bluuebunny/crossref_metadata_2025 huggingface dataset:
Accumulation and Distribution of K, Ca, and Mg by Selected Determinate Soybean Cultivars Grown With and Without Irrigation1
Authors: Karlen D. L. , Hunt P. G. , Matheny T. A.
Published: July 2010

Reports on nutrient accumulation and distribution by determinate soybeans [Glycine max. (L.) Merr.] when grown under field conditions have seldom compared irrigated and nonirrigated management or attempted to measure differences among cultivars. To provide this information we grew three or four determinate soybean cultivars from Maturity Group VI, VII, or VIII with or without irrigation on a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Paleudults) during 1978 and 1979. Plant samples were collected periodically throughout the growing season to measure dry matter accumulation and distribution among the leaves, petioles, stems, and pods. Plant fractions were analyzed for K, Ca, and Mg to measure nutrient accumulation and distribution. The two growing seasons during which the soybeans were grown had distinctly different rainfall patterns. In 1978 a drought existed for most of the reproductive growth period, while in 1979 a drought occurred during the vegetative growth stages. Also, in 1979 the soil water content below 30 cm was generally higher throughout the entire growing season. Potassium, Ca, and Mg concentrations and accumulations were all greater during 1979, but even with irrigation, yields averaged only 1.95 metric tons/ha compared to irrigated yields of 3.16 metric tons/ha in 1978. Nonirrigated yields averaged 1.72 and 1.62 metric tons/ha in 1978 and 1979. The lower yields in 1979 may have been caused by very wet soils following Hurricane David which may have reduced O2 levels during pod fill. The uptake patterns of K, Ca, and Mg showed different responses to water stress, probably because of differences in the mechanism by which these nutrients move to plant roots. Potassium uptake under nonirrigated (stressed) conditions fluctuated with water availability, whereas K uptake under nonstressed (irrigated) conditions was relatively constant until physiological maturity. Calcium and Mg uptake were relatively constant regardless of stress until physiological maturity. Differences in nutrient concentrations and accumulations among cultivars were generally not statistically significant, although the Ransom cultivar frequently had the highest nutrient concentrations and also produced the highest seed yield. Irrigation did not significantly change the cation concentrations within the soybean plant. Therefore, differences in cation accumulation were primarily caused by increased plant growth.
Dry Matter Accumulation Patterns and Seed Yield Components of Two Indeterminate Soybean Cultivars1
Authors: Beaver J. S. , Cooper R. L.
Published: July 2010

The Maturity Group II soybean [Glycine mar (L.) Merr.] cv. Corsoy often produces seed yields in central Illinois that are equal or greater than many full‐season, Maturity Group III cultivars. A field study was conducted during two growing seasons at Urbana, Ill. in order to gain a better understanding of the yield physiology of Corsoy. Dry matter accumulation patterns of various plant parts, leaf areas, seed yields, and seed yield components of Corsoy were compared with those of Maturity Group III cv. Williams.

Corsoy accumulated seed dry weight more efficiently than Williams by producing seed yields as great as or greater than Williams with less leaf area and less total vegetative dry weight than Williams. Although Corsoy produced less leaf area than Williams, crop growth rates of Corsoy and Williams were similar. This suggested that Corsoy possessed a greater net assimilation rate than Williams. Although Corsoy reached harvest maturity (RS) 2 weeks earlier in the growing season than Williams, duration of the seed filling periods of Williams and Corsoy were similar. Differences in seed yield were attributed to differences in rates of seed dry weight accumulation per unit‐area. Corsoy accumulated reproductive (seed and pod wall) dry weight at a greater rate than Williams by setting a greater number of pods containing at least one seed. Corsoy initiated reproductive development earlier in the growing season than Williams which resulted in Corsoy accumulating less vegetative dry weight and leaf area than Williams. The results suggested that earlier reproductive development might enable the pod filling period to be lengthened without affecting the harvest maturity date.
Corn Yield as Influenced by In‐season Application of Nitrogen with Limited Irrigation1
Authors: Anderson C. K. , Stone L. R. , Murphy L. S.
Published: July 2010

With limited irrigation of corn (Zea mays L.) on medium or fine textured soils, the initial application of water (and thus of N being water applied) would perhaps be no earlier than when corn is at the 12 or 14‐leaf growth stage. This experiment was established to evaluate the effects of delaying N application until the 14‐leaf or silk emergence growth stages on yield of corn on a medium‐textured soil.

The study soil is a coarse‐silty, mixed, mesic, Fluventic Hapludoll near Manhattan, Kansas. Ten treatments (combinations of N application time and rate, each replicated three times in a completely randomized design) were applied in each of 3 years. Nitrogen was broadcast applied (preplant) and applied with irrigation water (at the 14‐leaf stage and/or at early silking).

