bluuebunny/crossref_metadata_2025 huggingface dataset:
Ryegrass Cultivars and Endophyte in Tall Fescue Affect Nematodes in Grass and Succeeding Soybean
Authors: Pedersen J. F. , Rodriguez‐Kabana R. , Shelby R. A.
Published: July 2010

Annual ryegrass (Lolium multiflorum Lam.) is often double cropped with soybean [Glycine max (L.) Merr.] in much of the southeastern United States to provide winter grazing and ground cover. Little is known about the effect of annual ryegrass cultivars on nematodes associated with the grass, and with subsequent soybean crops. In several other taxonomically similar grasses, including tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.), the presence of endophytic fungi imparts pest resistance to the grass. No information is available on the effect of these endophytic fungi on nematodes associated with the grass. Therefore, the objectives of this study were to determine: (i) the effect of annual ryegrass cultivars on nematodes in the grass and in succeeding soybean, and (ii) the effect of Acremonium coenophialum Morgan‐Jones and Gams in tall fescue on nematodes. Thirteen annual ryegrass cultivars, ‘Kentucky 31” tall fescue with and without A. coenophialum infection, and a nematode‐susceptible soybean check were grown for 7 wk in pots in the greenhouse in a Malibis sandy loam (fine‐loamy, siliceous, thermic Plinthic Palendults) soil known to be infested with high numbers of phytonematodes. Plants were then removed from the soil, and the soybean was seeded into the pots and grown for 7 wk. Significant differences among nematode populations in the annual ryegrass cultivars occurred, and the nematode numbers were generally higher in the soybean that followed. However, these increased numbers did not affect soybean performance. Therefore, it does not appear that the use of annual ryegrass‐soybean doublecropping systems will be effective in controlling most nematodes when using nematode‐susceptible soybean cultivars. In tall fescue, lower spiral [Helicotylenchus dihystera (cobb) Sher.] and stubby root [Paratrichodorus minor (culbran) Siddiqi) nematode numbers were associated with A. coenophialum in the grass. Since nematode damage has previously been associated with stand decline in tall fescue, breeders working in nematode‐infested areas should be aware that decreased pest resistance may be associated with the removal of A. coenophialum from tall fescue.
Use of Growing Degree Days to Project Sample Dates for Cereal Crops
Authors: Klepper Betty , Rickman R. W. , Zuzel J. F. , Waldman S. E.
Published: July 2010

Timely field sampling of a developing crop requires careful organization of laboratory space, equipment, and personnel to maximize efficiency. This paper demonstrates how historical temperature data sets, planting dates, and plot site elevation and location can be used to project expected developmental stage for winter wheat (Triticum aestivum L.) plants at any site in the Pacific Northwest dryland wheat‐growing areas. Historical average temperature data from long‐term weather station records for over 50 sites in the Oregon‐Washington‐Idaho dryland cereal production areas are stored on a computer. A program selects the weather station site nearest to the plot site on the basis of latitude, longitude, and altitude. Average daily maximum and minimum temperatures from the weather station are used to generate daily growing degree days for the plot site. Growing degree days are used to predict crop development. Projections can be made of either the expected date for a particular developmental stage or the expected degree days for any given date. Projections are used to schedule sample dates.
Breakage Susceptibility of Corn Kernels in Relation to Crop Management under Long Growing Season Conditions
Authors: Vyn T. J. , Moes J.
Published: July 2010

Corn (Zea mays L.) kernels are subject to breakage during postharvest handling. Manipulation of crop management factors has influenced kernel breakage susceptibility, but the effects of hybrid, plant density, harvest moisture content, and drying temperature on breakage susceptibility have not been studied under long growing season conditions. Field experiments were conducted in 1985 and 1986 at Ridgetown, Ontario. Five commercial hybrids were grown at different plant densities (5.5 and 7.0 plants m−2 in both years, and 6.3 plants m−2 in 1985), harvested at 300 and 240 g kg−1 moisture content (wet basis), and dried at different air temperatures (20, 40, and 80°C in 1985; 20 and 100°C in 1986) to approximately 150 g kg−1 moisture content. A Wisconsin breakage tester was used to measure breakage susceptibility. Small increases in breakage were consistently associated with increased plant densities. Reductions in breakage were sometimes associated with lower grain moisture content at harvest. The largest and most consistent changes in breakage susceptibility were due to changes in drying temperatures. Increased drying temperatures resulted in increased breakage, but there was variation among the hybrids in the size of the response. The results indicate that breakage susceptibility is an inherited trait that is also influenced by crop management. Kernel breakage can be reduced by proper choice of hybrids, drying at low air temperature, and harvesting at low grain moisture content. In both years, increased breakage susceptibility was related to higher levels of endosperm stress cracks, tendency towards roundness in shape, and increased levels of harvest damage in the form of visible chips or cracks.
Ontogeny and Yield Response of Common and Tepary Beans to Temperature
Authors: Scully B. , Waines J. G.
Published: July 2010

