bluuebunny/crossref_metadata_2025 huggingface dataset:
A Detrimental Interaction of Subsoil Aluminum and Drought Stress on the Leaf Water Status of Soybean
Authors: Goldman I. L. , Carter T. E. , Patterson R. P.
Published: July 2010

Drought and subsoil Al are major concerns which face soybean [Glycine max (L.) Merr.] producers in the southeastern USA. However, the interaction of these two factors is not clearly understood. This study was designed to characterize the combined effect of these two stress factors on soybean water status. A greenhouse experiment was conducted, with two levels of subsoil Al saturation (6 and 71%), and two levels of drought stress (watered and unwatered). A split plot experimental design with three replications was employed. Soil treatments were applied via a soil layering technique using topsoil of a Goldsboro sandy loam (fine‐loamy, siliceous, thermic, Aquic Paleudult). The top layer in all pots consisted of the unamended topsoil. In the lower layer, highly contrasting Al saturation levels were obtained by amending one half of the pots with Al2(SO4)3. Data were collected during a 14‐d moisture stress treatment imposed at podfilling (R3). Traits measured were leaf water potential, relative water content, transpiration, and diffusive resistance. A detrimental interaction between subsoil Al and drought was observed in all traits measured. Plants grown in the presence of both stress factors had lower levels of leaf relative water content and water potential, and a lower transpiration rate than predicted additively by independent stress factors. In general, subsoil Al had much greater effects on leaf water status in drought‐stressed soybean plants than in the wellwatered plants. These results suggest that hindered root growth in highly Al‐saturated subsoils may have limited the ability of the plant to withstand drought. Soybean producers in regions characterized by drought and subsoil Al should consider the incorporation of Altolerant germplasm into management systems. Field studies including water stress as a variable should be interpreted with regard to this interaction, if soil A1 is present.
Least Significant Differences for Combined Analyses of Experiments with Two‐ or Three‐Factor Treatment Designs
Authors: Carmer S. G. , Nyquist W. E. , Walker W. M.
Published: July 2010

Many agronomic experiments with complete factorial treatment designs are conducted in two or more environments. If at least one of the treatment factors is qualitative, the combined analysis may appropriately include pairwise comparisons of various treatment means averaged over environments. Heretofore, however, formulae for estimation of the variances of pairwise mean differences, which are needed for the calculation of least significant differences (or other mean separation procedures), have not been available in either the agronomic or statistical literature. The main purpose of this paper is to provide the formulae for estimation of these variances so that researchers can use them in testing the significance of differences among various treatment means averaged over environments. Emphasis is given to combined analyses of series of experiments in which the effects of experiments are considered to be random; individual experiments are assumed to have complete factorial treatment designs involving either two or three factors of which at least one is qualitative. All treatment effects, including main effects and interactions, are considered to be fixed effects. Formulae applicable to commonly used experimental designs are presented for the estimation of variances for the five categories of pairprise mean differences in two‐factor treatment designs and the 19 categories of pairwise mean differences in three‐factor treatment designs. Experimental design considerations and the implications of assuming random (versus fixed) experiment effects as well as the structure of the treatment × experiment interactions are studied. Pooling portions of the treatment × experiment interaction with error mean squares are considered, and suggestions are given for cases where some of the treatment factors are quantitative rather than qualitative.
Soybean Cultivar Response to Reduced Tillage Systems in Northern Dryland Areas
Authors: Deibert E. J.
Published: July 2010