Grain N content increased as N fertilizer rates increased and as N application time was delayed. No corn grain or dry matter yield advantage was found for split applications or for in‐season applications of N over preplant application. Corn receiving 101 kg N/ha at the 14‐leaf stage produced 94% of the grain obtained when 101 kg N/ha was applied preplant. Corn receiving 101 kg N/ha at silk emergence produced 71% of the grain obtained when the same N rate was applied preplant. Our findings indicate that with limited irrigation of corn on medium to fine‐textured soils, all N should be applied preplant rather than in‐season with irrigation.
Proposal: Critical Nutrient Ranges for Crop Diagnosis1
Authors: Dow A. I. , Roberts S.
Published: July 2010

The concept of critical nutrient concentration (CNC) as a basis for diagnosing nutritional problems is well established. The CNC implies a single point on a curve that relates nutrient concentration with yield. However, a single point is difficult to establish experimentally and, in addition, the critical point may vary under different conditions. Therefore, it seems desirable to deal with a critical nutrient range (CRN) of concentration rather than with a single concentration. Critical nutrient range is defined as: that range of nutrient concentration above which we are reasonably confident the crop is amply supplied and below which we are reasonably confident the crop is deficient. If “seasonal monitoring” of crop nutrition is to be useful, CNR values must previously be established at various growth stages during the season. Data are cited to illustrate the need for the CNR approach and for seasonal monitoring of CNR values.
Root Development of Field‐Grown Flue‐Cured Tobacco1
Authors: Osmond Deanna L. , Raper C. David
Published: July 2010

A flue‐cured cultivar of tobacco (Nicotiana tabacum L. ‘NC 2326’) was grown on a Norfolk fine sandy loam soil (Typic Paleudult) in 1977 and 1978 to characterize the development of roots in field culture and additionally in 1978 to determine the extent to which band placement of fertilizer and removal of the flowering head by topping at anthesis influence the pattern of development. Both band placement of fertilizer and topping are common cultural practices. Root development was observed at intervals during the growing season using a pinboard method. Pinboard monoliths, 100‐cm wide, 60‐cm deep, and 24‐cm thick, were taken transverse to the row and the soil rinsed away with a fine spray of water to expose the roots. Because of rotational schedules, the same field could not be used in both years, but adjacent fields within a continuous soil mapping unit were used. The single distinction in soil properties between fields was the thickness of the A2, horizon. In 1977 the A2 horizon was 25 to 35‐cm thick, and in 1977 the A2 was 0 to 5‐cm thick.

In both years root growth until anthesis was confined to the Ap horizon and then penetrated into subsurface horizons. In 1977 root growth after anthesis was contained within the A2 and did not penetrate into the B2. In 1978 roots penetrated through the thin A2 horizon and into the B2. The eventual depth of rooting in 1978 was greater than in 1977; however, the mass of roots recovered in 1977 was nearly three times greater than in 1978. Soil moisture data for both years and measurement of penetrometer resistances in 1978, along with published data, indicate that the variations in rooting depth and dry weight may have been associated with the effects of differences in soil moisture on resistance to penetration at the A to B interface and on shifts in direction of assimilate flow within the plant in response to changes in turgor potentials within the plant.

For the cultural variables imposed in 1978, the pattern of root development was not different between removal of the floral parts at anthesis, together with chemical inhibition of lateral meristem development, and permitting uninterrupted floral development. Fertilizer placement did alter the rate of root development for a period following anthesis, but not the final root mass, with a greater rate during this interval for banded than for broadcast placement.
Height and Yield Response of Selected Wheat, Barley, and Triticale Cultivars to Ethephon1
Authors: Dahnous K. , Vigue G. T. , Law A. G. , Konzak C. F. , Miller D. G.
Published: July 2010

Yield losses occur in cereals as a result of lodging. Ethephon [(2‐chloroethyl)phosphonic acid] has been reported to reduce lodging; however, studies of its effect on grain yield have produced conflicting results. In this study. selected cultivars of semidwarf wheat (Triticum aestivum L.), normal height barley (Hordeum vulgare L.) and triticale (Triticale hexaploid L.) were treated with ethephon to determine (1) if this growth regulator had an effect on yield other than via a reduction in lodging and (2) the optimum growth stage and rate (kg/ha) of application. Foliar‐applications to field grown plants (the soil was a fine‐silty, mixed, mesic Cumulic Haplaxeroll) were made at two plant growth stages, late boot and early heading. Ethephon was applied at 0, 0.28, and 0.55 kg&ha in 1976 and at 0, 0.28, 0.55, and 0.85 kg/ha in 1977. Main plots were fertilized with 45 or 90 kg N/ha in 1976 and 90 or 180 kg N/ha in 1977.

Ethephon applications at the late boot stage reduced the elongation of plants more effectively than applications at early heading. Ethephon treatments reduced elongation of tall cereal species, i.e., barley and triticale were significantly shorter following treatment of 0.28 kg/ha in 1977. Ethephon treatments increased harvestable yields when they reduced lodging. For instance, untreated ‘Unitan’ barley lodged heavily, but ethephon treatment of 0.55 kg/ha reduced lodging which resulted in increased harvestable yields. Ethephon treatment of 0.84 kg/ha significantly inhibited stem elongation in semidwarf wheats, but semidwarf wheats did not lodge and treatment did not increase yields. The results of this study indicate that further field testing should be conducted in regard to ethephon's potential to benefit yields of tall, ‘weak‐stemmed’ cereals such as barley, since no benefit was derived from ethephon treatment to semidwarf wheats.
Seedling Growth and Nodulation of Arrowleaf, Crimson, and Subterranean Clovers1
Authors: Evers G. W.
Published: July 2010

Cool‐season annual clovers (Trifolium spp.) are overseeded in warm‐season perennial grasses to extend the grazing season and to incorporate symbiotically fixed N in the pasture system. Overseeding grass sods with clover often fails because of grass competition and unfavorable climatic conditions during the establishment period. Seed size and its effect on seedling vigor was determined on three cultivars of arrowleaf (Trifolium vesiculosum Savi.) clover, crimson (Trifolium incarnatum L.) clover, and subterranean (Trifolium subterraneum L.) clover. Each fall for 3 years clover seedlings were excavated 3 and 7 weeks after planting in 1976 and 1977, and 5 and 13 weeks in 1978. Nodules, leaves, and weight per seedling, percent protein, and total dry matter production were determined.

