bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and Yield of White Lupin Under Mediterranean Conditions
Authors: Lo´pez‐Bellido Luis , Fuentes Mariano , Castillo Juan E.
Published: July 2010

In a species with a well‐defined growth pattern such as lupin, changes in plant density alter the structure and size of the canopy and affect grain yield components. A 4‐yr study of autumn‐sown white lupin (Lupinus albus L.) was conducted under rainfed Mediterranean conditions in southern Spain to determine the influence of plant density on biomass and grain yield. Three plant densities (20, 40, and 60 plants m−2) were tested in a randomized complete block design with four replications. Between‐year variation in rainfall during the growing season had more marked effects on growth indices than on grain yield. Dry matter accumulation, leaf area index, and leaf area duration were directly related to plant density; however, leaf senescence was higher with increased density. While grain yield exhibited no significant differences among the densities studied, the harvest index decreased with increasing plant density. With increasing plant density, the number of pods per plant decreased, whereas number of seeds per pod and mean seed mass remained unaltered. Path coefficient analysis showed that pods per plant and per unit area had most important direct and indirect effects on grain yield. The high plasticity of the canopy structure offset changes in grain yield components of lupin which resulted from differences in plant density and led to a constant grain yield. This feature can be turned to advantage under the extremely variable conditions of the Mediterranean climate.
Sugarcane Response to Phosphorus Fertilizer in Relation to Soil Test Recommendations on Everglades Histosols
Authors: Glaz Barry , Powell Gerald , Perdomo Raul , Ulloa Modesto F.
Published: July 2010

To protect habitat in the Everglades, legislation mandates a reduction of at least 25% in the P content of water discharged from the Everglades Agricultural Area (EAA). Accurate P fertilizer recommendations for sugarcane (interspecific hybrids of Saccharum spp.), the major crop in the EAA, are needed to help achieve this P reduction. The objective of this study was to compare two soil‐tests for basing P fertilizer recommendations for sugarcane grown on Histosols in the EAA. Three yield characteristics were measured at four field locations with no added P (P0), an often‐recommended commercial rate of 24 kg P ha−1 (P1), and 48 kg P ha−1 (P2) for the plant‐cane, first‐ratoon, and, at three locations, the second‐ratoon crop. One group of eight genotypes was planted at two locations, and two other groups of eight genotypes were each planted at one of two other locations. An acetic acid‐extractable P (Pa) soil test predicted yields better than the water‐extractable P (Pw) test. However, unexpected responses in sugar and cane yields occurred for both P extraction procedures. Further knowledge of the effects of soil pH, factors affecting P mineralization, and sugarcane genotype response to P may explain some of the unexpected results.
Sasg × estab: A sas program for computing genotype × environment stability statistics
Authors: Hussein Mohammed Ali , Bjornstad A ˚ smund , Aastveit A.H.
Published: July 2010

We provide a comprehensive SAS program for the computation of univariate and multivariate stability statistics for balanced data. The program is intended for genotype × location × year (G × L × Y) or genotype × location (G × L) data, averaged over replications (R). It computes the symmetrical joint linear regression with the right and left solutions and Tukey's 1 df for nonadditivity, the regression coefficients (b‐ or β‐values), and the deviations from regression (δij) and provides the graphs of the regression lines for both genotypes and locations. Separate regression on the positive and negative sectors of the environmental indices is also conducted. The program calculates Tai's α and λ statistics with graphical presentation of the scatter of the genotypes in the α, λ space. Other outputs of the program include the univariate stability statistics Wricke's ecovalence (Wi2), Shukla's stability variance (σi2), Hanson's genotypic stability (Di2), Plaisted and Peterson's θi, Plaisted's θ(i), Francis and Kannenberg's environmental variance (Si2), and coefficient of variance (CV); and the rank‐based nonparametric stability statistics Si(2), Si(3), Si(6), Kang's rank sum, and the stratified rank analysis of the genotypes. The program also computes Type 4 stability, superiority measure (Pi), the desirability index of genotype performance, and the pairwise genotype × environment (G × E) interaction of genotypes with checks. It partitions the G × E interaction into that due to heterogeneity of variances and that due to imperfect correlation between the genotype performance and performs the singular value decomposition of the G × E matrix, plotting the first two interactions’ principal components.
Influence of Nitrogen on Productivity and Nutritive Value of Forage Chicory
Authors: Belesky David P. , Turner Kenneth E. , Ruckle Joyce M.
Published: July 2010

Chicory (Cichorium intybusL.) is highly productive and responsive to N fertilization under midsummer conditions in the eastern USA. We conducted a field experiment for 3 yr on a Ramsey soil (loamy, siliceous, subactive, mesic Lithic Dystrudept) in southern West Virginia to determine if fertilizer N influenced forage chicory nutritive value and NO3–N concentration. Each N rate (0, 80, 160, 240, or 480 kg N ha−1) was replicated three times in a randomized block design. Swards were clipped at 6‐wk intervals during the growing season. Swards were virtually pure chicory in the first year (1994) regardless of N rate. By the third year (1996), chicory ranged from about 40% (0 N) to less than 5% (480 kg N ha−1) of swards. Botanical composition changes in the sward influenced dry matter (DM) response to N rate and herbage nutritive value. Dry matter production increased with N rate in 1994, but was not affected by N in 1996 when chicory was not a major sward component. More than 70% of total annual DM production in 1994 occurred after the first harvest, but by 1996 was less than 50%, reflecting productivity patterns typical of cool‐season swards. Nitrate concentrations in herbage were greatest (3.5 g kg−1) in 1995, a relatively dry year, and least (2.3 g kg−1) in 1996, when there was less chicory in the sward. Crude protein (CP) and in vitro organic matter disappearance (IVOMD) values indicated high forage quality throughout the course of the experiment.
Simplifying Daily Evapotranspiration Estimates over Short Full‐Canopy Crops
Authors: Ibá n ˜ ez Manuel , Castellv ı ´ Francesc
Published: July 2010

