bluuebunny/crossref_metadata_2025 huggingface dataset:
Tillage and Nitrogen Fertilization Influences on Grain and Soil Nitrogen in a Spring Wheat–Fallow System
Authors: Halvorson Ardell D. , Wienhold Brian J. , Black Alfred L.
Published: July 2010

Spring wheat (Triticum aestivum L.) is generally produced in the northern Great Plains using tillage and a crop–fallow system. This study evaluated the influence of tillage system [conventional‐till (CT), minimum‐till (MT), and no‐till (NT)] and N fertilizer rate (0, 22, and 45 kg N ha−1) on grain N, grain N removal from cropping system, and changes in residual postharvest soil NO3–N during six rotation cycles of a dryland spring wheat–fallow (SW–F) cropping system. Grain N concentration increased with increasing N rate and was higher with CT (33.3 g kg−1) than with NT (32.3 g kg−1) at 45 kg ha−1 N rate. Grain N removal per crop was greater with CT (70 kg N ha−1) and MT (68 kg N ha−1) than with NT (66 kg N ha−1) and tended to increase with increasing N rate, but varied with rotation cycle. Total grain N removal in six rotation cycles was in the order: CT > MT > NT. Total grain N removal by six SW crops was increased by N fertilization, with only 21 and 17% of the applied N removed in the grain for the 22 and 45 kg ha−1 N rates, respectively. Postharvest soil NO3–N levels in the 150‐cm profile varied with N rate and rotation cycle, with residual NO3–N increasing during consecutive dry crop cycles. In contrast, some leaching of NO3–N below the SW root zone may have occurred during wetter crop cycles. Soil profile NO3–N levels tended to be greater with CT and MT than with NT. Variation in precipitation during rotation cycles and N fertilization impacted grain N removal and residual soil NO3–N levels more than tillage system within this SW–F cropping system.
Winter Wheat Cultivar Performance as Affected by Production Systems in Croatia
Authors: Varga Boris , Svečnjak Zlatko , Pospisil Ana
Published: July 2010

The use of intensive production systems (IPS) may substantially increase winter wheat (Triticum aestivum L.) grain yields in Croatia because the national average yield of 4.14 t ha−1 is low compared with the yield potential of currently grown cultivars. Field experiments were conducted during 1996 through 1998 to evaluate the agronomic responses of 15 modern cultivars grown at two seeding rates (440 and 770 seeds m−2) in both an IPS and an extensive production system (EPS). The IPS consisted of plowing at 30 to 32 cm; fertilization at 194, 130, and 130 kg ha−1 N, P, and K; and high input of crop protection chemicals. The EPS involved plowing at 20 to 22 cm; fertilization at 59, 104, and 104 kg ha−1 N, P, and K; and less effective herbicide application. Grain yields significantly increased in the IPS and averaged 7840 kg ha−1 compared with 5910 kg ha−1 for the EPS. This difference was due to a 16.8 and 19.6% increase in spike number and kernel number per spike, respectively, while 1000‐kernel weight for the IPS decreased by 6.0% compared with the EPS. Higher seeding rate maximized grain yields in both production systems except for one growing season in the IPS, primarily due to improved spike number. Cultivars responded similarly to seeding rates regardless of the production system. A significant interaction between cultivars and the two production systems was found because some cultivars were highly responsive to the IPS while others were not. Thus, cultivar selection is an important consideration for Croatian farmers when they decide to adopt the IPS.
Tillage, Crop Sequence, and Cultivar Effects on Sclerotinia Stem Rot Incidence and Yield in Soybean
Authors: Kurle James E. , Grau Craig R. , Oplinger Edward S. , Mengistu Alemu
Published: July 2010

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) de Bary, is an important soybean [Glycine max (L.) Merr.] disease in the North Central States. The effect of tillage, crop sequence, and cultivar on SSR incidence and soybean yield was evaluated in a 3‐yr on‐farm study conducted at Janesville, Sharon, and Waunakee, WI. In the study, arranged in a split‐split‐split‐split plot design, main plots were tillage: moldboard (MB), chisel plow (CP), or no‐till (NT); subplots were 1995 crops: corn (Zea mays L.), small grain, or soybean; sub‐subplots were 1996 crops: corn, small grain, or soybean cultivar. Sub‐sub‐subplots were soybean cultivars planted in 1997. In 1997, SSR incidence averaged >40% at Janesville and Waunakee, and <1% at Sharon; and was lowest in NT (P < 0.001) or when the soybean cultivar S19–90 was planted (P < 0.001). Planting corn or oat (Avena sativa L.) the preceding year (1996) reduced SSR incidence in 1997 (P < 0.001). Yield was highest in NT (P < 0.001), in S19–90 (P < 0.001), and following oat (P < 0.001). Sclerotial density was affected by tillage (P < 0.001). Apothecial numbers were greatest in MB and lowest in NT. Because brown stem rot, Phialophora gregata (Allington and Chamberlain) W. Gams, and SSR developed at Janesville, there was a simple linear relationship between yield and SSR incidence (R2 = 0.35, P < 0.01) only at Waunakee. Soybean yields were greatest when S19–90 was planted in NT following corn or oat.
Nutritive Value and Animal Selection of Forage Chicory Cultivars Grown in Central Appalachia
Authors: Foster Joyce G. , Fedders James M. , Clapham William M. , Robertson Jared W. , Bligh David P. , Turner Kenneth E.
Published: July 2010

