bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield of Cool‐Season Soybean Lines Differing in Pubescence Color and Density
Authors: Morrison Malcolm J. , Voldeng Harvey D. , Guillemette Ron J. D. , Cober Elroy R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] pubescence color may affect yield in cool‐season soybean growing areas. The objective of this research was to examine the interaction of tawny (T) and gray (G) pubescence color with dense (D) and normal (N) pubescence density on seed yield. Lines differing in pubescence color and density were created from crosses with eight soybean cultivars adapted to Maturity Group 00 and 0 conditions. Within each cross, quadruplets were selected that had the four pubescence types: TD, TN, GD, and GN. These lines were evaluated for yield across 4 yr at Ottawa, Canada. Lines with gray pubescence had from 7.6 to 27.7% higher yields than those with tawny pubescence in years receiving >2664 crop heat units (CHU) during the growing season. In a year receiving <2664 CHU, soybean lines with tawny pubescence had 9.3% higher seed yields than those with gray pubescence. The interaction between pubescence color and seasonal temperature was similar among lines of diverse genetic background. Tawny lines with dense pubescence had from 3.1 to 10.6% higher yields than tawny lines with normal pubescence when the seasonal precipitation was <360 mm. In gray lines, changing pubescence density did not consistently affect seed yields. Soybean pubescence color did affect seed yield and should be considered when breeding for cool‐season regions.
Defoliation Tolerance of Bluebunch and Snake River Wheatgrasses
Authors: Jones Thomas A. , Nielson Dale C.
Published: July 2010

Bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Löve] has long been noted for poor tolerance to grazing during culm elongation in the spring. Bluebunch wheatgrass is an autoploid series of diploids (2x) and tetraploids (4x). In the mid‐1980s, a group of populations were found to be allotetraploid and are now commonly referred to as Snake River wheatgrass. Relative grazing tolerance of 2x and 4x bluebunch wheatgrass and of Snake River wheatgrass is unknown. This study evaluated the effect of multiple defoliation on these grasses to simulate one consequence of grazing, removal of photosynthetic tissue. Fifteen entries representing the three taxa were established at North Logan, UT, on a Millville silt loam (coarse‐silty, carbonatic, mesic Typic Rendolls; 2–4% slope) during 1988. Seedlings were vegetatively propagated into two clones apiece and transplanted adjacent to one another; one clone was subjected to multiple defoliation and the other served as an undefoliated control. Multiple defoliation at 10 cm was applied from late spring to midsummer from 1990 to 1992 at 4‐wk intervals and dry matter yield was measured in late fall 1991, early spring 1992, late fall 1992, and late spring 1993. We used the defoliated‐to‐control ratio of plant response to estimate defoliation tolerance. The defoliated‐to‐control ratio for dry matter yield of Snake River wheatgrass (0.17 and 0.38 in late fall 1991 and early spring 1992, respectively) was greater than for 4x (0.06 and 0.18) or 2x (0.06 and 0.19) bluebunch wheatgrasses after the first year of multiple defoliation. The defoliated‐to‐control ratio for dry matter yield did not differ among taxa in late fall 1992, but the ratios for Snake River wheatgrass (0.20) and 4x bluebunch wheatgrass (0.21) were both greater than for 2x bluebunch wheatgrass (0.13) in late spring 1993. Less variation was seen among Snake River than bluebunch wheatgrass entries. Because Snake River wheatgrass had both higher yield and greater defoliation tolerance than bluebunch wheatgrass, Snake River wheatgrass is more likely to survive defoliation over the long term.
Kill Date of Vetch, Rye, and a Vetch–Rye Mixture: I. Cover Crop and Corn Nitrogen
Authors: Clark Andrew J. , Decker Alvin M. , Meisinger John J. , McIntosh Marla S.
Published: July 2010

Spring kill date affects cover crop N content and N availability to subsequent no‐till corn (Zea mays L.). This 2‐yr study was conducted in 1990 and 1991 at Coastal Plain and Piedmont locations in Maryland to evaluate three cover crop kill dates, three corn planting dates, and four corn fertilizer N (FN) rates following hairy vetch (Vicia villosa Roth), cereal rye (Secale cereale L.) and a vetch‐rye mixture. No‐cover checks were included for each corn planting date. Fertilizer N rates were 0 to 202 kg ha−1 in the Piedmont and 0 to 270 kg ha−1 for the Coastal Plain. The vetch‐rye mixture contained as much or more N than vetch, and more N than rye within each kill date. Cover crop biomass and N content increased for each delay in kill. In a 50‐d period from late March until early May, vetch and the vetch‐rye mixture accumulated about 2 kg N ha−1 d−1, with total topgrowth N accumulation from 144 to 203 kg ha−1 over two locations and two years. Greatest rye N accumulation was 51 kg ha−1. Corn N content ranged from 37 to 293 kg ha−1, and was significantly affected by FN rate. Within FN rate, N content was greater following vetch or vetch‐rye than following rye or no cover, particularly at low FN rates. Corn N content was greater if cover kill and corn planting were delayed until late April or mid‐May. This was attributed to greater cover crop N production and mulching effects, and the timing of summer rainfall. Corn FN requirements were greatest following rye or no cover, intermediate following vetch‐rye, and least following vetch. This demonstrates that cover crop species and kill date can be managed to conserve N with rye, supply N for the next crop with vetch, or provide both N conservation and N supply with a vetch‐rye mixture.
Early‐Maturing Soybean Cropping System: III. Protein and Oil Contents and Oil Composition
Authors: Kane Mark V. , Steele Colleen C. , Grabau Larry J. , MacKown Charles T. , Hildebrand David F.
Published: July 2010

