bluuebunny/crossref_metadata_2025 huggingface dataset:
Indexes of Sulfur Deficiency in Alfalfa. I. Extractable Soil SO4‐S1
Authors: Westermann D. T.
Published: July 2010

Sulfur deficiencies occur on many of the undeveloped agricultural soils found in the mountain valleys of the western United States; however, the majority of the S soil‐test correlation studies have been conducted on leached and weathered soils. Identification of S deficiency on alfalfa (Medicago sativa L.) growing in three mountain valleys permitted the collection of S soil‐test correlation data for these undeveloped soils. This paper reports the relationships found between extractable soil SO4‐S levels and the response of alfalfa to S fertilization.

Soil samples were taken from 13 experimental sites before active plant growth commenced in the spring in 30‐cm depth increments to 92 cm. Soil SO4‐S was extracted by water, 0.1 M LiCl, and 0.032 M KH2PO4 and measured by the methylene‐blue reduction method. Significant correlations were obtained between the SO4‐S extracted by all three extractants from the 0‐ to 30‐cm soil layers and relative forage yields and total S uptake by the first harvest of alfalfa at early bloom. Critical soil SO4‐S levels of 3.0, 3.0, and 4.0 ppm in this soil layer were found when extracted by water, LiCl, and KH2PO4, respectively. Inclusion of KH2PO4‐extractable SO4‐S to 92 cm did not improve the curvilinear regression relationships, nor did inclusion of percent soil organic matter. Increasing the soil:extractant ratio from 1:2 to 1:3 did not significantly change the amount of SO4‐S extracted by the KH2PO4 solution. The 0.1 M LiCl solution is recommended for extracting SO4‐S from soils with relatively small amounts of absorbed SO4‐S.
Effect of Lime, Sulfur, and Molybdenum on N2 Fixation and Yield of Dark Red Kidney Beans1
Authors: Janssen K. A. , Vitosh M. L.
Published: July 2010

Symbiotic nitrogen fixation by the Rhizobium‐legume association of fieldbeans does not provide sufficient nitrogen for optimum yield under Michigan growing conditions. Consequently, an average of 44.8 kg/ha (40 lbs/A) of supplemental nitrogen is applied to these legume crops each year. This results in a sizeable investment for the growers and also increases the potential for N loss by leaching and runoff.

The purpose of this study was to determine whether lime, S, and/or Mo might be limiting N2 fixation and bean yield of dark red kidney beans (Phaseolus vulgaris L.) in the field. Two acid sandy soils 40.2 km (25 miles) apart, N‐S direction, suspected of being deficient in S and Mo, were selected for this study. Lime rates (0, 2,800, and 5,600 kg/ha), S rates (0 and 45 kg/ha), and Mo rates (0 and .07 kg/ha) were compared in a factorial design. Symbiotic nitrogen fixation was measured by the acetylene reduction assay. Soil samples were collected and bean yields were recorded.

Sulfur increased nitrogen fixation (acetylene reduction activity) nearly 60%. The lime and Mo treatments had little influence on nodule activity. The average yield of beans was increased 10% by the 2,800 kg/ha lime rate and 26% by the 5,600 kg/ha lime rate. The Mo seed treatment reduced yield 7%. Yield response to S was 26% at the zero lime rate, 12% at the 2,800 kg/ha lime rate, and 10% at the 5,600 kg/ha lime rate. Soil test results showed that lime increased the amount of available S in the soil.

These data suggest that lime and S are limiting bean yield on certain acid sandy soils in Michigan. It also appears that where soils are S deficient symbiotic nitrogen fixation is being restricted.
Soil and Plant Factors Influencing Accumulation of Dry Matter in Burley Tobacco Growing in Soil Made Acid by Fertilizer1
Authors: Sims J. L. , Atkinson W. O.
Published: July 2010

A field experiment was conducted to elucidate factors influencing dry matter accumulation in tobacco (Nicotiana tabacum L. cv. ‘Burley 21’) growing in soil whose acidity was increased by fertilizer. Relatively large amounts of commercial fertilizers commonly are added to soil in burley tobacco production and knowledge of the effects of such additions on dry matter accumulation may lead to increased yields of cured leaf and improved usability of cigarette smoke. Samples of soil and plant material were obtained at varying dates during the growing season and were chemically analyzed. Varying soil pH levels were obtained from applications of N as ammonium nitrate at rates of 0, 90, 180, and 360 kg N/ha.

The addition of N fertilizer to Maury silt loam soil with an initial pH of 6.2 significantly increased exchangeable Mn and decreased soil pH, exchangeable Ca, and concentrations of available MoO4−2 and H2PO4−. Exchangeable Mg and K were little affected by N fertilizer at any sampling date. Much of the decrease in exchangeable Ca may be attributed to leaching with NO3− by excessive rainfall early in the season. Evidence indicated some delay of nitrification of NH4+ in plots fertilized at the 360 kg N rate.

Nitrogen fertilization of tobacco increased concentrations of Mn in leaves, but levels were not judged to be excessive for normal growth. A tendency existed for concentrations of Ca and Mg to be decreased by N at 40 days after transplanting and concentrations were near deficiency levels for Ca at this date, although exchangeable soil Ca levels exceeded 1500 ppm. In contrast, at 77 days and at harvest, N fertilizer significantly increased plant concentrations of Ca and Mg. Molybdenum concentrations in leaves from high N plots were only 20 to 50% of those in plots unfertilized with N. Concentrations of MoO4−2 in leaves from fertilized plots were near deficiency levels for most of the growing season. The data suggested interaction of MoO4−2 and Mn, and of Mn with Ca and Mg within the plant.

