bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seed Rate and Row Spacing of No‐Till Winter Wheat
Authors: Tompkins D. K. , Hultgreen G. E. , Wright A. T. , Fowler D. B. 
Published: July 2010

AbstractA snow management system, which utilizes no‐till seeding into standing stubble immediately after harvest of the previous crop, has permitted the expansion of winter wheat (Triticum aestivum L.) production in western Canada. The effect of seed rate and row spacing on grain yield and yield components of no‐till winter wheat were evaluated in 21 trials conducted in Saskatchewan from 1986 to 1988. Two winter wheat cultivars were evaluated in eight of the trials. The relationship between grain yield (Y) and seed rate was best described by a modified inverse polynomial: Y = uSR(1‐SR/566)/(SR + u/104) where u represents the upper limit of yield when seed rate is not limiting. This curve accounted for 98% of the observed variation in grain yield. Optimum seed rate varied from 58 kg ha−1 at a very dry trial to 148 kg ha−1 in a trial with more favorable growing conditions. Grain yield increased as row spacing decreased and the effect of row spacing on pain yield was increased under more favorable growing conditions. Increased seed rate and decreased row spacing interacted positively to increase grain yield so optimum seed rate increased as row spacing decreased. Increased spikes per square meter was responsible for the increase in grain yield associated with high seed rate and narrow row spacing. In contrast, kernel weights were slightly higher with low seed rate and kernels per spike were higher with low seed rate and wide row spacing. Optimum seed rate was higher for the cultivar ‘Norstar’ than for ‘Norwin’ due to higher yield potential of Norstar under the conditions experienced in this study.
Soybean Dry Matter Allocation under Subambient and Superambient Levels of Carbon Dioxide
Authors: Allen L. H. , Bisbal E. C. , Boote K. J. , Jones P. H. 
Published: July 2010

AbstractRising atmospheric carbon dioxide concentration [CO2] is expected to cause increases in crop growth and yield. The objective of this study was to investigate effects of subambient, as well as superambient, [CO2] on soybean [Glycine max (L.) Merr.] dry matter production and allocation for two reasons: to assess response of plants to prehistoric as well as future expected CO2 levels and to increase confidence in [CO2] response curves by imposing a wide range of [CO2] treatments. Soybean was grown in outdoor, sunlit, controlled‐environment chambers at CO2 levels of 160, 220, 280, 330, 660, and 990 µmol (CO2) mol−1 (air). Total dry matter growth rates during the linear phase of vegetative growth were 5.0, 8.4, 10.9, 12.5, 18.2, and 20.7 g m−2 d−1 for the above respective [CO2]. Samples taken from 24 to 94 d after planting showed that the percentage of total plant mass in leaf trifoliolates decreased with increasing [CO2] whereas the percentage in structural components (petioles and stems) increased. At final harvest the respective [CO2] treatments resulted in 38, 53, 62, 100, 120, and 92% seed yield with respect to the 330 µmol mol−1 treatment. Total dry weight responses were similar. Late season spider mite damage of the 990 and 280 µmol mol−1 treatments reduced yields. These data confirm not only that rising CO2 should increase plant growth, but also that plant growth was probably seriously limited by atmospheric [CO2] in preindustrial revolution times back to the previous global glaciation.
Propagation of Hybrid Bermudagrasses from Harvested Culms
Authors: Greene B. B. , Lancaster D. M. , Pee K. C. , Turpin J. M. , Eichhorn M. M. 
Published: July 2010

AbstractProduction of hybrid bermudagrass [Cynodon dactylon (L.) Pers.] requires stand establishment by vegetative means. Sprigs (rhizomes and rooted stolons) are the method of choice, but vegetative culms (cuttings) are often used because of lower planting material costs. Two studies, one in raised beds in a greenhouse (1987 and 1989) and one under field conditions (1989), were conducted during the summers of those years to investigate differences in survival of cuttings from four hybrid bermudagrass cultivars at 2, 4, 6, 8, and 10 wk of age. In raised beds, percent survival of Coastal (49%) was higher than Grazer (31%) and Tifton‐44 (24%); Brazos (41%) was higher than Tifton‐44. Cutting length and number of nodes were related to survival and reduced the proportion of variation in percent survival attributable to cutting age when included in analysis of variance models as covariates. Grazer and Brazos had higher survival than Coastal and Tifton‐44 after adjusting data for cutting length. A cultivar‐×‐age interaction affected survival in the field study. All the above results were significant at P < 0.05. Analysis of data by cultivar resulted in significant effects of age on survival of Brazos clippings, and no effect (P > 0.05) of age on survival of other cultivars.
Management and Dynamics of Potassium in a Humid Tropical Ultisol under a Rice‐Cowpea Rotation
Authors: Cox F. R. , Uribe E. 
Published: July 2010