Expanding production of early‐maturing soybean [Glycine max (L.) Merrill] cultivars in the southeastern USA has exposed such cultivars to a wide range of environmental conditions during seedfill. Temperatures during this growth stage influence levels of specific fatty acids, particularly of the unsaturated fatty acids. Our objective was to evaluate the grain quality responses of early‐maturing cultivars to the wide range of planting dates in the southeastern USA. Protein and oil contents, along with fatty acid profiles, were assessed for cultivars from Maturity Group (MG) 00 through IV using late April, mid‐May, early June, and late June planting dates on a well‐drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993. Across years and cultivars, delayed planting increased protein content and linolenic acid levels and reduced oil content and oleic acid levels, but had little or no influence on palmitic, stearic, or linoleic acid levels. The higher seed‐fill temperatures associated with early planting were strongly correlated with increased oil content and oleic acid levels and reduced linolenic acid levels. Increasing seed‐fill temperatures were closely associated with reduced linolenic acid levels for all six cultivars. However, the oleic acid response to seed‐fill temperatures strongly depended on cultivar maturity. Oleic acid levels of early‐maturing cultivars were much more sensitive to seed‐fill temperatures than were those of later maturing cultivars. While overall effects of environment on grain quality characteristics may be relatively small, perhaps the quality of new low linolenic acid cultivars could be amplified through culture under the warmer conditions of the southeastern USA.
Managing Yield and Water Use of Pearl Millet in the Sahel
Authors: Payne William A.
Published: July 2010

Drought occurs often in the West African Sahel, but studies have shown that soil water availability is not usually the limiting factor to pearl millet [Pennisetum glaucum (L.) R. Br.] production, and that field water‐use efficiency (WUE)—i.e., the ratio of yield to evapotranspiration (ET)—is almost always very low. The purpose of this study was to determine management effects on yield and water use of pearl millet for a range of climate conditions in the Sahel. Grain and aboveground dry matter yield, daily vapor pressure deficit, and soil water data were taken during four years of contrasting rainfall. Within any given year, genotype, plant population, and fertilizer had relatively small to no effect on ET, but large effects on yield. When high plant population (≥20 000 hill ha−1) was combined with high fertilizer application (≥40 kg N ha−1 and ≥18 kg P ha−1) during the wettest year, total ET was increased by ≈50 mm. High fertilizer application tended to slightly increase ET and thereby deplete soil water reserves, but this was not associated with yield decline. Yield and water‐use data refute the view that, by maintaining fields at low fertility and low plant populations, farmers reduce risk of crop failure during drought by reducing crop water use. Compared with traditional practices that use plant populations as low as 5000 hill ha−1 and zero fertilizer input, moderate plant population (10 000 hill ha−1) and fertilizer application (20 kg N ha−1 and 9 kg P ha−1) substantially increased yield and approximately tripled WUE even during 1984, the driest year on record. In general, grain yield was better predicted from ET within different management categories when corrections were made for mean daily vapor pressure deficit during the growing season (VPD). The study provides evidence for the need to moderately increase pearl millet plant population and fertilizer application in the Sahel to efficiently use available water without risk of crop failure through depletion of soil water reserves. It also provides a practical, albeit empirical, basis for predicting yield under different management systems from seasonal ET and VPD data.
Growth and Water Status in Meadow Fescue is Affected by Neotyphodium and Phialophora Species Endophytes
Authors: Malinowski D. , Leuchtmann A. , Schmidt D. , Nösberger J.
Published: July 2010

Growth and water status in meadow fescue (Festuca elatior L.; syn. F. pratensis Huds.) is affected by Neotyphodium and Phialophora endophytes. Meadow rescue is often infected with Neotyphodium uncinatum (Gams, Petrini & Schmidt) Glenn, Bacon, Price & Hanlin or cosymbiotically with this and a Phialophora‐like endophyte. In a growth chamber experiment, we determined the influence of these endophytes on selected growth attributes and plant water status of one genotype of meadow fescue. Single plants of clone M1 free of endophytes (E‐) or infected with N. uncinatum (N), Phialophora like endophyte (P), or both endophytes (NP) were adequately irrigated (control plants) or subjected to a gradually established soil water deficit for 26 d (stressed plants). Afterwards, stressed plants were rewatered and allowed to regrow for 4 wk. Cumulative herbage dry matter (DM) yield was greater in P plants by 7.5% compared with N plants, generally. Control P plants produced more root DM thanE ‐ andN Pp lants. RootD Min N plants wass ignificantly greater during recovery from drought, compared with P and NP plants (36%). Tiller number of NP plants was the lowest among endophyte treatments in the predrought period. In response to waters tress, P plants produce more tillers than E ‐ plants (24%), but average tiller weight of P plants was lower than in E‐ plants (14%). During imposed waters tress, stomatal conductanc(ge) and leaf water potential (ΨL) decreasedin all plant‐endophyate associations to a similar extent. At severe soil water deficit, however N plants had significantly lower (g3) and ΨL than the other plant‐endophyte associations. Control plants benefited from the symbiosis with endophytes by increasing root growth( both endophytes) and shoot growth( Phialophora‐like endophyte). Plants infected with N. uncinatum were potentially able to adjust to soil water depletion earlier, suggesting a greater potential for adaptation to drough.
Variation in Eastern Gamagrass Forage Yield with Environments, Harvests, and Nitrogen Rates
Authors: Brejda John J. , Brown James R. , Lorenz Todd E. , Henry Jimmy , Lowry Stephen R.
Published: July 2010

