bluuebunny/crossref_metadata_2025 huggingface dataset:
Planting Patterns and Radiation Interception, Plant Nutrient Concentration, and Yield in Corn
Authors: Ottman M. J. , Welch L. F.
Published: July 2010

The upper leaves of corn (Zea mays L.) are radiation‐saturated while the lower leaves, the prime source of carbohydrates for nutrient uptake by roots, are radiation‐starved. This study was conducted to determine the degree to which planting patterns could influence radiation interception by layers in the canopy, plant nutrient concentration, and yield in corn. Corn was planted in the field in a high‐yielding environment on a Drummer silty clay loam (finesilty), mixed, mesic, Typic Haplaquoll) in 0.38 m single rows, 0.76 m twin rows, 0.76 m single rows, 1.14 m twin rows, and 1.52 m twin rows with 0.13 m between pairs of twin rows. Interception of solar radiation shortly after silking was generally similar for all the planting patterns except for the 1.52 m twin row spacing which intercepted 10% more incident radiation with lower rather than upper leaves compared to the other planting patterns 3 h before solar noon, but allowed 7% more incident radiation to strike the soil surface compared to the narrow row spacings (0.38 ‐ 0.76 m) at solar noon. Planting pattern had no consistent effect on nutrient concentration in the grain, stover, or cob. Grain yields averaged 9.7 Mg ha−1 for the 1.52 m twin planting pattern and 11.7 Mg ha−1 for the other planting patterns. In conclusion, wide row spacings resulted in a partial redistribution of radiation from the upper to the lower leaves but allowed more radiation to strike the soil surface, did not affect plant nutrient concentration, and decreased yield.
Genetic Contribution to Increased Wheat Yields in the USA Between 1979 and 1984
Authors: Feyerherm A. M. , Kemp K. E. , Paulsen G. M.
Published: July 2010

Genetic yield potential of wheat (Triticum aestivum L. and T. turgidum var. durum) and its impact on production need to be documented to determine past and future gains in productivity. This study provides such documentation on growers' yields of wheat from 1979 to 1984 in states where each major class is grown. Cultivar‐specific differential yielding ability (DYA) values were calculated and weighted by sown hectarage to measure state‐wide genetically imputed increases in farmers' yields. Yield increases in spring wheat states ranged from 44 kg ha−1 in Montana to 88 kg ha−1 in South Dakota for the 5‐year period. Increases in the hard red winter region ranged from 40 kg ha−1 in South Dakota to 199 kg ha−1 in Nebraska. Soft wheat yield increases ranged from 211 to 438 kg ha−1 in Corn Belt states and was 151 kg ha−1 in Washington state. We concluded that there has been continued genetically induced improvement in farmers' wheat grain yields during the first half of the 1980s, and that productivity gains should continue at approximately the same rate into the next decade.
Sweet Corn Response to Surface and Subsurface Trickle Phosphorus Fertigation
Authors: Bar‐Yosef B. , Sagiv B. , Markovitch T.
Published: July 2010

High‐frequency phosphorus fertigation may increase the time‐averaged P concentration in the soil solution above that expected from P solubility considerations. Where P is a yield‐limiting factor, frequent P fertigation may increase yield by stimulating P‐uptake by the roots. A field experiment was conducted on a loessial soil (Haploxeralf) high in NaHCO3‐extractable P (0.8 mmol kg−1 soil) to test the hypothesis that subsurface placement of emitters (SSR) is more effective in stimulating P uptake than surface placement (SR). Four concentrations of P in the water (Cp), 0.04,0.16,0.64, and 1.29 mol P m−3, were applied via surface or subsurface emitters to sweet corn [Zea mays (L.) Jubilee]. Marketable ear yield increased with Cp, yielding 22.9,24.3,24.9, and 28.9 t ha−1, respectively. Yield was higher for tricklers placed 30 cm below soil surface (25.2 t ha−1) than on the surface (23.5 t ha−1). Elevated Cp increased the soil solution P concentration, thereby increasing total P uptake and total dry matter production by the plants. Deep trickler placement significantly increased the fraction of total dry matter allocated to the ears, which resulted in higher marketable yield. Subsurface irrigation also reduced weed growth due to the dry top soil during the experiment.
Operational Estimates of Reference Evapotranspiration
Authors: Allen Richard G. , Jensen Marvin E. , Wright James L. , Burman Robert D.
Published: July 2010

Many forms of the Penman combination equation have been proffered for estimating daily evapotranspiration (ET) by the agricultural reference crops grass and alfalfa (Medicago sativa L.). This study was conducted to evaluate popular forms of the Penman equation, and to develop and evaluate general relationships for estimating daily average values of canopy and aerodynamic resistance parameters required by the Penman‐Monteith equation. For simplicity and ease of use, resistance relationships were expressed as linear and logarithmic functions of mean plant height. The Penman‐Monteith and other forms of the Penman equation were compared at 11 international lysimeter sites, with the Penman‐Monteith method and a Penman equation with variable wind function developed at Kimberly, ID providing the best estimates of reference ET across the sites. Ratios of computed alfalfa to grass reference ET during peak months at various locations averaged 1.32, and ranged from 1.12 to 1.43. Values of computed ratios were related to local wind and humidity conditions. The development of relationships for canopy and aerodynamic resistances as functions of reference crop height allowed use of the Penman‐Monteith equation in an operational mode, and improved transferability of this resistance form of the Penman equation to a wide variety of climates.
Trained and Untrained Individual's Ability to Identify Morphological Characters of Immature Grasses
Authors: Fermanian T. W. , Barkworth M. , Lui H.
Published: July 2010

