bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Green Manure Potential of Austrian Winter Peas in Northern Idaho
Authors: Mahler R. L. , Auld D. L.
Published: July 2010

The objective of this field study was to determine the effect of Austrian winter peas [Pisum sativum spp. arvense (L.) Poir] used as either a green manure (GMP) or seed pea (SP) crop on soil N levels, and yields of subsequent crops of winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.). The Austrian winter pea‐winter wheat‐spring barley (GMP‐WW‐SB) rotation was compared with seed pea‐winter wheat‐spring barley (SP‐WW‐SB), spring barley‐winter wheat‐spring barley (SB‐WW‐SP), and summer fallow‐winter wheat‐spring barley (SF‐WW‐SB) cropping sequences at two sites similar in annual precipitation. After harvest of the initial rotational crop, plots were divided into four subplots and four rates of N were applied as a topdress application following planting of ‘Stephens’ winter wheat. Spring barley was planted the third year. Winter wheat yields, spring barley yields, and inorganic soil N were not significantly affected by rotation ✕ N fertilizer interactions. Winter wheat yield averages following GMP, SP, SF, and SB were 6.6, 6.4, 6.3, and 4.7 Mg ha−1, respectively. Average N feitilizer equivalent values of 94, 75, and 68 kg ha−1 were provided by GMP, SP, and SF, respectively, to the following winter wheat crop. Yield differences resulting from crop rotation or N fertilization rate were not observed in the third year of the cropping sequence. Austrian winter peas used as either a GMP or SP crop provided more inorganic N for the following winter wheat crop than SF or SB. From a 3‐yr total yield the SP‐WW‐SB was the most efficient cropping sequence, as cereal yields were comparable to the GMP‐WW‐SB and SF‐WW‐SB rotations; however, since SP was harvested three crops instead of two (other rotations) were produced.
Nitrogen Fertilizer Carriers and Their Placement for Minimum Till Corn Under Sprinkler Irrigation
Authors: Raun W. R. , Sander D. H. , Olson R. A.
Published: July 2010

Nitrogen fertilizer efficiency is influenced by source of N and how sources interact with different methods of application. This study was initiated to evaluate various N sources and placement methods for sprinkler irrigated corn (Zea mays L.) grown under minimum tillage on a Sharpsburg silty clay loam (fine, Montmorillonitic, mesic Typic Argiudoll) in 1983 to 1985. In general, no differences were found for the yield parameters measured in this study for any of the N methods or N source combinations at 180 kg N ha−1. At the 90 N kg ha−1 grain yields were equal when N was applied broadcast preplant (using urea‐ammonium nitrate, urea, or urea‐ureaphosphate as sources) and when anhydrous ammonia was applied (preplant and sidedressed at the eight‐leaf stage). Both the broadcast preplant and anhydrous ammonia treatments were found to maximize grain yield at the low N rate. Broadcast preplant and anhydrous ammonia treatments provided superior grain yields, fertilizer N uptake in the grain, fraction of N translocated to the grain, and values for harvest index compared with the banding methods employed (dribble surface and band to the side of the seed) at the low N rate. Marked differences were observed in N utilization efficiency as only the banding methods showed fertilizer response above 90 kg N ha−1 while having no advantages over the other methods at 180 kg ha−1. There were generally small differences among N sources although urea‐ureaphosphate did appear to maximize total dry matter yields versus sulfur‐coated urea, urea, and urea‐ammonium nitrate over the 3‐yr period. Measurements made for ear leaf N did not consistently show high positive correlation with grain yield, therefore limiting the use of such a variable for identifying season N deficiencies.
Reducing Iron Toxicity in Rice with Resistant Genotype and Ridge Planting
Authors: Winslow M. D. , Yamauchi M. , Alluri K. , Masajo T. M.
Published: July 2010

Iron toxicity reduces rice (Oryza sativa L.) grain yield in many poorly drained swamps in West Africa. Two methods for alleviating Fe toxicity were examined, (i) the use of a resistant genotype, and l(ii) planting on ridges to aerate the upper root zone. Grain yield responses to these factors were measured in field trials conducted .in an inland valley swamp in southeastern Nigeria over two seasons on a set of paddies ranging from nontoxic to severely toxic. Two genotypes were compared, ITA 212 (susceptible) and ITA 247 (resistant). The severity of Fe toxicity in each paddy was estimated by visually scoring symptoms on ITA 212. Yield decline with increasing toxicity score fit simple linear regressions for both genotypes, but slopes differed significantly. On nontoxic paddies, ITA 212 yielded 10% more than ITA 247, but ITA 247 yielded 10 to 250% more than ITA 212 as toxicity increased from moderate to severe. Ridge planting did not significantly affect grain yield in 1985, but increased it by 245% in 1986 on a severely toxic paddy. The large increase in 1986 was attributed to the use of higher ridges (120 mm above the water surface) than in 1985 (30 mm). In both years the response to ridging was significantly greater when the resistant genotype was used. Resistant genotype and ridging appear to be effective technologies for reducing yield losses on Fe toxic soils, especially when used in combination.
Yield‐Soil Water Relationships in Sorghum‐Soybean Cropping Systems with Different Fertilizer Regimes
Authors: Roder W. , Mason S. C. , Clegg M. D. , Kniep K. R.
Published: July 2010

