bluuebunny/crossref_metadata_2025 huggingface dataset:
Fall Armyworm Resistance in Corn and Its Supression of Larval Survival and Growth1
Authors: Williams W. Paul , Davis Frank M. , Wiseman Billy R.
Published: July 2010

The fall armyworm [Spodoptera frugiperda (J. E. Smith)] is a serious pest of late planted corn (Zea mays L.) in the South; however, corn genotypes which show reduced leaf feeding damage have been developed. To study the effects of corn genotypes with and without resistance to leaf feeding by the fall armyworm on larvae development, field tests were conducted at Mississippi State, Miss. and Tifton, Ga. in 1980 and 1981. Experiments at Tifton were grown on a Tifton loamy sand (fine‐loamy, siliceous, Thermic, Plinthic Paleudult), and the experiments at Mississippi State were grown on a Leeper silty clay loam (fine, montmorillonitic, nonacid, thermic, Vertic Haplaquepts). Standard corn production practices were followed although soil insecticides were not applied. Fall armyworm larvae were placed in the whorls of susceptible and resistant corn genotypes at the 5 and 10‐leaf stages of growth. Fewer larvae were recovered from the resistant than the susceptible genotypes 8 days after infestation. Larvae produced on the resistant corn genotypes were also smaller than those produced on susceptible genotypes. Both number of surviving larvae and larval weights were highly correlated with leaf feeding ratings. Selections for reduced larval survival and growth, as well as reduced leaf feeding damage, should enhance efforts to develop corn genotypes with higher levels of resistance to fall armyworm.
A Plot Planting System Utilizing a Rear‐Engine Tractor1
Authors: Oplinger E. S. , Wright J. P. , Klassy A.
Published: July 2010

To meet the demands of several cultivar evaluation projects, a plot planting system utilizing a rear‐engine tractor was developed. Important design criteria were that it be adaptable to several different row spacings and row numbers, that it use only one seed packet per plot, and that it be easily transported. The equipment developed uses a 20 kw rear‐engine power unit equipped with a three point bitch behind the front axle. Seed is metered through a cone to a spinning divider which can be fitted with interchangeable heads to divide the seed into two to nine rows. Interchangeable tool bars, one equipped with double disc drill openers, the other with unit‐planters permit planting, as many as, nine 18‐cm rows, or as few as, two 95‐cm rows. The planting system has been used successfully for several crop evaluation trials, population and row width studies.
Copper Status of United States Soils and Forage Plants
Authors: Kubota Joe
Published: July 2010

Plants with few exceptions are the primary sources of dietary Cu of grazing animals. Levels of Cu in plants are important to ruminant animals because the utilization of Cu is tied closely to that of Mo. Copper concentrations in forage plants grown on a wide range of U.S. soils were determined, and a summary is presented in this report. A geographic pattern of Cu concentration across the USA is illustrated in map form, using legumes as the test crop, and Cu levels of 6 mg kg−1 or less, 6 to 10 mg kg−1, and 10 to 12 + mg kg−1. The Cu concentrations in grasses were low, so their Cu concentrations were summarized separately from those of the legumes. The Cu concentration in neither the legumes nor the grasses, however, strongly reflected the Cu status (total) of soils. Compared with the geographic distribution pattern of Mo in U.S. forage plants, the pattern of Cu was quite diffuse due mainly to the narrow range of Cu in plants. An understanding of plant sources of Cu is important because ruminant animals grazed in parts of the USA suffer from molybdenosis, a Mo induced Cu deficiency disease. Animals afflicted with molybosis require supplemental Cu in addition to Cu from plant sources.
Root System Characteristics of Two Soybean Isolines Undergoing Water Stress Conditions1
Authors: Garay A. F. , Wilhelm W. W.
Published: July 2010

Environmental stress may have a differential influence on root development of soybean [Glycine max (L.) Merr.] isolines which vary in pubescence density. Root length density and root dry matter distribution as a function of depth and distance from the row were determined for two isolines of ‘Harosoy’ soybean in association with an experiment designed to evaluate the influence of epidermal pubescence on root development, water use, and photosynthetic characteristics of the two isolines. The isolines, Harosoy normal (HN) and Harosoy dense (HD), differed in the density of trichomes on the epidermal surfaces of leaves, stems, and pods. The study was conducted at the Univ. of Nebraska Field Laboratory at Mead, Nebr., during the 1980 growing season. Root samples were collected 47 (full bloom) and 78 (beginning seed) days after planting. Until the first sampling, soil water content was high at all depths, and roots were concentrated in the surface 0.15‐m layer, especially under the row. Eighty percent of the roots were found within the upper 0.30 m. By 78 days after planting and after 30 days of drought, root length density was greatest at the 0.90 to 1.20‐m layer; 80% of the roots were found within the 0 to 1.2‐m layer; and uniform lateral distribution was observed. Harosoy dense pubescence isoline tended to have a greater root density, to explore deeper into the soil, and to extract more soil water during the drought than did the normal pubescence isoline. However, the rate of water extraction (per unit root length) was greater for the HN isoline.
Relation of Agronomic and Multispectral Reflectance Characteristics of Spring Wheat Canopies1
Authors: Ahlrichs J. S. , Bauer M. E.
Published: July 2010

