bluuebunny/crossref_metadata_2025 huggingface dataset:
Wheat Seedling Growth and Developmental Response to Incident Photosynthetically Active Radiation1
Authors: Rickman R. W. , Klepper Betty , Peterson Curt M.
Published: July 2010

Shade from residues of previous crops in high residue seedbeds may limit development of winter cereal seedlings. A growth chamber experiment with photosynthetic photon flux densities of 140, 275, or 500 µmol−2s−1 for 12 h each day was designed to reveal the growth and development patterns of winter wheat (Triticum aestivum L. em Thell.) under light limiting conditions. Daily totals of light received during winter months at 46°N Lat are within this range. Leaf and tiller growth and development were observed daily on 6 to 12 separately potted plants in each of seven treatments for 1 month after emergence. At 140 µmol m−2s−1, a higher fraction of specific tiller buds failed to elongate than at either higher irradiance. Failure to elongate one tiller bud did not influence the point of development of subsequent tillers. Plants developed at 0.0097,0.0117, and 0.0138 leaves per degree day (0°C base) under 140, 275, and 500 µmol m−2s−1 treatments, respectively. An average of only four tillers per plant were present after 27 days under 140 µmol m−2s−1 while 12 tillers per plant were produced under 500 µmol m−2s−1. The basic relationship between main stem leaf and individual tiller development was not changed by different amounts of light. Specific tillers appeared at essentially the same point in plant development regardless of irradiance. At 140 µmol m−2s−1, the slower leaf development and reduced tillering both contributed to reduce plant weights to only one‐fifth those from the 500 µmol m−2s−1 treatment. The irradiance required for maximum development rate of winter wheat seedlings exceeds that expected in shaded areas of a seedbed from November through February at 46° N Lat. Based on this experiment, irradiance will not change the point of development of specific tillers relative to main stem leaf development. Irradiance will influence the fraction of plants with specific tillers and the rate (leaves per degree day) of leaf appearance. Leaf development rate (leaves per degree day) appears to be buffered by short term (a few days) energy reserves. Winter wheat seedlings that are shaded over winter will skip a higher fraction of the early tillers (T0, T1) than unshaded seedlings, reducing the population of potentially large heads.
Corn Irrigation Scheduling in Humid Regions on Sandy Soils with Tillage Pans1
Authors: Cassel D. K. , Martin C. K. , Lambert J. R.
Published: July 2010

Several droughts during the past decade in humid regions of the USA, especially the Southeast, have intensified the interest in supplemental irrigation. One objective of this study was to evaluate the effect of supplemental irrigation in a humid environment on corn (Zea maysL.) production on an Atlantic Coastal Plain soil having a tillage pan. A second objective was to evaluate two alternative techniques for scheduling supplemental irrigation in humid regions. The study, conducted on a Wagram soil (Arenic Paleudults)‐Norfolk soil (Typic Paleudults) from 1979 to 1981, employed a split plot design with water level (irrigation scheduling) as the main block. Water levels were control or dryland (W1), scheduled irrigation water applications based on a computerized water balance model (W2), and scheduled water applications based on tensiometer measurements (W3). Subplot treatments were time of N application in 1979 and 1980 and cultivation intensity in 1981. Compared with a normal rainfall of 447 mm during the growing season, 464, 262, and 220 mm fell during 1979, 1980, and 1981, respectively. The average amount of irrigation water applied over the 3‐yr period based on the water balance model was 40 mm greater than the 3‐yr average of 179 mm applied based on the tensiometers. Grain yield as affected by subplot treatment was not significantly different for any year. Mean grain yields for the 3‐yr period were 2.58, 7.73, and 8.14 Mg ha−1, for treatments W1, W2, and W3, respectively. Either irrigation scheduling method offers large yield improvements in drier years, but no significant yield difference occurred for the two scheduling techniques. In the wetter year 1979, irrigation increased yield by 2.45 Mg ha−1, whereas in the dryer years of 1980 and 1981 the increases were 6.53 and 7.06 Mg ha‐1, respectively.
Molybdenum Limitations to Alfalfa Growth and Nitrogen Content on a Moderately Acid, High‐Phosphorus Soil1
Authors: Doerge T. A. , Bottomley P. J. , Gardner E. H.
Published: July 2010

Alfalfa (Medicago sativaL.) grown in an Aquultic Argixeroll at pH 5.5 had a low N content and produced very low yields even though soil and/or plant tissue analysis for Al, Mn, Ca, P, Mo, and Mg did not indicate deficiency or toxicity conditions. Field and greenhouse experiments with pH, Ca, N, and Mo variables were undertaken to characterize the factor(s) limiting production of alfalfa on this soil. Plants at all pH levels (5.5 to 6.4 in the field and 5.3 to 6.5 in the greenhouse) were well nodulated. Under greenhouse conditions the application of 1 mg Mo kg−1soil resulted in a total dry matter yield, total N uptake, and shoot N concentration of 9.87 g pot−1, 0.216 g pot−1, and 26.5 g kg−1, respectively, compared with corresponding values of 2.96, 0.040, and 20.6 for plants grown without Mo. The application of 714 mg N kg−1(greenhouse) and 672 kg N ha−1(field) as NH4NO3to alfalfa grown in unamended soil increased shoot dry matter production from 1.46 to 7.01 g pot−1in the greenhouse and 3.7 to 12.0 Mg ha−1under field conditions. No response in yield or nodulation to the application of CaSO4was measured. Responses to N and Mo, especially at the lower pH levels, suggested that the growth response to lime is due primarily to increased nodule efficiency, resulting from greater Mo availability as soil pH is raised. On moderately acidic fertile soils, the application of Mo to well‐nodulated but N‐deficient alfalfa may provide an economical, effective means for increasing production where low Mo availability is the major growth‐limiting factor.
Variability Among Plants in Dinitrogen Fixation (Acetylene Reduction) Rates by Field‐Grown Soybean1
Authors: Denison R. F. , Weisz P. R. , Sinclair T. R.
Published: July 2010