AbstractLittle is known about the role of K fertilization, stover management, and tillage methods on soil K availability as they affect rice (Oryza sativa L.) and cowpea [Vigina unguiculata (L.) Walp.] productivity on Ultisols of the humid tropics. The effects of five K rates (0‐120 kg K ha−1), returning or removing stover, and three tillage methods (no‐till, strip, and conventional) were evaluated during 12 crops of rice and cowpea grown for a 4‐yr period. Fertilizer K was applied to the first seven crops. The site was a recently cleared, 18‐yr‐old secondary forest in the Peruvian Amazon Basin. The soil was a fine‐loamy, siliceous, isohyperthermic Typic Paleudult. Soils samples were collected at each crop harvest to 90 em in 15‐cm increments. Potassium fertilizer always increased grain yields when stover was removed. Conversely, responses to K additions were seldom obtained when the stover was returned. The extractable K (Modified Olsen) critical level for both upland rice and cowpeas was calculated to be 0.10 cmol L−1. Returning stover with no K fertilization maintained soil K concentrations above critical levels for both species up to the last crop of the rotation. Residual effects of fertilizer K were prolonged by returning the stover. When stover was returned, subsoil exchangeable K increased with increasing rate of K fertilization. Removal of stover resulted in greater increases in subsoil exchangeable K at the 40 kg K ha−1 rate than at 120 kg K ha−1, apparently because the higher rate resulted in K fixation. Tillage methods did not affect crop yields.
Comparison of Methods for Determining Critical Concentrations of Soil Test Phosphorus for Corn
Authors: Mallarino A. P. , Blackmer A. M. 
Published: July 2010

AbstractCritical concentrations of soil‐test P (STP) are used to identify soils where response to P fertilization should be expected. There is, however, little agreement concerning the methods that should be used to identify critical STP concentrations. This study compares the efficacy of critical STP concentrations generated by using various methods. Twenty‐five P fertilization trials with corn (Zea mays L.) were established in Iowa. Available soil P at each site was estimated by the Bray‐P1, Mehlich‐3, and Olsen extractants. Corn yield response was expressed in both absolute and relative terms and then related to STP values by using various statistical models (Cate‐Nelson split, linearplateau and quadratic‐plateau segmented polynomials, the quadratic polynomial, an exponential Mitscherlich‐type equation, and a multivariate polynomial). The use of various combinations of the extractants, expressions of yield response, and models resulted in a wide variety of critical STP concentrations. Comparisons of the ability of each critical concentration to generate economic returns when used to guide fertilization across the 25 sites showed that selection of the model was much more important than selection of the extractant or the expression of yield response. The best model was the Cate‐Nelson, which identified critical concentrations of 13 rag kg−1 for the Bray‐P1, 12 mg kg−1 for the Mehlich‐3, and 5 mg kg−1 for the Olsen extractants. Overall, the results of this study demonstrate that selection of the most appropriate critical STP concentration can be a major factor affecting the profitability of fertilization in areas having an abundance of soils testing high in P.
Crimson Clover Management to Enhance Reseeding and No‐Till Corn Grain Production
Authors: Ranells N. N. , Wagger M. G. 
Published: July 2010