Temperature affects crop development and yield. In this study the effect of temperature on emergence, vegetative development, and yield of common bean (Phaseolus vulgaris L.) and tepary bean (P. acutifolius A. Gray) was compared. In the growth chamber nine common bean accessions were evaluated for emergence response over planting depths of 25, 50 and 75 mm, and at constant temperatures of 15,20,25,30, and 35 °C. The three depths had no significant effect on emergence between 20 and 30 °C, but at 15 and 35°C the increased depth significantly delayed emergence. The most rapid germination and emergence occurred at 30 °C under these controlled conditions. In the field emergence of the same common bean accessions was compared to tepary bean; tepary bean emerged about 1.5 d earlier than common bean at soil temperatures of 18 to 28 °C. The effect of temperature on vegetative development was evaluated by a linear heat unit system that measured base temperature (Tbase) and heat units to flowering. Under field conditions common bean had an average base temperature (Tbase) lower than tepary bean, and required more heat units to flower. Genotypic differences for base temperatures and heat unit requirements existed among accessions within both species. Temperature strongly affected the yields of both species when grown at Riverside, CA, on an Arlington fine sandy loam (coarse‐loamy, mixed, thermic Haplic Durixeralf). Tepary bean produced higher yields than common bean under hot summer conditions, but lower yields under early spring conditions.
Forage Quality and Yield of Wheat‐Vetch at Different Stages of Maturity and Vetch Seeding Rates
Authors: Roberts C. A. , Moore K. J. , Johnson K. D.
Published: July 2010

Recent studies have shown that wheat (Triticum aestivum L.) grown in association with hairy vetch (Vicia villosa Roth) has a greater forage quality potential than wheat grown alone. The objective of this study was to evaluate the forage quality of wheat‐vetch with four vetch seeding rates at different stages of maturity. In the fall of 1983 and 1984, field plots were established at the University of Illinois South Farm at Urbana, IL. Wheat was planted alone at a rate of 324 pure live seeds (PLS) per square meter, or in combination with hairy vetch at rates of 0, 54, 108, or 162 PLS/m2 in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. The forage was harvested when wheat was in the boot, anthesis, and milk stages of maturity. Mixed samples and individual fractions were analyzed using standard forage quality procedures. The vetch proportion was 18.4 and 9.9% in 1984 and 1985, respectively. Dry matter yield decreased with increasing vetch seeding rate and increased (P < 0.05) as the season progressed. Crude protein increased (P < 0.05) an average of 46.8 and 22.9% in 1984 and 1985, respectively, as vetch seeding rate increased from 0 to 162 PLS/m2; crude protein was primarily contributed by the vetch fraction, which contained twice as much protein as did wheat in both years. Digestibility (P < 0.05) increased an average of 12 and 1% as vetch seeding rate increased from 0 to 162 PLS/m2 in 1984 and 1985, respectively. Total cell wall concentration was not affected (P > 0.05) by vetch seeding rate. We conclude that the forage quality of wheat‐vetch sown with a vetch seeding rate of 162 PLS/m2 was higher than that of wheat‐vetch with lower vetch seeding rates.
Salt Effects on Germination, Emergence, and Seedling Mortality of Onion
Authors: Miyamoto S.
Published: July 2010

Good stands of furrow irrigated onion (Allium cepa L.) are difficult to obtain in saline areas of the Southwest. This study examined salt effects on seed germination, emergence, and seedling mortality of five onion cultivars in a series of greenhouse experiments at diurnal temperatures of 15 to 25 °C. Germination exceeded 80% within 10 d at solution salinity of 20 dS m−1 or less. Cultivar effects on germination appeared initially, but diminished after approximately 1 wk. Seedling emergence from potted and subirrigated loamy sand declined significantly when salinity of irrigation water exceeded 4.9 dS m−1. This decline was apparently caused by hypocotyl mortality when the cotyledon came into contact with the salts accumulated at the soil surface, but not by reduced seed germination. Soluble salts accumulated mostly within the top 5 mm of the soil and the accumulation below 5 mm was minimal. The removal of the salted surface layer improved seedling emergence. Leaching of the surface‐accumulated salts into the seedling root zone 3 wk after seeding resulted in seedling mortality of significant magnitude; 12 and 20% in seedlings previously subirrigated with solutions of 2.8 and 4.9 dS m−1, respectively. A significant increase in seedling mortality was also observed when seedlings were sprayed twice after emergence with saline solutions of 28 and 39 dS m−1. The ability of cotyledons and seedlings to tolerate salinity, rather than the ability of seed to germinate in highly saline solutions, may be a limiting factor for obtaining good stands in furrow‐irrigated onion in saline areas.
Water Stress and Temperature in Relation to Seed Germination of Pearl Millet and Sorghum
Authors: Smith R. L. , Hoveland C. S. , Hanna W. W.
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a potentially productive high‐quality grain crop that appears superior to sorghum (Sorghum bicolor L. Moench) in establishment under limited soil moisture. Our objectives were to compare sorghum and pearl millet seed germination under moisture stress conditions at two temperatures. Drought resistance was tested by germinating seeds in polyethylene glycol solutions with osmotic pressures of 0, 0.4, 0.8, and 1.2 MPa at 15 and 30 °C. At both temperatures pearl millet germination was less affected by increasing osmotic pressure (OP) than sorghum germination. At 30 °C sorghum germination decreased steadily as OP increased above 0 while pearl millet germination decreased significantly above an OP of 0.8 MPa. At 15 °C, pearl millet germination was always significantly higher than sorghum germination although the germination of both decreased steadily as OP increased. No germination occurred in either species at an OP of 1.2 MPa at 15 °C. The median germination time (MGT) at 30 °C for pearl millet was less than the MGT of sorghum under osmotic stress. There were no differences between sorghum and pearl millet MGT at 15 °C except at an OP of 0.4 MPa. The average MGT was higher at 15 °C than at 30 °C. Median germination time increased with each rise in OP, except for pearl millet between osmotic pressures of 0 and 0.4 MPa at 30 °C. The results indicate that pearl millet seed germinates better than sorghum seed under drought and lower temperature. The ability to germinate under stressful conditions could give pearl millet an advantage in stand establishment under the less than ideal conditions that frequently occur in the field.
Forage Selection by Cattle Grazing Orchardgrass‐Legume Pastures
Authors: Forwood J. R. , Stypinski P. , Paterson J.A.
Published: July 2010