Correlation and regression analyses revealed significant relationships of soil measurements near transplanting and dry matter at 40 days and of plant constituents and dry matter at all dates. Results indicated the depression of dry weight by N fertilizer noted previously during early growth was the direct or indirect result of fertilizer‐induced soil acidity.
Cation‐Anion Balance of Field‐Grown Crops. II. Effect of P and K Fertilization and Soil pH1
Authors: Banwart W. L. , Pierre W. H.
Published: July 2010

Plant species differ in their cation‐anion balance, but the organic anion content (C‐A), excess‐base (EB), and EB/N ratio of a given plant species may vary considerably when grown under different environmental conditions. Nitrogen fertilizers, for example, increase the organic anion content of certain crop plants and alter their effect on soil acidity by reducing the EB/N ratio. The primary objective of this study was to determine the effect of a wide range in amounts of P and K fertilizers and of soil pH on the cation‐anion balance of several crop species grown under field conditions.

Leaf and plant samples of corn (Zea mays L.) and plant samples of alfalfa (Medicago sativa L.) and oats (Avena sativa L.) were taken for analysis from plots of several field experiments that had received a wide range in amounts of P and K or of ground limestone.

In general, phosphorus and potassium fertilizers decreased the C‐A and EB contents of corn leaves, oats, and alfalfa. The effect of P and K additions in reducing C‐A and EB seemed less where they had the least effect in increasing crop yields; and in some experiments, K additions had little or no effect on C‐A, EB, or yield. Limestone additions on two soils, resulting in pH changes from below 6.0 to above 7.6, increased C‐A and EB of corn leaves slightly in one experiment, but had no significant influence on C‐A, EB, or yield in the other.

Potassium fertilizers lowered the EB/N ratio of corn leaves. However, K and P fertilizers and limestone additions resulted in only very slight changes in the EB/N ratio of corn, oats, and alfalfa plants; and no change in EB/N was observed in several of the comparisons. Thus, on the basis of their effect on the EB/N ratio of the crops harvested, P and K fertilizers and soil pH should not alter the plant effect on the base status of soils.
Crop Recovery and Nitrification of Fall and Spring Applied Anhydrous Ammonia1
Authors: Chalk P. M. , Keeney D. R. , Walsh L. M.
Published: July 2010

To evaluate the relative agronomic efficiency of and potential NO3, pollution by fall and spring applied anhydrous NH3, N uptake and yield response by corn, and detailed sampling of the NH3, bands were conducted. Nitrogen significantly increased grain yield and N uptake by corn (Zea mays L.) on a Plano sil (0.216% N) and a Pella loam (0.447% N) in south central Wisconsin. There were no differences between fall and spring application of N. Crop recovery of applied N depended on soil type and rate of application, and at most amounted to 40% of the N applied. Depending on rate of application, from 68 to 86% of the fall‐applied NH3, was nitrified before mid‐May. Nitrite accumulated within both fall and spring applied bands, the highest concentrations being detected in early spring within fall applied bands. Persistence of NO2 was more prolonged on a neutral than on a slightly acid soil. Accumulation of NO2 must be considered undesirable because of possible phytotoxicity and losses through biological or chemical denitrification, and fall application appears to offer a great potential for these processes to occur.
Use of Soil Sterilants to Defoliate and to Terminate Growth of Irrigated Cotton1
Authors: Gardner B. R. , Troutman J. L.
Published: July 2010

The conventional approach of applying harvest‐aid chemicals to leaves of luxuriantly growing cotton plants, Gossypium hirsutum L., often results in partial or top defoliation followed by secondary growth. This study was initiated to test a new concept of cotton defoliation. The application of 61 liters/ha of a 32.7% aqueous solution of sodium methyl dithiocarbamate in the irrigation water to luxuriantly growing cotton plants resulted in termination of plant growth and complete leaf defoliation. Defoliation was completed within 10 days from time of application with full size, immature bolls opening in about 20 days. There was no evidence of plant regrowth after 75 days. The cotton plants were ideally suited for mechanical harvest. Although the chemical is too expensive to be economically feasible, we suggest that luxuriantly growing cotton plants can best be defoliated by destroying the conductive tissues of the root and/or lower portion of the stem and that further testing of this concept be initiated.
Relation of Soil Water Potential to Stomatal Resistance of Soybean1
Authors: Brady R. A. , Goltz S. M. , Powers W. L. , Kanemasu E. T.
Published: July 2010

This research was undertaken to establish a meaningful relationship between stomatal resistance of soybeans and soil water potential. The main objectives were to establish this relationship and examine some of the factors affecting measurements of stomatal resistance of soybeans. Stomatal resistance in the soybean leaves was measured with a stomata porometer and plotted against soil water potential.

A definite relationship was determined in two consecutive growing seasons between the soil water potential and stomatal resistance. Adaxial stomatal resistance increased rapidly when soil water potentials decrease to near −4 bars.