Environmental variation, and the interaction of environment with management practices, can significantly affect perennial forage yields. The objective of this research was to evaluate the importance of environmental main effects and the interaction between environments, N rates, and harvests on eastern gamagrass [Tripsacum dactyloides (L.) L.] forage yields. Established eastern gamagrass stands were fertilized with 0, 168, or 336 kg N ha−1, and harvested three times during the growing season for three consecutive years at two locations in northern Missouri. Year and the year × location interaction were significant environmental sources of variation affecting forage yields. The year main effect had the larger variance component and accounted for 9% of the total variation in forage yields. The harvest main effect and year × harvest interaction had the largest variance components, and together accounted for more than 67% of the total variation in forage yields. Most of the variation between harvests resulted from differences in first‐harvest yields, taken at the reproductive growth stage, compared with regrowth harvest yields which were at vegetative growth stages. Variation in precipitation amounts between harvests significantly influenced regrowth harvest yields, causing a significant year × harvest interaction. Forage yield responses to N rates also varied between years, causing a significant year × N rate interaction. Location was not an important source of variation in eastern gamagrass forage yield in this study, nor was there a significant interaction between N rates and harvests. Resultsuggest that supplemental irrigation and longer rest periods between harvests may help improve forage yields and distribution.
Nutritive Value of Clipped ‘Mott’ Elephantgrass Herbage
Authors: Chaparro Cesar J. , Sollenberger Lynn E.
Published: July 2010

Many tropical grasses are low in nutritive value, but ‘Mott’ dwarf elephantgrass (Pennisetum purpureum Schumacher) has supported gains of yearling cattle (Bos taurus) approaching 1 kg d−1. To aid in identifying optimum harvest management practices for Mott, this study quantified crude protein (CP) and in vitro digestible organic matter (IVDOM) concentrations of leaf blade, leaf sheath, stem, and total herbage harvested following imposition of a wide range of clipping treatments. Treatments in 1989 and 1990 included all 16 combinations of four defoliation frequencies (3, 6, 9, and 12 wk) and four stubble heights (10, 22, 34, and 46 cm) in a randomized block design with three replicates. The soil was a hyperthermic, uncoated Aquic Quartzipsamment (Adamsville series). Data were analyzed by fitting multiple regression equations starting with a second‐order polynomial model. The range in IVDOM of total herbage harvested was from 653 to 791 g kg−1 (1989) and 680 to 739 g kg−1 (1990). Frequent defoliation to short stubble resulted in greatest IVDOM; herbage harvested infrequently to short stubble was least digestible. Total herbage CP ranged from 87 to 140 g kg−1 in 1989 and 89 to 133 g kg−1 in 1990, and was greatest with frequent harvest to a tall stubble. Mott elephantgrass CP and IVDOM were high across a wide range of defoliation frequencies and stubble heights. Because of Mott's high nutritive value even when defoliated infrequently (e.g., 9 wk), achieving yield and persistence goals can be the primary basis for selecting defoliation management practices.
Effect of Annual Medic Smother Plants on Weed Control and Yield in Corn
Authors: De Haan Robert L. , Sheaffer Craig C. , Barnes Donald K.
Published: July 2010

Using spring‐seeded smother plants for weed control could reduce the environmental impact of corn (Zea mays L.) production. Research was conducted to determine whether currently available medic (Medicago spp.) cultivars are adapted for use as smother plants in corn. In field experiments in 1992 at Becker and Rosemount, MN, Medicago scutellata (L.) Mill. cv. Sava and Kelson were interseeded with corn at 0, 85, 260, or 775 seeds m−2. In 1993, Sava and Kelson, along with M. polymorpha L. cv. Santiago and M. lupulina L. cv. George, were interseeded with corn at 260 seeds m−2 and N fertilizer was applied at 0, 84 (56 at Rosemount), or 168 kg−1. Land equivalent ratios for corn and medic intercrops grown in 1992 were not > 1, indicating that corn and medics competed strongly for resources. Medics seeded with corn at a rate high enough to consistently suppress weeds (260 seeds m−2) reduced weed dry weight 14 wk after corn emergence by 69% at Becker and by 41% at Rosemount compared with monoculture corn. The same seeding rate reduced corn grain yield in weed‐free plots by 21% at Becker and 15% at Rosemount compared with monoculture yields. In 1993, medic smother plants reduced weed dry weight more when grown in the 0 kg ha−1 N plots than in the 168 kg ha−1 N plots. Corn yield losses, however, were less severe in the 168 kg ha−1 N treatments than with 0 N. Annual medics managed as smother plants in corn effectively reduced weed biomass; however, additional research is needed to identify medic genotypes and smother plant management systems that reduce corn yields less than those we evaluated, and that provide more consistent weed suppression across environments..
Wheat Coleoptile and Root Growth and Seedling Survival after Dehydration and Rehydration
Authors: Guedira M. , Shroyer J. P. , Kirkham M. B. , Paulsen G. M.
Published: July 2010