A knowledge of daily evapotranspiration (λE) from surface radiative temperature at a regional scale is of interest in agronomy. The aerodynamic formulation and the radiative Bowen ratio–energy balance method provide good estimates of instantaneous λE based on remote‐sensed canopy temperatures. Instantaneous latent heat flux estimates for the daytime period can be integrated to obtain a value for daily λE when detailed crop knowledge and continuous meteorological measurements are available. We propose a different method for estimating daily evapotranspiration for short, unstressed crops with a leaf area index (LAI) > 3. The method is based on the radiative Bowen ratio–energy balance method and on the similarity between the diurnal course of λE and solar irradiance. This regression‐based approach uses continuous measurements of air vapor pressure, air temperature, surface radiative temperature, and solar irradiance during daylight hours. Moreover, detailed crop knowledge is not required. The method was tested in a Mediterranean area with semicontinental climatic characteristics on grass (Festuca arundinacea Schreb.), wheat (Triticum aestivum L.), and alfalfa (Medicago sativa L.). Daily λE was estimated with an error <15% compared with estimates of λE made using a Bowen ratio–energy balance equipment. This new approach is promising for remote sensing applications at a regional scale, although it requires further verification for other climatological conditions.
Phosphorus Deficiency Affects the Rate of Emergence and Number of Maize Adventitious Nodal Roots
Authors: Pellerin Sylvain , Mollier Alain , Plénet Daniel
Published: July 2010

Root growth is critical for P uptake, especially when soil P availability is low. We studied the effects of P deficiency on the rate of appearance and number of adventitious nodal roots of field‐grown maize plants (Zea maysL.). Experiments were conducted in 1995, 1996, and 1997 on a long‐term P fertilization trial with three P fertilization regimes, located on a sandy soil in southwest France. Phosphorus deficiency had a negative effect on leaf area index (LAI). The amount of photosynthetically active radiation (PAR) absorbed by the canopy and plant growth were reduced, especially during the first phases of the crop cycle (between the 7‐ and 14‐visible‐leaf stage). The emergence of adventitious roots was delayed for P‐deficient plants, but the synchrony between root and leaf emergence was not disturbed. The final number of roots was significantly lower for P‐deficient plants for phytomers 4 to 7. These phytomers were those for which root differentiation occurred when the PAR absorbed by the canopy was most severely reduced relative to the fertilized P treatments. A unique relationship was found for all years and P treatments between the cumulative amount of PAR absorbed by the plant and the number of emerged adventitious roots. We concluded that the reduced number of adventitious roots for phytomers 4 to 7 on P‐deficient plants may be caused by the negative effect of P deficiency on LAI and its subsequent effect on PAR absorption and C nutrition of plants during the period of root emergence from specific phytomers.
Modeling Energy Fluxes from Sparse Canopies and Understorys
Authors: Daamen Carl C. , McNaughton Keith G.
Published: July 2010

Land surfaces are an assemblage of component surface types, for instance overstory vegetation species, understory vegetation species, and bare soil. Often two or more surface types absorb a significant fraction of the available energy to the land surface as a whole. In these cases the interaction of fluxes from the component surfaces may be important to the total land surface energy balance. We compare three models of land surface energy balance: a Penman‐Monteith model; a model with two component surfaces that don't interact (patch model); and a model with interacting component surfaces (Shuttleworth‐Wallace model). Data from six published studies are used to investigate which models best represent a particular land surface taking account of water supply to the component surfaces and overstory canopy architecture. Flux interaction between component surfaces was only found to be important when there was a large difference between the surface resistances (i.e., water availability to the surfaces). Also, all three models were found to estimate the same land surface energy fluxes (to within 50 W m−2) when both surface resistances were >300 s m−1. The ratio of (aerodynamic resistance between the canopy air space and the reference height) to (mean component surface boundary layer resistance) was useful for indicating the level of interaction between component surfaces.
Soil and Plant Influences on Crop Response to Two African Phosphate Rocks
Authors: Weil Ray R.
Published: July 2010