It was found that stomatal resistance of upper canopy leaves were not affected by the physiological stage of growth of the whole plant. The difference in stomatal resistance of well‐irrigated and nonirrigated soybeans was distinct, and stomatal resistance showed promise in determining irrigation schedules.
Effects of Soil pH on Forage Yield, and Chemical Composition of Sorghum and Millet1
Authors: Walker Milton E. , Marchant Warren H. , Ethredge W. Jerome
Published: July 2010

Millet [Pennisetum typhoides (Burm.) Stapf and Hubbard] yields more forage than sorghum [Sorghum bicolor (L.) Moench] does in certain areas of the Southern Coastal Plain. Yield differences are associated with low soil pH in some instances. Experiments were conducted to elucidate the relation between soil pH, forage yield, and selected chemical composition of sorghum and millet.

Management practices and plant nutrient applications were applied in a manner and at a level shown by other experiments to be adequate. The forage from both crops was analyzed for N, P, K, Ca, Mg, Al, and Mn. Upon completion of the experiment, soil samples were analyzed for P, K, Ca, Mg, Al, and Mn and soil pH was measured. Millet forage yield was unrelated to the soil pH in the pH range used. Sorghum forage yield increased 2,000 kg/ha when soil pH increased from 5.2 to 5.6. The concentration of Mg in sorghum forage was found to be greater at soil pH of 5.8 and above, while the concentration of Al and Mn decreased at a soil pH ≥ 5.2. The concentration of Ca increased more at soil pH ≥ 5.8; while the concentration of Al and Mn decreased at a soil pH ≥ 5.2. The concentration of Ca increased in millet forage at a soil pH ≥ 5.2; while P and Mg content increased at a soil pH ≥ 5.8.

Based on this study, it is recommended that liming acid soils in the Southern Coastal Plain to increase soil pH increases sorghum forage yields and improves the mineral nutritional quality of both sorghum and millet forage.
Nitrogen‐Sulfur Relations in Soft White Winter Wheat. II. Initial and Residual Effects of Sulfur Application on Nutrient Concentration, Uptake, and N/S Ratio1
Authors: Rasmussen P. E. , Ramig R. E. , Allmaras R. R. , Smith C. M.
Published: July 2010

Although sulfur is routinely applied over much of the limited‐rainfall area of the northwestern United States, present diagnostic criteria for determining the need and frequency of S fertilization of white winter wheat [Triticum aestivum ssp. vulgare (Vill., Host) and T. aestivum ssp. compactum (Host)] are not highly successful. Our objective was to evaluate the initial and residual availability of applied S by investigating a) S uptake and distribution in wheat and b) the success of S concentration and N/S ratio as diagnostic criteria.

Sulfur uptake, S concentration, and N/S ratios were compared with yield to measure S response over a period of 7 years after S application to a typical S‐deficient soil. Four rates of S (0, 17, 34, and 68 kg/ha) were applied as gypsum in factorial combination with four rates of N (0, 45, 90, and 180 kg/ha) as ammonium nitrate. Residual S effects were then evaluated in three subsequent wheat crops grown in a wheat‐pea (Pisum sativum L.) rotation with optimum N fertilization.

Sulfur uptake and concentration in the first wheat crop was proportional to the rate of S applied, but accumulated primarily in vegetative tissue when present in excess of the amount required for grain protein. Uptake from residual S was much lower than uptake from the fertilizer application and S levels in grain were maintained at the expense of S in straw. Excellent residual availability of S (i.e., two wheat crops for a 17 kg/ha application) was attributed to the low amount of S needed for the additional grain yield (< 1 kg S/ha), recycling of substantial quantities of S in straw residues, and negligible leaching of S.

The initial N fertilization significantly increased S uptake from the S source by increasing both S concentration and dry matter. Nitrogen applied without S increased dry matter but not S concentration. In contrast, S fertilization had little effect on N concentration in grain and straw and influenced N uptake only through its effect on dry matter production.

Grain yield responses to S were poorly correlated with S concentration or N/S ratio in tissue because of the inconsistency of S accumulation in the plant‐parts and the dominating effect of N on yield. Decreased grain yield in wheat responding to S was associated with < 0.12% S in grain, <0.08% S in mature plants, and with N/S ratios > 16 in mature plants.
Evapotranspiration of Dryland Barley with Different Plant Spacing Patterns1
Authors: Luebs R. E. , Laag A. E. , Nash Phyllis
Published: July 2010

Standard row, grid, and paired‐row plant spacing patterns were compared at the same plant population for their effect on barley (Hordeum vulgare L.) leaf area index (LAI), crop canopy, evapotranspiration (ET), and yield under dryland conditions in the field. The minimum unit area of equal plant population density for all spacing patterns was 240 cm2. Crop canopy was defined as the percentage of soil surface covered by the crop when viewed from a direction normal to the surface. Crop canopy and LAI were lowest for the grid spacing pattern, largely because of less tillering. During the vegetative phase with adequate water availability, the barley crop planted in the paired‐row pattern had the highest LAI but intermediate crop canopy. Evapotranspiration was more closely related to crop canopy as achieved with these spacing patterns than to LAI. Slightly greater ET during the first two‐thirds of the growing season by barley in the standard row pattern resulted in more water stress and lower ET later in the season, but this did not reduce grain yield below that for the other spacing patterns.
Response of Two Peanut Cultivars to Irrigation and Kylar1
Authors: Gorbet D. W. , Rhoads F. M.
Published: July 2010

With improved yields resulting from new cultivars and production practices, irrigation of peanuts (Arachis hypogae L.) is receiving increased attention. The objective of this study was to measure the response of two peanut cultivars to soil‐water management in the plow layer and to the growth regulator Kylar (succinic acid 2, 2 dimethylhydrazide).