Identifying juvenile grasses is especially difficult because their characteristics are greatly affected by growing conditions. One problem, which affects both computer‐based identification systems and written identification keys, is the inability of users to select the correct alternatives for some morphological characters or structures. This study was designed to determine, for each selected character, whether individuals without training in plant identification could identify each character state correctly as often as trained individuals, and to determine if combining poorly distinguished character states would increase the value of a character for identification of the selected species. seeds or young seedlings of 18 grass species commonly found in turfs of the USA were sown in 125 cm3 plastic plots in a standard greenhouse mix. Untrained participants were students enrolled in an introductory horticulture course on the campus of the University of Illinois and molecularly oriented (not working at the whole plant level) members of the Department of Biology at Utah State University. Observations for trained participants were obtained from sessions held at various locations with faculty members in turfgrass science, plant taxonomists, and graduate students with field experience in grass identification. Considered across all characters, the trained participants selected the correct alternative for a character 59% of the time, the untrained participants 53%. There was no significant association between training group and selection ability for ligule size, sheath, blade width, collar, and pubescence when all species were considered jointly. The frequency with which ligule type was correctly identified was reanalyzed after combining the states of truncate or round and acute or acuminate. This modification increased the frequency of correctly identified, ligule‐type states from 47 to 62% and 31 to 49% for the trained and untrained groups, respectively. On the basis of this study, we would recommend that anyone attempting to construct an identification tool examine both the ability of characters to discriminate among the included species and the ability of expected users to select the correct state or condition of each character.
Alfalfa Persistence and Regrowth Potential under Continuous Grazing
Authors: Smith S. R. , Bouton J. H. , Hoveland C. S.
Published: July 2010

Alfalfa (Medicago saliva L.) generally does not persist well under continuous grazing. Experiments were conducted under continuous grazing to compare the persistence and regrowth potential of an alfalfa germplasm (Georgia—Grazed Collection, GA‐GC), selected for continuous grazing, with two hay‐type (Apollo and Florida 77) and two grazing‐type (Travois and Spredor II) cultivars. The germplasm and cultivars were subjected to continuous, heavy grazing by beef cattle for 18 weeks in each of 3 yr to a height of 3 to 5 cm. Wire exclosures rotated at 28‐d intervals on all plots were used to estimate the regrowth potential of each entry during the grazing period. Plant and stem counts were taken before and after grazing each year as estimates of stand persistence. Cultivars differed significantly for stand persistence after 3 yr of continuous grazing with 6 to 9 plants m−2 remaining for the hay‐type cultivars and 40 to 48 plants m−2 remaining for grazing‐type cultivars. The GA‐GC maintained plant densities of 64 plants m−2 while producing the highest forage regrowth compared with all cultivars. Total nonstructural carbohydrates (TNC) in roots at the end of 1986 and 1987 grazing seasons ranged from 256 g kg−1 for Florida 77 to 429 g kg−1 for Travois, suggesting that grazing tolerance may be related to the TNC concentration in roots of alfalfa that had been heavily and continuously grazed. This study indicates that selection for plant persistence under continuous grazing from a broad‐based population improved the grazing tolerance of the resulting germplasm (GA‐GC) while maintaining the potential for good forage yields.
Assessment of Carbon Allocation with Stable Carbon Isotope Labeling
Authors: Svejcar Tony J. , Boutton Thomas W. , Trent James D.
Published: July 2010

Labeling plants with isotopic forms of C allows many processes important to agriculture and/or natural resource management to be studied. Most C‐labelling experiments have employed radioactive 14C, but in recent years regulatory constraints associated with use of radioactive materials appear to have curtailed studies which may have benefited from 14C labeling. In this paper, we describe a procedure for using the stable isotope 13C for C labelling. By using gas‐isotope‐ratio mass spectrometry, isotopic differences as small as 0.4 µg of 13C could be detected in the 23‐d‐old cheatgrass (Bromus tectorum L.) we used to demonstrate the technique. The procedure is flexible and can be applied to most plant species and a wide range of research objectives. Because 13C is a naturally occurring stable isotope, there are no regulatory problems, environmental hazards, or health risks associated with its use.
Soil Nitrogen Mineralization in the Presence of Surface and Incorporated Crop Residues
Authors: Smith S. J. , Sharpley A. N.
Published: July 2010

The increasing adoption of farming practices which maintain crop residues on the soil surface has created a need for more detailed information regarding associated soil N availability. This study examines the effects of crop residue placement and type on soil N availability for a range of soils. Representative field rates of alfalfa (Medicago saliva L.), corn (Zea mays L.), oat (Avena saliva L.), peanut (Arachis hypogaea L.), sorghum, (Sorghum sudanense (Pipe;:) Stapf.), soybean (Glycine max L.), and wheat (Triticum aestivum L.) crop residues were applied to eight Oklahoma surface soils. The experiment was conducted under aerobic laboratory conditions at 35 °C, and involved 2‐mm soil particles and 0.25‐mm crop residue materials. The N availability was measured on the basis of indigenous and fertilizer‐derived soil N mineralized during short‐ (14 d) and long‐ (84 d) term incubation. Short‐term, an initial depression (more than 80% with corn) in net mineralization occurred with nonlegume residue additions. The depression was enhanced when the residues were incorporated rather than left on the soil surface. The relative depression was greater with the newly formed, fertilizer‐derived soil N than the older, indigenous soil N. On the other hand, N mineralization was enhanced more than 50% with the alfalfa addition. Effects of crop residue type on N mineralization showed ranges up to threefold or more and generally proceeded in the order alfalfa > peanut > soybean > oat ≥ sorghum > wheat > com. Long‐term, N mineralization for all systems was more comparable to that without residue additions.
Tissue Test for Excess Nitrogen during Corn Production
Authors: Binford G. D. , Blackmer A. M. , El‐Hout N. M.
Published: July 2010