Affordable technologies are needed to allow smallholder farmers to effectively use the phosphate rocks (PRs) found in many African countries. A pot study was conducted in Tanzania using two PRs (Panda and Minjingu) and two soils (an Alfisol and an Andisol) to assess responses of several types of crops to these PRs and to determine whether changes in crop responses to PR with time are due to crop sequence or merely contact time with soil. The Panda PR had no effect on growth or tissue P content in maize (Zea mays L.), bean (Phaseolus vulgaris L.), and pigeon pea [Cajanus cajan (L.) Millsp.], but it nearly tripled these parameters for cabbage (Brassica oleracea L.) on the Alfisol. Freshly applied Minjingu PR only slightly stimulated maize and pigeon pea, but nearly tripled cabbage yield in both soils. Previous crop had a greater effect than previously applied PR on second crop maize. Yields and P content of maize were always lowest following cabbage and highest following pigeon pea. Minjingu PR, but not Panda PR, had residual benefits on maize. Severe Mn toxicity occurred in all crops on the unamended Andisol. The calcareous Minjingu PR, but not the Panda PR, increased yields dramatically on the Andisol, partly by raising the soil pH in water enough (from 4.6 to 5.6) to alleviate Mn toxicity. Future P fertility work in Africa should pay adequate attention to the effects of crop sequences and soil biological properties.
Dinitrogen Fixation in Kura Clover and Birdsfoot Trefoil
Authors: Seguin Philippe , Russelle Michael P. , Sheaffer Craig C. , Ehlke Nancy J. , Graham Peter H.
Published: July 2010

The quantification of symbiotic N2 fixation by legumes is essential to determine their impact on N budgets. Kura clover (Trifolium ambiguum M.B.) and birdsfoot trefoil (Lotus corniculatus L.) are two promising pasture legumes for which such estimates are scarce. Dinitrogen fixation by 2‐ and 3‐yr‐old stands of these species was determined at two locations in Minnesota using the 15N isotope dilution method. Species were evaluated for forage and N yields, the percent of N derived from the atmosphere (%Ndfa), and the amount of fixed N2 at each of four harvests. The results for each parameter varied with location, legume species, and harvest, as demonstrated by a three‐way interaction among these terms. Across environments, both species produced the greatest amount of forage, total N, and fixed N yields at the first harvest. The yields decreased with successive forage harvests at one location but stabilized at the other. The %Ndfa for Kura clover was stable across harvests and environments. The %Ndfa for birdsfoot trefoil varied during the season, with a peak at the end of the season. The yearly total forage, total N, and fixed N yields of Kura clover were stable across environments, and the total N and fixed N yields were greater than those of birdsfoot trefoil at one location. Overall, Kura clover fixed about 155 kg N ha−1 yr−1, with a %Ndfa of 57; birdsfoot trefoil had amounts of fixed N2 that varied with locations (avg. of 145 kg N ha−1 yr−1), and it obtained about 62% of its herbage N from fixation.
Bread‐Making Wheat and Soil Nitrate as Affected by Nitrogen Fertilization in Irrigated Mediterranean Conditions
Authors: Lloveras Jaime , Lopez Antonio , Ferran Javier , Espachs Sergi , Solsona Joan
Published: July 2010

Mediterranean areas are suitable for the production of high quality bread‐making wheat (Triticum aestivumL.) because of the high temperatures during grain filling. Wheat quality is also influenced by variety and can be enhanced through the use of N fertilizer. However, N fertilization can increase residual soil NO−3after harvest. The purpose of this study was to evaluate the effect of supplemental topdressed N fertilizer on quality and production of high quality bread‐making wheat and on residual soil NO−3under irrigated Mediterranean conditions. Field experiments were conducted at two sites during two growing seasons on Calcixeroclic Xerochrept soils of the Ebro Valley (Spain). Five N treatments (100, 200, and 300 kg N ha−1applied at the end of tillering and 150 or 250 kg N ha−1at the end of tillering plus 50 kg ha−1foliar‐applied N at the end of the boot stage) were imposed on two cultivars. Topdressed N increased yields, when increasing from 100 kg N ha−1to higher rates only, in soils with low residual NO−3However, N fertilization increased grain protein contents for all locations and years and bread quality parameters but with a greater effect in soils with low soil NO−3Residual soil NO−3after harvest increased little with increasing N rates. Grain protein, yield, and quality varied depending mainly on the year and amount of precipitation during grain filling. A topdress N rate of 200 kg N ha−1would be the most appropriate way to produce high quality bread‐making wheat and minimize the risk of NO−3leaching.
Predicting Leaf/Stem Ratio and Nutritive Value in Grazed and Nongrazed Big Bluestem
Authors: Smart Alexander J. , Schacht Walter H. , Moser Lowell E.
Published: July 2010

Recent advancements in describing morphological development of perennial grasses have provided a useful index for identifying dates to harvest hay or graze pasture. The objective of this study was to determine the relationship between big bluestem (Andropogon gerardii Vitman) morphological developmental stage, days from 1 May, and accumulated growing degree days (GDD) and leaf/stem ratio, crude protein (CP), and neutral detergent fiber (NDF) in grazed and nongrazed swards. The grazing experiment was conducted in eastern Nebraska during 1997 and 1998. Six grazing treatments consisting of all combinations of two herbage allowances (22 or 66 kg of herbage dry matter per animal unit day) and three grazing dates (late May, early June, and mid‐June) were randomly assigned to seven paddocks (900 m2) in each of four blocks along with a nongrazed control treatment. Random samples consisting of 50 or more tillers were hand‐clipped weekly at ground level in each paddock beginning in late May and ending in early August. Morphological developmental stage of the samples were determined, and a mean morphological stage based on shoot count [mean stage count (MSC)] was calculated. Samples were hand‐separated to determine leaf/stem ratio and analyzed for CP and NDF. Regression analysis showed that good relationships were found between MSC (R2 = 0.61–0.81), days from 1 May (R2 = 0.45–0.76), and GDD (R2 = 0.44–0.74) and leaf/stem ratio in nongrazed big bluestem and high herbage allowance swards. All three were adequate predictors of nutritive value and leafiness, but MSC may be more useful to researchers who want a more descriptive measure of plant morphological development, particularly when comparing cultivars or species.
Nitrogen Dynamics and Fertilizer Use Efficiency in Rice following Straw Incorporation and Winter Flooding
Authors: Eagle Alison J. , Bird Jeffrey A. , Hill James E. , Horwath William R. , van Kessel Chris
Published: July 2010