Wheat (Triticum aestivum L.) seed frequently is planted deeply in dry soil that supports germination but not emergence. Our objective was to ascertain the effect of dehydration on seedling survival and development, particularly the coleoptile and root, and their ability to resume growth after rehydration. Seeds of ‘Larned’, a tall, hard red winter wheat with a long coleoptile, were germinated for 1, 2, 3, 4, or 5 d and seedlings were dehydrated for 1, 2, 3, 4, or 5 d and then rehydrated. Seedling survival was greater than 75% after 1 to 3 d germination and all dehydration treatments, but declined from about 60% to zero after germination for 4 d and dehydration for 3 d or more. Dehydration reduced coleoptile lengths by 17 to 58% compared with the control. Seminal roots also were highly sensitive to dehydration, except at early stages, but were replaced quickly at all stages when seedlings were rehydrated. Changes in seed weight suggest that reserves were important for recovery of seedlings from dehydration. Increasing depth of planting and duration of germination successively reduced emergence of seedlings from seeds that were germinated for 1 to 4 d and then dehydrated for 2 d. The results demonstrated that emergence of wheat seedlings is increasingly impaired by dehydration as germination progresses, that the seedling stage when dehydration occurs is more important than the duration of the stress, and that coleoptile and root growth and seed reserves are involved in seedling responses to dehydration.
Near‐Infrared Analysis of Cotton Leaves as a Guide for Nitrogen Fertilization
Authors: Saranga Yehoshua , Landa Ari , Shekel Yehuda , Bosak Arie , Kafkafi Uzi
Published: July 2010

Nitrate level in cotton (Gossypium hirsutum L.) leaf petioles is commonly used as a practical guide to N fertilization, especially in cases of critically low N levels. The optimization of N supply to irrigated cotton requires a reliable method for monitoring the plant's N status. The feasibility of using leaf N concentrations monitored by near‐infrared analysis (NIRA) as a guide for N fertilization in irrigated cotton was examined in this study. Three field trials were conducted in three consecutive years. The NIRA data from fresh leaf disks were calibrated against laboratory N measurements expressed as g N kg1−1 dry matter (R2 = 0.90). Validation of the calibration showed a high correlation between NIRA estimates and laboratory data from two field trials. Dawn leaf sampling was selected for routine monitoring of plant N status. Application of NIRA‐guided N fertilization was examined in the third‐year trial. The NIRA‐guided treatment, with only 60 kg N ha−1, resulted in only a 7.5% lower yield (statistically nonsignificant) relative to the commercial predetermined N treatment with 150 kg N ha−1. Yield was linearly correlated with leaf N concentration. Cotton leaf N concentration was reliably monitored by NIRA. Only 30 s are required for each N determination; using 10 samples, about 7 min are needed per plot. Once its reliability under various conditions is established, this method could be used for on‐the‐spot decision‐making regarding N‐fertilizer application in irrigated cotton.
Nondestructive Estimation of Shoot Nitrogen in Different Rice Genotypes
Authors: Ladha Jagdish K. , Tirol‐Padre Agnes , Punzalan Gloria C. , Castillo E. , Singh Upendra , Reddy C. Kesava
Published: July 2010

Plant N uptake and grain yield are important components of N use efficiency. Grain yield is easily measured, but plant N analysis is time consuming and requires hazardous chemicals or expensive equipment. A nondestructive method involving the least equipment and skill, to determine N uptake, is needed in agronomic and plant breeding experiments. A nondestructive method to determine shoot (aboveground biomass) N of transplanted rice (Oryza sativa L.) was developed based on SPAD‐502 chlorophyll meter readings, leaf area, and tiller number. In two dry‐season and one wet‐season field experiment, shoot N of various genotypes at flowering were highly correlated (P < 0.05) with CLAT, the product of SPAD reading from a selected leaf (C), area of that leaf (LA), and number of tillers (T) (r2 = 0.46, 0.90, and 0.85 in Exp. 1, 2, and 3, respectively); and with LAT, the product of LA and T (r2 = 0.56, 0.88, and 0.76). Shoot N may be estimated using LAT for larger differences in leaf area compared with SPAD readings. Lower correlations in Exp. 1 were due to the lower range in shoot N contents. The highest correlation between shoot N and CLAT was observed in the third uppermost leaf. Regressions of shoot N on LAT and CLAT varied across growth stages and seasons. Thus, LAT or CLAT can be used to evaluate N uptake among N fertilizer treatments and different rice genotypes at a given stage within a season. Further work is needed to assess the reliability of this method under different seasons and cultural practices.
Influence of Soil Texture on Alfalfa Autotoxicity
Authors: Jennings John A. , Nelson C. Jerry
Published: July 2010

A rotation interval is recommended between alfalfa (Medicago sativa L.) stands to avoid negative effects of autotoxicity. Differences in soil properties such as texture can strongly influence allelopathic expression in plants and may explain the large variation in research results and recommended rotation intervals among states. A laboratory experiment was conducted to determine the influence of soil texture on alfalfa autotoxicity. Alfalfa extracts were passed though leaching columns filled with topsoil of either Sarpy fine sandy loam (mixed, mesic Typic Udipsamments) or Carlow silty clay loam (fine, smectitic, mesic Vertic Endoaquolls) and fractions were collected. Control columns for each soil were leached with distilled water only. Sequential fractions were added to 50 alfalfa seed in petri dishes. Radicle length and percentage germination were measured after 3 d. Active fractions reduced radicle growth more than percentage germination in both soils. The autotoxic chemical or chemicals moved through the Sarpy soil faster than through the Carlow soil. Fifty percent more water was required to move the active fraction of the extract through 10‐cm columns of the Carlow soil than the Sarpy soil. Maximum autotoxicity within a fraction was greater for the Sarpy soil, but the effects appeared in more fractions for the Carlow soil. The results indicate that similar amounts of the autotoxic factor in sandy soil will have a greater influence on alfalfa seedling growth than in the clay soil. Conversely, the same amount of rainfall will leach the autotoxic factor from a sandy soil while only diluting it in a clay soil. Soil texture and rain water throughput may interact to affect length of rotation intervals needed for successful reseeding of alfalfa. Field research is needed to determine if rotation intervals can be modified based on soil texture and irrigation or expected rainfall.
Yield and Yield Components of Corn Interseeded with Cover Crops
Authors: Abdin Omar , Coulman Bruce E. , Cloutier Daniel , Faris Mohamed A. , Zhou Xiaomin , Smith Donald L.
Published: July 2010

