bluuebunny/crossref_metadata_2025 huggingface dataset:
An Automated System for Harvesting Wheat Cultivars Grown under a Line Source Sprinkler Irrigation System1
Authors: Gerard C. J. , Worrall W. D.
Published: July 2010

The purpose of this study was to design a fast and accurate method of harvesting cultivars and experimental lines of wheat grown under a line source sprinkler irrigation system. The harvesting system consisted of a strain gauge transducer energized with an amplifier‐indicator mounted on a Hege combine and a millivolt recorder and Omnidata Polycorder (use of trade names does not imply endorsement). Both methods of monitoring the voltage output from the transducer were adequately sensitive to allow continuous harvest and recording of yields at different distances from the line source sprinkler. Use of the polycorder was preferable to the millivolt recorder because data were more rapidly and accurately translated for computer‐assisted statistical analyses. This method will make it possible to quickly measure and compare the differential response of wheat cultivars and experimental lines to moisture stress.
Selective Tall Fescue Control in Kentucky Bluegrass Turf with Diclofop1
Authors: Dernoeden Peter H.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) is an objectionable weed in Kentucky bluegrass (Poa pratensis L.) turf. Currently, there are no herbicides registered for selective control of tall fescue in Kentucky bluegrass. The objectives of these field studies were to determine safe and effective rates of diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy] propanoic acid} for selective control of tall fescue in a ‘South Dakota Certified’ Kentucky bluegrass turf grown on a Chillum silt loam (fine‐silty, mixed, mesic Typic Hapludult). A total of three applications of diclofop during spring and fall at rates of 2.2, 3.4, or 4.5 kg ha−1 provided > 90% tall fescue control. The 4.5 kg ha−1 rate was more effective (98 or 99% control), but normally caused a reduction in Kentucky bluegrass cover. Diclofop was most injurious when applied to Kentucky bluegrass less than one year of age. Mature turf sustained much less injury from high rates of diclofop. The 2.2 kg ha−1 rate was generally safer to the turf than 3.4 or 4.5 kg ha−1, and the level of tall fescue control ranged from 91 to 96%. Diclofop stunted and discolored the Kentucky bluegrass turf. These effects generally persisted for 2 to 3 weeks. More information is needed regarding the relative sensitivities of Kentucky bluegrass cultivars to diclofop, as well as the influence of water dilution on the safety of diclofop's use
Analysis of Primary Spring Growth of Four Pasture Legume Species1
Authors: McGraw R. L. , Marten G. C.
Published: July 2010

Alfalfa (Medicago sativa L.) is the most‐used forage legume in the northern USA; however, it has several shortcomings, especially as a pasture species. Among northern‐adapted forage legume species that are potential alternatives in grazing situations are birdsfoot trefoil (Lotus corniculatus L.) sainfoin (Onobrychis viciifolia Scop.), and cicer milkvetch (Astragalus cicer L.). We conducted an analysis of primary spring growth of these four legumes to determine patterns of dry matter, crude protein (CP), and in vitro digestible dry matter (IVDDM) accumulation. The legumes were established on a Waukegan silt loam (Typic Hapludoll) in late July 1981. Beginning on 10 May 1982 and 1983, total forage was harvested weekly until 28 June when total forage accumulation had decreased. Near infrared reflectance spectroscopy was used to determine CP and IVDDM for leaves, stems, and reproductive parts for each species. All four species reached maximum dry matter accumulation on 21 June. Sainfoin produced the greatest forage dry matter (8.51 Mg ha−1); however, it also had the lowest IVDDM and CP concentration on 21 June. Thus, sainfoin had IVDDM and CP accumulations similar to those of other species. Cicer milkvetch had the greatest IVDDM concentration (67.6 dag kg−1) on 21 June, but its relatively low forage dry matter yield during primary spring growth reduced its IVDDM accumulation to an amount similar to that of the other species. Alfalfa had the greatest CP concentration on 21 June, but its CP yield exceeded only that of cicer milkvetch. None of the four species was definitely superior under these growth conditions. However, birdsfoot trefoil, sainfoin, and cicer milkvetch all showed potential as pasture substitutes for alfalfa, especially in that they did not reach a leaf‐to‐stem ratio of 1.0 or less until considerably later than alfalfa.
Response of Wheat to Irrigation in a Tropical Soil1
Authors: Ghuman B. S. , Maurya P. R.
Published: July 2010

Substantial hectarages of land are planted to wheat (Triticum aestivum L.) every year in northern Nigeria. However, information on scheduling of irrigation for wheat grown in this part of the world is scanty. Field experiments were, therefore, conducted from 1982 to 1984 to study the response of wheat to seasonal and individual irrigations. There were three seasonal irrigations: (i) 300 mm, (ii) 450 mm, and (iii) 600 mm. Each seasonal irrigation was divided into three smaller individual irrigations (30,45, and 60 mm), which were applied at different frequencies. The experimental field soil has a water table that fluctuated between 85‐ and 115‐cm depths during the 1982–1983 and 1983–1984 growing seasons. Dry matter accumulation, plant height, and grain and straw yields were not significantly affected by the depth of seasonal irrigation. However, application of 30 and 45 mm water per irrigation gave higher grain yields than 60 mm. Wheat produced 5 to 6 Mg ha−1 grain when irrigated with 30 mm of irrigation water at 7‐day intervals.
Normal‐12 and Brown Midrib‐12 Sorghum. II. Chemical Variations and Digestibility1
Authors: Akin D. E. , Hanna W. W. , Snook M. E. , Himmelsbach D. S. , Barton F. E. , Windham W. R.
Published: July 2010