Incorporation of rice (Oryza sativa L.) straw, when compared with burning, affects soil N supply by increasing N and C inputs. This study determined the effects of long‐term alternative rice straw management and winter flooding on seasonal crop uptake of N, fertilizer N use efficiency (FNUE), and crop N uptake from 15N‐labeled straw. Microplots were established on two sites in California, Maxwell and Biggs, by applying 15N‐labeled fertilizer during Year 4 of a long‐term rice straw management study. At the end of the year, 15N‐labeled straw was applied to assess crop uptake of straw N in the following season. Fertilizer use efficiency by 15N dilution (FUE–15N) over the growing season at Maxwell and at final harvest at Biggs was significantly higher when straw was burned rather than incorporated. Fertilizer use efficiency by N difference was significantly greater than FUE–15N, suggesting an apparent added N interaction (ANI). Straw management did not significantly affect the uptake of residual fertilizer 15N or of straw 15N in the subsequent year. Winter flooding had no significant effect on measured parameters. Data indicate a decrease in FNUE with a concomitant and more significant increase in the plant available soil N following the change in straw management from burning to incorporation. Belowground 15N pools appear to be a larger source of N for the following crop than aboveground residue.
Quantification of Grain Yield Response to Soil Depth in Soybean, Maize, Sunflower, and Wheat
Authors: Sadras Víctor O. , Calviño Pablo A.
Published: July 2010

Risk analysis to identify the more profitable or less risky crops in areas with shallow soil requires quantification of yield responses to physical constraints to root penetration. Grain yield, shoot biomass, and harvest index (HI) were measured in commercial fields of indeterminate soybean (Glycine max L. Merr.), maize (Zea mays L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) grown on Typic Argiudols and Petrocalcic Paleudols. At crop maturity, shoots were sampled along transects (approximately 200 m) with soil depths between 0.35 and >1 m as determined by petrocalcic horizon depth. In all four species, shallow soil reduced shoot biomass and grain yield but did not affect HI in wheat. Harvest index was most affected by shallow soil in maize. Seasonal water deficit [maximum – actual evapotranspiration (ET)] accounted for 43 to 90% of the variation in yield. Average water use efficiency (WUE) was wheat, 14.5; maize, 11.7; soybean, 8.9; and sunflower, 7.5 kg grain ha−1 mm−1 ET. In relation to crops on the deepest soil, yield decline per centimeter reduction in soil depth was 0.41% in wheat, 0.45% in soybean, 0.54% in sunflower, and 0.76% in maize. This ranking of grain yield response to shallow soil was mostly accounted for by (i) cropping season (autumn to late spring for wheat vs. spring to autumn for row crops), (ii) timing of the most critical period for grain yield determination (later in soybean than in sunflower and maize), and (iii) plant features related to vegetative and reproductive plasticity, including growth habit.
Annual Medic and Berseem Clover Dry Matter and Nitrogen Production in Rotation with Corn
Authors: Sheaffer Craig C. , Simmons Steve R. , Schmitt Michael A.
Published: July 2010

Annual medic (Medicago truncatulaGaertn.) and berseem clover (Trifolium alexandrinumL.) have potential to fix atmospheric N2for use by subsequent crops. Our objectives were to determine the dry matter and N production of annual barrel medic and berseem clover, and their effect on grain yield of a subsequent corn (Zea maysL.) crop. First‐year treatments included spring‐seeded annual medic–oat (Avena sativaL.) and berseem clover–oat intercrops; summer‐seeded annual medic following spring‐seeded oat; and a spring‐seeded oat monoculture. The second‐year corn crop was fertilized with four N rates. In three of four environments, berseem clover had greater average fall dry matter (4392 kg ha−1) and N yield (125 kg ha−1) than spring‐ or summer‐seeded barrel medic. Spring‐ and summer‐seeded medics had similar fall dry matter (1309 kg ha−1avg.) and N yields (38 kg ha−1avg.) in two environments, but spring‐seeded medics had greater dry matter and N yield than summer‐seeded medic in two environments (avg. dry matter yield of 5304 and 2428 kg ha−1, respectively, and N yield of 138 and 70 kg ha−1, respectively). Berseem clover and medic did not consistently differ in their effects on soil NO3–N or corn grain yield when no N fertilizer was applied. Legume treatments increased second‐year corn grain yields from 9% for the silt loam soil to 82% for the loamy sand soil compared with the no‐legume treatment when no fertilizer N was applied; however, this effect decreased as N fertilizer rate increased.
Termination of Sewage Biosolids Application Affects Wheat Yield and Other Agronomic Characteristics
Authors: Barbarick K. A. , Ippolito J. A.
Published: July 2010