AbstractEconomic savings and increased legume‐N use efficiency may result from natural reseeding of winter annual legume cover crops. A 3‐yr experiment was conducted on a Cecil fine sandy loam (clayey, kaolinitic, thermic Typic Kanhapludult) to examine the effects of crimson clover (Trifolium incarnatum L.) strip desiccation width (25, 50, and 75% of row area) and orientation (parallel or perpendicular to plant row) on soil water depletion, corn (Zea mays L.) growth and grain yield, and clover reseeding. Additional treatments included early desiccation (25% parallel strip 2 wk before corn planting), annual seeding (complete desiccation at corn planting), and mechanical disruption of clover growth by the no‐tillage planter. Early‐season soil water was lower in annual seeded plots compared to the 25% strip treatments each year, however, soil water was limiting in only one of 3 yr. Crimson clover successfully reseeded in all strip treatments each year, with dry matter production ranging from 3.0 to 5.2 Mg ha−1 in 1990 and from 3.9 to 5.2 Mg ha−1 in 1991. Nitrogen content of reseeded crimson clover biomass ranged from 86 to 134 kg ha−1 in 1990 and 93 to 111 kg ha−1 in 1991. Corn grain yield was only marginally affected by clover strip management in two out of 3 yr. Results suggest that under adequate moisture conditions a 50% desiccated strip has the potential to maximize clover N contribution. However, a 75% strip‐width can minimize potential competition with corn for water and reduce physical impedance of the clover cover crop on corn growth.
Fallow and Sesbania Effects on Soil Nitrogen Dynamics in Lowland Rice‐Based Cropping Systems
Authors: Buresh R. J. , Chua T. T. , Castillo E. G. , Liboon S. P. , Garrity D. P. 
Published: July 2010

AbstractVast areas of rice‐growing (Oryza sativa L.) lowlands in Asia are fallowed or cropped with non‐rice crops for part of the year. Nitrate can accumulate during the fallow or non‐rice crop, but this nitrate can be lost upon flooding for rice production. To determine fallow and green manure crop effects on soil nitrate and ammonium dynamics in lowland riceland, a 2‐yr field study was conducted in the Philippines. Treatments before wet season rice were (i) Sesbania rostrata grown for either 45 or 60 d, (ii) weedy fallow, and (iii) weed‐free fallow. Sesbania rostrata was sown with irrigation in late April‐early May, rains started in early (1989) or mid‐May (1990). Weeds and S. rostrata were incorporated after soil flooding on 23 June. Rains increased soil water‐filled pore space to above 0.75 mL mL−1 between mid‐May and soil flooding. Weeds and S. rostrata assimilated soil nitrate, as evidenced by lower (P < 0.05) nitrate in those treatments than in the weed‐free fallow. The decrease in soil nitrate in the weedfree fallow from 24 April to before soil flooding (15 kg N ha−1) was apparently due to denitrification or leaching; additional nitrate (19 kg N ha−1 in 1990) disappeared after soil flooding. Ammonium‐N was rapidly released from incorporated weeds and S. rostrata. It reached a maximum by 36 d after incorporation, which correlated (r = 0.95) with N accumulation by rice at 45 d after transplanting. Results suggest that weeds and crops before rice can reduce soil N loss by assimilating nitrate‐N and then cycling this N through incorporated plant residues back to the soil where it is rapidly mineralized and used by rice.
Soybean Stover Nitrogen Affected by Dinitrogen Fixation and Cultivar
Authors: Ravuri V. , Hume D. J. 
Published: July 2010

AbstractGrain legumes often are credited with leaving residual N for crops that follow in the rotation. This study was conducted to determine if increasing N2 fixation in soybean [Glycine max (L.) Merr.] would result in higher amounts of stover N at harvest. Eleven early‐maturing cultivars (Maturity group 00 and 0) in 1988 and 16 in 1989 were grown with five inoculant strain treatments and alone as uninoculated controls. There were slight cultivar‐by‐inoculant interactions but main effects were much larger. The order of N2 fixation with inoculant treatments, measured by the difference method, was 532C or three‐strain mixture > USDA 110 > CB 1809 > HH303. Dinitrogen fixation ranged from 60 to 125 kg ha−1 in 1988 and from 31 to 84 in 1989. Higher N2 fixation caused related significant (P ≤ 0.05) increases in stover dry matter and stover N yields in both years, despite concomitant increases in the apparent harvest index (AHI) and apparent NHI. Stover N concentration was not affected by increased N2 fixation in either year. In 1988, cultivars differed only slightly in stover N content. In 1989, amounts of stover N in different cultivars depended on how completely N was translocated to seed. Over the 2 yr, amounts of N in harvestable stover of the early‐maturing cultivars ranged from 9 to 24 kg ha−1, averaged across inoculant treatments. Although stover N increased with N2 fixation in both years, the amount of stover N available for return to the soil was quite low.
Nitrification Inhibitor Influences on Potato
Authors: Martin H. W. , Graetz D. A. , Locascio S. J. , Hensel D. R. 
Published: July 2010