Crop rotation of soybean [Glycine max (L.) Merr.] with grain sorghum [Sorghum bicolor (L.) Moench], and application of N fertilizer or manure generally increases grain sorghum yield. Little is known about rotation and fertilization effects on soybean yield in the Great Plains. Grain yields were measured from 1981 to 1987 in a cropping experiment started in 1980 on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). The cropping treatments included continuous soybean, continuous grain sorghum, and grain sorghum‐soybean rotation. Fertilizer treatments consisted of control, manure (15.8 Mg dry matter ha−1 yr−11) and N (45 kg ha−1 for soybean and 90 kg N ha−1 for sorghum). Volumetric soil water content was determined with a neutron probe in 1985, 1986, and 1987. Soil water content was unaffected by fertilizer treatment. Water content in the upper 30 cm was generally greatest with continuous grain sorghum and least with continuous soybean. Soil water depletion to 120 cm in September was 10 to 36 mm greater with soybean than with grain sorghum. Crop rotation increased soybean yield, but N application did not. Manure application reduced soybean yield in 1986, but had no effect in the other years. Rotation and fertilization increased sorghum grain yield. The soybean yield advantage from crop rotation decreased as 1 April to 31 May rainfall increased. Cropping‐system induced differences in soil water content early in the growing season may be partly responsible for higher soybean yield with crop rotation.
Calculating Air Leakage Rates in Controlled‐Environment Chambers Containing Plants
Authors: Acock B. , Acock M. C.
Published: July 2010

Air leakage rates from semi‐closed plant growth chambers under elevated CO2 concentration ([CO2]) treatments must be known in order to calculate plant CO2 exchange (CE). It is usually assumed that air leakage rates cannot be measured with plants in the chambers, so air leakage rates are measured before and after each experiment, and assumed to remain constant or vary linearly over time. Variability in leakage rate will diminish the accuracy of calculating CE. A method for calculating air leakage rate at night in the presence of respiring plants was devised. Simultaneous equations for three situations were developed: (i) when respired CO2 = CO2 leaked from chamber; (ii) when [CO2] is maintained at a set level overnight by injection; and (iii) when respired CO2 > CO2 leaked from chamber. All equations were based on two principles: (i) at night, the change in mass of CO2 within the chamber results from a loss of CO2 by leakage and a gain by respiration; and (ii) leakage of CO2 from the chamber is proportional to the difference between chamber [CO2] and ambient [CO2]. Respiration rate is assumed constant during the measurement period. Results are reported for the situation when chamber [CO2] reaches an equilibrium overnight (respired CO2 = CO2 leaked). Air leakage rate was found to have a coefficient of variability as high as 26.2% over eight daily measurements. Errors in calculating CE depend on the magnitude of the leakage rate, its variability, [CO2], and photosynthetic activity. A leakage rate that varied by 10% from two air changes h−1 in the 800 μL L−1 [CO2] treatment chamber could have given a 5% error in calculating CE during a cloudless day and a 14% error during a day with complete cloud cover. Using these procedures, variability in leakage rate can be checked automatically each day, with plants in the chamber, and without monitoring any gas except CO2.
Fraction of Thermal Units as the Base for an Evapotranspiration Crop Coefficient Curve for Corn
Authors: Amos Brigid , Stone L. R. , Bark L. D.
Published: July 2010

A need exists to determine if evapotranspiration (ET) crop coefficient curves, based on a fraction of thermal units concept, could be used across cultivars that require various thermal unit totals from emergence to physiological maturity. Our objective was to develop such a curve for corn (Zea mays L.) and then to test the ability of this curve to estimate ET of cultivars of various maturity lengths. A basal crop coefficient curve for corn was developed by using field data obtained from 1974 through 1982 near Manhattan, KS and during 1981 and 1982 near Tribune, KS. The method involved calculating the ratios of measured ET rates adjusted for surface evaporation to reference ET rates, adjusting these ratios for the amount of available soil water, and then performing regression of the adjusted ratios against fraction of thermal units. The developed basal crop coefficient curve (n = 48, RMSE = 0.11, and R2 = 0.88) was then used to estimate the ET rate of three corn cultivars grown near Manhattan, KS in 1983 and 1984. We then performed linear regression of estimated ET rates against measured ET rates (water balance technique) for each cultivar. All regression equations and coefficients were significant at P < 0.001. The hypotheses that intercept equals zero and slope equals 1 could not be rejected for any of the cultivars. The use of fraction of thermal units as the crop coefficient base scale allowed for a general and accurate use of the basal crop coefficient curve across corn cultivars requiring various thermal unit totals from emergence to physiological maturity.
Cultivar ✕ Tillage Interaction of Hard Red Spring Wheat Cultivars
Authors: Hall E. F. , Cholick F. A.
Published: July 2010

Tillage systems in the spring wheat (Triticum aestivum L.) production areas of the North Central Great Plains are changing to control soil erosion and increase soil water conservation. Therefore, a field study was conducted under three environmental conditions to determine if there was a cultivar ✕ tillage interaction for grain yield, plant establishment, tiller number at boot and maturity, grain volume weight, and plant height. Eighteen adapted hard red spring wheat cultivars were evaluated using two tillage systems, till and no‐till, during 1985 and 1986 on a Beotia silt loam (fine‐silty, mixed, Pachic Udic Haploboroll) and during 1986 on an Aberdeen silt clay loam (fine, montmorillontic, glossic Udic Natriboroll). There was a significant cultivar ✕ tillage interaction for grain yield, with a range from a 9.8% increase to a 11.6% decrease depending on cultivar when examined over all environments. There was a cultivar ✕ tillage interaction for seed weight (P = 0.07) and grain yield (P < 0.05). Stand establishment was superior at all locations in no‐till. Tillering at various growth stages did not explain grain yield differences. This study indicated that selection under no‐till should be considered to more efficiently develop spring wheat cultivars for no‐till production systems.
Water‐Use Efficiency and Light Interception of Semidwarf and Standard‐Height Sunflower Hybrids Grown In Different Row Arrangements
Authors: Zaffaroni Eduardo , Schneiter A. A.
Published: July 2010