‘Florigiant’ and ‘Florunner’ cultivars, representing Virginia and runner market types, respectively, were grown on Typic Paleudult and Arenic Paleudult soils. Tensiometers were utilized to schedule irrigations for treatments in which soil moisture tension in the plow layer (20 cm) was maintained below 1 bar. In one treatment, plant wilt at midday was used as an indicator for irrigation. A plant growth regulator, Kylar, was applied in some treatments to reduce vegetative development.

Total pod production of both cultivars was increased with irrigation, especially in dry seasons. During seasons of high rainfall and/or favorable distribution of rainfall, pod loss in the soil at harvest was excessive, resulting in a net yield reduction under conditions of low soil‐water tension (30 to 60 cbar). Treatments irrigated at low soil moisture tension produced significant yield increases and greater dollar value per metric ton in the dry 1972 season. The growth regulator, Kylar, and irrigation resulted in the greatest peanut yields when averaged across years (52 and 55 q/ha for Florigiant and Florunner, respectively). Kylar reduced vine growth all 3 years, but reduced dollar value per metric ton (grade) in some cases.
Production of Rye and Ryegrass Forage with Sulfur‐coated Urea and Ammonium Nitrate1
Authors: Dunavin L. S.
Published: July 2010

The need for fertilizer materials which provide particular elements to plants over a long period of time is well known. This reduces the expense of numerous applications. In the production of forage from grasses, N is an element which needs to be continually available but is one which is normally rather quickly dissipated. Sulfur‐coated urea (SCU) has given promise as a slow‐release source of N and the need to compare it with other sources of N, such as ammonium nitrate (AN), for various crops has arisen.

This investigation was conducted to determine the value of the use of SCU as an alternative to AN in the production of forage from rye (Secale cereale L.) and ryegrass (Lolium multiflorum Lam.). SCU compositions having dissolution rates of 10, 20, and 30% (dissolution in water in 7 days) were applied at annual rates of 100, 200, and 400 kg of N/ha. AN was also used at these same rates of N. AN was tested at one and three times of application. Data was obtained for two seasons with five monthly harvest dates in each season. For the 2‐year period, the highest yield (P < .05) was obtained from AN fertilization at a 400 kg/ha rate of N when three applications were made. The next highest yields were obtained when 400 kg/ha of N was applied as SCU with no difference between the dissolution rates. For the 2‐year period, there was no significant difference in the total recovery of N from forage receiving 400 kg/ha of N from AN and that fertilized with SCU at either the 30 or 30% dissolution rates. Monthly forage yield and N recovery differences among rates and between the fertilizer sources were evident.
Cannabinoid Profile and Elemental Uptake of Cannabis sativa L. as Influenced by Soil Characteristics1
Authors: Coffman C. B. , Gentner W. A.
Published: July 2010

The consumption of Cannabis products (marihuana) derived from domestic and foreign sources persists in the United States despite its illegality and health hazards. The objectives of this investigation were: 1) to evaluate relationships between soil and plant elements, cannabinoids, and growth of Cannabis sativa L., and 2) to evaluate the practicality of using chemical analysis of Cannabis products to determine their geographic origin. Knowledge of geographic origin is useful to governmental agencies investigating illicit narcotic traffic.

Cannabis sativa L. was grown on 11 different soils for 45 days in the greenhouse. Soils differed significantly in 15 measured elements and pH. Plants were grown from seed of Afghan origin. The following cannabinoids were extracted and measured from leaf tissue: cannabicyclol (CCC), cannabidiol (CBD), Δ9‐Tetrahydrocannabinol (Δ9THC), and cannabinol (CBN). Fifteen elements measured in leaf tissue and correlated with soil and cannabinoid measurements. Soil pH was negatively correlated with leaf concentrations of Mn, Fe, Zn, and S. Extractable soil Mg was negatively correlated with N, Δ9THC and CBD concentrations in leaf tissue (p < 0.05). Plant height was negatively correlated with Δ9THC concentration, suggesting enhancement of the narcotic principle of marihuana when grown under stress. Extractable soil P2O5 was negatively correlated with CBD concentration while extractable soil Zn was positively correlated with CCC concentration. Several correlations between soil and plant characteristics having potential value for determination of geographic origin of marihuana were elucidated. However, environmental, harvesting, and analytical procedures used by different workers which do not conform to one another could result in changes in the soil‐plant correlations reported herein. Thus, additional studies are required before determination of the geographic origin of Cannabis products by foliar analysis becomes feasible.
Germination of Wheat and Alfalfa Seeds as Affected by Some Soil Urease Inhibitors1
Authors: May P. B. , Douglas L. A.
Published: July 2010

The use of urease inhibitors has been proposed as a means of controlling the rate of urea hydrolysis in soils. However, application of enzyme inhibitors to soils may affect other soil processes in addition to urea hydrolysis.

The purpose of this study was to determine whether soil urease inhibitors would affect the germination of wheat (Triticum aestivum L.) and alfalfa (Medicago sativa L) seeds. Soil urease inhibitors included in this study were; catechol, p‐benzoquinone, 2,5‐dimethyl‐p‐benzoquinone, hydroquinone, 1,2‐napthoquinone, benzohydroxamic acid, and phenylmercuric acetate.