The species seed weight ratio for arrowleaf:crimson:subterranean was 1:2.9:6.8 with minor differences between cultivars within species. Subterranean clover means were always highest for nodules, leaves, and weight per seedling except for the 13‐week sampling in 1978. Arrowleaf clover means were always lowest with crimson being intermediate. The most dramatic species difference was for seedling weight with subterranean seedlings three to four times and crimson seedlings two to three times heavier than arrowleaf seedlings. Seedling weight differences between species decreased with time and did not affect total forage production for the season. There was a high correlation of seed weight with nodule and leaf number and at the earlier samplings for seedling weight. Percent protein and yield were not significantly correlated with seed weight. Ranking of the three clover species for nodules, leaves, and weight per seedling in this study was identical to that for seed weight. Thus, subterranean clovers should be the least difficult to establish and most competitive, followed by crimson and then arrowleaf clover.
Effects of N, P, and K Fertilization on Barley Grown in a Newly Cleared Subarctic Soil1
Authors: Michaelson G. J. , Loynachan T. E. , Wooding F. J. , Mitchell G. A.
Published: July 2010

Alaska has vast areas of undeveloped land with the potential for agricultural expansion. To develop renewable resources from oil royalty monies, the state has initiated a 24,000 ha agricultural demonstration project near Delta Junction, Alaska. Little is currently known, however, concerning the natural fertility of these virgin soils. A 43 factorial experiment was established, with barley (Hordeum vulgare L. var. ‘Otra’) as the test crop, to determine responses to fertilization the first 2 years after clearing on a Typic Cryopsamment soil. Fertilizer was applied before seeding each year at 0, 45, 90, and 135 kg N/ha; 0, 34, 68, and 102 kg P/ha; and 0, 34, 68, and 102 kg K/ha. Grain yields, protein contents, and subsequent soil‐test levels were measured.

Nitrogen increased grain yields from 2 quintal/ha with no applied N in 1979 to 25 quintal/ha with 135 kg N/ha and from 4 quintal/ha with no applied N in 1980 to 31 quintal/ha with 135 kg N/ha. The yield response to N was linear throughout the 0 to 135 kg N/ha range in 1979, and both the linear and quadratic regression terms were significant in 1980. Cooler initial soil temperatures, lack of native residual nutrients, or N immobilization may have contributed to lower overall yields in 1979. Grain protein increased linearly with added N both years. Phosphorus increased yield up to 34 kg P/ha, with little response beyond that in either year. In 1979, both P and K were significant in increasing the yield response to N. In 1980, only K increased the yield response to N. Neither P nor K fertilization significantly increased grain protein contents.

Multiple‐regression equations were developed to predict grain yields and protein contents with rates of fertilizer applied. When considering only N, P, and K fertilizer additions, equations with relatively high coefficients of determination were obtained for the first 2 years of production (Yield: R2 = 0.929,0.937 for 1979 and 1980; and protein: R2 = 0.684, 0.842 for 1979 and 1980, respectively). Thus, the application of fertilizer accounted for much of the variation in yield and protein contents.
Phosphate Rock and Superphosphate Combinations for Soybeans in a Cerrado Oxisol1
Authors: Smyth T. J. , Sanchez P. A.
Published: July 2010

The extent to which local low reactivity Patos de Minas phosphate rock (PR) and banded superphosphate (OSP) applications can replace high cost broadcast OSP applications was studied during a 2‐year period on a Typic Acrustox at the Cerrado Research Center near Brasilia, Brazil. Highest soybean (Glycine max) yields were obtained in two consecutive crops with a single broadcast OSP application of 352 kg P/ha or by broadcasting 172 kg P/ha + banding 44 kg P/ha per crop, all as OSP. Combining a broadcast PR application of 88 kg P/ha + 44 kg P/ha as banded OSP per crop resulted in 81% of the maximum yield at 31% of the cost of applying 352 kg P/ha as OSP. Increasing the broadcast PR rate to 352 kg P/ha while maintaining the same banded OSP rate produced 89% of the maximum yield at 50% of the fertilizer cost. Other OSP combinations (44 broadcast + 44 annual band; 88 broadcast + 22 annual band; 88 broadcast + 44 annual band; and 178 broadcast without annual bands) also produced over 80% of maximum yield at 38 to 50% of the fertilizer cost.

Broadcast P applications were found necessary to obtain the highest soybean yields observed in this experiment. Phosphate rock alone was unable to supply sufficient P; it must be supplemented by annual banded OSP applications. About 4 kg P/ha as PR were required to obtain similar increases in available P as 1 kg P/ha as OSP. Phosphorus availability in the broadcast OSP treatment decreased with time, while that of broadcast PR remained stable. Response to bandapplied OSP, in combination with either broadcast source, declined with increasing levels of Bray 1 available P. This soil test helps estimate further needs of banded OSP applications. The Bray 1, Olsen, and resin extractants produced the same critical ranges with either source, suggesting that the two rapid extractants could be used in Oxisol areas where PR use is being introduced. Critical ranges of available P for soybeans in this soil were 11 to 15 ppm Bray 1 P, 6 to 8 ppm Olsen P, and 8 to 12 ppm resin‐extractable P.
Leaf Photosynthetic Response to Foliar Fertilizer Applied to Corn Plants During Grain Fill1
Authors: Harder H. J. , Carlson R. E. , Shaw R. H.
Published: July 2010

