bluuebunny/crossref_metadata_2025 huggingface dataset:
Management of Tropical Legume Cover Crops in the Bolivian Amazon to Sustain Crop Yields and Soil Productivity
Authors: Luna‐Orea Pedro , Wagger Michael G.
Published: July 2010

The trend to shorter natural fallow periods in shifting agriculture calls for management alternatives to accelerate nutrient accumulation and aid in weed control. Substituting cover crop‐based managed fallows is one possibility. Our objectives were to (i) quantify nutrient accumulation by three tropical legumes [Canavalia ensiformis (L.) DC.; Desmodium adscendens (Sw.) DC.; and tropical kudzu, Pueraria phaseoloides (Roxb.) Benth.] grown as managed fallows for 12 and 18 mo, (ii) evaluate the effect of residue management (burning vs. not burning) on the efficient use of nutrients by the subsequent rotational crops rice‐cowpea‐rice [Oryza sativa L.‐Vigna unguiculata (L.) Walp.‐O. sativa], and (iii) determine the effect of commercial fertilizer on maintaining crop yields. The study was conducted at two sites (Typic and Aquic Dystropepts) in the Chapare region of Bolivia. Total aboveground nutrient contents of the cover crops, across sites and duration of managed fallow, ranged from 41 to 391 kg N ha−1, <1 to 27 kg P ha−1, 5 to 191 kg K ha−1, 3 to 136 kg Ca ha−1, and 7 to 47 kg Mg ha−1. Averaged across sites and residue management, grain yields for the first rice crop after a 12‐mo managed fallow were highest with pueraria (1.65 Mg ha−1), followed by canavalia (1.38 Mg ha−1) and desmodium (0.65 Mg ha−1). Slashing and burning resulted in a mean rice (1st crop) yield increase of 137% compared with slash only. Cowpea yield was less affected by treatment variables than rice, due perhaps to N2 fixation. For the last rice crop, there were no grain yield differences for any of the variables studied. Nutrient uptake differences were most evident with the first rice crop, and were influenced primarily by residue management. Compared with slash only, and averaged across sites for the first rice crop, slashing and burning fostered a whole‐plant increase of approximately 18 kg N ha−1, 3 kg P ha−1, 24 kg K ha−1, 4 kg Ca ha−1, and 3 kg Mg ha−1. Soil chemical properties were only marginally affected by any variable. Shorter fallow periods with legume cover crops can produce adequate yields of annual crops. Longer cropping periods than we used are likely to require lime and fertilizer to sustain crop production.
Turfgrass Quality, Growth, and Water Use Influenced by Salinity and Water Stress
Authors: Dean Dorothy E. , Devitt Dale A. , Verchick Linda S. , Morris Robert L.
Published: July 2010

Limited water resources in the arid southwestern USA have created greater interest on the part of municipalities to utilize nonpotable waters in urban areas. Research was conducted to assess the feasibility of using a perched saline aquifer as an alternative irrigation source for turfgrass. Two line‐source irrigation gradients, one using municipal water with an EC of ≈ 1.1 dS m−1 and the other using saline aquifer water blended with municipal water to an EC of 6.0 dS m−1, were established to impose a salinity and/or water deficit gradient on tall fescue (Festuca arundinacea Schreb. ‘Monarch’) and an improved common bermudagrass (Cynodon dactylon L. ‘Numex Sahara’). Yield was found to be highly correlated with actual evapotranspiration (ETa) (r = 0.92, P < 0.001 for bermudagrass; r = 0.83, P < 0.001 for tall fescue), regardless of how the stress was imposed. Relative ETa (ratio of ETa to maximum ETa under municipal irrigation) values as a function of the summation of the leaf‐to‐air temperature differences also indicated no distinguishable change in stress response based on water quality (r = 0.94, P < 0.001 for tall fescue; r = 0.86, P <0.001 for bermudagrass). Relative turf color and percent cover remained unchanged if the ratio of irrigation volume to potential evapotranspiration (I/ETo) remained above species‐specific threshold values of 0.80 for tall fescue and 0.65 for bermudagrass. Below these thresholds, cover and color declined linearly, with differences due to water quality treatment in tall fescue but with no differences due to water quality treatment in bermudagrass.
Genotype of Wheat and Barley Affects Light Penetration and Wild Oat Growth
Authors: Lanning Susan P. , Talbert Luther E. , Martin John M. , Blake Thomas K. , Bruckner Philip L.
Published: July 2010

Cereal breeders have selected for traits that confer resistance to diseases and insects, with the goal of stabilizing yield potential and reducing inputs. The possibility exists that, by selecting for growth habits that impede weed development, cultivars can be developed with increased tolerance to weed infestations. Our objective was to determine whether wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) lines differ in their ability to prevent penetration of light into interrow spaces and suppress wild oat (Avena fatua L.) growth. Based on our results, significant genotypic variation exists within winter and spring wheat and spring barley for the amount of sunlight allowed to penetrate to interrow spaces. A negative correlation existed between height and light penetration in four of seven nurseries studied. Six barley lines and six spring wheat lines, of similar heights but allowing different amounts of light penetration, were tested for suppression of wild oat growth. Barley was a much better competitor with wild oat than wheat was, allowing approximately one‐half the wild oat biomass and seed production. Barley lines allowed approximately 43% less light penetration than wheat. Significant variation for wild oat growth variables also existed among lines within the crops. High positive correlations of light penetration with wild oat growth existed within barley, suggesting that lines may be selected to contribute to integrated wild oat management.
Superiority of Winter Sowing over Traditional Spring Sowing of Chickpea in the Mediterranean Region
Authors: Singh Kharag B. , Malhotra Rajinder S. , Saxena Mohan C. , Bejiga Geletu
Published: July 2010

