bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of Festuca rubra L. Seedlings to Ethephon1
Authors: Nittler L. W. , Kenny T. J.
Published: July 2010

Seed characteristics are not distinctive enough for reliable identification of Festuca rubra L. cultivars; therefore, research was conducted to identify seedling characteristics useful for cultivar purity testing. Starting 2 weeks after seeds were planted, seedlings were sprayed three times, at 3‐day intervals, with 700 μl/liter of ethephon (2‐chloroethyl‐phosphonic acid) until the foliage was completely wet. This resulted in development of two distinctly different types of plants. The first had long‐narrow‐leaf blades and the second had short‐wide leaf blades. All seedlings of the Chewing fescue cultivars ‘Cascade’, ‘Highlight’, and ‘Jamestown’ were of the long‐narrow leaf type. In contrast, all seedlings of ‘Rainier’ and 98% of the seedlnigs of ‘Ruby’ red fescue were of the short‐wide leaf type. ‘Arctared’, ‘Illahee’, and ‘Pennlawn’ red fescue developed 74, 36, and 39% short‐wide leaf plants respectively. Even though this technique distinguishes only two types of plants, it was useful in determining accuracy of labeling of Festuca rubra L. seed samples.
Nitrogen Content of Winter Wheat During Growth and Maturation1
Authors: Daigger L. A. , Sander D. H. , Peterson G. A.
Published: July 2010

Preliminary studies showed that winter wheat (Triticum aestivum L.) was losing relatively large amounts of N during the grain formation growth period. In order to further document this N loss, winter wheat plants were sampled at different times and at different locations before and after anthesis until maturity. The objective was to determine the nature and extent of dry matter and N losses that occur during the later stages of wheat development as influenced by N fertilization. While N is translocated rapidly from other plant parts to the grain after anthesis, total N losses ranged from 25 to 80 kg ha−1 in different experiments. These losses occurred during the grain filling period after anthesis. Dry matter and N losses were attributed primarily to the stems where 83 to 87% of dry matter losses occurred and 73 to 75% of the N. Dry matter and N losses from leaves and roots were relatively small. The N losses increased with increasing rates of N application. Plant N losses could account for much of the N losses found in soil N balance studies and certainly influence calculations involving fertilizer N efficiency. Grain protein could be doubled if plant N losses could be translocated instead into the grain.
Seed Grade Effect on Corn Performance1
Authors: Hicks D. R. , Peterson R. H. , Lueschen W. E. , Ford J. H.
Published: July 2010

Small‐sized or ungraded corn (Zea mays.) seed usually costs less than large‐graded seed. Since planters can now uniformly plant ungraded and/or small seed, we conducted trials at Waseca and Lamberton, Minn., in 1973 and 1974 to determine the effect of seed size and shape on performance of early compared to late‐planted corn.

Four seed grades — large round (LR), large flat (LF), small round (SR), small flat (SF), and mixed (M) — were evaluated each year. The M category was an equal mixture of the four grades. In 1973, the single cross hybrid ‘A639 × A638’ was used; in 1974 we used ‘DeKalb XL45A’ and ‘DeKalb XL43.’ Early plant height, early plant dry weight, and tassel dates were recorded at the Waseca location and grain yield was measured at both locations.

Seed grades did not affect corn yields when data were averaged over years, locations, and hybrids. In only one of 12 comparisons was there a seed grade effect with higher yields from graded vs. ungraded seed, from large vs. small seed, and from round vs. flat seed. Seed grade did not affect early plant height or tassel dates. Early plant dry weight for plots seeded with SR and SF seeds was lower than that of plots seeded with LR or LF seeds in 1973; only very small plant dry weight differences occurred in 1974.

Grain yields from the early May planting were higher than from late May planting for all location‐years except Waseca in 1973. Interactions of seed grade with planting dates or hybrids were not statistically significant for three of the four location‐years of the study. Soil temperature at the 10‐cm depth for the 2 weeks post planting was 8 to 10 C colder for early vs. late planting dates, yet yields from SR and SF seed were equal to those from LR or LF.
Effect on Tuber Yield of the Exposure of Yam Tubers to Light1
Authors: Gumbs F. A. , Ferguson T. U.
Published: July 2010

This study was designed to determine the effect of exposure of yam (Dioscorea alata L.) tubers to light on tuber yield, since the emergence of yam tubers from the ground as a result of a compacted or restricting soil layer was found by the authors in previous unpublished studies to be associated with reduced tuber yield. Yam tubers were allowed to develop in the absence of soil, and in a separate compartment from the roots, in specially designed wooden growth boxes. Tubers were allowed to develop in total darkness, in continuous day. light or, with exposure to light for 30 min once per week. Continuous exposure of the developing tubers to daylight significantly reduced tuber yield and caused a large number of small tubers to be produced. Periodic exposure of the tubers to light did not significantly reduce tuber yield nor tuber number compared to tubers developing in total darkness. Exposure of the tuber to light did not significantly affect leaf number but there was some effect on leaf area.
Performance of the Silver‐foil Psychrometer for Measuring Leaf Water Potential in situ1
Authors: Hoffman Glenn J. , Hall Anthony E.
Published: July 2010

Continuous in situ measurements of leaf water potential are often needed in studies of the soil‐plant‐atmosphere continuum. The development of the silver‐foil thermocouple psychrometer has made these measurements possible. The objective of this investigation was to evaluate the performance of the silver‐foil psychrometer under various steady‐state and dynamic conditions. Leaf water potential measurements were made in situ on pinto bean (Phaseolus vulgaris L.) in a controlled‐environment plant chamber where temperature, relative humidity, CO2 concentration, radiation, and photoperiod were precisely controlled.