Foliar fertilization of field crops has received renewed interest as a method of increasing seed yield by supplying additional nutrients to the leaves to delay the normal depletion of nutrients in the leaves during reproductive stages. It has been hypothesized that application of foliar fertilization may delay natural leaf senescence. We tested this by estimating leaf photosynthesis in field‐grown corn (Zea mays L.) plants using a 14CO2 uptake procedure. A small segment of the leaf material enclosed in a chamber is exposed to 14CO2 for a short time period. Leaf samples are then analyzed using standard radiotracer techniques. In 1976 and 1977 14CO2 uptake rates were measured on a number of days between silking and plant maturity in conjunction with a larger experiment relating the response of corn to foliar fertilizer application and soil moisture deficits. The experimental plants were field‐grown in a Nicollet loam soil (an Aquic Hapludoll, fineloamy, mixed, mesic).

These measurements indicated that the rate of leaf photosynthesis was depressed by as much as 17% the day following foliar‐fertilizer application, but had nearly recovered by the 2nd day. A similar pattern occurred in leaf conductance. No difference in the seasonal trend of photosynthetic rate was detected between control and foliarfertilizer treatments.

Photosynthetic patterns after foliar‐fertilizer application may warrant further investigation, as significant yield reductions were noted in these experiments. Because the technique used in our experiments monitors rate of photosynthesis on small, intact leaf segments, totalcanopy photosynthesis and transpiration measurements could reveal helpful information.
Salt Tolerance of Two Pea Cultivars1
Authors: Cerdá A. , Caro M. , Fernández F. G.
Published: July 2010

Production of pea (Pisum sativum) in southeastern Spain may be limited because the waters used for irrigation are relatively poor in quality. Accordingly, this study was done to determine the salt tolerance of the pea and to compare the effects of water quality on production of pods, seed, and leaf mineral composition. Two pea cultivars were grown to maturity in lysimeters filled with a calcareous soil (Paralithic‐mollic‐Calciorthid) and irrigated with waters having ECi, values of 1.8, 4.0, 6.0, and 10.0 dS/m.

The mean ECe values for the 0 to 25 cm horizon of the lysimeter soils at harvest time were approximately the same as the EC,iw of the water applied. The yields of green pods plotted as a function of ECe. manifested a yield‐ECe, function described by the equation y = 100 − B (ECe — A) where y represents the yield expressed relative to that for the lowest ECiw treatment, and B and A, the slope, and threshold ECe. value. The threshold ECe values for the SP‐290 and ‘Durana’ cultivars were respectively 2.5 and 4.5 dS/m; both cultivars exhibited the same slope value per unit decrease of ECe. at values < the threshold ECe value. Thus, the SP‐290 and Durana cultivars respectively were classified as moderately salt sensitive and moderately salt tolerant. Leaf analysis data showed a salinity treatment effect for Cl and NO3−N only, whereas cultivar effects were reflected in the Na, Ca, K, P, and total N data.

The yield reduction appeared to be a function of the osmotic potential of the soil water within the rootzone (ECe although specific effects also may account in some degree.
Nitrogen and Date of Defoliation Effects on Seed Yield and Seed Quality of Tall Fescue1
Authors: Watson C. E. , Watson V. H.
Published: July 2010

Each year approximately 150,000 to 200,000 ha of tall fescue (Festuca arundinacea Schreb.) are havested for seed in the United States. The majority of this hectarage is utilized for fall and winter grazing as well as seed production in the spring. The objectives of this study were to examine the effects of N level and date of last forage harvest in the spring on the forage and seed yield and seed quality of tall fescue.

A sward of ‘Kenwell’ tall fescue was grown under three levels of N and five defoliation regimes at Mississippi State, Miss. on a Leeper silty clay loam (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept). Nitrogen rates of 0, 67, and 134 kg/ha applied as NH4NO3 were applied in February of 1967 and 1968. Plots were harvested zero, one, two, three, or four times at 15 day intervals prior to seed harvest. The five defoliation treatments, by date of last forage harvest prior to seed harvest were no harvest, 15 and 30 March and 15 and 30 April. Following seed harvest the aftermath was harvested for forage. Variables measured were dry matter yield, seed yield, panicles/ m2, spikelets/panicle, and florets/spikelet. Seed quality characteristics measured included germination, seedling weight, and shoot and radicle length.

Dry matter and seed yields were decreased significantly in plots defoliated later than 30 March. Reductions in seed yield appeared to be the result of decreased tiller density and the number of spikelets per panicle. Early spring defoliation (15 March) resulted in some damage to fertile tillers in the 1st year as evidenced by a reduced number of spikelets/panicle, although there was no effect on seed yield or tiller density. Seed quality was reduced for all plots defoliated after 30 March.

Dry matter and seed yields increased with increasing rates of N. Maximum forage and seed yields were attained at 134 kg/ha of N while maximum seed quality was attained with 67 kg/ha of N.