High variability in acetylene reduction rates within cultivars and treatments has been a problem in evaluating treatment and cultivar effects. This study examined the sources of such variability, using field‐grown soybean [Glycinee max(L.) Merr.] plants. Acetylene reduction rate per plant was measured in situ for thinned and unthinned ‘Chippewa 64’ soybean near Ithaca, NY for well‐watered and drought‐stressed ‘Biloxi’ soybean in Gainesville, FL and for ‘Guelph’ soybean subject to extended photoperiods in Gainesville, FL. A number of morphological traits, including leaf weight per plant and nodule weight per plant, were measured for each plant assayed. In addition, the nodule gas conductance (permeability ✕ surface area) was computed for each plant. Correlations between these characteristics and acetylene reduction rate per plant were used to assess their relative importance. Acetylene reduction rate was consistently more closely correlated with nodule weight than with shoot characteristics. The highest correlation with acetylene reduction rate was, however, with nodule gas conductance. This correlation was highly significant across all treatments, cultivars, and maturity stage. Nodule gas conductance was concluded to play an important role in determining acetylene reduction rates in field‐grown plants.
Influence of Surface Liming on the Yield and Nutrient Concentration of Alfalfa Established Using No‐Tillage Techniques1
Authors: Rechcigl J. E. , Wolf D. D. , Reneau R. B. , Kroontje W.
Published: July 2010

Soil acidity is believed to be an important cause of limited root penetration and low herbage yields of alfalfa (Medicago sativaL.). Alfalfa was seeded into an orchardgrass (Dactylis glomerataL.) sod to evaluate the influence of surface‐applied limestone on alfalfa growth under acidic soil conditions. Alfalfa was planted without tillage in April of 1981 and 1982 on an Ernest silt loam soil (fine‐loamy, mixed, mesic Aquic Fragiudult). Dolomitic agricultural limestone was surface applied at 0 or 6.7 kg ha−1either 8 or 20 months before or at planting. Yield (from 1982 through 1984) increases, greater than two‐fold, resulted from surface application of limestone. Time of lime application had no influence on yields. Roots were more prevalent at the 1.0‐ and 1.5‐m depths due to surface limestone application. Soil pH (0‐ to 10‐cm depth) ranged from 6.4 to 6.9 in the surface limed plots as compared to 5.3 to 5.9 in the unlimed plots. The pH averaged 5.1 at and below the 45‐cm depth irrespective of limestone application. Exchangeable Al ranged from 22 mg kg−1at the 0‐ to 5‐cm depth to 186 mg kg−1at the 145‐ to 150‐cm depth on unlimed plots. Lime application reduced Al 2‐ to 20‐fold in the upper 15 cm, but had no influence on Al concentrations at depths of 95 cm and greater.
Economic Comparisons of Crop Rotations Including Alfalfa, Soybean, and Corn1
Authors: Hesterman O. B. , Sheaffer C. C. , Fuller E. I.
Published: July 2010

The increasing cost of N fertilizer and development of new alfalfa (Medicago sativaL.) germplasm with increased storage of reduced N in roots and crowns have accentuated the importance of determining the economic value of 2‐yr alfalfa‐corn (Zea maysL.) rotations. Our objectives were to (i) determine the economically optimum rotation/N‐fertilization combination of corn following alfalfa at four Minnesota locations and (ii) compare the profitability of alfalfa‐corn rotations with that of continuous corn and soybean [Glycine max(L.) Merr.]–corn systems. Field studies were conducted in 1982 and 1983 at four Minnesota locations (soils were Udorthentic Haploborolls, Typic Haplaquolls, Aquic Haplustolls, and Typic Haplaquolls). First‐year rotation components included alfalfa, corn, and soybean, and the 2nd‐yr component was Corn. Alfalfas were subjected to two harvest systems. Four or five rates of N fertilizer were applied to corn. A linear programming model selected the optimum 2‐yr rotation/N‐fertilization combination at each location. A parametric procedure was used to determine changes in the optimum rotations as N costs varied ($.26 to $2.25 kg−1).

An alfalfa‐corn sequence with alfalfa subjected to a three‐cut system was the economically optimum rotation. Continuous corn and soybean‐corn systems resulted in at least a $39 and $200 ha−1decrease, respectively, in 2‐yr gross margin. At three of four locations, ‘Saranac AR’ provided greater gross margins than ‘MN ROOT N’, an experimental alfalfa.

