bluuebunny/crossref_metadata_2025 huggingface dataset:
Choosing the Best by Ranking and Selection
Authors: Lund R. E. , Cherry J. S. , Martin J. M.
Published: July 2010

Selecting the best treatment(s) is a common problem in agricultural research. The usual procedure is to rank all treatment means and to claim the best treatment(s) are the highest (or lowest) subset found not to differ significantly according to a traditional multiple comparison (TMC). A least significant difference (LSD) procedure is applied most frequently. Our objective is to introduce a somewhat new methodology called simply ranking and selection (R&S) by way of agronomic examples and to illustrate why R&S may be preferred over TMC for selecting the best. Steps similar to those when using TMC to select the best are applied by R&S but it uses tabled values distinctive to several criteria for specifying “bestness.” We concentrate upon both identifying the one best treatment and selecting the subset containing that one best, but unspecified treatment. The R&S method assumes outright that the true unknown treatment means (population means) are unequal. Probabilities are derived from available information about that inequality and pertain specifically to the likeliness of making a correct selection. Conversely, LSD was developed upon the framework of testing the explicit hypothesis of equality for two specific population means and the most evident probability pertains precisely to incorrectly rejecting that equality. Probabilities associated with correctly identifying means, which are not equal, are considered only indirectly by LSD. Two examples from agronomic literature are used to demonstrate R&S methodology. We are recommending that agricultural researchers continue to use TMC for the broad general purpose for which it was designed, but furthermore, we are suggesting they become familiar with R&S and apply it for the specific purpose for which it was designed.
Temperature Effects on Cotton Canopy Growth, Photosynthesis, and Respiration
Authors: Reddy V. R. , Baker D. N. , Hodges H. F.
Published: July 2010

The ecological range of temperature conditions where cotton (Gossypium hirsutum L.) is commercially grown frequently exceeds the temperature range of available data. To predict growth, development, and responses of the primary physiological processes to those conditions, data at both lower and higher temperatures are needed. Cotton plants were grown in naturally lit, temperature‐ and CO2− controlled chambers. Plants grown at near‐optimum temperatures (30 and 35 °C day temperature) fixed twice as much CO2 at high photosynthetically active radiation during the fruiting period as did plants growing at 20 °C. Growth exhibited similar differences due to temperature during the boll‐filling period. Plants with heavy fruiting load partitioned less to vegetative structures. Most plants grown at 35/25 °C day/night temperatures and all those grown at 40/30 °C had serious flower survival problems. No fruits were harvested from the plants grown in the 40/30 °C chamber and only a few from those grown in the 35/25 °C chamber. Gross photosynthesis, canopy light utilization efficiency, and canopy conductance were found to be highly variable from day to day. This variability should be considered by investigators measuring short‐term CO2 exchange rates. Respiration rates of cotton plants were 45% higher during the first hour of dark than during the rest of the night. These data suggest that carbohydrate is more readily available for respiration during and immediately after the light period than later in the dark period.
Nutrient and Carbohydrate Partitioning in Sorghum Stover
Authors: Powell J. M. , Hons F. M. , McBee G. G.
Published: July 2010

Although petroleum fuels have been abundant during the past decade, alternative energy sources are needed for the long term. Sorghum [Sorghum bicolor (L.) Moench] stover has been demonstrated to be a potential biomass energy source. Complete above‐ground crop removal, however, can result in soil degradation. Differential dry matter, nutrient, and carbohydrate partitioning by sorghum cultivars may allow management strategies that return certain stover parts to the field while removing other portions for alternative uses, such as energy production. A field study was conducted to determine N, P, K, nonstructural carbohydrate, cellulose, hemicellulose, and lignin distributions in stover of three diverse sorghum cultivars of differing harvest indices. Determinations were based on total vegetative biomass; total blades; total stalks; and upper, middle, and lower blades and stalks. Concentrations of N and P were higher in blades than stalks and generally declined from upper to lower stover parts. Large carbohydrate and lignin concentration differences were observed on the basis of cultivar and stover part. Greater nutrient partitioning to the upper third of the intermediate‐ and forage‐type sorghum stovers was observed as compared to the conventional grain cultivar. Stover carbohydrates for all cultivars were mainly contained in the lower two‐thirds of the stalk fraction. A system was proposed for returning upper stover portions to soil, while removing remaining portions for alternative uses.
Ontogeny and Water Use of No‐Tillage Sorghum Cultivars on Dryland
Authors: Unger Paul W.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] yields are strongly influenced by soil water content at planting and use of that water during the growing season. Sorghum on Pullman soils (fine, mixed, thermic Torrertic Paleustolls), however, usually does not use water from as deep in the soil as other crops, thus possibly not attaining its full yield potential. This study was conducted from 1986 to 1989 to determine whether eight sorghum hybrid cultivars grown under no‐tillage conditions on a dryland Pullman clay loam at Bushland, TX, differed with respect to water use depth, growth, yield, yield components, total water use, and water use efficiency. The hybrids were Pioneer 8493; Funk 1498 and 499; DeKalb DK‐46, DK‐42, and DK‐41Y; and Richardson 9112 and Sprint. Determinations included precipitation and soil water use, water use efficiency, grain and stover yield, harvest index, panicles harvested, panicle/seedling ratio, seed per panicle, seed per unit area, and weight per seed. Based on water content measurements, there was no conclusive evidence that any cultivar depleted soil water deeper or to a greater extent than the others, but the highest yielding cultivar (DK‐41Y, mean yield of 5.22 Mg ha−1) was among the highest water users each year, suggesting that this cultivar uses water effectively for grain production. Multiple regression analyses involving all cultivars showed that grain yield was most strongly affected by weight per seed, but this was closely followed by seed per unit area. Other variables significantly related to grain yield were planting seed (number per gram), panicle/seedling ratio, panicles harvested, and stover yield. Overall, this study showed that high grain yields are achieved by cultivars that use available water supplies or that respond to improved water conditions during the growing season to produce vigorous plants capable of converting photosynthate into high quality grain. Although deeper and more intensive soil water use is desirable, sorghum improvement programs should not neglect other traits that can also result in more efficient grain production.
Effect of Soil Surface Treatments on Runoff and Wheat Yields under Irrigation
Authors: Stern R. , Van Der Merwe A.J. , Laker M.C. , Shainberg I.
Published: July 2010