Typically, the psychrometer will reach equilibrium with an intact leaf 2 hours after attachment. Consistent leaf water potentials are attainable when the leaf temperature varies by as much as 0.25 C/min. This thermal stability is as good as that of any multijunction psychrometer described to date. At radiation levels below 50 Wm−2, leaf water potential readings can be made on unshaded leaves; above this level, the leaf must be shaded to prevent thermal gradients across the leaf and psychrometer.

The silver‐foil psychrometer responded to rapid osciliations in leaf water potential. During oscillations, leaf water potential preceded leaf conductance and transpiration by one‐third of the oscillation period. Net photosynthesis oscillated in phase with leaf conductance, indicating that net photosynthesis is limited by the internal CO2 concentration, even at very low irradiances.
Growth and CO2 Assimilation by Corn as Related to Potassium Nutrition and Simulated Canopy Shading1
Authors: Smid A. E. , Peaslee D. E.
Published: July 2010

Radiant flux density and K are potentially limiting factors in CO2 assimilation by corn leaves having the common property of being more accessible to the upper leaves than to lower leaves of the plant canopy. In this experiment, the effects of K nutrition and shading on growth and CO2 assimilation were evaluated in the absence of confounding factors such as differentials in moisture supply, rooting volume, and availability of other nutrients that often accompany studies having variable plant populations. Corn was grown outdoors in sand cultures receiving solutions containing 15, 45, 135, or 400 μg of K/ml. Plant populations of 33,000, 98,800, and 118,000 plants/ha were simulated by progressive artificial shading of each plant with layers of shade cloth during growth. Rates of CO2 assimilation by selected leaves, yield of dry matter, and leaf concentrations of K were measured at the silking stage. In general, CO2 assimilation rates increased with K levels, with simulated population, and with proximity to the plant top. However, these relationships were complex as evidenced by a significant interaction of K ✕ leaf location and K ✕ population ✕ leaf location. The interactions apparently were associated with increases in leaf K concentrations due to less growth with shading and to movement of K from lower into upper leaves under conditions of K stress. Across all treatment combinations, CO2 assimilation was highly correlated (r = 0.89) with tissue levels of K. Thus, the effects of shading and leaf position were indirect through their influence on the concentrations of K in leaf tissue. Measured assimlation rates (mg/hour) at canopy illumination levels for leaves 5, 7, and 9, when the entire leaf surface was considered uniformly photosynthetic provided indices that were highly correlated (r=0.96, significant at the 0.01 level) with yields of dry matter per plant.
Simulation Model for Nutrient Uptake from Soil by a Growing Plant Root System1
Authors: Caassen N. , Barber S. A.
Published: July 2010

Mathematical models of nutrient uptake by plants are useful for investigating the effect of various soil and plant factors on nutrient flux to plant roots. The objective of this research was to develop a model based on theoretical considerations of the processes of nutrient uptake by plant roots growing in soil and then to test the model experimentally. The soil and plant factors used in the model were to be measured independent of final nutrient uptake.

The model for flux by mass flow and diffusion to the root was patterned after that of Nye and Marriott. The absorption kinetics of the root were assumed to follow Michaelis‐Menten kinetics. The Nye‐Marriott model gives the nutrient concentration at the root with time. From this accumulated uptake per cm2 of root surface with time was calculated. Rate of root growth was assumed exponential for the growth of the young plant. Uptake per cm2 of root with time was combined mathematically with rate of root growth to get total uptake with time by the plant. The present program assumes root hairs do not affect uptake and that roots do not compete for nutrients.

A computer program was written for solution of the mathematical model. The factors required in the model from the soil are: effective average diffusion coefficient, initial nutrient concentration in solution, and buffering capacity. For the plant they are: the relation between nutrient concentration in solution and net influx into the root, water influx, root radius, initial root length, and rate of root growth.

The model was tested for measuring K uptake by corn (Zea mays L.) from eight different soil‐K combinations. The corn was grown in a growth chamber and K uptake was measured for the period of plant growth from 4 to 10 and 13 days. The calculated uptake, y, was correlated with observed uptake, x, by the equation y = 0.155 + 1.566 × (R2 = 0.87) where y and are μmoles of K/plant. Calculated uptake was overestimated by about 50%, possibly because competition occurred between roots for soil K and K was not absorbed by the root as fast at night as in the day.