Marginally digested tissues in the brown midrib‐12 (bmr) sorghum (Sorghum bicolor (L.) Moench.) mutant are more readily degraded than similar tissues in the normal (N) line. Reduced lignin concentrations have been reported to be a factor affecting digestibility of bmr genotypes, but lignin type could also influence digestibility. The objectives of this work were to (i) examine N‐12 and bmr‐12 plants for variations in chemical composition, including phenolic acids and phenolic structure, using solid‐state nuclear magnetic resonance (NMR) spectroscopy; and (ii) evaluate by microscopy the effect of permanganate delignification. Leaf blades of bmr plants were significantly (Ρ ≤ 0.05) lower in neutral detergent fiber (NDF) and permanganate lignin (PML), and higher in in vitro dry matter digestibility; leaf sheaths contained significantly less PML. Solid‐state NMR spectroscopy suggested that bmr leaf blades had lower amounts of bound syringyl moieties. The predominant alkali‐soluble (1.0 M NaOH) phenolic acids in both plant types were ρ‐coumaric and ferulic acids, and ρ‐coumaric acid was significantly lower (Ρ ≤ 0.05) in concentration in bmr leaves. Treatment of intact blade sections with permanganate to oxidize lignin compounds resulted in a reduced staining intensity for lignin identified by both the acid phloroglucinol and chlorine‐sulfite tests in all but midrib sclerenchyma; lignin staining intensity did not differ between plant types. Degradation of delignified midribs by rumen microbes indicated that the tissues were more degradable in bmr than in N plant types. Results suggest that reduced concentrations of phenolic acids (especially ρ‐coumaric acid) and reduced levels of etherated syringyl moieties in conjunction with reduced concentrations of lignin are factors in the improved quality of bmr‐12 sorghum.
Evaluation of Corn Growth and Productivity with Three Conservation Tillage Systems1
Authors: Al‐Darby A. M. , Lowery B.
Published: July 2010

This study was conducted to provide needed data comparing corn (Zea mays L.) growth and productivity for several conservation tillage (CT) systems. Such data will provide necessary information to better evaluate the economical potential of CT systems in the Northern Corn Belt. The tillage systems used in this study were till‐plant (TP), chisel (CH), no‐till (NT), and conventional (CN) tillage. The study was conducted on a Griswold silt loam soil (fine‐loam, mixed, mesic Typic Argiudoll) at Arlington, WI, and a Plainfield loamy sand soil (sandy, mixed, mesic Typic Udipsamment) at Hancock, WI, over a 3‐yr period. Final plant emergence and growth and yield parameters were measured. The final plant emergence was higher with the CT systems compared to CN at Arlington, while the final plant emergence of the NT system was lower than other tillage systems at Hancock. Plant height, leaf area, and dry matter per plant early in the growing season, for both locations ranked: CN > TP ≷ CH > NT, and in most cases were significantly different. However, at the end of the growing season, these growth parameters were not significantly different. Days from planting to 50% silking for the NT system were significantly delayed by 2 to 3 and 4 days at Arlington and Hancock, respectively. No‐till had the highest grain moisture content. Grain yields with CT systems were equal to or greater than CN tillage at both locations. No‐till grain yield at Hancock was 18% greater than CN when rainfall was below normal in 1983. Three‐year grain yield averages for the silt loam soil were 8.75,8.78,8.97, and 8.49 Mg ha 1 for CN, TP, CH, and NT, respectively. Three‐year grain yield averages for the loamy sand soil were 6.48, 6.48, 6.44, and 6.79 Mg ha 1 for CN, TP, CH, and NT, respectively. The results from this study showed no serious growth and yield reductions with CT systems compared to CN tillage in the Northern Corn Belt.
Forage Quality of Selected Wild Sunflower Species1
Authors: Seiler Gerald J.
Published: July 2010

Although wild sunflower (Helianthus spp.) may be components of pastures, hay, and silage, little information exists on their contribution to overall forage quality. The objective of this study was to evaluate 26 taxa of wild sunflower species for protein and mineral concentrations at various stages of maturity. The field experiment was conducted on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) soil, and the experimental design was completely randomized with three replicates. The leaves and stems of 19 annual and seven perennial taxa of wild species and a commercial sunflower, ‘hybrid 894’, were planted in pure stands and evaluated at vegetative, flowering, and fruiting stages to ascertain their nutritive value for ruminants. Crude protein (CP) of 140 g kg−1 and above occurred in leaves of 19 of 26 taxa (15 were annuals) at the vegetative stage. Nutritionally adequate amounts of Ca (2 to 5 g kg−1) were present in the leaves and stems of all wild sunflower taxa. Nutritionally adequate amounts of Mg (2 g kg−1) and K (8 g kg−1) were present in the leaves of most wild taxa at all stages of maturity. Leaves and stems of most taxa at the flowering and fruiting stages had sub‐optimum P (< 3 g kg 1) levels for high producing ruminants. Nutritionally adequate amounts of CP, Mg, and P were present in whole seeds of most species. At varying maturity stages, nutrient levels of some of the wild sunflower species are comparable to that of cultivated sunflower. Ruminants most likely would not graze pure stands of wild sunflower but would graze in mixed stands with other forbs and grasses. Hence, wild sunflower may be incorporated into hay or silage and provide a satisfactory nutrition level for ruminants.
Growth of Creeping Bentgrass on a New Medium for Turfgrass Growth: Clinoptilolite Zeolite‐Amended Sand1
Authors: Ferguson G. A. , Pepper I. L. , Kneebone W. R.
Published: July 2010