Remote sensing technology is nearing operational use for area estimation of wheat (Triticum aestivum L.). However, the relationships between crop canopy variables such as leaf area index (LAI) which might be used in large‐scale applications of growth and yield models of wheat and other crops and their multispectral reflectance properties are not well defined. The objective of this investigation was to identify these relationships and assess the potential for estimating selected canopy variables from remotely sensed reflectance measurements. Reflectance spectra over the 0.4 to 2.5 µm wavelength range were acquired during each of the major development stages of spring wheat canopies at Williston, N.D., during the 1975, 1976, and 1977 seasons. The soil was a Williams loam (fine‐loamy mixed typic Argiboroll). Treatments in the experiment included planting date, N fertilization, cultivar, and soil moisture. Agronomic characterization of the canopies included measurements of development stage, plant height, fresh and dry biomass, LAI, and percent soil cover. Correlation and regression analyses were used to relate the agronomic variables to reflectance factor. High correlations were found between reflectance factor and percent soil cover, LAI, biomass, and plant water content. A near infrared wavelength band, 0.76 to 0.90 µm, was most important in explaining variation in green LAI and percent soil cover, while a middle infrared band, 2.08 to 2.35 µm, explained the most variation in fresh and dry biomass and plant water content. Transformations, including the near infrared/red reflectance ratio and greenness index, were also highly correlated with canopy variables. The relationship of canopy variables to reflectance was influenced by the development stage of the crop and decreased after anthesis. The canopy variables could be accurately predicted using measurements from three to five wavelength bands. The reflective wavelength bands of the thematic mapper sensor were more strongly related to and better predictors of the canopy variables than the Landsat MSS bands.
Fruiting of Cotton. II. Effects of Plant Moisture Status and Active Boll Load on Boll Retention1
Authors: Guinn G. , Mauney J. R.
Published: July 2010

abstract

Yield of cotton (Gossypium hirsutum L.) is proportional to the number of fruits (bolls) produced, which is a function of flower production and boll retention. It bas been known for many years that a severe water deficit decreases boll retention, but tbe reports did not indicate a critical plant water status below which field‐grown plants lost bolls. Field experiments were conducted with 'DPL 70' cotton on an Avondale clay loam (a member of the fine‐loamy, mixed, hyperthermic family of Typic Torrifluvents) to a) quantify the relationship between leaf water potential (xylem pressure potential) and boll retention, and b) to assess the importance of boll load in modifying the results. Two irrigation levels were compared through the season. Boll retention was high early in the season at midday leaf water potentials from −1.4 to −1.9 MPa, but decreased when the leaf water potential decreased below about −1.9 MPa. Boll retention decreased as boll load increased. Because water deficit decreased flowering and boll retention, it limited the boll load. The feedback effect of boll load on boll retention tended to counteract the effect of water deficit on boll retention. Water deficit decreased yield, in part because of decreased flowering and in part because of decreased boll retentio
Leaf Gas Exchange in ‘Caucasian’ Bluestem in Relation to Light, Temperature, Humidity, and CO21
Authors: Coyne Patrick I. , Bradford James A.
Published: July 2010

abstract

Leaf gas exchange was measured in glasshouse‐grown Old World bluestem [Bothriochloa caucasica(Trin.) C. E. Hubb cv. Caucasian] as a function of light, temperature, humidity, and CO2to provide a database for developing a model to aid in deriving specific genotypeenvironment combinations that result in optimum forage production. The CO2resistance pathway was partitioned into stomatal (r′sand residual (r′r) components and a water‐use efficiency index (r′s/r′twhere r′2= r′s+r′t) was calculated. Maximum CO2exchange rates (CER) were 40 µmol m−2s−1which are above the average of published rates of numerous C4 perennial grasses. Maximum r′s/r′twas about 70% of the theoretical potential and was markedly superior to comparable values from the literature. The r′s/r′tratio declined rapidly as temperature was decreased or increased from the optimum for maximum CER (36 °C) due to the greater temperature sensitivity of r′gcompared to r′s. The ratio of r′s/r′rwas greater than unity for temperatures greater than 20 °C and photon flux densities greater than about 150 µmol m−2s−1and maximum r′srrat high light and Toptwas about 2.5. Increasing the leaf‐air vapor pressure difference (VPD) resulted in linear reductions in CER and stomatal conductance (Ca). The decrease in CER per unit reduction in Ca(ratio of regression slopes) resulting from the imposition of atmospheric water stress increased from 2.3 at 15 °C to 4.2 at 35 °C showing increased stomatal control of CO2uptake as temperature was increased. Stomatal behavior may vary with growing conditions, but in this experiment, stomates did not operate to maintain internal CO2constant independent of ambient CO2and light. Caucasian bluestem's high CER and r′srtare consistent with its demonstrated forage production potential. Together, these attributes suggest a promising role for the Old World bluestems (Bothriochlocr spp.) on marginal cropland sites in the Southern Plains to complement and supplement native range.
Rapidly Determining Sorghum Canopy Photosynthetic Rates with a Mobile Field Chamber1
Authors: Garrity Dennis P. , Sullivan Charles Y. , Watts Darrell G.
Published: July 2010

Progress in characterizing the photosynthesis of plant communities under field conditions demands simple, rapid methods for determining CO2exchange rates in the field. With conventional flow‐through gas exchange systems, difficulties are faced because of the need for an electrical power source to operate the analyzer in the field and the lack of mobility of this multiple component system. Recently, a technique was developed for precisely measuring CO2concentrations of small gas samples collected in medical syringes. We describe the design and operation of an assimilation chamber that adapts this technique into a rapid and mobile method for canopy photosynthesis measurements on grain sorghum [Sorghum bicolor(L.) Moench). The chamber and all accessories can be hand‐carried by two people. Two to 3 min are required to sample the photosynthetic rate of a 0.86 m length of crop row at any given location. The chamber is constructed of acrylic plastic with aluminum reinforced corners. A unique ventilation system was designed using an exhaust blower powered by a lightweight 12 v battery. The differential in CO2concentration between air samples drawn at 0 and 60 s provided the basis for canopy apparent photosynthesis determinations. Diurnal measurements of the canopy photosynthesis of sorghum under different soil moisture regimes on two dates are reported. The convenience and mobility features of the method suggest numerous applications in field investigations where conventional CO2exchange systems are impractical.
Physiological Response of St. Augustinegrass to Irrigation Scheduling
Authors: Peacock C. H. , Dudeck A. E.
Published: July 2010