Semidwarf sunflower (Helianthus annuus L.) may have potential for adaptation in large areas where conventional‐height sunflowers are currently grown. To develop improved production practices for this plant type, a better understanding of light and water use is needed. The objective of this study was to evaluate light interception, water‐use efficiency (WUE), and energy‐use efficiency (EUE) of semidwarf (SD) and standard‐height (SH) sunflower hybrids grown under various row spacings. Field studies were conducted at Prosper, ND during the 1984 and 1985 growing seasons. Row arrangements consisted of (i) conventional rows, spaced 0.76 m apart; (ii) solid seeding, rows spaced 0.38 m apart; and (iii) twin rows, two rows 0.19 m apart on 0.76‐m centers at populations of 35 000, 50 000 and 65 000 plants ha−1. Soil‐water depletion at different levels of the soil profile was similar for both plant types during 1984, but statistically greater for the SH hybrid during 1985. In general, soil‐water depletion was greater under solid seeding both years. Total water use (WU) and WUE were not statistically different between hybrids or among row arrangements in combined analysis across years. In 1985, WUE was statistically higher for the SD hybrid (4.69 kg ha−1 mm−1), as a result of decreased yield in the SD hybrid caused by Sclerotinia head rot (Sclerotinia sclerotiorum). Light interception among treatments was not different in 1984, but in 1985 was higher for sunflower sown at solid seeding and twin rows than in conventional rows. Energy‐use efficiency was not different among treatments in 1984, while in 1985, the SH hybrid had statistically higher values (1.29%). During this year EUE significantly increased from 0.99 to 1.33% as plant population increased.
Infrared Thermometry to Measure single Leaf Temperatures for Quantification of Water Stress in Sunflower
Authors: Nielsen D. C. , Anderson R. L.
Published: July 2010

Quantification of water stress by infrared thermometry is routinely done on complete plant canopies to minimize the influence of viewed soil surface. When plants are small or widely spaced, canopies may not be complete. This study was conducted to determine if Crop Water Stress Index (CWSI) values computed from infrared thermometer measurements of single‐leaf temperatures of sunflower [Helianthus annuus (L.) ‘Triumph 566DW’] were correlated with other measures of plant water stress. Plants were grown under an automated rainout shelter and subjected to four water treatments ranging from 0.0 to 100% replacement of evapotranspirational losses. The soil type is a Rago silt loam (fine, montmorillonitic, mesic Pachic Argiustoll). Statistically significant correlations were found between CWSI calculated from single‐leaf temperatures and stomatal conductance, CO2 exchange rate, leaf water potential, transpiration rate, and percent available water in the active root zone. Calculating CWSI from single‐leaf temperatures measured with an infrared thermometer can provide a rapid means of assessing plant water status in incomplete canopies.
Bermudagrass Response to Leaching Fractions, Irrigation Salinity, and Soil Types
Authors: Devitt D. A.
Published: July 2010

Reuse of wastewater as an irrigation source for turfgrass is becoming a more viable and appealing option in arid environments where competition for good‐quality water is increasing. The objective of this research was to determine the impact that varied leaching fractions, irrigation salinity, and soil types had on root growth and distribution, and fractional water uptake of bermudagrass [Cynodon dactylon (L.) Pers.]. Bermudagrass was grown for a 2‐yr period in large columns packed with three different soil types (sandy loam, silt loam, and clay). Saline water was synthesized and applied at three different salinity levels (electrical conductivities of 1.5,3.0,and 6.0 dS m−1). Irrigations were applied 3 d wk−1 at a rate beyond measured evapotranspiration (ET) to establish three different leaching fractions (0.09, 0.18, and 0.27). The soil salinity (ECe), soil solution chloride (CI−), root density, and volumetric water contents were measured in soil cores taken with depth and time. Dry matter of weekly grass clippings was measured and recorded throughout the 2‐yr period. Plant water status was monitored by measuring canopy temperatures and leaf xylem water potentials. Results indicated that bermudagrass was very tolerant to the range of salinity‐leaching conditions imposed. However, differences were noted by treatments, with the sandy soil showing as much as a 25% yield decrement at the highest salinity level. Salinity of the irrigation water (ECI), rather than soil salinity (ECe), was more highly correlated with most of the soil‐plant‐water relationships observed. Root length density was best described by a hyperbolic function. Only limited success was found in correlating root length density with fractional water uptake. In addition, poor correlations were found between soil salinity with depth and fractional water uptake. These findings indicate that the ability to predict water uptake based on root distribution and/or soil salinity would be poor and that great error might occur in using such an approach in predictive models.
Soil and Tissue Nitrate Tests Compared for Predicting Soil Nitrogen Availability to Corn
Authors: Fox R. H. , Roth G. W. , Iversen K. V. , Piekielek W. P.
Published: July 2010

