over time control the accumulation of dry matter in the leaves, stem, and roots. The objective of the work presented was to demonstrate the response of SIMED to two of the most important environmental variables, temperature and solar radiation, and to compare its response to current information on alfalfa growth.

Computer simulations can be conducted to determine how a crop responds to wide ranges and many combinations of environmental factors. Such sensitivity analyses were made using combinations of five temperature and five solar radiation regimes for a period of 6 weeks, representing early spring growth or regrowth following a harvest. Data on herbage yield and crop growth rate indicate the interaction of these two important environmental parameters on alfalfa growth. Plants grown at lower temperatures maintain vegetative growth for longer periods than those grown at high temperatures. Also, radiation levels exert less influence on alfalfa crop growth rates as temperatures increase. These data further illustrate the importance of maturity factors and temperature factors utilized in the physiological rates computed in SIMED.
Amino Acid Composition of Cicer Milkvetch Forage1
Authors: Kaldy M. S. , Smoliak S. , Hanna M. R.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) is a hardy and persistent forage legume that has potential in some regions of western Canada. This study was undertaken to determine the amino acid composition and protein quality of cicer milkvetch in comparison with that of alfalfa (Medicago sativa L.). Samples of both legumes were harvested at the mid‐ to late‐bud stage of growth from a replicated field test on an Orthic Dark Brown Chernozem soil developed on alluvial parent material (Lethbridge loam). Samples were dried at 70 C for 20 hours and then analyzed for 18 amino acids. The limiting amino acid in both legumes is methionine. The protein score, an estimation of protein quality for monogastric animals, was calculated for both forage legumes. It was 67 for cicer milkvetch and 70 for alfalfa relative to 100 for “ideal protein”, as defined by FAO‐WHO Expert Group (1965). Therefore, the nutritional quality of cicer milkvetch protein is similar to that of alfalfa as a supplement to cereal proteins for monogastric animals.
Nitrogen Fertilization of Soybeans1
Authors: Sorensen R. C. , Penas E. J.
Published: July 2010

Nitrogen fertilization of soybeans (Glycine max (L.) Merr.) has given variable results in increasing soybean yields. The objectives of this study were to determine the extent and magnitude of yield increases of soybeans from N fertilization on soils of the Sharpsburg‐Marshall association in Nebraska, and to determine factors to assist in identification of conditions conducive to N induced yield increases. Experimentation with N rates of zero to 224 kg N/ha applied to soybeans was carried out at 13 sites on farmers' fields over a 3‐year period. Yield increases were observed at 9 of the 13 sites. Plant N concentration was increased at 7 sites. Increases in yields were not necessarily related to increase in plant N content; but were closely related to increase in seed size. Where effects were observed, seed yield, plant N content, and seed size were generally linearly related to rate of N application. Regression analyses were performed to determine factors which were related to the occurrence of N response. The factors found were soil pH, soil organic matter content, and yield level.
Tall Fescue Tiller Weights, Green Forage Present, and Forage IVDMD1
Authors: Beaty E. R. , Dobson James W. , Smith A. E.
Published: July 2010

Tall fescue, Festuca arundinacea Schreb., grows well in the upper South, but following initial growth in the spring, forage quality as measured by animal performance is generally low. Forage quality generally declines from spring to summer and data on forage quality in the summer and fall as related to management are badly needed. To characterize forage present after several months of growth this investigation was undertaken.

Tillers were collected in October from an experiment with whole plots having clipping schedules of (A) monthly/year‐long, (B) monthly September to May, (C) monthly December to May, and (D) each time forage reached a height of 15 cm. Split plots were N rates of 56 and 224 kg/ha and split‐split plots were clipping heights of 5 and 10 cm. Data collected were tiller weight, percent green and dead forage of tillers, dry matter digestibility (IVDMD) of each, percent green forage/swards, and tillers/dm2. Weights varied from approximately 0.1 to 0.5 g/tiller and were largely determined by clipping frequency and height. Green forage/tiller averaged 56.1%, and other than height of clipping, was largely independent of all applied treatments other than years. Green forage as a percent of all forage present averaged 29.9. Green forage IVDMD averaged 70.9%, and dead forage 42.4%.

The amount of dead forage and its low digestibility would appear to be the dominant factor in determining the digestibility of tall fescue forage. None of the clipping treatments affected a major reduction in the accumulation of dead forage. Defoliation schemes to be effective in maintaining green forage may require harvesting at lower heights than were used in this study. Additional research would be required to develop improved harvesting methods but opportunities for improvement are sizable and progress should be rapid.
Effects of Cultural Practices on Grain Yield of Irrigated Wheat1
Authors: Day A. D. , Jackson E. B. , Alemu Aschalew
Published: July 2010

Nitrogen is the principal fertilizer element in the production of wheat (Triticum aestivum L.). More effective combinations of N fertilization and cultural practices may further increase the yield and quality of wheat grain. Wheat is sometimes grown on beds in the southwestern U.S. Experiments were conducted at Yuma, Ariz. to study the effects of N fertilizer treatments in combination with methods of planting and row positions on beds, on the yield and quality of wheat grain. Six N fertilizer treatments (34, 17 + 17, 68, 34 + 34, 136, and 68 + 68 kg/ha), two methods of planting (on the flat and on beds), and four row positions on beds (north, south, east, and west) were evaluated.