Irrigation is an integral part of a turfgrass management program and accounts for a large part of the energy inputs on a turf area. As potable water supplies decrease, use of limited water will impose stress on turfgrass areas which may result in reduced quality. Research on irrigation practices should help to minimize the effects of water stress resulting from reduced irrigation frequency. Response of St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze] to irrigation scheduling was studied during the summers of 1980 and 1981 on a loamy, siliceous, hyperthermic Grossarenic Palendult soil. An irrigation schedule of 2‐, 3‐, 4‐, and 6‐day intervals simulated conditions ranging from grass being under no water stress to severe water stress. Field plots were constructed to maintain an undisturbed soil profile that horizontally isolated adjacent plots to prevent lateral water movement. Irrigation treatments were implemented by irrigating with evapotranspiration estimates of 0.64 cm day−1in 1980 and 0.38 cm day−1in 1981 at either 2‐,3‐,4‐, or 6‐day intervals. Plots received equal volumes of water, only irrigation timing was varied. Turfgrass swards were evaluated on 12‐day cycles under water stress prior to irrigation and after 24 h of recovery following irrigation. Measured parameters included turfgrass quality, carbon exchange rates (CER), evapotranspiration rates (ET), plant water potential component changes, and leaf diffusive resistance, and transpiration. Irrigation scheduling affected many of the parameters studied. The 6‐day irrigation schedule caused a reduction in CER and ET and concurrent increase in stomatal resistance and a loss of turgor pressure prior to irrigation. Following irrigation, CER and ET increased, turgor pressure increased, and diffusive resistance decreased during each 12‐day cycle. When averaged over the entire study period preirrigation values of CER, ET, leaf water potential components, and transpiration were lowest and diffusive resistance highest for the 6‐day schedule, and these increased or decreased during recovery following irrigation. Even under the most severe conditions of 0.38 cm of water day−1applied every 6 days, the sward remained in positive carbon balance. Turfgrass quality and percent cover were not affected by irrigation treatments. Scheduling irrigation every 6 days with 2.3 cm of water will not affect St. Augustinegrass turf quality if adequate mowing height is maintained.
Adventitious Rooting in ‘Hopi’ Sunflower: Function and Anatomy1
Authors: Rogers C. E. , Unger P. W. , Kreitner G. L.
Published: July 2010

The ‘Hopi’ sunflower (Helianthus annuusL.) is a primitive openpollinated variety that produces numerous adventitious buds (nodules) on exposed lower stalks under greenhouse conditions. Similar conditions do not induce such budding in more advanced hybrids. The root buds remain dormant when exposed to air, but begin rapid growth into adventitious roots when covered with damp soil. Objectives of this study were to determine the effects of adding basal soil around stalks of Hopi and hybrid ‘894’ sunflower on adventitious root development, contribution of the roots to plant standability, and anatomy of the roots. The addition of one or two 100‐mm layers of soil around lower stalks induced significantly more (1% level) adventitious root growth above the original soil level on stalks of Hopi variety than on hybrid 894 stalks. When the addition of soil was delayed until plants were flowering, extensive adventitious rooting still occurred in Hopi sunflower, but little occurred in hybrid 894. Applying horizontal forces to stalks 0.3 and 0.6 m above the original soil level caused significantly less stalk deflection in Hopi than in hybrid 894 plants. The greater resistance to stalk deflection in Hopi was attributed to greater plant stability furnished by more extensive adventitious rooting. Anatomical studies revealed that the internal anatomy of adventitious roots was nearly identical to the internal anatomy of primary roots for both Hopi and hybrid 894. Roots of hybrid 894 had larger intercellular spaces in the cortex and a higher xylem to cortex ratio than comparable roots of the Hopi variety.
Effect of Fungicides and Herbicides on Nodulation and N2 Fixation in Soybean Fields Lacking Indigenous Rhizobium japonicum1
Authors: Rennie R. J. , Dubetz S.
Published: July 2010

Growing soybeans [Glycine max(L.) Merr.] under irrigation requires the use of herbicides and seed‐applied fungicides to control weeds and root diseases. Soils in southern Alberta contain no indigenous Rhizobium japonicumand thus inoculation is essential to the establishment of a successful N2‐fixing symbiosis in soybeans. Unfortunately, these chemicals may be incompatible with survival of the inoculated rhizobia. Accordingly, an evaluation was made of the effects of three seed‐applied fungicides, captan {N‐[{(trichloromethyl) thio]‐4‐cyclohexene‐l,2‐dicarboximidef}, thiram [bis(dimethylthiocarbamoyl)disulfide], and carbathiin (5,6,‐dihydro‐ 2‐methyl‐l,4‐oxathiin‐3‐carboxanilide); four herbicides applied as preplant incorporated, chloramben (3‐amino‐2,5‐dichlorobenzoic acid), linuron [3‐(3,4‐dichIorophenyl)‐l‐methoxy‐l‐methylurea], metribuzin [4‐amino‐6‐tert‐butyl‐3‐{methylthio)‐as‐triazin‐5(4H)‐on], and trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine); and one post‐emergence herbicide, diclofop {2‐[4‐(2,4‐dichlorophenoxy) phenoxy]propanoic acid}, on shoot N, seed yield, nodulation, acetylene‐reducing activity (ARA), and 15N‐determined N2fixation of soybean line ‘King Grain X005’ inoculated with granular rhizobial inoculant. The soil was an irrigated Chin loam (Typic Haploboroll).