Animal performance can be improved by overseeding legumes into grass swards, but little is known concerning consumption of various legumes over time. This study compared selection of various legumes to grass and weeds, and gathered information helpful in configuring grazing systems. Over two grazing seasons, esophageally fistulated steers (Bos taurus) sampled replicated pasture systems of; (i) orchardgrass (Dactylis glomerata L.) and red clover (Trifolium pratense L.) (OG‐RC), (ii) orchardgrass and birdsfoot trefoil (Lotus corniculatus L.) (OG‐BFT), and (iii) orchardgrass alone (OG) as spring and fall pasture near Columbia, MO. Steers also sampled the same treatments as summer hay regrowth, except that alfalfa [Medicago sativa L.] replaced birdsfoot trefoil in Treatment ii (OGALF). Grass dominated swards and steer diets, but selectivity ratios (SR) indicated no preferential selection for grass by steers. Dietary amounts of birdsfoot trefoil and red clover on pasture, and red clover and alfalfa on hay regrowth were similar, although availability of red clover was generally less than the other legumes. Thus, steers selected red clover to a greater extent over birdsfoot trefoil or alfalfa early in pasture and hay regrowth, and avoided both species during the fall. Average SR values indicate selectivity for weed species was least on OG‐RC followed by OG‐BFT, OG, and OG‐ALF. Diets from grass‐legume systems contained similar amounts of weeds and legumes, but weed proportion increased with time.
Soybean Cultivar Response to Metalaxyl Applied In Furrow and as a Seed Treatment
Authors: Guy S. O. , Oplinger E. S. , Grau C. R.
Published: July 2010

Phytophthora root rot of soybean [Glycine max (L.)Merr.], caused by Phytophthora megasperma Drechs, f. sp. glycinea Kaun and Erwin, is a major disease problem in the Upper Midwest. This study was conducted to determine soybean performance with metalaxyl [N‐ (2,6‐dimethyl phenyl)‐N‐(methylacetyl)alanine methyl ester] fungicide on cultivars with different resistance and tolerance to this disease under low to moderate Phytophthora root rot potentials. Yield, plant density, and a Phytophthora root rot index were determined for metalaxyl treatments applied at labeled rates in furrow (IF) and as a seed treatment (ST) on 10 cultivars in two Wisconsin locations in 1985 and 1986, and IF at 0, 85, 170, and 340 g a.i. ha−1 on five cultivars at two 1987 locations. Yields of two, four, and five cultivars were increased by metalaxyl ST, IF, or IF+ ST treatments, respectively, in two moderate Phytophthora root rot diseased environments. Soybean yields with ST did not differ from IF for any cultivar. The cultivar AP200 with IF+ST treatment yielded more than IF alone. The AP200 plant stand at V2 stage was increased by IF+ST compared with the control. In furrow metalaxyl treatment decreased plant stand compared with ST for ‘S18‐84’. In two 1985 and 1986 environments, without detected Phytophthora root rot, soybean yields were decreased by 280 g ha−1 metalaxyl applied IF at 0.42, 0.25, 0.26, and 0.20 Mg ha−1 for S18‐84, AP200, ‘Century 84’, and ‘L1771’, respectively. However, in additional studies conducted in 1987 at two locations in the absence of Phytophthora root rot, metalaxyl applied at 85 to 340 g ha−1 IF did not influence the yield of five cultivars. Metalaxyl can be an effective fungicide for soybean Phytophthora root rot control; however, yield for certain cultivars may be adversely affected where there is no disease control benefit.
Soil Disturbance‐Residue Management Effect on Winter Wheat Growth and Yield
Authors: Wilhelm W. W. , Bouzerzour H. , Power J. F.
Published: July 2010