The rising costs of pesticides, soil erosion, and environmental pollution associated with corn (Zea mays L.) production have led to consideration of alternative production methods. Growing cover crops with corn could address these problems. Field experiments were conducted in 1993 and 1994 at l'Assomption and Macdonald in Quebec to determine the effects of interseeding 12 cover crops on corn yield and yield components. Fall rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), a mixture of red clover (Trifolium pratense L.) and ryegrass (Lolium multiflorum Lam.), a mixture of white clover (T. repens L.) and ryegrass, subterranean clover (T. subterraneum L.), yellow sweetclover (Melilotus officinalis Lam.), black medic (Medicago lupulina L.), Persian clover (T. resupinatum L.), strawberry clover (T. fragiferum L.), crimson clover (T. incarnatum L.), alfalfa (Med. sativa L.), and berseem clover (T. alexandrinum L.) were seeded 10 and 20 d after corn emergence. The experimental design was a splitplot, randomized complete block with four replications at each site. The mainplots were the cover crop planting dates; the subplots were the 12 cover crop treatments and 3 controls (hand weeding, chemical weeding, and no weeding). Seeding the cover crops either 10 or 20 d after corn planting did not affect corn grain yield. Chlorophyll fluorescence measurements (Fv/Fm) indicated that corn plants were stressed when interseeded with crimson clover (P < 0.05). When there was competition for moisture, crimson clover was found to be too competitive with corn at the seeding rates used in this experiment. Corn yield was less affected by the interseeded cover crops under conditions of adequate rainfall. No consistent differences in corn grain yield components were found for cover crop treatments.
Phenological Temperature Response of Maize
Authors: Stewart Douglas W. , Dwyer Lianne M. , Carrigan Lori L.
Published: July 2010

Variability of development rate estimates across locations and years using the current heat unit system of growing degree‐days (GDD) with maximum and minimum temperature thresholds of 30 and 10°C (GDD30,10) limits predictability of maturity in hybrid maize (Zea mays L.). Data sets of daily maximum and minimum air temperatures and dates of maize development stages were collected for a range of hybrids at locations in Canada and the northern USA (39° to 45° N lat). Data were analyzed to improve the temperature response functions for maize at different stages of development. Results indicate that during vegetative growth, phenological response to mean daily air temperature followed a sigmoidal curve beginning below 5°C, with maximum response to temperatures between 25 and 30°C. During reproductive growth, the temperature response function was flat from 0 to 12°C and rose significantly only with mean daily air temperatures greater than this range. A general thermal index (GTI) based on these two response functions improved estimation of maturity dates by 50% over estimates made using GDD30,10 (SE of 6.7 d for GTI and 13.6 d for GDD30,10 in estimating time from planting to maturity). The greatest improvement using GTI occurred for the reproductive period (SE of 5.8 d using GTI, compared with 12.1 d using GDD30,10). These results suggest that incorporating the temperature response function reported in this paper would improve prediction of maize development.
Contribution of Rice Tillers to Dry Matter Accumulation and Yield
Authors: Wu Guowei , Wilson Lloyd T. , McClung Anna M.
Published: July 2010

A rice (Oryza sativa L.) crop functions as a population of tillers produced at different times and possessing specific growth characteristics. The objective of this study was to characterize the contribution of cultivar tillering ability to dry matter accumulation, yield components, and grain yield. Field experiments were conducted over a 2‐yr period using a completely randomized plot design at Beaumont, TX, grown under a pin‐point flood system, with a China clay soil (fine, smectitic, hyperthermic Oxyaquic Dystrudert). Three cultivars were chosen (Gulfmont, Rosemont, and Teqing), to represent moderate to high tillering abilities, and three plant densities were chosen (56, 112, and 169 plants m−2), to produce differential competition for light and nutrients. Teqing had the highest tillering ability and partitioned more mass to tillers, especially at the lowest plant density, with 77% of the total mass represented by tillers, compared with 71 and 69% for Gulfmont and Rosemont, respectively. However, total dry mass per unit area at harvest was not significantly different, contrasting the plant density treatments (1618, 1725, and 1744 g m−2 for the 56, 112, and 169 plants m−2 treatments, respectively, when averaged across cultivars). Both cultivar and plant density significantly affected a number of yield components, but not kernel weight. The higher yield of Teqing (918 g m−2), contrasted with the lower‐yielding Gulfmont (791 g m−2) and Rosemont (729 g m−2), appears largely to have resulted from its greater tillering ability, higher spikelet density, and longer maturation period, which makes greater use of the relatively long growing season length at Beaumont.
Soybean Leaf Morphology and Defoliation Tolerance
Authors: Haile Fikru J. , Higley Leon G. , Specht James E. , Spomer Stephen M.
Published: July 2010