In arid and semi‐arid regions, where soil structure is unstable, surface runoff due to seal formation reduces irrigation water use efficiency. This study was conducted to determine the efficiency of surface treatments in reducing runoff and increasing wheat crop productivity. Surface runoff from wheat plots on a non‐sodic, silty clay loam soil (Rhodudalf silty clay loam), sprinkler irrigated with a good quality irrigation water, was collected using flumes and collection boxes. Percentages of runoff were 36.1% of the total irrigation during the growing season for the control (Ct), 12.8% for phosphogypsum (PG), 1.4% for polyacrylamide plus PG (PAM), and 1.1% for pitting plus PG (Pt) treatments. The mulching effect of the growing canopy did not reduce runoff during consecutive irrigations as the season progressed. Water content in the profile was correlated with the amount of water that infiltrated into the soil. The crop biomass production in the Pt and PAM treatments was significantly higher than the PG and Ct treatments (8.81 and 7.91 vs. 6.41 and 5.47 Mg ha−1, respectively). The Pt and PAM treatments also gave significantly higher grain yield (3.66 and 3.02 vs. 2.25 and 2.12 Mg ha−1, respectively). The Pt, PAM, and PG treatments resulted in significantly higher irrigation water use efficiency (IWUE) than the Ct. The PAM is the least known treatment and is given special attention in this study. In regions where water is scarce and costly, improving the efficiency of irrigation by tillage or soil ameliorants should be considered.
Effect of Mono and Mixed Culture of Tall Fescue and Birdsfoot Trefoil on Yield and Quality
Authors: Beuselinck P.R. , Sleper D.A. , Bughrara S.S. , Roberts C.A.
Published: July 2010

Growth habit of grass and legume cultivars may affect their competitiveness, yield, and herbage quality in grass‐legume mixes. The objective of this research was to examine herbage yield and quality of mixed cultures of tall fescue (Festuca arundinacea Shreb.) genotypes and birdsfoot trefoil (Lotus corniculatus L.) cultivars with contrasting growth habits. High (HLAER) and low (LLAER) leaf‐area‐expansion‐rate tall fescue populations and prostrate (‘Dawn’) and upright (‘Viking’) birdsfoot trefoil cultivars were used. Eight treatments comprising monocultures of the four entries (HLAER, LLAER, Dawn, Viking) and 1:1 mixed cultures of each possible interspecific combination of the entries were transplanted into field plots in June 1983 and harvested at a 3‐ or 6‐wk frequency in 1984 and 1985. Mixed cultures were hand‐separated into tall fescue and birdsfoot trefoil components prior to drying. Herbage dry weight (DWT), in vitro dry matter digestibility (IVDMD), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were measured. Mixtures of tall fescue and birdsfoot trefoil were moderately compatible regardless of growth form of species. When grown in mixed cultures, yield of tall fescue and birdsfoot trefoil was reduced by interspecific competition. Growth form of either species did not appear to affect DWT of mixed cultures. Herbage yield of tall fescue and birdsfoot trefoil was influenced by harvest frequency. Yield and quality of tall fescue‐birdsfoot trefoil mixed cultures can be greater than monocultured tall fescue.
Yield Losses in Winter Wheat Caused by Low‐Density Cereal Aphid Populations
Authors: Kieckhefer R.W. , Gellner J.L.
Published: July 2010

In most autumns on the Northern Plains of the USA, low population densities of several species of cereal aphids feed on seedling winter wheat, Triticum aestivum L., for a month or more. The objective of this research was to determine the influence of that feeding on the growth and yield of ‘Rose’ winter wheat. Experiments were conducted by confining non‐viruliferous (barley yellow dwarf virus) greenbug, Schizaphis graminum (Rondani), at precisely maintained population densities of 2, 4, 6, 8, 10, and 15 aphids per plant, bird cherry oat aphids, Rhopalosiphum padi (L.), at densities of 10 or 15 aphids per plant, or Russian wheat aphids, Diuraphis noxia (Mordvilko), at 5, 10, 15, and 20 aphids per plant on seedling plants for 30 d in an environmental chamber at 10°C (to simulate mean October temperature in the field), 12 h day/night. The results showed that the threshold for significant yield loss under these environmental conditions was at the 10 aphids per plant level for the bird cherry oat aphid and the Russian wheat aphid, and 15 aphids per plant for greenbug. Yield losses caused by any of the aphid species were in the range of 35 to 40% at 15 aphids per plant. Although the visible injury to plants caused by the feeding of the greenbug and the Russian wheat aphid was striking, the bird cherry oat aphid was as damaging to yield as the other two species in this study.
Crop Sequence Affects Nutrient Composition of Corn and Soybean Grown under High Fertility
Authors: Copeland P. J. , Crookston R. K.
Published: July 2010