The model should be useful for investigating the principles of nutrient absorption by plant roots from soil which can be used for developing more efficient systems of fertilizer application.
Yield and Nitrogen Utilization by Rice as Affected by Method and Time of Application of Labelled Nitrogen1
Authors: Reddy K. R. , Patrick W. H.
Published: July 2010

Recent increases in the cost of N fertilizer make it important to examine methods of improving the utilization of fertilizer N by lowland rice (Oryza sativa L.). The objective of the present investigations was to compare the effects of different methods and times of N application on yield and utilization of N by lowland rice. Field experiments using labelled fertilizer N were carried out during 1974 and 1975 utilizing different times and methods of application of ammonium sulfate on small field plots (2.32 m2). Fertilizer N was applied either by deep placement at the beginning of the season or at one or more times during the growing season as surface application. Relative contributions of native soil N and fertilizer N sources to plant uptake were followed during the growing season, and total uptake of native soil N and fertilizer N by rice was determined at harvest.

Highest grain yields were obtained where all of the N was applied early in the growing season or where part of the N was applied in early season and part applied no later than mid season. Late season application of part of the nitrogen was not as effective. In 1974, recovery of fertilizer N (in grain and straw) was highest in the plots receiving all N by deep placement, while in 1975 split application (half at early season and half at mid season) gave greatest N utilization. For the 2 years, the recovery of fertilizer in grain and straw ranged from 33 to 61% of applied N. Rice plants derived more fertilizer N during the early part of the growing season with the rate of uptake decreasing as the season progressed. Recovery of fertilizer N calculated from labelled N data showed lower values, compared to the recovery of fertilizer N estimated by a method based on total N uptake difference between the plots receiving N and the untreated plots. More native soil N was taken up by the crop from the plots receiving fertilizer N than from the check plots in 1974, but there was little difference in uptake in 1975.
Photosynthesis, Transpiration, and Leaf Elongation in Corn Seedlings at Suboptimal Soil Temperatures1
Authors: Barlow E. W. R. , Boersma L. , Young J. L.
Published: July 2010

The physiology of plant response to low soil temperatures is not well understood. Laboratory studies were conducted to examine the relative sensitivities of rates of leaf elongation, net photosynthesis, and transpiration and the leaf water potential of corn seedlings (Zea mays L. ‘Pride 5’) to decreasing temperature. These parameters were simultaneously monitored, as the soil temperature was decreased from 28 to 10 C at about 4 C increments. The different soil temperatures were imposed during a 10‐hour period on 14‐day‐old plants with seven exposed leaves growing at a 27.5 C air temperature, a 55% relative humidity, and a light intensity of 753 μE/m2/sec.

Any decrease of the soil temperature below 28 C decreased the leaf elongation rate. This was attributed to restricted water uptake which lowered the plant water potential and to the temperature decrease of the shoot apical meristem region. Leaf elongation ceased at the plant water potential of —9 bars due to decline of leaf turgor pressure.

Neither transpiration nor net photosynthesis was reduced significantly until the plant water potential reached —12 to —13 bars. Increases in both stomatal and internal resistances to CO2 diffusion coincided with the decreased net photosynthesis at low plant water potentials. Suboptimal soil temperatures affect corn seedling growth primarily by decreasing leaf elongation.
Influence of Three Soil‐water Regimes on Root Porosity and Growth of Four Rice Varieties1
Authors: Das D. K. , Jat R. L.
Published: July 2010

A better understanding of the growth response of rice (Oryza sativa L.) to waterlogged soil conditions is desirable. The objective of this study was to measure the influence of soil water regime on root porosity, growth, and nutrient content of four varieties of rice at various dates after transplanting.

Four rice varieties (‘IR8’, ‘Padma’, ‘BC6’, and ‘IR22’) were grown under three soil water regimes (continuous flooding, alternate flooding, and no flooding) in a greenhouse on a clay loam soil. Root porosity, growth of plants and nutrient (N, P, K, Ca, and Mg) content of shoots were determined at four different plant ages (30, 60, 85, and 110 days after transplanting).

Root porosity was greatest in plants grown with continuous flooding. Porosity of roots in all four varieties reached maximum values between 30 and 60 days and then started to decline. Padma and BC6 had higher root porosities than IR8 and IR22. High root porosity was associated with greater root length, increased dry weight of roots and shoots, and higher nutrient content in shoots.
Influence of Simulated Early Lodging upon Soybean Seed Yield and its Components1
Authors: Woods S. J. , Swearingin M. L.
Published: July 2010

Early lodging of soybeans [Glycine max (L.) Merr.] in highly productive environments has been observed throughout the midwestern United States. It has been established that soybean seed yields are decreased when severe lodging occurs sometime prior to physiological maturity. The objective of this 2‐year field study was to examine the effect of plant growth stage at the time of lodging on soybean seed yield and its primary components; pods per plant, seeds per pod, and seed size.

The study was conducted at Tipton, Ind., in 1972 on a Crosby silt loam soil (member of the fine mixed mesic family of Aeric Ochraqualfs) and at Lafayette, Ind., in 1973 on a Chalmers silty clay loam soil (member of the fine loamy mixed mesic family of Typic Haplaquolls.) Two Group II soybean cultivars (‘Wells’ and ‘Corsoy’), representing distinct degrees of lodging resistance, were subjected to a simulated lodging treatment at 2‐week intervals in the early reproductive growth stages. Controls were: a) plants supported by a 10 ✕ 10 cm plastic grid system, and b) no treatment or support which permited natural lodging to occur. Depending upon the time of simulated lodging, seed yields of both cultivars were reduced from 11 to 32% in 1972 and from 12 to 22% in 1973. The reproductive growth stage, R5, normally reached during the first 2 weeks of August in central Indiana, was found to be the most critical time for lodging to occur. Neither seeds per pod nor seed size was significantly reduced when lodging occurred at stage R5. The reduction in yield was due almost entirely to a reduced number of pods per plant, especially those on the central stem. When lodging occurred after flowering had commenced apical dominance was lost, resulting in lateral branches assuming central stem characteristics.
The Brown‐Rosenberg Resistance Model of Crop Evapotranspiration Modified Tests in an Irrigated Sorghum Field1
Authors: Verma Shashi B. , Rosenberg Norman J.
Published: July 2010