Clinoptilolite zeolite (Z) is a natural silicate mineral with a three‐dimensional lattice, a high degree of internal tunneling, and a large cation exchange capacity and water holding capacity even when particles are sand‐sized (> 0.5 mm). The hypothesis of this study was that clinoptilolite had the facility to preferentially and internally sorb NH+4 where it would be physically protected from microbial nitrification resulting in increased plant fertilizer‐N use efficiency. A field study relating growth and quality of creeping bentgrass (Agrostis palustris Huds.) to ranges of Z amendment of sand and N application rates of 25, 50, or 75 kg ha 1, was initiated at the University of Arizona, Turfgrass Research Center in the spring of 1981. Germination and establishment were significantly increased by amendment of sand with 5 or 10% Z. Bentgrass quality in August 1981 was significantly increased by the 5% Z treatment. The 10% Z treatment initially did not increase turf quality due to the initial high Na content of the Z. However, by January 1982 both Z treatments gave significantly increased turf quality. At this time, excess N reduced turf quality due to high N‐induced iron chlorosis. Clipping yields from seven harvests and N‐use efficiency increased significantly with Z. Zeolite also increased both root growth as indicated by soil organic carbon and shoot‐clipping P content. Excess N decreased root growth. Phosphorus uptake decreased with N during the hot summer months but increased when temperatures were cool. These data indicate that Z has potential as a new medium for the growth of turfgrass.
Application of GOSSYM to Yield Decline in Cotton. I. Systems Analysis of Effects of Herbicides on Growth, Development, and Yield1
Authors: Reddy V. R. , Baker D. N. , Whisler F. D. , Fye R. E.
Published: July 2010

Cotton (Gossypium hirsutum L.) yields have declined since 1965 despite improvements in technology and introductions of higher yielding cultivars. Cotton scientists have been unable to identify exact causes of the yield decline. One suggested cause is the increased use of herbicides and their toxic effects on root growth in the herbicide incorporated zone. In this study, the computerized crop simulation model, GOSSYM, was used to predict cotton performance under several levels of herbicide‐induced root reduction under various environmental conditions in a Leeper clay loam soil (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept). The model predicted a small increase in yield when root reduction was moderate and at shallow depths. However, when the depth of root reduction increased to 200 mm or the percentage of root reduction increased, there was a predicted decrease of up to 40% in cotton lint yield. This decrease in lint yield was much larger when decreased root length was combined with reduced soil water permeability in remaining roots. Predicted yield was also reduced under unfavorable weather conditions. With increase in the depth of root reduction or increase in the percentage of root reduction and with permeability reduction there was a decrease in the root growth throughout the season. Increased N and water shortages were apparent with increase in the depth or level of root reduction. It was concluded that improper application of herbicides was one of the contributing factors for the cotton yield decline.
Response of Susceptible and Resistant Alfalfa Cultivars to Phytophthora Root Rot in the Absence of Measurable Flooding Damage1
Authors: Mueller S. C. , Fick Gary W.
Published: July 2010

Alfalfa (Medicago sativa L.) growth and development is known to be adversely affected by Phytophthora megasperma Drechs. f. sp. medicaginis (Pmm), a root rotting fungus most active under waterlogged soil conditions. The response of the plant to the pathogen under low levels of flooding stress is not well‐established, but that relationship is important during alfalfa establishment on soils flooded for short periods by rainfall. Our main objective was to determine if yield reductions caused by the disease occurred in the absence of yield reductions caused by flooding on seedling alfalfa plants. Controlled environment studies were conducted to quantify the effects of flooding or inoculation with Pmm, or both, on alfalfa yield and disease severity, and to examine the differential response of a susceptible (‘Iroquois’) and a resistant (‘Oneida’) cultivar. At 26°C, one or two 3‐day cycles of flooding with subsequent 4‐day drainage periods did not reduce dry matter yields of alfalfa shoots grown in either soil (mixed, mesic Typic Udipsamment) or vermiculite. Inoculation with Pmm significantly reduced the shoot yield of Iroquois, but not that of Oneida. The presence of an interaction between Pmm inoculation and cultivar in the absence of a flooding × cultivar interaction indicates true disease resistance and not simply increased flooding tolerance in Oneida. Oneida also showed fewer and less severe root lesions than Iroquois. Flooding increased both the incidence and severity of root lesions. The pathogen, Pmm, could be reisolated from root tissue in which disease symptoms were observed. Redox potentials indicated that anaerobic conditions developed quickly in both soil and vermiculite following flooding and that aerobic conditions were reestablished within one day in both media upon draining. Resistance to Phytophthora root rot is of value on new stands subjected to marginal flooding stress.
Relative Sensitivity of Nitrogen and Biomass Accumulation to Drought in Field‐Grown Soybean1
Authors: Sinclair T. R. , Muchow R. C. , Bennett J. M. , Hammond L. C.
Published: July 2010