Although crop rotation may change soil mineral status, particularly N, there may also be a rotation effect beyond that which can be explained by soil mineral status alone. Research has shown that leaf mineral‐composition can vary between crop sequences at high fertilizer levels. We hypothesized that the rotation effect observed in longterm sequences of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] might be due to an increased nutrient concentration, not just an increased accumulation. A corn‐soybean rotation study in Minnesota managed at high nutrient fertility was used to test our hypothesis. The high management level was appraised by soil test levels. Corn and soybean sequences evaluated were monoculture, first year, second year, and annually‐alternated. These crop sequences were evaluated for their effects on plant nutrient concentration, accumulation, or both. The growth stage at which differences in plant nutrient concentration or accumulation might affect final yield was also evaluated. A positive effect of rotation on yield was observed in both crops. Shoot concentrations and total accumulations of N, P, and K were higher in first year corn compared to monoculture, suggesting that the increased corn yield associated with rotation may have been due to a general improvement in plant nutrition. Cropping sequence had less of an effect on soybean nutrient concentration than corn. Nutrient accumulation in soybean was not generally affected by crop sequence.
Conventional vs. No‐Till Corn Following Alfalfa/Grass: Timing of Vegetation Kill
Authors: Smith M. A. , Carter P. R. , Imholte A. A.
Published: July 2010

Producers who plant no‐till corn (Zea mays L.) following hay or pasture are concerned about herbicide application timing and efficacy to kill perennial vegetation, plant residue effects on corn growth, and optimal corn planting date. A field study was conducted near Arlington, WI, from 1985 to 1988 to evaluate the influences of (i) conventional (CT) vs. no‐till (NT), (ii) fall vs. spring kill of perennial vegetation, (iii) late‐April vs. mid‐May planting, and (iv) three hybrid maturities on corn following legume/grass sod. Parameters measured include residue cover, soil temperature, and soil moisture after planting; corn emergence percentage; days to emergence; days to silk; grain moisture; and grain yield. Tillage by time of vegetation kill interactions were important for corn development and grain yield. Few differences were observed between fall and spring plowing in CT. For NT, however, chemically killing perennials in the spring compared to in the fall resulted in greater residue cover after planting (6–90% vs. 40%), and cooler and drier soil in the seed zone after planting. Emergence was delayed 1.5 to 4.0 d with spring‐kill NT and subsequent development was delayed throughout the growing season. Spring‐kill NT resulted in lower grain yields (−10 to −50%) compared to fall‐kill NT in 3 of 4 yr. For NT, when perennial vegetation was killed in the fall and corn was planted early, plant growth and grain yields were comparable to those for CT. Fall‐kill NT produced consistent growth and yield responses during the study years, whereas spring‐kill NT results were more variable, with poorest results in the drought of 1988.
Colonization of Soybean by Mycorrhizal Fungi and Spore Populations in Iowa Soils
Authors: Khalil S. , Loynachan T. E. , McNabb H.S.
Published: July 2010

Mycorrhizae, a mutualistic association between fungi of the family Endogonaceae and higher plants, have been studied extensively in the greenhouse, but much less is known about the natural ecology of these fungal‐plant associations in field soils. A better understanding of the mycorrhizae of agronomic crops is needed because of their potential involvement in systems of sustainable agriculture. This study reports on the extent of root colonization by mycorrhizal fungi, the distribution of mycorrhizal fungal spores in the rhizosphere, and the mycorrhizal fungal genera associated with soybean [Glycine max (L.) Merr.] in 15 Iowa soils. Results indicated that soybean roots from most soils, in spite of some soils having very high soil‐test P levels, were extensively colonized (60–100%) by vesicular‐arbuscular mycorrhizal (VAM) fungi. Colonization was determined by evaluating the percentage of root segments with VAM fungi. The average colonization of plant roots from all soils was 89%, and the average Bray P1 soil‐test value was 60.3 mg kg−1 (values greater than 30.5 are considered by the Iowa State Soil Testing Laboratory to be very high). Abundant colonization was unexpected in these high‐P fertility soils because most authors report extensive colonization to occur mainly in plants growing in soils of low fertility. The VAM fungal spores were quite common in all rhizosphere soils sampled and ranged from 66 to 998 spores 100 g−1 soil. Total spore counts were significantly different among soil series (P < 0.001) and within soil series (P < 0.01). A negative correlation (P < 0.05) was found between soil organic matter, P, and VAM fungal colonization. For VAM fungal genera (Glomus, Gigaspora, Acaulospora, and Scutellospora) were found associated with soybean rhizosphere soil. Among these, Glomus was the most abundant.
Seed Germination Response of Four Southwestern Range Grasses to Equilibration at Subgermination Matric‐Potentials
Authors: Hardegree Stuart P. , Emmerich William E.
Published: July 2010