Optimum rotations were determined more by the quantity and quality of alfalfa forage produced than by differences in second‐phase corn grain yield. Our results suggest that management of alfalfa to increase production of high‐quality forage will contribute to the economic viability of 2‐yr alfalfa‐corn rotations.
Response of No‐Tillage Corn Grown in Corn and Soybean Residues to Several Nitrogen Fertilizer Sources1
Authors: Eckert D. J. , Dick W. A. , Johnson J. W.
Published: July 2010

Proper management of different N fertilizer sources to reduce effects of ammonia volatilization, denitrification and N immobilization potentials is necessary for successful no‐tillage corn (Zea maysL.) production. A 2‐yr study was conducted on a Canfield silt loam (fine‐loamy, mixed, mesic Aquic Fragiudalf) to evaluate corn response to several N sources‐anhydrous ammonia, broadcast urea, and broadcast urea‐ammonium nitrate solution, when the crop was grown in two crop residues (corn or soybean [Glycine maxL. (Merr.)]. Nitrogen was applied at 112 and 168 kg N ha−1at planting. In both years, urea produced lower yields than ammonia in corn residue but yields equivalent to ammonia in soybean residue. Urea‐ammonium nitrate solution produced (i) lower yields than ammonia in both years in corn residue; (ii) equal yields to ammonia in soybean residue in 1982, but (iii) lower yields than ammonia at the low N rate in soybean residue in 1983. It appears that N source selection for no‐tillage corn can be affected by residue conditions, with less potential for decreased yields when urea‐based N materials are used in soybean residue conditions.
Production of Alfalfa in Pennsylvania Soils of Differing Wetness1
Authors: Alva A. K. , Lanyon L. E. , Leath K. T.
Published: July 2010

Plant nutrient applications and plant disease resistance are management factors that may contribute to successful alfalfa (Medicago sativaL.) production on soils that are not inherently well suited to growing alfalfa. Applications of K and P, and cultivar resistance to Phytophthora root rot (Phytophtora megaspermaf. sp. medicaginis; PRR) were evaluated on six well to poorly drained field soils to determine the contributions of these factors to alfalfa production under less than ideal conditions. The six soils were representative of two extensive soil associations in northwestern Pennsylvania. Factorial combinations of 0,175,350, and 525 kg ha−1yr−1K, and 45 and 90 kg ha−1yr−1P were applied annually for 3 yr. Significant yield response to only applied K was measured on two of the three soils of each association. Economic optimum rates for the 3 yr ranged from 137 to 263 kg ha−1yr−1K. Herbage K concentrations of 16.0 to 19.5 g kg−1and exchangeable soil K of 275 kg ha−1K were the minimum levels necessary to produce 90% of the maximum yield for the first harvest year. When the soil water table was within 50 or 25 cm of the soil surface at some time during the growing season, total yields for the 3‐yr period were reduced by 20 to 25% or 80 to 85%, respectively. Due to the lack of PRR development, cultivar resistance to PRR did not influence the total alfalfa yields. Neither management factor of nutrient application nor cultivar resistance to PRR could compensate for the adverse effects of excess soil wetness on alfalfa. The extent of the area in each association in which excess soil water would adversely alfalfa production ranges from 10 to 75%
Response to Vertical Mowing and Ethofumesate Treatments for Annual Bluegrass Control in Bermudagrass Turf1
Authors: Johnson B. J.
Published: July 2010

Annual bluegrass (Poa annua L.) is a major weed in bermudagrass (Cynodon spp.) golf greens overseeded with cool‐season grasses. Herbicides are often ineffective or may injure the overseeded grass. This study was initiated to determine the effects of sequential vertical mowing and ethofumesate [( ± )‐2‐ethoxy‐2,3‐dihydro‐3,3‐dimethyl‐ 5‐benzofuranyl methanesulfonate)] treatments on a bermudagrass green. Treatments were arranged as a split plot design with whole plots as vertical mowed treatments in a randomized complete block and subplots as ethofumesate treatments stripped across all whole plots with four replications. One‐half of each whole plot was overseeded with perennial ryegrass (Lolium perenne L.) in each of 2 yr. The bermudagrass was an established 'Tifway' Cynodon transvaalensisBurtt‐Davies ✕ C. dactylon (L.) Pers.] growing on a sandy loam (clayey, kaolinitic thermic Typic Hapludult). Vertical mowed treatments included: none, low (25% leaf removal), and high (60% leaf removal) intensity prior to overseeding and applying ethofumesate. Ethofumesate treatments were made at time of overseeding in October or delayed until bermudagrass was dormant in November. Herbicide treatments were also applied at the same time to nonoverseeded common bermudagrass [Cynodon dactylon (L.) Pers.] infested with annual bluegrass. October vertical mowing reduced bermudagrass quality the following spring. Quality was reduced with increased intensity. Vertical mowing and ethofumesate applied in October reduced quality in April and May more than either treatment alone. Transition from cool‐season to bermudagrass was generally slowest in the high‐intensity vertical mowed turf.
Selected Chemical and Physical Properties of Soils Manifesting Cotton Root Rot1
Authors: Smith R. B. , Hallmark C. T.
Published: July 2010

Some soils that produce cotton (Gossypium spp.) that is free of Phymatotrichum omnivorum are physically adjacent to similar soils on which cotton annually succumbs to the fungus. This study evaluated relationships of soil properties to incidence of cotton root rot (CRR) at 26 sites. Complete pedon descriptions were made, and horizons were sampled and analyzed to determine selected physical and chemical soil properties. Means of soil analyses for non‐root rot (NRR) and root rot (RR) soil groups were compared by t‐test using the weighted averages for the surface horizons, upper 0.50‐m and 1.0‐m sections. Physical properties were not suitable indicators of disease incidence; however, extractable Mg2+ within land resource areas was found to be significantly greater in NRR‐affected rather than RR‐affected soils. Furthermore, the ratio of extractable Ca2+ to Mg2+ was found to be greater in RR soils than NRR soils. X‐ray analysis of the soil carbonates did not indicate that the differences were the result of differential Mg contents of the soil carbonates. In addition to Mg2+, mean extractable Fe2+, Zn2+, and Cu2+ were found to be greater in NRR soils in some cases. The soluble bicarbonate ion content of surface horizons was also found to be higher in RR soils than NRR soils. Results suggest that cotton grown in RR soil is more stressed than that grown in adjacent NRR soil.
Maize‐Cowpea Intercropping as Affected by Nitrogen Fertilization1
Authors: Ezumah H. C. , Nam Nguyen Ky , Walker P.
Published: July 2010