In the initial study, 0.003, 0.015 or 0.03 g of each inhibitor was applied to wheat or alfalfa seeds that had been placed on moist paper towelling. Germination percentage was recorded after incubating the seeds for 8 days at 20 C. At the highest rate of inhibitor application all inhibitors caused a noticeable decrease in the germination percentages of seeds of both species. Only catechol and 1,2‐napthoquinone had no effect on seed germination at the low rate of 0.003 g/plate. In a second experiment, seeds were germinated in moist soil in the presence of inhibitors applied at the rates of 100, 50, or 10 ppm of soil. No compounds affected germination when applied at 10 ppm of soil and at the higher rates, only 2,5‐dimethyl‐p‐benzoquinone caused severe reduction in the germination percentages recorded for both species.
Yield Response to Soil Warming: Agronomic Crops1
Authors: Rykbost K. A. , Boersma L. , Mack H. J. , Schmisseur W. E.
Published: July 2010

Waste heat appears in the form of warm condenser cooling water from power generating plants. It has been proposed to use this water with temperatures ranging from 25 to 40 C for warming soils by pumping it through buried pipes. Experiments were conducted to determine the effect of warming soils in this manner on the growth rates and yields of several crops. The proposed system was simulated with parallel electrical heating cables buried 92 cm deep and 183 cm apart. Heat source temperatures ranged from 35 to 38 C during the growing period. Heating increased the average temperature of the soil layer from 0 to 100 cm deep by about 10 C. The average temperature increase of the 0 to 10 cm soil layer was < 3 C. The crops tested were field corn (Zea mays L.), sudangrass (Sorghum vulgare sudanese), sorghumsudangrass hybrid (Sorghum bicolor L.), and tall rescue (Festuca arundinacea).

The yield increases, expressed as percentages of yields obtained on unheated plots, ranged from 19% for tall rescue to about 50% for sudangrass. The yield increases varied widely from year to year for the same crop. The highest yield increases occurred during years when the yields on unheated plots were lowest. Correlations between yield increases and yields from unheated plots were highly significant. A yield decrease occurred only with tall fescue during the summer. Soil heating appears to be most effective when climatic conditions and management factors are limiting. The effects of higher soil temperatures on growth rates were greatest in the early spring.
Improved Water‐use Efficiency in Dryland Grain Sorghum by Promoted Plant Competition1
Authors: Blum A. , Naveh M.
Published: July 2010

Field experiments evaluated the hypothesis that competition‐suppressed plant growth might improve the water‐use efficiency and yield of dryland grain sorghum [Sorghum bicolor (L.) Moench.] grown on stored soil moisture.

Plant competition was promoted by planting sorghum in double rows (DR), i.e., 40 cm between rows within a pair, and 160 cm between row pairs, as compared with regular‐spaced rows (RR) (100 cm between rows), with the same number of plants/unit area.

The effect of competition in DR was observed, beginning at 20 to 35 days after emergence, in reduced total stover dry matter/plant, and reduced tillering and LAI, as compared with the RR arrangement.

In two out of four experiments, grain yield was significantly increased by DR configuration, as compared with RR, and was associated with a reduced number of panicles/plant, and an increased number of grains/panicle and 1,000‐grain weight.

Leaf water potential prior to the grain‐filling period did not differ between treatments. During the grain‐filling period, leaf water potential was significantly lower in RR than in DR plants. Leaf diffusive resistance prior to the grain‐filling period was significantly higher in DR than in RR plants, during late afternoon. During grain‐filling period, leaf diffusive resistance was significantly higher in RR than in DR plants, beginning at noon.

During the boot to full bloom growth stages, less soil water was extracted in DR than in RR plots. Consequently, more soil water was available in DR plots during the grain‐filling period.
Nutrient Content of Sorghum Leaves and Grain as Influenced by Long‐Term Crop Rotation and Fertilizer Treatment1
Authors: Brawand Hans , Hossner L. R.
Published: July 2010

The objective of this research was delineation of longterm crop rotation and fertilizer influence on levels of N, P, K, Ca, and Mg in sorghum leaves and grain. Continuous farming practices may introduce gradual departures in the prevailing initial biological, chemical, and physical characteristics of the plant root environment, thereby altering soil productivity characteristics. These chnges, as they alter nutrient composition and yield of crops, can be documented from long‐term field experiments maintained under continuous farming and fertilization programs. The treatments featured continuous versus rotations of grain sorghum (Sorghum vulgare), wheat (Triticum aestivum) and cotton (Gossypium hirsutum) with and without fertilizer. Most treatments have been applied annually for over 20 years. Fertilization of grain sorghum predominantly consisted of N and P at rates of 45 and 20 kg/ha, respectively, in field plots on a Houston Black clay soil (fine montmorillonitic thermic family of Udic Pellusterts).

Apart from some selective positive influence on sorghum leaf N, leaf P and leaf K, the crop rotational effect on leaf composition was considered inconclusive. Generally, crop rotation did result in larger grain production with fertilized as well as with unfertilized sorghum.

Levels of sorghum leaf N, leaf P, leaf K, and leaf Ca were mostly higher in plants receiving fertilizer than in checks. Grain sorghum leaf N, leaf P, leaf Ca, and leaf Mg percentages decreased, increased, or remained nearly constant during the interval from plant booting to half bloom. Sorghum leaf K percentages generally decreased from booting to half bloom. Fertilizer increased grain protein percentage and grain yield. Yet, high rates of fertilizer are not usually recommended in the Texas Blackland Prairie because of frequent soil moisture depletion prior to or at grain formation.