Information on response of soybean [Glycine max (L.) Merr.] cultivars to reduced tillage systems in northern dryland areas is limited. A 4‐yr field study (1984 to 1987) was conducted to evaluate the effect of tillage system, weed control method, and cultivar maturity on soybean seed yield variables. An early and a late‐maturing soybean cultivar were grown on a Fargo clay (fine, montmorillonitic frigid Vertic Haplaquoll) on established tillage plots. Tillage systems included conventional (moldboard plow) and three reduced tillage systems (sweep, intertill, and no‐till) with herbicides or herbicides plus cultivation for weed control. Climatic conditions resulted in differences among years in seed yield, seed weight, seed moisture, seed oil concentration, and seed oil yield. These seed variables were not significantly influenced by tillage system, weed control method, or cultivar maturity when grown in rotation with barley (Hordeum vulgare L.), but showed significant interactions. Cultivation for weed control depressed seed yield and weight of only the early cultivar. Early plant water stress (June and July) lowered yield of the early cultivar more than the late cultivar. Early cultivar no‐till yields (1240 kg ha−1) were greater than tilled system yields (average 1070 kg ha−1), while late cultivar yields were similar among systems (average 1420 kg ha−1). An early maturing cultivar performed similarly to a late‐maturing cultivar irrespective of tillage system unless early plant water stress was encountered. Fall application of granular herbicide provided good weed control, but cultivation for weed control was not beneficial for the yields parameters measured.
Rice Response to Waterlog‐Tolerant Green Manures
Authors: Morris R. A. , Furoc R. R. , Rajbhandari N. K. , Marqueses E. P. , Dizon M. A.
Published: July 2010

Chemical N fertilizers are usually applied to modern rice (Oryza sativa L.) cultivars, but yield responses are obtained from green manuring as well. To be considered as a viable alternative to chemical N fertilizer in tropical Asia, however, green manures must tolerate the ephemeral waterlogging that precedes rice cultivation. Experiments on an Aeric Tropaqualf soil during three early wet seasons determined green manure N accumulation in 60 d or less, and rice grain yield response to it. In the first experiment (1983), cowpea [Vigna unguiculata (L.) Walp.] and Sesbania cannabina [(Retz.) Poir.] were grown 24, 36, and 48 d before incorporation. Nitrogen accumulation was greatest (79 kg N ha−1) in 48‐d S. cannabina. Accumulation in cowpea was apparently depressed by waterlogging. Rice grain yield response to green manure N was unaffected by location of green manure cultivation (in situ vs. transported from a nearby field). In the second (1984) and third (1985) experiments, Sesbania sp. were flooded during the last 25 d of growth to assure early wet–season waterlogging. Mean N accumulation in flooded S. rostrata (Brem. and Obrem.), which nodulates on its stem, was 90 kg ha−1 in 48 d and 164 kg ha−1 in 60 d. Nitrogen accumulations in nonflooded S. rostrata were 128 kg ha−1 in 48 d and 198 kg ha−1 in 60 d. Accumulation in a Nepalese S. cannabina cultivar averaged 84% of that in S. rostrutu. Rice grain yield response was a function of green manure N regardless of species or age. Both S. rostrata and S. cannabina tolerate waterlogging and accumulate sufficient N in less than 60 d to increase rice yields more than 2 Mg ha−1.
No‐Till Winter Wheat Production on the Canadian Prairies: Timing of Nitrogen Fertilization
Authors: Fowler D. B. , Brydon J.
Published: July 2010

The introduction of a practical snow management system, which uses direct no‐till seeding into standing stubble immediately after harvest of the previous crop, has permitted northward expansion of the North American winter wheat (Triticum aestivum L.) production area to include most of the western Canadian prairies. Twenty‐one broadcast ammonium nitrate fertilizer field trials were conducted in Saskatchewan from 1976 to 1986 to determine what influence timing of N fertilizer application had on grain yield, grain protein yield, and grain protein concentration of no‐till winter wheat. Time of N application had a significant influence on all three variables in approximately one‐third of the trials. Lower grain yield, grain protein yield, and grain protein concentration were attributed to loss of fallapplied N in four trials. In one trial, a prolonged period without rainfall left N temporarily stranded in a dry surface soil layer and lowered yield for early spring fertilizer application. Delays in spring N application also limited grain and grain protein yield‐N responses. However, dry spring conditions and late fertilizer applications did not limit grain protein yield to the same extent as it did grain yield. Therefore, increased grain protein concentration was often associated with delayed N availability. Reduced grain and grain protein yield, and increased grain protein concentration were observed for fall and early spring N applications in trials that experienced favorable spring growing conditions followed by a prolonged drought. Under these conditions maximum grain protein concentration ranged from 170 to 230 g kg−1, compared with approximately 150 g protein kg−1 dry grain under normal growing conditions.
Seasonal Variation in Chemical Composition of Forage Brassicas. II. Mineral Imbalances and Antiquality Constituents
Authors: Guillard K. , Allinson D. W.
Published: July 2010

