bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluxes of Ammonia Over an Alfalfa Field1
Authors: Dabney Seth M. , Bouldin David R.
Published: July 2010

The cycling of atmospheric ammonia has significance to both agricultural and global N balances. Field data concerning the magnitude of ammonia exchange is not available for many crops and ecosystems. The vertical flux of gaseous plus particulate ammonia above an extensive alfalfa (Medicago sativaL.) canopy was measured periodically over a one‐yr period. The gradients of mean wind speed, mean temperature, and mean ammonia concentration were simultaneously determined during one‐h runs and were combined to estimate average ammonia flux. Total ammonia was determined using a treated filter paper sampling technique. A diurnal pattern of ammonia evolution during the day and deposition at night was observed. At least a portion of the deposition at night was due to the influence of a local ammonia source. The magnitude of the fluxes was small. The nighttime observations yielded an estimated yearly gain of 1.6 kg N ha−1. The daytime observations, excluding periods of 10 days for each of three hay harvests yielded an estimated annual loss of 1.2 kg N ha−1. During the three periods of hay harvesting an additional 2.3 kg N ha−1was estimated to have been lost. The data indicate ammonia exchange over the alfalfa field was of little importance to the agricultural N balance, but has relevance to understanding global N cycling.
Diurnal and Seasonal Variation in Dinitrogen Fixation (Acetylene Reduction) Rates by Field–Grown Soybeans1
Authors: Denison R. F. , Sinclair T. R.
Published: July 2010

No data exist that represents in situ, continuous observations under field conditions of changes in dinitrogen fixation potential through diurnal cycles. Acetylene reduction responses of soybean [Glycine max(L.) Merr.] plants to changes during the diurnal cycle and during seasonal developmental changes were monitored using a continuous flow system with very low acetylene concentration. These data were used to assess the relative effects on acetylene reduction rates of environmental and plant ontogeny variables. During the diurnal cycle, acetylene reduction rates generally peaked late in the afternoon and then declined through the night. However, the night rates did not fall below half of the daily maximum. Within individual days, rates were more closely correlated with soil temperature than with photosynthetically active radiation. A consistent link was not observed between acetylene reduction rates and any particular stage of ontogeny. These results, and a reexamination of published reports, suggest that dinitrogen fixation rate in soybeans is not closely coupled to current photosynthetic rates under field conditions.
Grain Sorghum Yield and Yield Component Response to Timing and Number of Irrigations1
Authors: Hooker M. L.
Published: July 2010

Efficient use of irrigation water becomes more essential as the availability of this resource declines. Research evaluating the effect of timing and number of irrigation water applications on yield and yield components of grain sorghum [Sorghum bicolor(L.) Moench] was initiated in 1976. The experiment was conducted on a Richfield silty clay loam (fine, montmorillonitic, mesic, Aridic Argiustoll). Irrigation water treatments were applied at preplant (PP), PP + growth differentiation (GD), PP + boot (B), PP + GD + B growth stages, and PP + initiation of irrigation at 50% available soil moisture. Maximum grain yields were consistently achieved when three or more irrigations were applied. Two irrigation water applications reduced grain yields, but the timing of the in‐season water application (GD or B) had no effect on yields. Yield components were evaluated in 1982 and 1983 to determine what effect timing of water application had on these parameters. Irrigation at GD resulted in a greater number of kernels per head and per unit area, whereas applications at B increased seed weight. Head weight showed no response to the timing of water applications, suggesting that the same amount of dry matter was accumulated in the head whether water was applied at GD or B. Therefore, producers of grain sorghum have a broader time period over which to apply limited quantities of irrigation water without reducing grain yield than is reported in most literature. However, if maximum yield potential is desired, it is necessary to have adequate water available to the plant at GD to set the maximum number of kernels.
Responses of Sugarbeet to Deficit, High‐Frequency Sprinkler Irrigation. II. Sugarbeet Development and Partitioning to Root Growth1
Authors: Hang An N. , Miller D. E.
Published: July 2010

The water requirement of sugarbeet (Beta vulgarisL.) has been studied extensively throughout the western states. However, there is limited information about the response to prolonged deficit irrigation, particularly on sandy soils with low water‐holding capacity. The present study was conducted to determine the effect of deficit, daily sprinkler irrigation on rates and growth characteristics of sugarbeet grown on loam and sandy soils (Xerollic Camborthids and Xeric Torripsamments, respectively). On loam soil, irrigation rates less than estimated evapotranspiration (Et) did not significantly affect the leaf blade petiole or top/root ratio until 4 to 8 weeks after they were initiated. Afternoon wilting of leaves was observed at the 15, 17, 39, and 41% Et irrigation rates, but they regained turgor during the night. After about 8 weeks of 15 and 17% Et irrigation rates specific leaf weight increased significantly. Top and root growth rates increased as the amount of water applied increased. Partitioning to root growth was maximum (75.8%) at irrigation rates equivalent to about 58% estimated Et. On sandy soil, irrigation rates less than estimated Et depressed growth, and shortened leaf life cycle. Leaf blade petiole and top/root ratio were not affected until after 6 weeks of deficit irrigation. Low irrigation rates depressed leaf expansion and resulted in very high specific leaf weights. Top and root growth rates increased with water application up to rates equivalent to 100% estimated Et. Maximum partitioning to root growth of 74.4% occurred at 100% irrigation rate. Increasing irrigation to 115% estimated Et gave no increased benefits. In both soil types, leaf blade petiole and top/root ratios were generally affected later and much less by drought than were leaf area, specific leaf weight and crop growth rate.
Alfalfa Dry Matter and Nitrogen Production, and Fertilizer Nitrogen Response in Legume‐Corn Rotations1
Authors: Hesterman O. B. , Sheaffer C. C. , Barnes D. K. , Lueschen W. E. , Ford J. H.
Published: July 2010