The need to reduce soil erosion, maximize soil water conservation, and optimize grain production in dryland cropping systems in the Central Great Plains has culminated in development of nontilled fallow systems. These systems have greatly reduced the degree of soil disturbance, and the amount and degree of residue incorporation. The objectives of this study were to evaluate the influence of soil disturbance and residue management on soil temperature, soil water, and winter wheat (Triticum aestivum L.) growth. Two field studies were established in 1981 and 1982 on an Alliance silt loam (Fine‐silty, mixed, mesic Aridic Argiustoll) with treatments consisting of various degrees of soil disturbance (moldboard plow, tandem disk, and no tillage), residue incorporation (on the soil surface or incorporated), and amount of residue applied (0.0, 0.5, and 1.0 of that produced by the previous crop). Decreased soil disturbance (tillage) and increased residue application decreased maximum, and increased minimum, soil temperatures. In all tillage treatments, soil water content showed a significant positive linear relationship to residue application rate. Grain yield was similar for all treatment factors, except tillage within the 1983‐1984 season when tilled (3.48 Mg ha−1) treatments produced more grain than the nontilled (3.20 Mg ha−1) treatment. Early development and growth of winter wheat was slowed by the presence of residues (surface or incorporated) or the absence of tillage. However, by completion of heading, phenology and yield were similar for all treatments. Cooler soil temperatures slowed development and growth during those stages when the meristem temperature was influenced most by soil temperature. However, after jointing, when air temperature and photoperiod were controlling development and growth, differences among treatments disappeared. Interaction of wheat development with soil temperature, air temperature, and daylength may contribute to the crop's inability to consistently capitalize, in terms of grain yield, on the greater amount of water stored in nontilled and mulched systems.
Environmental Effects on Nitrogen Dynamics in Soybean under Conservation and Clean Tillage Systems
Authors: Harper L. A. , Giddens J. E. , Langdale G. W. , Sharpe R. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.) obtains required N from the soil via root uptake of mineralized organic matter and fertilizer, and from the air by symbiotic gaseous N2 fixation and ammonia (NH3) absorption. The purpose of this study was to evaluate environmental and tillage effects on dynamic N transport under conservation (NT) and clean tillage (CT) management systems. Soil, plant, and microclimate measurements were made concurrently with estimates of gaseous N2 (using 15N2 techniques) and NH3 uptake from the atmosphere. Soybean growth and N uptake characteristics were similar in both tillage systems, except during a 14‐d drought period, which caused water stress in the CT system, but not the NT system. Nitrogen fixation decreased in the CT system to less than half that of the NT system fixation rate, resulting in a seasonal reduction of 29% in the CT system. Net NH3 transport varied from net absorption by the canopy during periods of adequate soil water to net evolution by the CT system during the drought‐stress period. Integration of the net NH3 flux density curves indicated that approximately 3% of the NT system and less than 1% of the CT system plant N was derived from the atmosphere. Also during the drought‐stress period, there was a net loss of plant N to the soil in the CT system indicated by soil and plant mass balance. Insect infestation was much greater in the NT system, reflecting insects' preference for a higher N crop, resulting in a significant N removal from the system. This study showed that soybean in these systems decreased soil N by about the amount of harvested N yield.
Elongation and Branching of Roots on Soybean Plants in a Carbon Dioxide‐Enriched Aerial Environment
Authors: Del Castillo D. , Acock B. , Reddy V. R. , Acock M. C.
Published: July 2010

Plants grown in high CO2 concentrations ([CO2]) often have a higher root weight than those grown in low [CO2]. It is usually assumed that the plants with this extra root weight can explore a greater volume of soil and will, therefore, have more water available to them. To test this assumption, soybean [Glycine max (L.) Merr. cv. Forrest] plants were grown in outdoor, sunlit plant‐growth chambers in [CO2] of 330, 450, 600, and 800 μL L−1 throughout the growing season. The soil containers in the growth chambers had a glass side and new root growth appearing at the glass was measured and marked two or three times each week. Root weight at the end of the season (93 d after emergence) was 26 to 31% higher in [CO2]‐enriched chambers compared with the 330 μL L−1 treatment, and cumulative root length was approximately proportional to [CO2]. However, CO2 treatment did not affect the rate of elongation of individual root axes. Instead, there was a significant linear increase in the number of actively growing roots with increased [CO2]. Plants grown in 800 μL L−1 had 65% more actively growing roots than plants grown in 330 μL L−1. Thus, growing a plant in high [CO2] enabled it to explore a given volume of soil more thoroughly, but did not increase the volume of soil explored.
Wheat Volatilized Ammonia and Resulting Nitrogen Isotopic Fractionation
Authors: O'Deen W. A.
Published: July 2010

Many agricultural crops show significant losses of N from flowering to maturity (during senescence). This research employs 15N fertilization to measure volatilization of NH3 directly from plants. A Plexiglas chamber was designed to isolate the aerial part of winter wheat (Triticum aestivum L. cv. Vona) from its growth medium following anthesis. The system was a continuous free‐flow, open design. Volatilized ammonia was trapped in surfaces of 0.1 M HCl continuously for three separate 90 d runs conducted in 1983, 1984, and 1985. The potted wheat yielded sensitive double‐peaked senescent N bands representing 3 to 4% of the N within the in‐chamber crop. The NH15‐N emission was from the internal N pool of the plant. Wheat tissue total N was determined by gravimetric Kjeldahl procedures employing tube diffusion. Fractionation of 14N and 15N isotopes, previously observed with tube diffusion and steam distillation, provided a basic model for similar fractionation caused by wheat volatilization of NH3. The varying atom percent 15N trends fit a model of continuously increasing wheat 15N content due to volatilization of NH3 with lower 15N content.
Grazing Winter Wheat: I. Response of Semidwarf Cultivars to Grain and Grazed Production Systems
Authors: Winter S.R. , Thompson E.K.
Published: July 2010