Biosolids land application for beneficial use requires managers to use agronomic rates to avoid nutrient overapplication. Consequently, one question regarding biosolids land application is, “Once application ceases, how long does it take agronomic properties associated with excessive biosolids applications to approach the agronomic characteristics corresponding to an untreated control?” In a summer fallow rotation system receiving 40 dry Mg biosolids ha−1 rate per cropping (six to nine times larger than the agronomic rate) for five applications (>10 yr), we compared dryland hard red winter wheat (Triticum aestivum L. ‘Vona’ or ‘TAM 107’) and 0‐ to 20‐cm soil depth responses to results for an untreated, unfertilized control (0 Mg ha−1) for three croppings (>6 yr) following discontinuation. We applied biosolids from the Littleton/Englewood, CO, wastewater treatment plant to an Aridic Paleustoll and an Aridic Argiustoll soil at Sites A and B, respectively. Using a split plot in time design, we found differences, probably due to climatic variations, between the control and the discontinued biosolids treatment for yield and grain N, P, Zn, and Cu concentration at Site A and a significant cropping effect on all plant parameters at both sites. After five applications of biosolids exceeding the agronomic rate by six‐ to ninefold, the discontinued biosolids treatment produced similar soil NH4HCO3–diethylenetriaminepentaacetic acid (AB‐DTPA) extractable P and Zn at both sites, and soil AB‐DTPA Cu and electrical conductivity of a saturated soil–paste extract (ECe) at Site A by the third cropping following termination.
Cultivating Better Nutrition: Can the Food Pyramid Help Translate Dietary Recommendations into Agricultural Goals?
Authors: Peters Christian J. , Fick Gary W. , Wilkins Jennifer L.
Published: July 2010

An explicit goal of agricultural production should be good human nutrition. Concurrent trends of chronic disease and obesity in the developed world and energy and micronutrient deficiency in the developing world reflect in part an inadequate correspondence between food production and food needs. Cropland allocation is one leverage point for changing the current system so that food supplies better reflect nutritional requirements. However, most methods for assessing the adequacy of food supplies or agricultural output tend to focus only on calories. Fortunately, recent research by the USDA Economic Research Service (ERS) suggests that the Food Pyramid can serve as a basis for estimating how cropland should be allocated to meet nutritional needs. While the Food Pyramid has been subjected to a flurry of criticism in both the academic and the popular press, the methods employed by ERS allow for a whole‐diet approach to food supply assessment and are useful irrespective of any future changes in Food Guide recommendations. Moreover, the current critique of the Pyramid completely ignores agricultural sustainability and questions of what kind of diets are possible for the food system to produce in the long term. For this reason, agricultural scientists must become engaged in the discussion of human nutrition to ensure that agroecological concerns are included in determining how to allocate land resources to nutritious ends.
Phytochemical Characterization of Six Sesame (Sesamum indicum L.) Genotypes and Their Relationships with Resistance against the Sweetpotato Whitefly Bemisia tabaci Gennadius
Authors: Laurentin Hernán , Pereira Carlos , Sanabria María
Published: July 2010

To determine the phytochemical relationship of six sesame (Sesamum indicum L.) genotypes and their resistance against whiteflies (Bemisia tabaci Gennadius), a randomized complete block field trial with six treatments (genotypes) and four replications was conducted in the Microsur growing area of the Municipio Santa Rosalìa, Portuguesa State, Venezuela. Whitefly eggs and nymphs were counted weekly during 6 wk in each experimental plot. At the end of the crop cycle, the presence or absence of eight secondary metabolites from each plant organ in experimental plots was determined. The relationship among the genotypes was observed by means of a phenogram and the respective analyses of principal coordinates. Significantly different characterizations were found on the 19x10 and 43x32 genotypes. An analysis of principal components was conducted with metabolites in the leaves and the values of foliar acidity. This analysis separated the genotypes 19x10 and 43x32 from the other genotypes with the lowest foliar acidity values. These two genotypes harbored the lowest incidence of eggs and nymphs of whiteflies (nearly 10 and 50% of the total incidence in the other genotypes), demonstrating the importance of foliar acidity values of sesame as resistance mechanisms against whiteflies.
Emergence and Seedling Structure of Temperate Grasses at Different Planting Depths
Authors: Sanderson Matt A. , Elwinger Gerald F.
Published: July 2010

Some producers have adopted ecologically based practices such as planting complex forage mixtures in their grazing systems to exploit the potential benefits of biodiversity. An understanding of grass seedling emergence and structure under different planting conditions could help develop planting recommendations for establishing multispecies swards. We conducted controlled‐environment and field studies to compare the seedling emergence and morphology of several grasses at three planting depths. Perennial ryegrass (Lolium perenne L.; diploid and tetraploid cultivars), orchardgrass (Dactylis glomerata L.), prairiegrass (Bromus catharticus Vahl), and bromegrass (Bromus stamineus Desv.) were planted at 1, 3, and 6 cm in the growth chamber and greenhouse. Seedlings were destructively sampled 14 d after emergence, and leaves, tillers, and roots were counted. Mesocotyl length and coleoptile width were measured. The grasses were planted in two field experiments to determine emergence and seedling size when planted at 1, 3, or 6 cm. Both perennial ryegrass and orchardgrass elongated the mesocotyl from 1 to 4 cm depending on planting depth, but bromegrass and prairiegrass did not. Seedlings of bromegrass and prairiegrass had greater mass but fewer tillers and roots than perennial ryegrass. Increased planting depth reduced seedling size by reducing the number and size of leaves and number of tillers by 15 to 30% in all grasses. Differences in seedling size and structure among cultivars within species were positively correlated (r of 0.8 to 0.9, P < 0.05) with seed mass. Variation in seed mass and coleoptile width, however, did not explain differences among grasses in seedling emergence in the field.
Effects of Disease, Nitrogen Source, and Risk on Optimal Nitrogen Fertilization Timing in Winter Wheat Production
Authors: Roberts Roland K. , Walters Jeremy T. , Larson James A. , English Burton C. , Howard Donald D.
Published: July 2010