The unequivocal success of ‘Grasslands Puna’ (Puna) chicory (Cichorium intybus L.) as a forage species in other areas has not been realized in the central Appalachian Region of the USA. A field study was conducted in southern West Virginia (38° N, 81° W; 850 m above sea level) to compare nutritional qualities and palatability of herbage from three forage chicory cultivars that were developed in different parts of the world. Puna, ‘INIA Le Lacerta’ (Lacerta), and ‘Forage Feast’ were established on a Gilpin soil (fine‐loamy, mixed, semiactive, mesic, Typic Hapludults) in replicated plots in 1997 and 1998, and herbage was used for chemical analyses and ruminant feeding assessments. Whitetail deer (Odocoileus virginianus), in a free‐foraging situation, and sheep (Ovis aries), in two cafeteria trials, discriminated against Forage Feast. Deer selected Lacerta first; sheep did not exhibit a preference for Lacerta over Puna. Mature leaves from vegetative rosettes of the three cultivars had similar concentrations of crude protein, neutral detergent fiber, and acid detergent fiber (P > 0.10). In vitro organic matter disappearance and amino acid composition were also similar among the cultivars (P > 0.05). In all cultivars, approximately 65% of the total N occurred as protein amino acids. Nonprotein amino acids were not major constituents in any of the cultivars. Results suggest that differences in palatability and intake of chicory are related to the secondary plant metabolite composition of the herbage.
Economic Viability of High Digestibility Sorghum as Feed for Market Broilers
Authors: Dowling L.F. , Arndt C. , Hamaker B.R.
Published: July 2010

Recently, improved lines of the high‐lysine mutant of grain sorghum [Sorghum bicolor (L.) Moench] have been shown by Hamaker, Axtell, and coworkers at Purdue University to have substantially greater digestibility of protein than normal cultivars. These lines exhibit substantially greater digestibility of protein than normal cultivars. Here, we seek to estimate the value of high digestibility sorghum (HDS) relative to regular sorghum for market broilers. To do this, nutritional characteristics of HDS derived from laboratory tests were incorporated into a least‐cost feed mix linear programming model. The model was used to optimize rations for starting and grown‐for‐market broilers (Gallus gallus domesticus) in poultry production for three age categories: 0 to 3 wk, 3 to 6 wk, and 6 to 8 wk. The base model established a premium value on HDS of $1.54, $1.24, and $0.96/t for use as feed for chicks in the three corresponding age ranges. Sensitivity analysis was performed with respect to objective function coefficients and HDS amino acid digestibility. Over a range of historical and regional prices, the inclusion of HDS was relatively stable, and average premiums for HDS derived were close to or above base model values. From amino acid digestibility parametric analysis, it was found that the premium on HDS increases essentially linearly with improvements in digestibility over the 0 to 10% range.
Yield Mapping to Document Goose Grazing Impacts on Winter Wheat
Authors: Borman Michael M. , Louhaichi Mounir , Johnson Douglas E. , Krueger William C. , Karow Russell S. , Thomas David R.
Published: July 2010

In southwestern Washington and western Oregon, increasing numbers of wintering Canada geese (Branta canadensis) graze several farm crops including wheat (Triticum aestivum L.). Our objectives were to develop methods to determine timing, intensity, and locations of grazing, and to measure the impact of grazing on grain yield. Aerial photography with ground‐truth photography and repeated sampling worked well to determine timing, intensity, and locations of grazing. Exclosures served as nongrazed controls. A yield‐mapping‐system‐equipped combine measured yields. All data collection points were spatially located via differential global positioning system (DGPS) technology, which allowed us to integrate all data spatially and temporally via geographical information system (GIS) technology. Based on yield‐mapping‐system data, goose grazing resulted in grain yield differences ranging from a 16% increase on part of one field to a 25% decrease on an area of a field heavily grazed in April, just before geese migrated north. Comparisons of exclosures (nongrazed controls) with paired plots provided variable results. Results from paired‐plot comparisons for three fields during 1998 were 25% reduction, no difference, and 13% increase in grain yields in the paired plots available for grazing vs. exclosures. Based on yield‐mapping‐system data, the same three fields experienced 19, 7, and 5% grain yield reductions due to goose grazing with the extent of reduction depending on a combination of timing, intensity, and extent of grazing. Paired plots did not adequately represent grazing impacts on the fields. The yield‐mapping system provided nearly complete coverage of the fields and adequately captured grazing impacts.
Zone of Autotoxic Influence around Established Alfalfa Plants
Authors: Jennings John A. , Nelson C. Jerry
Published: July 2010

Interseeding alfalfa (Medicago sativa L.) to thicken declining alfalfa stands is seldom successful due to autotoxicity. Our objective was to characterize the lateral zone of autotoxic influence around established plants. Experiments were conducted in South Missouri in alfalfa fields of ‘Apollo’ [Location 1 (L1)] and ‘Cody’ (L2) in 1992 and ‘Cimarron’ (L3) in 1993. Soils were Poynor cherty silt loam (loamy‐skeletal over clayey, siliceous, mesic Typic Paleudult) at L1, Ashton silt loam (fine‐silty, mixed, mesic Mollic Hapludalf) at L2, and Waben very cherty silt loam (loamy‐skeletal, siliceous, mesic Ultic Hapludalf) at L3. Established alfalfa was killed in May with herbicide within 2 m of selected alfalfa test plants, and then 1 yr later, Cody alfalfa was seeded within 1 m around the test plants. Granular chlorpyrifos and seed treatment metalaxyl at planting did not improve alfalfa seedling establishment or yield. Seedlings were smaller (p < 0.05) near both live and dead test plants at L1, indicating mainly autotoxicity, but at L2, yield per plant was reduced more within 25 cm from live than from dead plants, indicating competition was involved. Clipping test plants more frequently at L3 did not improve establishment and reduced seedling yield for six of eight harvests. Seedling density and dry matter yield averaged 70 and 44% (p < 0.05) of the control, respectively, within 20 to 25 cm of test plants, an area equivalent to a stand density of 8 plants m−2. The zone of influence around established alfalfa plants involves both competition and autotoxicity and needs to be considered in replant decisions.
Grazing Effects on Herbage Mass and Composition in Grass–Birdsfoot Trefoil Mixtures
Authors: Leep Richard , Jeranyama Peter , Min Doo-Hong , Dietz Timothy , Bughrara Suleiman , Isleib James
Published: July 2010