Evidence of differential sensitivity to drought between symbiotic N fixation and leaf photosynthesis in legumes has been measured under greenhouse conditions. If the greater sensitivity of N accumulation to drought is substantiated under field conditions, then important questions concerning legume production under water‐limited conditions must be considered. Consequently, the relative sensitivity of N and biomass accumulation to drought was examined in a 2‐yr study on ‘Biloxi’ soybean [Glycine max (L.) Merr.] grown in the field on Arredondo fine sand soil (loamy, siliceous, hyperthermic Grossarenic Paleudults). Various irrigation treatments were imposed during vegetative growth after canopy closure when solar radiation was almost fully intercepted. Shoot and root plus nodule biomass and N accumulation were determined from periodic harvests. Solar radiation use‐efficiencies were computed from regressions of biomass against cumulative solar radiation, and were found to range from 0.53 g MJ−1 under daily irrigation, to 0.23 g MJ−1 under the most severe drought treatment. Nitrogen accumulation rates were computed by regression of N accumulation against time, and were found to decline from 0.31 g N m−2 day−1 for the daily irrigation to 0.003 g N m−2 day−1 for the most severe drought treatment. In both years and all three drought treatments, the N accumulation rate was decreased relatively more than the solar radiation use‐efficiency for biomass accumulation. These results indicate that a high sensitivity of N accumulation to soil dehydration may be an important constraint on soybean productivity.
Comparison of Microscopic and Pinitol Techniques in Determining Legume Composition of Steer Diets1
Authors: Forwood J. R. , Stypinski P. , Mawhinney T. , Paterson J. A.
Published: July 2010

Knowledge of botanical and chemical composition of herbage consumed by grazing livestock is essential in understanding animal performance and improving pasture and animal management. Esophageal fistula samples are considered to best represent cattle (Bos spp.) diets, but current microscopic methods used to determine botanical composition are time consuming, expensive, and may be subject to large operator error. Pinitol (1‐D‐3‐O‐methyl‐chiro‐inositol) has been found unique to the leguminosae family and accurate in determining alfalfa (Medicago sativa L.) percentage in greenhousegrown alfalfa‐tall fescue (Festuca arundinacea Schreb.) mixtures (R2 = 0.99). Its utility in estimating the legume composition of esophageally collected grass‐legume samples was compared to that of two widely used microscopic techniques. No significant differences were found between microscopic methods in pasture or hay aftermath of any treatments or dates. Sensitivity analysis showed no differences in the two methods related to their ability to detect dietary legume concentration changes in esophageal samples. Pinitol estimates of legume content were less (P<0.05) than those from microscopic estimates taken from orchardgrass (Dactylis glomerata L.) + legume [red clover (Trifolium pratense L..), birdsfoot trefoil (Lotus sp.), or alfalfa] pasture and hay aftermath, but not from nearly pure orchardgrass. The three methods provided similar estimates late in the grazing season when all values were low. With few exceptions the pinitol method underestimated legume composition of esophageal samples. In a separate experiment, the pinitol content of alfalfa, red clover, and birdsfoot trefoil extrusa after mastication and salivation was lower than that of unfed samples, suggesting that leaching may have been partially responsible for low estimates of legume composition by the pinitol method
A Leaf Area Index Model for Corn with Moisture Stress Reductions1
Authors: Flesch T. K. , Dale R. F.
Published: July 2010

The leaf area index (LAI) of a crop is an input in many agronomic models, but is time consuming to measure. An accurate method of estimating LAI is needed. Using measurements from 72 plots over 17 yr, a model was developed to predict corn (Zea mays L.) LAI based on a normalized thermal crop calendar (NC). The seasonal change in LAI was divided into three periods: 1) planting to silking; 2) silking to the start of rapid senescence; and 3) rapid senescence. The LAI data during the first period were fitted with a logistic function of NC and the maximum leaf area per plant (LAmax) using plot‐years with no moisture stress. The LAmax was predicted using the population density and a hybrid coefficient. The decline in LAI during the second period was predicted with NC, the maximum LAI, and a hybrid coefficient. During the third period, LAI prediction was based on the number of days past the beginning of rapid senescence. Leaf area measurements in plot‐years with moisture stress were used to develop a stress growth factor (SGF) to reduce the growth of LAI in the first period. The SGF was determined from the daily ratios of actual to potential evapotranspiration (ET/PET). Daily ET/PET values < 1.00 reduced LAI growth. Moisture stress did not affect LAI during Periods 2 and 3. The error of predicted LAI for independent plot‐years averaged 19% for the first period, 11% for the second, and 58% for the period of rapid senescence. The model is recommended for broader testing and use.
Planting Date, Row Spacing, and Irrigation Effects on Soybean Grown on Clay Soil
Authors: Heatherly L. G.
Published: July 2010

Because of adverse weather and management decisions, soybean [Glycine max (L.) Merr.] is often planted beyond the period considered optimum. In the southern Mississippi River alluvial plain, this frequently occurs on clay soil. Research was conducted from 1984 through 1986 at Stoneville, MS, on Sharkey clay (very‐fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) to determine the effect of irrigation and row spacing on seed yield and yield components of early or mid‐May versus late‐June plantings of soybean. ‘Braxton’ was planted in 0.53‐ and 1.02‐m‐wide rows and was either nonirrigated or irrigated from the R1 to R6 stages. Irrigation significantly increased yield regardless of row spacing or planting date, but the increase was always greater for early plantings. Seed yields from the irrigated early plantings in 1984,1985, and 1986 averaged 3570, 2960, and 2695 kg ha−1, while the later plantings averaged 3115,1900, and 1425 kg ha−1, respectively. Without irrigation, yield differences between planting dates were not significant. Average nonirrigated yields were 1495,1760, and 185 kg ha−1 for 1984,1985, and 1986, respectively. Narrow rows produced 100 kg ha−1 more seed when averaged over all environments, and row spacing did not significantly alter the planting date × irrigation treatment interaction. Yield increases from irrigation were primarily attributable to increased number of seed. These results show that (i) late planting of soybean on clay soil in either row spacing used will result in significant yield decline even with irrigation, (ii) nonirrigated production of soybean on clay soil is risky, and (iii) choice of row spacing is not as important a consideration as is the alleviation of drought stress on this soil type regardless of planting date.
Supplemental Fertilization of Irrigated Corn Guided by Foliar Critical Nutrient Levels and Diagnosis and Recommendation Integrated System Norms
Authors: Elwali A. M. O. , Gascho G. J.
Published: July 2010