Seeming conflict between the need to use N fertilizers and the need to protect groundwater quality requires better tools for distinguishing between fertilizer applications that are essential and those that are excessive. Studies were conducted to evaluate NO‐3 concentration in corn (Zea mays L.) stalks at physiological maturity as the basis for a tissue test to characterize degree of N excess during corn production. Samples of the lower portion of corn stalks were collected from plots in N‐rate experiments at 18 site‐years in Iowa. Observed relationships between grain yields and stalk NO‐3 concentrations indicated sharp breaks between NO‐3 concentrations that were not adequate and those that were adequate for obtaining maximum or near‐maximum yields. When yields were near maximum, stalk NO‐3 concentrations increased linearly with amounts of N fertilizer applied. Stalk samples collected at various times after black layering showed that NO‐3 concentrations remained constant for at least 2 wk. These observations suggest that stalk NO‐3 concentration offers great potential as the basis for a tissue test to characterize degree of N excess during corn production.
Stubble Height Effect on Winter Wheat in the Northern Great Plains: I. Soil Temperature, Cold Degree‐Hours, and Plant Population
Authors: Bauer Armand , Black A. L.
Published: July 2010

Soil temperatures at the crown‐depth of winter wheat (Triticum aestivum L.) that effect winterkill are generally known. In contrast, estimates of the effect that duration of the low temperature has on winter survival have not been published for winterhardy cultivars. Objectives were to relate temperature at the 4‐cm soil depth to winter survival and develop capability to estimate survival based on accumulated cold degree‐hours. Field trials were conducted during a 4‐yr period on Williams loam (fine‐loamy, mixed Typic Argiborolls) at Mandan, ND. Soil temperature at the 4‐cm depth was measured at 2‐hr intervals under three cultivars (Roughrider, Mironovskaya and Centurk) grown on four stubble heights (0, 5, 20, and 36 cm) and with two preplant water levels (0 and 50 mm supplemental water applied 1–2 wk before planting). Based on postwinter pretillering plant populations, complete winterkill was effected at about −20 °C soil temperature for Roughrider and Mironovskaya; Centurk did not survive at −18 °C. Population reductions began to occur when 4‐cm depth soil temperatures were about 7 °C warmer than the lethal soil temperature. Duration of the lethal temperature effecting complete winterkill appears to be a matter of hours, based on cold degree‐ hours lower than a threshold temperature. This information, coupled with that of soil temperatures estimated from models, has utility in predicting degree of potential winterkill and reduction in plant populations.
Temperature and Solar Radiation Effects on Potential Maize Yield across Locations
Authors: Muchow R. C. , Sinclair T. R. , Bennett J. M.
Published: July 2010

The objective of this analysis was to use a simple, mechanistic crop growth model to examine the effects of variation in solar radiation and temperature on potential maize (Zea mays L.) yield among locations. Crop phenology and leaf growth were calculated from daily mean temperature data obtained at the five locations studied. Daily biomass accumulation was calculated by estimating the amount of radiation intercepted and assuming maximum crop radiation use efficiency of 1.6 g MJ−1. Grain yield accumulation was simulated using a linear increase in harvest index during grain filling. Observed and simulated grain yields were compared for several sowings at each of five localions ranging from latitude 14°S to 40°N lat. Averaged across sowings, respective observed and simulated oven‐dry grain yields (g m−2) were 816 and 830 at Katherine, Australia; 953 and 908 at Gainesville, FL; 1059 and 1106 at Quincy, FL; 1091 and 1119 at Champaign, IL; and 1580 and 1626 at Grand Junction, CO. Temperature primarily affected growth duration with lower temperature increasing the length of time that the crop could intercept radiation. The solar radiation response was related to the amount of incident radiation and to the fraction of radiation intercepted by the crop. In the tropics (Katherine), high temperature decreased the duration of growth and grain yield, despite high levels of radiation. Only at locations with low temperature and consequent long growth duration. and with high radiation were maize yields simulated to be more than 1600 g m−2 (300 bushels per acre at 15.5% moisture).
Use of Spectral Vegetation Indices to Infer Leaf Area, Evapotranspiration and Yield: I. Rationale
Authors: Wiegand C. L. , Richardson A. J.
Published: July 2010

Observations of plant canopies in visible and near‐infrared wavelengths and the calculation of spectral vegetation indices from them are now routine, but a unified rationale for interpreting the measurements has been lacking. Herein we present a rationale that links spectral observations to plant processes and express the relationships in equation form. Specifically, the equations relate vegetation indices or cumulative daily vegetation indices to leaf area index, fraction of photosynthetically active radiation that is absorbed, economic yield, leaf mass, aboveground dry phytomass, and evapotranspiration. Data from the literature demonstrate the relationships. The approach, termed spectral components analysis, assumes that crop canopies display the net assimilate achieved in response to growing conditions experienced and that vegetation indices are a measure of the amount of photosynthetically active and transpiring tissue present. It is expected to hold as long as the size of the canopies achieved by the time reproduction begins and the duration/persistence of the canopies limit economic yield, the situation typical of commercial agriculture. The approach provides a basis for using spectral observations to estimate large area yields and to model effects of multiple stresses on crops and forages.
Environment and Genotype Influence on Grain Protein Concentration of Wheat and Rye
Authors: Fowler D. B. , Brydon J. , Darroch B. A. , Entz M. H. , Johnston A. M.
Published: July 2010