Plant architecture and N fertilizer may limit the performance of intercropped maize (Zea mays L.) and cowpea [Vigna unguiculata (L.) Walpers] cultivars. This paper describes an experiment in which cultivars of maize and cowpea were intercropped and fertilized with varying rates of N. The cowpea cultivars tested included a semi‐erect and photoperiod‐insensitive cultivar, TV × 3236, and a photoperiod‐sensitive cultivar, Vita 5. Both were intercropped in factorial combinations with three maize cultivars: a short, early maturing cultivar, Population 49, the tall, highly vegetative cultivars, TZSRW and TZPB. All cultivars were grown in an Alfisol soil (Oxic Paleustalf, Egbeda series) with rates of 0, 40, 80, and 120 kg N/ha applied. Maize responded positively to N fertilization. Grain yields of maize increased 62% with N rates from 0 to 120 kg/ha, while average cowpea yield decreased 27%. The magnitude of these changes varied with maize and cowpea architecture and growth habits. There are available cultivars of maize and cowpea that are compatible for mixed cropping, especially at high rates of N application. The sensitivity of the various treatments used was improved by use of bivariate analysis.
Lime and Gypsum Effects on Pea‐Root‐Pathogen Inoculum and Related Factors in a Wheat‐Peas Rotation1
Authors: Allmaras R. R. , Kraft J. M. , Pikul J. L.
Published: July 2010

Root‐disease responses to manageable soil chemical factors, such as pH or Ca saturation, can be an effective biological control strategy. In a wheat‐peas rotation, single applications of lime, to adjust pH of a Walla Walla silt loam (coarse silty, mixed, mesic Typic Haploxeroll) from 5.5 to 6.2, produced less growth in peas (Pisum sativum, L.) than in wheat (Triticum aestivum L.)—a response inconsistent with greater legume responses to liming. Gypsum applied at 1 Mg/ha did not change soil pH, but was adverse for late‐season pea growth while the sulfate ion remained in the upper 0.30 m of soil. Wheat responded to the added S. Propagule density of Pythium ultimum was high enough to damage pea roots, but showed no differential response to the single lime or gypsum application during the 4‐yr period. Propagule density of Fusarium solani f. sp. pisi in the 0‐ to 0.15‐m soil layer of the lime treatment decreased 37% over a 3‐yr period. Gypsum reduced propagule density 22%. Increased exchangeable Ca in response to the lime and gypsum was the only soil factor that explained this reduced propagule density. Calcium may have improved the resistance of pea‐root membranes to pathogen attack, impaired saprophytic growth and survival of the pathogen, or favored microbial antagonism of the pathogen. No measurements were made to determine the mechanism for the Ca effect. Reduced propagule numbers in the top 0.15 m of soil may not have reduced root disease because propagules of F. solani f. sp.pisi were abundant in the 0.15‐ to 0.45‐m layer, which had a pH of 5.7 and showed only a negligible increase of Ca saturation.
Time of Flower Opening and Seed Mass in Soybean1
Authors: Egli D. B. , Wiralaga R. A. , Bustamam T. , Zhen‐Wen Yu , TeKrony D. M.
Published: July 2010

Seeds from an individual soybean [Glycine max (L.) Merrill] plant exhibit a range in seed mass, the cause of which is not well understood. This research was conducted to investigate the relationship between the time of flower opening and seed mass. Five soybean cultivars (Cumberland, Harper, DeSoto, Douglas, and Essex) were grown in the field using conventional cultural practices in 1984 and 1985. Fully open flowers were marked with acrylic paint at growth stages R1 to R4.5. Fruits from marked flowers were harvested at maturity and seed dry mass determined. The range in seed mass was estimated using round‐hole screens. The rate of seed development was monitored by determining when seeds reached 3 mm in length and when the pod turned yellow. Mean mass of seeds from flowers opening at R4 or R4.5 was less than mass of seeds from earlier flowers, and this was associated with a shorter seed filling period. Seed mass was not consistently related to time of flowering for flowers opening at R1 to R3. There was a range in seed mass within a time of flower opening, and most of this variation was associated with variation in seed growth rate. Applying fruit removal treatments when pods from the marked flowers reached maximum size indicated that the maximum potential mass of seeds from late flowers was much larger than the normal mass. The data indicate that the time of flowering accounts for only a portion of the variation in seed mass of a soybean plant.
Selective Control of Annual Bluegrass in Cool‐Season Turfs with Fenarimol and Chlorsulfuron
Authors: Gaul M. C. , Christians N. E.
Published: July 2010