Mounting concern about NO3 pollution of the nation's ground and surface waters make accurate N‐fertilizer recommendations increasingly important. A study was initiated in 1984 to determine if presidedress soil or corn stalk (Zea mays L.) NO3 concentrations could be used to predict soil N availability and the need for sidedress N fertilizer. Nitrate concentration was determined in the surface 30 cm of soil and in the lower 10 cm of corn stalks 22 to 37 d after emergence (corn was in the 5‐ to 6‐leaf stage). Eighty‐seven N‐response experiments were conducted over a 4‐yr period in central and southern Pennsylvania. A number of these sites were on fields that had received high rates of manure in the past. Corn stalk NO3 concentration was not an accurate predictor of soil N availability nor of the probability that a site would respond to N fertilizer. The NO3 concentration in the surface 30 cm of soil 4 to 5 wk after emergence was a good indicator of whether a response to sidedress N fertilizer would be attained. The best critical level for separating responsive from nonresponsive sites was 21 mg NO3‐N kg−1. No sites responded to N fertilizer when the soil NO3‐N concentration was greater than 25 mg kg−1. Soil NO3 concentration and soil N‐supplying capability (NSC) at soil NO3 levels below the critical level were not correlated well enough (r2 = 0.34) to use the predicted NSC for adjusting N‐fertilizer recommendations. As a result, the best use of this test in Pennsylvania appears to be in identification of nonresponsive sites rather than predicting N‐fertilizer rates. Use of this test by farmers in Pennsylvania will help minimize the practice of applying “insurance” N when N contributions from manure and legumes in rotations are uncertain.
Chemical Regulation of Alfalfa/Grass Mixtures with Imazethapyr
Authors: Fales S. L. , Hoover R. J.
Published: July 2010

Growth regulators can improve forage grass quality, but they have not been evaluated for quality enhancement with grass‐legume mixtures. A field experiment was conducted for 2 yr to investigate the effects of applications of imazethapyr [5‐ethyl‐2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl) nicotinic acid] on production and quality of alfalfa (Medicago sativa L.) /grass mixtures. Mixtures of alfalfa with either orchardgrass (Dactylis glomerata L.), ryegrass (Lolium perenne × L. multiflorum Lam.), reed canarygrass (Phalaris arundinaceae L.), smooth bromegrass (Bromus inermis Leyss.), or timothy (Phleum pratense L.) were established on a Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf) and were treated with imazethapyr at application rates of 0, 25, 50, and 100 g a.i. ha−1. Results showed first‐harvest mean (mean of rates and grass species) grass crude protein (CP), in vitro dry matter disappearance (IVDMD), and neutral detergent fiber (NDF) of 128,643, and 622 g kg−1, respectively compared with 108, 623, and 654 g kg−1, respectively for controls. Alfalfa was unaffected by treatments. Changes in CP, IVDMD, and NDF concentrations with increasing imazethapyr levels showed significant linear and quadratic components for first harvest in 1986, but showed only a linear trend in 1987 due to reduced effectiveness of the 25 and 50 g ha−1 treatments the second year. Second‐ and third‐harvest quality trends were inconsistent both years. Controls averaged 21% grass at first harvest in 1986 and 37% in 1987, whereas imazethapyr lowered first harvest grass percentage to 13 and 22%, respectively for the 2 yr. In 1986, treated plots showed enhanced grass regrowth at second cutting, but the same was not observed in 1987. Consequently, treatments did not affect seasonal yield in 1986, but resulted in a mean reduction of 0.6 Mg ha−1 in 1987. Where forage quality of alfalfa/grass hay is paramount, imazethapyr may be an effective management tool.
Chemical Regulation of Growth and Forage Quality of Cool‐Season Grasses with the Imazethapyr
Authors: Fales S. L. , Hill R. R. , Hoover R. J.
Published: July 2010

Forage quality in cool‐season grasses declines rapidly in the spring primarily due to the production of relatively indigestible stem tissue. This study was conducted to evaluate the ability of the plant growth regulator, imazethapyr [5‐ethyl‐2‐(4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl) nicotinic acid], to constrain losses in grass quality by reducing rates of neutral detergent fiber accretion and by maintaining levels of crude protein and in vitro dry matter disappearance. In 1986 and 1987 field plots of ‘Pennlate’ orchardgrass (Dactylis glomerata L.), ‘Bison’ ryegrass (Lolium perenne L. × L. multiflorum Lam.), ‘Palaton’ reed canarygrass (Phalaris arundinacea L.), ‘Saratoga’ smooth bromegrass (Bromus inermis Leyss.), and ‘Toro’ timothy (Phleum pratense L.) were treated with imazethapyr, at rates of 0, 25, 50, and 100 g a.i. ha−1. Plots were sampled at weekly intervals for 7 wk after imazethapyr application in the spring. Treated forage averaged between 36 and 71 g kg−1 lower in neutral detergent fiber, between 19 and 44 g kg−1 higher in vitro dry matter disappearance, and between 9 and 20 kg−1 higher in crude protein, depending on the level of imazethapyr applied. Improvements in quality were accompanied by corresponding dry matter yield reductions, which ranged between 0.8 and 2.8 Mg ha−1. Rates at which yield increased or quality decreased as the season progressed were reduced by higher rates of imazethapyr application. Imazethapyr appears to be an effective tool for manipulating the growth and nutritive quality of cool‐season grasses.
Foliar‐Applied Daminozide Effect on the Yield and Tuber Size Distribution of Potato
Authors: Sanderson J. B. , White R. P. , Platt H. W. , Ivany J. A.
Published: July 2010