The Brown‐Rosenberg (1973) resistance model was modified to simplify its calculation and increase its usefulness for estimating evapotranspiration. The model requires inputs of net radiation, air temperature, and vapor pressure and canopy and boundary layer resistance. The first three of these parameters are measured. In the modified version canopy resistance is estimated from a functional dependence on irradiance. The boundary layer resistance is estimated from a functional dependence on windspeed. The modification was tested in an irrigated sorghum (Sorghum bicolor Moench, cv ‘Rs 633’) field at Mead, Neb.

The model predictions generally agreed to within 10%, on both an hourly and daily basis, with direct lysimetric and Bowen ratio‐energy balance measurements of evapotranspiration from the sorghum.

The Brown‐Rosenberg model in its original and modified forms is useful when neither direct nor remotely sensed crop canopy temperature data are available and when there is need to evaluate the impact on evapotranspiration of several of the aforementioned environmental and crop parameters.
Disk Meter for Rapid Estimation of Herbage Yield in Grazing Trials1
Authors: Bransby D. I. , Matches A. G. , Krause G. F.
Published: July 2010

A rapid, indirect, in situ technique for making accurate estimates of pasture dry matter (DM) yield would be of great benefit in grazing trials to insure sound grazing management and meaningful interpretation of results. A disk meter, designed to estimate pasture DM, was constructed and evaluated on tall fescue (Festuca arundinacea Schreb.) pastures which were grazed by yearling steers. Fifty paired observations of bulk‐height readings with the disk meter and DM yields were used to establish the regression relationship between meter reading and yield. Separate calibrations were made for four different size disks. Area and diameter of disks, respectively, were 0.2 m2, 0.50 m; 0.4 m2, 0.71 m; 0.6 m2, 0.87 m; and 0.8 m2, 1.0 m. Relative to a constant weight per unit area of 5 kg/m2, actual disk weights were 1, 2, 3, and 4 kg, respectively, for the 0.2, 0.4, 0.6, and 0.8 m2 disks. Also, additional calibrations were made for the 0.2 m2 disk with weights of 2 and 3 kg. Correlation coefficients (r) for bulk‐height and DM yield ranged from 0.79 to 0.94, and all were significant at the 1% level of probability. Neither size nor weight of disks had any significant effect on residual standard deviation or r, although the heavier weights did alter the regression coefficient (b). Tall fescue pastures changed from reproductive growth in June to a vegetative phase in September, and this also affected b values. This study indicates that the disk meter can be useful for monitoring herbage‐on‐offer in grazing experiments which have a pure stand of tall fescue.
Influence of Seed Size on Yield and Yield Components of Rape1
Authors: Major D. J.
Published: July 2010

This study was initiated because previous research had indicated that large rapeseed produced higher yielding plants than small rapeseed and because this had not been studied in the rape‐growing area of western Canada. Seed of two rape species (Brassica campestris L. cultivar ‘Span’ and B. napus L. ‘Zephyr’), was screened to provide lots of small, medium, and large seeds (expressed as mg/seed), and grown in the field at Lethbridge, Canada, with an ungraded sample. A randomized complete block design was used with 4 replications in 1974 and 8 in 1975. The soil was a Brown Chernozemic (Typic Haploboroll) silty clay loam (Lethbridge series) developed on alluvial‐lacustrine material. In a laboratory study, 500 seeds of each cultivar were weighed and date of germination recorded. In a greenhouse study, 200 seeds of each cultivar were weighed individually and dates of emergence recorded. Thirty days after planting, 50 plants were chosen at random, transplanted, and grown to maturity. The remaining plants were dried and weighed for an estimate of seedling vigor. Planted seed size in the field did not significantly affect plant height, final population density, pods per plant, seeds per pod, seed size, or seed yield. In the laboratory and greenhouse studies, some small seeds produced smaller or slower growing plants. Seed size was positively related to seedling vigor but not consistently related to final seed yield or its components. Grading rapeseed, therefore, would be of little or no economic value to the farmer.
Potential of Sunflowers for Silage in Double‐Cropping Systems Following Small Grains1
Authors: Sheaffer C. C. , McNemar J. H. , Clark N. A.
Published: July 2010

Sunflowers (Helianthus annus L.) are a drought tolerant and high dry matter producing crop. Due to these properties, sunflowers might find use as a silage crop in double‐cropping systems where moisture supplies are limited. The objective of this study was to evaluate cultural practices and sunflower cultivars which would enhance forage quality and yield.