Applying moderate amounts of fertilizers to irrigated corn (Zea mays L.), and making corrections during the growing season as indicated by foliar analysis, is very appealing as a means of reducing risk and increasing fertilizer efficiency, especially on irrigated sandy soils. This study was conducted to determine the relative abilities of the Diagnosis and Recommendation Integrated System (DRIS) and the Critical Nutrient Level (CNL) approach to predict supplemental fertilization needs of irrigated corn based on foliar analysis at the 10‐ or 12‐leaf stage. Three field experiments were conducted on a Bonifay sand (loamy, siliceous, thermic Grossarenic Plinthic Paleudult). Treatment variables in the first year consisted of a factorial combination of two basic N‐P‐K fertilization rates and four supplemental fertilizer treatments applied at the 12‐leaf stage using the DRIS and CNL approaches. In the second and third years, treatment variables consisted of four basic N‐P‐K fertilization levels and six supplemental treatments following foliar analysis at the 10‐leaf stage. Foliar analysis at the 10‐ or 12‐leaf stage was effective for making supplemental fertilizer recommendations for corn. Application of moderate amounts of fertilizers and supplemental applications during the growing season as indicated by both foliar CNL and DRIS norms significantly increased grain yield in two of three experiments. Both CNL and DRIS norms are needed for accurate interpretation of foliar values. Additional studies are needed to increase predictability of supplemental S and Mg applications.
Cotton Response to Planting Date and Mepiquat Chloride
Authors: Cathey George W. , Meredith William R.
Published: July 2010

Few studies have documented the effect of planting date on cotton (Gossypium hirsutum L.) response to mepiquat chloride (MC) (N,N‐dimethylpiperidinum chloride). Planting dates were mid‐April, early May, and mid‐May during 1982, 1983, and 1984, and consisted of five cultivars representing three general maturity types: early—‘DES 422’; intermediate—‘Coker 3131’, ‘Stoneville 825’, and ‘McNair 235’; and full season—‘Deltapine 90’. Mepiquat chloride was applied at a rate of 49 g a.i. ha−1 when the plants had about 0.7 white flowers per meter of row. More parameters were affected by chemical treatment and planting date than by cultivars. Plants were taller and produced fewer flowers, smaller bolls, and less lint as planting dates were delayed. In addition, most boll components were adversely affected by delayed planting dates. However, most of the adverse effects caused by delayed planting were mitigated by the MC treatment. Mepiquat chloride x planting date interactions occurred for plant height, flower production, lint yield, and seed index. Mepiquat chloride caused a 4.5% reduction in lint yield from the early planted plots, and 5.4 and 12.7% yield increases from the optimum and late plantings, respectively. Mepiquat chloride increased boll weight in all plantings, but affected (increased) flower production only in the late planting. Seed index was increased and lint percentage reduced in all MC‐treated plots from each of the three plantings. The MC early, intermediate‐, and late‐planting plots averaged 0.11, 0.25, and 0.30 less height, respectively, than the control plots. Statistical significance was achieved only for the latter two plantings. These studies indicate that MC application would be most beneficial in late‐planted cotton, which tends to produce more vegetative growth than earlier plantings.
Effect of Sampling Period on Nutrient Diagnostic Indices for Burley Tobacco
Authors: Evanylo G. K. , Grove J. H. , Sims J. L.
Published: July 2010

Diagnosis and Recommendation Integrated System (DRIS) norms and critical values are two tools employed in the interpretation of plant analyses. The accuracy of these tools, especially DRIS, depends on their abilities to make diagnoses over time. Changes in values of burley tobacco (Nicotiana tabacum L.) leaf nutrient concentrations, and ratios from 35 d after transplanting (early) to postcuring (late) were examined to determine how the indices might respond as diagnostic norms over time. Total N, P, K, Ca, Mg, CI, and Mo analyses were performed on early and cured‐leaf tissue samples from a 2‐yr field study employing three N rates, four K rates, and two K sources (K2SO4 and KCI). The data were used in DRIS equations to determine the comparative abilities of early and late sampling to predict the order of nutrient limitations. Although sampling period (SP) and SP ✕ fertilizer treatment interactions significantly influenced nutrient concentrations and ratios, DRIS norms were able to make similar nutrient diagnoses on plant tissue sampled early and late. Precise diagnoses employing DRIS ratios over wide time periods can be obtained if large numbers of nutrients are considered simultaneously.
Digestion of Plant Materials for the Determination of Total Nitrogen to Include Nitrate
Authors: Silvertooth J. C. , Westerman R. L.
Published: July 2010