Seed priming at subgermination water potential has been shown to enhance the germination response of a wide number of plant species. Optimal priming conditions for germination enhancement are usually found to be at the least negative water potential that prevents radicle emergence. Equilibration of seeds at more negative water potentials may have detrimental effects on germination relative to control treatments. Seeds of Bouteloua curtipendula (Michx.) Torr., Cenchrus ciliaris L., Eragrostis lehmanniana Nees, and Panicum coloratum L. were equilibrated over the matric potential range of −1.6 to −17.5 MPa and germinated over the matric potential range of 0 to −1.6 MPa. Matric‐priming at −1.6 MPa frequently increased germination percentage and rate at reduced water potential. Matric‐priming at water potentials more negative than −1.6 MPa had a less positive and sometimes detrimental effect on germination relative to control treatments. Germination response of primed seeds showed a tendency toward, but not necessarily achievement of, control levels at the most negative priming‐water potentials.
Fertilizer Placement and Tillage Effects of Nitrogen Assimilation by Wheat
Authors: Rao S.C. , Dao T.H.
Published: July 2010

Little information is available concerning tillage effects on seasonal N accumulation and their effect on wheat yield. Field studies were conducted to determine the effects of fertilizer N placement and tillage practices on the reduction and assimilation of N in winter wheat (Triticum aestivum L.) during 1984 through 1987 on Renfrow silt loam (fine, mixed, thermic, Uderic, Paleustolls) near El Reno, OK. Fertilizer N (50 kg ha−1) and P (60 kg ha−1) including 4 kg N ha−1 and 11 kg P ha−1, with the seed was applied in the fall. In the spring, an additional 50 to 100 kg N ha−1 as ammonium nitrate was either broadcast or placed in narrow bands on the soil surface. Nitrate reductase (NR) activity, NO3‐N, and crude protein (CP) content of wheat plants were determined periodically during spring growth until anthesis, and final grain and straw yield and their CP contents were determined. The NR activity in early spring was slightly greater during early spring in plants grown under no‐till when compared to conventional till in 1985 and 1986, whereas the reverse was observed in 1987. Increased NR activity was paralleled by an increase in vegetative CP. Placement of N in a narrow band on the soil surface in the spring improved NR activity levels, but the effect of N placement had little effect on CP concentration. Grain yield followed NR activity levels and was 36% higher in no‐till in 1985, similar in 1986, but 51% lower in 1987 than conventionally tilled plots. Placement of N in narrow bands increased N‐use efficiency by increasing N reduction and assimilation; but had little effect on the yield of grain and straw in both tillage methods.
Photosensitization in Lambs Grazing Switchgrass
Authors: Puoli J. R. , Reid R. L. , Belesky D. P.
Published: July 2010

Hepatogenous photosensitization has been recorded in herbivores grazing a number of Panicum species in different areas of the world. This condition was observed in weaned and suckling lambs (Ovis sp.) grazing switchgrass (Panicum virgatum L. cv. Cave‐in‐Rock) in Morgantown, WV, during the abnormally hot, dry summer of 1991. The first cases occurred in June, 35 d after initiation of grazing. Further cases occurred with a new group of lambs 12 d after their introduction to switchgrass pastures in late July. Of a total of 104 lambs, 17 showed photosensitization and eight died. Symptoms were similar to those reported for ‘geeldikkop’ in sheep and hepatotoxicity was confirmed by changes in blood metabolites. Mature ewes were not affected and no signs of photosensitization were noted in suckling lambs grazing switchgrass during the previous year under more normal temperature and rainfall conditions. Photosensitization does not appear to have been observed in cattle on switchgrass but monitoring of younger animals grazing this Panicum species seems desirable.
Available Water and Nitrogen Effects on Yield Components and Grain Nitrogen of Zero‐Till Spring Wheat
Authors: Campbell C. A. , Selles F , Zentner R. P. , McConkey B. G.
Published: July 2010

Straw yield is important in soil conservation and nutrient cycling. Grain N concentration is of economic importance, and variations in yield components can be used to improve our understanding of grain yield response to environmental stimuli. Therefore, quantifying these responses in relation to soil water and N fertility is of considerable importance. A 9‐yr study was conducted in southwestern Saskatchewan on a medium textured Aridic Haploboroll using zero‐tillage management. We examined the influence of snow trapping and fertilizer management (rate, placement, and time of N application) on hard red spring wheat (Triticum aestivum L.) grown annually. Multiple regression was used with backward elimination to relate straw yield, heads per plant, kernel weight, and grain N concentration to available water use (WU), fall soil NO3−N in 0‐0.6 m depth (SN), rate of urea fertilizer N (FN), years of consecutive cropping (Yr) and several interactions among these variables. Significant (P < 0.0001) meaningful relationships were obtained betwen straw yield (R2 = 0.78, P = 0.001), kernel wt (R2 = 0.81, P = 0.001), heads/plant (R2 = 0.36; P = 0.001) and grain N concentration (R2 = 0.56, P = 0.001) and the independent variables. In this semi‐arid region, WU was by far the most important factor influencing all characteristics. The effect of SN was often more important than that of FN. Further, the advantage of SN over FN increased with years of cropping, possibly reflecting a gradual increase in the N supplying power of this well‐managed soil. Straw yield was related to grain yield. The relationship expressed in kilograms per hectare, was SY = 285 + 0.77 GY + 0.00029 GY2, R2 = 0.85, P = 0.001, n = 1248). Grain N concentration was greater for spring than for fall‐applied N in 5 of 9 yr, and deep banding superior to broadcasting in 1 of 9 yr.
Water Deficit Effects on Osmotic Potential, Cell Wall Elasticity, and Proline in Five Forage Grasses
Authors: Barker D. J. , Sullivan C. Y. , Moser L. E.
Published: July 2010