Chickpea (Cicer arietinum L.), when traditionally grown as a springsown crop in the Mediterranean region, often suffers from heat and moisture stress, resulting in low and unstable yields. In contrast, sowing the crop in winter with cultivars tolerant to cold and to ascochyta blight [caused by Phoma rabiei (Pass.) Khune & J.N. Kapoor; syn. Ascochyta rabiei (Pass.) Lab.] minimizes the effects of terminal heat and drought stress and increases and stabilizes productivity. Therefore, a study was conducted with the objective of assessing the comparative seed yield advantage of winter over spring sowing in Mediterranean environments. Nineteen to 23 ascochyta blight‐resistant and cold‐tolerant breeding lines were compared in winter and spring sowing for 10 yr (1983–1993) at three locations in Syria and Lebanon. The set of lines used in this study differed each year. Averaged over 10 yr, winter‐sown chickpea produced 70% (692 kg ha−1) more seed yield than the spring‐sown crop. The longer growing period of winter‐sown chickpea resulted in higher biomass production, which contributed mainly toward increased seed yield. The yield potential of lines sown during winter was approximately 4000 kg ha−1, and yields were more stable than in the spring‐sown crop. The correlation between seasonal rainfall and seed yield was positive and significant in both seasons. In 1988–1989, when the Tel Hadya site experienced severe drought, the springsown crop resulted in virtually no seed yield, whereas the winter‐sown crop produced an average yield of 542 kg ha−1 by a partial escape of the severe drought. Winter‐sown plants were taller than those in the spring sowing, permitting harvesting by combines. Because of these advantages, winter sowing of chickpea is gaining popularity in the Mediterranean region.
Factors Affecting Maize Forage Quality Development in the Northeastern USA
Authors: Crasta Oswald R. , Cox William J. , Cherney Jerome H.
Published: July 2010

Topographical features in the northeastern USA result in temperature and soil water differences between locations of close proximity. Dairy producers frequently inquire how these differences affect forage quality of maize (Zea mays L.). Field experiments were established in 1990 and 1991 at two locations and two planting dates to evaluate temperature and soil water effects on neutral‐detergent fiber (NDF), lignin, and in vitro dry matter digestibility (IVDMD). Whole‐plant IVDMD at harvest (R5 stage) had correlation coefficients (r) of −0.61 with NDF and −0.63 with lignin concentration at silking. Also, IVDMD had r = −0.90, −0.72, and 0.75 with NDF, lignin, and grain content, respectively, at the R5 stage. Stover lignin concentration and grain content explained 83% of the variability in whole‐plant IVDMD at the R5 stage. In the dry 1991 growing season, IVDMD was higher and fiber components were lower than in the wetter 1990 season. Locations, which had average temperature differences of 3.5°C from the eighth‐leaf (V8) to R5 stage, did not affect forage quality in 1990, but the cool location in 1991 had somewhat higher IVDMD and lower fiber components than the warm location. Nevertheless, regression analysis indicated that temperature did not contribute significantly to IVDMD variability and contributed only a small portion to NDF variability at harvest. In contrast, a calculated water deficit index value explained 74%o f the variability in IVDMD at early grain‐fill and 61% at harvest. Clearly, maize forage quality in this study was associated more with soil water differences than with temperature differences.
Environmental Adaptation of Long‐Juvenile Soybean Cultivars and Elite Strains
Authors: Tomkins Jeffrey P. , Shipe Emerson R.
Published: July 2010

A long‐juvenile (LJ) trait that delays flowering under short‐day conditions has been incorporated into adapted soybean [Glycine max (L.) Merr.] germplasm. Little is known about the performance of recently developed LJ cultivars and elite strains as influenced by planting systems typical of the southeastern USA. Therefore, a field study was undertaken using two LJ cultivars and four elite LJ Florida strains at Blackville and Pendleton, SC. Planting dates were early (late April), normal (late May), and late (late June), in 1993 and 1994. The LJ genotypes exhibited neither genotype × planting date nor genotype × location interactions for seed yield or seed quality, indicating consistency of genotype performance across environments. Although variation among LJ genotypes for yield was not detected, all four elite strains all ranked higher in yield than the two cultivars. Maturity varied among LJ genotypes but seed yield did not, indicating the possibility of developing LJ genotypes that have relatively short life cycles and high seed yield. Additionally, LJ genotypes were compared with two conventional cultivars: Maturity Groups (MG) IV, V, and VI at early plantings; MG V, VI, and VII at normal plantings; and MG VI, VII, and VIII at late plantings. As planting date was delayed, growth and agronomic responses of LJ genotypes became similar to those of successively later conventional cultivars. The LJ genotypes were similar in yield to conventional cultivars in maturity groups V to VIII across planting dates, but had 56% higher yields than MG IV cultivars at the early planting. Seed quality ratings of LJ genotypes were 54 and 23% better than MG IV and V cultivars, respectively, at the early planting. In general, LJ genotypes showed superior photoperiodic adaptation to different planting date environments.
Grazing Sheep and Cattle Together or Separately: Effect on Soils and Plants
Authors: Abaye Azenegashe O. , Allen Vivien G. , Fontenot Joseph P.
Published: July 2010