Grass–legume mixtures have the ability to supply more consistent forage yields across a wide range of environments throughout the grazing season than do grass monocultures. The suitability of diverse grass species in binary mixtures with birdsfoot trefoil (Lotus corniculatus L.) in rotational stocking systems has not been extensively studied. The objective of this study was to evaluate binary mixtures of five cool‐season grasses with the birdsfoot trefoil cultivar Norcen for herbage mass, botanical composition, and cattle (Bos taurus) grazing preference under a rotational stocking. Experiments were established at Lake City and Chatham, MI, in 1994. Binary mixtures were grazed for 2 yr with beef or dairy cows three times yearly at predetermined periods from spring to fall. Total herbage dry mass production ranged from 3 to 10 Mg ha−1 yr−1 over two years and locations. The grass fraction in binary mixtures was 327 to 946 g kg−1 in swards over two years and locations. Perennial ryegrass (Lolium perenne L.) failed to persist at Lake City, probably due to less consistent snow cover. Birdsfoot trefoil fraction was highest in binary mixtures with smooth bromegrass (Bromus inermis Leyss) and timothy (Phleum pratense L.). Binary mixtures with orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) produced the highest herbage biomass but were less preferred by grazing animals while binary mixtures with timothy and smooth bromegrass were associated with the highest apparent herbage utilization at both locations (84–100%).
Canopy Light Environment and Yield of Narrow‐Row Cotton as Affected by Canopy Architecture
Authors: Reta‐Sánchez David G. , Fowler James L.
Published: July 2010

Alterations of plant architecture in narrow‐row cotton (Gossypium hirsutum L.) using management and genetic strategies to improve light penetration into the canopy may increase crop yields. The objective of this study was to quantify how plant architecture changes affect light penetration into the canopy, yield, and yield components of narrow‐row cotton. The study was conducted on a Glendale clay loam soil (fine montmorillonitic, thermic Typic Torrert). Two field experiments were established on 0.76‐m rows in 1995 and 1996. Treatments consisted of the following plant architecture modifications: pruning leaves throughout the canopy, mechanical topping, trimming of branches, and temporarily opening the canopy during boll production. Photosynthetic photon flux density (PPFD) interception and PPFD penetration into the canopy were measured when the canopy was fully developed. Seed‐cotton yield and yield components by plots, fruiting positions, and strata by four main‐stem node groups were obtained. Early canopy modifications simulating plant characteristics such as reduced plant height, short branches, and modified leaf shape increased light availability at the medium and upper part of the canopy. Modified canopy treatments grown at 97 000 plants ha−1 reached high PPFD interception (90–97%), with leaf area index from 3.7 to 5.2. Treatments to increase light distribution in the canopy while maintaining a high PPFD interception increased seed‐cotton yield by 34% due to a 26% increase in number of bolls per square meter. A canopy light environment improved during the first 3 wk after canopy closure (86–107 d after sowing) increased number of bolls per square meter by 33%.
No‐Till Establishment of Rhizoma Peanut
Authors: Williams M. J. , Valencia E. , Sollenberger L. E.
Published: July 2010

Planting rhizoma peanut (Arachis glabrata Benth.) directly into grass sod may be practical for producers [e.g., cow‐calf (Bos taurus) production, low maintenance roadside or turf situations, wildlife feed, etc.] who do not need the feed value of pure rhizoma peanut stands. The objective of this study was to determine the effects of planter (no‐till vs. conventional sprig planter), ground preparation (undisturbed sod vs. rotovated), planting date (winter vs. summer), and herbicide (glyphosate [N‐(phosphonomethyl) glycine] vs. none) on the establishment and survival of rhizoma peanut. Planter type had no effect on rhizoma peanut establishment. In 1996 there was a planting date × ground preparation × herbicide interaction due to the winter‐planted, rotovated plots without herbicide (0.9 sprouts m−2) having lower sprout counts than any other rotovated treatment at either planting date (>3.4 sprouts m−2). In 1997, only the main effects of planting date and ground preparation and their interaction affected sprout emergence and survival. Final sprout counts were positively correlated with bare ground (r = 0.37). Herbicide suppressed grass in the winter planting only, but did not consistently reduce total ground cover due to increased annual forb cover. There was a ground preparation × herbicide interaction on ground cover of rhizoma peanut (rotovated + herbicide, 22%; rotovated no herbicide, 13%; herbicide not rotovated, 5.9%; and no herbicide not rotovated, 2%). This study indicates that producers can select establishment practices for rhizoma peanut plantings that meet their production goals (clean cultivation establishment for hay production or dairy cattle grazing and sod planting without herbicide for less intensive situations).
Rice Response to Phosphorus Fertilizer Application Rate and Timing on Alkaline Soils in Arkansas
Authors: Slaton Nathan A. , Wilson Charles E. , Norman Richard J. , Ntamatungiro Sixte , Frizzell Donna L.
Published: July 2010