Nondormant alfalfa (Medicago sativaL.) germplasms have been selected for increased storage of reduced N in roots and crowns. It is important to learn how this improved germplasm will affect yield of a subsequent nonlegume crop in a cropping sequence. Our objectives were to (i) compare effects of two harvest systems on the forage yield, quality, and N incorporated for the nondormant experimental ‘MN ROOT N’ population and the moderately dormant cultivar ‘Saranac AR’; and (ii) evaluate effects of previous cropping and fallow treatments on grain yield and N response of a subsequent corn crop. Field studies were conducted in 1982 and 1983 at four Minnesota locations on a Hubbard loamy sand (Udorthentic Haploboroll), Webster silt loam (Typic Haplaquoll), Normania clay loam (Aquic Haplustoll), and Webster clay loam (Typic Haplaquoll). First‐year rotation components included seeding year alfalfa, corn (Zea maysL.), soybean [Glycine max(L.) Merr.], and fallow. The second‐year component was corn. Alfalfas were subjected to two harvest systems. The two alfalfas did not differ in total forage production, but Saranac AR tended to have higher crude protein and digestible dry matter concentrations than MN ROOT N. MN ROOT N had greater root dry matter yield and N concentration than Saranac AR. Total N incorporated was 14% greater for MN ROOT N than Saranac AR under the one‐cut system and 41% greater under the three‐cut system. Total N incorporation was 84% greater for the one‐cut (157 kg ha−1) than for the three‐cut (85 kg ha−1) system. Differences in second‐phase corn yields were correlated with differences in first‐phase alfalfa N incorporation at one of four locations. Alfalfa was a more effective first‐phase rotation crop for corn than corn, soybean, or fallow. With no N applied, second‐phase corn grain yields were 84% greater after first‐phase alfalfa (6.8 M g ha−1), 33% greater after soybean (5.1 Mg ha−1), and 61% greater after fallow (6.1 Mg ha−1) than after corn (3.7 Mg ha−1). Alfalfa cultivars and harvest systems affected the yield of a subsequent corn crop; however, harvest system effects were greater.
Winter Legumes as a Nitrogen Source for No‐Till Grain Sorghum1
Authors: Hargrove W. L.
Published: July 2010

Because winter legume cover crops may provide significant quantities of N while conserving soil and water resources, the role of legumes in conservation tillage production systems warrants renewed attention. The objectives of this study were (i) to determine the N contribution of several legumes to a subsequent crop of grain sorghum [Sorghum bicolor(L.) Moench] under no‐tillage management and (ii) to determine the influence of legume cover crops on soil fertility status. A field experiment was conducted in which four winter legumes, one nonlegume, and a no cover crop treatment were studied over a 3‐yr period. In addition, four fertilizer N rates (0, 28, 56, and 112 kg N ha−1) were applied to no‐till grain sorghum. Grain sorghum did not respond to fertilizer N when following a legume cover crop but responded to as much as 99 kg N ha−1when following a nonlegume cover crop or no cover crop. A mean estimate of 72 kg N ha−1was obtained for the fertilizer N replaced by the legume. The effects of the legume cover crops on soil fertility status included: (i) a lower pH, (ii) a redistribution of K+to the soil surface from deeper in the soil profile, and (iii) a lower C/N ratio in soil organic matter. Since fertilizer N represents a sizeable portion of the fossil fuel energy required for nonleguminous row crop production, the estimated N contribution of legume cover crops represents a significant energy savings, enhancing the conservation value of a no‐tillage production system.
A Nitrogen and Water Response Surface for Sprinkler‐Irrigated Broccoli1
Authors: Beverly R. B. , Jarrell W. M. , Letey John
Published: July 2010

Farmers typically apply large amounts of both N and water in commercial vegetable production. As costs of both inputs increase, and with mounting concern over nitrate leaching and non‐point source water pollution, the need for information on optimal management of both resources grows. We investigated the combined effects of five N application rates (0, 87, 190, 255, and 331 kg ha−1) and a continuous irrigation variable (1.14 to 32.9 cm of water, or 0.05 to 1.52 times net pan evaporation) applied by a line‐source sprinkler system on broccoli (Brassica oleraceaL., Botrytis group) growth rates and yield. Growth rates generally increased with both water and N treatments, although some interactions emerged. Harvested fresh weights continued to increase throughout the range of treatments, applied, with maximum yields in excess of 20 Mg ha−1. Yield (Mg ha−1) responded to N (kg ha−1) and water applied following seedling establishment (cm) according to the equation Y−1.03 + 0.0498 N− 8.73 × 10−5N2+ 1.23 × l0−3NW+ 0.272 W− 8.20 × 10−3W2, where Yis yield, Nis nitrogen, and Wis water applied after seedling establishment. Analysis of the resulting response surface indicated that under these conditions of frequent sprinkler irrigation (approximately twice weekly), relatively low N rates (140 kg ha−1) provided the lowest combined N and water cost for 10 Mg ha−1) yield. Further, yields increased with higher N and water rates, although quality must also be considered
Carbon Dioxide Partial Pressure in Lysimeter Soils1
Authors: Robbins Charles W.
Published: July 2010