None of the fungicides or herbicides affected seed yield. Thiram and captan applied at 1.0 g kg−1seed reduced shoot N yield at anthesis but a lower rate of thiram (0.54 g kg−1seed) increased N yield. None of the fungicides affected ARA. Metribuzin applied at recommended rates caused erratic germination. Linuron significantly reduced ARA whereas trifluralin stimulated it in 1 year but had no effect in the other year. This alteration in ARA was not reflected in N or seed yield. 15N isotope dilution at levels of 15N natural abundance showed the plant received approximately 50% of its N from N2fixation at anthesis, and in agreement with ARA, showed no effect of chemical when proper rates were applied. We conclude that these herbicides and seed‐applied fungicides have no effect on nodulation and N] fixation under these experimental conditions when granular inoculant is applied.
Cultivar and Management Effects on Stand Persistence of Birdsfoot Trefoil1
Authors: Beuselinck P. R. , Peters E. J. , McGraw R. L.
Published: July 2010

Interactions between growth habit and management of birdsfoot trefoil (Lotus corniculatusL.) are reported by other researchers to affect stand persistence. Stand persistence dependent on the longevity of plants within the stand can be confused with the persistence of stand resulting from natural reseeding in this crop. A field test of 10 birdsfoot trefoil cultivars differing in growth habit was planted in May 1979 on Mexico silt loam (Fine, montmorillinitic, mesic Udollic Ocharqualf) near Columbia, Mo. Commencing April 1980, effects of four management treatments on stand persistence were studied to determine the degree of emphasis to be given to growth habit in a program of genetic improvement for trefoil persistence. Volunteer seedling establishment was controlled with simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine]. Significantly lower herbage yields in stockpiled and unharvested managements were attributed to foliar blight caused by Rhizoctonia solaniKeuhn. Stand persistence, based on plant counts, was observed to be independent of management since plants within stands behaved more like biennials than perennials regardless of management. Cultivar by management effects on stand persistence were not significant (P>0.05). An average stand reduction of 90% was observed from April 1980 to 1982. Greatest reductions in stand counts were observed each year between April and October. An average disease score of 2.4, where 0 indicated root and crown tissues visibly free of decay and 5 indicated extensive decay, was obtained from 939 surviving plants examined in April 1982. Poor stand persistence could be explained in part by the foliar, crown, and root diseases found at the study site. Lack of differences in stand persistence and tolerance to disease may reflect the close ancestry of the entries tested. Emphasis on growth habit in a genetic improvement program for persistence in the Southern Corn Belt appeared less important than an examination of genetic resources for lowered susceptibility to disease.
Effects of Solar Radiation Regimes on Growth and N2 Fixation of Soybean, Cowpea, and Bushbean1
Authors: Eriksen F. I. , Whitney A. S.
Published: July 2010

Legumes are commonly grown in the tropics under reduced solar radiation due to dense cloud cover and shading from plantation or tall intercrops. This paper examines the growth and N2 fixation of several grain legumes common to the tropics on an Oxic Haplustoll in Hawaii. Plantings were made in April (warm season) and November (cool season) of soybean (Glycine max L. Merr.) ‘Kahala’; cowpea (Vigna unguiculata Walp.) ‘TVu 1190’ (April) and ‘TVu 4557’ (Nov.); and bushbean (Phaseolus vulgaris L.) ‘Burpee Tenderpod’. Polypropylene netting was used to obtain 27, 45, 70, and 100% of the incoming solar radiation through the entire crop cycle. Consistent shading effects were with the three legumes during both warm and cool seasons even though absolute yields were lower in the cool season due to daylength and temperature sensitivity in soybean and cowpea. Nitrogen fixation parameters generally followed dry matter (DM) and seed yields. Total nodule activity (TNA) was very low in all the legumes at 27% sun. With the exception of bushbean at 27% sun, shading caused an 34% average reduction in DM and grain yields, vs a 50% reduction in TNA, and a 76% reduction in nodule mass. Soybean TNA peaked 3 to 4 weeks after flowering, cowpea (cool season) TNA peaked at flowering, and bushbean TNA peaked slightly before or at flowering. There was a tendency for a delay (≈ 2 weeks) at 70, 45, and 27% sun in the final stages of TNA, for summer and cool‐season soybean and bushbean. These delays were not noted for cowpea or cool‐season bushbean. Of the three legumes, cowpea was the least shade tolerant. It produced more DM at full sun than either soybean or bushbean, but at 27% sun, DM yields were similar for all three crops. The response of soybean to shade was intermediate with no reduction in DM and grain yield at 70% sun. Bushbean was the least affected by shading; in fact, maximum yields were obtained at 70% sun. At full sun, their leaves were yellow and seed weight was low; this problem could be corrected by N fertilization.
Prediction of Animal Performance on Bermudagrass Pasture from Available Forage1
Authors: Guerrero J. N. , Conrad B. E. , Holt E. C. , Wu H.
Published: July 2010