Phosphorus deficiency of rice (Oryza sativa L.) in Arkansas occurs almost exclusively on alkaline silt loam soils. Phosphorus‐deficient rice has been observed where P fertilizer was applied near the time of seeding, which suggests that fertilizer P is rapidly converted to a form not available to flooded rice on alkaline soils. The primary objective of this study was to evaluate rice response to P fertilizer applied at different times. Field studies were established in six commercial rice fields. Three rates of P (9.8, 19.6, and 39.1 kg P ha−1) were applied at four different times during the growing season including preemergence (PRE), preflood (PF), 5 to 10 d postflood (POF), or at midseason (MS) and compared with an untreated control. Significant grain yield increases were measured at two of the six locations. Grain yields were maximized by application of 19.6 kg P ha−1 at the two highly responsive sites with yield increases of 24 to 41%. Application of P fertilizer PRE, PF, and POF were superior to MS applications, which were not different from the control. Phosphorus concentration in harvested grain was not affected by time or rate of P fertilizer application. The average grain P content represented 56 to 75% of the total P in the aboveground portion of rice at physiological maturity. Broadcast applications of P fertilizer to the soil surface between seeding and active tillering were equally effective at increasing rice yields and optimizing P uptake on the P deficient soils.
Spatial Growth and Nitrogen Uptake Variability of Corn at Two Nitrogen Levels
Authors: Katsvairo Tawainga W. , Cox William J. , Van Es Harold M.
Published: July 2010

Crop measurements that predict spatial yield variability and correlate with yields may facilitate development of variable N rate management. We evaluated growth, N concentration, and N uptake of two corn (Zea mays L.) hybrids at two N rates (130 vs. 185 kg ha−1 at two sites and manure vs. manure + 55 kg N ha−1 at another site) in 2000 (wet) and 2001 (dry) to help explain corn spatial yield variability that existed at five of six site–years. Biomass, N concentration, and N uptake mostly had no spatial variability at the sixth leaf stage (V6), silking (R1), and physiological maturity (R6). Plant height at V6, which had spatial variability at four site–years, correlated with yields at two sites (0.55 and 0.66) in 2000 and at one site (0.56) in 2001. Plant height at V10, which had spatial variability at all sites, correlated with yields at all sites (0.50–0.64) in 2000 but at only one site (0.69) in 2001. Nitrogen uptake at R6, which correlated with yields at all sites in 2000 (0.25–0.58) and 2001 (0.34–0.65), did little to explain the N response within sites. Stalk NO3–N concentrations showed no spatial variability, despite spatial variability for residual soil NO3–N concentrations at all site–years. Residual soil NO3–N, which had distinct zones of high concentrations in the upper 30 cm in 2001, may provide more useful information than crop measurements for development of variable N rate management.
Relationship among Crop Grain Yield, Topography, and Soil Electrical Conductivity Studied with Cross‐Correlograms
Authors: Kravchenko A. N. , Thelen K. D. , Bullock D. G. , Miller N. R.
Published: July 2010

The characterization of factors causing spatial variability of crop yield is a necessary prerequisite for successful implementation of precision agriculture. However, the existing tools for a quantitative description of these factors and their relationship to crop yield lack effectiveness and completeness. This study proposed to use the area under an experimental cross‐correlogram as a single parameter to describe the spatial correlation between crop yield and topographical and soil variables. The developed parameter conveniently combines the information on the magnitude of the cross‐correlogram values, the correlation range, and the cross‐correlogram shape. We used the developed parameter to quantify the relationships between corn (Zea maysL.) and soybean [Glycine max(L.) Merr.] yield and soil apparent electrical conductivity (EC) and elevation in their spatial context. Variations in the strength and direction (positive vs. negative) of the relationship between yield and soil EC were found to be related to the amounts of precipitation observed early in the growing season. Crop yield was strongly and negatively related to EC in years with high March precipitation and positively or weakly negatively related to EC in years with low or moderate March precipitation. Results also indicated that in years with high March precipitation, the cumulative spatial correlation between soybean yield and EC was stronger than that between corn yield and EC. The range of significant spatial correlations between crop yield and elevation was related to the precipitation data as well as to the soil characteristics of the fields, such as soil organic matter content.
Parameters for Predicting Giant Foxtail Cohort Effect on Soybean Yield Loss
Authors: Conley Shawn P. , Binning Larry K. , Boerboom Chris M. , Stoltenberg David E.
Published: July 2010

Quantifying the effect of cohort emergence time on weed–crop interference is critical for development of accurate crop yield loss models. Therefore, research was conducted to assess late‐season weed shoot biomass, weed density and cohort emergence time, weed relative leaf area, and weed relative volume as predictors of soybean [Glycine max (L.) Merr.] yield loss. Field experiments were conducted in 1999 and 2000 at the University of Wisconsin Arlington Agricultural Research Station near Arlington, WI. The main‐plot effect was giant foxtail (Setaria spp.) cohort emergence time at VE, VC, V1, and V3 soybean. The subplot effect was giant foxtail density at 0, 4, 16, 36, and 64 plants m−2. Linear and nonlinear regression equations were used to describe soybean yield loss based on measurements of giant foxtail shoot biomass, volume, leaf area, and density and cohort emergence time. Based on weed density and cohort emergence time, coefficient estimates used to describe soybean yield loss were similar between years. Based on weed relative leaf area, coefficient estimates for the giant foxtail damage coefficient (qL) and maximum soybean yield loss (mL) differed between years. Based on weed relative volume, coefficient estimates for the giant foxtail damage coefficient (qV) and maximum soybean yield loss (mV) were similar between years. Soybean yield loss increased linearly as giant foxtail shoot biomass increased. The stability of the density and cohort emergence time coefficients and the weed relative volume coefficients indicated these parameters may prove more useful that weed relative leaf area for predicting soybean yield loss.
Reduction of High Soil Test Phosphorus by Corn and Soybean Varieties
Authors: Eghball Bahman , Shanahan John F. , Varvel Gary E. , Gilley John E.
Published: July 2010