The carbonate chemistry portion of mechanistic salinity models is generally the weak link in describing salt reactions in soils. This is primarily due to a lack of available soil atmosphere CO2data. Carbon dioxide concentrations were measured at 0.25, 0.50, and 0.75 m depths in 0.30 m diam lysimeters containing 1.0 m of sodic soil. Four non‐cropped treatments included a check, gypsum, fresh manure, and chopped alfalfa irrigated weekly with 70 mm (5.0 1) of tap water (EC=0.7 and SAR=1.7). Six cropped treatments included barley (Hordeum vulgare), alfalfa (Medicago sativaL.), Sordan [Sordan is a trade name for a sorghum (Sorghum bicolor), sudangrass (Sorghum sudanesehybrid], Sordan + leaching, cotton (Gossypium hirsutumL.), and tall wheatgrass (Agropyron elongatum). The cropped lysimeters were irrigated at 1.25 times the consumptive use since the previous irrigation (0.20 leaching fraction). Soil PCO2values were decreased by the gypsum treatment and increased by all other treatments as compared to check. Cotton and barley had the lowest PCO2values for the cropped treatments and Sordan had the highest (frequently above 16 kPa). The PCO2levels were affected by applied organic matter source, crop, plant growth rate, irrigation water application and leaching.
Plant Interaction Among Poa Annua, Poa pratensis, and Lolium perenneTurfgrasses1
Authors: Brede A. D. , Duich J. M.
Published: July 2010

Annual bluegrass (Poa annuaL.) Kentucky bluegrass (Poa pratensisL.), and perennial ryegrass (Lolium perenneL.) differ in their competitive abilities. To properly maintain stands of these species, turfgrass managers need specific information on how these grasses interact with one another and what conditions favor the growth of one species over another. The purpose of this study was to determine the effects and locations (above vs. below ground) of plant interaction among these turfgrasses under field conditions. Furthermore, information was sought on the effects of environmental variables on the competitive potential of these grasses. Plant interaction was studied by means of partitioned boxes, installed within a mature sod environment in the field. Species pairs were established in alternating chambers within the apparatus and were evaluated after 1 yr of growth. Below‐ground partitions were used to confine the interaction to aboveground in one apparatus, and vice versa in another. Interspecific interaction was significant, both above and below ground, even though a relatively close mowing height (3.1 cm) and seemingly ample nutrients and water were supplied. All three species responded to interspecific interaction with reductions in root and shoot parameters. Competitive ability of perennial ryegrass was generally greatest below the ground, whereas Kentucky and annual bluegrass excelled above the ground. Tillering rate was used to assess the competitive potential of the three species under establishment conditions. Relative tillering rate, measured in the field via the growth of individual, transplanted shoots, generally increased with increasing temperature, daylength, and precipitation. Annual bluegrass had the highest rate of tillering of the three species during early autumn, whereas perennial ryegrass had the highest rate during early summer. Plant interaction among these species was characterized as the summation of their ability to proliferate tillers under establishment conditions and their ability to compete above and below ground under dense, solid‐stand conditions.
Corn and Soybean Yield Response to Crop Residue Management Under No‐Tillage Production Systems1
Authors: Wilhelm W. W. , Doran J. W. , Power J. F.
Published: July 2010

Crop residues (stover) have many potential uses by society: food, feed, shelter, fuel, and soil amendment. Use of residues for purposes other than as a soil amendment may have serious negative consequences on crop productivity. This study was conducted to investigate the yield response of continuous corn (Zea maysL.) and continuous soybean [Glycine max(L.) Merr.] to removal or addition of crop residues under no‐tillage management. The study was conducted near Lincoln, NE, on a Crete‐Butler silty clay loam (fine, montmorillonitic, mesic Pachic Arguistoll‐Abruptic Argiaquoll) with 1 to 2% slope. Crop residue was collected and weighed immediately after harvest in autumn. Quantity of residue to be returned to each treatment (0, 50, 100, or 150% of that produced) was calculated and uniformly spread over the plot area (12.2 by 12.2 m) by hand. Corn and soybean were planted into the established residue levels with no tillage the following spring. Data were collected on soil water, soil temperature, and grain and residue yield. A positive linear response was found between grain and stover yield and amount of residue applied to the soil surface. Each Mg ha−1of residue removed resulted in about a 0.10 Mg ha−1reduction in grain yield and a 0.30 Mg ha−1reduction in residue yield. Quantity of applied residue accounted for 81 and 84% of the variation in grain yield of corn and soybean, respectively, and 88 and 92% of the variation in residue yield. Amounts of stored soil water at planting were closely associated with quantity of residue applied the previous year. Differences in total available water (soil storage at planting plus rainfall) accounted for approximately 70% of the yield variation associated with the residue treatments. Soil temperature (50‐mm depth) and total available water accounted for nearly the same amount of variation in yield (80 to 90%) as quantity of residue, emphasizing the importance of these factors in evaluating response of crops to residue‐management practices. Residue removal reduced grain and residue yields by amounts equal to 10 and 30%, respectively, of the quantity of residue removed. Residue effects on crop yield were induced mainly through changes in soil water and soil temperature.
Interactive Effects of Nitrogen and Water Stresses on Water Relations of Field‐Grown Corn Leaves1
Authors: Bennett J. M. , Jones J. W. , Zur B. , Hammond L. C.
Published: July 2010