Protein is a primary quality component of cereal grains. Protein concentration is influenced by both environmental and genotypic factors that are difficult to separate. In the present study, a series of cultivar and agronomic trials were conducted on several Saskatchewan soil types with the objective of characterizing the influence of genotype and environment on wheat (Triticum aestivum L.) and rye (Secale cereale L.) grain protein concentration and N use efficiency (NUE) for grain protein production. Minimum protein concentration of 95.4 g protein kg−1 dry grain was expressed when cultivars were produced under high productivity conditions on soils with low total plant available N. Minimum protein concentration was maintained until N was no longer the factor most limiting grain yield. At this point, the protein concentration‐N response curve of a cultivar entered an increased phase. Any environmental (e.g., water or time of N availability) or genotypic factor that increased yield potential also increased the amount of N required to initiate the increase phase of the grain protein concentration N‐response curve. Asymptotic maximum protein concentration was determined by both environmental and genotypic factor. Maximum protein concentration at high levels of N varied from 130 to 231 and 107 to 177 g protein kg−1 dry grain for winter wheat and rye, respectively. At low levels of total available N, the NUE for grain protein production approached 80%. The NUE for grain protein production dropped off rapidly for subsequent increments of N fertilizer, approaching zero for maximum grain yield and reaching zero when maximum grain protein yield was achieved. The end of the increase phase of the protein concentration‐N response curve occurred at approximately the same available N level as maximum grain yield. These observations indicate that management systems designed for the production of cereals with high grain protein concentrations will have a very low NUE for grain and grain protein production.
Forage Yield and Quality of Oat Cultivars with Increasing Rates of Nitrogen Fertilization
Authors: Collins M. , Brinkman M. A. , Salman A. A.
Published: July 2010

Forage yield and several quality parameters of oat (Avena saliva L.) have been addressed in the literature, but the effect of N fertilizer rate on forage yield and quality of oat cultivars, and the possibility of cultivar by N interactions, has received little attention. The objective of this study was to evaluate oat cultivar responses to N fertilization when harvested as forage at heading. Nine adapted oat cultivars ranging from early to late in heading date were grown in four field environments from 1982 to 1984 with five N application rates (0, 28, 56, 84, and 112 kg ha−1). Nitrogen application rates up to 84 or 112 kg ha−1 increased forage yield and increased N concentration in two of three environments. Increasing N application rate increased neutral detergent fiber (NDF) 46 g kg−1 in one environment but decreased it slightly otherwise. In three of four environments, forage yield at heading increased (r2 = 0.66−0.94) linearly with later heading date. Nitrogen concentration generally decreased and NDF, acid detergent fiber, and acid detergent lignin concentrations increased with later heading date. The difference in NDF between the earliest and latest cultivars could affect forage utilization by affecting forage intake. In situations where high quality is important, early maturing oat cultivars might be preferable because they produce higher quality forage. Early harvest would also alleviate competition with an underseeded perennial legume earlier in the season. Application of 84 to 112 kg ha−1 of N produces maximum yields and increases N concentration with generally small effects on fiber concentrations and without increasing lodging.
Nitrogen Transfer from White Clover, Red Clover, and Birdsfoot Trefoil to Associated Grass
Authors: Mallarino A. P. , Wedin W. F. , Perdomo C. H. , Goyenola R. S. , West C. P.
Published: July 2010

Information on N transfer from field‐grown forage legumes to associated grass would contribute to elucidation of N budgets and improved N management of pasture mixtures. This research evaluated N transfer by white clover (Trifolium repens L.) (WC), red clover (Trifolium prutense L.) (RC) or birdsfoot trefoil (Lotus corniculatus L.) (BT), grown with tall fescue (Festuca arundinacea Schreb.) (TF) at various legume proportions. Two identical experiments were established on a Typic Argiudoll soil in Uruguay, one in 1983 (Exp. 1) and one in 1984 (Exp. 2), and each was evaluated for approximately 2 yr. The soil of the area was a fine, montmorillonitic, mesic, Typic Argiudoll. Transfer of N to TF was estimated by 15N isotope dilution, using TF grown alone as the reference crop. Mean values for the proportion of grass N derived from legumes (%NT) were 20% for the 60% harvest after seeding, and later increased up to 60%. The increase on %NT over time was greater for WC‐TF and RC‐TF in Exp. 1 and for WC‐TF in Exp. 2. The annual uptake of transferred N (TNY) averaged 18 and 34 kg ha−1 in 1st and 2nd yr, respectively. The WC‐TF mixture usually showed greater annual TNY than RC‐TF on BT‐TF. Transfer by WC in summer often was greater than for RC or BT. Increasing legume proportion generally resulted in linear increases of %NT for the three mixtures, but TNY either did not change or decreased. We conclude that these legumes transferred small amounts of N shortly after seeding, but transfer increased to significant values with time. The concentration of legume‐derived N in TF herbage increased when legume proportion increased, but the amount transferred was not affected or reduced.
Indole Acetic Acid Production by the Fungal Endophyte of Tall Fescue
Authors: De Battista J. P. , Bacon C. W. , Severson R. , Plattner R. D. , Bouton J. H.
Published: July 2010