Although the nutritional value of Brassica crops is apparently high, antiquality constituents and elevated concentrations of certain minerals in herbage may negatively affect animal performance. This paper reports on seasonal variation of Ca/P, K/(Ca + Mg), and (K + Ca)/Mg ratios, and concentrations of thiocyanate (SCN−) and nitrate (NO−3‐N) in various Brassica crops. Turnip (B. rapa L.), rape (B. napus L.), swede (B. napus L.), and Tyfon [B. rapa L. × B. pekinensis (Lour.) Rupr.) were no‐till seeded in Connecticut on a Paxton fine sandy loam soil (coarse‐loamy, mixed, mesic Typic Dystrochrept) in summer and autumn of 1983 and 1984. Kale (B. oleracea L. var. acephala DC.) and the species listed above were seeded in the summer of 1987 and autumn of 1986 and 1987, to determlne NO−3‐N partitioning. Foliage Ca/P ratios were above 1:1 to 2:1, whereas root ratios were close to or slightly below this range. Ratios of Ca/P were significantly greater in summer than in autumn. The (K + Ca)/Mg ratio in 1983 exceeded the maximum desirable limit of 5.2 in autumn foliage and roots. Only turnip root ratios exceeded 5.2 in 1984. Concentrations of SCN− ranged from 160 to 840 mg kg−1 in foliage and from 274 to 845 mg kg−1 in roots. Foliage concentrations of NO−3‐N ranged from 21 to 1011 mg kg−1 in summer and from 2293 to 4750 mg kg−1 in autumn. Concentrations of NO−3‐N were lower in roots and showed the same seasonal pattern as foliage. Accumulation of NO−3‐N was highest in stems and petioles, lowest in leaf laminae, and intermediate in roots. Nitrate toxicity risk may be greater for ruminants grazed on autumn‐grown Brassica than those grazed on summer‐grown Brassica. Supplementation of P and iodine, controlled intake of Brassica crops, or addition of roughages should reduce concerns about mineral imbalances or antigrowth constituents associated with these forages.
Growth Response of Cultivars to Conservation Tillage in a Continuous Wheat Cropping System
Authors: Dao Thanh. H. , Nguyen H. T.
Published: July 2010

Changes in tillage methods to cope with the continual erosion of our soil resource prompted the need to reassess current management practices for annual cropping systems of wheat (Triticum aestivum L.). A field study was conducted on Bethany silt loam (fine, mixed, thermic Pachic Paleustoll) from 1983 through 1987 near El Reno, OK to determine whether 10 hard red winter wheat cultivars respond differently to tillage systems. The cultivars were planted in moldboard‐plowed seedbeds, stubble‐mulch‐tilled seedbeds, or directly in standing stubble (no‐tillage). The effects of tillage method on plant stand, phenology, grain yield, and yield components were determined. Tillage method ✕ cultivar interactions varied with agronomic traits and years. In general, reducing tillage intensity delayed plant maturation beginning in the spring. Anthesis and leaf‐area duration periods occurred about 1 to 8 d later in mulch‐tilled and no‐tilled plots, compared with plowed plots. The prolonged vegetative phase indicated a potential benefit of no‐tillage in a wheat‐production system that includes a livestock grazing component during the winter months. Grain‐fill periods of no‐tillage wheat increased between 1 to 4 d in early‐maturity cultivars while those of later‐maturity cultivars were variable. The lack of tillage method ✕ cultivar interaction for grain yield indicated that development of wheat cultivars for emerging conservation technology may not be necessary. Notillage wheat yields were similar to conventional‐tillage yields, or slightly better in years with cold autumns that had erosive rains or dry springs. Early maturity cultivars consistently had stable yields during 1983 to 1987 with good resilience against environmental variations, but late‐maturity ones may not be suitable for no‐tillage winter wheat production. High temperature tolerance may be a potential breeding objective for plant types adapted to conservation tillage in the Southern Plains.
Plant Density and Defoliation Effects on the Recovery of Soybean Injured by Stem Cutoff During Vegetative Development
Authors: Hintz R. W. , Fehr W. R.
Published: July 2010