Soils with high levels of P can contribute to excess P in runoff and subsequently pollute the surface water. Excess P in the soil can be removed from the system by harvesting crops. The objectives of this study were to evaluate corn (Zea mays L.) P removal effects on soil P reduction, and to evaluate various corn hybrids and soybean [Glycine max (L.) Merr.] varieties for differences in grain P concentration and P removal. Soil with varying P levels as a result of annual or biennial beef cattle (Bos taurus) feedlot manure or compost application was cropped to corn for 4 yr without any P addition. In other studies under various water and N regimes, corn hybrids and soybean varieties were evaluated for grain P concentration and P removal. Four years of corn production without P addition lowered surface soil (0–15 cm) extractable P level (Bray and Kurtz no. 1) from 265 mg kg−1 to 171 mg kg−1 in the biennial N‐based compost treatment. Based on a decay equation, it would have required 10 yr of corn P removal to lower the soil P level to the original 69 mg kg−1 that existed before treatment application. The rate of decrease in extractable soil P was greater when soil P was higher and reduced with decreasing soil P level. Most of the P in the plants was absorbed from the 0‐ to 15‐cm soil depth since no significant reduction in soil P level was observed from 1996 to 1999 in the 15‐ to 30‐cm soil depth. Across 2 yr, there was as much as 54% difference among corn hybrids for grain P removal. The differences in P concentrations among corn hybrids indicated that hybrids could be selected for low P uptake when lower P level in ethanol production by‐product or in animal ration and subsequently in manure is desired. Soybean grain P concentration was nearly twice that for corn but grain P removal was less for soybean than for corn. Crop P removal can significantly reduce soil P level with time.
Modeling Soil Water and Solute Transport—Fast, Simplified Numerical Solutions
Authors: Ross P. J.
Published: July 2010

Modeling of water and solute transport in soils is increasingly important in hydrology and agriculture, but there remain many gaps and unresolved issues. One of these, the speed and robustness of numerical solutions, is important in large‐scale and stochastic modeling. A fast method was developed for solution of the Richards equation for water transport. Brooks–Corey soil hydraulic property descriptions were used with water content as the dependent variable in unsaturated regions and pressure head in saturated regions. Central time weighting was used in unsaturated conditions to improve accuracy and fully implicit weighting in saturated conditions to improve stability. Water fluxes were calculated using matric flux potentials combined with a novel spatial weighting scheme for the gravitational component. Flow across soil property interfaces was calculated by equating fluxes to and from the interface. Results on a test problem involving rainfall, surface ponding, evaporation, and drainage over 400 h showed the new method to be an order of magnitude faster and more robust than an iterative scheme typifying current practice. Execution time for the test problem with <3% error was 0.006 s on a 166‐MHz personal computer. Solutions for solute transport described by the advection–dispersion equation were obtained concurrently without substantial increase in execution time by assuming average water fluxes over several steps of the water transport solution. The methods presented here should also be applicable to two‐ and three‐dimensional problems.
Amendments and Construction Systems for Improving the Performance of Sand‐Based Putting Greens
Authors: Ok Chang‐Ho , Anderson Stephen H. , Ervin Erik H.
Published: July 2010

Physical and chemical properties of root zone mixes and methods of green construction are important considerations for improving turfgrass quality for putting greens. This study compared ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) performance as affected by three root zone construction systems with three amendments (sand, peat, and zeolite). The objective of this study was to determine if an amended California construction system would improve green performance during establishment (1998–1999) and maturation (2000–2001). Three treatments were tested: California (100% sand), USGA (90% sand and 10% peat, v/v), and California‐Z (85% sand and 15% zeolite, v/v). Treatments were arranged in a randomized complete block with four replicates. Physical and chemical properties of the root zone and bentgrass performance were compared for the treatments. The California‐Z treatment had the highest saturated hydraulic conductivity and field infiltration rate and the lowest bulk density. It also had the highest cation exchange capacity and plant available nutrient concentrations among the three treatments. The California‐Z treatment produced bentgrass quality and color during green establishment and maturation that were equal to or higher than the California treatment and consistently higher than the USGA treatment. The addition of an inorganic amendment to the California system improved physical and chemical properties of the root zone and improved quality and color of bentgrass during green establishment. During green maturation, creeping bentgrass in the California‐Z treatment was equal (6 of 15 sampling dates) or 20% higher (9 of 15 dates) in quality compared with the California system.
Persistence and Spread of Kura Clover in Cool‐Season Grass Pastures
Authors: Cuomo G. J. , Peterson P. R. , Singh A. , Johnson D. G. , Head W. A. , Reese M. H.
Published: July 2010