Increased plant growth and morphological alterations are characteristics of tall fescue (Festuca arundinacea Schreb.) infected with a fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams). A study was conducted to determine if there were ancillary plant growth regulators produced by the endophyte, which could account for these vegetative characteristics. Two endophytes, RRC 401 and RRC 347, were isolated from a rhizomatous and upright growing genotype of tall fescue, respectively. These isolates were cultured on laboratory medium, and extracts of this medium were examined for plant growth regulators using thin‐layer and gas chromatography. Only 3‐indole acetic acid (IAA) was detected in culture extracts of this fungus. The in vitro production of IAA by both isolates was confirmed by gas chromatography‐mass spectrometry. This was the first report of IAA production by this endophyte. Indole acetic acid production varied according to the strain, culture conditions, and age. Indole acetic acid in plant material was quantified with an immunoassay. Attempts to relate free IAA concentrations to altered growth expressions characteristic of endophyte‐infected and noninfected rhizomatous and upright growing genotypes of this grass were inconclusive.
Rice, Mungbean, Soybean, Peanut, Ricebean, and Blackgram Yields under Different Intercropping Systems
Authors: Mandal Bijan K. , Dhara Madhab C. , Mandal Barid B. , Das Swapan K. , Nandy Rita
Published: July 2010

Intercropping provides farmers profit‐oriented and subsistence‐oriented requirements from the same piece of land. The objective of a 2‐yr experiment on intercropping rice (Oryza sativa L.) and legumes was to assess effect on yield in India. Rice was intercropped with mungbean (Vigna radiata L.), soybean [Glycine max (L.) Merr.], peanut (Arachis hypogaea L.), ricebean (Vigna umbellata L.) and blackgram [Vigna mungo (L.) Hepper.] on a well‐drained sandy loam soil in the Gangetic Alluvial Plains (Fleuvudent). Rice/legume planting ratios (row basis) were 2:1, 4:1 simultaneously planted or legumes were planted (2:1 planting ratio) at 30 d after planting of rice (deferred planting). Control plots were monocrops of rice and legumes with each species fertilized according to soil test recommendations. Rice + mungbean, rice + soybean, rice + peanut and rice + blackgram intercroppings resulted in higher yields than that of rice + ricebean intercropping. Rice + ricebean and rice + blackyielded higher when deferred planting was practised. All intercropping treatments of rice + legumes save rice + ricebean (simultaneous planting) were greater in land equivalent ratio (LER), relative net return (RNR), monetary advantage (MA), etc. The competitive ratios (CR) of rice was above one in deferred planting except rice + blackgram and rice + mungbean in 1985 and only rice + blackgram in 1986. Thus, LER, RNR, and MA showed that intercropping of rice + legumes other than ricebean resulted in greater productivity per unit of land than monocultures.
Yield and Botanical Composition of Alfalfa‐Bermudagrass Mixtures
Authors: Brown R. H. , Byrd G. T.
Published: July 2010

The regions of adaptation of alfalfa (Medicago sativa L.) and bermudagrass [Cynodon dactylon (L.) Pers.) overlap in the southeastern USA, but the compatibility of these species in a mixture has not been described. Two field experiments were conducted to compare the yield and botanical composition of alfalfa‐bermudagrass mixtures with each species grown alone. In the first experiment ‘Apollo’ alfalfa was grown alone and in mixtures with ‘Tifton 44’ bermudagrass fertilized with 0 and 100 kg N ha−1, and compared with bermudagrass fertilized with N at rates of 100, 300, and 500 kg ha−1. In a second experiment Apollo alfalfa was grown alone in 15‐cm rows and in 15‐ and 30‐cm rows in mixtures with ‘Coastal’ bermudagrass. Bermudagrass was also grown alone and fertilized with 100, 200, and 300 kg of N ha−1. Yields of the alfalfa‐bermudagrass mixtures averaged 9.7 Mg ha−1 over both experiments and were similar to alfalfa alone (9.2 Mg ha−1). The mixtures also were similar in yield to bermudagrass fertilized with 200 kg N ha−1 in the second experiment (11.2 Mg ha−1) and between yields of bermudagrass receiving 100 and 300 kg N ha−1 in the first experiment. Alfalfa dominated the mixture in both experiments comprising 100% of the forage in the spring harvests, except for the establishment year in the first experiment. The lowest percentage of alfalfa was in August when in 1 yr it reached 53%. Neither N fertilization nor row spacing of the alfalfa affected yield or botanical composition of the mixture.
Corn Response to Rye Cover Crop, Tillage Methods, and Planter Options
Authors: Raimbult B. A. , Vyn T. J. , Tollenaar M.
Published: July 2010

Studies in Ontario have shown that corn (Zea mays L.) yields are reduced when corn is seeded immediately after rye (Secale cereale L.) harvest or chemical kill of winter rye. A study was conducted in 1983 and 1984 on a Maryhill (Typic Hapludalf) loam soil to determine the effect of spring tillage systems and timing of rye chemical kill on the subsequent corn crop. The rye was seeded in early October after corn silage harvest. The tillage treatments consisted of (i) moldboard plow plus secondary tillage, (ii) strip tillage, (iii) notillage with ripple coulters (iv) no‐tillage with disc furrowers plus plow coulters, and (v) no‐tillage with ripple coulters plus plow coulters. The rye kill treatments were early (2 wk before planting) or late dust prior to corn planting). Corn whole‐plant yields averaged 13.6 and 12.4 Mg ha−1 for early and late rye kill, respectively. Corn yield in the moldboard plow treatment was higher than in strip tillage and the average of no‐till treatments; however, using disc furrowers produced yields equal to those with the moldboard plow treatment. Moving the residue out of the row with disc furrowers no‐till treatments with ripple coulters. The improvement in plant growth due to an early rye kill (as opposed to a late rye kill) was often greater with the conservation tillage systems relative to the moldboard plow treatment. A crop production system is proposed involving chemical control of a winter rye cover crop 2 wk before corn planting and planting the corn with a modified no‐till system that removes rye residue from the row area.
Water Use Efficiency of Double‐Cropped Wheat and Soybean
Authors: Daniels M. B. , Scott H. D.
Published: July 2010