Oil and confectionary sunflower cultivars were handplanted in a factorial experiment at populations of 71.8, 143.6, and 287.2 thousand plants/ha in 1973; and 86.1, 172.1, and 344.3 thousand plants/ha in 1974. Fertilizer was applied at rates of 56‐49‐93 (low) and 112‐98‐186 (high) kg N‐P‐K/ha. The experiment was conducted in the field on a Chester silt loam (fine‐loamy, mixed mesic Typic Hapludults) in 1974 and an Elsinboro loam (fine‐loamy mixed mesic Typic Hapludults) in 1975. In a second field experiment conducted from 1973 to 1975, sunflowers, corn (Zea mays L.), and sorghum (Sorghum bicolor L. Moench) were no‐tillage planted into barley (Hordeum vulgare L.) stubble using conventional farm machinery following the removal of the small grain. Populations of sunflowers, corn, and sorghum were 128, 46, and 366 thousand plants/ha, respectively. In 1973 and 1974, the experiment was located on a Delanco silt loam (fine‐loamy, mixed mesic Aquic Hapludults) and in 1975 on a Chester silt loam (fine‐loamy, mixed mesic Typic Hapludults).

Confectionary cultivars produced more dry matter/ha than oil cultivars. All sunflowers had low forage quality. Dry matter yields were greater at higher populations up to 344.4 thousand plants/ha, but at higher populations lodging occurred. Fertilizer application had no effect on silage yield or forage quality. In the second experiment sunflowers were found to be as productive as corn and matured in a shorter period of time.

Results from these experiments indicate that sunflowers can be competitive with corn in terms of dry matter production when planted in a double‐cropping system; however, low‐forage quality is a limiting factor in potential use of sunflowers for silage in the northeast.
Sampling Distribution of Nitrates in Irrigated Fields1
Authors: Reuss J. O. , Soltanpour P. N. , Ludwick A. E.
Published: July 2010

The object of this study was to determine the components of variability encountered in sampling farmers' fields for soil nitrates. This information is required for formulating recomendations for sampling plan and intensity. Twenty‐four irrigated farm fields in northeastern Colorado and Western Nebraska were sampled on 61 ✕ 61 m grids. One soil core was taken in 30‐cm increments from each grid to a depth of 120 cm. Duplicate cores were obtained from each third grid to allow determination of within grid variability. The laboratory‐induced variability was also estimated. The results indicated that within and among grid standard deviations increased as the means increased. The standard errors of laboratory determinations (subsampling plus analytical errors) also increased as the means increased. A logarithmic transformation produced histograms that approximated a normal distribution better than the untransformed values. Therefore, the geometric mean represented the nitrate content of a sampled field better than an arithmetic mean. Regression analyses showed that geometric mean could be estimated by multiplying the arithmetic mean of nitrates by 0.91. The nitrate values changed significantly in parallel and perpendicular directions with respect to the crop rows in a nonpredictive manner, indicating that a systematic sampling plan will lead to a more representative sample than a random sampling plan. By separation of a spatial component of variance it was calculated that for the average field sampled to a depth of 120 cm, 7% of the area had nitrate levels below 67% of the geometric mean while on 9% of the area the nitrates exceeded 150% of the geometric mean. In the most variable 10% of the fields 20% or more of the area had nitrate levels below 67% of the geometric mean while on 21% of the area the nitrate exceeded 150% of this value. The laboratory standard deviation was consistently 5% of the mean, indicating a lognormal distribution. With this laboratory precision doubling laboratory variability will not significantly increase the confidence interval of the geometric mean at a low level of sampling intensity, but it will have much larger effect as sampling intensity increases. The number of cores required for a 90% confidence interval of about ± 15% and ± 26% of the geometric mean was calculated to be 82 and 20 per field, respectively.
Water Relations of Cotton. II. Continuous Estimates of Plant Water Potential from Stem Diameter Measurements1
Authors: Huck Morris G. , Klepper Betty
Published: July 2010

Information about plant water potential is often required at very frequent intervals in studies with small numbers of plants. Two methods for inferring plant water potential continuously and nondestructively are described for cotton (Gossypium hirsutum L.) plants. Both methods require continuous monitoring of stem diameter and occasional destructive sampling of tissue for determination of water potential by conventional methods. The computed results are compared with experimental measurements of plant water potential.

The shrinkage modulus method requires calibration points obtained from conventional water potential measurements in early morning and mid‐afternoon in order to relate a measured diameter change to a corresponding measured water potential difference. The dynamic flux method requires an initial estimate of tissue conductivity (between 0.7 and 1.4 ✕ 10−6 cm2 sec−1 bar−1 for cotton) and a half‐time for xylem‐phloem equilibration (30 min for cotton). These parameters are used to calculate the stem xylem water potentials which would have been required to bring about measured changes in stem diameter. Both techniques permit plant water status to be monitored continuously in either field or laboratory experiments with minimum destructive sampling of tissue; once accurate parameter estimates are available, the dynamic flux method requires less frequent field calibration.
Element Concentration of Forage and Non‐soluble Cell Wall Fraction of Coastal Bermudagrass1
Authors: Edwards J. H. , Jackson W. A. , Beaty E. R. , McCreery R. A.
Published: July 2010

