bluuebunny/crossref_metadata_2025 huggingface dataset:
Tillage Effects on Some Soil Physical and Corn Physiological Characteristics
Authors: Cox W. J. , Zobel R. W. , van Es H. M. , Otis D. J.
Published: July 2010

Tillage systems influence soil temperature and available soil water, which can influence photosynthetic rates and growth of corn (Zea mays L.). Field experiments were conducted in 1987 and 1988 in New York on a tile‐drained silt loam soil (fine‐loamy, mixed, nonacid, mesic Aeric Haplaquept) to determine to what extent conventional tillage (CT), no‐till (NT), and ridge tillage (RT) systems influence soil temperature and soil water conditions, thereby influencing CO2 exchange rates (CER) and growth of corn. Soil temperature at the 0.1‐m depth under NT averaged about 1 °C lower than CT and RT during the first 50 d after emergence (DAE). In 1987, when water stress was not a factor, the lower soil temperature under NT resulted in lower leaf, stem, and total phytomass throughout the vegetative period. Kernel growth rates, however, did not differ between tillage treatments (33.2, 30.9, and 31.4 g m−2 d−1 for CT, NT, and RT, respectively) which resulted in no differences in kernel phytomass at physiological maturity (1125, 1000, and 1030 g m−2 under CT, NT, and RT, respectively). During the hot and dry 1988 growing season, soil water pressure under CT at the 0.25‐m‐soil depth decreased to −0.1 MPa at 44 DAE, 13 d earlier than under NT anti RT. Cone index values were higher under NT and RT from the 0.07‐ to 0.22‐m‐soil depth which indicates increased soil mechanical resistance under NT and RT. The CER were significantly lower under NT or RT compared to CT on 8 of 10 measurement dates during a dry period in 1988 (34‐54 DAE) which was reflected in lower leaf, stem, and total phytomass during the vegetative period. Likewise, NT had a lower kernel growth rate (19.6 compared to 27.4 and 23.4 g m−2 d−1 under CT and RT, respectively), which resulted in lower kernel phytomass at physiological maturity. The data suggest that increased soil mechanical resistance can develop under a continuous NT and RT system which can decrease soil water uptake, CER and growth of corn when dry conditions occur during vegetative development.
Spectral Estimates of Daily Carbon Dioxide Exchange Rates in Wheat Canopies
Authors: Wall G. W. , Lapitan R. L. , Asrar G. , Kanemasu E. T.
Published: July 2010

Spectral indices have been used to predict leaf area index (LAI) and the interception efficiency (e1) of photosynthetically active radiation (PAR) within a plant canopy. The objectives of this work were to investigate the influence of canopy geometry on the temporal trends in LAI and spectral indices, and to develop equations to predict the daily canopy gross carbon dioxide exchange rates (DGCE) from daily PAR. Winter wheat (Triticum aestivum L. cv. Newton) was planted in north‐south and east‐west row orientations with 0.18‐, 0.35‐, 0.53‐, and 0.71‐m row spacings, during 1982—1983 and 1983—1984. Net CO2 exchange rates were measured with a transparent dynamic positive‐pressure chamber and a differential infrared gas analysis system. Daytime dark respiration rate correction were made to obtain the DGCE. Canopy spectral reflectance was monitored with a multispectral radiometer, while absorption of PAR was measured with quantum sensors. Daily absorbed PAR was derived by taking the product of e1, estimated from either the LAI or spectral indices, and total incoming PAR. Row orientation did not significantly influence the temporal trends in LAI or the spectral response, whereas significantly greater LAI and spectral response occurred in the narrower‐ vs. wider‐spaced canopies. A linear model characterized the relationship between DGCE and daily absorption of PAR. A common slope model (0.74 g CO2 mol−1 photon) indicated that the LAI and spectral indices had similar predictive capabilities. Good agreement occurred between an equation developed with 1984 data and measured values from 1983 (i.e., R2 0.49—0.65). Remotely sensed multispectral canopy reflectance data, therefore, can be used to estimate DGCE in wheat canopies.
Crop Water Stress Index and Forage Quality Relationships in Alfalfa
Authors: Halim R. A. , Buxton D. R. , Hattendorf M. J. , Carlson R. E.
Published: July 2010

Recent developments in assessment of plant‐water stress employ infrared thermometers to measure the difference between air and canopy foliage temperature (Tc – Ta). Crop Water Stress Index (CWSI), which normalizes Tc – Ta values for climatic variability, is related to forage yields of alfalfa (Medicago sativa L.). The objective of this study was to determine whether forage quality of alfalfa also is related to CWSI. ‘Apollo II’ alfalfa was grown in 100‐L potometers set into the ground and protected by a movable rainout shelter. Plants were watered either weekly or twice weekly to 112, 100, 88,76, and 64% of field capacity during 2 yr. Daily readings of canopy and air temperature were taken, and vapor‐pressure deficits were determined from the time plants were 15 cm tall until harvest. Plants were harvested after 5 wk of regrowth and were divided into stem bases (lower six nodes and internodes), stem tops, and leaves before forage quality analyses were conducted. Dry‐matter yield and plant maturity declined linearly with increasing CWSI (r2 = 0.86 and 0.65, respectively). Leaf‐to‐stem ratio increased with increasing CWSI (r2 = 0.51), but year effects, in addition to waterstress effects, were evident. In vitro digestible dry matter (IVDDM) in stem bases increased with CWSI (r2 = 0.78), but leaf IVDDM was not significantly related to CWSI. Crude protein (CP) concentration in stem bases increased with CWSI (r2 = 0.86), whereas leaf CP concentration declined quadratically with increasing CWSI (r2 = 0.51). Total‐herbage CP concentration was not significantly related to CWSI. Neutral‐detergent fiber concentration in stem bases, leaves, and total herbage declined with increasing CWSI (r2 = 0.89, 0.75, and 0.69, respectively). Thus, models based solely on plant quality‐CWSI relationships may not be adequate for predictive purposes because, often, year effects were not removed or coefficients of determination were low.
Daylength and Temperature Effects on Emergence and Early Growth of Sericea Lespedeza
Authors: Mosjidis J. A.
Published: July 2010