Plant tolerance to pest injury is an ideal component of integrated pest management (IPM) programs, because it places no selection pressure on pest populations, but tolerance is little understood and its use in pest management is limited. In field experiments in 1994, 1995, and 1996, we characterized tolerance to defoliation in ‘Clark’ soybean [Glycine max (L.) Merr.] isolines differing in leaf morphology: 3‐ and 5‐leaflet, narrow and wide leaflet. Sequential defoliation was imposed manually at the R2 stage (full flowering), based on an insect consumption model. In 1994 and 1996, with ample rainfall, all isolines expressed yield compensation or overcompensation for defoliation as high as 75%, due to compensatory regrowth and delayed leaf senescence; in 1995, however, when rainfall was marginal, defoliation caused significant yield reduction. Equal amounts of leaf tissue removed resulted in different leaf area indices (LAIs). Wide‐leaflet isolines had higher LAI than narrow‐leaflet isolines, but the narrow‐leaflet isolines, particularly Clark‐3N, had greater light interception capacity for a given LAI level and had a higher light extinction coefficient in 1995. This shows that light was available to leaves in the lower canopy in the narrow‐leaflet isoline. Both low and high defoliation treatments caused significant yield reductions in all isolines, except that low defoliation did not significantly affect the yield of Clark‐3N in 1995. The narrow‐leaflet isolines apparently tolerated defoliation better than the wide‐leaflet isolines because the narrow‐leaflet isolines had greater light interception and maintained equal or better yields, despite similar defoliation. In addition to LAI, both canopy light interception and light extinction coefficient are important criteria for selecting cultivars tolerant to defoliation.
Water Distribution in a Fragipan Soil during the Growing Season
Authors: Rhoton Fred E. , Römkens Mathias J. M.
Published: July 2010

The resistance to penetration developed during the formation of fragipan horizons effectively excludes plant roots from the water stored in this zone. Thus, plant roots are believed to be restricted to the use of water stored in the profile between the fragipan and soil surface. This study was conducted to determine if fragipan horizons contribute water to plant rooting zones during the growing season. Twelve experimental field plots were installed at each of three sites situated on Grenada silt loam (fine‐silty, mixed, active, thermic Glossic Fragiudalfs). Based on relative depths to the fragipan horizon, these three sites represented slight, moderate, and severely eroded phases of the soil. Access tubes were inserted to a depth of 30.5 cm below the fragipan surface on six of the plots at each site. Water contents were measured weekly by a combination of gravimetric and neutron probe methods from the 1984 through the 1987 growing seasons. Results indicate that the fragipan horizons contributed water to the overlying profile each growing season at all three sites. The extent of water loss from the fragipan was determined by its proximity to the soil surface. For the four growing seasons, the fragipan horizon contributed on average 15.6% of the water lost at the severely eroded site, compared with 5.5 and 6.1% at the slightly and moderately eroded sites, respectively. These results suggest that plants grown on soils with fragipan horizons have indirect access to water stored in that zone. Consequently, yield data from such studies must be carefully interpreted when comparing sites with a range of depths to fragipan.
Estimating Cotton Canopy Ground Cover from Remotely Sensed Scene Reflectance
Authors: Maas Stephan J.
Published: July 2010

Many agricultural applications require spatially distributed information on growth‐related crop characteristics that could be supplied through aircraft or satellite remote sensing. A study was conducted to develop and test a methodology for estimating plant canopy ground cover for cotton (Gossypium hirsutum L.) from scene reflectance. Previous studies indicated that a relatively simple relationship between ground cover and scene reflectance could be developed based on linear mixture modeling. Theoretical analysis indicated that the effects of shadows in the scene could be compensated for by averaging the results obtained using scene reflectance in the red and near‐infrared wavelengths. The methodology was tested using field data collected over several years from cotton test plots in Texas and California. Results of the study appear to verify the utility of this approach. Since the methodology relies on information that can be obtained solely through remote sensing, it would be particularly useful in applications where other field information, such as plant size, row spacing, and row orientation, is unavailable.
Potato Yield, Petiole Nitrogen, and Soil Nitrogen Response to Water and Nitrogen
Authors: Meyer Roland D. , Marcum Daniel B.
Published: July 2010

Detection of high NO3 concentrations in domestic wells has led to concern about excessive fertilizer N use in crop production. A potato (Solanum tuberosum L. cv. Russet Burbank) experiment was initiated to examine the effect of water and N on potato yield and quality, tuber N concentrations, petiole NO3 concentrations, and N distribution in the soil. The field trial consisted of a line‐source irrigation system with six water rates (0.33, 0.66, 1.00, 1.10, 1.20, and 1.30 times crop evapotranspiration ETc) each having six planting‐time N rates (0, 56, 112, 168, 224, and 448 kg ha−1) replicated four times with treatments applied to the same plots in two successive years on a Pittville sandy loam (fine‐loamy, mixed, mesic Typic Argixerolls). Yields were significantly increased with water, averaging 14.1 to 54.4 Mg ha−1 in 1992 and 20.8 to 46.5 in 1993. Nitrogen rate significantly increased yield in 1993, averaging 28.7 to 44.1 Mg ha−1, but not in 1992. Residual soil profile NO3‐N (1040 mg kg−1) present at planting time in the first cropping season was utilized, denitrified, or leached from the top 150 cm of soil by above‐normal winter rainfall before the beginning of the second season. At the end of the second season, low NO3−N concentrations were observed in soil profiles receiving 0, 112, and 224 kg N ha−1, whereas a concentration of 1050 mg kg−1 was found in the 0‐ to 60‐cm depth of soil with the 448 kg N ha−1 rate. High residual soil N in 1992 resulted in N use efficiency (NUE) for tubers of >200 g kg−1; in the 1993 season, however, NUE was > 300 g kg−1. Nearmaximum yields were obtained with 1.10 to ETc applied water and 0 to 56 kg N ha−1 in 1992 and with 1.10 to 1.30 ETc applied water and 168 to 224 kg N ha−1 in 1993.
Integrated Root System Age in Relation to Plant Nutrient Uptake Activity
Authors: Gao Shiyu , Pan William L. , Koenig Richard T.
Published: July 2010