Physiological responses of forage grasses to water deficit are not well documented, but may be important in determining drought resistance. The objective of this study was to determine the response of osmotic potential, leaf proline concentration, and cell wall elasticity to water deficit for the C4 (warm‐season) grasses ‘Nebraska 54’ indiangrass [Sorghastrum nutans (L.) Nash], ‘Pathfinder’ switchgrass (Panicum virgatum L.), and ‘Pawnee’ big bluestem (Andropogon gerardii Vitman), and the C3 (cool‐season) grasses, ‘loreed’ reed canarygrass (Phalaris arundinacea L.), and ‘Lincoln’ smooth bromegrass (Bromus inermis Leyss.). Other measurements included leaf water potential, soil water content, and osmotic adjustment. A field study at Mead, NE, and a complementary greenhouse study at the University of Nebraska, Lincoln, found osmotic adjustment occurred in response to water deficit for all species, and was greater for C4 than for C3 grasses. Despite less osmotic adjustment, C3 grasses had more elastic cell walls (low modulus of cell wall elasticity), which maintained turgor despite loss of water. Leaf proline concentration averaged 20 times greater in stressed compared to well‐watered plants grown in the greenhouse. Proline accumulation in greenhouse‐grown plants was much larger than observed under field conditions. The physiological role of proline accumulation was uncertain because even dramatic increases in leaf proline concentration were insufficient to influence osmotic potential.
Field Response of Soybean to Nodulation by a Rhizobitoxine‐Producing Strain of Bradyrhizobium
Authors: Vasilas Bruce L. , Furhmann Jeffrey J.
Published: July 2010

Nodulation by rhizobitoxine‐producing (RT+) strains of Bradyrhizobium japonicum has been shown to decrease shoot growth of green‐house‐grown soybeans. The potential impact of nodulation by a RT+ strain on the productivity of field‐grown soybeans has not been determined. Therefore, a field experiment was conducted for 2 yr on a Matapeake silt loam (fine‐silty, mixed, mesic Typic Hapludults) to determine the response of soybean cv. ‘Forrest’ to nodulation by one RT+ strain (USDA 94). Inoculation treatments were (i) USDA 94, (ii) a mixture of bradyrhizobia indigenous to the field site (Control), and (iii) a combination of Treatments 1 and 2 (USDA 94/Soil). Inoculation treatments were applied to the seed and the seedlings were grown for about 21 d under greenhouse conditions. Pre‐nodulated seedlings were transplanted to 1.8‐m2 field microplots. Inoculation with USDA 94 reduced plant N derived from fixation (as measured by isotope dilution) by 43% relative to the Control (2‐yr mean). Inoculation with USDA 94 decreased seed yield by 38%. Yield reductions were associated with reductions in pod number. The USDA 94 inoculation decreased vegetative growth, delayed the onset of full pod, beginning seed and full seed stages, and doubled the interval between beginning pod and full pod stages. For most of the parameters measured, USDA 94 and USDA 94/Soil treatments produced similar results. This research demonstrated that nodulation by USDA 94 can significantly alter shoot growth and reduce seed yield of field‐grown soybeans.
Logistic Response of Bermudagrass and Bunchgrass Cultivars to Applied Nitrogen
Authors: Overman A. R. , Sanderson M. A. , Jones R. M.
Published: July 2010

Models provide a quantitative means to evaluate yield response of forage grasses to applied N and water availability. The objective of this analysis was to estimate model parameters (A, b, c) for bermudagrasses and bunchgrasses grown at the same location and during the same time period. The logistic equation was used to relate annual dry matter production to applied N for three bermudagrasses [Cynodon dactylon L., ‘Coastal’, ‘Alicia’, and ‘Coastcross‐1’] and four bunchgrasses [Eragrostis curvula (Schrad.) Nees, ‘Morpa’ and ‘Renner’ lovegrass; Panicum coloratum L., ‘Selection‐75’ kleingrass, and Cenchrus ciliaris L., ‘Strain 18‐35’ buffelgrass]. Data were from 4 yr of field experiments at Stephenville, TX. Analysis of variance was used to show that the N coefficients b and c were independent of year and climate for each grass, in agreement with recently published results. Applied N required to provide one‐half of maximum yield was approximately 150 kg ha−1 for bermudagrass and 50 kg ha−1 for lovegrass. Variation among years was accounted for in the linear coefficient A, which was then related to rainfall. Bunchgrasses typically had lower A and b, but similar c values compared with bermudagrasses. The logistic model allows estimates of yields in terms of applied N and rainfall, and quantifies the interaction between these two factors. Bermudagrass yielded approximately 45% more dry matter than lovegrass for the same rainfall. Correlation coefficients exceeded 0.95 throughout the analysis.
Soil Temperature, Soil Water, and No‐Till Corn Development Following In‐Row Residue Removal
Authors: Fortin M.‐C.
Published: July 2010