Elements contained in forage, the primary feed of beef cattle, are extremely important in animal nutrition. However, lack of knowledge concerning the release of elements in the forage during digestion has hampered effective research on the biological value of forage elements. The research reported here was concerned with measuring some of the major elements contained in (a) coastal bermudagrass (Cynodon dactylon L. Pers.) and (b) in the non‐soluble cell wall fraction of this forage. The experiments were done in the field on a Cecil sandy loam soil (a Typic Hapludult). Coastal bermudagrass fertilized with 0, 165, 336, and 504 kg/ha of N and clipped at 2, 4, 6 and 8 weeks after first clipping was analyzed for Ca, K, Mg, Mn, Na, Fe, Zn, and Cu. The nonsoluble cell wall fraction of the same forage samples was analyzed for Ca, K, Mg, Mn, Cu, and Zn. The cell wall extraction removed about 90% of the Cu and from 97 to 99% of the Ca, K, Mg, and Mn contained in the forage. However, from 80 to 100% of the Zn contained in the forage remained in the non‐soluble cell wall fraction. Increasing N rates increased the K, Mn, and Cu concentration in the forage, but did not influence the concentration retained in the non‐soluble cell wall fraction. Clipping frequency and growth cycle did not affect the concentration of the elements in the forage or the non‐soluble cell wall fraction.
Nitrate‐N Percolation through Irrigated Sandy Soil as Affected by Water Management1
Authors: Smika D. E. , Heermann D. F. , Duke H. R. , Bathchelder A. R.
Published: July 2010

Fertilizer N has been considered as a source of groundwater pollution because of NO3‐N mobility in soil. This study was conducted on a Torripsammet soil (Valent fine sandy loam) during three consecutive growing seasons to determine the magnitude and differences in NO3‐N losses below corn (Zea mays L.) roots from two different, but current, farmer‐used fertilizer management practices. Three farmer‐owned and ‐operated center pivot sprinkler irrigation systems (designated A, B, and C) near Crook, Colo. were used each year. Nitrate‐N percolation losses were measured in water samples collected at 150 cm below the soil surface in vacuum extractors located in a line 91, 182, and 372 m for the pivot in each field. The A, B, and C systems were managed so that 4.8, 2.5, and 10.2% respectively, of the growing season water (irrigation plus rain) percolated to the 150‐cm depth. Three‐year average annual NO3‐N collected in the extractors was 30.4, 19.0, and 59.7 kg/ha for the A, B, and C systems, respectively. Nitrate‐N and water percolating to the 150‐cm depth were highly correlated (r = 0.95), with each centimeter of water carrying an average 10.2 kg/ha NO3‐N. Average annual total dry matter production for the systems, in the same order, was 20,763, 21,876, and 18,858 kg/ha, respectively, and was negatively related to NO,‐N percolating to the 150‐cm depth (r = −0.99), showing that production was highly related to NO3‐N loss. Total dry matter production decreased 65 kg/ha for each kg/ha of NO3‐N percolating to the 150‐cm depth. Soil NO3‐N changed very little from spring to fall in each of the systems but the soil under the A and B systems contained more than 250 kg/ha NO3‐N to a depth of 180 cm, whereas soil under the C system contained only 20 kg/ha to this depth.
Plowsole Placement of Fertilizer for Soybeans and Response to Tillage of Plowsole1
Authors: Camper H. M , Lutz J. A.
Published: July 2010

In Virginia, most of the soybean [Glycine max (L.) Merrill] are grown on the light‐textured soils of the Coastal Plain. Because of tillage operations, a traffic pan has developed over the years in some of these soils. This pan may reduce water infiltration and root penetration with a subsequent reduction in crop yields. During droughty periods, the traffic pan may be beneficial by reducing the percolation rate of water through the rooting zone. At any rate, the effect of the pan on soybean production is unknown and should be investigated. Also, the effect of incorporating P and K into the traffic pan on the production of soybeans should be determined.

In order to evaluate the importance of the traffic pan in soybean production, an experiment was conducted for 6 consecutive years on Sassafras sandy loam (Typic Hapludults; fine‐loamy siliceous, mesic) at Warsaw, Va. Comparisons were made of rates of P, K, and/or lime tilled and not tilled into the traffic pan after the surface 15‐cm soil layer had been removed.

Tillage of the plow sole increased plant height in 1 year, reduced it in 2 years, but the average heights for 6 years with and without tillage were identical. Tillage did not affect maturity but increased yields in 1 of 6 years. Soybean seed weight, shattering, and pod and stem blight were unaffected by tillage but purple seed stain was increased by tillage.

Fertility treatments had a significant effect on plant height, maturity, yield, seed size, disease, and shattering.
Growth and Nutrient Uptake by Rice in a Flooded Soil under Controlled Aerobic‐Anaerobic and pH Conditions1
Authors: Jugsujinda Aroon , Patrick W. H.
Published: July 2010

A number of studies have shown that soil redox conditions and pH are important factors in determining the growth and nutrient uptake of lowland rice (Oryza sativa L.), but no studies report the interaction between these two conditions. A study was made of growth and nutrient uptake of rice plants grown in soil suspensions maintained under either aerobic or anaerobic conditions and at several pH values.