Differences in grazing behavior suggest opportunities to improve forage use when cattle and sheep graze in the same pasture, but a better understanding of their effect on soils and plants is needed. Angus cows (Bos taurus) with calves and ewes (Ovis aries) (1/2 Dorset, 1/4 Finn, 1/4 Rambouillet crossbred) with lambs grazed Kentucky bluegrass‐white clover (Poa pratensis L.‐Trifolium repens L.) pastures from spring until autumn in a study of the effects on soils and plants of grazing cattle and sheep together and separately. The experiment was a randomized block design with three replications conducted during 3 yr. There were 6 cow‐calf pairs per replication of cattle alone and 6 ewes with 11 lambs per replication of sheep alone. For the mixed‐grazed pastures, there were 6 cows plus 6 ewes, each with their respective offspring, per replication. Grazing sheep alone increased soil bulk density (1.47 vs. 1.38 g cm−3), extractable soil P (140 vs. 80 kg ha−1), and percentage bluegrass (36 vs. 25%), but decreased percentage white clover (3 vs. 10%) compared with grazing cattle alone. Grazing sheep and cattle together resulted in soil bulk density and extractable soil P of 1.45 g cm−3 and 115 kg ha−1, respectively. Grazing sheep and cattle together resulted in a higher B horizon soil pH (6.7 vs. 6.4 and 6.5) and percentage organic mater (1.9 vs. 1.5 and 1.7) than where cattle or sheep grazed alone, respectively. Percentage bluegrass and white clover present in the sward where both animal species grazed was 37 and 5%, and there were fewer forbs (12%; P < 0.08) than when cattle or sheep grazed alone (18 and 15%, respectively). Grazing both animal species together appeared to have beneficial effects on several botanical composition and soil characteristics over grazing cattle and sheep in separate pastures.
No‐Till Corn Response to Crop Rotation and In‐Row Residue Placement
Authors: Janovicek Ken J. , Vyn Tony J. , Voroney Robert P.
Published: July 2010

Enhanced corn (Zea mays L.) yield responses to rotation in no‐till systems may be due to the types and amounts of surface‐placed plant residue. Research in 1989, 1990, and 1995 evaluated no‐till corn yield response to various preceding crops and examined whether in‐row residue removal affected no‐till corn response to rotation crops. The soil was an imperfectly drained loam (medium, mixed, weakly to moderately calcareous Typic Hapludalf). The preceding crops were: corn harvested for grain or whole‐plant silage; hard red spring wheat (Triticum aestivum L.); barley (Hordeum vulgare L.); red clover (Trifolium pratense L.) cover crops, following barley, that were killed by spraying either 3 wk (early‐kill) or 1 d (late‐kill) prior to corn planting; canola (Brassica napus L.); and soybean [Glycine max (L.) Merr.]. In‐row residue was either retained while planting or cleared using planter‐mounted, notched‐disk row cleaners. Clearing in‐row cover crop residue increased early‐season corn growth and was associated with yield increases of 0.61 Mg ha−1 (8%) following early‐killed red clover and 0.43 Mg ha−1 (6%) (P = 0.10) following late‐killed red clover. In 2 of 3 yr, corn yields following early‐killed red clover were similar to following soybean and greater than following grain corn, provided that in‐row residue was cleared. Following the other crops, grain yield response to clearing in‐row residue was smaller and less consistent over years. Preceding cropping affected early‐season corn growth, with the largest plants at 5 wk after planting following either soybean or silage corn and the smallest following either red clover or grain corn. In 2 of 3 yr, when preceding crop effects on grain yield were statistically significant, yields following either soybean or spring wheat were more than 1.05 Mg ha−1 (16%) higher than after grain corn. That yield increase occurred regardless of in‐row residue placement. Removing corn stover by harvesting as silage increased corn yield by 0.86 Mg ha−1 (12%) over yield following grain corn. During 1995, corn yield following silage corn was less than after soybean, canola, barley, or wheat; thus, no‐till corn yield response to rotation is not exclusively due to the presence of surface‐placed stover. In‐row residue placement and preceding cropping practices affected in‐row soil temperature, but this could not totally account for the treatment effects on early‐season corn growth and yields.
A Computer Program for Geostatistical and Spatial Analysis of Crop Model Outputs
Authors: Thornton Philip K. , Booltink Harry W. G. , Stoorvogel Jetse J.
Published: July 2010

Well‐tested computer simulation models of the growth, development, and yield of annual crops are being used for a wide range of purposes, including the prediction of impacts of different management practices and land use systems on food production, farmers' profitability, and the environment. Presentation and interpretation of simulation results can be significantly enhanced through the linking of models with software that allows spatial visualization. Many users of crop simulation models, however, are located in institutions in developing countries where resources are particularly limited. Computer software to perform a variety of spatial analyses was written, which can be run on modest hardware without the need for costly third‐party software. The software is an integral part of the Decision Support System for Agrotechnology Transfer (DSSAT), a comprehensive crop simulation model and data system, but can also be run in a stand‐alone mode. Users can run spatial simulation experiments and then analyze the results using (i) a geostatistical module to interpolate maps and produce probability surfaces from a network of data points and (ii) a utility that calculates agronomic and economic output statistics from model simulations and maps the results as polygons. The suite of modules, which runs on an IBM‐compatible personal computer, interfaces with some widely used third‐party GIS software, and the mapping facility enables users to export and import images to a number of common file formats.
Ontogenetic Evaluation of Grain Yield and Time to Maturity in Barley
Authors: Dofing Stephen M.
Published: July 2010