In northern areas where corn (Zea mays L.) is grown, no‐till plants develop more slowly and, consequently, could be more susceptible to soil water limitations than plants under conventional tillage. This study was conducted to determine if removing in‐row residues by pushing them into the interrow can solve problems related to no‐till corn development in droughty soils. Residues were removed to produce a 30‐cm band of bare soil along the corn row. This bare row no‐tillage (BRNT) treatment was compared with conventional tillage (C), regular no‐tillage (NT), and bare no‐tillage (BNT) for plant development, plant height, crop yield, soil water content in the upper soil layers, and seed zone temperature. The BRNT seed zone temperature was higher than that of NT and similar to that of C and BNT from emergence to the V6 stage. Accordingly, BRNT plants reached the V6 stage 1.3 and 3.7 d later than C while NT reached the V6 stage 5.0 and 7.2 d later than C in 1990 and 1991, respectively. In 1991, NT plants were further retarded by hot and dry conditions despite the fact that interrow soil water was higher in treatments with interrow residue cover. Height differences among treatments were related to developmental differences. Despite considerable changes in soil temperature, water, developmental rate, and height of plants among treatments during the vegetative stage, reproductive yield was not affected by tillage and residue treatments.
Post‐Anthesis Nitrogen Loss from Corn
Authors: Francis D. D. , Schepers J. S. , Vigil M. F.
Published: July 2010

Published research has shown relatively large amounts of NH3 being lost from aboveground vegetation during grain development for various grain crops For corn (Zea mays L.), maximum net N accumulation usually occurs during early reproductive development (R1‐R3) and a subsequent decline is often observed. Two recently completed N fertilizer recovery studies on irrigated corn utilizing isotopic techniques were re‐examined to quantify post‐anthesis N losses from aboveground biomass of irrigated corn under different N regimes. These studies were conducted at different sites, in different years, with fertilizer rates ranging from 50 to 300 kg N ha−1. Measured losses of labeled N from aboveground plant material ranged from 7 to 34 kg N ha−1. Isotopic dilution suggests that apparent real N losses from aboveground biomass ranged from 45 to 81 kg N ha−1, assuming there is no selectivity for N source (i.e., 15 N vs. 14N). Plant N losses accounted for 52 to 73% of the unaccounted‐for N in 15N balance calculations. Failure to include direct plant N losses when calculating an N budget leads to overestimation of losses from the soil by denitrification, leaching, and ammonia volatilization. Proper accounting for volatile plant N losses may improve management strategies that affect N fertilizer use efficiencies.
FLOWDATA: Software for Analysis of Infiltration Data from Automated Infiltrometers
Authors: Ankeny M. D. , Prieksat M. A. , Kaspar T. C. , Noh K. M.
Published: July 2010

Soil hydraulic properties are quite variable, and characterization of field sites usually requires many measurements. One way to collect the data needed for field site characterization is to use multiple infiltrometers with automated data collection capabilities. Automated infiltrometers use pressure transducers connected to a datalogger to measure cumulative infiltration over time. The FLOWDATA software was developed to reformat, graphically display, and analyze the large well‐structured data sets collected with automated infiltrometers. Program features include interactive editing, graphing, statistical summaries for each infiltration data set, and pooling of estimates from multiple data sets. Inputs required are identification codes, times, transducer voltage readings, and transducer calibration files. Outputs are infiltration rates, and saturated and unsaturated hydraulic conductivities. Program performance is demonstrated with data from a typical field data file.
Sowing Depth and Soil Water Effects on Seedling Emergence and Root Morphology of Three Warm‐Season Grasses
Authors: Roundy Bruce A. , Winkel Von K. , Cox Jerry R. , Dobrenz Albert K. , Tewolde Haile
Published: July 2010

Greater seed burial has been suggested as a way to increase the time of water availability to seeds and seedlings in revegetation of semiarid rangelands. The effects of sowing depth on seedling emergence and root development of ‘Vaughn’ side‐oats grama [Bouteloua curtipendula (Michx.) Torr.], ‘A‐130‘ blue panic (Panicum antidotale Retz.), and ‘Cochise’ atherstone Iovegrass (Eragrostis lehmanniana Nees × E. tricophora Coss. & Dur.) were measured in relation to water availability on a sandy loam soil in the greenhouse. Side‐oats grama and blue panic were sown at depths of 0, 10, 20, and 30 mm, while Cochise lovegrass was sown at 0, 5, 10, and 15 mm. Pots were subirrigated every 3 d, on Days 1 and 7 after sowing, or on Day 1 only. Soil water contents in the greenhouse were initially higher and decreased more rapidly than those of field seedbeds. Seedling emergence was generally highest from surface‐sown seeds and decreased with depth of sowing, possibly due to lack of aeration. All three warm‐season grasses elongated their subcoleoptile internodes to place the coleoptilar node and site of adventitious root initiation near the soil surface, regardless of sowing depth. Adventitious roots required 9 to 13 d of available water to initiate. Seminal root growth and depth were not increased with increased sowing depth. Seminal root elongation rates from 5.8 to 8.7 mm d−1 are not fast enough to stay ahead of a typical drying front of 15 to 20 mm d−1 during the summer rainy season on sandy loam soils in southern Arizona. Frequent rainfall is apparently necessary to permit adventitious root development and establishment of these species.
Using GIS Datasets to Classify Maize‐Growing Regions in Mexico and Central America
Authors: Pollak Linda M. , Corbett John D.
Published: July 2010