Many modifications in procedures for N determination by Kjeldahl digestion exist. However, few modifications include the quantitative recovery of NO−3–N, which is essential in 15N research. A digestion procedure is described in which reduced Fe and H2SO4 pretreatment is used for the quantitative recovery of NO−3–N. The procedure utilizes an aluminum block digester with a programmable control unit. The recommended program employes a stepwise temperature ramp up to 400°C and continues digestion 1 h after clearing for a total digestion time of 7.25 h. Two other digestion programs were compared with the recommended program. One program used a temperature ramp identical to the first, but digested 2 h after clearing for a total time of 8.25 h. A third digestion program used a shortened temperature ramp, attained a final temperature of 400°C, and was completed 1 h after clearing for a total time of 5.90 h. Wheat (Triticum aestivum L.) grain samples with up to 0.5 mg additional NH+4–N and NO−3–N were used to evaluate these procedures. The recommended procedure provides complete recovery of grain N, and added N with superior levels of precision in comparison to the other digestion procedures evaluated. The digestion procedure using 5.90 h did not yield accurate analysis of grain N, indicating incomplete digestion. The 8.25‐h digestion did not result in improvement of grain N results or added N recovery.
Centipedegrass Response to Foliar Application of Iron and Nitrogen
Authors: Carrow R. N. , Johnson B. J. , Landry G. W.
Published: July 2010

The lawn‐care industry has interest in the use of foliar iron (Fe) to enhance the color of common centipedegrass [Eremochloa ophiuroides (Munro.) Hack.] without using excessive N. We evaluated different Fe carriers, Fe rates, and N rates in three different studies conducted on centipedegrass grown on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult). Minor differences occurred with respect to phytotoxicity but not visual quality or color from ferrous sulfate, ferrous ammonium sulfate, and Sequestrene 330 chelate. When visual quality and color ratings were made at 2 wk or more after application, the highest Fe and N rates always provided the best response. However, initial phytotoxicity [within 1 to 6 d after treatment (DAT)] from Fe and N dictated the use of much lower rates. If applied on a moderately warm day (21–33 °C), the maximum acceptable Fe rate was 2.0 kg ha−1 in combination with 0 or 9.8 kg N ha−1. Centipedegrass could receive up to 39.0 kg N ha−1 without any Fe before N burn was objectionable. On a very hot day (28–37.5 °C), only 0.73 kg Fe ha−1 could be applied with 12.2 kg N ha−1 without objectionable phytotoxicity. The maximum N rate that could be applied alone under these conditions was 24.2 kg N ha−1 before N‐induced phytotoxicity occurred. The 2.0 kg Fe ha−1 rate provided positive visual quality and color responses for up to 35 DAT, while 0.73 kg Fe ha−1 improved color for only 22 DAT. Results show that Fe can improve centipedegrass color, but that centipedegrass is very sensitive to phytotoxicity from Fe. Addition of N further reduces centipedegrass tolerance to Fe.
Nitrogen Argument for Corn Leaf Area Models
Authors: Flesch T. K. , Dale R. F.
Published: July 2010

When soil N fertility is low, it should be considered in predicting corn (Zea mays L.) leaf area index (LAI). Measurements of LAI in 1978, 1979, 1983, and 1984 were used to develop an N growth factor (NGF) to reduce daily LAI increase before silking, based on N fertilizer rate (NR) and LAI in a corn LAI model developed for non‐N limiting conditions. With the NGF there is no reduction in rate of LAI increase when LAI is below a critical value (LAICNR) determined by NR. After LAI exceeds LAICNR, NGF reduces the rate of LAI increase according to NR. After silking there was no apparent N effect on the rate of LAI decline. A LAI prediction model using NGF was tested against independent LAI measurements in 1985, including data from plots receiving no N fertilizers. The LAI prediction errors were less than 20% for most of the season. This empirical NGF is a method to lower LAI predictions for corn with low N applications in models in which N fertility has not been considered.
Planting Seed Density in Relation to Cotton Emergence and Yield
Authors: Hofmann W. C. , Kittock D. L. , Alemayehu M.
Published: July 2010

Cotton (Gossypium hirsutum L.) planting seed density has been related to seedling emergence and vigor, although its effects on yield are not clearly understood. Seed lots of the cultivar ‘DP90’ were separated into four density classes using a gravity separation table. These seed classes were evaluated along with an undivided seed sample and a sample from processed seed selected for commercial use. The seed classes were planted at three planting rates in seven tests conducted from 1983 to 1985 at Maricopa, Marana, and Safford, AZ. The soils at these locations are Typic Camborthids, Thermic Torrifluvents, and Typic Torrifluvents, respectively. The lowest density seed had significantly lower standard and cold germination test results; however, there were no differences among the other five seed classes in 2 of the 3 yr. Field emergence of the highest density seed was significantly greater than that of the other density classes for the seven tests combined, and was significantly lower for the lowest density seed. Lint yields produced by plants from the highest density seed were significantly greater than those of the four other seed classes, and the lowest density seed produced significantly lower yields. There were no significant interactions between planting seed density and planting rate for yield. The results indicate that cotton planting seed quality could be improved slightly by selecting higher density seed
Seed Reserves and Seedling Development in Winter Wheat
Authors: Peterson Curt M. , Klepper Betty , Rickman R. W.
Published: July 2010