This study investigated the effects of foliar applied daminozide (butanedioic acid mono 2, 2‐dimethyl hydrazide, Alar 85, Uniroyal Chemical, Inc.) on two potato (Solanum tuberosum L.) cultivars, Kennebec and Red Pontiac, field grown with six replications over 3 yr at Charlottetown, Prince Edward Island, Canada. Four treatments were evaluated in 1985: (i) control, (ii) 0.42 kg daminozide ha−1 applied when largest tubers reached 20 mm, and (iii) 0.85 kg daminozide ha ' applied when largest tubers reached either 20‐min or (iv) 30‐mm stage. The treatments evaluated in 1986 and 1987 were: (i) control, and (ii) 0.85 kg daminozide ha−1 applied when the largest tubers had reached either the 10‐mm, (iii) 20‐mm, or (iv) 30‐mm stage. Daminozide did not significantly affect foliar or tuber disease levels, nor total tuber yield, but an increase of 2.36 t ha−1 in the seed size tuber yield did result from a 0.85 kg daminozide ha−1 application at the 30‐mm tuber size stage. Differences in cultivar responses occurred at earlier tuber size stages. Application of daminozide modified the tuber size distribution of the potato crop, however considering the cost of daminozide, its potential value to seed potato producers is questionable.
Growth Analysis of ‘Florigraze’ Rhizoma Peanut: Forage Nutritive Value
Authors: Saldivar A. J. , Ocumpaugh W. R. , Gildersleeve R. R. , Moore J. E.
Published: July 2010

‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a perennial tropical forage legume grown in Florida and the southern Gulf Coast. Two field studies were conducted near Gainesville, FL on Arredondo loamy sands (loamy, siliceous, hyperthermic, Grossaremic Paleudults) in 1980 and 1981. The objective of these studies was to evaluate nutritive value of Florigraze topgrowth as measured by crude protein (CP) and in vitro digestible organic matter (IVDOM). Experiment 1 was an establishment‐year growth analysis study conducted at two sites (years). Experiment 2 was a defoliation‐frequency study (0 vs. 2, 6, and 8 wk) conducted in 1981 on plants that were undisturbed at the 1980 site. Samples were taken periodically during the growing season in both years. In Exp. 1, both CP and IVDOM concentrations were characterized by two‐stage curves, where CP and IVDOM declined linearly (−0.9 and −0.7 g kg−1 d−1) until September, then stabilized at 125 and 610 g kg−1, respectively. Leaves constituted 60 to 80% of top growth in both years. In Exp. 2, CP and IVDOM declined linearly (−0.3 and −1.0 g kg−1 d−1) during the growing season for all defoliation treatments. Decline in percent leaf in the established plants of Exp. 2 was twice that of undisturbed plants in Exp. 1: −0.10 vs. −0.05 percentage units d−1. There was a sampling date × defoliation treatment interaction (P < 0.001) in percent leaf. Values for undefoliated plants were similar to that of Exp. 1, but leaf percentages declined at increasing rates in all defoliation treatments. At four dates in Exp. 1 and three dates in Exp. 2, top growth was separated into leaves and stems for IVDOM analysis. Leaf IVDOM declined linearly (−0.3 g kg−1 d−1), while stem IVDOM declined and then increased slightly from September through December. The data suggested that leafiness can be altered by defoliation management, and in turn, leafiness influences forage nutritive value of Florigraze rhizoma peanut.
Carbon Dioxide and Water Level Effects on Yield and Water Use of Winter Wheat
Authors: Chaudhuri U. N. , Kirkham M. B. , Kanemasu E. T.
Published: July 2010

Increasing levels of atmospheric CO2 may have major effects on yield and water use of winter wheat (Triticum aestivum L.). The objective was to determine the effect of elevated levels of CO2 on grain yield and water use from planting to harvest under two water levels. ‘Newton’ winter wheat was grown in the field under ambient (340 µL/L) and elevated levels (485, 660, and 825 µL/L) of CO2, during three growing seasons, in 16 underground boxes (77 cm long, 37 cm wide, and 180 cm deep) containing a Muir silt loam (finesilty, mixed, mesic Cumulic Haplustoll). Water in half of the boxes was maintained at 0.38 m3/m3 (high water level) and in the other half between 0.14 to 0.25 m3/m3 (low water level). Boxes were weighed in the fall and spring to determine the amount of water use by transpiration. Plastic chambers (121 by 92 by 168 cm) covered the boxes to maintain different CO2 levels. Grain yield of the high‐water‐level wheat grown under ambient CO2 was about the same as the grain yield of low‐water‐level wheat grown at the highest level of CO2 (825 µL/L) (3‐yr means: 725 and 707 g/m2, respectively). Similar results were obtained for yield components (spike number, spike weight, kernels/spike, and kernel weight). High‐water‐level wheat grown with 825 µL/L CO2 transpired more water than low‐water‐level wheat grown under ambient levels of CO2 (3‐yr means: 453 and 370 L/m2, respectively). Under high and low water levels, 29 and 31% less water was required, respectively, to produce a gram of grain when the CO2 concentration was raised from ambient to 825 µL/L. Results show that the water requirement of wheat is reduced by about 30% by elevated (1.4 times present ambient) CO2.
Respiration Measurements of Maize Plants Using a Whole‐Plant Enclosure System
Authors: Berard R. G. , Thurtell G. W.
Published: July 2010