Bermudagrass [Cynodon dactylon (L.) Pers.] is a major warmseason perennial grass grown on improved pastures in the South. Available forage and its digestibility vary widely in a normal grazing season on bermudagrass pasture. A method is needed to predict steer (Bos sp.) gains from the amount and digestibility of available forage. Five bermudagrass cultivars differing in digestibility were grazed at different grazing pressures to produce four levels of available forage. Forage was classified by concentration of in vitro digestible dry matter (IVDDM) as high (>600 g kg−1 IVDDM), medium (530 to 600 g kg−1 IVDDM), or low ( <530 g kg−1 IVDDM) digestibility. At each level of IVDDM, average daily gain (ADG) of steers was fitted to an asymptotic function of available forage. On high, medium, and low digestibility forages, approximate asymptotic ADG values were 0.94, 0.74, and 0.31 kg, and 68,83, and 89 g forage kg−1 body weight day−1, respectively, were needed to produce the asymptotic ADG values. For steers to maintain their weight on high, medium, and low digestibility forage, 14,18, and 43 g forage dry matter kg−1 body weight day−1, respectively, must be present. Because the quantities of available forage required for maximum steer gains or even for maintenance were far in excess of what the steers could physically consume, it appears that opportunity for selective grazing is necessary.
Reduced Seedbed Tillage Effects on Irrigated Sugarbeet Yield and Quality1
Authors: Halvorson A. D. , Hartman G. P.
Published: July 2010

Field studies were conducted from 1979 through 1982 on a furrow irrigated silty clay loam soil (Typic Argiboroll) to determine if sugarbeet (Beta vulgaris L.) sucrose production levels could be maintained with reduced seedbed tillage. Tillage treatments were: a) conventional tillage (CT)—complete fall incorporation of surface residues; b) strip tillage (ST)—fall incorporation of surface residues in 18‐cm wide bands located 56 or 61 cm apart; and c) no‐tillage (NT)—no incorporation of surface residues. Herbicides were fall applied for weed control. Sugarbeets were seeded 10 or 15 cm apart to eliminate need for thinning. Sugarbeet stands before cultivation averaged 3.7 sugarbeets/meter of row over the 4‐year period. Tillage treatment had no significant effect on spring soil temperatures and on sugarbeet stand, root yield, sucrose content, gross sucrose yield, and recoverable sucrose yield when averaged over the 4‐year period. Sugarbeet quality, in terms of clear juice purity, tended to be better in the reduced tillage treatments than in the CT treatment. This difference in clear juice purity probably resulted from the higher levels of spring soil NO3‐N found under CT than under reduced tillage plots. The results indicate that sucrose production under reduced seedbed tillage conditions can be maintained at levels comparable with conventional seedbed tillage conditions. Potential advantages of reduced seedbed tillage for sugarbeets are wind erosion control, reduced soil crusting problems, better soil water conditions in the seedbed for germination, reduced energy requirements, and reduced production costs.
An Analysis of Post‐Anthesis Sink‐Limited Winter Wheat Grain Yields Under Various Environments1
Authors: Shanahan J. F. , Smith D. H. , Welsh J. R.
Published: July 2010

Better understanding of the frequency of post‐anthesis sink‐limited winter wheat (Triticum aestivum L.) grain yields is needed in selecting genotypes with high yield potential and yield stability. Field studies were conducted at four locations (the major soil types were mesic, Aridic Paleustolls and mesic, Aridic Argriustolls) in eastern Colorado over the two cropping seasons of 1976–1977 (1977) and 1977–1978 (1978), using yield and yield component analysis, to determine the effect of sink limitations. Three hard red winter wheat cultivars were grown under four N fertilizer rates at each location to increase variation in grain yield and yield components. Variation was observed for grain yield and the yield components of spike no. (spike no. m−2), kernel no. per spike, kernel no. (kernel no. m−2), and kernel size (mg kernel−1) across locations. Grain yield and yield component variation, due to cultivars or N treatments, were observed at six of the eight sites. Variation in grain yield within and across sites was more consistently correlated with kernel no. than kernel size. These results strongly suggest that wheat grain yields may be sink‐limited during grain filling over a wide array of environments. Variation in kernel no. within locations was more consistently correlated with kernel no. per spike than spike number, while variation in kernel no. across locations was more highly associated with spike no. than kernel no. per spike. Thus, both yield components were important in establishing sink capacity under the variable environmental conditions of this study.
Soybean Canopy Growth, Photosynthesis, and Transpiration Responses to Whole‐Season Carbon Dioxide Enrichment1
Authors: Jones Pierce , Allen L. H. , Jones J. W. , Boote K. J. , Campbell W. J.
Published: July 2010

Soybeans [Glycine max (L.) Merr. cv. Bragg] were grown throughout their life cycle in six controlled‐environment chambers that maintained CO2 concentrations at 330,450,600, and 800 µmol CO2 mol−1 air. Air temperatures were controlled, and solar radiation and dewpoint temperatures were measured continually for each chamber. Net photosynthesis and transpiration were computed on 5‐min intervals. The CO2 enrichment had no apparent effect on the rate of mainstem node development, but leaf area increased at a faster rate proportional to the CO2 concentration. Daytime CO2 exchange rate (CER) increased with increasing CO2 and followed the same trend as final yield. Midday CER was typically about 90 µmol CO2 m−1 of ground area s−1 for 800 µmol mol−1 and 60 µmol CO2 m−2 ground area per second for 330 µmol mol−1 chambers. Canopy transpiration rates, leaf area index and vapor pressure deficits were used to compare bulk canopy resistances among CO2 treatments. Bulk canopy resistance (stomatal and boundary‐layer) of the 800 µmol mol−1 treatment was about 1.6 times that of the 330 µmol mol−1 CO2 treatment. These results imply that the expected continued increase in global atmospheric CO2 will increase both agricultural productivity and water use efficiency.
Effects of Municipal Wastewater Effluent and Cutting Management on Root Growth of Perennial Forage Grasses1
Authors: Clapp C. E. , Newman T. C. , Marten G. C. , Larson W. E.
Published: July 2010