The age of a root segment is inversely related to its nutrient uptake activity (uptake rate per unit root length). It is uncertain how this information should be incorporated into nutrient uptake models, due to our inability to characterize the age of a whole root system. A method of calculating an integrated root system age (IRSA) was defined, and two solution experiments were conducted to relate the N uptake activity of spring wheat (Triticum aestivum L.) to root age. Literature data also were analyzed to characterize the relationship between IRSA and nutrient uptake activity of whole plant root systems. Integrated root system age was defined as the summation of the mean ages of root segments produced during each growth period weighted by the ratio of the root length generated during each growth period to total root length. The NH4 and NO3 uptake activity of spring wheat decreased with plant age as IRSA increased, while plants with similar IRSA at 14 and 21 d had similar N uptake activity. These relationships between IRSA and the uptake activity of N, P, K, Ca, and Mg of corn (Zea mays L.) were also revealed from an analysis of published data. In young root systems, nutrient uptake activity declined rapidly as IRSA increased, while older root systems (IRSA >10 to 15 d) maintained a relatively low and gradually declining nutrient uptake activity with increasing IRSA. The IRSA is a useful parameter for characterizing nutrient uptake activity of an entire root system, providing a potential tool for modeling nutrient uptake.
SAS Code for Recovering Intereffect Information in Experiments with Incomplete Block and Lattice Rectangle Designs
Authors: Federer Walter T. , Wolfinger Russell D.
Published: July 2010

Efficient use of resources and time requires optimal planning of designed experiments and optimal recovery of information from them. Selection of an appropriate experiment design and selection of an appropriate statistical analysis are mandatory for efficient experimentation. It is known that using a random effects model is more efficient than using a fixed effects one, as in the analysis of variance, meaning that fewer experimental units (plots) will be necessary to obtain the same precision. The question of transformation of data prior to analysis, of using standard textbook analyses, or of using a form of spatial analysis arises with each experiment. To obtain these analyses, it is desirable that computer programs (code) be available to the experimenter. Computer programming to recover the information from random effects is not well or widely understood. In light of recent developments of software for performing the needed calculations, a description of SAS programs is presented. Code is described for recovering interblock, interrow, intercolumn, intergradient, and interregression information in incomplete block and lattice rectangle (row‐column arrangement within each complete block) designed experiments. These are illustrated with a numerical example.
Starter Nitrogen and Growth Habit Effects on Late‐Planted Soybean
Authors: Starling Michael E. , Wood C. Wesley , Weaver David B.
Published: July 2010

In the Gulf Coast region of the southeastern USA, soybean [Glycine max (L.) Merr.] is often planted in a double‐cropped system following corn (Zea mays L.). In this system, soybean planting date is delayed from the optimal range (mid‐May to mid‐June) to late July, causing a substantial yield reduction. Potential grain yield response has led to increased interest in indeterminate growth habit and N application for late‐planted, double‐cropped soybean systems. Our objective was to determine the interactiv effects of growth habit (determinate and indeterminate stem termination types) and starter N (0 and 50 kg ha−1) on soybean growth and yield when planted following corn in a double‐crop system. Three Maturity Group VIII soybean genotypes [the near‐isolines Au86‐2397I (Dt1Dt1, indeterminate) and Au86‐2397D (dt1dt1, determinate) and a determinate check cultivar, Cook] were planted in late July in seven Alabama environments during 1995 and 1996. Starter N increased R1 dry matter for both Au86‐2397D and Au86‐2397I by 0.50 Mg ha−1. Au86‐2397I had 1 cm greater average plant height at the R1 developmental stage and 14 cm greater height at R8 than Au86‐2397D. Au86‐2397I yielded 0.16 Mg ha−1 more than its determinate near‐isoline. Application of starter N decreased the number of nodules per root, but increased plant N concentration and dry matter yield. Grain yield was increased on average by 0.15 Mg ha−1 with addition of starter N. In this study, an indeterminate genotype soybean coupled with application of starter N promoted greater soybean growth and yield in a late‐planted, double‐cropped system.
Phytotoxicity of Banded Urea Amended with Triple Superphosphate and Potassium Chloride
Authors: Ouyang Duosheng , MacKenzie Angus F. , Fan Mingxian
Published: July 2010