Sorghum leaf composition, grain protein level and grain yield portrayed noticeable response to applied cattle manure plus fertilizer N and P. As the measurable response to fertilizer P was below expectation, its significance on longterm maintenance of balanced soil fertility remains an important consideration.
Changes in Total N, Organic Matter, Available P, and Bulk Densities of a Cultivated Soil 8 Years after Tame Pastures were Established1
Authors: White E. M. , Krueger C. R. , Moore R. A.
Published: July 2010

Cultivated Williams loam (Typic Argiboroll, fine‐loamy, mixed) soils in north‐central South Dakota were sampled after pastures were established and 8 years later so that the effect of the pastures on soils could be studied from analysis in the laboratory. Pastures were seeded to Russian wildrye (Elymus junceus Fisch.), crested wheatgrass (Agropyron desertorum (Fisch.) Schult.), or a mixture of smooth bromegrass (Bromus inermis Leyss.), intermediate wheatgrass (Agropyron intermedium (Host) Beauv.), and a pasture alfalfa (Medicago sativa L.). Soil N and bulk densities increased as available P decreased in the 8 years. The soil organic matter increased under all pastures, but it was small. The increases in organic matter, decreases in available P, and increases in saturated‐clod bulk densities were different in the various pastures. Total N and organic matter increased about 0.001 and 0.02% per year, respectively, which is slower than the rate of decrease caused by cultivating the original grassland soils.
Nitrogen Concentrations of Cotton Leaves, Buds, and Bolls in Relation to Age and Nitrogen Fertilization1
Authors: Thompson A. C. , Lane H. C. , Jones J. W. , Hesketh J. D.
Published: July 2010

Our plant growth models depend on a nitrogen economy in the plant as a limit for the initiation of new organs as well as the slowing of growth or abscission of plant organs. To improve our N‐balance model, we needed better information about possible organ age effects for plants growing under different N‐levels.

Leaf and fruit N and N‐effects upon morphology at four preplanting soil nitrogen levels of 0, 67, 134, and 201 kg N/ha were studied in cotton (Gossypium hirsutum) in the field and greenhouse. Three sets of leaves and fruit were monitored for N‐content throughout the season. N‐concentration in leaves from each N‐treatment decreased (6 to 2%) as the season progressed. Regression analysis of these data indicated that the N‐concentration dilution was not linear with time. Seventy‐nine percent of the variation in N‐concentration could be accounted for by N‐application rate and time in growing season. Regression analysis of fruit data indicated that the dilution of N‐concentration (4.5 to 1.5%) was linear with N‐application rate. However N‐concentration dilution was significant for young fruit from older plants. In plants grown both in the field and greenhouse at the four N‐levels, the flowering rule time values (days/flower) increased with lower N‐rates. There was a delay in maturity of floral buds in the high N‐treatment plants, but no delay in the time required for boll set.
Comparison of Irrigation Schedules Based on Pan Evaporation and Growth Stages in Winter Wheat1
Authors: Prihar S. S. , Khera K. L. , Sandhu K. S. , Sandhu B. S.
Published: July 2010

Most of the schedules suggested by researchers for irrigating wheat (Triticum aestivum L. em Thell) are not sufficiently simple to be adopted by farmers in general. Recently a more practicable approach based on the ratio of a fixed amount of irrigation water (IW) to pan evaporation, PAN‐E, (cumulative evaporation from US Weather Bureau class A pan less rain since previous irrigation) has been suggested. Several workers have advocated irrigation of wheat at definite growth stages. One possibility of further improving the water use efficiency could be a combination of these two approaches. We compared, in a two year field study, IW/PAN‐E ratios of 0.75 and 0.9 for scheduling irrigation to winter wheat irrespective of growth stage with (i) a combination of these ratios with growth and (ii) irrigation at five growth stages.

IW/PAN‐E of 0.75 irrespective of growth stage produced as much grain yield as irrigation at five growth stages. But the former, as an average, received 12 cm less irrigation. There was no gain in the yield by combining the IW/PAN‐E with growth stages. These results indicate that irrigating wheat, sown after a presowing irrigation, on the basis of IW/PAN‐E, irrespective of growth stage, offers a practical means to economize irrigation water without reduction in yield.
Establishing Reed Canarygrass on Low Fertility Soil1
Authors: Kroth Earl M. , Meinke Louis , Dudley Richard F.
Published: July 2010

Pasture production can be increased on low fertility soils in North Missouri by topdressing fertilizers on stands of reed canarygrass (Phalaris arundinacea L.). The optimum banded starter fertilizer to obtain these stands was determined by comparing experimental N, P, and K mixtures applied in kg/ha composed of: (N‐0, 17, 34) (P‐0, 15, 30, 45) (K‐0, 14, 28, 42) in all combinations. Fertilizers were banded 2.5 cm below and 2.5 cm beside reed canarygrass seed planted 0.6 cm deep in three August and two April plantings during 1971–1974. Stands were evaluated visually using a scale of 0 to 10, and by forage yields. Results showed that a fertilizer mixture composed of N and P carriers applied to give 17 kg/ha N and 15 kg/ha P, banded 2.5 cm below and 2.5 cm beside the seed would give optimum results for both August and April seedings.
Absorption of Trimethylselenonium by Plants1
Authors: Olson O. E. , Cary E. E. , Allaway W. H.
Published: July 2010