Legumes can improve productivity and quality of cool‐season grass pastures but often do not persist under grazing. In May of 1997 and 1998, field experiments were planted in cool‐season grass pastures near Morris, MN, to evaluate establishment and persistence of kura clover (Trifolium ambiguum Bieb.) compared with alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), and red clover (Trifolium pratense L.) under grazing pressure in the north‐central USA. Each spring, from planting through 2002, stands of these legumes were evaluated for persistence. Pastures were grazed five or six times per growing season for 12‐h grazing periods by lactating dairy cows (Bos taurus L.) over the duration of the study. Kura clover stand density was low relative to the other species in the growing season after establishment but increased and maintained denser stands in subsequent growing seasons. Alfalfa, birdsfoot trefoil, and red clover initially developed stands greater than 30% of the sward and remained constant or increased for two (1998 planting) or four (1997 planting) growing seasons before declining. In the spring of 2002, stands were greater (P > 0.001) for both planting years for kura clover (90%) compared with alfalfa, birdsfoot trefoil, and red clover (41, 28, and 9%) when averaged across planting years, respectively. Kura clover stands spread 60 (1998 planting) to 90% (1997 planting) over the length of the study. Stands of other species did not spread. In these studies, kura clover was able to compete, persist, and spread under intermittent grazing and has the potential to be an important and persistent component of cool‐season grass pastures in the north‐central USA.
Evaluation of Microlysimeters Used in Turfgrass Evapotranspiration Studies Using the Dual‐Probe Heat‐Pulse Technique
Authors: Bremer Dale J.
Published: July 2010

Microlysimeters (ML) are commonly used in turfgrass evapotranspiration (ET) studies. No standard exists for ML, which has resulted in multiple designs that may affect soil moisture. The effects of ML design on volumetric soil water content (θv) were investigated with the dual‐probe heat‐pulse (DPHP) technique. DPHP sensors were installed at 5, 15, and 25 cm in the ambient soil profile and in three designs of ML: (i) 15‐cm diam. by 30‐cm, mesh base, soil fill (MSL); (ii) 15‐cm diam. by 30‐cm, Plexiglass base (one drainage hole), soil fill (PSL); 3) 10‐cm diam. by 20‐cm, mesh base, soil (intact cores) (MSNL). Sleeves and a 5‐cm layer of gravel were placed in MSL and PSL. DPHP estimates of θv revealed that soils consistently dried faster in MSL and PSL than in the ambient profile, probably because of higher leaf area index (LAI) and biomass in MSL and PSL than in surrounding turf, limitations of roots to extract soil water only from mL, and evaporation through open bases. In MSNL, θv was similar to but may have been in hydraulic contact with ambient soils. The correlation was good between θv determined by DPHP and θv determined by gravimetric methods; DPHP sensors on average (all ML) measured θv to within 0.025 m3 m−3 of gravimetric estimates. ET estimates varied significantly among ML and were strongly correlated to LAI and aboveground biomass (r = 0.85). Results suggest that establishment–maintenance of similar LAI and biomass between ML and surrounding turf may be more important than ML design in providing accurate ET estimates, and bases should be sealed during ET measurements to prevent hydraulic contact with soil, drainage, or evaporation through bases.
Effect of Soil and Topographic Properties on Crop Yield in a North‐Central Corn–Soybean Cropping System
Authors: Jiang P. , Thelen K. D.
Published: July 2010

Understanding the variability of soil and landscape properties and their effect on crop yield is a critical component of site‐specific management systems. The objectives of this study were to identify yield‐limiting soil properties and to investigate the relationship between soil properties and topographical variables and their relationship to crop yield. Two corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] fields in Michigan were sampled, and 23 soil properties from the top two horizons up to 50 cm deep were examined. Corn and soybean yield data were collected from 1996 through 2001 using a combine yield monitor. A multivariate statistical model, principal‐component analysis (PCA), was used to identify important soil properties based on their potential to affect crop yield. Soil properties identified by PCA to be important to yield and two topographic variables, elevation and slope, derived from a high‐resolution digital elevation model (DEM), were investigated for their effect on crop yield. Correlation analysis was used to examine the relationship between soil properties and field topography and between crop yield and both soil and topographical variables. Principal‐component analysis was useful in identifying important soil variables. Slope and very fine sand content were two major yield‐limiting factors during the study period. Other soil variables such as base saturation, pH, clay content, and elevation were helpful in explaining yield variability. The combined effect of both soil and topography varied by year and explained 28 to 85% of the observed yield variability.
Diagnostic Tests for Site‐Specific Nitrogen Recommendations for Winter Wheat
Authors: Bundy Larry G. , Andraski Todd W.
Published: July 2010

Wheat (Triticum aestivum L.) yields can be limited by both inadequate and excessive N availability. This study evaluated several diagnostic tests for predicting the economic optimum N rate (EONR) for winter wheat at 21 site‐years. Tests included soil NO3 (90 cm) at three sampling times [preplant, predormant, and at Zadoks Growth Stage (GS) 25—five tillers], UV absorbance of NaHCO3 soil extracts (30 cm) at preplant, and plant N concentration, N uptake, and chlorophyll meter measurements taken at GS 30 (pseudo stem initiation). All samples were obtained from the control plots (no N fertilizer). Yield response to applied N fertilizer was positive for 13 site‐years (EONR of 34 to 168 kg ha−1), negative for three site‐years, and not significant for five site‐years. Nitrogen additions to sites with high soil NO3 levels resulted in yield reductions up to 30%. The strongest relationship among diagnostic tests and EONR was preplant soil NO3 content at the 90‐cm depth (R2 = 0.53). The combination of soil NO3–N content at GS 25 plus N uptake at GS 30 was also strongly related to EONR (R2 = 0.58). Nitrogen rate recommendations for wheat adjusted for preplant soil NO3 contents >56 kg ha−1 avoided excessive N applications at 11 of 21 sites, thereby increasing economic gains by $1 to $110 ha−1 (median $17) due to reduced fertilizer costs and avoiding yield reductions due to excessive N availability. Wheat N recommendations based on preplant soil NO3–N measurements in the 0‐ to 60‐cm depth have potential for avoiding reduced profits, lower yields, and environmental risks associated with excess N use.
Fate of Nitrogen‐15 Applied to Irrigated Acala and Pima Cotton
Authors: Fritschi Felix B. , Roberts Bruce A. , Rains D. William , Travis Robert L. , Hutmacher Robert B.
Published: July 2010