Annual bluegrass (Poa annua L.) is a weed that presents turfgrass managers with serious problems upon infestation into desired turfgrass stands. This species can be managed as a turfgrass, but selective herbicides for its removal would be very useful in intensely managed turfs. In this study, fenarimol [3‐(2‐chlorophenyl)‐3‐(4‐chlorophenyl)‐5‐ pyrimidinemethanol] and Chlorsulfuron {2‐chloro‐N[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐y1)‐aminocarbonyl]‐benzenesulfonamide} were tested in field and greenhouse trials over a 2‐yr period to determine their effectiveness as annual bluegrass (Poa annua L.) controls in both Kentucky bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds.) turfs. Fenarimol treatments in the field included rates of 0, 155, 306, 459, 612, and 765 g ha−1 applied eight times in 1984 until cumulative amounts of 1.2, 2.4, 3.7, 4.9, and 6.1 kg ha−1 were reached, and seven times in 1985 until cumulative amounts of 1.1,2.1,3.2,4.3, and 5.4 kg ha−1 were reached. In the greenhouse, fenarimol was applied at single application rates of 1.5, 3.0, 4.6, and 6.1 kg ha−1. Chlorsulfuron was applied in the field at single application rates of 18, 35, 70, 140, and 280 g ha−1 and in the greenhouse at single application rates of 70, 140, 210, and 280 g ha−1. Fenarimol was not effective in controlling annual bluegrass in the field or greenhouse and caused discoloration to the creeping bentgrass in the field at rates above 4.9 kg ha−1. Chlorsulfuron was effective in controlling all three annual bluegrass biotypes in the greenhouse and had no detrimental effects on creeping bentgrass or Kentucky bluegrass. In the field, Chlorsulfuron was effective in controlling annual bluegrass at one of the two testing sites.
Effect of Temperature, Daylength, and Solar Radiation on Production of Coastal Bermudagrass
Authors: Burton G. W. , Hook J. E. , Butler J. L. , Hellwig R. E.
Published: July 2010

Forage yields of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] drop sharply in late summer and fall, even though warm temperatures continue. The objective of this study was to examine relationships among meteorological parameters and forage yield of irrigated and rain‐fed Coastal bermudagrass fertilized annually with 672 kg ha−‐1 of N plus adequate P and K. Irrigation maintained soil water pressure above –25 kPa, as indicated by gypsum blocks. Forage from six irrigated and six rain‐fed plots was harvested at eight 24 d intervals. Three‐year average yields for the eight growth periods ranged from 295 kg ha−1 in October to 2907 kg ha−1 in June. Stepwise multiple regression of yields from individual cuttings with various meteorological parameters indicated that daylength was the single most important variable related to yield (r2=0.64). Total rainfall plus irrigation, mean minimum temperature, growing degree days, and mean daily solar radiation could be associated with yield to a limited extent. Over years, yield was most highly correlated with daylength and solar radiation, (r=0.95 and 0.93, respectively,) indicating that these factors were largely responsible for low yields of Coastal bermudagrass forage in the fall. The small correlation between average yields and average temperatures (r=0.46) or average growing degree days (r=0.37) for the eight 24‐d growth periods resulted from the failure of Coastal bermudagrass to grow well in the fall even when water, fertilizer, and temperature were adequate.
An Investigation of the Validity and Usefulness of Trend Analysis for Field Plot Data
Authors: Tamura Roy N. , Nelson Larry A. , Naderman George C.
Published: July 2010

Blocking is sometimes ineffective in accounting for a field's systematic, spatial variation. In such cases, trend analysis has been proposed as an alternative method. This procedure fits a polynomial regression function (surface model) to account for some of the systematic variability. Computer simulated data were used to test the statistical validity of trend analysis. Data simulation facilitated this evaluation, because the experimental conditions of treatment variation, systematic variation, and random variation could be computer generated within prescribed limits. The validity of the significance levels in trend analysis was evaluated. Also, trend analysis was compared to the randomized complete‐block analysis with regard to power of test and estimation of treatment effect. These studies show that with proper restrictions on choosing the surface model, trend analysis has true significance levels close to assumed levels. In addition, trend analysis was often superior to the randomized block analysis in power, and offered less biased estimates of treatment effects, especially when the pattern of systemic variation was complex and curvilinear.
Phosphate Rock Fertilization in Tilled and No‐Till Low‐Input Systems in the Humid Tropics
Authors: Gichuru Mwenja P. , Sanchez Pedro A.
Published: July 2010

Application of phosphate rock is of interest to low‐input systems in the humid tropics, because phosphate rock is less expensive than ordinary superphosphate and releases P quickly in acid soils. However, the lack of incorporation in zero‐tillage systems may result in low availability of surface‐applied P. This study was directed toward determining the effects of these two P sources under no‐till and rotovation tillage systems on crop production in a fine‐loamy siliceous, isohyperthermic Typic Paleudult of Yurimaguas, Peru. A rotation of Al‐tolerant cultivars of rice (Oryza sativa L.)‐rice‐cowpea (Vigna unguiculata) was followed for seven consecutive harvests. Grain yields increased with rotovation in the first crop, were not affected by tillage methods during the second and third crops, but decreased with rotovation from the third to the seventh crops. Sechura phosphate rock at a soil pH of 4.5 was as effective as superphosphate in supplying available P. A total of 13.9 Mg ha−1 of rice and 2.5 Mg ha−1 of cowpea grain was produced in seven harvests in newly cleared fields without lime or P application. There were significant responses to P fertilization in one rice crop and in both cowpea crops. On the average, however, rice yield did not respond to P. A single application of 22 kg P ha‐' was sufficient to produce 85% of the maximum yield of cowpea for 2 yr. The results with cowpea indicate that broadcast phosphate rock is a good source of P for low‐input systems on acid soils where acid‐tolerant cultivars are used.
Tissue Nitrogen Levels For Dryland Hard Red Winter Wheat
Authors: Vaughan B. , Barbarick K. A. , Westfall D. G. , Chapman P. L.
Published: July 2010