Most wheat (Triticum aestivum L.) research in west Texas is conducted in ungrazed wheat that is managed solely for grain production (grain system). In contrast, most commercial wheat is planted early and grazed by cattle (Bos spp.) prior to management for grain production (grazed system). The objective of this research was to understand cultivar × production system interactions. Four semidwarf cultivars, TAM 105, Newton, Vona, and TAM 108, were grown in irrigated grain and grazed production systems for 3 yr. Grazed wheat headed 2.3 d later, had 57 and 62% as much above‐ground biomass and leaf area at heading, was 80% as tall, and yielded 80% as much as wheat grown in the grain system. There was a significant cultivar × system interaction for grain yield 2 yr (P = 0.088 in 1982, P = 0.001 in 1984) caused by differential cultivar response to yield constraints such as lodging, winterkilling, and shattering. In the 3‐yr combined analysis there was no cultivar × system interaction; however, the cultivar × system × year interaction for grain yield was significant (P = 0.003) because yield constraints within systems were not consistent across years. In 1984, extra fertilizer and insecticide reduced grain yield of TAM 108 by 18% (P = 0.001) in the grain system due to increased lodging while having no measurable effect on grain yield in the grazed system. If production systems frequently differ in type or degree of yield constraints, then breeders and agronomist must be concerned with cultivar × system interactions.
Transplanting of Maize During the Winter in India
Authors: Khehra A. S. , Brar H. S. , Sharma R. K. , Dhillon B. S. , Malhotra V. V.
Published: July 2010

Maize (Zea mays L.) cultivation during the winter is a new cropping practice in North India. In this cropping system, maize has slow seedling growth associated with low winter temperatures. If the crop can be grown in a nursery during this slow‐growth period and then transplanted, the crop duration in the main field is shortened. Therefore, the present study was conducted to determine if maize could be successfully transplanted to the field. Other objectives were to evaluate the effect of seedling age, and date and method of transplanting. Experiments were done in the field during two or three winter seasons at two locations. Among the transplanting treatments, 40‐d‐old seedlings transplanted on 24 December and 60‐d‐old seedlings on 16 January resulted in the highest grain yields. Grain yields from these transplantings were 92 to 94% (5314–5402 kg ha−1) of the yield of the crop direct seeded on 9 November (5743 kg ha−1), the optimum sowing time. Grain yield was significantly reduced when younger (up to 20 d) or older (up to 80 d) seedlings were used, with drastic reduction in the latter case. Transplanting of 60‐d‐old seedlings on 24 December and 80‐d‐old seedlings on 16 January yielded only 10 to 12% as compared with the best transplantings. Delayed transplanting (6 February) also decreased grain yield. The comparisons between methods, transplanting on the southern slope of the east‐west ridge or on a flat seed bed, showed that the former improved grain yield. The present study indicates that maize can be successfully produced by transplanting 40‐d‐old seedlings on 24 December and 60‐d‐old seedlings on 16 January, and that transplanting should preferably be done on the ridged seedbed.
Soybean Cultivar Response to Tillage Systems and Planting Date
Authors: Elmore Roger W.
Published: July 2010

The soybean [Glycine max (L.) Merr.] production area in the USA planted with reduced‐tillage practices has doubled in the last two decades. Previous studies show that soybean cultivars yield similarly in various tillage systems when planted in well‐drained soils. Reduced‐till farmers are planting earlier than in the past, but planting date studies with various tillage systems and cultivars have not been reported. A 3‐yr field study was conducted to compare soybean cultivar responses to various tillage systems at various planting dates. Six soybean cultivars were planted on three dates each year (average planting dates were: 7 May, 29 May, and 15 June) with two tillage systems: three passes with a tandem disk in the spring (TD) or notill (NT). A Hastings silt loam soil (fine, montmorillonitic, mesic Udic Argiustoll) was used in 2 yr and a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustoll) was used in the other. The determinate cultivar yielded less when planted on 7 May than on 29 May at 2.72 and 3.14 Mg ha−1 respectively. Indeterminate cultivars had similar yields for these two dates with 2.99 Mg ha−1. Yield of TD was 0.18 Mg ha−1 less than that of NT for 7 May, but was 0.19 Mg ha−1 greater than that of NT for 29 May. There were no tillage × cultivar or tillage × planting date × cultivar interactions. Although planting date was shown to be an important factor in cultivar selection, this study has shown that planting date is not a critical factor in the tillage‐cultivar selection process. The best yielding cultivars in tilled performance tests will likely be the same as those from a no‐till performance test, irrespective of planting date.
Nutrition of Mycorrhizal Soybean Evaluated by the Diagnosis and Recommendation Integrated System (DRIS)
Authors: Bethlenfalvay Gabor J. , Franson Raymond L. , Brown Milford S.
Published: July 2010