Better knowledge on the fate of fertilizer N will aid in developing effective N management strategies balancing plant requirements for optimal lint yield with environmental concerns. Field studies were initiated to determine the fate of 15N fertilizer applied to Acala (Gossypium hirsutum L.) and American Pima (G. barbadense L.) cotton. Four N regimes (56, 112, 168, and 224 kg N ha−1 corrected for residual soil nitrate N levels) were established for Acala cotton grown on a Panoche clay loam [fine‐loamy, mixed (calcareous) thermic Typic Torriorthents] and on a Wasco sandy loam (coarse‐loamy, mixed, nonacid, thermic Typic Torriorthents) in 1998, 1999, and 2000. Pima cotton was evaluated on the Panoche clay loam for the same N regimes in 1999 and 2000. To trace the fate of fertilizer N, 15N‐labeled urea was applied to microplots in selected treatments and years. Acala fertilizer use efficiency by 15N dilution (FUE–15N) averaged 49% on Panoche clay loam and 43% on Wasco sandy loam. Pima FUE–15N on the Panoche clay loam averaged 48% and was not affected by N treatment. Recovery of fertilizer N in the soil was not different between the Panoche clay loam and the Wasco sandy loam in the Acala experiments and combined across both Acala and Pima trials averaged 42%. Averaged across all experiments, more than 75% of the 15N recovered in the soil was found in the top 0.9‐m layer. The total recovery of 15N fertilizer in plant and soil averaged 89% (76–98%) across all treatments, suggesting that production practices employed in this study resulted in only small losses of fertilizer N during the season of application.
Interactive Effects of Carbon Dioxide and Nitrogen Nutrition on Cotton Growth, Development, Yield, and Fiber Quality
Authors: Reddy K. Raja , Koti Sailaja , Davidonis Gayle H. , Reddy Vangimalla Ramakrishna
Published: July 2010

The consequences of elevated carbon dioxide concentrations ([CO2]) and N nutrition on cotton (Gossypium hirsutum L.) growth, development, yield, and fiber quality were determined. Cotton cultivar NuCOTN 33B was grown in sunlit controlled environment chambers at three levels of [CO2] (180, 360, and 720 μmol mol−1) and two levels of N [continuous N throughout the plant growth period (N+) and N withheld from flowering to harvest (N−)]. Leaf N concentration decreased with increasing [CO2] under both N treatments. These low leaf N concentrations did not decrease the effect of elevated [CO2] in producing higher lint yields at both N treatments, the response being highest for plants grown at elevated [CO2] and N+ conditions. Fiber quality was not significantly affected by [CO2], but the leaf N concentrations, which varied with [CO2], had either a positive or a negative influence on most of the fiber quality parameters. Leaf N during boll maturation period had significant positive correlations with mean fiber length (r2 = 0.63), fine fiber fraction (r2 = 0.67), and immature fiber fraction (r2 = 0.65) and negative correlations with mean fiber diameter (r2 = 0.61), short fiber content (r2 = 0.50), fiber cross‐sectional area (r2 = 0.76), average circularity (r2 = 0.74), and micronafis (r2 = 0.65). It is inferred that future elevated [CO2] will not have any deleterious effects on fiber quality and yield if N is optimum. The developed algorithms, if incorporated into process‐level crop model, will be useful to optimize cotton production and fiber quality.
Ligands and Phytase Hydrolysis of Organic Phosphorus in Soils Amended with Dairy Manure
Authors: Dao Thanh H.
Published: July 2010

Information about orthophosphate and organic phosphorus (P) desorption in soil amended with animal manure is needed because a build‐up of P following repeated manure applications poses risks of offsite dissolved P discharges. An enzymatic hydrolysis and soil P desorption study was conducted to develop a novel ligand‐based phytase‐hydrolyzable P (PHP) method and quantify water‐extractable uncomplexed and complexed P forms (i.e., bioactive P) in Unicorn and Christiana soils (Typic Hapludults). Extractability of inorganic P with ligands alone (LEP) increased from 2 and 22 mg kg−1 (0.3 and 3.1 ± 0.16% total P) up to sevenfold with increasing ligand (LIGND) concentrations in the order of CDTA = EDTA > DTPA >> oxalate. The LIGNDs nullified the benefits of using an anion sink in soil P desorption measurements. Soil organic P was hydrolyzed in situ by Aspergillus ficuum (Reichardt) Henn. phytase EC 3.1.3.8, corroborating the presence of myo‐inositol phosphomonoesters including IP6. Adding CDTA and EDTA increased phytases’ efficacy and that of the PHP assay for measuring previously inaccessible complexed organic P; soil PHP increased from 2.3 and 6.4% to peak at 32.0 ± 0.7 and up to 40.8 ± 0.2% of total P in Unicorn and Christiana soils, respectively. In long‐term manure‐amended Christiana silt loam under orchardgrass–red clover stands, the LIGND‐PHP method showed that repeated manure applications resulted in soil storage of unextractable complexed PHP and a buildup of inorganic LEP. Accumulation of LEP increases risks of mobilization of bioactive P in the top 10 cm of these soils.
Simulating Seed Number in Grain Sorghum from Increases in Plant Dry Weight
Authors: Gerik T. J. , Rosenthal W. D. , Vanderlip R. L. , Wade L. J.
Published: July 2010