Results of this study indicate that tall fescue seed fields which are to be grazed or cut for hay should not be defoliated in the spring after tillers commence to elongate and become erect if maximum production is to be realized. Higher rates of N were required to maximize dry matter and seed yields than to maximize seed quality.
Concentrations of Mg, Ca, P, K, and Crude Protein in Fertilized Tall Fescue1
Authors: Reynolds J. H. , Wall W. H.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) pastures have been implicated with the occurrence of grass tetany in the eastern U.S.A. Grass tetany problems would probably be reduced if Mg concentration in tall fescue forage were increased. The purpose of this study was to examine the effects of Mg, NPK, and N fertilizers on Mg and other major nutrients in tall fescue grown on a soil already high in Mg. A randomized complete block factorial experiment was conducted for 2 years on an Etowah silt loam (line‐loamy, siliceous, thermic, Typic Paleudults).

Tall fescue was fertilized in August of 2 successive years with 0, 84, or 168 kg Mg/ha from MgSO4 . 7H2O and 67‐29‐56 or 134‐58‐112 kg N, P, K/ha from a complete NPK fertilizer; and in December with 0 or 67 kg N/ha from NH4NO3. Forage was harvested five times during the growing season and stockpiled forage was harvested in December. The Mg concentration in forage was increased by Mg and N application and was not affected by NPK rate. Calcium was decreased by N. Potassium was slightly increased by NPK fertilization.

Forage Mg was above 0.20% for all sampling dates and K/(Ca + Mg) ratios were below 2.2, so the grass tetany hazard from this forage was probably low. Soil test Mg levels increased in response to Mg fertilization, but soil Mg levels were not affected by NPK or N fertilization. Temperature of the growth period had a greater influence on forage Mg than the fertilization treatments on this soil which was already high in Mg.
Irrigation, Row Spacing, and Genotype Effects on Late and Ultra‐Late Planted Soybeans1
Authors: Boerma H. R. , Ashley D. A.
Published: July 2010

In the southeastern United States between 25 and 40% of the soybean [Glycine max (L.) Merr.] hectarage is double‐cropped. Information on desirable production practices for double cropping soybeans after small grains, soybeans, or corn (Zea mays L.) is limited. The objectives of this study were to evaluate the effects of late (late June or early July) and ultra‐late (late July or early August) planting dates, 51‐ and 91‐cm row widths, irrigated and nonirrigated treatments, and Maturity Group VII determinate (‘Bragg’) and indeterminate (Ga76‐32 and Ga76‐18) genotypes on seed yield and other plant traits.

The experiment was conducted at Plains, Ga. (32°N Lat 84°W Long) on a Greenville sandy loam (Rhodic Paleudult, clayey, kaolinitic, thermic family) soil in one dry (1978) and two intermediate rainfall seasons (1979 and 1980). Delays in planting from early July to late July resulted in an average yield reduction of 36 kg ha−1 day−1 (1.5%). In the dry season supplemental irrigation increased yield 355% (2,623 kg ha−1) in the late planting and 115% (635 kg ha−1) in the ultra‐late planting. In the intermediate rainfall seasons irrigation increased yields 38% (784 kg ha−1) for the late and 15% (190 kg ha−1) for the ultra‐late planting. The 51‐cm rows averaged 17% (278 kg ha−1) higher seed yield than the 91‐cm rows when averaged over years and all other factors. Genotypes did not differ in seed yield. The magnitude of the yield reduction from delays in planting and the high response to irrigation in dry seasons indicate the importance of intensive management to obtain maximum yields in these late‐planted environments.
Sod‐Seeding Perennial Grasses into Eastern Nebraska Pastures1
Authors: Samson John F. , Moser Lowell E.
Published: July 2010

Eastern Nebraska and neighboring areas have large amounts of depleted pastures which consist of annual bromegrasses (Bromus spp.), Kentucky bluegrass (Poa pratensis L.), and numerous broadleaf weeds. Such pastures need renovation but complete seedbed preparation is expensive and may enhance erosion. The objective of our study was to determine if sod‐seeding grasses offered an alternative to complete seedbed preparation. Three weedy pastures in southeast Nebraska on a Hastings silty clay loam (fine, montmorillonitic, mesic Udic Argiustoll), a Lamo silty clay loam [fine‐silty, mixed (calcareous), mesic Cumulic Haplaquoll], and a Geary silty clay loam (fine‐silty, mixed, mesic Udic Argiustoll) were sprayed with sod suppressing herbicides and sod‐seeded with intermediate wheatgrass [Agropyron intermedium (Host) Beauv.] or switchgrass (Panicum virgatum L.). Spring herbicide treatments consisted of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] plus paraquat ( 1 , 1 ‘ dimethyl‐4, 4’ bypyridinium ion) broadcast and banded at 0.3 + 2.2 kg/ha, respectively, glyphosate [N‐(phosphonomethyl) glycine] broadcast and banded at 1.1 and 2.2 kg/ha, and paraquat broadcast at 0.3 or 0.6 kg/ha. In the spring experiments both intermediate wheatgrass and switchgrass were seeded. In late summer experiments the atrazine plus paraquat treatments were replaced with banded paraquat and only intermediate wheatgrass was seeded. A nonsprayed but seeded control and a seeded rototilled treatment were included at all locations and dates.