Colonization of roots by vesicular‐arbuscular mycorrhizal (VAM) fungi affects host‐plant growth and nutrition, but standard methods to evaluate VAM effects are lacking. The Diagnosis and Recommendation Integrated System (DRIS) may serve this purpose, and an analysis of mycorrhiza‐mediated nutrient‐uptake effects on soybean [Glycine max L.) Merr. cv. Hobbit) plants by DRIS is presented. Plants were grown either colonized by one of three geographical isolates of the VAM fungus Glomus mosseae (Nicol & Gerd) Gerd and Trappe or as nonVAM controls in a nutrient‐deficient soil. Plant development and nutritional status differed among the treatments. Analysis by DRIS confirmed that N, P, and K were limiting, and established different rankings in the degree of deficiency for each nutrient. Nitrogen was least limiting in all four treatments and K or P were most limiting in each of two treatments. The analysis permitted a ranking of the G. mosseae isolates as to their effects on the uptake of each nutrient. Evaluation of VAM‐mediated nutrient‐uptake effects by DRIS and by nutrient‐dilution and concentration analyses could become useful in the selection of specific VAM fungal isolates for their specific crop responses.
Cicer Milkvetch Forage Yield, Quality, and Acceptability to Insects
Authors: Kephart Kevin D. , Higley L. G. , Buxton D. R. , Pedigo L. P.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) has shown potential as a forage legume. A study near Ames, IA, was conducted to determine its herbage yield, forage quality, and acceptability to insects in relation to alfalfa (Medicago sativa L.) and birdsfoot trefoil (Lotus corniculatus L.). Averaged over 2 yr, cicer milkvetch harvested three times each year (3‐cut) had 40 and 18% lower herbage yield than alfalfa and birdsfoot trefoil, respectively. The 2‐cut cicer milkvetch had 20% lower yield than 3‐cut alfalfa, but had similar yield to that of 3‐cut birdsfoot trefoil. Seasonal neutral‐detergent fiber (NDF) concentration for 3‐cut cicer milkvetch was 31 and 20% lower than for alfalfa and birdsfoot trefoil, respectively. Seasonal acid‐detergentlignin (ADL) concentration expressed on an NDF basis for 3‐cut cicer milkvetch was 20 and 37% lower than for alfalfa and birdsfoot trefoil, respectively. Seasonal crude protein concentration was greater for 3‐cut cicer milkvetch than for the other treatments, and seasonal in vitro digestible dry matter was similar for the three species when harvested similarly. Compared with alfalfa, average host acceptability of cicer milkvetch was 98% lower for alfalfa weevil [Hypera postica (Gyllenhal) (Coleoptera: Curculionidae)], 89% lower for potato leafhopper [Empoasca fabae (Harris) (Homoptera: Cicadellidae)], and 84% lower for pea aphid [Acrythosiphon pisum (Harris) (Homoptera: Aphididae)]. Cicer milkvetch has favorable yield and forage quality and should be considered for problem areas prone to these insects.
Seed Production Environment Influence on the Base Temperature for Growth of Sorghum Genotypes
Authors: Lawlor D. J. , Kanemasu E. T. , Albrecht W. C. , Johnson D. E.
Published: July 2010

The base temperature for growth is an important element in plant growth models that utilize heat accumulation methods. The effect of location (environment) on the base temperature for growth of sorghum [Sorghum bicolor (L.) Moench] genotypes was studied. Seeds of six sorghum genotypes were obtained from three locations: Manhattan, KS, College Station and Lubbock, TX. The seeds were placed on moist germination blotter paper on a one‐way thermal gradient plate. Observations were made at least daily for 3 wk to determine the number of days required for (i) germination (i.e., protrusion of the radicle from the seed), (ii) root elongation to 10 mm or longer, and (iii) shoot elongation to 10 mm or longer. The base temperature for germination of each genotype was then determined as the x‐intercept from regressing the rate of germination (i.e., the reciprocal of the number of days required to germinate) vs. the mean temperature. A similar regression was used to determine the base temperatures for shoot elongation and for root elongation of each genotype. The values of base temperature for shoot and root elongation were similar for the genotypes studied, and were consistent with the values of base temperature for emergence of sorghum reported in the literature; whereas the base temperature for germination values were up to 4.6 °C lower than reported values. Results indicated that: the base temperature for shoot elongation is not affected, the base temperature for root elongation is somewhat affected, and the base temperature for germination is more affected by the location (environment) of seed production.
Rhizome and Herbage Production of Endophyte‐Removed Tall Fescue Clones and Populations
Authors: De Battista J. P. , Bouton J. H. , Bacon C. W. , Siegel M. R.
Published: July 2010

Grass endophytes alter the morphology and growth of their hosts. The endophyte (Acremonium coenophialum Morgan‐Jones and Gams) benefits the tall fescue (Festuca arundinacea Schreb.) plant by increasing dry matter production and drought tolerance. Rhizomatous tall fescue was also found to be more persistent and competitive in mixed swards, but the effect of endophyte infection on rhizome expression is unknown. This study was conducted to determine the effect of endophyte removal on rhizome and herbage production of clones and populations of tall fescue. Six clones and four populations (‘Kentucky 31,’ Georgia‐5, Georgia‐Jesup, and Georgia‐Jesup Improved), infected with A. coenophialum and the same clones and populations with the endophyte removed were evaluated for rhizome production, tillering, and herbage and root yield after 12 wk of growth in the greenhouse. No differences in rhizome production were detected between either infected and noninfected clones or populations. However, endophyte infection increased tillering, herbage growth and root growth by 12, 18, and 25%, respectively. A significant (P < 0.01) interaction was detected between endophyte infection and populations for herbage growth with infection increasing herbage growth in Kentucky 31 but decreasing growth in Georgia‐Jesup. Interaction between populations and endophyte infection suggest that the data obtained should not be extrapolated to other germplasm or environmental conditions.
Water Use by Monocropped and Intercropped Cowpea and Sorghum Grown after Rice
Authors: Morris R. A. , Villegas A. N. , Polthanee A. , Centeno H. S.
Published: July 2010