The environments in which maize (Zea mays L.) germplasm originated and in which it is evaluated can substantially affect results from germplasm evaluations, thus influencing where the germplasm will eventually be used. The adaptation classifications normally used (e.g., temperate, tropical, subtropical, and highland) are imprecise. Our objectives were to (i) apply multivariate statistical techniques to spatial GIS (geographic information system) datasets of agroclimatic data to group similar maize‐growing regions in Mexico and Central America and then (ii) use the groups to refine the mega‐environments developed by CIMMYT maize breeders to help manage their germplasm. Data for this region were extracted from a GIS‐compatible global spatial climate dataset. Variables analyzed (based on long‐term monthly averages) included mean maximum and minimum monthly air temperatures, absolute maximum and minimum air temperatures based on each year's monthly data, mean monthly temperatures and precipitation, total precipitation, and mode of the elevations in the grid. The best grouping of similar regions resulted when cluster analysis on 7 mo of growing season data (April through October) was used to obtain 25 groups. The 25 groups were then classified into 10 maize ecologies corresponding to CIMMYT's mega‐environments. The ecologies included three lowland, three highland, two subtropical, and two transitional from subtropical to highland. The technique will be an important aid in classifying and using northern Latin America's large quantity of diverse maize germplasm.
Nitrogen Fertilization Timing Effect on Wheat Production, Nitrogen Uptake Efficiency, and Residual Soil Nitrogen
Authors: Alcoz Mercedes M. , Hons Frank M. , Haby Vincent A.
Published: July 2010

Split fertilizer N application has been proposed for improving N uptake efficiency in wheat (Triticum aestivum L.) production systems, but results have been inconsistent. In this field study, 75 and 150 kg N ha−1 was applied either all preplant or in two, three, or four split applications based on wheat growth stage (GS) to determine N timing effect on wheat yield and apparent fertilizer N recovery. Vegetative samples were also collected at Feekes GS 4, 6, and 10 to determine treatment effects on tissue N concentration during the growing season. Soil samples were collected after harvest to evaluate residual N quantity and movement in soil relative to N rate and time of application. The soil used was a Fluventic Ustochrept‐Udic Chromustert intergrade. Nitrogen rate and application timing appeared to have less effect than year on yield and N parameters. Significant grain yield increases were achieved with split applications of N fertilizer when N was topdressed at GS 4 or 6 in 1989 as compared with all preplant or application at GS 10. Split N application at GS 10 produced greater grain yield than application at GS 4 or 6 in 1990. Nitrogen uptake efficiency was greatest with 75 kg N ha−1 and split application. Soil NO‐3–N concentration was significantly higher at 150 kg N ha−1 than at 75 kg N ha−1. Significantly lower residual NO‐3‐N with the preplant treatment was not accounted for by greater grain or straw N content.
Accounting for Spatial Yield Variability in Field Experiments Increases Statistical Power
Authors: Scharf Peter C. , Alley Marcus M.
Published: July 2010

Parametric statistical techniques evaluate treatment significance in field experiments by comparing variability attributed to treatments to variability attributed to random error. In many experiments, a considerable amount of the variability attributed to random error is actually due to large‐scale soil variability that cannot be accounted for by blocking. This variability can, in part, be accounted for by a technique called nearest neighbor analysis, thus reducing the amount of variability attributed to random error; variability attributed to treatments is then larger in comparison, and the statistical significance of treatment effects is increased. Our objective was to evaluate the utility of nearest neighbor analysis in the statistical analysis of a set of field experiments. Four experiments with fall N treatments on winter wheat (Triticum aestivum L.) were analyzed using analysis of variance (ANOVA). According to this analysis, treatment had no significant effect on yield in any of the four experiments. After nearest neighbor analysis was used to remove spatial yield variability from the random error term, ANOVA revealed statistically significant treatment effects in two of the four experiments. Accounting for spatial variability is a practical way to increase the power of ANOVA and accompanying means‐separation techniques when analyzing data from replicated field plot experiments.
Row Spacing and Nitrogen: Effect on Alfalfa‐Bermudagrass Yield and Botanical Composition
Authors: Stringer William C. , Khalilian Ahmad , Undersander Daniel J. , Stapleton Gregory S. , Bridges William C.
Published: July 2010

Interseeding perennial legumes into bermudagrass [Cynodon dactylon (L.) Pers.] sods should increase forage quality. Preliminary research revealed that alfalfa (Medicago sativa L.) interseeded into bermudagrass (BG) rapidly reduced BG vigor, possibly because of shading by alfalfa. Grass—legume pastures should contain balanced mixtures for quality maintenance and bloat prevention. It may be possible to manipulate botanical composition with N and row spacing. The objective of this research was to examine effects of these factors on botanical composition and yield of alfalfa‐BG swards. We interseeded alfalfa into ‘Tifton 44’ BG in 20‐, 40‐, and 60‐cm row spacings, and included a non‐interseeded check treatment. Experiments were on Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult) and Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) sites. Nitrogen was applied at 0, 112, 224, and 448 kg ha−1 yr−1. Yield of BG increased by a factor of 2.06 with 448 kg ha−1 of N, compared with 0 N. Alfalfa increased total yields over BG alone, at all but the highest rates of N. Nitrogen increased yields of interseeded plots an average of 11%. Yield increases from N did not result from increased grass percentage. Increasing row spacing decreased yields of interseeded mixtures, but increasing N rate sometimes compensated slightly for wide rows. Nitrogen had no effect or decreased grass percentage, whereas wide row spacing usually increased the grass component. It appears that alfalfa utilized a significant portion of applied N, and that N will not aid in retaining BG in mixtures. Increasing row spacing will aid in retaining grass in mixture, probably through reduced shading of grass.
Rotation and Nitrogen Fertilization Effects on Changes in Soil Carbon and Nitrogen
Authors: Varvel Gary E.
Published: July 2010