Nitrogen source and timing can interact with glume blotch (Stagonospora nodorum) and take‐all root rot (Gaeumannomyces graminis var. trittici) to affect risk in wheat (Triticum aestivum L.) production. The objectives of this research were to evaluate the effects of N source, N timing, and disease severity on expected yield and risk and to evaluate the risk–return trade‐offs between N sources for farmers with different risk preferences. A Just–Pope model was used to estimate separate mean yield and yield variance (risk) effects in evaluating the N timing decision. Wheat yields for 1998 through 2000 were obtained from an experiment on Collins silt loam (coarse‐silty, mixed, active, acid, thermic Aquic Udifluvents). The experimental design was a split plot with five replications. Main plots were fertilized on 15 February, 1 March, 15 March, 1 April, and 15 April. The N sources and fertilization rate were ammonium nitrate (AN) and urea ammonium nitrate (UAN), both applied at 101 kg N ha−1. Glume blotch occurred in 1998, and take‐all occurred in 2000. Nitrogen timing, glume blotch severity, and take‐all severity significantly increased risk for AN but not for UAN. Nevertheless, at average disease ratings, fertilization with AN on 8 March was the utility‐maximizing N source and date regardless of risk preferences. The finding that AN was the optimal N source is worth $40.74 ha−1 to net‐return–maximizing wheat farmers who fertilize with AN instead of UAN. With take‐all severity at its higher 2000 level, risk increased for AN relative to UAN, but the net‐return advantage of AN was still positive at $26.41 ha−1
Defining Yield Goals and Management Zones to Minimize Yield and Nitrogen and Phosphorus Fertilizer Recommendation Errors
Authors: Chang Jiyul , Clay David E. , Carlson Charles G. , Reese Cheryl L. , Clay Sharon A. , Ellsbury Mike M.
Published: July 2010

Three general approaches (minimize soil nutrient variability, yield, and fertilizer recommendation errors) have been used to assess nutrient management zone boundaries. The objective of this study was to determine the influence of different approaches to define management zones and yield goals on minimizing yield variability and fertilizer recommendation errors. This study used soil nutrient and yield information collected from two east‐central South Dakota fields between 1995 and 2000. The crop rotation was corn (Zea mays L.) followed by soybean [Glycine max (L.) Merr.]. The four management zone delineation approaches tested were to: (i) sample areas impacted by old homesteads separately from the rest of the field; (ii) separate the field into grid cells; (iii) use geographic information systems or cluster analysis of apparent electrical conductivity, elevation, aspect, and connectedness to identify zones; and (iv) use the Order 1 soil survey. South Dakota fertilizer N and P recommendations were used to calculate fertilizer requirements. This study showed that management zones based on a 4‐ha grid cell and an Order 1 soil survey had lower within‐zone yield variability than the other methods tested. The best approaches for minimizing recommendation errors were nutrient specific. Nitrogen and P recommendations were improved using multiple years of yield monitor data to develop landscape‐specific yield goals, sampling old homesteads separately from the rest of the field, and grid cell soil sampling to fine‐tune N and P recommendations.
Row‐Spacing and Seeding Rate Effects on Glyphosate‐Resistant Soybean for Mid‐Atlantic Production Systems
Authors: Kratochvil Robert J. , Pearce Justin T. , Harrison Michael R.
Published: July 2010

Glyphosate [N‐(phosphonomethyl)‐glycine]‐resistant soybean [Glycine max (L.) Merr.] production in the Mid‐Atlantic occurs under full‐season and double‐crop production systems. Row‐spacing and seeding rate manipulation affects the yield of soybean. This study evaluated the effects upon yield caused by reductions in seeding rate from current standards for these two systems. During 2000–2002, row spacing (19 and 38 cm) and seeding rates (current standard, 20 and 40% less, and 20% greater than the standard) were tested using four glyphosate‐resistant cultivars representative of the maturity groups for the region. Tests were conducted for both full‐season and double‐crop systems at two Maryland locations for each per year on coastal plain soils. During the 3 yr, only 1 out of 48 total cultivar × row spacing comparisons for the two production systems had better yield with 38‐cm rows. At best, 38‐cm row spacing produced equivalent to the 19‐cm rows. A 20% seeding rate reduction (345800 seeds ha−1 for full‐season and 444600 seeds ha−1 for double‐crop production) was generally found to not yield significantly different than the standard seeding rates for both systems. A 40% reduction consistently had yield significantly less than the standards in both systems. These results indicate a 20% seeding rate reduction can be a cost‐saving practice for glyphosate‐resistant soybean production in the Mid‐Atlantic. With no yield loss at a 20% reduced seeding rate, additional profit ranging from $14.30 to $27.72 ha−1 can be realized.
Screening Yield Monitor Data Improves Grain Yield Maps
Authors: Simbahan G. C. , Dobermann A. , Ping J. L.
Published: July 2010