Intermediate wheatgrass stands were acceptable if aboveground herbage suppression was 65% or greater during the first 6 weeks after spraying a subirrigated pasture and 80% or greater during the first 6 weeks after spraying upland pastures in the spring. In order to successfully establish switchgrass complete sod‐suppression during the first 6 weeks after spraying was required on the subirrigated pasture and 85% suppression was required on the upland pastures. Glyphosate and paraquat suppressed the sod more severely in late summer but subsequent competition with annual brome increased. Atrazine plus paraquat, or glyphosate broadcast in spring, greatly enhanced the vigor of remnant big bluestem (Andropogon gerardii Vitman) in these depleted but unplowed pastures. In some instances the existing big bluestem was dense enough to form a complete stand once the cool‐season vegetation was removed. In other situations the seeded switchgrass established around the resident big bluestem clumps.
Manganese Deficiency and Toxicity in Wheat: Influence on Growth and Forage Quality of Herbage1
Authors: Fales S. L. , Ohki K.
Published: July 2010

There is little information concerning critical Mn deficiency and toxicity levels in forage plants, or how plant Mn concentration affects other plant constituents associated with forage quality. This study was undertaken to investigate possible interactions between plant Mn concentration and the growth and forage quality of wheat (Triticum aestivum L. cv. Stacy).

Wheat plants were grown in nutrient solution containing 0.005, 0.02, 0.05, 0.25, 1, 5, 25, 100, 200, and 500 µg/g Mn. Plants were grown for 30 days after transplanting into nutrient solution and were harvested at the three‐leaf stage, lyophilized, and weighed. Manganese concentration, in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), in vitro cell wall disappearance (IVCWD), total nonstructural carbohydrates (TNC), and Ca and Mg concentrations were determined on wheat shoot.

Critical Mn deficiency and toxicity levels affecting normal growth of wheat shoot were determined to be 35 and 475 µg/g dry wt, respectively. These values are useful in determining deficiency and toxicity in wheat production. Percentage NDF, IVDMD, TNC, and IVCWD were reduced in tissue from plants that were critically Mn‐deficient. In vitro dry matter disappearance and TNC were increased in tissue from critically Mn‐toxic plants.

In vitro dry matter disappearance ranged from 71 to 89%, with the lowest values observed for Mn‐deficient and the highest for Mn‐toxic plants. The high IVDMD of the Mn‐toxic plants appeared to be related to an accumulation of TNC, while the relatively lower IVDMD of the Mn‐deficient plants was related to reduced cell wall digestibility. Both Ca and Mg concentrations decreased as Mn concentration in the plants increased above 475 µg/g.

Results of this study indicate that Mn deficiency and toxicity in wheat have a significant effect on amount of growth and the concentration of plant constituents associated with forage quality. These constituents remain relatively constant over the adequate range of Mn nutrition and plant Mn concentration should be kept within the 35 and 475 µg/g range.
Tolerances of 20 Rice Cultivars to Excess Al and Mn1
Authors: Nelson Lyle E.
Published: July 2010

Manganese toxicity is a rare occurrence in flooded or paddy rice (Oryza saliva L.); however, this is not the case for upland rice grown on aerobic soils. Although acid upland soils may contain toxic levels of both Al and Mn, cultivar tolerances to excess Al and Mn do not necessarily coincide. These studies were to determine whether a procedure could be devised for rapid screening of rice cultivars for tolerances to excess Mn and to correlate tolerances between excess Al and excess Mn. Nine rice cultivars were grown in a greenhouse for 4 weeks in nutrient solutions containing 1 µg·cm−3 and 80 µg·cm−3 Mn. The relative tolerance was expressed as a ratio of the excess Mn treatment to the optimum or control treatment using weights of plant parts, height, root length, and tiller number. These expressions of relative tolerance to excess Mn were used to rank the nine cultivars. These rankings were then compared to a ranking based on previous results obtained at IRRI when the cultivars were grown on an acid soil. Significant Spearman's rank correlation coefficients were observed between rankings for tolerance to acid soil toxicity and relative root weight (r8 = −0.93**, significant at the 0.01 level) and relative tiller number (r8 = −0.68*, significant at the 0.05 level). Other rank correlations with acid soil toxicity were not significant. Subsequently, 20 cultivars were screened for tolerance to excess Mn by growing them in a greenhouse for 4 weeks in solutions containing 0.5 and 80 µg·cm−3 Mn. These cultivars were also screened for tolerance to excess Al by growing them for 3 weeks at 3 and 30 µg·cm−3 Al. The correlation between tolerances to excess Al and Mn was tested using relative root length for Al and relative shoot weight for Mn. The correlations were not significant. Large differences in tolerance to excess Mn were observed among rice cultivars; however, it was not established that screening trials using soils containing excess amounts of available Mn can be replaced by short‐term screening in nutrient solutions. The results of this study clearly indicate that tolerance to excess Al is not necessarily correlated with tolerance to excess Mn.
Legume Establishment in Grass Sods Using Minimum‐Tillage Seeding Techniques without Herbicide Application: Forage Yield and Quality1
Authors: Taylor R. W. , Allinson D. W.
Published: July 2010