Many studies have demonstrated that double cropping wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] allows for greater utilization of natural resources by intensifying cropping practices. A 3‐yr study was conducted on a Captina silt loam (finesilty, mixed, mesic, typic Fragiudult) to determine the water use efficiency (WUE) of winter wheat and to determine the effects of selected management practices on WUE of double‐cropped soybeans. The 3‐yr mean grain yield of wheat was 3170 kg ha−1 and the mean cumulative evapotranspiration (ET) after 1 April was 32.8 cm. This translated into an average WUE of 96.6 kg ha−1 cm−1 of water. Shortly after wheat harvest, the effect of irrigation, planting date, and stubble management on soybean water use and yield were determined. Irrigation significantly increased soybean grain yield in 2 of 3 yr. The 3‐yr yield mean was 2406 and 1704 kg ha−1 for irrigated and non‐irrigated soybean, respectively. When irrigation significantly increased grain yield, irrigated soybean had a highet WUE than non‐irrigated soybean. Planting date had a significant effect on soybean yield and WUE in only 1 of 3 yr and only when planting date was confounded with row‐spacing. Burning of wheat stubble produced significantly higher soybean yields only when herbicide interference by standing wheat stubble was observed. Stubble management had no effect on soybean ET or WUE. The 3‐yr mean WUE for the double cropped wheat and soybean system was 79.3 kg ha−1 cm−1 of water.
Suitability of Corn Growth Models for Incorporation of Weed and Insect Stresses
Authors: Retta A. , Vanderlip R. L. , Higgins R. A. , Moshier L. J. , Feyerherm A. M.
Published: July 2010

Shattercane [Sorghum bicolor (L.) Moench] and second generation European corn borer (ECB) [Ostrinia nubililis (Hubner)] are pests that singly or in combination reduce corn (Zea maize L.) production in the northcentral regions of the USA. Shattercane reduces corn growth and yield because it competes effectively with corn for light and water. Second generation ECB larvae, in tunneling through the vascular system, apparently affect yield by disrupting water and photosynthate movements. Pest models may be linked to physiological models for assessing the effects of pest stresses on corn growth and yield. CERES‐Maize and CORNF corn growth models were chosen to test accuracy and consistency in predicting corn growth and yield parameters. The objectives were to evaluate corn growth models to which pest models could be attached and to test the sensitivity of the selected model to variations in light and water. Simulated leaf area index; vegetative, grain, and total biomass; and yield components were compared to measured data. CERES‐Maize modified for leaf growth and phenology computations (VO/SAT) gave more accurate predictions of date of silking (bias = 1 d) than CORNF (bias = 6 d) or original version CERES‐Maize (bias = −5 d). Accurate estimation of phenology is important because the severity of yield reduction from ECB infestation is dependent on the stage of growth. Sensitivity of VO/SAT to reductions in light and water inputs was tested by simulating combinations of light and water levels ranging from 50 to 100% of actual. A 50% reduction in light resulted in average reductions of 26% in yield, 16% in kernel weight, 16% in kernel number, and 20% in leaf area index. Similarly, a 50% reduction in precipitation resulted in average reductions of 47% in yield, 51% in kernel weight, 1% in kernel number, and 1% in leaf area index. The combination model showed adequate sensitivity to light and water, and thus could be modified to mimic weed competition.
Water Use by No‐Till Winter Wheat Influence of Seed Rate and Row Spacing
Authors: Tompkins D. K. , Fowler D. B. , Wright A.T.
Published: July 2010

Management practices are required in rainfed agriculture of western Canada to reduce early season water evaporation from soil relative to loss by transpiraition. The objective of this study was to measure the effect of two seed rates and two row spacings on the pattern of water use and writer use efficiency (WUE) of no‐till winter wheat (Triticum aestivum L.). Nine field trials were conducted on Udic Haploboroll and Molllic Cryoboralf soils in Saskatchewan from 1987 to 1989. Higher dry matter production and more rapid early season plant ground cover associated with the 9 cm row spacing and 140 kg ha−1 seeding rate, compared to other row spacing‐seeding rate combinations reduced water loss from evaporation and increased the partitioning of evapotranspiration to transpiration during the pre‐anthesis growth period. Pre‐anthesis water use was 11% higher, post‐anthesis wateir use 6% lower, and growing season water use 4% higher for the 140 compared to the 35 kg ha−1 seeding rate, The 140 kg ha−1 seeding rate produced 40% more preanthesis dry matter than the 35 kg ha−1 rate, thus establishing a higher yield potential for the crop. A row spacing of 9 compared to the 36 cm resulted in water use that was 6% higher during the pre‐anthesis, growth period and 3% higher during the entire growing season. The combination of 140 kg ha−1 seeding rate and 9 cm row spacing ultimately produced a 21% higher grain yield and a 9 kg cm‐−1 higher WUE than the combination of 35 kg ha−1 seeding rate and 36 cm row spacing. Grain protein concentration increased from 13.1% with the 35 kg ha−1 seeding rate to 13.9% with the 140 kg ha−1 seeding rate. Grain protein yield increased from 198 to 227 kg ha−1 for the 35 compared to the 140 kg ha−1 seeding rate. The increase in grain protein concentration and yield associated with 140 kg ha−1 seeding rate was related to the pattern of water use by the crop. Even under conditions of high dronght stress, a larger number of more uniformly distributed plants associated with seeding rates higher than 35 kg ha−1 and row spacings narrower than 36 cm resulted in a higher WUE and a water use pattern that produced larger yields and higher grain protein concentration.
Steer Performance in Fescue‐Clover Pastures with Different Levels of Endophyte Infestation
Authors: Fribourg H. A. , Chestnut A. B. , Thompson R. W. , McLaren J. B. , Carlisle R. J. , Gwinn K. D. , Dixon M. C. , Smith M. C.
Published: July 2010