Banded urea can result in toxicity to corn (Zea mays L.) germination and growth, due to accumulation of NH3 and NO‐2s as a result of urea hydrolysis. Delaying urea hydrolysis through addition of acidic materials may reduce urea toxicity. Laboratory and field experiments were conducted to study phytotoxicity of banded urea amended with triple superphosphate (TSP) or KCI. A Ste. Rosalie clay (fine, mixed, frigid Typic Humaquept), an Ormstown silty clay loam (fine‐silty, mixed, frigid Typic Humaquept), and a Chicot sandy clay loam (fineloamy, mixed, frigid Typic Hapludalf) were used in the laboratory to investigate corn germination and growth across distances of 2.0 and 4.0 cm from the fertilizer band with four rates of TSP (0, 0.11, 0.22, and 0.33 g P kg−1), two rates of KCI (0 and 0.42 g K kg−1), 0.50 g urea‐N kg−1 and an unfertilized control. Field experiments were conducted on a Ste. Rosalie clay and an Ormstown silty clay loam with two rates of urea (60 and 120 kg N ha−1) and three rates of TSP (0, 26, and 52 kg P ha−1), either compacted or blended. In the laboratory experiment, NO‐2‐N, and pH decreased with TSP and KCI, due to delayed urea hydrolysis. Soil electrical conductivity (EC) increased with KCI, but was not affected by TSP. Corn growth decreased with increased soil NH3 concentration and EC. In the field, corn germination decreased with banded urea and increased with banded TSP at Day 10 after planting, but no difference was found at Day 20. Compacted mixtures of urea‐TSP increased corn germination, growth, N uptake, and yield compared with blended mixtures for the same rate of P. Compaction of urea and TSP may provide an effective way to improve efficiency of banded urea for corn production.
Acidic Soil Amendment with a Magnesium‐Containing Fluidized Bed Combustion By‐Product
Authors: Stehouwer Richard C. , Dick Warren A. , Sutton Paul
Published: July 2010

Removal of SO2 from the emissions of coal‐fired boilers produces by‐products that often consist of CaSO4, residual alkalinity, and coalash. These by‐products could be beneficial to acidic soils because of their alkalinity and the ability of gypsum (CaSO4·2H2O) to reduce AI toxicity in acidic subsoils. A 3‐yr field experiment was conducted to determine the liming efficacy of a fluidized bed combustion boiler by‐product (FBC) that contained 129 g Mg kg−1 as CaMg(CO3)2 and MgO and its effects on surface and subsurface soil chemistry. The FBC was mixed in the surface 10 cm of two acidic soils (Wooster silt loam, an Oxyaquic Fragiudalf, and Coshocton silt loam, an Aquultic Hapludalf) at rates of 0, 0.5, 1, and 2 times each soil's lime requirement (LR). Soils were sampled in 10‐cm increments to depths ranging from 20 to 110 cm, and corn (Zea mays L.) and alfalfa (Medicago sativa L.) were grown. Application of Mg‐FBC increased alfalfa yields in all six site‐years, whereas it had no effect on corn grain yield in five site‐years and decreased grain yield in one site‐year. Plant tissue concentrations of Mg, S, and Mo were increased by Mg‐FBC, while most trace elements were either unaffected or decreased. Application of Mg‐FBC at one or two times LR increased surface soil pH to near 7 within 1 wk. Although surface soil pH remained near 7 for 2 yr, there was minimal effect on subjacent soil pH. Application of Mg‐FBC increased surface soil concentrations of Ca, Mg, and S, which promoted downward movement of Mg and SO4. This had different effects on subsoil chemistry in the two soils: in the high‐Ca‐status Wooster subsoil, exchangeable Ca was decreased and exchangeable Al was increased, whereas in the high‐Al‐status Coshocton subsoil, exchangeable Al was decreased and exchangeable Mg was increased. The Mg‐FBC was an effective liming material and, because of the presence of both Mg and SO4, may be more effective than gypsum in ameliorating subsoil Al phytotoxicity.
Methods of Simulating Freezing Damage during Sorghum Grain Fill
Authors: Staggenborg Scott A. , Vanderlip Richard L. , Roggenkamp Gregory J. , Kofoid Kenneth D.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] grain yields can be reduced if plants are exposed to freezing temperatures prior to reaching physiological maturity. Two field experiments were conducted to evaluate chemical desiccation and panicle removal as methods for simulating the loss of carbohydrate production associated with leaf death or transport tissue damage when sorghum is exposed to freezing temperatures during grain fill. In one experiment, both treatments were repeated at 3‐ to 4‐d intervals during grain fill with a range of hybrid maturities and environments to establish a relationship between caryopsis weight or test weight with heat unit accumulation after anthesis. This relationship was best described as sigmoidal in shape. A second field experiment compared these two treatments with potted field‐grown plants exposed to −2°C for 4 h. Treatments were applied four different times during grain fill. Panicle removal produced caryopsis weights 5% greater than those from freeze treatments, whereas chemical desiccation resulted in caryopsis weights 13% greater than those from freeze treatments. Test weights followed similar trends. Caryopsis weights from each treatment were similar across experiments. Panicle removal accurately simulated caryopsis weight reductions caused by exposure to freezing temperatures throughout the grain‐filling period. Chemical desiccation underestimated freeze damage during early grain fill but adequately simulated caryopsis reductions during late grain fill. Test weights from panicle removal treatments were similar in both experiments, while chemical desiccation was inconsistent across experiments. Test weight reductions caused by exposure to freezing temperatures were not adequately simulated by either treatment. The results of these experiments indicate that panicle removal is a more appropriate method for simulating freeze damage to maturing grain sorghum than is chemical desiccation; however, chemical desiccation may be utilized if appropriate adjustments are made during early grain fill.