Flat plantings resulted in higher wheat grain yields than did bed plantings; however, bed plantings produced higher grain volume‐weights. Within planting methods, N fertilizer treatments did not significantly influence grain yields or grain volume‐weights. Grain yield components (number of heads per unit area, number of seeds per head, and seed weight) were similar for both plantng methods. When wheat was grown on beds with an east‐west orientation, the higher rates of N fertilizer resulted in more heads per unit area, more seeds per head, and higher grain yields than did the lower N treatments. The south row position on east‐west beds produced more heads per unit area, more seeds per head, and higher grain yields than did the north row position.

Wheat grown on beds with an east‐west orientation produced more heads per unit area, more seeds per head, and higher grain yields than did wheat produced on beds oriented in a north‐south direction. Wheat responded to N fertilization when grown on both flat and bed plantings during the winter months in the Southwest.
Nitrate and Ammonium Uptake by Rooted Cuttings of Sweet Potato1
Authors: Munn D. A. , Jackson W. A.
Published: July 2010

Nitrogen uptake by rooted cuttings of sweet potato [Ipomoea batatas (L.) Lam.] has not been studied extensively although “slips” (rooted sprouts) are the normal plant part used in commercial propagation. Experiments with rooted cuttings of sweet potato, cultivar ‘Jewell’, were conducted in solution culture to investigate the effects of ambient acidity and the presence and concentration effects of ammonium and nitrate on rates of nitrate and ammonium uptake. Plant stem cuttings were rooted in Hoagland's solution (plus or minus nitrate) then transferred to 980 ml containers of experimental solutions. In experiment I rates of N uptake from 0.1 mM NH4NO3 were measured at pH of 4.5, 5.5, and 6.5. In experiment II rates of N uptake were measured from 0.1 mM solutions with and without the presence of the ammonium in the case of nitrate uptake and vice versa. In experiment III nitrate uptake was measured from 0.1 mM nitrate without ammonium and in the presence of 0.1 mM and 1 mM ammonium. Solutions were sampled periodically and analyzed for nitrate, ammonium, and K. Nitrate uptake rate was decreased by increasing ambient pH while ammonium uptake rate was increased. Presence of ambient ammonium at equimolar concentration decreased rate of nitrate uptake ,∼30% at pH 5.5. However, a tenfold increase in ammonium concentration did not further reduce rate of nitrate uptake although rate of ammonium uptake was doubled. Presence of equimolar nitrate had no effect on rate of ammonium uptake at 0.1 mM ammonium. Efflux of K to initially K‐free solutions was increased by ambient ammonium, but a transition from K efflux to influx occurred without a consistent change in rates of ammonium or nitrate uptake. A suggestion is made that two components of nitrate uptake by sweet potato roots exist, one of which is assumed to be associated with nitrate reductase and inhibited by ammonium.
Segmental Liming of Soil and Its Effect on the Growth of Wheat1
Authors: Kauffman M. D. , Gardner E. H.
Published: July 2010

The use of fertilizers and the leaching of basic cations from the soil by winter rain and irrigation have resulted in the acidification of soils and the need for lime applications to most crops grown in western Oregon. As the cost of spreading lime often exceeds $20.00 per ton, there is a need to examine the feasibility of reducing liming rates through partial mixing of lime with the soil. The effects of mixing 2.2, 6.7, and 11.2 ton/ha of lime with 10, 30, 60, and 100% of the soil volume on the growth of Nugaines wheat (Triticum aestivum L.) were studied using an acid Dayton silt loam soil in a growth chamber. The soil was placed in boxes measuring 30 on wide × 30 cm deep × 1 cm thick with the limed soil being located in equispaced vertical columns. Maximum wheat growth resulted when 6.7 ton/ha of lime was mixed with 30% of the soil. Root growth characteristics in limed and unlimed soil illustrated the chemotropic characteristics of the wheat roots with aluminum toxicity symptoms occurring in unlimed soil and where 2.2 ton/ha of lime was mixed with more than 30% of the soil. The water potential of wheat plants was increased when the root growth was reduced by soil acidity.
Temperature Dependence of Water Uptake by Plant Roots1
Authors: Dalton F. N. , Gardner W. R.
Published: July 2010

The 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

Phalaris (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

A 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

Various 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

Over 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

Rapid 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

The 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

New 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

Liebig'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

The 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

The 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

Soybeans [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.