High grain yield and early maturity are desirable characteristics in many regions in which barley (Hordeum vulgare L.) is grown. However, negative correlation between these traits makes their joint improvement difficult. Previous research quantifying the contribution of traits to grain yield has not included their effects on time to maturity, and often has not included important developmental traits related to time to maturity. The purpose of this research was to quantify the determination of grain yield and time to maturity in barley, using a model that included developmental traits such as leaf number, phyllochron, and grain fill rate. A genetically diverse group of 24 barley genotypes was grown for three years at Palmer, AK, and significant causal relationships determined using path analysis and stepwise regression. Longer vegetative periods (time to heading) resulted in higher grain yield, but longer heading‐to‐maturity periods had no effect on grain yield. Faster grain fill rate resulted in higher grain yield and shorter grain filling period. In environments similar to these, the competing objectives of high grain yield and acceptably early maturity were realized by cultivars with relatively long preheading periods and relatively short reproductive periods, without exceeding the critical level of early maturity required by growers. Longer preheading periods appear necessary to develop an adequate number of kernels per spike and sufficient number of leaves to provide photoassimilate during grain fill. These results provide breeders additional insights for decisions involving choice of germplasm and selection criteria in breeding programs.
Relating Sugar Fluxes during Bale Storage to Quality Changes in Alfalfa Hay
Authors: Coblentz Wayne K. , Fritz John O. , Bolsen Keith K. , Cochran Robert C. , Fu Lin‐qian
Published: July 2010

Negative quality changes that occur when alfalfa (Medicago sativa L.) is baled at moisture levels in excess of 200 g kg−1 have been well documented; however, relatively little is known about changes in nonstructural carbohydrate pools during bale storage and how these changes are involved in depression of forage quality. The objectives of this study were to quantify nonstructural carbohydrate pools at specific time periods during bale storage and to relate these findings to accumulated heating degree days and traditional quality indices. Alfalfa forage was field‐dried to high‐ and low‐moisture concentrations of 299 and 197 g kg−1, respectively, and packaged as conventional (CONV) and laboratory‐scale (LAB) bales. During the first 4 d of storage, reducing sugar concentrations appeared to increase in highmoisture conventional bales and high‐moisture laboratory bales made at twice the density of conventional bales (treatments that most favored spontaneous heating). Between 4 and 11 d in storage, reducing sugar concentrations for these treatments decreased sharply and continued a gradual decline thereafter, effectively mirroring the concurrent increases in acid‐detergent insoluble N (ADIN). Nonreducing free sugar, total free sugar, and total nonstructural carbohydrate (TNC) concentrations declined rapidly during storage; these responses were linearly related to increases in heating degree days >30°C. For high‐moisture treatments, ADIN concentrations were strongly correlated with total free sugar and TNC levels (r = −0.90 and −0.90, respectively). Correlations between ADIN concentrations and reducing sugars (r ≤ −0.72) appeared weaker. At the low moisture level, reducing sugar concentration was not related (P ≥ 0.05) to ADIN concentration.
Symbiosis with Neotyphodium uncinatum Endophyte May Increase the Competitive Ability of Meadow Fescue
Authors: Malinowski D. , Leuchtmann A. , Schmidt D. , Nösberger J.
Published: July 2010

Infection with the endophyte Neotyphodium uncinatum (Gams, Petrini & Schmidt) Glenn, Bacon, Price & Hanlin may influence drought resistance and competitive ability of meadow fescue (Festuca pratensis Huds.). We determined endophyte‐related effects on some growth and physiological characteristics in one clone of meadow fescue. In a growth chamber experiment, meadow fescue and orchardgrass (Dactylis glomerata L.) were planted in pots as monocultures or binary mixtures, competing in the root systems. One group of plants was adequately watered to maintain the original pot weight (control). The other group was subjected to a gradually imposed water stress, defined as soil water deficit, during 25 d (stressed plants). After rewatering, plants were allowed to regrow for 3 wk. Endophyte infection increased shoot and root dry weight by 33 and 70%, respectively, in control meadow fescue plants, and by 24 and 69% in stressed plants. Infected (E +) plants had significantly greater competitive ability than noninfected (E−) plants when grown in E−/E+ binary mixture. In binary mixtures with orchardgrass, the competitive abilities of E− and E+ plants were reduced relative to that of E− and E+ plants grown as monocultures. In response to water stress, stomatal conductance was lower in E+ than in E− plants, regardless of root competition. Noninfected plants could not completely recover in leaf water potential when exposed to root competition with infected plants or orchardgrass. The greater competitive ability of E+ plants was related to improved root and shoot growth and enhanced drought resistance. Infection with N. uncinatum could confer a competitive advantage to the meadow fescue clone.
Recovering Information in Augmented Designs, Using SAS PROC GLM and PROC Mixed
Authors: Wolfinger Russell , Federer Walter T. , Cordero‐Brana Olga
Published: July 2010