The trimethylselenonium ion (TMSe+) is an important urinary Se metabolite. As an aid to evaluating its role in the natural cycling of Se, these plant studies concerning its uptake from soils or from nutrient solution and its metabolism were undertaken. Wheat (Triticum aestivum L.) and alfalfa (Medicago sativa L.) were grown on Dalton and Lima loam soils (coarse — silty, mixed, mesic Aeric Fragiaquert and fine‐loamy mixed, mesic Glossoboric Hapludalf) containing no added Se or added Na2SeO3, Na2SeO4, or TMSe+, with and without a 4‐month storage period prior to planting. Wheat only was grown in a separate experiment on Cecil (a clayey, haolinitic, thermic Hapludult) and Lakeland (thermic, coated Typic Quartzipsamment) soils containing similar amounts of these added Se compounds. The Se contents of the wheat and alfalfa grown on the TMSe+‐treated Lima and Dalton soils were much lower than for the Na2SeO3 or Na2SeO3 treatments, barley exceeding that for the untreated control. With the Cecil and, especially, the Lakeland soils the Se content of the wheat was considerably above that for the untreated control, greater than that for the Na2SeO3 treatment, but considerably less than that for the Na2SeO4 treatment. TMSe+ added to nutrient solutions was readily absorbed and translocated to the leaves and stems but not the grain of wheat. At concentrations providing 3 mg Se/liter or more of nutrient solution, it caused signs of toxicity resembling those caused by similar concentrations of Se as Na2SeO4. Studies on the chemical form of the Se in the wheat suggested that, except for some volatilization, the TMSe+ absorbed was not metabolized.
Differential Susceptibilities of Weeping Lovegrass Strains to an Iron‐related Chlorosis on Calcareous Soils1
Authors: Foy C. D. , Voigt P. W. , Schwartz J. W.
Published: July 2010

Observations of weeping lovegrass (Eragrostis curvula (Schrad.) Nees) strains growing on a calcareous soil at Woodward, Okla., indicated differing degrees of susceptibility to a chlorosis tentatively attributed to Fe deficiency. To test this hypothesis thoroughly, we grew 41 strains in greenhouse pots containing a mixture of calcareous Millville and Quinlan soils, both of which were known to produce Fe‐deficiency chlorosis in several crops. The final pH of the mixture was 7.8. Weeping lovegrass strains differed widely in susceptibility to chlorosis and in top growth on the calcareous soil mixture. Chlorosis‐susceptible strains had higher Mn concentration and lower Fe:Mn ratios than did the chlorosis‐resistant strains. Some chlorosis‐ susceptible strains seemed to have unfavorable Fe:Cu and Fe:Zn ratios. Differential chlorosis was not directly related to concentrations of Fe, P, Zn or Cu in plant tops. Chlorosis susceptibility seems to be related to inhibited Fe metabolism, rather than to reduced Fe uptake by plants. Several experimental strains of weeping lovegrass were far more resistant to Fe deficiency chlorosis than current cultivars used. Results suggest that superior cultivars of this species can be bred for adaptation to calcareous soils in which Fe‐deficiency chlorosis is a problem.
Influenced of N Nutrition on Total N, Nitrate, and Carbohydrate Levels in Soybeans1
Authors: Brevedan R. E. , Egli D. B. , Leggett J. E.
Published: July 2010

A better understanding of the effects of varying the N supply to the soybean (Glycine max (L.) Merrill) be obtained by studying, after treatment, the resultant changes in N and carbohydrate levels in the various plant parts. Greenhouse and field experiments were conducted to determine the effect of varying the N supply to the plant during flowering and pod‐filling on the dry weight, total N, NO3‐, and the total available carbohydrates. The greenhouse experiment was conducted in a gravel culture hydroponics system with 5 meq NO3‐/liter m the nutrient solution. Some plants were shifted to 12.5 and 18.0 meq NO3‐/liter at initial bloom and maintained at these levels until maturity, while others were exposed to the high NO3‐ levels only until the end of bloom. Treatments in the field consisted of 168 kg N/ha as NH4NO3 applied at initial bloom, at the end of bloom, or at both times (total of 336 kg N/ha). Increasing the N supply to the plant during the period from initial bloom increased the dry weight of the vegetative plant parts at the end of bloom and at mid‐podfill. The effect was much greater in the greenhouse than in the field. Increasing the N supply to the plant also increased the concentration of N and NO3‐ in the vegetative tissue at the end of bloom; differences in N and NO3‐ were also apparent at midpodfill although the magnitude was not so great. The concentration of total available carbohydrates in the vegetative tissue decreased when the N supply to the plant increased. Treatment effects were similar in the greenhouse (non‐nodulated) and in the field (nodulated) experiment. A previous paper reported that yield was increased by increasing the N supply to the plant during flowering and pod set, primarily as a result of an increase in seed number. The increase in yield was associated with increased tissue levels of N and NO3‐ and decreased levels of total available carbohydrates. The data demonstrate the importance of high tissue levels of N during the period of flowering and podset.
Grass Tetany Potential of Tall Fescue as Affected by Soil O21
Authors: Elkins Charles B. , Haaland Ronald L. , Hoveland Carl S. , Griffey Wallace A.
Published: July 2010

Grass tetany, a metabolic disorder in cattle on pasture, has been related to low Mg and high K levels in tall rescue (Festuca arundinacea Schreb.) and other forages. These mineral imbalances in forages and most cases of tetany usually occur in late winter and early spring when soil O2 is low because of frequent precipitation and low evaporation rates.