Poor emergence and seedling growth of sericea lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don.] may be related to the climatic conditions under which it is established in the southern USA. A growth chamber study was undertaken to measure the effect of temperature on seedling emergence and the influence of temperature and daylength on early growth of several sericea lespedeza genotypes. Emergence was reduced by about 20% with each reduction of 3 °C in day /night temperature within the range of temperatures used. Height, shoot dry weight, leaf dry weight, and stem dry weight of all genotypes tested were very sensitive to both daylength and temperature. Increases in temperature and day length above the lowest temperature combination (18/14 °C) and the shortest daylength (11 h) brought about large increases in height, shoot dry weight, leaf dry weight, and stem dry weight of all genotypes. Screening sericea genotypes for seedling growth should be done at 26/22 °C or 30/26 °C (day/night) and 13 or 15 h of daylength. Further screening of sericea germplasm for emergence and growth underlow temperature and for day‐neutral genotypes may lead to cultivars with more vigorous seedlings under short day conditions.
Long‐Term Field Research on Water and Environmental Quality
Authors: Menzel R. G.
Published: July 2010

Maintaining the quality of soil, water, and air presently has a high national priority, and is particularly important for agriculture. The deterioration of environmental quality, in most respects, has proceeded almost imperceptibly. Long‐term research is required to study effects that change slowly with time, such as contamination of groundwater, or that depend upon infrequent weather events, such as water erosion of soil. Much environmental quality research involves long‐term measurements of runoff and soil erosion because these are the dominant mechanisms for transporting nutrients and pesticides to rivers and lakes. Water and environmental quality studies are being made at sites ranging from small field plots to large watersheds and experimental lakes. Effects of acid rain are being studied mainly at watershed and lake sites. There has been little long‐term groundwater quality research on agricultural areas, but a major investigation of nitrate and pesticide movement is getting under way. Long‐term field research is essential to confirm and refine the predictions derived from environmental models.
Evaluating Nitrogen Fertilizer Rate and Timing for Meadowfoam Seed and Dry Matter Production
Authors: Jolliff Gary D. , Seddigh Majid
Published: July 2010

Previous reports on N fertilization effects on meadowfoam (Limnanthes alba Hartw. ex Benth.) seed yield are inconsistent. This study was conducted to determine whether N fertilizer application rate and timing could be manipulated to increase seed yield in ‘Mermaid.’ Field experiments were conducted during the 1982–1983 and 1984–1985 seasons on a Woodburn silt loam (fine‐silty, mixed, mesic Aquultic Argixeroll) to evaluate the influence of twelve combinations of N rate and timing on Mermaid dry matter production and seed yield. Treatments included 50, 100, and 200 kg N ha−1 applied in fall, winter, spring, and split fall/spring timings. Except for the 50 and 100 kg N ha−1 applied in the fall of 1984, seed yields for all N treatments were greater than the control. Application rate and timing interactions on dry matter production, seed yield, and harvest index were not significant in either growing season. Averaged over rates, fall application resulted in significantly lower seed yield and total dry matter than the other timing treatments, presumably because of N loss through leaching. The effects of application rates above 50 kg N ha−1 on dry matter production and seed yield varied between years. The data suggest that 50 kg N ha−1 applied in late winter or early spring increases meadowfoam seed yield. Under climatic conditions such as during the 1984–1985 season when lodging was low, higher rates of N might be beneficial. However, application of more than 50 kg N ha−1 in spring could reduce seed yield if the climatic conditions are conducive to lodging.
Influence of Ethephon on Lowest Pod Height and Yield of Soybean
Authors: Grabau L. J. , Pearce R. C. , Konsler J. V.
Published: July 2010

Ethephon [2‐(chloroethyl) phosphonic acid] has improved lodging resistance of several crops, mainly by reducing plant height. Our objective was to determine if ethephon could reduce plant height of soybean [Glycine max (L.) Merr.] without reducing lowest pod height (LPH), which would increase the potential for stubble harvest losses. Maturity group IV soybean cultivars Ripley (short) and Southern States 443 (tall) were planted in both full season and late‐planted cropping systems in 1987 and 1988 on a Maury silt loam (fine, mixed, mesic Typic Paleudalfs) near Lexington, KY. Ethephon was applied at 280 g a.i. ha−1 at growth stages V4, V6, or V4 and V6. All three ethephon treatments reduced plant height to a similar degree. No ethephon effect on lodging was detected, since lodging pressure was minimal. Ethephon did not reduce LPH, and thus had no effect on stubble harvest losses. In addition, ethephon did not influence grain yield. Ethephon successfully reduced plant height without increasing stubble harvest losses. No conclusion on the effect of ethephon on lodging resistance of soybean can be drawn from this research.
Nitrogen Use by Northern‐Adapted Barley Genotypes Under No‐Till
Authors: Tillman B. A. , Pan W. L. , Ullrich S. E.
Published: July 2010