The SAS GLM and MIXED procedures can be useful for experimenters desiring to analyze data from screening experiments using a member of the class of augmented experiment designs. Since application of the procedures is typically not straightforward for these designs, several programs of possible interest are described. We show how to recover interblocking and intervariety information when the blocking and varieties are random effects, how to arrange varietal responses in descending order, and a number of other options.
Tillage Effect on Soil Water Content and Corn Yield in a Strip Intercropping System
Authors: Ghaffarzadeh Mohammadreza , Préchac Fernando García , Cruse Richard M.
Published: July 2010

A three‐crop strip intercropping system including corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and oat (Avena sativa L.) interseeded with nondormant alfalfa (Medicago sativa L.), was established in south‐central Iowa on a poorly drained Haig soil (fine, smectitic, mesic Vertic Argiaquoll). In 1989 (a dry year) and 1990 (a wet year), we studied the effect of tillage treatment (conventional, CT; reduced, RT; and no‐till, NT) and row position on soil water content, canopy and air temperatures, corn grain yield, and yield components. No‐till resulted in the most favorable soil water status, plant water status, and grain yield in 1989. No‐till had the poorest performance in 1990, mainly because of excessive soil water. The opposite was true for conventional till in both years. Reduced till yield equaled that for the most productive tillage treatment in both years. Conventional and reduced tillage resulted in lower corn grain yield at the border with oat‐alfalfa than with soybean because oat depleted soil water more than soybean in both years. In contrast, for no‐till the corn grain yield at the border with oat‐alfalfa was 6% greater than corn yield bordering soybean in 1989 and 13% greater in 1990. When water was not limiting, in 1990, both corn borders outyielded the center rows by an average of 14% in NT, 27% in RT, and 28% in CT. Soil water content rankings throughout the 1989 season were NT > RT > CT and row position rankings were soybean border > center > oats‐alfalfa border. In 1990, there were no soil water content differences between tillage treatments and row positions. Reduced tillage is the most suitable soil management system for corn production with three‐crop strip intercropping on this soil, considering consistently high relative yields for both wet and dry years.
Influence of Seeding Rate on Big Bluestem Establishment with Herbicides
Authors: Masters Robert A.
Published: July 2010

Weeds interfere with establishment of big bluestem (Andropogon gerardii Vitman var. gerardii Vitman) on rangeland and cropland in the central Great Plains of North America. A study was conducted to determine the influence of seeding rate on establishment of big bluestem when metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] and atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] were applied alone or in combination. ‘Pawnee’ big bluestem was planted in late May to early June 1990 and 1991 near Clay Center and Mead, NE, at 110, 220, and 440 pure live seed (PLS) m−2. Metolachlor at 0, 2.2 or 3.3 kg a.i. ha−1 and atrazine at 2.2 kg a.i. ha−1 were applied alone or in combination before weeds or the seeded big bluestem emerged. Big bluestem stand frequency (the number of times the planted grasses occurred within sampling grids and expressed as a percentage of the total number of grids evaluated) and yield were measured the year after planting to determine establishment success. Big bluestem stand frequency and yield were influenced primarily by the main effects of herbicide and seeding rate. Grass stand frequencies usually increased with increasing seeding rate. Big bluestem stands were successfully established in three of the four environments evaluated when seeded at 110 PLS m−2, and in all environments when seeded at 220 or 440 PLS m−2. Big bluestem yields were at least 1.2 Mg ha−2 greater on areas treated with metolachlor than on areas not so treated at Clay Center in 1991 and 1992 and Mead in 1991. Atrazine increased big bluestem yields by 1.2 and 2.4 Mg ha−1 at Mead in 1991 and 1992, but had no effect on yields at Clay Center. Based on these findings, metolachlor and/or atrazine can be applied preemergence the year of planting to improve yield of big bluestem seeded at a rate as low as 110 PLS m−2.
Modeling Soybean Cultivar Development Rates, Using Field Data from the Mississippi Valley
Authors: Acock Basil , Pachepsky Yakov A. , Acock Mary C. , Reddy Vangimalla R. , Whisler Frank D.
Published: July 2010

To predict how crop yields of soybean [Glycine max (L.) Merr.] respond to management practices, we need a reliable understanding of how environmental factors affect ontogeny of the many soybean cultivars grown. The objective of this work was to use field observations to develop equations relating reproductive development to environmental variables for several cultivars grown commercially in the southern USA. We used data on five soybean cultivars, recorded during farm testing of the soybean crop model GLYCIM in 1993, 1994, and 1995. Crop development stages were determined by averaging the Fehr and Caviness development stages of individual plants. We inspected the data and found that it could be fitted using a piecewise linear regression with alternating horizontal and sloping segments. The progress in crop reproductive development stages was expressed as a function of time after emergence for the period before flowering, and as a function of thermal time for the period after flowering. Horizontal segments that occurred near R2, R5, and R6 were interpreted as developmental plateaus (i.e., a period when the crop remains at a given stage). The length of the R2 plateau was a function of date of emergence, and the length of the R6 plateau was a linear function of soil surface water balance. In our dataset, there was no effect of soil properties, irrigation, or plant population density on reproductive development. The technique developed in this study will facilitate the application of crop simulation models on farms by providing a way to develop a set of parameters for reproductive development for any cultivar being grown.
Accumulation of Dry Matter and Evolution of Nutritive Value in Serradella (Ornithopus sativus Brot.)
Authors: Lloveras Jaime , Iglesias Isabel
Published: July 2010