Plant tissue analysis could be an effective diagnostic tool for identifying N sufficiency or deficiency at early growth stages for hard red winter wheat (Triticum aestivum L.). This study was conducted to determine critical plant tissue N and NO3‐N concentrations of three plant parts at three growth stages. Nitrogen was applied preplant (fall) at rates of 0, 22, 44, and 66 kg N ha−1 to establish a range of spring plant tissue N levels and grain yields within a location. Critical plant N levels were calculated by the cate‐Nelson procedure. All plant N measurements made at early tiller (Feekes 3) had limited diagnostic value. Late tillering (Feekes 5) and early jointing (Feekes 7) were the best growth stages to sample. Stem and whole‐plant NO3‐N concentrations were highly variable and have limited use for N recommendations. Total N in the whole plant or in the leaves was found to be the best plant part to sample at Feekes 5 and 7 growth stages. Critical N levels recommended for Feekes 5 growth stages are: 32 g kg−1 total N for the whole plant and 38 g kg−1 total N for the leaves. Critical N levels recommended for Feekes 7 growth stage are: 27 g kg−1 total N for the whole plant and 35 g kg−1 total N for the leaves
Day‐Night Temperature Effects on Leaf Expansion and Height of Field‐Grown Corn
Authors: Benoit G. R. , Olness A. , Van Sickle K. A.
Published: July 2010

The effect of constant day/night, average daily, or instantaneous temperatures on plant growth has been extensively documented. Little work has looked at how plant growth under field conditions may be influenced by variations in the day/night temperature combinations experienced. Our objective was to evaluate the effect of day/ night temperature differences on daily corn (Zea mays L.) growth. To accomplish this, corn was grown with and without irrigation (four replications of three planting dates in 1983, 1984, and 1985) on a Hamerly clay (Aerie calciaquoll, fine‐loamy, frigid) at Morris, MN. Hourly soil and air temperature, weekly profile soil water content, and daily precipitation were recorded. Leaf area and plant height were measured daily from eighth leaf to 100% silking. Only plant size data from consecutive days of complete measurements were used with daily maximum and minimum temperatures to establish temperature‐growth rate relations. Leaf area and plant height prediction equations developed from stepwise multiple regression techniques were used to construct percent growth (leaf area and plant height) vs. maximum and minimum temperature response surfaces. Equations were developed for all possible combinations of planting date and irrigation level for each year and all years combined. Combined data showed general relations representative of those shown by individual data sets between percent growth and temperature. Plant height and leaf area predictive equations for combined data have highly significant r2 values of 0.72 and 0.54, respectively. The data shows that percent increase in plant size decreases over time as size at the start of any 24‐h‐growth period increases and that each daily maximum temperature has a successive apparent optimum night temperature for growth.
Soil Acidity and Liming Effects on Stand, Nodulation, and Yield of Common Bean
Authors: Buerkert A. , Cassman K. G. , de la Piedra R. , Munns D. N.
Published: July 2010

The area planted to common bean (Phaseolus vulgaris L.) has been declining in the Southern Mexican State of Chiapas. To determine factors limiting bean productivity in this region, on‐farm experiments were conducted at four locations. Soils were Acrisols (Ustults) at two sites and a Cambisol (Tropept) and Phaeozem (Ustoll) at the other two sites, with pH (H2O) of unlimed soil from 4.6 to 5.0. Insecticide application, genotype, and lime were treatments in a split‐plot design with a factorial combination of two genotypes and 0 or 2000 kg Ca(OH)2 ha−1 as subplots. Across sites, lime addition raised soil pH by 0.4 to 1.3 units, decreased Al saturation by 13 to 38%, and increased extractable Ca two‐to three‐fold. Mean yield without lime was 444 kg ha−1 ha. Insecticide and bean genotype had negligible effects on yield. Lime application resulted in a yield increase of 76 to 313% above unlimed controls across locations. Liming resulted in 40% greater shoot and 18% greater root dry weight, and also improved nodule weight per plant by 110% at early flowering. At maturity, plant density in limed treatments was 23% higher than in unlimed controls, and counts made during the season indicated that soil acidity factors inhibit seedling establishment. Liming also increased pod number per plant by 67%, seed number per pod by 18%, and seed weight by 7%. Increased yield from lime therefore resulted from better stand establishment, and increased seed yield per plant. Increased nodulation and N2 fixation may also contribute to the response to lime.
Domesticated and Wild Tepary Bean: Field Performance with and without Drought‐Stress
Authors: Federici C. T. , Ehdaie B. , Waines J. G.
Published: July 2010

The tepary bean (Phaseolus acutifolius A. Gray) is reputed to be heat and drought tolerant, but the literature contains little information on yield performance of tepary in different conditions. To fill this void, replicated field studies were conducted to measure and compare yield, seed protein concentration, and seed weight of 16 domesticated and eight wild tepary lines at the hot, dry location of Riverside, CA. Well‐watered and drought‐stressed conditions were set up in the summer of 1978. The experiment was repeated with six of the domesticated lines in the spring and summer of 1979. Significant differences were found among the wild lines and among the domesticated lines for the three traits measured. Mean yield and seed weight of wild teparies were 40 and 75% lower than those of domesticates, but mean protein concentration of the two groups was the same (27.6%). Moderate drought‐stress reduced the mean yield of teparies by 55%, but did not reduce protein concentration or seed weight. Seed yield showed a positive correlation with seed weight (r = 0.78), but a negative correlation with seed protein concentration (r = −0.75) in domesticated teparies.
Barley, Lentil, and Flax Yield under Different Intercropping Systems
Authors: Mandal Bijan K. , Mahapatra Susanta K.
Published: July 2010