In a greenhouse experiment, gas mixtures were used to study the effect of soil O2 levels on Mg and K in forage of four tall rescue entries. Magnesium content of these entries was 0.25% or less at 2% soil O2 but ranged from 0.35 to 0.44% at 21% soil O2. Entries differed in Mg content at 21% but not at 2% soil O2. Potassium content ranged from 2.1 to 2.7% at 2% soil O2 and from 2.9 to 3.7% at 21% soil O2. Root length was greatly reduced by low soil O2 levels and was the only root characteristic we studied related to Mg and K uptake.

A replicated field experiment was used to study the effect of soil drainage on forage Mg content of ‘Kentucky 31’ tall rescue. Forage from poorly drained areas had Mg contents of 0.18 to 0.25%, whereas nearby well‐drained areas produced forage with 0.27 to 0.40% Mg.

Our results showed that low soil O2 levels and, therefore, poor soil drainage may be important factors in production of tetanogenic tall fescue forage. Draining wet areas, removing animals from poorly drained pastures, and maintaining legumes on these problem areas should be helpful practices for preventing tetany.
A Procedure for Determining Numbers of Experimental and Sampling Units1
Authors: Geng S. , Hills F. J.
Published: July 2010

Researchers often sample experimental units to measure certain characteristics, for example, percent protein in grain or percent sucrose in plant roots. Thus, in planning such experiments, one of the first questions encountered is how many samples and replications should be used.

A procedure is suggested for using the non‐central F distribution to determine the number of replications and samples needed per experimental unit. The method requires the specification of the treatment effects to be detected, the probability of type I and type II errors, and an estimate of population variance. Sugar beet (Beta vulgaris L.) trials, employing sampling for sucrose content of roots, are used to illustrate the procedure in completely randomized, randomized complete blocks, latin square, and split‐plot designs. It is shown that fewer samples and/or replications are required when orthogonal comparisons can be defined.
Growth and Nutrient Uptake of Soybean Roots Under Field Conditions1
Authors: Barber Stanley A.
Published: July 2010

Although soybean (Glycine max L. Merr.) root growth in soil has been measured, the nutrient flux characteristics of the roots during the growth of the plant in the field have not. Soybean root amount and distribution were measured using approximately biweekly samplings during the growth of ‘Williams’ soybeans on Chalmers silty clay loam soil (Typic Argiaquoll) near Lafayette, Ind., in 1973, 1974, and 1975. Root length and fresh weight were measured with depth and distance from the row. Shoot samples taken at each sampling were analyzed for P and K. Shoot growth rate averaged 135 kg ha−1 day−1 between plant ages of 50 and 100 days. Shoot concentration of P decreased until 60 days then increased as beans began to form. Shoot concentration of K decreased during the sampling period. Root length increased until 70 to 80 days, remained constant to 100 days, and then decreased. Maximum root length averaged 24 cm per cm2 of soil surface. Average proportion of the roots in the 0 to 15 cm layer increased with plant age after 36 to 49 days and reached a maximum of 59% at 113 to 120 days. Soybean root density was approximately one‐fifth that observed at the same location for corn (Zea mays L.). Influx of P and K into soybean roots was less than with corn during early growth but more than corn later in the season. This result indicates that soybeans may not respond to fertilizer banded near the seed at planting but would require higher P and K fertility in the whole rooting volume of soil than corn after 50 days in order to sustain the required nutrient influx into the roots.
Yields, Nutrient Removal, and Nutrient Concentrations of Double‐Cropped Corn and Small Grain Silage1
Authors: Murdock L. W. , Wells K. L.
Published: July 2010

Double‐cropping corn (Zea mays L.) and small grain silage has become an important practice but there is virtually no research information upon which to base fertility or management decisions. Consequently a double‐cropping corn and small grain silage experiment was conducted at two locations in Kentucky. The study was initiated to determine production levels from doublecropped silage, the most compatible small grain species for double‐cropped silage, and the rate and method of fertilizer application needed for high production. Field experiments were established on Huntington (fine‐silty, mixed mesic fluventic Hapludoll) and Pope (coarse‐loamy, mixed, mesic fluventic Dystrochrept) soils. Three fertility levels were tested with 392‐128‐280, 280‐89‐232, or 168‐54‐140 kg/ha of N‐P‐K being applied each year. Single and split applications of K were studied. Barley (Hordeum vulgare L.) and oats (Avena sativa L.) were compared as small grain species. Double‐cropped silage produced 26% more dry matter than single cropped silage. Since most of the total silage yield was due to corn, the harvesting management favored this crop so that its yield potential would not be reduced. As a result all small grain species were harvested on the same date and large differences in stage of maturity existed. The small grain species or its stage of maturity at harvest were found to affect the yield of the succeeding corn crop. Corn grown after barley, harvested in soft dough, averaged 25% more yield than that grown after oats, harvested at heading. Fertility rates above 280‐89‐232 kg/ha of N‐P‐K (250‐180‐250 lb/A of N‐P205‐K2O) did not significantly increase the yield. The average nutrient removal at the foregoing rate of fertility was 241‐54‐260 kg/ha of N‐P‐K. The small grain accounted for 47% of the total K removed. Split applications of K increased the corn silage yield at the low application rate (140 kg/ha/yr). At one of the two locations the corn yields were 33% higher when one‐half of the total annual K was added to each crop as opposed to adding all of the K at the time of small grain planting. This study indicates that double‐cropped corn and small grain for silage can result in substantially higher dry matter production per unit land area than single‐cropped corn. Large amounts of minerals are removed, however, particularly K, by the small grain component of the double‐cropping system.