Different redox and pH conditions caused marked differences in the uptake of some nutrients and smaller differences in growth of rice. Fe and Zn uptakes were especially affected by redox‐pH interaction. Uptake of the two elements decreased markedly as the pH was increased. The two elements reacted differently to redox conditions, however, with Fe showing greater uptake and Zn showing lower uptake under anaerobic conditions. P uptake was affected more by pH than by redox conditions, with a general decrease in uptake resulting as pH increased. Increasing pH also resulted in lower uptake of labelled ammonium‐N with redox conditions showing little effect.
Screening Corn for Al Tolerance Using Different Ca and Mg Concentrations1
Authors: Rhue R. Dean , Grogan C. O.
Published: July 2010

Cations such as Ca and Mg can protect roots from the toxic effects of Al. However, little use of this fact has been made in screening for Al tolerance. This study was undertaken to determine the effects of Ca and Mg concentrations in screening solutions on the toxicity of Al in roots of corn inbreds (Zea mays L.). Two‐day‐old corn seedlings were grown for 12 days in dilute nutrient solutions containing 0.25 mM Al. Treatments consisted of Ca or Mg at concentrations of 0.5, 1.0, and 2.0 mM. The pH was adjusted to 4.60 initially with no further adjustments. The large solution: root volume ratio resulted in only small pH changes during the 12‐day screening. These small pH changes had little or no effect on the toxicity of Al in corn roots. Increasing the concentration of Ca decreased the severity of Al toxicity in roots of corn inbreds. However, there were marked differences among inbred lines in the ability of their roots to grow in these screening solutions at all levels of Ca. For example, roots of the inbred lines W153R and Va17 were susceptible and tolerant, respectively, to Al at all three levels of Ca, whereas A239 showed symptoms of severe Al toxicity at 0.5 mM and 1.0 mM Ca but produced good root growth at 2.0 mM Ca. Thus, a wide range in tolerance to Al was observed in these screening solutions by varying the concentration of Ca. At equal concentrations, Mg was as effective as Ca in protecting corn roots from Al. This technique could be utilized for screening species where a knowledge of the range in tolerance among individual genotypes is desired.
Yield, N, and S Content of Corn as Affected by N and S Fertilization on Coastal Plain Soils1
Authors: Rabuffetti Armando , Kamprath Eugene J.
Published: July 2010

Since there is an increasing use of high analysis fertilizers containing very little sulfur, two field experiments were conducted to evaluate the S requirements of corn (Zea mays L.) grown on Coastal Plain soils under present management practices. The soils used were Goldsboro loamy sand (Aquic Paleudult) and Wagram loamy sand (Arenic Paleudult). Experiments consisted of a complete factorial arrangement of nitrogen rates (which varied from 56 to 224 kg/ha) and S rates (which varied from 0 to 66 kg/ha). Gypsum was used as the source of S. The hybrid ‘Pioneer 3369A’ was grown at both sites. Nitrogen fertilization had the largest effect on yield and N content of corn grain. The effects of S fertilization depended on the N supply. With 56 or 112 kg N/ha, S additions had no effect or depressed grain yields and N content. With 168 or 224 kg N/ha, S fertilization significantly increased grain yields and N content of corn grain. Total amounts of S accumulated by corn varied from 7 to 20 kg/ha depending on soil type, N, and S rates. Nitrogen fertilization had a larger effect than S fertilization in determining total S accumulation in grain and stover. This study indicated that additions of 30 to 60 kg S/ha to adequately N‐fertilized corn crops are likely to improve grain yield and quality of corn grown on Coastal Plain soils, particularly on those having deep sandy A horizons.
Evaluation of Wild Oat Straw as a Soil Erosion Retardant Using Simulated Rainfall1
Authors: Singer Michael J. , Blackard John
Published: July 2010

Soil cover is recognized as an important factor in soil erosion control. This study was made to determine the qantitative relationship between cover percent for one cover type and soil loss under simulated rainfall. Data from this experiment are used to calculate a cover coefficient for wild oat (Avena barbata Brot.) straw similar to the “C” factor in the Wischmeier Universal Soil Loss Equation (USLE). The R, K, L, S, and P factors were kept constant during the experiment.

A rainfall simulator was used in the laboratory to produce 30 min rainfall events of 76 mm/hour (3 in/hour) intensity on soil material at 9% slope. Under these conditions, wild oat straw significantly reduced sediment loss at cover levels of 50% or more. A significant reduction in runoff volume was observed for cover percentages exceeding 90%. A parabolic regression model Y = 158.4 − 0.051X − 0.014X2 which describes the relationship between Y sediment loss and X percent cover (0 to 100) was highly significant R2 = 0.81. The effect of the straw was to 1) reduce splash, 2) reduce soil crust formation, 3) block sediment movement, 4) delay runoff initiation, and 5) reduce total runoff loss. A cover coefficient (CC) can be calculated as a ratio of soil loss under any straw cover percent to soil loss under no straw cover. The relationship needs to be tested for other cover types before it is used with cover types different than straw mulch, or substituted for the C factor of the Wischmeier equation.
Critical Zinc Levels Related to Early Growth and Development of Determinate Soybeans1
Authors: Ohki K.
Published: July 2010