Field‐portable enclosure systems are useful in assessing the impact of environmental parameters on crop growth rates and yields. These systems are normally designed to measure only one aspect of the C exchange budget, either the incoming (net photosynthesis) or outgoing (respiration) C fluxes. The objective of this work was to enable a whole‐plant enclosure system, originally designed exclusively for field measurements of photosynthesis and transpiration, to be used additionally for respiration measurements. The conversion from photosynthesis to respiration measurement was relatively simple and required minimal modifications to the existing system. The technique basically involved substituting CO2‐free air for CO2 as the gas being injected into the chamber to maintain a constant [CO2] within the chamber. Precise monitoring of air flow rate into the chamber allowed calculation of the whole‐plant respiration rate. Calibration tests indicated that the system was accurate to within <5% of typical respiration rates. Nighttime measurements on the whole maize (Zea mays L.) plants yielded respiration rates typical of those reported in the literature. The system could be left unattended throughout the night during respiration measurements, and could be converted back to daytime photosynthesis measurements within a few minutes. The ability of the enclosure system to provide constant day/night monitoring of whole‐plant C exchange makes it a valuable tool in the study of environmental factors affecting the above‐ground carbon balance of maize plants.
Rice Photosynthesis and Evapotranspiration in Subambient, Ambient, and Superambient Carbon Dioxide Concentrations
Authors: Baker J. T. , Allen L. H. , Boote K. J. , Jones P. , Jones J. W.
Published: July 2010

The current global rise in atmospheric carbon dioxide concentration, [CO2], has stimulated interest in the response of agricultural crops to [CO2]. The objectives were to determine the effects of [CO2] on photosynthesis, evapotranspiration, and water use efficiency of rice (Oryza sativa, L., cv. IR‐30). Rice plants were grown in naturally sunlit, plant growth chambers in subambient (160 and 250), ambient (330), or superambient (500, 660, and 900 μmol CO2 mol−1 air) [CO2] treatments. Photosynthetic light response curves were analyzed to obtain estimates of canopy light utilization efficiency (α) and canopy conductance to CO2 transfer (τ). Estimates of ℵ increased with increasing [CO2] treatment with the greatest increase in the 160 ito 500 μmol mol−1 treatments. Estimates of were more variable tham those for τ and were not different among [CO2] treatments. Photosynthetic rates increased with increasing [CO2] treatment from 160 to 500 μmol mol−1 followed by a leveling off of the response among the superambient [CO2] treatments. Evapotranspiration decreased while water‐use efficiency increased with increasing [CO2]. Shortterm cross‐switching of [CO2] among the chambers revealed a profound adaptive response to long‐term [CO2] growth treatments. Photosynthetic rate, measured at a common [CO2], decreased with increasing long‐term [CO2] growth treatment. The lack of further Photosynthetic response above the 500 μmol mol−1 [CO2] treatment appears to indicate a need to select or screen rice cultivars for increased response to superambient [CO2] in order to more fully take advantage of future increases in global atmospheric [CO2].
Growth Responses, Ion Relations, and Osmotic Adaptations of Eleven C4 Turfgrasses to Salinity
Authors: Marcum K. B. , Murdoch C. L.
Published: July 2010

Shortages of fresh water, coupled with soil salinization in many areas have resulted in an increased need for salt tolerant turfgrasses. This study was conducted to compare growth and physiological responses of eleven C4 (grasses which utilize the C‐4 carboxylic acid pathway in photosynthesis) turfgrasses to salinity. Grasses were grown in solution culture in a glasshouse, with NaCl added to achieve salinities of 0.7, 10, 20, and 30 dS m−1 (0, 99, 198, and 298 mM NaCl). Grasses were ranked for salinity tolerance according to their relative top growth reductions with increasing salinity. Tolerant grasses included a Hawaii selection of seashore paspalum (Paspalum vaginatum Swartz), two St. Augustinegrasses (Stenotaphrum secondtum Walt.), and manilagrass (Zoysia matrella L.). Bermudagrasses (Cynodon spp. (L.) Pers. Burtt‐Davey) tested were generally less tolerant to salinity. Shoot and root Na and CI concentrations reached very high levels in St. Augustinegrasses, and were relatively high in seashore paspalum and Japanese lawngrass (Zoysia japonica Steud.). In contrast, manilagrass and bermudagrasses maintained low levels of Na and Cl under high salinity which is indicative of ion regulation, due in part to efficient leaf salt glands. Seashore paspalum maintained higher shoot and root K concentrations under high salinity than did other grasses. All grasses adjusted osmotically under increasing salinity. Although St. Augustinegrasses and seashore paspalum accumulated Na and Cl in the shoots to relatively high levels, they maintained much higher tissue water levels than did other grasses, resulting in intermediate sap osmolalities.
Early Growth and Dinitrogen Fixation by Arrowleaf Clover in Response to Starter Nitrogen
Authors: Schomberg H. H. , Weaver R. W.
Published: July 2010

Seedling vigor of arrowleaf clover (Trifolium vesiculosum L. Savi) is poor but it may be enhanced by application of starter mineral N. Three experiments were conducted using a growth chamber and a glasshouse to determine the influence of starter mineral N and strains of Rhizobium leguminosarum biovar trifolii on dry matter production and N2 fixation of arrowleaf clover. In one experiment, seeds were planted in a N‐deficient medium, inoculated with two strains of rhizobia and provided with five levels of mineral N. The lowest level of mineral N doubled seedling dry weights and the amount of biologically fixed N in 40‐d‐old seedlings. Rhizobial strain interacted with mineral N in influencing dry matter production and N2 fixation. To further examine the influence of rhizobial strain, five additional strains varying in effectiveness were evaluated in a second experiment. Mineral N provided to plants inoculated with any strain increased dry matter production and N2 fixation. To aid in extrapolating the response of arrowleaf clover seedlings to mineral N, seed were sown into undisturbed soil cores from four fields. The cores were fertilized with the equivalent of 0, 31, and 62 kg N ha−1. Fertilization with 31 kg of N did not reduce N2 fixation by plants grown on cores of soil collected from three fields and dry matter production was nearly doubled on cores from two fields. Providing some mineral N to arrowleaf clover seedlings greatly enhanced seedling vigor.
Exact Equations for Calculating Air Leakage Rates from Plant Growth Chambers
Authors: Kimball B. A.
Published: July 2010