Seedings of forages can now be made directly into existing vegetation following herbicide application. Herbicides, however, are expensive and may destroy desirable vegetation. Three field experiments were conducted on a Paxton fine sandy loam soil (coarse‐loamy, mixed, mesic Typic Dystrochrepts) to evaluate minimum‐tillage establishment of legumes in grass sods without herbicide application and to evaluate subsequent changes in forage quality. In Exp. I, alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and crownvetch (Coronilla varia L.) were seeded into orchardgrass (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.), smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.) sods. Harvests were taken in 1975 through 1978 and samples obtained in 1977 and 1978 were analyzed for in vitro dry matter disappearance (IVDMD), crude protein, and mineral content. Alfalfa and birdsfoot trefoil establishment was most successful in timothy and smooth bromegrass and least successful in orchardgrass. Crownvetch failed to establish. Alfalfa mixtures produced the most dry matter, digestible dry matter, and crude protein in 1977 and 1978. Winter survival was greatest for legumes seeded in tall fescue. Experiments II and III were conducted on sites where soil pH was 6.4 and 5.6, respectively. Birdsfoot trefoil, red clover (Trifolium pratense L.), and crownvetch were directly seeded into a mixed grass‐forb sod. Vegetation was mowed for 8 weeks after seeding at either 2‐ or 4‐week intervals. Crownvetch failed to establish. Mowing frequency after seeding had little effect on legume establishment. Red clover seedings increased yields of crude protein in 1977 and digestible dry matter in 1977 and 1978. Birdsfoot trefoil did not increase digestible dry matter yields, compared to the control, until 1979 on the limed soil but increased digestible dry matter yields in 1978 on the initially unlimed soil. Results indicate that alfalfa, birdsfoot trefoil, and red clover may be successfully direct seeded into certain grass sods that have not been suppressed using herbicides.
Sugar Beet N Fertilization and Economic Optima: Recoverable Sucrose vs. Root Yield1
Authors: Adams R. M. , Farris P. J. , Halvorson A. D.
Published: July 2010

Sugar beet (Beta vulgaris L.) yields are frequently measured in terms of root yield but recoverable sucrose is the marketable product. The response of recoverable sucrose content to N fertilization differs from that of whole root yield. The rationale for this study was to compare N fertilization rates and associated returns under two decision rules: (1) fertilize to optimize recoverable sucrose yield and (2) fertilize to optimize whole root yield. Sets of response functions were estimated using both whole root yield and recoverable sucrose as measures of yield. Three years of data (1976‐1977‐1978) from the Northern Plains Soil and Water Research Center, Sidney, Mont., were used to derive these physical relationships. The estimated response functions were then combined with price and cost data to determine economically optimal N fertilization rates. Finally, returns for each optimal combination were calculated and compared. The results show substantially lower levels of N are required to optimize recoverable sucrose. Over the years of this analysis, it required approximately 90 kg less N per ha to optimize recoverable sucrose than whole root yield. More importantly, under the conditions of this analysis, producer returns would increase by an average of $460 per ha by using N rates consistent with recoverable sucrose rather than root yield. These observations suggest substantial economic benefits from use of recoverable sucrose in N fertilization decisions.
Turfgrass Growth, N Use, and Water Use under Soil Compaction and N Fertilization1
Authors: Sills M. J. , Carrow R. N.
Published: July 2010

Soil compaction is a problem in many turf areas. In this greenhouse study the effects of soil compaction on turfgrass growth, N use, and water use were investigated. Perennial ryegrass (Lolium perenne L. ‘Pennfine’) was subjected to two compaction treatments with an 11.5 kg falling weight: a) none and b) heavy–874 J energy. Two parts of fine, montmorillonitic mesic, Aquic Argiudoll soil (Chase silt loam) was used to one part medium silica sand by volume. Fertilization rate treatments were 0.5 and 1.0 kg N/100m2. Nitrogen carrier treatments were water soluble N applied as NH4NO3 and water insoluble N applied as IBDU (isobutylidine diurea). Compaction increased bulk density, water retention, and soil strength, while decreasing aeration porosity. Visual quality, clipping yield, N use per unit area of sod, evapotranspiration, and root growth declined with compaction. Verdure, total nonstructural carbohydrates (TNC), and percent N in leaf tissue were not affected by compaction. Initial TNC levels, water use efficiency, and N use per unit area, increased as N rate increased. Clipping yield, N use per unit area, and water use efficiency were higher with a water‐soluble N carrier. Percent N in leaf tissue, early in the study, increased with water‐insoluble fertilizer. The most detrimental effects of compaction were on root weight and distribution at the high N rate. Application of high N did not compensate for the adverse effects of compaction.
Response of the Clover‐Rhizobium Symbiosis to Soil Acidity and Rhizobium Strain1
Authors: Thornton Frank C. , Davey C. B.
Published: July 2010

Thirty‐three strains of Rhizobium trifolii were tested for the effects of soil acidity on nodulation, nitrogen fixation, and dry matter production with ‘Mt. Barker’ clover (Trifolium subterraneum L.). Clover plants were grown in a Norfolk loamy sand (Typic Paleudult, fine loamy, silicious thermic) adjusted to 7, 34, and 57% Al saturation at acidity levels of pH 5.9, 5.1, and 4.4, respectively. Results from this experiment confirm that R. trifolii exhibits a large and varied tolerance to soil acidity in symbiotic association with the host. Laboratory prescreening of R. trifolii in liquid medium, based on the ability of rhizobia to grow in acid media (pH 4.2) containing Al (15 µM), identified 54% of the strains that proved symbiotically acid sensitive. Over 70% of the strains prescreened as acid tolerant ranked in the top half of all strains in total N accumulation in the most acid soil treatment. In some cases acid‐resistant effective strains of R. trifolii formed symbiotic associations that produced between 90 to 99% of the yield of the N‐amended controls.
Performance of Cool‐Season Perennial Grasses in Pure Stands and in Mixtures with Legumes1
Authors: Barnett F. L. , Posler G. L.
Published: July 2010