Water and N stresses often limit corn (Zea maysL.) grain yields. Although the effects of either water or N stress on crop growth and development, physiology, and yield have been widely studied, relatively little information is available on the interactive effects of these stresses when imposed in combination. The objective of this study was to define and evaluate the interactive effects of water and N stresses on leaf water potential components, transpiration rate, and stomatal resistance of field‐grown corn leaves. Corn grown on a Kendrick fine sand soil (loamy, siliceous, hyperthermic Arenic Paleudult) was subjected to two water management treatments (optimal irrigation, and a 10‐day water stress period, which immediately preceded 50% silking). Within each water management treatment, two N levels (low, 62 kg ha−1; high, 275 kg ha−1) were imposed. During the water stress period, both midday and diurnal measurements of leaf water potential (ΨL)leaf osmotic potential (Ψτ), leaf turgor potential (ΨP), leaf transpiration, and leaf diffusive resistance were determined on combinations of the water and N stress treatments. Although high‐N plants attained similar or slightly lower ΨLthan low N plants as a result of the water stress, high‐N plants maintained lower stomatal resistances at the lower ΨL. High‐N plants also extracted more water from depths below 0.3 m in the soil profile compared with the low‐N plants. Lower Ψτas ΨLdeclined resulted in higher ΨPin high‐N plants, which was probably responsible for the lower stomatal resistances and higher rates of transpiration that were observed. Lower Ψπof the water‐stressed, high‐N plants could have resulted in the more efficient extraction of water from the soil profile. We conclude that the high‐N plants were affected less by the water stress than low‐N plants as evidenced by the maintenance of ΨPopen stomata, and higher rates of individual leaf transpiration despite similar reductions in ΨLduring periods of low soil water availability.
Plant Height and Yield Responses of Rice to Paclobutrazol1
Authors: Street J. E. , Jordan J. H. , Ebelhar M. W. , Boykin D. L.
Published: July 2010

Lodging of rice decreases speed and efficiency of mechanical harvest of rice (Oryza salivaL. ‘Starbonnet’). A 3‐yr field study was conducted at Stoneville, MS, on a Sharkey clay soil (Vertic Haplaquept) to determine if rice height and lodging could be reduced with a growth regulator. Paclobutrazol [(2RS,3RS)‐1‐(4‐chlorophenyl)‐4,4‐dimethyI‐2‐1,2,4‐triazol‐1‐yl‐)penta‐n‐3‐ol)] was applied at 0.14 and 0.28 kg a.i./ha 2 weeks before or 2 weeks after panicle initiation, and at 0.07, 0.14, and 0.28 kg a.i./ha at panicle initiation. Application of 0.28 kg a.i./ha of paclobutrazol 2 weeks after panicle initiation reduced rice height each year and increased rough rice yield in 2 of 3 yr. Lodging, which occurred in only 1 of 3 yr, was significantly decreased with 0.28 kg a.i./ha of paclobutrazol applied either at panicle initiation or 2 weeks after panicle initiation. Increasing preflood N rates to 168 kg N/ha plus applications of paclobutrazol did not consistently increase yields
Estimation of Aerodynamic and Crop Resistances from Canopy Temperature1
Authors: O'Toole J. C. , Real J. G.
Published: July 2010

Previous reports illustrated two methods of interpreting canopy minus air temperature (Tc— Ta). The first was empirically based on linear regression of Tc— Taon air water vapor pressure deficit (VPD) and appeared to illustrate crop specific characteristics. The second approach was an energy balance equivalency for Tc— Tain which the crop parameters aerodynamic (ra) and canopy resistance (rc) were the primary crop specific components. From a crop physiology perspective, the previous reports provided an opportunity to couple crop specific physiological and micrometeorological parameters. Using data obtained from irrigated field plots in Arizona, California, and Philippines, we evaluated both approaches and tested a solution for the merger of the empirical and energy balance concepts. Briefly, the regression statistics from the regression of Tc— Taon VPD were substituted into the energy balance allowing a mean value of ra(r̄ap) and rc(r̄cp) to be estimated given conditions of potential evapotranspiration by the crop canopy. Estimation of the mean resistances are illustrated for nine crop species with r̄apanr̄cpranging from about 5 and 14 s m−1for rice (Oryza sativaL.) to 16 and 69 s m−1for fig tree (Fiscus CaricaL.). Trends in r̄apand r̄cpwere related to ecophysiological adaptation of the different species as well as phenological changes. Four growth stages of a rice crop showed increased r̄cpassociated with postanthesis senescence of panicles and leaves in the canopy. The combination of empirical regression and energy balance approaches assists in our understanding and interpretation of Tc— Ta. It also provides a means of estimating species specific values of rcand ranecessary to more fully exploit the energy balance based assessment of Tc— Ta.
Leaf Area Development in Field‐Grown Maize1
Authors: Dwyer L. M. , Stewart D. W.
Published: July 2010