No‐till planting can restrict the growth and productivity of spring grains in the U.S. Pacific Northwest. Cooler soil temperatures, compared to conventional tillage, may contribute to lower productivity. Therefore, genotypes bred in cold climates may better adapt to notill management. Eleven spring barley (Hordeum vulgare L.) genotypes were evaluated for N content and dry matter accumulation under direct drilling at 45 and 90 kg N ha−1. These genotypes originated in the Pacific Northwest (PNW) or the Northern European (Nordic) countries Denmark, Finland, and Sweden. The Nordic genotypes were developed under cooler, wetter soil conditions than the PNW genotypes, and were therefore predicted to be better adapted to no‐till management. Barley was drilled into stubble of spring cereals in a Palouse silt loam (fine‐silty, mixed mesic Pachic Ultic Haploxeroll). The Finnish genotypes, HJA Potra, HJA 80201, and HJA 78003, generally had greater above‐ground dry matter and N content than the domestic genotypes prior to anthesis. These differences were not sustained through rain filling, however, and PNW genotypes accumulated more N and dry matter per unit area by maturity. Steptoe was the only genotype that consistently absorbed N during grain filling, while many genotypes exhibited net N losses. Nitrogen remobilization and N harvest index tended to be greater in 6‐row genotypes compared to 2‐row genotypes. The PNW genotypes generally outyielded the Nordic genotypes with the exception of ‘Nordal’. Nevertheless, if the physiological traits of the Nurdic genotypes associated with efficient N uptake during cold soil conditions could be incorporated into an existing PNW genotype, improved N use efficiency may be obtainable.
Response of Internal Tissue Water Balance of Peanut to Soil Water
Authors: Erickson P. I. , Ketring D. L. , Stone J. F.
Published: July 2010

Efficient water application for crop productivity requires knowledge of the plant/soil water balance. The objectives of this research were to determine how peanut (Arachis hypogaea L.) leaf water content responds to soil water content and to examine the soil water content‐ΨS relationship for predicting limiting levels of soil water relative to crop water status in the field. Few field data describing peanut internal water balance responses to soil water are available. In the present study, available soil water content is defined as water content minus water content at −1.5 MPa divided by water content at −0.01 MPa minus water content at −1.5 MPa. This approach. normalizes water content to the fraction available. It is analogous to leaf relative water content (LRWC) and is expressed as soil relative water content (SRWC). The objectives of this research were to: (i) define the relationship between SRWC and LRWC of peanut grown under rainfed and irrigated conditions, and (ii) use SRWC to predict limiting levels of soil water relative to crop water status. Plants were grown on a Teller loam soil (fine, mixed, thermic Udic Argiustoll). Weekly midday (1130 to 1300 apparent solar time) measurements of LRWC were made between 40 and 100 d after planting (DAP). Weekly SRWC values were interpolated to correspond to LRWC measurement days. Above 50% SRWC, the mean LRWC was about 85%, and appeared to be affected more by evaporative demand than by SRWC. Below 50% SRWC, LRWC was highly correlated with SRWC. The predicted SRWC when turgor pressure potentials approached zero was about 45%. This SRWC threshold occurred under rainfed conditions in the 3 yr studied at 59, 56, and 64 DAP during flowering and pod formation. It is concluded that the SRWC vs. soil water pressure potential curve of Teller soil may be useful for predicting limiting levels of soil water for peanut and that limiting levels of soil water may occur well above the classically defined lower limit of soil water availability.
Measuring Water Infiltration Rates of Sports Turf Areas
Authors: Taylor D. H. , Williams C. F. , Nelson S. D.
Published: July 2010

Measuring the rate of decline of ponded water in rings is commonly used to determine water infiltration rates on turfgrass sites. Recently rings smaller than 30 cm in diameter have been marketed and used. This research examined the utility of 15‐ and 20‐cm diam. rings used as single or as double rings as well as 30‐ and 50‐cm diam. double rings for measuring water infiltration rate into golf greens and athletic fields. Results indicated that infiltration rates measured by any ring, including the 30‐ and 50‐cm diam. double ring, varied widely on a single golf green or athletic field. Infiltration rates measured with smaller rings used either as single or as double rings did not always correspond well with infiltration rates measured by the larger double rings. Infiltration rates measured with ponded water in single or double rings on sports turf areas should be viewed only as rough estimates and results should be used with caution.
Agronomic Performance of Winter versus Spring Wheat
Authors: Entz M. H. , Fowler D. B.
Published: July 2010