AbstractNitrification inhibitors may reduce loss of fertilizer N from the root zone by reducing leaching and denitrification. This reduced N loss should be reflected in increased crop yields. These studies were conducted to determine if potato yield, specific gravity, or leaf N at flowering would be increased by use of nitrification inhibitors. Nitrification inhibitors dicyandiamide (DCD) and 2‐chloro‐6‐(trichloromethyl)‐ pyridine (nitrapyrin) were evaluated in five studies on potato (Solanum tuberosum L. cv. Atlantic) in Northeast Florida on an Arenic Ochraqualf, a Grossarenic Paleudult, and a Grossarenic Paleaquult. Treatments were combinations of N at 67, 134, and 202 kg ha−1; DCD at 0, 5.6, and 11.2 kg ha−1; nitrapyrin at 0.56 and 1.12 kg ha−l; and isobutylidene diurea (IBDU) applied as one‐third of the N. Tuber yields were not affected by nitrification inhibitors in four of five tests but were increased 14% in one test. Nitrification inhibitors increased leaf N concentration at flowering in three of four tests. Tuber yields were higher with DCD than with nitrapyrin in three of five tests. In several year‐location combinations, use of IBDU resulted in greater tuber yield and leaf N concentration at flowering than did nitrification inhibitors. Based on these results, nitrification inhibitors can not be recommended for potato production on hyperthermic, sandy, irrigated soils.
Early Season Ethephon Application Effects on Cotton Photosynthesis
Authors: Pettigrew W. T. , Heitholt J. J. , Meredith W. R. 
Published: July 2010

AbstractCotton (Gossypium hirsutum L.) can compensate for a limited amount of early floral bud (square) loss induced by early ethephon ethephon [(2‐chloroethyl)phosphonic acid] application, but ethephon has been found to alter the photosynthetic process in many species. A field study was conducted in 1989 and 1990 to determine how early season ethephon application affected cotton photosynthesis throughout the growing season. Early season squares were removed by hand or induced to abscise with a spray application of 0.28 kg ha−1 ethephon. Dry matter harvests were collected and light‐saturated leaf CO2 exchange rates (CER) measured periodically throughout both growing seasons. Concentrations of leaf chlorophyll, soluble protein, ribulose‐1,5‐bisphosphate carboxylase‐oxygenase (Rubisco), and thylakoid proteins CP1 and light harvesting complex along with the specific leaf weights were periodically determined on leaves tested for CER. The net assimilation rate was 13 to 17% lower in the ethephon‐treated plots directly after treatment application in both years. In 1990, leaf CER was 15% lower in the ethephon‐treated plants than either the check or hand‐removal treatments 2 d after treatment application, but was 5% greater than the two other treatments 13 d later. Stomatal conductance of the ethephon‐treated plants was 23% lower during the period of lower CER and net assimilation rate, but the internal CO2 concentration was unchanged, suggesting depressed photosynthetic activity in the chloroplasts, in addition to stomatal closure. Other than the 1‐ to 2‐wk period after treatment application, CER was unaffected by treatments. Perhaps superior carbohydrate partitioning or remobilization is more important than elevated photosynthesis in compensating for early square loss.
Spring Nitrogen on Winter Wheat: II. A Flexible Multicomponent Rate Recommendation System
Authors: Scharf Peter C. , Alley Marcus M. 
Published: July 2010

AbstractA recently developed system to predict the optimum N fertilizer rate for winter wheat (Triticum aestivum L. emend. Theil) at Zadoks growth stage (GS) 30 is based on the relationship between measured economic optimum N rate at GS 30 and wheat tissue N content measured at GS 30. However, winter wheat often needs an earlier application of spring N to achieve optimum yield. We therefore developed a test to determine which fields need this earlier (GS 25) application, and to predict the optimum N rate with split‐application management using the tissue test or as a single spring application. The optimum N rate at GS 25 was measured over 5 yr, both with and without GS 30 N applications. These measured optimum N rates were regressed against a variety of possible predictor variables measured in the same fields. Tiller density at GS 25 was a good predictor of optimum N rate at GS 25 in a split spring application program. Using this relationship along with the GS 30 tissue test to make N recommendations for winter wheat increased estimated profit relative to using the tissue test alone. Soil NO3 measured to 0.9 m depth was the best predictor of optimum N rate at GS 25 when that is to be the only spring N application, and improved estimated profit relative to applying 90 kg N ha−1 at all sites; however, the economic performance of split spring N applications was substantially better than for any single spring applications. The recommendation system developed by integrating these component relationships is powerful and flexible, and provides field‐specific N rate recommendations for all spring N applications to winter wheat, regardless of management decisions about splitting spring N applications.
Defoliation Effects on Seasonal Production and Growth Rate of Cool‐Season Grasses
Authors: Belesky David P. , Fedders James M. 
Published: July 2010