Leaf area is important for crop light interception and therefore has a large influence on crop yield. In this study, a method was devised to characterize and predict the development process of maize (Zea maysL.) leaf area by separating the process into time of appearance of each mature leaf (leaf stage) and leaf area of each mature leaf (leaf expansion). Leaf area was measured for several years on each of two soil types [a sandy loam of the Uplands association (Typic Haplorthod) and a clay of the Dalhousie association (Typic Haplaquoll)] at Ottawa, Canada. Analysis of field data indicated that leaf stage was highly correlated with growing degree days (base temp of 10°C) accumulated from planting (r= 0.98). However, air temperature alone did not account for the annual variability in leaf area of mature leaves. To separate leaf expansion from leaf stage, mature area per leaf was plotted as a function of leaf number. The resultant curve had a slightly skewed bell shape whose amplitude represented the leaf area of the largest leaf. When these curves were normalized with respect to their amplitudes they varied little from year to year. The amplitudes compared well (r=0.87) to plant‐available water averaged from planting to development of the largest leaf and the sum of minimum daily temperature for the same period. Total mature plant leaf area for each year was then calculated by multiplying the integration of the normalized bell shaped curve times the amplitude calculated by the regression equation. These calculated total mature plant leaf areas were used to normalize total plant leaf areas (expanding plus mature leaf area in the absence of senescence). The normalized plant leaf areas were expressed as an S‐shaped logistic function of growing degree days and total plant leaf areas were calculated over each growing season. An additional relationship related water deficit during growth to senescence and the amount of leaf area senesced was subtracted from total plant leaf areas to obtain actual plant leaf area. Estimates of actual plant leaf area for the six growing seasons used to develop the method compared well with measured values (rbetween 0.94 and 0.99). Estimates of actual plant leaf area for two independent years at the same location were also good (r=0.91 and 0.97). This approach reduces prediction of maize leaf area to relatively simple functions of temperature and available water.
A Thermogradient Incubator for Seed Germination Studies1
Authors: Mohapatra S. C. , Johnson W. H.
Published: July 2010

Multiple temperature regimes in seed germination and seedling development studies are usually obtained with the use of several isothermal incubators. A thermogradient incubator measuring 15 by 36 by 54.5 cm and weighing less than 20 kg was built from 6.3‐mm thick aluminum sheet. It was heated electrically at the top and cooled by circulating water at the bottom. It contained 12 equidistant (2.5 cm) sample compartments separated by fixed shelves. Each shelf supported a removable tray to accommodate a row of three standard petri dishes. The mean temperature gradient along the sample compartments (but excluding the cooling and heating compartments) was linear at all temperature differentials (ΔT) tested. Settings for maximum heating at the top shelf and cooling at the bottom shelf gave approximately 54° and 0°C, respectively, thus giving a ΔT of 54°C across the 12 sample compartments. With these settings, temperature cycling with time and temperature nonuniformity within a given shelf was higher for warmer (upper) shelves but negligible for cooler (lower) shelves. However, temperature cycling in the upper shelves was minimized by selecting smaller temperature differential(s). In addition to being more portable and less expensive than other reported devices, the incubator occupies less space and permits the use of standard petri dishes or paper towels in triplicates. Construction specifications for the thermogradient incubator are provided.
Sulfur Fertilization Effects on Winter Wheat Yield and Extractable Sulfur in Semiarid Soils1
Authors: Rasmussen P. E. , Allmaras R. R.
Published: July 2010

Winter wheat (Triticum aestivumL.) yield response to sulfur (S) in semiarid climates is inconsistent on coarse‐silty, mixed mesic haploxerolls containing < 2.0 mg extractable S kg −1in the upper 0.6 m of soil. To develop more efficient S fertilization practices, we determined the initial and residual grain yield, S uptake, and extractable soil S response to 7,14,28, and 42 kg S ha −1applied as gypsum at three wheat/fallow sites and residual response to 270, 540, 810, and 1570 kg S ha 1at an annual crop site. Applied S increased grain yield at one of the three wheat/fallow sites. Maximum yield at this site was always > 3.5 Mg ha −1, whereas yield at the nonresponding sites was < 2.6 Mg ha 1. Residual S at the annual crop site increased grain yield in 10 of 16 yr, with increases occurring at yields < 2.0 Mg ha 1. Maximum yield increase was obtained with 14 S ha −1. The 14 kg S ha 1application supplied adequate S to a second, and the 28 and 42 kg ha 1applications, to a third wheat crop, even though increased extractable S from 14 kg S ha 1was not detectable in the upper 0.6 m of soil at seeding of the second crop, and residual from 28 and 42 kg S ha 1not detectable at seeding of the third crop. Periodic soil sampling at the S‐responsive site indicated progressive downward movement of S to at least 1.8 m within 4 yr. Substantial leaching of S was suggested for both annual crop and wheat/fallow systems, with partial retention in calcic horizons when present in the soil profile.
Influence of Harvest Frequency and Season on Bermudagrass Cultivar Yield and Forage Quality1
Authors: Holt E. C. , Conrad B. E.
Published: July 2010