Recent advances in crop management have enabled the production of winter wheat (Triticum uestivum L.) in most of the Canadian prairies. The agronomic performance of dominant hard red winter and highq‐uality hard red spring wheat cultivars was compared in semiarid and dry subhumid regions of Saskatchewan. In 15 trials, winter wheat (WW) outyielded spring wheat (SW) by an average 36%, and in three trials, ‘Norstar’ WW yielded 26% higher than the high‐yielding semidwarf SW, ‘HY 320.’ Protein yield was higher for WW in two of 15 trials and protein concentration was always higher for SW. Higher grain yield of WW was attributed mainly to the production of a higher kernel number per square meter (KNO). Crop development rate, aerial dry matter production, evapotranspiration (ET), and water use efficiency (WUE), were measured for Norstar WW and ‘Katepwa’ SW in six trials grown between 1986 and 1988. The period between Zadoks growth stage (ZGS) 21 and 65 was 4 to 14 d longer for Norstar than for Katepwa. Average daily air temperature between ZGS 21 and 65 was 2.6°C higher for Katepwa, and daily air temperature during this period was negatively correlated with KNO in both cultivars. Early season dry matter production was highest for Norstar. These early season cultivar differences gradually disappeared and, with the exception of two trials, total dry matter was similar by crop maturity. Harvest index was significantly higher for Norstar in five of six trials. Seasonal ET patterns were similar for Norstar and Katepwa, except in three of six trials where ET in early May was significantly higher for the WW cultivar. The WUE for dry matter production, grain yield and grain protein yield was consistently higher for Norstar.
Nodulation, Dinitrogen Fixation, and Yield Improvement in Second‐Crop Soybean Cover‐Inoculated with Bradyrhizobium japonicum
Authors: Ciafardini G. , Lombardo G. M.
Published: July 2010

When soybean [Glycine max (L.) Merr.) is grown in soil containing few Bradyrhizobium japonicum (Kirch.) Jordon, the limited mobility of the symbiont results in the formation of a small number of nodules distributed mainly on the primary root of the plant near the inoculation point. The authors conducted a 3‐yr study aimed at increasing nodulation and N2 fixation in ‘Hodgson’ soybean as a second crop, by cover inoculating B. japonicum on the soil with irrigation water at the time of sowing or at the three‐node (V3) stage. Inoculation treatments were: (i) seed inoculation; (ii) cover inoculation at sowing; (iii) seed inoculation plus cover inoculation at sowing; (iv) cover inoculation at the V3 stage; (v) seed inoculation plus cover inoculation at the V3 stage; (vi) uninoculated control. The seed plus cover inoculation at sowing or the V3 stage produced, on the whole, the greatest nodulation, 1.4 to 2.4 times that for seed inoculation alone. The addition of cover inoculation at sowing increased seed yield by 50 g m−2 in 1985 and 90 g m−2 in 1986, regardless of whether the cover inoculation was performed at sowing or the V3 stage. In 1988, a year in which the soybean was sown about 1 mo later than in the previous years and subjected to higher temperatures, seed and cover inoculation increased N2 fixation and plant‐N concentration, but not yield.
Small‐Plot Windrower
Authors: Ehrensing D. T. , Crane J. M. , Bolton F. E.
Published: July 2010

Although many crops are commonly field dried in windrows, research has often been limited by the lack of adequate equipment for small‐plot windrowing. A research scale windrowing machine was constructed that closely imitates commercial practice. The machine was used on a number of crops in 1989.
Radiation Use Efficiency among Cotton Cultivars
Authors: Rosenthal W. D. , Gerik T. J.
Published: July 2010

Cotton (Gossypium hirsutum L.) cultivars have diverse growth rates and fruiting characteristics that may be due to differences in radiation use efficiency. Potential growth rates were measured to see if differences could be attributed to radiation use efficiency or canopy light transmission coefficients. An irrigated field study was conducted at the Blackland Research Center using three diverse cotton cultivars; Acala SJ‐2, Deltapine 5O, and Tamcot CD3H. Plant densities ranged from 10 to 14 plants m−2. Transmitted, incoming, and reflected photosynthetically active radiation and leaf area index were measured weekly from 3 wk after emergence to boll opening. Dry matter accumulation and leaf area index were significantly different among cultivars both years. Light transmission coefficients were not different, but cultivars differed in radiation use efficiency through the reproductive period. Values for radiation use efficiency ranged from 1.5 g MJ−1 photosynthetically active radiation for Acala to 1.3 g MJ−1 for Tamcot. Values were not significantly different during the vegetative period. These differences during the reproductive period are likely due to differences in boll number and photosynthetic efficiency among cultivars. Tamcot had 50 to 100% more bolls than Acala both years. These results suggest that crop models should account for these cultivar differences in radiation use efficiency.
Root Hair Occurrence anld Variation with Environment
Authors: Meisner C. A. , Karnok K. J.
Published: July 2010

Early literature on peanut [Arachis hypogcrea (L.)] indicates the existence of two forms of root hairs: (i) a rosette form of root hair (4 mm long) occurring; radially where a lateral root initiates from a primary root, and (ii) shorter (0.30 mm), more profuse root hairs occurring along root lengths usually behind the root tip. Since little is known about the factors that influence peanut root hair formation, the purpose of this study was to quantify root hair formation under various soils and water stress conditions. Separate rhizotron, field, and greenhouse studies were conducted. The rhizotron study showed no differences in the percentage of roots having root hairs regardless of water stress treatments imposed 20 to 50 and 50 to 80 days after planting (DAP). Thirty‐seven to 43% of the roots had root hairs. In the field, peanut root systems growing within dialysis root bags in a Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Kandiudults) showed a significant increase in root hair formation from 7% at 70 DAP to 31% at harvest. In the greenhouse using three soil types, Greenville fine sandy loam (clayey, kaolinitic, thermic Rhodic Kandiudults), Tifton loamy sand, and a 4:1 coarse sand:fritted clay mixture (rhizotron), soil type was found to affect the percentage of roots having root hairs. Roots growing in the Tifton, sand:fritted clay mixture, and Greenville soils had 47, 17, and 14% root hairs, respectively. In all studies, the rosette form of root hair around lateral initiates was observed. Approximately 66% of the lateral initiates expressed rosette‐type root hairs. Mycorrhizal infection, though insufficient to significantly affect nutrient uptake, was greater with the rhizotron (18%) than the Greenville (6%) and Tifton soils (3%). There may be a possible interaction between root hair occurrence and mycorrhizae infection.
Field‐Grown Tomato Response to Carbonated Water Application
Authors: Novero R. , Smith D. H. , Moore F. D. , Shanahan J. F. , d'Andria R.
Published: July 2010