Development of efficient forage management and utilization is facilitated by knowledge of nutrititive value evolution and dry matter (DM) distribution patterns within plants. The objectives of this experiment were to determine the patterns of DM accumulation and the evolution of nutritive value from the vegetative stage to the ripe seed stage of serradella (Ornithopus sativus Brot.), a cool‐season annual forage legume adapted to acid soils. Serradella was established on a Dystric Eutrochrept soil with pH 5.4 in Mabegondo, northwestern Spain, for three consecutive years (1990–1992). Shoot samples were taken at approximately biweekly intervals in the spring and summer following autumn seeding, and were separated into stems, leaves, and seed pods. Dry matter (DM) accumulation, crude protein (CP), aciddetergent fiber (ADF), and in vitro organic matter digestibility (IVOMD) were determined for each plant part at each stage. Average annual DM production at initial flowering was 5.1 Mg ha−1, and the CP, ADF, and IVOMD concentrations were 163, 279, and 750 g kg−1, respectively. The rates of nutritive value decline with age coincided with a reduction in leaf‐to‐stem ratio (from a range of 1.91 to 2.85 at vegetative stage to 0.2 at ripe seed stage) and appear lower than the rates reported for other legumes, possibly because of the long indeterminate flowering period. We concluded that the nutritive value parameters of serradella indicate that this legume has a forage quality comparable to other leguminous crops and, if seeded in double‐cropping systems (as is done in some Atlantic coastal areas of southern Europe, where it is harvested around initial flowering), it can provide forage of good quality.
Potassium Effects on Canopy Light Interception and Earliness of No‐Tillage Cotton
Authors: Gwathmey C. Owen , Howard Donald D.
Published: July 2010

Earliness of maturity is essential for adaptation of cotton (Gossypium hirsutum L.) to regions with short growing seasons, and it may be influenced by potassium nutrition. Our objectives were to determine effects of K fertilization on interception of photosynthetically active radiation and earliness, and to describe the relationship between earliness and light interception at different in‐canopy heights. Research was conducted with no tillage on a Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalf) with low extractable K. Using a split‐plot randomized complete block design, 0 and 112 kg K ha−1 were soil‐applied before planting each year as mainplot treatments, and 0 and 4.1 kg K ha−1 were foliar applied four times per season as subplot treatments. Canopy interception of photosynthetic photon flux density (PPFD) was measured at 23‐cm vertical increments in 1993 and 1994. Plots were spindle‐picked twice each year. Earliness was measured as the percent of total yield picked at first harvest. Relative to no fertilizer K, soil‐applied K increased canopy PPFD interception at all heights measured. Neither soil‐applied nor foliar K affected earliness in 1993, a drought year, but soil‐applied K decreased percent first harvest from 78 to 65% in 1994. Foliar K did not affect canopy light interception in 1993, and it increased interception in 1994 only with no soil‐applied K. At 111 d after planting, percent first harvest was negatively correlated with PPFD interception at all measured heights in the canopy, suggesting that higher K fertility delayed maturity as it increased upper‐canopy light interception. In short‐season environments, optimum K fertilization needs to be accompanied by cultivar selection and management that promote earliness of maturity.
Grain Amaranth Seeding Dates in the Northern Great Plains
Authors: Henderson Tracey L. , Johnson Burton L. , Schneiter Albert A.
Published: July 2010

An understanding of crop response to planting date is essential when evaluating a potential new crop. A field study was designed to determine the optimum range of planting dates for dryland grain amaranth (Amaranthus cruentus L. and A. hypochondriacus L. ✕ A. hybridus L.) in the Northern Great Plains. Four grain amaranth cultivars, diverse for plant height and branching, were evaluated over four consecutive years from 1989 to 1992 at Prosper (46°58′ N, 97°4′ W, elevation 220 m) in North Dakota. Soil types at the test site are a complex of Perella (fine‐silty, mixed, superactive, frigid Typic Endoaquolls) and Beardon (fine‐silty, mixed, superactive, frigid Aeric Calciaquolls). Four or five planting dates were selected, ranging from 1 May to 1 July at approximately 15‐d intervals. Year‐to‐year differences in weather influenced the response of amaranth to planting date for grain yield, days to anthesis, harvest index, plant height, final plant population, and lodging. Plants sown in mid‐June produced the greatest grain yield in 1989 and 1990, when near‐ or above‐average temperatures occurred throughout most of the growing season. Seedling survival was greater with later planting dates in all years except 1989, when excellent stands were achieved with all planting dates. Greatest yields in 1992, an unusually cool year, were produced with May planting dates; in that year, most plants sown in mid‐June did not mature before first frost. Material planted on 1 July failed to mature in both 1991 and 1992. In years with near‐ or above‐average temperatures, the mid‐June planting date was best for maximizing both stand establishment and grain yield. Given the uncertainty in predicting weather conditions, planting in early June in the Northern Great Plains should achieve good stands and produce high grain yields, while minimizing the risk of yield loss associated with cool condition.
Extractable Soil Water and Transpiration Rate of Soybean on Sandy Soils
Authors: Sinclair Thomas R. , Hammond Luther C. , Harrison J.
Published: July 2010