A 3‐yr study was conducted at Ames Plantation, Grand Junction, TN to determine the effects of fungal endophyte (Acremonium conenophialum Morgan‐Jones & Gams) infestation (E+) levels in ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) pastures on steer (Bos taurus L.) performance. Two replications were used of 1.2‐ha pastures overseeded yearly with ladino white clover (Trifolium repens L.) on a fine‐silty, mixed, thermic Typic Hapludalf soil. Yearling tester steers (three per pasture) and additional steers of similar size maintained available forage at heights of 2.5 to 7.5 an. Botanical composition, available forage, average daily gain (ADG), grazing days, and gain per hectare were determined every 21 d; serum prolactin, haircoat roughness, rectal temperatures, and E+ levels were measured at longer intervals. Results were computed using a generalized linear mixed models procedure. Generalized least squares means and standard errors for the broad inference space were estimated (BLUE) and differences for specific linear contrasts were predicted (BLUP). Steer ADG was depressed from over 800 to about 450 g in spring and from about 700 to 400 g during the entire grazing season as A. coenophialum increased from 3 to 81%. Animal grazing days were not different among treatments. Gain was about 65 kg ha−1 more with 22% E+ (379 kg ha−1) than at higher endophyte levels, but it was almost 500 kg ha−1 at 3% E+. Serum prolactin (125 ng mL−1 in steers grazing 3% E+) was halved with 22% E+ and was depressed further at higher E+ levels (41 to 18 ng mL−1). Results suggested that the effect of the endophyte on animal performance in tall fescue‐clover pastures is not linear, with greater depression per unit infestation at lower levels than at higher levels.
Soybean Cultivar Yield Response to Benomyl, Nitrogen, Phosphorus, and Irrigation Levels
Authors: Slater G. P. , Elmore R. W. , Doupnik B. L. , Ferguson R. B.
Published: July 2010

Soybean [Glycine max (L.) Merr.] production for greatest yield involves intensive management of resource inputs. Proper cultivar selection, irrigation, and P application on P‐deficient soils have all been shown to increase yields. Nitrogen applications have resulted in variable yield effects. Under sprinkler irrigation, several diseases caused by species of Diaporthe [D. phaseolorum var. sojae (Lehman) Wehm., and D. phaseolorum var. caulivora Athow. G Caldwell.] and Phomopsis longicolla Hobbs, the Diaporthe/Phomopsis complex may also be yield limiting. This disease complex includes pod and stem blight (PSB), Phomopsis seed decay (PSD), and stem canker. In order to determine the combined influence of cultivar, irrigation level, fertility level, and disease control, field experiments were conducted in 1986, 1987, and 1988 at the South Central Research and Extension Center near Clay Center, NE to evaluate these possible soybean yield limiting factors. All combinations of two levels of benomyl [methyl‐l‐(butylcarlbamoyl)‐2‐benzimidazole carbamate] fungicide (0 and 1.12 kg ha−1 applied at R3 and R5), two levels of N (0 and 134.4 kg ha−1) and P (0 and 67.2 kg ha−1), and two cultivars (determinate Hoyt and indeterminate Zane) were tested at two nonreplicated levels of irrigation. Nitrogen and P application seldom increased seed yield. A yield increase (517 kg ha−1, 1986; 396 kg ha−1, 1987; 215 kg ba−1, 1988) occurred when benomyl was applied to Hoyt soybean under a high level of irrigation. Less of a yield response to benomyl was obtained with later‐maturing Zane, for both cultivars at the lower irrigation level, and during a year of below normal rainfall. Benomyl application decreased the incidence of PSB and increased seed size, but did not consistently affect PSD based on seed appearance. Stem canker was never observed during the course of this study. Yield increases were primarily the result of increased seed size associated with delayed maturity doe to PSB control and increased number of seeds per pod due to benomyl's possible growth regulatory properties. This research indicates that, contrary to previous reports in the northern USA, pod and stem blight can be a yield‐limiting factor with or without the development of Phomopsis seed decay under high‐yield environments.
Multi‐Year Response of Sugarcane to Calcium Silicate Slag on Everglades Histosols
Authors: Anderson D. L. , Snyder G. H. , Martin F. G.
Published: July 2010