Yield monitor data contain systematic and random errors, which must be removed for creating accurate yield maps. A general procedure for assessing yield data cleaning methods was applied to a new postprocessing algorithm in which six common types of erroneous yield monitor values were removed: (1) combine header status up; (2) start‐/end‐pass delays; (3) grain flow, distance traveled, and grain moisture outliers; (4) values exceeding minimum and maximum biological yield limits; (5) local neighborhood outliers; and (6) short segments and co‐located points. The algorithm was applied to four yield maps of maize (Zea maysL.) and soybean [Glycine max. (L.) Merr.] grown under irrigated and rainfed conditions. A total of 13 to 20% of the original yield monitor data was removed, with 72 to 85% of the removal occurring in the mandatory, primary screening process (Steps 1 and 2). Only 2.6 to 3.9% of the original yield monitor data were removed during secondary screening (Steps 3 through 6), but this additional screening lead to yield semivariograms with smaller nugget values and sills and a relative increase in map precision of 4.3 to 5.4% compared with conducting primary screening only. The local neighborhood outlier test (Step 5) removed a larger proportion of yield values in soybean (12.8 to 14.9% of all deleted values) than in maize (2.7 to 3.2%). The proposed algorithm is robust enough for implementation in commercial software but requires further testing in other crops and environments and with other brands of yield monitors.
Growth and Development of Hairy Vetch Cultivars in the Northeastern United States as Influenced by Planting and Harvesting Date
Authors: Teasdale John R. , Devine Thomas E. , Mosjidis Jorge A. , Bellinder Robin R. , Beste C. Edward
Published: July 2010

Hairy vetch (Vicia villosaRoth) is a winter annual legume that has become an important cover crop for sustainable production systems. New cultivars of hairy vetch, developed in the southern United States, need to be tested as cover crops in the northeastern states. Research was conducted at three locations (Salisbury, MD; Beltsville, MD; and Freeville, NY) that represent a range from a relatively mild coastal climate to a colder interior climate. Four cultivars of hairy vetch (common and three cultivars developed at Auburn University, AU Early Cover, Advanced Population 8, and Advanced Population 26) were planted at either optimum or delayed dates, and biomass was harvested when either vegetative or flowering. Common hairy vetch biomass was equal to or higher than the Auburn cultivars at all locations and years. The Auburn cultivars were winter hardy under Maryland but not under New York conditions. The Auburn cultivars reached 50% flowering an average of 15 d earlier than common hairy vetch. Delaying planting by 2 to 3 wk reduced hairy vetch biomass by 43% when harvested vegetative and by 20% when harvested at flowering. Hairy vetch growth and development could be predicted on the basis of growing degree days (GDD) with a base temperature of 4°C. The biomass of common hairy vetch increased linearly by 41 g m−2for every 100 GDD, and there was no significant difference in the slope of biomass gain between cultivars. Results suggest that the Auburn cultivars are an alternative for Maryland growers desiring a legume cover crop that flowers earlier than common hairy vetch but that delayed planting may compromise adequate winter ground cover and spring biomass regardless of cultivar.
Agro‐Economic Characterization of Rice Production in a Typical Irrigation Scheme in Burkina Faso
Authors: Segda Z. , Haefele S. M. , Wopereis M. C. S. , Sedogo M. P. , Guinko S.
Published: July 2010

Yield, yield gaps, input use, N‐use efficiency, productivity, and profitability of irrigated rice in Burkina Faso were determined for a typical irrigation scheme in the dry season (DS) 1999 and the wet season (WS) 2000. Objectives were to analyze agro‐economic constraints and opportunities and determine ways to overcome such constraints. The simulation model RIDEV was used to analyze farmers' crop management practices, revealing considerable deviation between actual and optimal timing of crop management interventions. This diversity of cropping practices caused considerable variation of internal efficiency of N (IEN), partial factor productivity of N (PFPN), N recovery fraction (RFN), rice (Oryza sativaL.) grain yields, and net benefits of N‐use. The results showed a clear relation between plant N uptake and yield (mean IEN of 48 kg grain kg−1N uptake in farmer's fields), but the relation between N applied and yield was scattered. The PFPN varied from 16 to 52 kg grain kg−1N applied (mean of 35 kg grain kg−1N applied) due to a large range of fertilizer N recovery rates (RFN = 7–77%; mean of 37%). Farmers' average yields were 4.9 Mg ha−1in the DS and 3.6 Mg ha−1in the WS, but yields were very variable and ranged from 0.9 to 7.9 Mg ha−1in the DS and from 1.0 to 7.9 Mg ha−1in the WS. Yield gaps between average farmer's yield and best farmer's yield were high (3.0 Mg ha−1in the DS and 4.3 Mg ha−1in the WS), indicating considerable scope for yield increases in both seasons. Net benefits to irrigated rice cropping were mostly positive (avg. $418 (US) ha−1) in the dry season, but very low in the wet season (avg. $108 (US) ha−1). Partial budget analysis of fertilizer use revealed considerably lower value/cost ratios of fertilizer use in the wet season (mean V/C: 1.5) compared with the dry season (mean V/C: 2.9). It was concluded that improved crop management practices are the key to reach higher yields and financial returns without additional investments.
Bermudagrass Management in the Southern Piedmont USA: VIII. Soil pH and Nutrient Cations
Authors: Franzluebbers A. J. , Wilkinson S. R. , Stuedemann J. A.
Published: July 2010