Water remaining in the soil after flooded rice (Oryza sativa L.) is a major source for crops grown during the dry season. To develop improved management systems, quantitative information describing water extraction from previously puddled and flooded fields is needed. Water used by monocropped and intercropped cowpea [Vigna unguiculata (L.) Walp.] and sorghum [Sorghum bicolor (L.) Moench] treatments grown on a fine, mixed, nonacid isohyperthermic Andaqueptic Haplaquoll after harvesting flooded rice was compared to water lost from a fallow treatment. Determinations were to 1.1 m. Water used before cowpea harvest was similar within a treatment among years, but among treatments monocropped cowpea used 172 mm, monocropped sorghum 135 mm, the intercrop 162 mm, and fallow 121 mm. Water used between cowpea and sorghum harvests ranged from 22 to 118 mm, varying with rainfall after cowpea harvest. Species were compared by expressing grain yields in Mg glucose hectare−1 required to synthesize grain. Glucose equivalent yields from monocropped cowpea ranged from 1.90 to 1.98 Mg glucose ha−1, monocropped sorghum from 1.99 to 3.66 Mg glucose ha−1, and the intercrop from 1.99 to 4.36 Mg glucose ha−1. Mean water use efficiency by monocropped cowpea, monocropped sorghum, and the intercrop was 11.3, 12.4, and 16.5 kg glucose ha−1 mm−1. Monocropped cowpea and the cowpea‐sorghum intercrop each use about 50% more water than is lost from fallow. Whereas the cowpea monocrop and the intercrop use about the same quantities of water when grown during the dry season after rice, the intercrop will use water more efficiently but yields from it will not be as stable as those from monocropped cowpea.
Intensive Crop Management Practices on Wheat Yield and Quality
Authors: Mohamed M. A. , Steiner J. J. , Wright S. D. , Bhangoo M. S. , Millhouse D. E.
Published: July 2010

Some researchers have reported increased wheat (Triticum aestivum L.) yields with increased N levels, narrow row spacings (R), and applications of plant growth regulators (PGR) and fungicides (F). However, little information is available concerning the effects of these factors and their interactions on irrigated wheat production in California. Therefore, this study was conducted in the eastern San Joaquin Valley of California at two locations (Dinuba and Fresno) with two planting dates (mid‐December 1986, and late January 1987) to determine the effects of three N levels (168, 220, and 252 kg ha−1), PGR ethephon [Ethephon (2‐chloroethyl) phosphonic acid], and F triadimefon [1‐(4‐Chlorophenoxy)‐3,3‐dimethy‐1‐(lH‐1,2,4‐triazol‐l‐yl)‐2‐butanone] applied to the semidwarf, hard red spring wheat cultivar Yecora Rojo planted at 10‐ and 17‐cm‐row spacings. Early planting increased grain yield, but no other variables affected grain yield or grain protein content. Yield and protein were not increased with N rates above the lowest rate, 168 kg ha−1, Lodging was increased with increasing amounts of applied N, except for the second planting date at Fresno. Applications of PGR reduced lodging but did not effect yield or grain protein, even at increased N levels. A lack of foliar disease resulted in no benefits from F applications. No notable interactions were observed between the different treatments on grain yield, but PGR interacting with other variables generally reduced stem base NO3−N. Intensification of cultural practices was not effective for increasing grain yield and grain protein content in this region with the environmental conditions experienced. This may be due to the already optimized cultural practices used in the region.
Developmental and Growth Effects of Crop Residues on Corn
Authors: Fortin M. ‐C. , Pierce F. J.
Published: July 2010

Residue‐related low soil temperatures have been shown to delay corn (Zea mays L.) emergence and silking dates, but it is unclear how residues affect general crop growth during this period. This study was conducted to determine how crop‐residue effect on corn development during the vegetative stage affects the measurements of various growth characteristics. The effects of small grain residue cover applied around 50% emergence on corn development (time to reach specific stages), growth (aboveground phytomass, height, N uptake) and soil temperatures were investigated on a Conover loam (mixed, mesic, Udollic Ochraqualf) under irrigated no‐tillage conditions. In 1987 and 1988, straw mulch significantly delayed development when compared to a bare soil control, but no consistent difference was found in aboveground phytomass when comparisons were done at similar vegetative stages. Comparisons on a calendar day basis showed significantly lower values for the residue treatment. The latter analysis confounded developmental‐delay effects with actual growth. Similar observations were made for height and N uptake. Consequently, an understanding of plant performance in tillage studies, involving significant developmental differences between treatments, requires that the response curve of a growth characteristic over time be coupled with data on development.
Yield Characteristics of Ancient Races of Maize Compared to a Modern Hybrid
Authors: Gardner F. P. , McCloud D. E. , Valle Raul
Published: July 2010

Open‐pollinated races of maize (Zea mays L.) have been cultivated in the Americas since antiquity although their performance is poor compared to modern hybrids. However, morphological‐physiological characteristics that contribute to the yield superiority of modern hybrids over ancient lines have not been well documented and such information should be useful in the selection of improved open‐pollinated lines and management strategies. Therefore, a study was conducted in Gainesville, FL (29 °38'N lat) to identify and quantify morphological‐physiological traits that are responsible for yield differences between ancient and modern hybrid maize cultivars. The characteristics assessed included photosynthetic capacity, grain‐filling rate and duration, and photosynthate partitioning. Three Central American ancient lines (Chapalote, Nal‐Tel, and Maiz Criollo) and a hybrid (Coker 77) widely adapted to the Southeast USA, were sequentially harvested at 10‐d intervals until physiological maturity for growth analysis. Leaf area index (LAI) and vegetative crop growth rate (CGRv) were similar for all genotypes except for Nal‐ Tel, which had lower values. The hybrid had greater LAI, leaf area duration (LAD), ear and kernel growth rates, as well as kernel number and size. Additionally, the hybrid redistributed more stalkstored photosynthate to the grain, and its grain‐filling period was longer. We conclude that the primary weaknesses of these ancient races compared to hybrids were low LAI and LAD, short grainfilling duration, and low photosynthate redistribution and sink capacity due to fewer and smaller kernels.
Plant Morphology of Cassava During Summer and Winter
Authors: Manrique Luis A.
Published: July 2010