Clarification of relationships among species in mixed stands is essential to enlightened management of forage mixtures. During 1976–1979, we evaluated several grass‐legume mixtures in a field study in eastern Kansas. Grasses were: commercial smooth brome, Bromus inermis Leyss.; ‘Regar’ Turkish brome, B. biebersteinii Roem. &Schult.; ‘Kentucky 31’ tall fescue, Festuca arundinacea Scbreb.; and ‘Ioreed’ reed canarygrass, Phalaris arundinacea L. Legumes were: ‘Kanza’ alfalfa, Medicago sativa L.; ‘Kenstar’ red clover, Trifolium pratense L.; ‘Dawn’ birdsfoot trefoil, Lotus corniculatus L.; and ‘Emerald’ crownvetch, Coronilla varia L. Each grass was grown in a two‐species mixture with each legume, and in a pure stand with 0 and 90 kg N ha‐1 as NH4NO3. Mixtures were obtained by alternating all‐grass and all‐legume drill rows. Legumes were grown in pure stands in an adjacent planting. Both plantings were on a Woodson silt loam of the fine, mixed, thermic family in the Abruptic Argiaquolls subgroup of the Mollisols. Dry matter (DM) yields were obtained from all plots. Proportion of grass in mixtures was determined from hand‐harvested samples. Dry matter yield of the grass component of each mixture was computed as the product of the DM yield of the whole stand and the proportion of grass in the mixture. Crude protein (CP) contents of whole stands and grass components of mixtures were computed as 6.25 times N. Although comparisons varied across years, mixtures averaged as much grass DM (3.21 Mg ha‐1) as unfertilized all‐grass stands (3.07 Mg ha‐1) during the 4‐year period. Crude‐protein contents of grass components of mixtures consistently ranked above those of unfertilized all‐grass stands; differences usually were significant (P < 0.05) but varied in magnitude with year and type of stand. Legumes differed significantly (P < 0.05) every year in DM yield and every year except 1979 in CP content. Over the 4‐year period, however, no legume was clearly superior in either variable.
Nitrogen Accumulation Rates of Irrigated Maize
Authors: Russelle M. P. , Hauck R. D. , Olson R. A.
Published: July 2010

Improved fertilizer nitrogen (N) use efficiency in irrigated maize (Zea mays L.) often results from delaying application of moderate N rates until the crop is rapidly growing. The objective of this experiment was to determine how N application time, N rate, and planting date influenced the pattern of N and fertilizer−derived N (FN) accumulation in irrigated maize grown on a deep, productive silty clay loam soil (Typic Argiudoll, fine, montmorillonitic, mesic). A factorial combination of early and late planting, N application at planting, or at the 4−, 8− or 16−leaf growth stage, and two N rates (90 and 180 kg N ha−1 as 15N−depleted ammonium sulfate) were applied to the same plots in 1979–1980. Above−ground plant samples were taken at the 8−leaf, l2−leaf, silking, soft dough, and physiological maturity stages of growth. Average net rates of N and FN accumulation were calculated using a temperature index as the divisor. Rates of N and FN accumulation per plant were greatest between the 12−leaf and silking growth stages in 1979, except when N application was made at the 16−leaf stage where maximum accumulation rates occurred during early grain fill. Effects of N application time on N accumulation rates were more pronounced in 1980 and followed patterns similar to those in 1979. Substantial amounts of residual FN from 1979 accumulated in above−ground tissue in 1980. Residual FN uptake was apparently greater, in comparison to newly applied FN, in the heavily−fertilized or late−planted crop. Time of maximum N accumulation was delayed as time of N application was delayed. Grain yield was reduced by early N deprivation only when active N uptake ceased during early grain fill. Excessive N application minimized the effect of application time on final grain FN content. Delayed planting reduced FN recovery at both levels of N fertilization. Relative recovery of FN in maize grain was maximized by applying the low N rate late in vegetative growth, irrespective of planting date.
Competition of Jimsonweed with Soybean1
Authors: Kirkpatrick B. L. , Wax L. M. , Stoller E. W.
Published: July 2010

Jimsonweed (Datura stramonium L.) is a broadleaf weed that has become increasingly severe in Midwest soybean (Glycine max (L.) Merr.) fields (9, 14). Knowledge of the competitive effects of this weed with soybean would be helpful in developing production practices to minimize losses. Our objectives were to determine the response of soybean (cv. Wells) stand and seed yield to (a) various jimsonweed densities, (b) different emergence dates of jimsonweed, and (c) various durations of jimsonweed competition and to compare the effectiveness of bentazon [3‐isopropyl‐1H‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] in controlling jimsonweed to that of hand weeding. Greater densities of jimsonweed resulted in greater losses in soybean yields. Jimsonweed at a low density of 0.3 plants m−1 of row reduced yield by as much as 8%, while jimsonweed at a higher density of 1.6 plants m−1 of row reduced yield by as much as 24%. Increased delay of jimsonweed emergence following soybean emergence markedly reduced soybean yield losses. Jimsonweed at a density of 1.6 plants m−1 of row emerging 2 and 4 weeks after soybean emergence decreased yields by 7 and 3%, respectively, compared to a 23% reduction in yield when jimsonweed emerged with soybean. As duration of competition increased, yields decreased. At a density of 1.6 plants m−1 of row jimsonweed competing with soybean for 2 and 4 weeks reduced yields up to 7 and 14%, respectively. Jimsonweed competing with soybean for the full season reduced yield up to 41%. Soybean stand was not affected by jimsonweed density, time of emergence, or duration of competition. Bentazon was just as effective as hand removal for terminating jimsonweed competition at all application dates.