Intercropping is being adopted as a method of crop production throughout the developing tropics. The objective of this experiment was to assess how the productivity of intercrops was affected by the interaction of irrigation levels and mulches, compared to monocrops. Six‐rowed barley (Hordeum vulgare L.) was intercropped with lentil (Lens culinaris Medik) and flax (Linum usitatissimum L.) with two levels of irrigations [(i) zero and (ii) one irrigation applied 35 d after planting] and two levels of mulch [(i) no mulch and (ii) rice straw mulch at the rate of approximately 7 Mg/ha−1]. Monocrop of each species were also grown. Seed yield of the monocrops were higher than their intercrop yields. Intercropped barley yielded 73 to 81% of the yield to monoculture. Intercropped lentil yielded 30 to 34% of the yield of monoculture, whereas intercropped seed yield of flax ranged from 27 to 31% of monoculture. Yield increased from one application of irrigation ranged from 12 to 21% of zero irrigation. The increase in yield due to straw mulch was 11 to 17% higher over no mulch. The barley‐lentil intercrop recorded higher values of land equivalent ratio (LER) and monetary advantage (MA), and had higher intercropping advantage of area time equivalent ratio (ATER) than the barley‐flax intercrop.
Polyethylene Glycol Solution Contact Effects on Seed Germination
Authors: Emmerich William E. , Hardegree Stuart P.
Published: July 2010

While polyethylene glycol (PEG) solutions have been used to control water potential in numerous seed germination investigations, there is concern that PEG solution‐seed contact may reduce seed germination. The PEG solution‐seed contact effect on seed germination was evaluated on four grass species: sideoats grama [Bouteloua curtipendula (Michaux) Torrey], buffelgrass [Cenchrus ciliaris L.], Lehmann lovegrass [Eragrostis lehmanniana Nees], and kleingrass [Panicum coloratum L.]. A water potential control system for seed germination was developed that controlled PEG (8000 mol. wt.) solution‐seed contact. Seeds were germinated on filter paper and cellulose membrane over the water potential range of 0.0 to −1.62 MPa. Buffelgrass and Lehmann lovegrass 21‐d germination and germination rate index (GRI) were not affected by PEG solution‐seed contact. Sideoats grama and kleingrass showed reduced germination and GRI without PEG solution contact on the cellulose membrane. The reduction was attributed to the hydraulic conductivity at the seedwater‐ membrane contact point which was influenced by PEG solution water potential and seed size and shape. Therefore, it was concluded EG solution‐seed contact does not reduce seed germination.
Modeling the Time Dependence of Nitrogen Uptake in Young Trees
Authors: Wallach D. , Loisel P. , Goffinet B. , Habib R.
Published: July 2010

In order to develop improved fertilization strategies for fruit trees, it is necessary to have a quantitative understanding of the dynamics of N uptake. This study was conducted to select a mathematical model for describing N uptake in young peach trees (Prunus persica (L.) Batsch). In 1985 young peach trees were grown outdoors in Avignon, France, in sand‐filled containers from late February to late September. At each of nine dates total tree N was measured by destructive sampling of three trees. The differences in total N between dates are related to N uptake. The models considered all take the form of a Michaelis‐Menten equation, with maximum uptake expressed as the product of total root weight and uptake efficiency. The models differ in that they express the efficiency factor as different order polynomial functions of time. The criterion used for selecting a best model was related to the squared error of prediction integrated over time. The value of the criterion was estimated for each model, and it was found that the model that expressed efficiency as a third‐order polynomial function of time had the smallest value of the criterion, and was therefore the model of choice. According to this model, N uptake efficiency increased from near zero in mid‐April to a maximum of 3.1 μg N/g root/d in late May, and then decreased again to near zero in late September.
Residual Nitrogen‐15 Recovery by Corn as Influenced by Tillage and Fertilization Method
Authors: Timmons D. R. , Cruse R. M.
Published: July 2010

Tillage systems that create different surface residue conditions may also affect the recovery of residual fertilizer N during subsequent growing seasons. This study evaluated the recovery of residual labeled N fertilizer in the soil by corn (Zea mays L.) for two tillage systems and two fertilization methods. Five atom % 15N‐enriched 28% urea‐ammonium nitrate solution (UAN) at 224 kg N ha−1 was either surface‐applied in the fall before any primary tillage or banded (knifed in) just before planting in the spring. Continuous corn was grown with either fall moldboard‐plow (MP) or ridge‐till (RT) systems. After the initial growing season, the recovery of residual labeled N in the soil by corn was determined for three consecutive growing seasons, and the soil profile was sampled periodically to measure residual ISN in the organic and inorganic pools. One year after labeled UAN application, from 16 to 27% of the initial I5N applied was found in the organic N pool and only 1% as inorganic N[NH4 + (NO2 + NO3)‐N]. After four seasons, residual 15N in the organic N pool ranged from 13 to 24%. Less than 0.5% remained as inorganic N. Regression analyses indicated that about 15N ha−1 yr−1 became available for both MP and RT systems with banded N, so the amounts were small. Total residual I5N recovery by corn grain plus stover for three seasons ranged from 1.7 to 3.5%, and was greatest for spring‐banded fertilizer (p = 0.01). Because the amounts of residual 15N utilized were too small to affect corn growth, this N source appears to be negligible when considering corn‐N needs.
Variable High‐Temperature Tolerance among Kentucky Bluegrass Cultivars
Authors: Howard Harold F. , Watschke Thomas L.
Published: July 2010