Seed reserves are essential for germination of cereals including wheat, but the contributions of the endosperm and its associated aleurone layer to postgermination seedling development remain to be elucidated. Winter wheat (Triticum aestivum L. em Thell. ‘Stephens’) was grown for 36 d in a controlled environment from kernels of three sizes, and from kernels where part of the endosperm had been excised prior to sowing to study the contributions of seed reserves to seedling development. Excision of endosperm delayed the first two phyllochrons, prevented outgrowth of the coleoptilar tiller, and slightly delayed the appearance of the next two tillers. Plant dry weight, leaf numbers and dimensions, number of nodal roots, and total number of tillers were all affected by endosperm excision. The combined area of the first two leaves was linearly correlated with aleurone area for all seed treatments. Areas of later‐formed leaves and final dry weight of seedlings were directly related to the areas of the first two leaves. Thus, the aleurone layer, in addition to seed reserves, is important for the enlargement of the first two leaves, with subsequent seedling development controlled by the size of the first two leaves under the conditions used in this study.
Resin‐Coated Urea Evaluation for Turfgrass Fertilization
Authors: Hummel N. W.
Published: July 2010

New resin coatings have been developed for producing slow‐release fertilizers for turfgrasses. It is important that new fertilizer materials be evaluated so that recommendations can be made for their use. Four experimental resin‐coated ureas (RCU) were evaluated for maintenance fertilization of Merion Kentucky bluegrass (Poa pratensis L.) turf grown on an Arkport sandy loam (coarse‐loamy, mixed, mesic Psammentic Hapludalfs). The RCUs had an analysis of 41% N and laboratory release rates of 270 d (RCU‐270), 100 d (RCU‐100), and 70 d (RCU‐70). A mixture of the RCU materials (RCU‐M), sulfur‐coated urea (SCU), urea, a 22–1.8–6.6 with 10% by weight dicyandiamide (DCD), and oxamide were included for comparison. The fertilizers were applied at an annual rate of 196 kg N ha−1, as single‐spring or split‐spring, and fall applications. The most rapid response to fertilization as measured by fresh weight yields and color ratings was produced by urea, followed in order by SCU, RCU‐70, and RCU‐100. The release rate of RCU‐270 was too slow to produce acceptable color ratings through much of the test at both fertilization times. The most uniform response was produced by RCU‐100 at both the single‐spring and split treatments. The highest N recovery in the leaf tissue was obtained from oxamide (24 and 59%), the single‐spring application of SCU (27 and 58%), and the split applications of RCU‐100 (21 and 52%) and RCU‐70 (25 and 54%). Nitrogen recovery from SCU was highest in growth periods immediately following fertilization, while recovery was more uniform across growth periods with the RCU‐100. Certain RCU fertilizers are well suited for turfgrass fertilization.
WEEDER: an Advisory System for the Identification of Grasses in Turf
Authors: Fermanian T. W. , Michalski R. S.
Published: July 2010

To effectively control weeds found in a turf it is first necessary to correctly identify them. A computer program, WEEDER, was built using the artificial intelligence system AGASSISTANT to provide a means for effectively identifying grass weed and turf species through the recognition of selected variables. WEEDER has a rule‐based, non‐hierarchical knowledge base concerning 37 grass species commonly found in turfs throughout the USA. Each species is represented by 11 or fewer variables. In order to measure the value of WEEDER for identifying unknown grasses in comparison to a commonly used method, the dichotomous identification key, 41 volunteers were assigned to one of two groups; (i) those with any previous experience in plant diagnosis or any formal training in plant science; and (ii) those with no experience or training. Each individual identified four unknown grasses; creeping bentgrass (Agrostis palustris Huds.); perennial ryegrass (Lolium perrene L.); zoysiagrass (Zoysia japonica L.); and large crabgrass (Digitaria sanguinalis [L.] Scop.) using WEEDER or a printed identification key. The maximum mean of either group to identify a grass species was 55% of the specimens, which were examined by participants with plant science training using WEEDER. Participants with some plant science training had a higher mean identification of each species (23% identified) than participants with no training (18%) when using the identification key. Little difference in their ability to identify the unknown species was found between the two groups when they were using WEEDER. There was a significant increase in the mean ability of all participants to identify an unknown grass using WEEDER (50%) rather than the identification key (20%) after rules for the four species were modified. A demonstrated advantage of WEEDER over the printed key was its ability to be easily modified to increase its usefulness. The mean percentage of correctly identified grasses by all participants increased from 11 to 50% after rules pertaining to the unknown grasses were modified to reflect variable values most consistently selected. No significant dependency on a participant group was found for correctly identifying a grass species when using WEEDER after the rules were modified. Further testing of WEEDER is required to determine if the modified rules are consistent with additional grass sample and user populations.
Soil Properties' Role in Stem Canker Infection of Soybean
Authors: Rhoton Fred E.
Published: July 2010

Stem canker [Diaporthe phaseolorum (Cke & Ell.) Sacc. var. caulivora Athow and Caldwell] is a destructive disease of soybean [Glycine max (L.) Merr.] that can unpredictably increase from negligible amounts to near total infestation within a year. An understanding of the soil environment's contribution to these outbreaks is essential to any comprehensive stem canker research program. This study was designed to assess the relationship between several soil properties and different disease levels occurring over a range of soil conditions. Experimental plots were established at six sites that differed in depth of past erosion. A high‐fertility status (P, 140 kg ha‐1; K, 280 kg ha‐1) was maintained on one half of the plots at each site. The remaining plots were left unamended. Visual estimates of stem canker infection levels in 1986 equalled 72 and 86% for the fertilized and unfertilized treatments, respectively, at the slightly eroded site. Estimates for similar treatments at the most severely eroded site were 3 and 2%, respectively. Regression analysis indicated that soil organic matter content, pH, and soil water accounted for 66% of the variability in infection levels among the differentially eroded sites; whereas, plant residues from the previous crop year had no influence. Higher infection levels associated with the unfertilized plots were significantly correlated (P < 0.01) with lower concentrations of K in the soybean plants. These results indicate that greater stem canker infection levels can be expected on soils with higher organic matter, pH, and soil water content, and on soils that contain lower amounts of potassium.
Growth, Grain Yield, and Tissue Mineral Concentration of Corn Treated with Ethephon
Authors: Bullock D. G. , Raymer P. L.
Published: July 2010