Plant crops of sugarcane (Saccharum spp.) grown in the Eveiglades respond to calcium silicate slag. Substantial cost is associated with application of slag. Thus, it is important to know whether yields of successive ratoon crops of sugarcane respond to residual soil Si applied as slag. Our objective was to determine the long‐term response of sugarcane grown on a Terra Ceia muck (euic, hyperthermic Typic Medisaprist) at two locations in the Everglades Agricultural Area to slag applied (0, 2.5, 5, 10, 20 Mg ha−3.1) before either a rice (Oryza sativa L.)/sugarcane rotation or immediately before sugarcane. Slag increased cane and sugar yields as well as tissue Si concentrations. Application of 20 Mg slag ha−1 increased cumulative cane yields as much as 39% and sugar yields as much as 50% over the three crop years. Yield response to slag was generally greater from application immediately prior to sugarcane planting than to the preceding rice rotation crop. Without slag, ratoon yield production decreased as much as 45% in cane and 50% in sugar, whereas with slag, yields decreased only 28% in cane and 29% in sugar. Our data indicate that the critical level for leaf Si may be greater than the previously reported value of 10 g kg−1, and that reduced yields in ratoon crops vs. plant crops were associated with lower Si levels. Consequently, more extensive Si deficiencies may exist in the Everglades than were previously considered. Other yield‐limiting factors such as low soil Mg concentrations were also shown to contribute to the decline of sugarcane ratoon yields.
Yield Potential of Soybean Grown under a Subirrigation/Drainage Water Management System
Authors: Cooper R. L. , Fausey N. R. , Streeter J. G.
Published: July 2010

Combination subsurface irrigation/drainage systems to manage water (add or remove) on poorly drained soils is a relatively new concept in the humid Midwest. The objective of this research was to evaluate the yield potential of a subirrigation/drainage system, when used in combination with a soybean [Glycine max (L.) Merr.] production system with known high yield potential, on a poorly drained soil at Wooster, OH. The water table was maintained on a Ravenna silt loam soil (fine‐loamy, mixed, mesic Aeric Fragiuqualfs) by subirrigation at an average depth of 39 cm. Water table depth ranged from 25 cm over the drain line to 53 cm at the midpoint between drain lines which were spaced 6 m apart. Five cultivars (Sprite, Sprite 87, Hobbit 87, Asgrow 3127, Williams 82) and two row spacings (18 and 76 cm) were compared in 1985 and 1986. In 1987, the five cultivars were all planted in 18‐cm rows and compared at two water table levels (the 1985 and 1986 level and a non‐irrigated naturally varying depth). Averaged over the five cultivars, the constant water table produced a 3‐yr average yield of 5392 kg/ha. In 1987 there was a 2051 kg ha−1 or 58% yield advantage for the subirrigation/drainage system over non‐irrigation (5563 vs 3512 kg ha−1). The 1985, 1986 mean yield advantage for 18cm rows compared to 76‐m rows was 1010 kg ha−1 or 23%. These results indicate that with a properly managed subirrigation/drainage system, combined with a soybean production system with high yield potential, long‐term average soybean yields of 5300 kg ha−1 should be possible in the humid Midwest.
Phosphate Interaction with Uptake and Leaf Concentration of Magnesium, Calcium, and Potassium in Winter Wheat Seedlings
Authors: Reinbott T. M. , Blevins D. G.
Published: July 2010

Low concentrations of Mg and Ca in cool‐season grasses in late fall and early spring are a primary cause of grass tetany and wheat pasture poisoning in grazing cattle. Our objective was to investigate phosphate interaction with the uptake and leaf concentration of Mg, Ca, and K in winter wheat (Triticum aestivum L., cv. Larned) seedlings. Seedlings were grown hydroponically or in pots containing perlite with a solution containing nutrient element concentrations that mimicked the soil solution of a typical midwestern alfisol. Phosphate concentration of this solution was low so that wheat seedlings depleted solution P within a few hours. At low solution P concentrations, Mg and Ca were effluxed from roots. As solution P was increased from 25 to over 100 μM, net uptake of both Mg and Ca was observed over a 48 h period. In 41‐d greenhouse experiments, Mg and Ca concentrations increased and K concentration decreased in the leaf as P treatments were increased. Tetany is likely to occur in ruminants consuming grass with equivalent ratios of K/(Ca + Mg) > 2.2. Increasing P from 50 to 400 μM lowered this ratio from 1.8 to 1.0 and from 1.7 to 1.2 in separate greenhouse experiments. Concentrations of P above 100 μM stimulated net uptake, increased leaf Mg and Ca concentration, and produced leaf tissues with a very low K/(Ca + Mg) ratio.
Subsurface Compaction Reduces the Root and Shoot Growth and Grain Yield of Wheat
Authors: Oussible M. , Crookston R. K. , Larson W. E.
Published: July 2010

The recent use of heavy machinery combined with frequent disk tillage has created a subsurface compacted horizon in many of the irrigated soils of Morocco. The objective of this study was to evaluate the effect of subsurface compaction on the mot and shoot growth, grain yield, and grain yield components of wheat (Triticum aestivum L.). Field experiments were conducted in 1982 and 1983 on a Moroccan clay loam soil (typic Calcixerolls). Soil compaction was artificially created. The 0.10‐m surface layer was removed from all plots with a road scraper. The exposed subsurface layer was then packed by making four passes over the plots with a 7.5‐ton tractor. The removed soil was then replaced and leveled. Control plots were tilled with a disk plow followed by two passes of a disk harrow. Both compacted and control plots were then roto‐tilled for final seedbed preparation. The result of this compaction was a 12 to 23% decrease in grain yield and 9 to 20% decrease in straw yield. The decrease in yield was accompanied by a consistent reduction in the number of shoots per unit area. Number of kernels per spike and kernel weight were unaffected. Both root growth and distribution were markedly changed as a result of subsurface compaction. Wheat plants in compacted plots had a denser, finer, and shallower root system than wheat plants in control plots. Plant height, and leaf area and dry matter per shoot were also unaffected. The decrease in shoot number might be attributed to a limitation in the amount of available soil N to the roots.