The tolerance to chronic high‐temperature stress varies greatly among Kentucky bluegrass (Poa pratensis L.) cultivars. This study of photosynthesis characteristics was conducted to determine whether such traits differ among cultivars and contribute to variable hightemperature tolerance. High‐temperature‐tolerant cultivars exhibited superior growth rates at 30 °C but growth rates were similar among cultivars at 10 °C. At 10 °C, fructosan comprised an approximately two‐fold larger portion of the plant dry weight than at 30 °C, however nonstructural carbohydrate fractions did not differ among cultivars. Under each experimental temperature, the sum of glucose, fructose, and sucrose fractions was approximately the same, though the relative concentrations were temperature dependent. Apparently fructosan served as a buffer fraction that allowed the sum of the other nonstructural fractions to remain constant. Photosynthetic response to increased leaf temperature was similar among cultivars but differed among acclimation temperature regimes. Net photosynthetic rates varied by as much as one‐third among cultivars, however, with a positive relationship between net photosynthetic rates and high‐temperature tolerance. These differences were not attributable to differential CO2 diffusive resistances. This evidence indicated that high‐temperature‐tolerant cultivars were capable of sustaining superior net photosynthetic rates under high but not low temperature conditions. It is suspected that cultivar differences in photosynthetic electron transport capacity may have caused this trend.
Witchweed Management by Sorghum‐Sudangrass Seed Size and Stage of Harvest
Authors: Bebawi Faiz F. , Mutwali Elnasri M.
Published: July 2010

Careful cultural management of field crops has become imperative in countries where chemical measures are not economically feasible. The occurrence of the endemic parasitic witchweed [Striga hermonthica (Del.) Benth] in production fields of sorghum‐sundangrass hybrid [Sorghum bicolor (L.) Moench ✕ S. sudanense Stapf. cv. Piper], Pioneer brand hybrid 988 (coded P988), is one example that requires such procedures. Study objectives were to relate: (i) P988 seed size (large and small) to witchweed germination, P988 root and shoot length, and weight and (ii) P988 seed size and harvest growth stage to P988 greenchop yield and sucrose content at three initial and subsequent P988 harvests at boot stage, late bloom stage, and maturity in witchweed‐infested fields. Seedlings of P988 grown from small seed had significantly shorter shoots but longer roots compared to those from large seed. Witchweed germination was not signficiantly affected by seed size of P988 but was postively correlated to P988 root length and root dry weight. Seed size of P988 had no significant effect on forage greenchop yield and forage sucrose of P988 at all harvests. Delaying initial harvest of P988 increased witchweed shoot dry weight with time and equated total yields, but reduced the quality of greenchop at late bloom and maturity. Delaying second and third harvests of P988 to maturity significantly increased greenchop yield of P988. Forage sucrose at maturity stage of second and third harvests exceeded forage sucrose at maturity of first harvest by 106 and 60%, respectively. Witchweed shoot dry weight was positively correlated with forage sucrose of P988. Growing small seeded P988 reduced witchweed incidence and sustained P988 yields when combined with harvesting at the boot stage on first harvest and at maturity of later harvests on witchweed‐infested soils.
Cotton Response to Starter Fertilizer Placement and Planting Dates
Authors: Guthrie D. S.
Published: July 2010

Effect of planting date on cotton (Gossypium hirsutum L.) response to side‐banded starter fertilizer has not been well documented. Consequently, field studies were conducted in four North Carolina environments to examine the response of cotton to placement of starter fertilier at three planting dates. Cotton planted prior to 5 May (Early), mid‐May (Mid), and late‐May (Late) on a Norfolk loamy sand (fine‐loamy, siliceous, and thermic Typic Kandiudults) and Craven fine sandy loam (clayey, mixed, thermic Aquic Hapludults) received broadcast or side‐banded applications of ammonium polyphosphate at the rate of 17 and 57 kg ha−1 of N and P2O5 respectively. Fertilizer placement had minor effects on plant population. Planting period effects on plant population could not be attributed to heat unit accumulations. Flower production during the first 3 wk of bloom varied with planting period and environment Mid‐ and late‐planting decreased average lint yields across the four environments by 31 and SO%, respectively. Lint yield was increased 9% by side‐banded fertilizer placement. Significant planting period ✕ fertilizer placement interactions were not observed for plant population, flower production, and lint yield. This indicates that applying side‐banded starter fertilizer can benefit producers irrespective of planting date.
Establishment of Two Bermudagrasses in Three Soil Environments
Authors: Mueller J. P. , Green J. T. , Nelson L. A. , Hall J. V.
Published: July 2010

Tifton 44 hybrid bermudagrass [Cynodon dactylon (L.) Pers.], has been reported to be more cold tolerant and to give better animal gains than the hybrid Coastal. It has been observed that Tifton 44 has not established as rapidly as Coastal, frequently taking 2 to 3 yr to achieve complete ground cover. The objective of this work was to determine and quantify differences in the field establishment of Coastal and Tifton 44 grown at three locations for 2 yr on clayey, kaolinitic, thermic Typic Hapludult (Cecil and Mayodan) and loamy, siliceous, thermic Grossarenic (Blanton) soils in North Carolina. A single row of sprigs was set in the center and the length of each 3.1‐ by 6.2‐m plot. Establishment effects were measured by weekly counts of the number of tillers/stolons intercepting a series of transect lines spaced at 0.15‐m intervals on both sides of the sprigged row, and by harvesting the forage produced at the end of the season in 0.30‐ by 6.1‐m increments from the center to the border of each plot. Two establishment indices were developed as the response variables from the transect count data. Analyses of variance were conducted on yield, establishment indices, and on spring ground cover estimates. Yield of forage and establishment characteristics were similar for Coastal and Tifton 44 on the Mayodan soil, but Coastal established more rapidly and produced more forage than Tifton 44 on the Cecil soil in both years of the trial and on the Blanton soil during the first year. In three of six trials, Tifton 44 would have required a 0.3‐ to 0.6‐m row spacing to equal the coverage obtained by Coastal in a 0.9‐ to 1.2‐m row spacing.