Municipal wastewater effluent studies have not evaluated perennial forage root growth at different effluent rates or cutting sequences. Our primary objective was to ascertain whether root length and mass of perennial grasses, that are tolerant of wastewater effluent, but that yield differently depending on frequency of cutting, are influenced by effluent application or cutting frequency. The two, three, or four‐time year−1 cutting sequence had little effect on root length or dry weight, whereas wastewater treatment levels caused significant root differences. The high effluent (10 cm week−1) treatment produced less root length and root mass in all four species compared with the control and low effluent (5 cm week−1) treatments. When high levels of effluent were applied, reed canarygrass (Phalaris arundinacea L.) had the greatest root length and mass, whereas orchardgrass (Dactylis glomerata L.) had the least; tall fescue (Festuca arundinacea Schreb.) and Kentucky bluegrass (Poa pratensis L.) had intermediate root production. Although orchardgrass produced significantly fewer roots than did reed canarygrass, previous work had shown the aboveground yields of these species were comparable. Also, the high effluent treatment produced the greatest yield of aboveground dry matter, the finest roots, the least root dry matter, and lowest rooting density. We concluded that root mass or length were not primary determinants of forage production of adapted perennial grasses when ample water and nutrients were provided by wastewater effluent.
Leaf Area Index and Dry Biomass of Taro1
Authors: Shih S. F. , Snyder G. H.
Published: July 2010

Taro (Colocasia esculenta) is a wetland plant that can be used as a fuel stock for biomass conversion into various energy forms. Predicting the biomass production is important in developing the optimal harvesting schedule, but information needed to predict production is unavailable. The objective of this study was to predict the tare biomass production based on leaf area index information. Cultivar Lehua Maoli was planted with a space of 0.5 m between plants in 1981. In 1982, the same cultivar was planted with spaces of 0.2, 0.4, and 0.6 m between plants. Dry biomass and leaf area (LA) were monitored monthly in 1981 and bimonthly in 1982. Leaf area was best estimated from leaf dry biomass (LDB) by the equation LA = 223 LDB (r2=0.91). Dry biomass was linearly related to cumulative monthly mean leaf area index until cumulative monthly mean leaf area index reached 10 (r2=0.80 to 0.97). These relationships could be useful for predicting taro biomass production, both as a research tool and as a guide for scheduling commercial harvest.
Moisture Sensor‐Controlled Irrigation for Reducing N Leaching in Bermudagrass Turf1
Authors: Snyder G. H. , Augustin B. J. , Davidson J. M.
Published: July 2010

The study was conducted to determine the feasibility of using a tensiometer‐controlled irrigation system to reduce N leaching in turfgrass while maintaining acceptable growth. Bermudagrass (Cynodon dactylon × C. transvaalensis) was grown on a sand soil (Pomano fine sand, a siliceous, hyperthermic Typic Psammaquent) during a series of 2‐month (bimonthly) cycles. Irrigation was applied either daily (Daily irrigation), or when permitted by tensiometer soil moisture sensors (Sensor irrigation). Nitrogen at the rate of 5 g m−2 month−1 was applied bimonthly as NH4NO3, (AN) or sulfur‐coated urea (SCU), or as NH4NO3, through the irrigation system with each irrigation (Fertigation). The effect of these treatments on turfgrass color, clipping weights, and on tissue N content were measured. Nitrogen was determined in soil water samples obtained on a near daily basis from below the rootzone using ceramic cup suction lysimeters. Nitrogen leaching ranged from 56% to less than 1% of that applied, depending on treatment and cycle. The AN source combined with Daily irrigation produced the greatest N losses (22 to 56%), and Fertigation with Sensor irrigation produced the smallest losses ( <l to 6). Sensor irrigation reduced N leaching from all N sources. For SCU and Fertigation with Sensor irrigation, the peak and average N concentrations were less than 0.9 and 0.3 mmol L−1, respectively, whereas for AN these values were as high as 2.8 and 1.0, respectively. The combination of Sensor irrigation and fertilization by Fertigation or SCU produced the least N leaching while maintaining acceptable turfgrass growth and quality.
Yield Components Associated with Soybean Yield Reductions at Nonoptimal Planting Dates1
Authors: Board J. E.
Published: July 2010