The rates of leakage of CO2 from plant assimilation chambers must be known in order to correct measurements of net photosynthesis and respiration for this unwanted but omnipresent source of error. Similarly, in order to precisely calculate heating or cooling requirements for plant growth structures, air leakage or “infiltration” must be known. The objective of this paper is to derive theoretically exact equations for calculating such leakage rates from measurements of CO2 concentration [CO2]. The needed equations were derived from the solution of a basic differential CO2 balance equation. The procedure presumes the determination will be done when plant CO2 exchange is steady, a condition most nearly satisfied by respiration near the end of the night. The equation had two unknowns, respiration and leakage rate. From measurements before and after a CO2 perturbation, it was possible to derive sets of two equations with two unknowns, which were then solved for the respiration and leakage rates. In contrast to prior work, the new equations are theoretically exact, and they can account for changes in ambient [CO2] during the measurement periods and also for differing rates of CO2 injection before and after the perturbation. Moreover, these theoretically exact equations are no more complex than the prior approximate equations for a couple of practical cases. Calculations for three specific cases showed the approximation used in the prior equations introduced errors of 0.8, 5.5, and 1.6%. Thus, using these equations derived in this paper should permit more accurate calculations of leakage rate and ultimately, therefore, more accurate determinations of gas exchange rates from plants in assimilation chambers as well as of the heating or cooling requirements of the chambers themselves.
Root Development of 12 Forage Legumes as Affected by Temperature
Authors: Brar G. S. , Gomez J. F. , Matches A. G. , Taylor H. M. , McMichael B. L.
Published: July 2010

Legumes with roots that elongate rapidly over a wide temperature range should have improved seedling establishment semiarid regions. We determined effects of 10, 15, 20, 25 and 30 °C temperature on main axis and lateral root growth of 12 forage legumes in germination chambers. Legumes differed (P < 0.05) in both main axis root length and lateral root development over temperatures and there were significant (P ° 0.05) entry by temperature interactions. There were significant positive non‐linear correlations with (R2,) of 0.72, 0.68 and 0.76 at 15, 20 and 25 °C temperatures, respectively, between seed weight and main axis root elongation.
Impact of Insect Feeding on Alfalfa Regrowth: A Review of Physiological Responses and Economic Consequences
Authors: Hutchins Scott H. , Buntin G. David , Pedigo Larry P.
Published: July 2010

Insect‐induced injury to alfalfa, Medicago sativa L., has been a frequent topic of research. The central focus of many investigations has been the physiological response of alfalfa to insect feeding, measured as altered root carbohydrate levels, canopy development, and forage feeding value. Leaf‐mass consuming insects generally either remove leaf tissue in aerial portions of established canopies (e.g., alfalfa weevil, Hypera postica [Gyllenhal]) or consume new foliage during early regrowth (e.g., variegated cutworm, Peridroma saucia [Hubner]). In both instances, injury results in an initial reduction in leaf‐to‐stem biomass (L/S) ratio. Continued defoliation, however, affects canopy photosynthesis to the point that stem growth is slowed. Assimilate‐removing insects (e.g., potato leafhopper, Empoasca fabae [Harris]), disproportionately reduce stem growth compared to leaf growth, resulting in a higher L/S ratio. Although specific host response varies across the range of piercing‐sucking insects, herbage feeding value per plant mass is generally enhanced with the increased L/S ratio. Overall, insect‐induced changes in yield and quality from leaf‐mass and assimilate removal consequentially reflects a delay in maturity. From a crop management perspective, slowed phenological development may alter harvest schedules or disrupt necessary root carbohydrate regeneration. Specific knowledge of host response, combined with current economic circumstances, should serve as a basis for developing economic injury levels to manage insect pests.
Sunflower Production as Influenced by Plant Type, Plant Population, and Row Arrangement
Authors: Zaffaroni Eduardo , Schneiter A. A.
Published: July 2010

Semidwarf sunflower (Helianthus annuus L.) hybrids recently became available to producers. Information on the response of this plant type to different cultural practices is limited. Field studies were conducted at two locations in 1984, 1985, and 1986, to determine the effect of different row arrangements and plant populations on yield, yield components, and other agronomic traits of a semidwarf (SD) and a standard height (SH) sunflower hybrid. Plant populations evaluated were 35 000, 50 000, and 65 000 plants ha−1. Row arrangements evaluated consisted of (i) conventional rows, spaced 0.76 m apart, (ii) solid seeded rows, spaced 0.38 m apart, and (iii) twin rows, two rows 0.19 m apart on 0.76 m centers. A path coefficient method was used for yield component analysis. Analyses across environments indicated no statistical differences for yield among hybrids, plant populations, or row arrangements. Significant environment ✕ hybrid, environment ✕ row arrangements and environment ✕ arrangement ✕ population interactions on yield were found. The SH type outyielded the SD at all environments, although statistically significant differences were found in only four of the six environments. In general, plant population and number of seeds per head were the yield components having the greatest direct effect on yield. The direct response of plant population was masked by the negative effect of seeds per head and seed weight, resulting in a low coefficient of correlation. Harvest index of SH (36%) was statistically higher than for the SD (32%). The difference was due to the heavier receptacle of the SD. This indicates that possibilities exist to improve semidwarf genotype yield by reducing receptable weight.
Simultaneous Selection for High Yielding and Stable Crop Genotypes
Authors: Kang M. S. , Pham H. N.
Published: July 2010