Direct release of CO2 gas to achieve a cost‐effective method of atmospheric CO2 enrichment has not been proven feasible under field conditions. We hypothesized that greater efficiency of application would occur by applying CO2 via carbonated water and that application would also result in beneficial modifications of the soil environment. Our objectives were to evaluate crop, soil, and atmospheric CO2 responses to application of carbonated water under pressure through a drip irrigation system. Studies were conducted under mulched and unmulched conditions in 1988 using tomato (Lycopersicon esculentum Mill.). In 1989, carbonated water was applied at approximately 2‐, 4‐, and 6‐d intervals to determine the effect of irrigation frequency. In 1988, a positive yield response of 9% was obtained in the presence of mulch. No response was observed in open beds. Fruit yields were increased at all three irrigation frequencies in 1989, with increases in fresh‐market and total fruit yields averaging 16.4 and 15.9%, respectively. Atmospheric enrichment was observed during carbonated water application, but residual enrichment between irrigations was difficult to detect. Significant increase in soil‐air CO2 from carbonated water application was noted throughout the intervals between successive irrigation events. Carbonated water application also decreased soil pH for periods of up to 5 d after irrigation and increased apparent uptake of P, K, Ca, Mg, Zn, Fe, Mn, Cu, and B. Based on the limited duration of enrichment relative to the entire growing season for any of the carbonated water treatments, the yield responses observed could not be attributed solely to atmospheric enrichment. Thus, we conclude that yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and soil environment modifications leading to improved nutrient uptake.
No‐Till Winter Wheat Dry Matter and Tissue Nitrogen Response to Nitrogen Fertilizer Form and Placement
Authors: Johnston A. M. , Fowler D. B.
Published: July 2010

Expansion of winter wheat (Triticum aestivum L.) production into the high winterkill risk regions of the Canadian prairies has been achieved by no‐till seeding into standing stubble immediately after harvest of the previous crop. Seven field trials were conducted in Saskatchewan to evaluate the seasonal pattern of dry matter and N accumulation of no‐till winter wheat. The fertilizer treatments included the currently recommended early (20 April) spring broadcast ammonium nitrate (AN) and early spring broadcast and surface band applied urea and urea‐ammonium nitrate (UAN) solution. In four of the seven trials, late (12 May) AN and urea were also applied. Nitrogen fertilizer was applied at 0, 34, 67, 101, and 202 kg N ha−1. Mean maximum dry matter and N yields were established by Zadoks Growth Stage 65 (ZGS65) and ZGS45, respectively. Subsequent losses of both dry matter and N were observed under conditions of high evaporative demand and low precipitation. When rainfall was more favorable and N supply abundant, N and dry matter yields increased through the growing season to harvest. Increased N rates increased N uptake and amplified plant‐N and dry matter losses. Growing season environmental conditions and plant‐available‐N levels also played an important role in determining the efficiency of N translocation to the seed. Early broadcast AN produced larger dry matter and N‐yield responses than all other fertilizer treatments. While surface band applied urea showed no advantage over early broadcast urea, surface band applied UAN increased dry matter yield and N uptake over broadcast sprayed UAN. Average dry matter (N) yield‐N response for early broadcast urea, surface band applied urea and surface band applied UAN treatments were 93 (89%) of those recorded for early broadcast AN. The broadcast sprayed UAN treatment dry matter and N yield‐N responses were 81% of early broadcast AN. Compared with early broadcast AN and urea, late broadcast AN and urea produced lower dry matter yields and delayed N uptake. Average late broadcast AN and urea dry matter (N) yield‐N responses were 63 (85%) of those recorded for early broadcast AN and urea. These observations indicate that differences in dry matter and N‐yield responses for different N forms and placement methods are established early in the growing season and maintained through to maturity.
Use of a Chlorophyll Meter to Predict Sidedress Nitrogen Requirements for Maize
Authors: Piekkielek W. P. , Fox R. H..
Published: July 2010

Most N testing methods require collecting, processing and analyzing of either soil or plant tissue samples. In 1987 we began a study to determine if chlorophyll readings of maize (Zea mays L.) made in the field with a portable chlorophyll meter could be used to predict soil N availabilities and sidedress fertilizer N requirements. The meter was tested over a 3‐yr period on 67 N response experiments located in central and southern Pennsylvania. At the six‐leaf stage of maize the chlorophyll meter reading of the fifth leaf was an accurate predictor of whether maize would respond to sidedress N fertilizer. A chlorophyll meter reading of 43.4 meter units was found to be the best critical level to separate responsive and nonresponsive sites. The chlorophyll meter method was similar in its accuracy in separating N responsive sites from nonresponsive sites to several proposed soil N availability tests including the soil NO3 concentration in the surface 20 cm of soil at planting, the UV absorbance at 200 nm of a 0.01 M NaHCO3 extract of the surface 20 cm of soil at planting, and the soil NO3 concentration in the surface 30 cm of soil 4 to 5 wk after plant emergence. The chlorophyll meter test was not well enough correlated with soil N supplying capability (r = 0.59) to determine sidedress N fertilizer rates for N responsive sites.
Small‐Grain Equivalent of Mixed Vegetation for Wind Erosion Control and Prediction
Authors: Skidmore E.L. , Nelson R.G.
Published: July 2010