Expansion of the optimal planting dates for soybean [Glycine max (L.) Merr.) would allow for more flexibility in management to fit into weather and cropping patterns. A field study was conducted to determine yield components associated with soybean seed yield reductions at nonoptimal planting dates in the southeastern USA. This information provides insight into how seed yield reductions occur at nonoptimal planting dates. Optimal planting period in the area is between early May and early June. Cultivars Forrest, Tracy‐M, Centennial, Davis, Ransom, Bragg, and experimental genotype D77‐12480 were planted at early April (nonoptimal), mid‐May (optimal), and mid‐June (nonoptimal) planting dates in 1981 and 1982 at Baton Rouge, LA (30° N Lat) on an Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalf) soil. At maturity, plant samples were separated into main and branch stem components. Main and branch stem length, branch number, node number, fertile node number, pod number, pods per fertile node, seed per pod, seed size, and seed yield were determined. In all genotypes, seed yield reduction at the mid‐June planting date was related to a decline in branch seed yield associated with a reduction in number of branches and branch nodes. The decreased number of fertile branch nodes resulted in fewer branch pods and seed. Davis and D77‐12480 showed no seed yield reduction at the early April planting date. Reduced seed yield of the other genotypes at the early April planting date was related to a reduction in branch nodes and proportion of the branch nodes that were fertile. The decreased number of fertile branch nodes resulted in fewer branch pods and seed. In conclusion, seed yield reduction at nonoptimal planting dates was associated with reductions in branch rather than main stem yield components.
Mycorrhizal Colonization of Crested Wheatgrass as Influenced by Grazing1
Authors: Bethlenfalvay G. J. , Evans R. A. , Lesperance A. L.
Published: July 2010

Vesicular‐arbuscular mycorrhizal (VAM) fungi play a role in crop productivity and soil stability in agricultural ecosystems. This role is accentuated under adverse cultural or climatic conditions, such as grazing or drought. The purpose of this study was therefore to assess the effects of stress (grazing) on VAM‐fungal colonization of a major forage species. Changes in root colonization of crested wheatgrass [Agropyron desertorum (Frisch.) Schult.] plants by VAM fungi were measured under three levels of grazing pressure, ranging from no grazing to heavy, continuous grazing. Percent colonization of root length was determined by microscopy, and VAM‐fungal biomass spectroscopically. These findings were related to the changes in root/shoot ratios caused by grazing. The study site is characterized as a Wyoming big sage brush (Artemisia tridentata spp. Wyomingensis) ‐ grassland community on an Abgese loam (fine‐loamy, mixed, mesic Xerollic Haplargid) soil in central Nevada. Plants studied were introduced previously as part of a range improvement program. Colonization of root length declined significantly (P < 0.05) and seasonally (40.2%, June and 50.6%, October) in plants under heavy grazing as compared to ungrazed plants. Spores (60.8% June and 89.5% October) and biomass (35.0% June and 61.5, October) of the VAM fungi also declined with grazing. Colonization of wheatgrass was favored when the amount of photosynthetic tissue relative to root mass was high. Phosphorus concentration in plant tissues was not significantly affected (P < 0.05) by grazing. It is concluded that severe grazing adversely affects the colonization of crested wheatgrass by VAM fungi. This reduction in the fungal symbiont may have an effect on plant nutrition and soil structure and stability which needs further investigation.
Cicer Milkvetch and Alfalfa as Influenced by Two Cutting Schedules1
Authors: Gabrielsen B. C. , Smith D. H. , Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) is a promising forage legume, but little is known about its response to cutting. A 2‐year study was conducted at Fort Collins, CO, on a Nunn clay loam (fine, montmorillonitic, mesic Aridic Argiustoll) soil to compare yield, quality, and trends in carbohydrate reserves of cicer milkvetch and alfalfa (Medicago sativa L.) in response to annual three‐ and four‐cut clipping treatments. Quality was evaluated by determining concentrations of crude protein (CP) and cell wall constituents (CWC) in herbage from each harvest. Seasonal dry matter yields of alfalfa were similar under both clipping treatments during each year. Yields of cicer milkvetch were reduced under the more frequent cutting schedule in 1979, but not in 1980. During 1979, quality differences between the clipping treatments were apparent for alfalfa but not for cicer milkvetch. Improved quality, as measured by increased CP and decreased CWC concentrations, was observed in herbage from both species under the more frequent clipping treatment in 1980. Herbage CP concentration was simiilar under comparable clipping treatments during both years, however, the CWC concentration of cicer milkvetch was consistently lower than that of alfalfa. Cyclic trends in carbohydrate reserves were observed in alfalfa under both clipping treatments in 1980, but only under the three‐cut treatment in 1979. Carbohydrate reserve trends in cicer milkvetch roots and rhizomes were less cyclic than in alfalfa and similar under both cutting schedules each year. Carbohydrate reserve concentrations in all forage entries were similar at the end of the 1980 growing season regardless of clipping treatment. Following cutting, carbohydrate reserves in alfalfa were readily utilized during the initial period of recovery. Carbohydrate reserves in cicer milkvetch appeared to be actively involved in regrowth processes only when little, or no, residual leaf area remained after cutting.
Potassium Fertilization of Alfalfa Grown on a Soil High in Potassium1
Authors: Barbarick K. A.
Published: July 2010

Most Colorado soils contain adequate levels of plant‐available K. This study investigated the influence of up to 750 kg K ha−1 on four semidormant varieties of alfalfa (Medicago sativa L.) grown on a soil high in K (Nunn clay loam—Aridic Argiustoll) over 4 years. Fertilizer K significantly increased dry matter yield for the first 2 years and significantly increased the total alfalfa yields for the entire duration of the study. The overall yield response, however, was not cost efficient based on current K fertilizer costs. Along with the yield increases, K fertilizer consistently decreased Na plant concentrations, Na uptake, and soil levels of Na. It is postulated that the additional K suppressed Na uptake which possibly resulted in greater N2 fixation and dry matter production. A greenhouse study using four rates of K and Mg applied as K2SO4 and MgSO4, respectively, showed that both materials equally reduced Na uptake and increased yields of the ‘Baker’ cv. Consequently, the yield response to applied K in the field was not a nutritional response to K but resulted from the suppression of Na uptake. This K‐Na interaction produced significant yield responses in the field and the greenhouse even though the Nunn soil (a fine, montmorillonitic, mesic Aridic Argiustoll) is a non‐sodic soil.
Continuous Tillage and Rotation Combinations Effects on Corn, Soybean, and Oat Yields1
Authors: Dick W. A. , Van Doren D. M.
Published: July 2010