Integration of stability of performance with yield is essential in yield trials. Methods that select for high yield and stability have been developed, but have not been compared for their usefulness. Our objective was to compare these methods and to study their relationship to yield and the stability‐variance statistic (σ2i). We compared Kang's (1988b) rank‐sum method (Index 1; equal weights for yield and σ2i) and four additional rank‐sum indices [two (Index 2), three (Index 3), four (Index 4), and five (Index 5) times more weight for yield than for stability variance] with Hühn's (1979) S3i and S6i statistics, and Lin and Binns' (1988) Pi. All statistics were calculated for each of five sets of data from international maize (Zea mays L.) yield trials. In Set 1, low σ2i's (indicative of stable performance) were generally associated with high yield (r3 = 0.73), but in Set 2 low σ2i's appeared to be associated with low yield (r3 = −0.46). Index 1 ranks were positively correlated with σ2i ranks in Sets 2 to 5 as were S3i ranks. Index 1 and S3i offered an opportunity to select for both stability based on σ2i and yield. Indices 2, 3, 4, and 5, and Pi favored selection primarily for yield. It was assumed that the top 50% genotypes would be selected, in Sets 1 and 2, on the basis of yield rank alone or individual statistics. In Set 1, Index 1 was slightly more conservative than S3i, in that Index 1 selected a higher yielding genotype from the two lowest yielding genotypes than did S3i. S6i was slightly more conservative than Index 1. Index 1 was intermediate between S3i and S6i. In Set 2, Index 1 and Index 2 were more conservative than σ3i, whereas σ6i was more conservative than Index 1, but less conservative than Index 2. Pi favored selection for yield only. We concluded that Kang's rank‐sum method (Index 1 here) and Hühn's S3i and S6i statistics would be useful for simultaneously selecting for yield and yield stability.
Timing and Nature of Mulch Retardation of Corn Vegetative Development
Authors: Fortin M.‐C. , Pierce F.J.
Published: July 2010

Low soil temperatures that are induced by crop residue have been shown to delay corn (Zea mays L.) development. The exact conditions under which retardation takes place and whether the delay is only due to thermal effects still need to be elucidated. This study was conducted to characterize corn vegetative development, with and without residue cover, and to determine if differences in seed‐zone temperature account for the differences in development. The effects of an oat (Avena sativa L.) straw mulch and an inert poplar excelsior (Populus) mulch, applied at second leaf tip emergence and at the time of full extension of the fourth leaf, on seed‐zone temperature, time, and thermal time (daily temperature accumulation) between specific vegetative stages, were investigated on a Conover loam (mixed, mesic, Udollic Ochraqualf) under irrigated conditions. Developmental delays occurred as average soil maxima temperatures, under the mulches, were 2.2 °C lower than the bare soil control. When mulches were applied at second leaf tip emergence, soil temperature‐based thermal time was significantly higher for the oat mulch than for the popular mulch or the bare soil, until the full extension of the fourth leaf in 1988 and the third leaf in 1989. Modeling equations derived from CERES‐MAIZE accurately predicted thermal times to the full extension of the third leaf and sixth leaf for most treatments, but underestimated thermal time for the 1988 oat mulch. When applied at full extension of the fourth leaf, oat straw had minimal effects on development. The differences in thermal time due to the two mulches during the early vegetative stages of corn, suggest that in addition to soil temperature, allelopathy from oat straw may be a source of developmental delay and that its occurrence is weather‐dependent.
Apical Development of Spring Barley in Relation to Chlormequat and Ethephon
Authors: Ma B. L. , Smith D. L.
Published: July 2010

There is considerable interest in the use of plant growth regulators (PGR) to control lodging in spring barley (Hordeum vulgare L.), and to increase the number of spike‐bearing tillers through early application. Application of PGR is likely to have effects on the development of reproductive structures in both main‐stem and tiller apices. The objective of this study was to investigate the timing and dynamics of barley main‐stem apical development as influenced by chlormequat chloride (2‐chloroethyl trimethylammonium chloride; CCC) or ethephon (2‐chloroethyl phosphonic acid) treatment. A 3‐yr field study using widely grown cultivars, ‘Leger’ and ‘Cadette’, was conducted on Bearbrook clay soil (fine, mixed nonacid, mesic Humaquept) at Emile A. Lods Agronomy Research Centre, McGill University, Canada, from 1987 to 1989. Treatments consisted of application with CCC and ethephon at Zadoks growth stages (ZGS) 13, 30, and 39. Data were collected on growth regulator induced plant changes in (i) external morphological characters, (ii) apical development, and (iii) spikelet primordium abortions. Application of CCC at ZGS 13 retarded development of the main‐stem apex from shortly after application to awn elongation and reduced the number of aborted spikelet primordia. Unlike CCC, the retarding effect of ethephon on main‐stem apical development was not shown until a few days after its application (when the maximum number of main‐stem primorida was reached), which may have promoted tiller survival. In general, the application of PGR reduced the apical dominance of dominant sinks (main‐stem apex and/or central spikelets of the rachis) allowing the survival and greater development of more subordinate sinks (tillers and/or distal rachis spikelets).