Simulation of seed number for crop models is important in identifying cultural practices, which enhance yield stability. Field and crop simulation studies examined the relationship between dry weight accumulation and seed number per plant to potentially improve the capability of the grain sorghum [Sorghum bicolor (L.) Moench] model, SORKAM, to simulate seed number. The best estimates of seed numbers were obtained from plant dry weight accumulated during the 360 growing degree day intervals encompassing panicle branch–spikelet formation (PBSI) and panicle elongation through anthesis (EAI). Comparison of observed vs. simulated seed numbers using SORKAM’s original equations accounted for 57% of the variation in seed number, but it underestimated high seed numbers. Accumulated plant dry weight for the PBSI and EAI intervals accounted for 49 and 64% of the variation in seed number, respectively. Simulation of seed numbers improved when the more sensitive water stress coefficient (for leaf area, WATCOle) was applied to the interval (PBSI or EAI) experiencing the highest water stress while the less sensitive water stress coefficient (for dry weight, WATCOdw) was applied to the interval experiencing the lowest water stress. The slope from the regression of observed on simulated seed numbers was 0.80 (r2 = 0.57) for SORKAM with the WATCOle switch compared with 0.59 (r2 = 0.57) in the original SORKAM model. Hence, the timing and recovery of water stress during the panicle development period was important in estimating seed number of sorghum.
Effects of Phosphorus and Potassium on Forage Nutritive Value and Quantity: Environmental Implications
Authors: Pant H. K. , Mislevy P. , Rechcigl J. E.
Published: July 2010

Management practices minimizing P application in agricultural catchments ultimately reduce P export to waters. To determine stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) response to P and K, eight rates of P and K were applied on experimental units located on Pomona fine sand (sandy, siliceous, hyperthermia Ultic Alaquods) Spodosols, and arranged in a randomized complete block design with four replicates. The forage yield was less from 39:0 (P/K; kg ha−1 yr−1) treatment than the experimental units supplied with 93 kg K ha−1 yr−1 and low P (10 and 20 kg ha−1 yr−1) in all years with exception in 1998 (i.e., the year of grass establishment), indicating efficient P utilization due to K applications. No significant differences were obtained in in‐vitro organic matter digestibility (IVOMD) from the applications of 10 kg P ha−1 yr−1 and 93 kg K ha−1 yr−1. The applications of 10 and 93 kg ha−1 yr−1 of P and K, respectively, provided efficient P utilization. Phosphorus mass balance showed that stargrass receiving 10 and 93 kg ha−1 yr−1 of P and K, respectively, removed maximum P (161% of the applied P) by uptake from soils. This may indicate the capability of stargrass to mine P from subsoils if sufficient K is supplied, and also suggests that stargrass may be useful for crop phytoremediation on P‐impacted sites. In general, this study indicates that applications of 10 kg P ha−1 yr−1 in combination with 93 kg K ha−1 yr−1 will maintain forage nutritive value and quantity, and maximize P removals by stargrass. Moreover, the supply of sufficient K appears to be crucial for efficient P utilization by forages, reducing potential adverse effects of P over‐fertilization on water quality.
Bermudagrass Management in the Southern Piedmont USA: X. Coastal Productivity and Persistence in Response to Fertilization and Defoliation Regimes
Authors: Franzluebbers A. J. , Wilkinson S. R. , Stuedemann J. A.
Published: July 2010

Productivity, quality, and persistence of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] pastures are affected by fertilization, but possible interactions with defoliation regime including animal grazing are not fully known. We evaluated three sources of fertilization with equivalent N rates [inorganic, crimson clover (Trifolium incarnatum L.) cover crop plus inorganic, and chicken (Gallus gallus) broiler litter] factorially arranged with four defoliation regimes [unharvested, cattle (Bos taurus) grazing to maintain high (4.5 ± 1.6 Mg ha−1) and low (2.5 ± 1.1 Mg ha−1) forage mass, and hayed monthly] on estimated forage dry matter production, forage and surface residue C/N ratio, and ground cover of pastures on a Typic Kanhapludult in Georgia during 5 yr. Mean annual forage dry matter production was 7.5 ± 0.7 Mg ha−1 with hay harvest but declined (1.3 Mg ha−1 yr−1) significantly with time as a result of lower precipitation. With grazing, estimated production was 8.3 ± 1.0 Mg ha−1 and did not change with time, suggesting that grazing cattle sustained forage productivity by recycling nutrients and creating better surface soil conditions. Coastal bermudagrass as a percentage of ground cover (initially 81%) declined 5 ± 2% yr−1 with unharvested and grazing to maintain low forage mass, declined 3 ± 1% yr−1 with haying, and remained unchanged (−1 ± 1% yr−1) with grazing to maintain high forage mass. Pastures with high forage mass were more productive than with low forage mass (9.2 ± 1.6 vs. 7.5 ± 1.1 Mg ha−1) from a forage sustainability perspective, primarily by avoiding encroachment of undesirable plant species.