Few studies report long‐term effects of various tillage and crop rotation practices. Studies were conducted to compare the relative ability of various tillage and crop rotation combinations (3 ✕ 3 factorial) to sustain corn (Zea mays L.), soybean (Glycine max L.), and oat (Avena sativa L.) yields. The tillage and rotation combinations were continuously applied for more than 20 years to a well‐drained Wooster silt loam (fine‐loamy, mixed, mesic Typic Fragiudalf), an imperfectly drained Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf), and a very poorly drained Hoytville silty clay loam (fine, illitic, mesic Mollic Ochraqualf). Tillage treatments were no‐tillage; plow and then plant; and plow, disk, and plant. Rotation treatments on the Wooster and Hoytville soils included continuous corn, corn and soybean in a 2‐year rotation, and corn‐oats‐meadow in a 3‐year rotation. Only continuous corn was grown on the Crosby soil. Corn yields were always positively influenced by no‐tillage on the Wooster soil and negatively influenced on the Hoytville soil. The results obtained for the Crosby soil were mixed. The average yearly corn yield increase and decrease due to no‐tillage on the Wooster and the Hoytville soils were 1070 kg ha−1 and 503 kg ha−1, respectively. The negative response to no‐tillage on the Hoytville soil was primarily due to the large decrease in yield obtained as a result of the continuous corn rotation treatment (average annual yield decrease, 880 kg ha−1). Yield responses of soybean and oats on the Wooster and the Hoytville soils were similar to those observed for corn. When Phytophthora root rot resistant (tolerant) soybean cultivars were grown on the Hoytville soil with the standard cultivars which had been used during most of the experimental period, yield differences between the no‐tillage and plow treatments were essentially eliminated. This study suggests that yield reductions of corn and soybean associated with no‐tillage on heavy clay, very poorly drained soils may be reduced by rotating crops and/or by the use of disease resistant cultivars.
Cotton Response to Mepiquat Chloride1
Authors: Kerby T. A.
Published: July 2010

The potential for mepiquat chloride (1,1‐dimethylpiperidinium chloride) to control excess vegetative growth and increase yield of cotton (Gossypium hirsutumL.) was evaluated under a wide range of environmental conditions in 35 replicated experiments conducted in the San Joaquin Valley of California from 1979 to 1983. Predominant soils were thermic Xeric Torriorthent's and typic Torriorthents. Yield response to mepiquat chloride (MC) has varied in production fields as well as in these tests. The focus of this study was to identify those variables which have contributed to the variability observed. Plot size among experiments varied from 15 m2to 1.3 ha. Mepiquat chloride was applied at 49 g ha−1when bloom counts reached 0.7 white blooms m−1row and plant height was between 46 to 61 cm. Overall, MC treated plots yielded 1309 compared to 1299 kg ha−1lint for control plots and the yield response varied significantly among experiments. Forty‐six percent of this variability could be accounted for by number of heat units for the growing season and by the final plant height of control plants. Yield increases occurred when the growing season was short or when final height of control plants was either shorter or taller than normal. Yield decreases occurred when heat units ranged between 2600 to 3000 and final control plant height ranged from 90 to 110 cm. Height reduction due to MC treatment varied according to plant height (r=0.57 for n= 17) and was maximal at 105 cm. Mepiquat chloride reduced main stem nodes by 1.0, gin turnout by 0.4%, and lint proportion by 0.3%; increased percent of final yield harvestable on 19 September by 5%, fiber strength by 3 kN m kg−1, micronaire by 0.06 units, and petiole NO3‐N at first open boll by 0.5 g kg−1; and had no effect on fiber length, fiber elongation, petiole PO4‐P and K, or NO3‐N at first bloom. Typical seasonal heat units and control plant heights in the San Joaquin Valley fall within the range where a favorable yield response to MC is not predicted.
Hybrid and Irrigation Effects on Conservation Tillage Corn in the Coastal Plain1
Authors: Karlen D. L. , Sojka R. E.
Published: July 2010

Conservation tillage (CT) can reduce soil erosion loss, but to be voluntarily implemented, corn (Zea maysL.) yield must not be reduced when compared with conventional tillage practices such as disking periodically (DP). We compared CT and DP treatments with and without irrigation on Norfolk (fine‐loamy, siliceous, thermic Typic Paleudults) sandy loam for 4 yr to determine if hybrid selection, water management, or soil temperature caused CT corn yields to be lower than where DP was used for seedbed preparation. Plant emergence and early season growth were consistently more rapid and uniform with DP than with CT. Water was conserved in CT treatments, but this increased grain yield only under nonirrigated conditions in 1981. Average daily soil temperature for 14 days after planting was 19 °C for both tillage systems and 22 or 24 °C for CT and DP treatments for days 15 to 28. When averaged for 28 days after planting, soil temperatures in CT treatments were 0.5 °C less at 0800 h and 1.1 °C less at 1500 h. Those soil temperature differences do not appear to be sufficient to cause slower, nonuniform emergence, growth, and generally lower corn grain yield when CT practices are used in this region, although maximum yield potential for corn appears to be physiologically initiated very early during the growing season. Therefore, a successful conservation tillage system must promote rapid, uniform germination, and emergence of all plants.