Control and prediction of wind erosion require knowledge of the effectiveness of surface vegetative cover. The effectiveness is usually referenced to as small‐grain equivalent. The procedure used to convert mixed vegetation to small‐grain equivalent was found faulty. Improper weighting of regression coefficients caused the conversion procedure to predict that adding crop residue decreased small‐grain equivalent. Therefore, the purpose of this analysis was to improve the conversion of mixed vegetation to a small‐grain equivalent. The new expression derived for this purpose gave a logical conversion where the previous procedure failed. It did not predict a decreasing small‐grain equivalent with increased soybean [Glycine max (L.) Merr.] residue in the 0 to 300 kg/ha range as did the former method. Applied to the same data that were used for testing the previous procedure, the new procedure reduced the error by almost 50%. The new procedure improves the conversion of mixed vegetation to small‐grain equivalent.
Lowland Rice Yield as Affected by Timing of Water Deficit and Nitrogen Fertilization
Authors: Castillo E. G. , Buresh R. J. , Ingram K. T.
Published: July 2010

Water deficit and insufficient N supply are important constraints to the productivity of rainfed lowland rice (Oryzu sativa L.). To determine the effects of water deficit and urea application timing on yield and N accumulation of lowland rice, a field experiment was conducted for 2 yr on an Andaqueptic Haplaquoll in the Philippines. Water regimes imposed in the dry season were continuously flooded, not flooded or irrigated from 15 to 35 d after transplanting (DT), and not flooded or irrigated from 41 to 63 DT. Urea treatments in factorial combination with the water regimes were no applied N, early N (80 kg N ha−1, one‐half basal incorporated and one‐half broadcast at 37 DT), and late N (80 kg N ha−1, one‐half broadcast at 11 DT and onehalf broadcast at 65 DT). Water deficit at 15 to 35 DT significantly reduced mean grain yield (26%), straw yield (21%), grain N accumulation (31%), and straw N accumulation (31%). Water deficit at 41 to 63 DT, which ended before panicle emergence, decreased yield and N uptake, but less than water deficit at 15 to 35 DT. Nitrogen application consistently increased grain yield even when the rice crop was exposed to water deficit. Mean grain yields were greater (P < 0.05) for early N (5.7 Mg ha−1) than late N (3.7 Mg ha−1) in 1986 but not in 1987 (4.1 and 3.8 Mg ha−1, respectively). Water‐by‐N interactions were not significant for grain or straw yields and grain or straw N accumulations. The N timing most effective for continuously irrgated rice was also most effective for rice exposed to moderate water deficit before flowering.
Impact Absorption Characteristics on Turf and Soil Surfaces
Authors: Rogers J. N. , Waddington D. V.
Published: July 2010

Playing quality of athletic fields is critical to an athlete from the safety and performance standpoints. Use intensity and maintenance practices affect playing surface quality and impact characteristics within and among fields. The objective of this study was to quantitatively assess the effects of cutting height, compaction, soil water content (date), and turf cover on the impact absorption characteristics of Kentucky bluegrass (Poa pratensis L.) turf. Treatments were four cutting heights (0 [bare soil], 19, 38, and 57 mm), and two compaction levels (with and without) for Exp. I, and three cutting heights (19, 38, and 57 mm), two compaction levels, and three surface types (full turf, no verdure, and no thatch) in Exp. II. Surface impact characteristics measured were peak deceleration, time to peak deceleration, and impact duration. Two hammer weights, 2.25 kg and 0.5 kg, were used to assess impact characteristics on four dates and to obtain data for soil water conditions of 0.263, 0.197, 0.163, and 0.064 kg kg−1. The highest peak deceleration values and shortest time periods were associated with the periods of low soil water and compacted conditions. Only the 0.5‐kg hammer detected differences in impact absorption characteristics between cutting heights. Significant cutting height‐by‐compaction‐ by‐date interactions occurred for each impact characteristic, indicating interdependence of one of the factors on another. It appears that field management practices that influence soil water content, soil compaction, and turf cover are more important than cutting height in altering the impact absorption capability of Kentucky bluegrass turf.
Seedling Emergence of Yellow‐Flowered Alfalfa as Influenced by Seed Weight and Planting Depth
Authors: Townsend C. E.
Published: July 2010