Digestibility of bermudagrass [Cynodon dactylon(L.) Pers.] decreases with age and varies during the growing season, but cultivar responses are not well documented. Five cultivars of bermudagrass (‘Coastal’, ‘Callie’, ‘Tifton 68’, ‘S‐16’, and ‘S‐83’), representing a wide range in digestibility, were grown in replicated plots at College Station, TX on a fine, loamy, mixed, thermic Typic Udifluvent soil and harvested at 14‐, 28‐, 42‐, and 56‐day intervals for 2 yr to determine responses to harvest frequency and seasonal trends in digestibility. Forage was separated into leaf and stem tissue to determine leafiness the first year and also analyzed for dry matter digestibility both years using the in vitro fermentation technique (IVDDM). Coastal produced significantly more forage than the other cultivars, but was the lowest in IVDDM. Total annual forage yield increased 0.15 Mg ha 1for each day of advancing age at harvest > 14 days of age, total yields being 58% higher when harvested every 56 days than when harvested every 14 days. Both IVDDM and leafiness declined with advancing age, 56‐day‐old forage having 89 g kg 1less digestibility and 180 g kg−1less leaf content than 14‐day‐old forage. Leafiness closely correlated to age of forage at harvest but not to IVDDM within specified ages. One cultivar (S‐83) tended to increase in yield more rapidly and to decrease in IVDDM less rapidly with advancing age than the other cultivars. The rate of decline (average of all cultivars) in forage IVDDM was 2 g kg 1of dry matter for each day of advancing age between 14 and 56 days. Forage IVDDM declined from spring to early summer, independent of age at harvest and somewhat independent of leafiness. Young forage increased in IVDDM after midsummer. Results of this study suggest that cultivars of bermudagrass can be selected for higher forage digestibilities. However, cultivars with higher digestibility tend to follow the same pattern as Coastal, which is a decline in digestibility with increasing age and advancing season.
Yield and Grain Quality Responses of Soft Red Winter Wheat Exposed to Ozone During Anthesis1
Authors: Mulchi C. L. , Sammons D. J. , Baenziger P. S.
Published: July 2010

Six soft red winter wheat (Triticum aestivum L.) cultivars were exposed to a simulated air pollution episode during anthesis in field studies conducted during 1979 and 1980. The air pollution treatments equaled 23 ± nL L−1, 47 ± 10 nL L−1 (ambient) and 123 ± 4 nL L−1 ozone for 4 h day−1 for 5 days in May. The primary objectives were to examine the effects of air pollution episodes along the mid‐Atlantic states during wheat pollination in May on yields and grain quality characteristics. Plant characteristics examined included total plant dry weights, grain weights, harvest index, seed set, seed weight, grain protein contents, particle size index, and alkaline water retention capacity. Environmental conditions in 1979 favored greater plant productivity than in 1980 and significant (P≤0.05) year effects were observed for four of eight characteristics examined. Also, ozone treatment responses were greater in 1979 than in 1980. Significant (P≤0.05) ozone treatment effects were observed for seven of eight characteristics and significant year ✕ treatment interactions were found for all eight variables. Although significant cultivar differences were noted for all eight variables, the only significant treatment ✕ cultivar interactions found were for grain weights, harvest index, and seed weights. The results further suggest that multiple environments should be considered and grain quality characteristics should be examined in addition to yields and yield components when evaluating responses among wheat cultivars to ozone stress.
Climatic Change, Weather Variability, and Corn Production1
Authors: Thompson Louis M.
Published: July 2010

A crop/weather model was used to determine the impact of changes in climate and weather variability on corn (Zea mays L.) production from 1891 to 1983. Five Corn Belt states, Illinois, Indiana, Iowa, Missouri, and Ohio, were included in the study. These states produce over 50% of the U.S. corn crop. A cooling trend from 1930 to 1972 was accompanied by increasing rainfall in July and August, and by decreasing weather variability. These three factors were favorable for corn yield increase. Simulated corn yields, calculated from weather data, increased 970 kg ha−1 from 1930 to 1972 because of improved weather for corn. After 1972 there was greater weather variability and higher intensity rainfall events. Fertilizer use on corn increased substantially in the 1960s and increased at slower rate after 1972. The annual increase in corn yield with normal weather after 1972 was less than half as much as it was from 1960 to 1972. Highest yields of corn have been associated with normal preseason precipitation, normal June temperature, below normal temperature in July and August, and above normal rainfall in July and August. The period after 1970 was expected to warm but weather variability has masked the identification of a trend.
Response of Spring Wheat, Barley, and Oats to Chloride in Potassium Chloride Fertilizers1
Authors: Fixen P. E. , Gelderman R. H. , Gerwing J. , Cholick F. A.
Published: July 2010

Cereal grain yield response to KCI fertilization has been reported on high K‐testing soils in the Northern Plains. Other field studies have demonstrated that wheat (Triticum aestivum L.) yield increases to CI fertilization occurred where disease incidence was high. Therefore, field experiments on high K‐testing soils were conducted over a 3‐yr period to determine the responsiveness of spring wheat, barley (Hordeum vulgare L.), and oats (Avena sativa L.) to KCI fertilization and to determine whether responses were due to K or to Cl. Experiments were conducted on soils representing Typic Argiustolls, Pachic Udic and Udic Haploborolls, and Pachic and Udic Haplustolls in eastern South Dakota. Spring wheat, barley, and oats showed grain yield increases (0.10 probability level) at four out of six, three out of six, and zero out of five sites, respectively, on soils that tested very high in ammonium acetate‐extractable K. Wheat grain yield increases varied form 0.2 to 0.5 Mg ha−1. Comparison of KCI, KNO3, and CaC12 treatments, soil analysis, and plant analysis all indicated that the yield increases on very high K‐testing soils were due to the CI in the KCI and not due to the K. Six additional wheat experiments were conducted to determine the influence of starter K and CI (applied with seed) on grain yield; however, no yield increases to CI were detected in these studies. Both KCI and KNO3 at a 20 kg K ha−1 rate significantly decreased yield at one of six sites. Other experiments showed that if sufficient CI was present in the soil or broadcast applied, no additional benefit to seed placed CI occurred. Generally, broadcast and seed placed KCI appeared equally effective. However, rates required for maximum yield at several sites were too high to be placed in direct seed contact with drill application due to potentially adverse salt effects. Grain yield increases were large enough to make KCI fertilization of these soils very economical, provided responsive sites could be predicted.
Dryland Grain Sorghum Water Use, Light Interception, and Growth Responses to Planting Geometry1
Authors: Steiner J. L.
Published: July 2010