AbstractKnowledge of seasonal distribution of herbage growth is essential for design of pasture management schemes that optimize season‐long herbage productivity and nutrients for grazing livestock. Current knowledge of cool‐season grass growth is derived largely from either hay production or high‐input systems. A 3‐yr field study was conducted to determine the productivity and growth rates of cool‐season grasses defoliated according to sward height criteria in a marginal soil environment. Defoliation regimes included hay harvest, lenient (50%) removal of short (10 cm) canopies, and both lenient and intensive (75%) removal of tall (20 cm) canopies. Species included orchardgrass (Dactylis glomerata L.), fescue × perennial ryegrass hybrid (Festuca arundinacea Schreb. × Lolium perenne L.), and prairie grass (Bromus willdenowii Kunth). Cumulative yield curves were fit to the Gompertz growth equation and growth rates were derived from the fitted data. All species had low yields relative to other defoliations and growth rates when managed for removal of 50% of canopy height regardless of height. Managing pastures on the premise of take half, leave half may not always contribute to plant persistence and sustained productivity. Frequent defoliation beginning in spring resulted in a greater portion of annual yield occurring in late than in early season, resulting in more stable distribution but less herbage within a season, compared with canopies managed as hay. High growth rates of prairie grass early in the study were followed by stand degradation, regardless of defoliation treatment, and may indicate unsuitability for use in low‐input or marginal environments. Autumn recovery of herbage production did not occur under any defoliation regime.
Photosynthate Reserves during Grain Filling in Winter Wheat
Authors: Gent Martin P. N. 
Published: July 2010

AbstractHow much does stored or reserve photosynthate contribute to grain growth in winter wheat (Triticum aestivum L.)? Three models were developed to assess this contribution. In Model I, all current photosynthate was used for vegetative or reproductive growth, and there was no reserve. In Model II, photosynthate accumulated in a reserve was used preferentially to support maintenance respiration, while current photosynthate accumulated in the grain. In Model III, the maintenance component extracted from the reserve was continuously replenished from current photosynthate, thus requiring a greater contribution from the reserve for dry matter in the grain. Each model related dry matter accumulation at the whole‐plant level to photosynthesis, respiration, and the distribution and retention of 14C from 14CO2 assimilated photosynthetically. To test the models, these characteristics were measured in four cultivars of New York soft white winter wheat grown in the field in Connecticut in three years. Observations showed that canopy respiration and grain dry matter accumulation were approximately equal sinks for photosynthate and, together, were greater than canopy photosynthesis late in grain filling. Consequently, in two years, Model I (with no reserve) terminated grain filling early and predicted a lower harvest index than was observed. The observed time course of the distribution and retention of radioactivity from a pulse of 14C02 assimilated photosynthetically was most consistent with predictions of Model III (continuous replenishment of the reserve). In this model, preanthesis reserves contributed from 0.2 to 0.5 of grain dry weight of winter wheat in Connecticut, depending on harvest index. This contribution is expected to exceed 0.5 in more stressful climates.
Cereal Grain Yield: Biblical Aspirations and Modern Experience in the Middle East
Authors: Amir J. , Sinclair T. R. 
Published: July 2010

AbstractVery little information exists on crop yields in antiquity. Examination of some of the earliest yield records may give some insight about crop productivity among ancient peoples and a historical perspective on the progress achieved in modern agronomic practices. The Book of Genesis contains one of the earliest recorded expressions of a concern for the yielding potential of cultivated crops. In this paper, we translate the ambiguous biblical reference to crop yield into a modern expression of crop yield per unit land area. Because the yield aspirations of these ancient people are equivalent to modern yields achieved under rainfed conditions at the same location, we undertook an analysis of the agronomic practices used by these ancient people to determine the likelihood that such yields could be achieved. In fact, it appears possible that maximum cereal yields in the ancient Middle East could have approximated modern yields. This analysis may highlight the great advances in modern agriculture to bring high crop yields to large land areas by overcoming various stresses, but the inherent physiological yielding potential may not have been substantially altered over the millennia.