Substantial consistency has been obtained in describing plant response to drying soil by expressing plant performance as a function of the fraction of soil water that can be used by the plants. Generally, there is no decrease in plant activity until the soil water has been decreased to the level where only about 0.3 of the water that can be extracted by the plants remains in the soil. There is, however, ambiguity as to whether this relationship is appropriate for sandy soils. The objective of this research was to compare methods for describing extractable soil water by soybean [Glycine max (L.) Merr.] plants grown in pots with soils differing in sand content. The two methods tested were based on thermodynamic and physiological definitions of the upper and lower end‐points of extractable soil water. While differences existed in the volumetric soil water content for the two definitions of the lower end‐point of extractable soil water, these differences were small. In contrast, very large differences existed in defining the volumetric soil water of the upper end‐point either thermodynamically (commonly assumed to be ‐10 kPa for sands) or physiologically (pot capacity). As a consequence, there were large differences in the response curves obtained based on the two expressions of extractable soil water. The threshold for transpiration expressed as an absolute volumetric soil water was of course independent of the determination of the end‐points. Instead of relying on a relative transpiration response to extractable soil water, for sandy soils it may be necessary to use the volumetric soil water content determined under controlled conditions to interpret crop response under any particular field situation.
Testing for Early Photoperiod Insensitivity in Soybean
Authors: Wang Zhongchun , Reddy Vangimalla R. , Acock Mary C.
Published: July 2010

To accurately model the flowering process in soybean, it is essential to identify photoperiod‐sensitive and photoperiod‐insensitive phases of development. Despite extensive studies, there remains some disagreement about when soybean plants first become sensitive to photoperiod. The length of the juvenile phase from emergence has been found to differ for the same cultivar. This experiment tested the hypothesis that the early phase in soybean development is truly photoperiod‐independent. Soybean plants [Glycine max (L.) Merr. cv. Hutcheson; Maturity Group V] grown in controlled environments at a constant air temperature of 26°C were transferred from a noninductive 22‐h photoperiod to an inductive 8‐, 10‐, 12‐, or 14‐h photoperiod at 2‐ to 5‐d intervals after seedling emergence (defined as the day when the cotyledons appeared above the soil surface). The duration of the so‐called juvenile phase was shown to be photoperiod‐dependent, the photoperiod effect being nonlinear. Soybean plants became sensitive to an 8‐, 10‐, 12‐, and 14‐h photoperiod at ‐1, 0, 1, and 9 d after seedling emergence, respectively. Based on these and other results, we conclude that there is no juvenile phase in Hutcheson soybean, and that photoperiod sensitivity begins when seedlings are exposed to light, but the rate of progress towards flowering depends on the photoperiod experienced.
Soybean Seed Coat Discoloration in Cool‐Season Climates
Authors: Morrison Malcolm J. , Pietrzak Lukasz N. , Voldeng Harvey D.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed with yellow seed coat and hilum is preferred in North America for the export market. Seed coats may darken or discolor when exposed to chilling temperatures during seed development. We examined the effects of chilling temperatures on seed coat discoloration of yellow hilum, isogenic lines of ‘Maple Presto’ soybean (Maturity Group 000) differing in pubescence color (I, r, T, tawny; I, r, t, gray). The isogenic lines were grown in the field for five seasons and once in the growth cabinet (25/20°C day/night). We quantified seed coat discoloration using an image analyzer. When exposed to cool temperatures during seed development, the seed coat darkened. In the extreme case, the seed coat from the tawny line looked gray‐brown. The tawny line discolored more than the gray line, both in the field and the growth cabinet. Seed coat discoloration increased with the accumulation of daily minimum temperature ≤ 115°C during seed development. In years with cool temperatures during seed development, seed coats may discolor, reducing the quality of the seed's appearance.
Nitrogen Fertilizer Effect on Grain Amaranth
Authors: Myers Robert L.
Published: July 2010

Grain amaranth (Amaranthus spp.) is an ancient crop that is now receiving fresh attention. This has led to a demand for crop management information, including that on N fertilization. This study evaluated the effect of N fertilizer on amaranth grain yield, yield components, and growth and development. The study was carried out in three Missouri environments with five levels of N fertilizer (NH4NO3 broadcast preplant at 0, 45, 90, 135, and 180 kg N ha−1) and three cultivars (Plainsman, D136, and K266). Averaged across cultivars and environments, N fertilizer at the top rate of 180 kg N ha−1 produced a yield increase of 42% relative to plots receiving no N fertilizer. Yields were consistently improved by additions of 45 and 90 kg N ha−1, but additional N fertilizer above the 90 kg N ha−1 rate increased yield in only one out of three environments. At the one site where yield components were evaluated, yield differences were due to increases in seed number per plant, since seed weight and plant population at maturity were unaffected by N fertilizer rate. Plots with high rates of N fertilizer had later maturity, as indicated by time of flowering and seed moisture. Average moisture of seeds harvested from plots receiving 180 kg N ha−1 was 320 g kg−1, while seeds from plots with no N fertilizer had 240 g kg−1 moisture. Comparing the same high‐N treatment to the control with no N showed height increases of 14, 24, and 44% in the three environments. Although amaranth yield is responsive to N fertilization, high rates of N fertilization can negatively affect grain harvest in terms of excessive plant height, increased lodging, and delayed crop maturity.
Tillage Effects on Grain Sorghum and Wheat Yields in the Texas Rolling Plains
Authors: Bordovsky David G. , Choudhary Manilal , Gerard Cleveland J.
Published: July 2010