Yellow‐flowered alfalfa [Medicago sativa L. subsp. falcata (L.) Arcangeli] is well‐adapted to rangeland sites in the central and northern Great Plains, but its early seedlings vigor is poor compared to that of purple‐flowered alfalfa (M. sativa L. subsp. sativa). The objectives of this study were to (i) develop germplasms with a high percentage of falcata traits and (ii) determine the effect of seed weight and depth of planting on seedling emergence. Germplasm with 18 seed‐weight classes (1.0 to 2.1 g/l000 seeds) was developed and evaluated for seedling emergence from a 1.9‐cm depth of planting in a Nunn clay loam soil (fine, montmorillonitic, mesic Aridic Argiustolls) on two dates of planting at Fort Collins, CO, in 1986. Seed weight was significantly (P ≤ 0.01) correlated with seedling emergence at both the first (r = 0.69) and second (r = 0.79) dates of planting. The 18 classes were consolidated into six classes whose mean seed weights were 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0 g/1000 seeds. The six classes were evaluated for seedling emergence from 1.3‐, 2.5‐, and 3.8‐cm depths of planting at Fort Collins, from 1987 through 1990. The six seed‐weight classes and three depths of planting differed significantly (P ≤ 0.05 or ≤ 0.01) for seedling emergence at each of six planting dates. In general, the heavier seedweight classes had the highest seedling emergence over all depths of planting and, as expected, seedling emergence decreased with increased depth of planting. Seedling emergence of yellow‐flowered alfalfa can be increased by selecting for high seed weight.
Structured Heterogeneity of Soil pH and Grain Yield of Rice and Wheat Grown in a Sodic Soil
Authors: Samra J. S. , Rajput R. K. , Katyal V.
Published: July 2010

Conventional statistical methods that assume independent random variation are inadequate when dealing with spatially dependent heterogeneity. Structural analysis of heterogeneity was performed for soil pH and grain yields of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) grown under uniform management in a sodic soil (Natric Haplustalf). Relative efficiencies of field sampling designs and methods of analysis were computed. The coefficients of variation (CV) for the yield of rice and a subsequent wheat crop were 16 and 5490, respectively. The two‐way trend variation in soil pH was 21% of variance before rice planting and 28% after wheat harvest. The same parameter for the grain yield of rice and wheat was 12 and 28%, respectively. Variogram analysis revealed that locally structured variation of soil pH was 30 and 48% of variance before rice planting and after wheat harvest, respectively. Structured heterogeneity for grain yield was 16% in rice and 59% in wheat. Soil pH heterogeneity effects on rice were of lower magnitude than with wheat. The relative efficiency of Wilkinson's nearest neighbor analysis as compared to a randomized block design varied from 623 to 1682% depending on size and shape of the plot. This indicates that a substantial improvement in experimental precision is possible by taking account of positional effects of observation plots.
Modeling Sorghum Seedling Establishment from Soil Wetness and Temperature of Drying Seed Zones
Authors: Brar G. S. , Steiner J. L. , Unger P. W. , Prihar S. S.
Published: July 2010

Existing crop simulation models predict emergence based on experimental results on the effects of soil temperature and water in systems sealed against evaporation. Under field conditions, however, the seed zone is open to evaporation. Seed zone water decreases with time and is often inversely related to soil temperature. Little is known about the combined effects of soil temperature and water on sorghum [Sorghum bicolor (L.) Moench] emergence rates in drying seed zones. Therefore, our objective was to study this and to model the effect to predict seedling stand establishment. Greenhouse experiments were conducted to study sorghum emergence at six constant temperatures (8.8, 15.9, 20.5, 25.2, 30.2, and 35.8 °C) attained on a thermogradient plate, and three initial soil water matric potentials (Ψ3) (−0.03, −0.1, and −0.3 MPa), using a Pullman clay loam. Emergence and plant height were recorded daily for 2 wk and root length was measured at termination of the experiment. We developed a sorghum stand establishment model that utilizes heat units and indices of emergence or growth as input parameters to predict emergence and root and shoot growth of seedlings. Optimum sorghum emergence (> 80%) was obtained at temperatures of 20.5 to 30.2 °C, and −0.03 to −0.1 MPa Ψ3. Furthermore, combinations of cool temperature (15.9 °C) and (6: of −0.1 MPa as well as warm temperature (35.8 °C) and Ψ of −0.03 MPa produced satisfactory emergence (> 80%). Sorghum emergence regressed with thermal emergence index yielded a highly significant (P < 0.0001) positive nonlinear correlation (Adj. R2 = 0.62). Similarly, main axis root length, lateral root length, and plant height regressed with thermal indices of main axis root length, laterlal root length, and shoot growth yielded significant (P < 0.0001) positive, nonlinear correlations (Adj. R2 = 0.46, 0.70, and 0.77, respectively). The model should provide more realistic sorghum emergence predictions than models developed in systems closed to evaporation.
Bermudagrass Response to Reactive Layer Coated Fertilizers
Authors: Peacock Charles H. , DiPaola Joseph M.
Published: July 2010

Recent polymer chemistry research has introduced a material manufactured by a reactive layer coating (RLC) process which shows promise for minimizing N loss through leaching. Laboratory studies have shown that RLC coated ureas were successful at slowing N release and have potential as slow‐release N fertilizers for turf. This field study compared ‘Tifway’ bermudagrass (Cynodon dactylon L. Pers. ✕ C. transvaalensis Burtt‐Davey) response to RLC ureas having different coating weights (thicknesses) with other conventional N carriers. Bermudagrass turf quality (1 – 9 scale, 9 = best) and shoot growth response observations were made over a 10‐wk period to determine if various coating thicknesses would allow adequate N release to provide a response equivalent to other N sources. Best turf quality (7.4) for the 2‐yr study was for RLC carriers that combined slow and intermediate release rate RLC ureas (12.5% or 10.8% coating + 7.2% coating) with urea. Overall turf quality was lowest (6.5) in 1987 for the RLC with the slowest release rate, a 12.5% coating (10 g N m−2), 9.9% RLC coating + urea (10 g N m−2), and urea (5 g N m−2). In 1988 the RLC with the slowest release had a 10.8% coating (10 g N m−2). Shoot growth rate in 1987 was greatest (11.9 mm wk−1) for the RLC material with a 7.2% coating at 10 g N m−2 and lowest for the RLC 12.5% coating (5.3 mm wk−1). By comparison, urea applied at 5 g N m−2 resulted in intermediate turf growth (9.4 mm wk−1). In 1988, shoot growth rate was greatest for the 10.8% RLC + 7.2% RLC + urea combination material applied at 10 g N m−2. Equivalent growth was noted for the urea + 9.9% RLC (5g n m−2) and sulfur coated urea (10 g N m−2) materials. Use of slow release RLC N carriers as turf fertilizers showed promise as a combination material with urea.
Influences of Soil Environment on Biomass and Nitrogen Accumulation Rates of Orchardgrass
Authors: Stout W.L. , Jung G.A.
Published: July 2010