Evidence of Zn deficiency in determinate soybeans [Glycine max (L.) Merr.] has appeared. Critical deficiency levels of Zn relating leaf concentration and growth are needed to provide reference values associated with maximum growth. The objective was to determine reference values needed to aid in the Zn fertilization program. Soybeans were grown in the greenhouse for 41 days in modified Hoagland solution with total Zn rates of 0, 5, 10, 20, 50, 100, 200, 300, 400, 500, 700, and 1,000 μg/liter Zn. Leaf blades were sampled at harvest and analyzed for Zn by atomic absorption. The critical nutrient deficient levels for Zn were 15, 15, and 14 μg/g dry weight in blades 1 (young developing leaf), 2, and 3 (recently matured leaf), respectively. For purposes of evaluating the Zn status, the recently matured leaf (blade 3) is suggested as the tissue to sample. The critical Zn levels in blade 4 and 5 were 17 and 21 μg/g, respectively. Blade 1 had the sharpest transition zone. Zinc deficiency reduced top and root dry weights, plant height, flower number, and branching; however node development was not affected by Zn deficiency stress. Symptoms similar to Mn toxicity were induced by very low Zn supply. High Mn concentrations were associated with low Zn in blade 3 of plants supplied with 5 μg Zn/liter.
Effect of Soil Mixtures and Irrigation Methods on Leaching of N in Golf Greens1
Authors: Mitchell W. H. , Morehart A. L. , Cotnoir L. J. , Hesseltine B. B. , Langston D. N.
Published: July 2010

Utilization of applied N by ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) is of special interest because of the cost and availability of N and the potential environmental problems resulting from its deep percolation. The influence of soil mixtures, irrigation systems, and N sources on N leaching was studied in experimental, though functional, golf greens from 1973 to 1976. Sprinkler irrigation was compared with subsurface irrigation using porous irrigation tubing constructed from spun‐bonded olefin. Soil mixtures contained from 60 to 80% sand and variable amounts of silt loam topsoil, calcined clay and humus. Nitrogen treatments included activated sewage sludge, ureaform, ammonium nitrate, 30% N solution, anhydrous ammonia and nitrapyrin. Nitrogen solutions were applied through the subsurface irrigation system while other N carriers were surface applied. Each soil × irrigation treatment was underlain by a drainage line placed in pea stone at a depth of about 46 cm. Water samples were collected periodically from drainage lines and analyzed for NH4‐ and NO3‐N.

Nitrogen leached primarily as NO3‐N with a reduced rate of loss associated with slow release N sources and the onset of low seasonal temperatures. Even though about 75% of the added was NH4‐N, N solution (30% N) applied through the subsurface irrigation system caused a sharp increase in NO3‐N in the drainage water. Anhydrous ammonia with or without nitrapyrin reduced NO3‐N leaching losses for 1 to 2 weeks but had little effect on the average NO3‐N concentration over a 47‐day period.

Subsurface irrigation stimulated turfgrass growth in bands about 20 cm wide located above the irrigation lines. Appearance of growth bands was associated with low temperatures and increased levels of NO3‐N in proximity to the irrigation lines. Banding was most apparent in soil mixtures containing low levels of residual soil N and absent when turfgrass was adequately fertilized with N.
Analysis of Potato Growth under Differing P Regimes. I. Tuber Yields and Allocation of Dry Matter and P1
Authors: McCollum R. E.
Published: July 2010

High rates of P fertilization for potatoes (Solarium tuberosum L.) over many years have resulted in significant increases in total and extractable soil‐P reserves. While fertilization practices for other crops grown in rotation with potatoes reflect both plant demand and soil‐test P, many producers continue to fertilize potatoes with little regard to crop requirements nor to existing soil‐P levels. If neither potatoes nor crops grown in rotation with them require such high rates of directly‐applied P, a considerable saving in fertilizer costs could be realized. This hypothesis was tested in two field experiments (on a Typic Umbraquult, fine‐loamy, mixed, thermic soil) designed to measure tuber yields and trace patterns of dry matter and P accumulation by ‘Pungo’ potatoes in response to row‐applied fertilizer P[FP (1969) = 0, 24, 48, and 72 kg/ha; FP (1970) = 0, 28, and 56] on soil with 35, 66, and 110 kg of extractable soil P/ha. The latter objectives were accomplished by weekly samplings and appropriate analyses of tops and tubers during tuber bulking. When soil P was low (35 kg) or medium (66 kg), row‐applied P increased yields by 38 and 22%, respectively; but no response to fertilizer P was obtained if initial soil P was high (110 kg). At tuber initiation, P concentration in whole plants ranged from 0.20% under severest deficiency to 0.45% under optimal nutrition; it dropped to less than 0.20% at harvest, regardless of treatment. On low‐P regimes (SP < 66, FP = 0) rates of dry matter and P accumulation were still positive at 84 days after emergence; but plants on other treatments had lost most of their leaves—and many haulms were dead—at 79 days. At tuber initiation, plants with and without row‐applied P had accumulated 20 and 10%, respectively, of their 72‐day total P. Dry matter at tuber initiation was about 10% of the 72‐day total for all treatments. About 75% of the total accumulated P and 70‐75% of total dry matter was in tubers at harvest. While massive P applications to these low P soils are needed to make them productive, my results suggest that even high‐demand crops like potatoes require relatively modest amounts of row applied P to maintain maximal productivity once the initial deficiency is eliminated.