Soils of the Texas Rolling Plains have poor structure, low soil organic matter contents, and low water holding capacity. Alternative farming practices must be explored to conserve and improve this natural resource. An 11‐yr (1979‐1989) field experiment was conducted at the Texas A&M University Research Station at Munday to determine the effects of tillage (reduced vs. conventional) and residue management (with vs. without residue) on grain yields of continuous grain sorghum [Sorghum bicolor (L.) Moench] and continuous wheat (Triticum aestivum L.) under dryland and irrigated conditions. A grain sorghum—wheat rotation (double‐crop) under reduced tillage was included in the irrigated study. Yields of reduced‐tillage grain sorghum in dryland and irrigated studies were as high or higher than yields of conventional‐tillage grain sorghum. Removal of surface residues in irrigated grain sorghum caused a significant decrease in yields. In contrast, reduced‐tillage systems and surface residues caused reductions in yields for dryland and irrigated wheat, which may be the result of decreased plant populations caused by poor seed‐to‐soil contact when planting through surface residues and N deficiency caused by immobilization. The average yield of irrigated wheat or grain sorghum using reduced‐tillage double‐cropping (2 and 3 Mg ha−1, respectively) was lower relative to wheat (3.5 Mg ha−1) and grain sorghum (4.6 Mg ha−1) grown continuously under conventional tillage.
Evaluation of Switchgrass Rhizosphere Microflora for Enhancing Seedling Yield and Nutrient Uptake
Authors: Brejda John J. , Moser Lowell E. , Vogel Kenneth P.
Published: July 2010

Many rhizosphere microorganisms enhance nutrient uptake and plant growth, but their effectiveness can vary with host species and with genotype within species. This study evaluated the effectiveness of rhizosphere microflora indigenous to the rhizosphere of switchgrass (Panicum virgatum L.) for enhancing seedling yield and nutrient uptake. Switchgrass roots and rhizosphere soil were collected from native prairies and seeded stands in Nebraska, Kansas, Iowa, Missouri, Virginia, and North Carolina. Seedlings of four switchgrass cultivars were inoculated with root fragments and rhizosphere soil from each collection, fertilized with a nutrient solution, and grown in steamed sand for 12 wk in a greenhouse. Seedlings inoculated with rhizosphere microflora produced up to 15‐fold greater shoot and root yields, and recovered up to 6‐fold more N and 36‐fold more P than seedlings inoculated with rhizosphere bacteria only. These responses were consistent for all four switchgrass cultivars and were probably due to arbuscular mycorrhizal fungi. Switchgrass rhizosphere populations were highly variable in their ability to recover N and P and stimulate seedling shoot and root yields. Seedlings inoculated with rhizosphere populations from seeded switchgrass stands averaged 1.5‐fold greater shoot and root yields than seedlings inoculated with rhizosphere populations from native prairies. Rhizosphere populations that stimulated the greatest N uptake differed from populations that resulted in the greatest P uptake. Highly effective microbial populations appear to develop in the rhizosphere of seeded switchgrass stands.
Conservation Tillage Corn Production for a Semiarid, Subtropical Environment
Authors: Smart James R. , Bradford Joe M.
Published: July 2010

Because of the extreme climatic differences between their regions, farmers in southern Texas and northern Mexico have been reluctant to adopt conservation tillage systems developed in the north‐central or midwestern United States. With greater knowledge of the benefits and risks of conservation tillage practices under a semiarid, subtropical environment, producers can make better decisions regarding tillage practices. The objectives of this study were to compare the effects of conventional and conservation tillage on corn (Zea mays L.) yields and production costs during the transition from conventional to reduced tillage and provide farmers with guidelines for implementing conservation tillage in a subtropical, semiarid environment through evaluation of grain yield and production economics as affected by tillage. Conventional tillage (CT), reduced tillage with wide V‐sweeps (RT), and preplant no‐tillage (PPNT) were compared for both spring and fall corn production over three years. Grain yields for PPNT were lower than CT in the spring (−9%) and fall (−20%) of the first cropping year. Yields in PPNT were equivalent or up to 12% greater than CT yields in Years 2 and 3. Production costs were lower in the PPNT than in the CT, because of the reduced number of tillage trips over the field. A three‐year average of net returns for corn grown in the PPNT spring treatment was $47 ha−1 greater than RT, and $104 ha−1 more than the CT systems. Average fall corn net returns over three years for the PPNT were $5 ha−1 more than RT and $104 ha−1 more than CT systems. Average net returns from PPNT for spring and fall cropping seasons over three years was $23 ha−1 greater than the RT and $104 ha−1 greater than CT. Greater economic returns and lower production costs of PPNT compared with CT systems for all seasons and years were the result of reduced energy and operator time requirements. The conservation tillage systems (RT and PPNT) resulted in greater economic returns, compared with a CT tillage system, due to both greater yields in dry years and lower production costs in all years.