Crop yields are primarily water‐limited under dryland production systems in semiarid regions. This study was conducted to determine whether the growing season water balance could be manipulated through planting geometry. The effects of row spacing, row direction, and plant population on the water use, light interception, and growth of grain sorghum [Sorghum bicolor (L.) Moench] were investigated at Bushland, TX, on a Pullman clay loam (fine, mixed, tbermic Torrertic Paleustoll). In 1983, which had a dry growing season, narrow row spacing and higher population increased seasonal evapotranspiration(ET) by 7 and 9%, respectively, and shifted the partitioning of ET to the vegetative period. Medium population crops yielded 6.2 and 2.3 Mg/ha of dry matter and grain, respectively. High population resulted in high dry matter (6.1 Mg/ha) and low grain yield (1.6 Mg/ha), whereas low population resulted in low dry matter (5.4 Mg/ha) and high grain yield (2.3 Mg/ha). Row direction did not affect water use or yield. In 1984, dry matter production for a given amount of ET and light interception was higher in the narrow‐row crops. Evapotranspiration was less for a given amount of light interception in the narrow‐row crops and in the north‐south row crops. Narrow‐row planting geometry appears to increase the partitioning of ET to the transpiration component and may improve the efficiency of dryland cropping systems.
Nitrogen Fertilizer Source, and Method and Time of Application Effects on No‐till Corn Yields and Nitrogen Uptakes1
Authors: Fox R. H. , Kern J. M. , Piekielek W. P.
Published: July 2010

The increasing use of both no‐tillage corn (Zea mays L.) production and urea‐containing fertilizers makes it imperative that we develop management strategies that maximize economic return from applications of these fertilizers to no‐till corn. A 3‐yr experiment was conducted on a Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludult) to determine the relative efficiencies (yield and N uptake per unit of N applied) of three common N sources [NH4NO3 (AN), urea, and urea‐ammonium nitrate solution (UAN)] used on no‐till corn. They were applied either as a surface band or as an injected band at or near the time of planting, or as a sidedress 26 to 31 days after plant emergence. Surface‐banded AN, injected AN, and injected urea all produced similar no‐till corn yields and N uptakes. The apparent NH3 volatilization loss from surface‐banded urea was strongly influenced by the number of days after application until a total of 10 mm of rain fell. Apparent losses ranged from less than 50 g kg−1 of applied N with 10 mm of rainfall within 2 to 3 days after application, to over 300 g kg−1 with 5 to 7 days of dry weather after application. Both surface‐banded and injected UAN were less efficient than AN or injected urea. Sidedress applications of N resulted in more efficient N fertilizer utilization with all sources, but particularly with urea‐containing sources. Shorter rain‐free periods after sidedress applications may have contributed to this effect. Surface applications of an experimental fertilizer, 3:1 urea/urea phosphate, produced greater ear‐leaf at silking N concentrations than did surface‐banded urea. Amending urea with KCI, or UAN with ammonium thiosulfate, did not result in yields, ear‐leaf N concentrations, or N uptakes significantly different from those obtained with their unamended surface‐applied counterparts in the one year that each was tested.
Environment and Cultivar Effects on Winter Wheat Response to Ethephon Plant Growth Regulator1
Authors: Wiersma D. W. , Oplinger E. S. , Guy S. O.
Published: July 2010

Recent introductions of new disease resistant, higher yielding winter wheat (Triticum aestivum L.) cultivars and plant growth regulators (PGRs) to reduce lodging, coupled with a growing awareness of high wheat yields in Europe, has resulted in an increased interest in and the development of Intensive Cereal Management (ICM) systems in the USA. Increases in fertility levels and seeding rates, practices used in ICM systems, may significantly increase lodging in winter wheat. The objective of this study was to evaluate the effects of the PGR ethephon [(2‐chloroethyl) phosphonic acid] on grain yield, lodging, plant height, test weight, and moisture percentage of seven winter wheat cultivars grown in various environments. Averaged across environments and cultivars, ethephon reduced lodging and plant height, and increased grain yield an average of 0.28 Mg ha−1, of 6.4%. Average environment × PGR and cultivar × PGR interactions were nonsignificant for grain yield, plant height, lodging, and test weight, but orthogonal contrasts showed variable responses to ethephon between environments and cultivars. Lodging and grain yield were negatively correlated, while lodging and plant height were positively correlated. With the exception of the cultivar Caldwell, grain yields were not increased by PGR applications when there was no lodging.
Tillage System and Date of Planting Effects on Yield of Corn on Soils with Restricted Drainage1
Authors: Herbek J. H. , Murdock L. W. , Blevins R. L.
Published: July 2010