Forage utilization could affect soil nutrient dynamics and depth distribution, potentially changing long‐term productivity and environmental quality. The effect of forage utilization on nutrient cycling might also be altered depending upon the source and quantity of nutrients applied. We evaluated changes in soil pH and extractable‐soil nutrient cations during the first 5 yr of bermudagrass [Cynodon dactylon (L.) Pers.] management varying in fertilization (three different sources targeted to supply 200 kg N ha−1 yr−1) and forage utilization (four levels). Chicken (Gallus gallus) broiler litter (5.4 Mg ha−1 yr−1) was a significant source of nutrient cations in addition to N and P and therefore, at the end of 5 yr, resulted in extractable‐soil concentrations (0‐ to 15‐cm depth) that were 1.5 ± 0.1 times greater for K, 1.6 ± 0.2 times greater for Mn, 4.3 ± 2.2 times greater for Zn, and 7.5 ± 0.8 times greater for Cu than under inorganic and clover (Trifolium incarnatum L.) + inorganic fertilization regimes. The increases in extractable‐soil K, Zn, Mn, and Cu concentrations with broiler litter, however, were only 13 ± 42% of nutrients applied. Removal of forage as hay resulted in significant declines in extractable‐soil K and Mg under all fertilization regimes and in extractable‐soil Ca and Mn with inorganic and clover + inorganic fertilization. Cattle (Bos taurus) grazing resulted in greater nutrient cycling within the paddock domain, and the more diverse and higher quantity of several nutrient cations applied with broiler litter either prevented a decline or contributed to an increase in concentrations with time.
Daily Simulation of Potential Dry Matter Production of Annual Field Crops in Tropical Environments
Authors: Verdoodt Ann , Van Ranst Eric , Ye Liming
Published: July 2010

This paper describes the modeling procedures activated when assessing potential biomass production using the Daily Crop Growth Simulator (DAICROS). Under optimal water and nutrient supply, the main physiological processes governing crop growth are photosynthesis, respiration, and leaf expansion. Simulation of the gross photosynthesis rate involves, among others, assessment of the maximum photosynthesis rate at light saturation, description of the photosynthesis light response of a fully developed canopy, and simulation of the leaf area index (LAI). Within the respiration module, maintenance respiration losses are quantified together with the conversion efficiency of the net primary assimilates into crop dry matter (DM), reflecting growth respiration losses. Leaf growth is simulated using a simplified model based on the LAI at maximum growth rate and the characterization of four leaf growth stages including fast linear growth during the vegetative stage and exponential decay at the end of the crop cycle. Input requirements include daily records of temperature and sunshine duration and crop parameters to be provided by local experts or the international literature. Both input requirements and output returns are illustrated by a case study simulating potential DM production of common bean (Phaseolus vulgaris L.) in Kigali, Rwanda. Sensitivity analysis and comparison of the simulated potential yields of five annual crops with field, literature, and alternative crop growth model outputs proved successful for model validation in the tropics and subtropics. Modeling capacity, functionality, and expendability of DAICROS surpass the performance of the worldwide operational crop growth model for land evaluation purposes developed by Tang.
Obligatory Summer‐Dormant Cool‐Season Perennial Grasses for Semiarid Environments of the Southern Great Plains
Authors: Malinowski D. P. , Zuo H. , Kramp B. A. , Muir J. P. , Pinchak W. E.
Published: July 2010

Introduced cool‐season perennial grasses may become an important complementary winter forage to dual‐use wheat (Triticum aestivumL.) in high‐risk semiarid environments of the southern Great Plains. Currently recommended, summer semidormant cultivars are not adapted to prolonged and severe summer drought and not productive in the autumn grazing season. In an experiment planted at Vernon, TX, on a Miles fine sandy loam (fine‐loamy, mixed, thermic Udic Paleustalfs) in October 2000, we evaluated productivity and plant survival of an obligatory summer‐dormant ‘Grasslands Flecha’ and summer semidormant ‘Georgia 5’, ‘Jesup’, and ‘Kentucky 31’ tall fescue (Festuca arundinaceaSchreb.); a highly summer semidormant ‘Grasslands Maru’ hardinggrass (Phalaris aquaticaL.); and summer semidormant ‘Grasslands Matua’ and ‘Grasslands Tango’ prairiegrass (Bromus wildenowiiKunth) under two defoliation intensities of 7.5 and 15 cm. Georgia 5, Jesup, and Grasslands Flecha were either infected with the novelNeotyphodium coenophialumGlenn, Bacon, and Hanlin endophyte strain AR542, with their endemic endophytes (except for Grasslands Flecha), or noninfected (E–). Only Grasslands Flecha and Grasslands Maru successfully survived summer droughts during 2001–2004. Prairiegrass behaved as an annual but did not reseed in 2003. Aboveground biomass was greater at 15‐ vs. 7.5‐cm defoliation height, except for 2004 growing season. In Grasslands Flecha, the novel endophyte increased tiller survival during summer drought by 150% (2001) and 121% (2002) when compared with E– plants. Obligatory and highly summer semidormant cultivars of perennial cool‐season grasses may be productive and persistent in the southern Great Plains and have the potential to complement forage from dual‐use wheat pastures.