Corn (Zea Mays L.) lodging limits grain yield (yield) in the southeastern USA. Ethephon (2‐chloroethyl‐phosphonic acid) can reduce lodging, but its effect on tissue mineral concentration is unknown. The objectives of this study were to measure the effect of ethephon application rate and time on mineral concentration of tissue, yield, and lodging of corn. Field experiments were conducted during 1986 and 1987 on a Dothan loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudults). Three corn hybrids were planted as a four ✕ three factorial of rate (0, 0.14, 0.28, and 0.56 kg ethephon ha−1 and application time (1 to 2 cm long developing tassel as Time 1; Time 1 + 6 d; Time 1 + 12 d). Yield and grain moisture decreased as rate increased. Plant and ear height decreased as rate increased, and the magnitude of the inhibition increased as application time was delayed. Earleaf concentration (ELC) of N, P, K, Ca, S, B, and Cu; and grain concentration of N, P, K, and Mg increased (7 to 20%) as rate increased. Except for Zn ELC and K ELC, time did not affect mineral concentration.
Tillage Effects on Grain Yields in a Wheat, Double‐Crop Soybean, and Corn Rotation
Authors: Wagger M. G. , Denton H. P.
Published: July 2010

Crop rotations in conjunction with the appropriate tillage system can be an important means for enhancing crop yields in the southeastern USA. The objective of this study was to determine the grain yield response in a wheat (Triticum aestivum L.), double‐crop soybean [Glycine max. (L.) Merr.), corn (Zea mays L.) rotation for different tillage sequences of conventional tillage (CT) and no‐tillage (NT). The four tillage sequences were; (i) continuous NT for all three crops; (ii) wheat CT, soybean NT, corn NT; (iii) wheat CT, soybean NT, corn CT; and (iv) continuous CT for all three crops. A field experiment was conducted for 3 yr on a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Hapludult) and an Aycock fine sandy loam (fine‐silty, siliceous, thermic Typic Paleudult) at North Carolina Piedmont and Coastal Plain locations, respectively. Notillage corn and soybean yields were greater than those in CT systems every year at the Piedmont location. Averaged over a 3‐yr period, these yield increases due to NT were 32 and 43% for corn and soybean, respectively. Corn and soybean yields were less affected by tillage at the Coastal Plain location, with NT yields greater than CT yields in only one year out of three for each crop. In general, wheat yields tended to be lower in a NT system at the Piedmont location, averaging 9% lower than CT wheat over a 2‐yr period. Yield increases for NT corn and soybean were attributed primarily to greater soil moisture availability as a result of reduced runoff. Tillage in the previous crop/year had little effect on grain yields.
Soil Potassium Distribution in Grazed K‐31 Tall Fescue Pastures as Affected by Fertilization and Endophytic Fungus Infection Level
Authors: Wilkinson S. R. , Stuedemann J. A. , Belesky D. P.
Published: July 2010

Fertilizer requirements of grazed pastures may be influenced by the spatial distribution of nutrients in animal excreta. This experiment was conducted to determine the effect of two levels of fertilization and endophytic fungus (Acremonium coenophialum Morgan‐Jones et Gams) infection of Kentucky‐31 tall fescue (Festucu arundinacea Shreb) on the lateral and vertical distribution of soil K after 3 yr of grazing. Each pasture consisted of 0.7 ha of a Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Hapludult,) and was grazed using the put‐and‐take method. Forage was removed only by grazing. Endophytic fungus levels were 20% (Low endophytic fungus, LE) and 52% (high endophytic fungus HE), and fertilizer rates were 134‐15‐56 kg N‐P‐K (Low fertilizer LF), and 336‐37‐139 kg N‐P‐K ha−1 yr (high fertilizer HF) in a 2 ✕ 2 factorial replicated twice in a randomized block design. Each pasture was divided into 12 zones with each zone sampled separately to a depth of 122 cm before the grazing experiment began and then annually for 3 yr. Potassium did not accumulate in the majority of the pasture area at either fertility level except near the waterer, mineral feeder, and shade. Potassium accumulation rates in this area, determined by linear regression, were 7, 23, 23, and 46 kg K yr‐1 for LELF, LEHF, HELF, and HEHF treatments, respectively. These amounts were equivalent to 18, 24, 59, and 47% of the fertilizer K applied to the 0.7 ha pastures for the LELF, LEHF, HELF, and HEHF treatments, respectively. This accumulation was a result of animal grazing and resting behavior. Much of the K accumulated below 15 cm. Transfer of K by grazing steers to camping zones and subsequent leaching increased with fertility level and endophyte infection level. This redistribution reduces effectiveness of K recycling under grazing, and increases fertilizer K requirements in non‐camping zones.