It has been reported that no‐tillage corn (Zea mays L.) production on poorly‐drained soils results in more uneven stands and slower early growth as compared to conventional tillage methods. A field study was established in 1979 at Princeton, KY, on a Johnsburg silt loam (Aquic Fragiudults) intergrading to a Tilsit silt loam (Typic Fragiudults), to compare corn planting dates under no‐tillage (NT) and conventional tillage (CT) systems. For the NT system, a yield increase trend was observed as planting date progressed from the first planting date (late April) to the second (mid‐May). Grain yields from conventionally tilled treatments decreased with delayed planting dates. No‐tillage corn performed better than CT corn during drier growing seasons, and conventionally tilled corn produced yields equal to or slightly higher (no significant differences) for early planting dates, during years in which wet and cool climatic conditions existed during the early part of the growing season. There appears to be a greater risk associated with early planting dates for NT corn on these soils. From a management viewpoint, corn planting on these cooler soils with slow internal drainage can be delayed due to excessive wetness without substantial yield losses if NT management is used.
Developmental Morphology of Dent Corn and Popcorn with Respect to Growth Staging and Crop Growth Models1
Authors: Stevens E. J. , Stevens S. J. , Flowerday A. D. , Gardner C. O. , Eskridge K. M.
Published: July 2010

Crop growth staging and developmental modeling (using regression analysis) requires a series of easily understood and documented field descriptives plus a continuous numerical analogue capable of generating data which conform with the underlying assumptions of regression analysis. One numeric phenological key and two mixed phenological keys combining alphabetic and numeric codes are presently used within the U.S. Corn Belt to describe and model the growth and development of dent corn and sweet corn (Zea mays L.). With respect to developing crop growth regression models, the phenology of popcorn has neither been adequately described nor compared with its assumed analogue, dent corn. The purpose of this research was to (i) document the phenology of popcorn, (ii) evaluate the suitability for popcorn of three commonly used phenological keys developed for dent corn, and (iii) if necessary, develop a universal set of phenological field descriptives and a continuous numeric analogue appropriate to developing corn regression growth models. One locally adapted dent corn cultivar (B73 × Mo17) and three differently maturing popcorn cultivars (P410, P609, and Iopop 12) were evaluated for three seasons (1982–1984) across three planting dates at one location in eastern Nebraska at the University of Nebraska Field Laboratory near Mead in Saunders County. None of the phenological keys tested were completely suitable for describing or modeling (using regression analysis), or both, the phenologies of dent corn and popcorn materials, which displayed contrasting morphological characteristics associated with leaf development, leaf number, grain type, and grain development. The universal phenological key and numeric analogue described in this article was therefore developed for modeling the phenology of genetically diverse cultivars grown across a range of environments.
Effects of Various Fungicides and Insecticides on Emergence of Three Wheat Cultivars1
Authors: Khaleeq B. , Klatt A.
Published: July 2010

Treatment of seeds with fungicides, insecticides, or a combination of both has been practiced by seedsmen, scientists, and farmers in order to protect seeds and seedlings from different pests. Treating seeds with recommended rates of application is usually safe, but workmen sometimes add more than the recommended rate. Treated seeds are also kept in storage for some time before planting. The purpose of the study was to find out the effects of those chemicals and to determine whether the treated seeds could be stored without loss of viability. Seeds of three wheat (Triticum aestivum L.) cultivars, Bolal, Bezostaya, and Köse 220/39, were treated with the fungicides carboxin [5,6‐dihydro‐2‐methyl‐1,4‐oxathiin‐3‐carboxanilide] and benlate [methyl 1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] and the insecticides aldrin [1,2,3,4,10,10‐hexachloro‐1,4,4a,5,8,8a‐hexahydro‐exo‐1,4 endo‐5,8‐dimethanonaphthalene], heptachlor [ 1,4,5,6,7,8‐heptachloro‐3 a.4.7.7a‐tetrahydro‐4,7‐methanoindene), and carbofuran [2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate] to determine the effects of these chemicals, alone and in combination, on germination and emergence. All seed lots were treated at the same time and were planted 10,30, and 50 days after treatment at 30‐mm depths in soil (a silty clay loam, typical of Turkey's Anatolian Plateau) at a greenhouse in Ankara, Turkey. After the first day of emergence, seedlings were counted daily for 7 days. Aldrin, heptachlor, and carboxin did not reduce seedling emergence. Benlate reduced emergence 17, 18, and 23% in Bezostaya, Bolal, and Köse 220/39, respectively, when seeds were stored for 50 days and seedlings counted 11 days after planting. Carbofuran decreased emergence as the storage period increased, especially in Köse 220/39. Carbofuran was the only pesticide that was consistently more phytotoxic when rates were doubled or tripled. Combinations of carboxin with either aldrin or heptachlor did not generally reduce emergence. However, all combinations involving carbofuran reduced emergence more than carbofuran alone. Cultivars varied in susceptibility to fungicides and insecticides. Bolal, a hard red winter wheat from Nebraska, showed the most tolerance. Seedling emergence of Köse 220/39, a Turkish variety, was reduced 13 to 19% more than was Bolal at the 11‐day seedling count in all seed treatment storage periods. Seedling emergence of Bezostaya, a Russian variety, was intermediate between Bolal and Köse 220/39. Adverse effects of pesticides that reduced emergence were more evident as storage time increased. Results indicated that benlate and carbofuran, used alone or in combination, reduced seedling emergence. Less phytotoxicity resulted if seeds were planted as soon as possible after treatment.