Grasslands are the basis for a stable agriculture in the northeast USA. However, knowledge of the interactive effects of the diverse soils and climate of this region on grassland production remains scant. Our objective was to quantify the effect of soil environment on grassland biosmass and N accumulation. The study was conducted for 3 yr on four sites in central Pennsylvania selected for soil water holding capacity and temperature regime. Orchardgrass (Dactylis glomerata L.) was treated with a split application (50%/50%) of 0, 84, and 168 kg N ha−1 of 15N depleted ammonium nitrate. Biweekly biomass samples were taken starting 30 April of each year and continuing until the grass heading stage. At heading, plots were cut at a 7.5‐cm stubble height and all herbage removed. Plots were refertilized with the second half of the N and monthly biomass sampling commenced on 31 July and continued until 31 October. Biomass samples were dried at 60 °C and weighed for yield. Subsamples of the dried material were analyzed for N and isotope ratio. Spring biomass accumulation rates ranged from 60.0 to 112.0 kg ha−1 day−1. Soil N, N fertilization and temperature all were factors controlling spring biomass accumulation rate. Fall biomass accumulation rate was controlled by N fertilization alone. Spring fertilizer N accumulation rates range from 0.078 to 0.72 kg ha−1 day−1 and were largely controlled by N fertilization. Spring total N uptake rates ranged from 0.461 to 2.20 kg ha−1 day−1 and were controlled by soil N levels and N fertilization. Fertilizer N recovery was about 42% for the spring growth period but only about 15% for the fall growth period.
Reproductive Abscission and Yield Response of Soybean to Root and Canopy Competition
Authors: Marvel J. N. , Beyrouty C. A. , Gbur E. E.
Published: July 2010

Interplant competition has been shown to influence plant architecture and seed yield. However, the influence of individual root or canopy competition on soybean [Glycine max (L.) Merr.] yield has not been identified. Field studies were conducted to determine the effects of root and canopy competition on abscission of reproductive structures and seed yield of the soybean cultivar Forrest. Plots were established on a Captina silt loam (fine‐silty mixed mesic Typic Fragiudults). Treatments were (i) no competition (ii) root competition only (iii) canopy competition only and (iv) both root and canopy (combined) competition. There was no difference among no, root, and canopy competition in the total number of reproductive structures produced and retained in 1985. However, in 1986 root and canopy competition resulted in an average of 281 and 166 reproductive structures produced and retained, respectively. In both years, combined competition caused the greatest reduction in the number of reproductive structures produced and retained. Combined competition resulted in 52 and 58% abscission in 1985 and 1986, respectively. In 1985, no, root, and canopy competition had similar effects on pod number per plant with an average of 387 pods, while combined competition resulted in only 99. In 1986, however, no competition resulted in the largest number of pods (310), combined competition resulted in the smallest number of pods (34), and root and canopy competition were intermediate with an average of 184 pods per plant. Subjecting plants to root competition decreased total seed weight and total seed number per plant by 44 and 42%, respectively, while canopy competition reduced total seed weight and number by 78%.
Growth and Development of Uniculm and Conventional‐Tillering Barley Lines
Authors: Dofing S. M. , Karlsson M. G.
Published: July 2010

Barley (Hordeum vulgare L.) producers in northern regions require genotypes that develop and mature rapidly. Although the phenological development of barley has been studied extensively, the effect of the uniculm character on rate of growth and development has not been investigated. The objective of this study was to compare the growth and development of uniculm and conventional‐tillering near‐isogenic barley lines. Three pairs of near‐isogenic lines that differed by the presence of the uc2 (uniculm) gene were evaluated at Palmer and Fairbanks, AK during the 1990 and 1991 growing seasons. Averaged over four environments, uniculm genotypes required more growing degree days (GDD) to reach double ridge formation, but there were no differences for GDD to terminal spikelet formation (P < 0.01). Uniculm genotypes had 0.3 more leaves per main culm, required 12 fewer GDD to reach full flag leaf extension, and had a leaf appearance rate that was 0.12 leaves (100 GDD)−1 faster than conventional genotypes (P < 0.01). Uniculm genotypes matured 23 GDD earlier and were 10.9 cm taller than their conventional counterparts (P < 0.01). The restriction of a single culm per plant decreased kernels per spike by 2.2 kernels and increased kernel weight by 8.4 mg (P < 0.01). Our results suggest that the uniculm phenotype results in several favorable modifications of phenological development, which may be of practical value in regions where early maturity is important.