The information on developmental changes in cassava (Manihot esculenta Crantz) in response to environment is often lacking despite interest in such work. This study was conducted to examine how patterns of leaf area development, plant growth, and root production were influenced by seasonal changes in temperature. A field experiment was established during summer 1986 and winter 1987 on the island of Oahu, HI. The growth and yield of the cultivar Ceiba was contrasted across seasons. During a 120‐d period, mean air temperature during summer and winter were 27.0 and 22.5 °C, respectively. Stem numbers per plant did not differ significantly from summer to winter but plants were taller, internodes were longer, branches per stem were greater, and leaf numbers were higher for plants grown during summer. Also, the number and fresh weight of marketable roots (diameter>5 cm) were greater for plants grown during summer. These differences in response between summer and winter crops suggest that plant growth and root yield production of cassava in Hawaii were more efficient during the summer months. Data from this study will be used to validate a cassava growth model being developed for use in agrotechnology transfer in the tropics.
Technique for Simulating Field Drought Stress in the Greenhouse
Authors: Pennypacker B. W. , Leath K. T. , Stout W. L. , Hill R. R.
Published: July 2010

Drought stress in the field develops gradually, allowing plants to acclimate to the stress, however, in the greenhouse it often develops too rapidly to allow acclimation. A technique was developed to induce drought stress on alfalfa (Medicago sativa L.) in the greenhouse, in a manner conducive to plant acclimation. The technique allows: (i) gradual development of drought stress; (ii) use of plants with large root systems; and (iii) imposition of several cycles of drought. The method uses 90‐cm‐tall by 20‐cm‐diam. containers and a growth medium that allows development of plant drought stress within the working range of soil tensiometers. The growth medium, a 2:1 mixture, by volume, of commercial potting mix and coarse sand, is amended with gypsum and slow‐release nutrients. Drought‐stressed plants were shorter than nonstressed plants and had lower leaf and stem dry weights, total aerial biomass, leaf water potentials, stomatal conductances, and osmotic potentials. These responses are indicative of plants undergoing drought acclimation. The technique is an inexpensive, low maintenance method of inducing a gradually intensifying drought stress in the greenhouse.
Soil pH and Calcium Effect on Nitrogen Fixation and Growth of Board Bean
Authors: Schubert Erika , Mengel Konrad , Schubert Sven
Published: July 2010

Nitrogen fixation and growth of broad bean (Vicia faba L.) are adversely affected by low soil pH. This investigation was conducted to determine whether pH effects can be alleviated by Ca, and whether low pH primarily limits growth of the host plant or symbiotic N2 fixation. The Vicia faba L. cv. Kristall was grown in pots on a Dystrochrent at different pH and Ca levels. Dinitrogen fixation was measured using a nondestructive acetylene reduction method. Exchangeable soil Ca had no major effect on yield, total N uptake, or nitrogenase activity. At low pH (pH 4.7 and 5.4), dry matter production, seed yield, and N2 fixation were significantly lower than at the higher pH levels (pH 6.2 and 7.0). Low pH delayed the development of nitrogenase activity. Rates of acetylene reduction correlated significantly with plant N content. The N concentrations in the various plant parts of pH 5.4 treatment were as high as in treatments with higher pH levels. The slight yield depression found at this moderately low pH is therefore assumed to be a direct effect of H+ activity in the soil on the growth of the host plant. However, at pH 4.7, plants showed N deficiency symptoms during early growth, which suggests pH limitation of N2 fixation. Dry matter production of young plants not dependent on rhizobial N2 fixation was significantly decreased at low pH 4.7, 5.6, and 6.2 relative to pH 7.0.
SOYWEED: A Simulation Model of Soybean and Common Cocklebur Growth and Competition
Authors: Wilkerson G. G. , Jones J. W. , Coble H. D. , Gunsolus J. L.
Published: July 2010

The yield reduction caused by a particular weed species depends not only on weed density, but also on many other factors which affect both crop and weed growth through time. The objective of this study was to develop a simulation model of crop/weed competition which could be used to investigate the effects of environmental conditions on weed and crop growth. A previously developed soybean crop growth model was used to simulate the growth of soybean [Glycine max (L.) Merr.]. A weed growth model was developed and coupled with the soybean model to describe growth of weed and soybean growing together and competing for resources. Published data from a field experiment were used to determine model parameters for common cocklebur (Xanthium strumarium L.). In the combined soybean‐weed model, only competition for light and water are considered. Competition for light occurs within an “area of influence” around each weed. The size of this area depends on weed canopy diameter, which increases as a function of weed leaf area. Competition for water has been modeled by using a field average total leaf area (weeds and soybean) in the calculation of potential transpiration. The model developed from 1 yr of data fit data from another year reasonably well. The approach developed in this research is a practical way for modeling crop/weed competition which incorporates both the effect of environment on growth processes and the nonuniform effect of a weed on crop plants at different distances from the weed.