Long‐term effects of cropping systems on soil properties, such as organic soil C and N levels, is necessary so more accurate projections can be made regarding the sequester and emission of CO2 by agricultural soils. This information can then be used to predict the effects of cropping systems on both soil degradation, maintenance, or improvement and global climate changes. My objective was to evaluate the effects of crop rotation and N fertilizer management on changes in total soil C and N concentrations that have occurred during an 8‐yr period in a long‐term study in the Western Corn Belt. Seven cropping systems (three monoculture, two 2‐yr, and two 4‐yr rotations) with three rates of N fertilizer were compared. Monocultures included continuous corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and grain sorghum [Sorghum bicolor (L.) Moench]. The 2‐yr rotations were corn‐soybean and grain sorghum‐soybean, and the two 4‐yr rotations were corn‐oat (Avena sativa L.) + clover (80% Melilotus officinalis Lam. and 20% Trifolium pratense). grain sorghum‐soybean and corn‐soybean‐grain sorghum‐oat+clover. Soil samples were taken in the spring both in 1984 and 1992 to a depth of 30 cm in 0‐ to 7.5‐cm, 7.5‐ to 15‐cm, and 15‐to 30‐cm increments. No differences were obtained in 1984, but both rotation and N rate significantly affected total soil C and N concentrations in 1992. The results indicate that C could be sequestered at 10 to 20 g m−2 yr−1 in some cropping systems with sufficient levels of N fertilizer. Greater storage of C in soils suggests CO2 emissions from agricultural soils could be decreased with improved management practices and may in the long term have a significant effect on CO2 in the atmosphere under current climate conditions.
CropSyst: A Collection of Object‐Oriented Simulation Models of Agricultural Systems
Authors: Van Evert F. K. , Campbell G. S.
Published: July 2010

Simulation of whole agricultural systems is now widely used in agronomy. Construction and maintenance of the large simulation models required for agricultural systems may benefit from the application of modern programming methods. In particular, object‐oriented programming (OOP) methods claim several advantages over conventional procedural methods. We sought a programming approach that would allow (i) interchanging of component models within and between whole‐system models, (ii) incremental model building without rewriting existing code, (iii) maintenance of more than one model of a component, and (iv) construction of a user‐friendly interface from which all parameters can be assigned and component models run. Here we report results of an experiment in which we used OOP to construct a cropping system model called CropSyst. An OOP analysis of cropping systems led to the abstraction of component systems (objects) with minimal and well‐defined interfaces. Examples of components, or objects, used in CropSyst are Time, Weather, Crop, Soil, Crop residue, Tillage, Erosion, Aphid population, Aphid immigration, Pesticide application, Planting, Crop rotation, and Output. Different versions of CropSyst were implemented and used to simulate production and erosion for cropping systems in eastern Washington, and to simulate yield loss and pesticide dynamics associated with Russian Wheat Aphid infestation. These were constructed from existing objects. Different versions of the Crop object simulated the different crops in a rotation cycle. Parameters were assigned and models were run from a commercially supplied user interface, which was also programmed using OOP. We were able to meet our objectives using OOP, and found it useful for construction and maintenance of agricultural systems models.
Corn Leaf Area Response to Early‐Season Soil Temperature under Crop Residues
Authors: Fortin M. ‐C. , Pierce F. J. , Edwards M.
Published: July 2010

Residue cover from conservation tillage modifies the soil temperature regime, compared with conventional tillage. This study was conducted to examine the influence of crop residue on the area of corn (Zea mays L.) leaves developed when the apical meristem is below the soil surface. Field studies compared the effects of residue‐covered and bare soil (Conover loam in East Lansing MI in 1988 and Brookston clay in Woodlsee, ON, in 1990), on maximum area per leaf (LAmax) at V6 and on leaf area index (LAI) after silking. LAmax for Leaves 4 to 6 was 11 to 52% higher in plants grown in residue‐covered soil than in bare soil. LAI after silking was similar in both treatments. LAmax differences could not be related to differences in volumetric water content or N concentration. Thermal effects of crop residue on LAmax and leaf appearance rates were tested in growth chamber. After emergence, the corn apical meristem was exposed to air. Nighttime air temperatures were maintained at 16°C and daytime air temperatures were controlled at 18, 21, and 25°C, simulating seed zone temperatures measured in the field. Daytime air temperatures of 21°C resulted in higher LAmax for Leaves 4 to 6 on V6 plants than did 18 or 25°C. Appearance rates increased with temperature. These results suggest that seed zone temperature under residue from emergence to V6 (≈23°C) was more favorable for LAmax than seed zone temperature under bare soil (≈26°C). Thus, for corn Leaves 4 to 6 the temperature optimum for LAmax is lower than the temperature optimum for leaf development.