The current procedure for assessing the yield loss of soybean (Glycine max (L.) Merr.] caused by defoliation and stem cutoff does not take into account plant density. This study was conducted to determine the effects of plant density on the recovery of soybean injured by defoliation and stem cutoff during vegetative development. Plots were established during 2 yr at plant densities of 119 600, 191 300, 239 200, 310 900, and 382 700 plants ha−1. Treatments imposed on each of the five densities at stages V3 and V6 consisted of a factorial arrangement of 33 and 66% removal of the main stem with 0 and 100% defoliation. The stage of development at which treatments were imposed and the plant density of treated plots had no significant effect on percentage yield reduction. The results indicated that plant density is not an important factor when assessing yield loss of soybean from plant injury during vegetative development.
Predicting the Effect of Ammonium Placement on Nitrogen Uptake by Corn
Authors: Anghinoni L. , Barber S. A.
Published: July 2010

A mechanistic model has successfully described the effect of P placement on P uptake by corn (Zea mays L.) and soybean (Glycine max L.). Model predictions for N have not been evaluated experimentally. The objective of this paper is to compare the effect of NH+4 placement on N uptake by corn found experimentally with that calculated with the mechanistic uptake model mentioned above. Observed N uptake values were obtained by growing corn in a growthchamber experiment using a sample of the 0 to 20 cm layer of Raub silt loam (fine‐silty, mixed, mesic Aquic Argiudolls) soil. Ammonium as (NH4)2SO4 was applied at a rate of 270 mg N per 3 kg soil to all or part of the soil in each pot. Fractional volumes fertilized were 1.00, 0.50, 0.20, 0.10, 0.05 and 0.02. Nitrapyrin [2‐chlorod‐6‐(trichloromethyl) pyridine] at 8 mg kg−1 was added to the soil to minimize nitrification of NH+4. Contribution to N uptake of each of the fertilized and nonfertilized fractions of soil were calculated with the mechanistic model from data for ion uptake kinetics, root distribution and morphology, and the soil parameters, soil solution NH+4 concentration, buffer power, and effective diffusion coefficient, used in the model. Predicted values were close to observed values when N fertilizer was mixed with all the soil. Calculated values became progressively smaller than observed values as the NH+4‐treated fraction of the soil decreased. When increases in the size of the NH+4‐treated soil volume due to NH+4 diffusion out of the initially treated volume and increases in the maximum N uptake rate per unit of root due to a reduction in the proportion of roots absorbing N were considered in the model, most predicted values approximated observed N uptake values.
Comparison of Three Herbicides For Selective Tall Fescue Control in Kentucky Bluegrass
Authors: Dernoeden Peter H.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) can be an objectionable weed in Kentucky bluegrass (Poa pratensis L.). Field studies were conducted to determine safe and effective rates of chlorsulfuron [2‐chloro‐N‐{[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl)amino]carbonyl}‐benzenesulfonamide], diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy)phenoxy]propanoic acid), and metsulfuron [2‐([{[(4‐methoxy‐ 6‐methyl‐l,3,5‐triazin‐2‐yl}amino]carbonyl}amino]sulfonyl)benzoic acid] for selective tall fescue control in Kentucky bluegrass. Herbicides were field tested in either ‘Kenblue’ Kentucky bluegrass, grown on a Sassafrass sandy loam (fine‐loamy, siliceous, mesic Typic Hapludult), or an improved Kentucky bluegrass blend grown on a Chester silt loam (fine‐loamy, mixed mesic Typic Hapludult). Two applications of diclofo p reduced bluegrass cover and quality for extensive periods and generally provided inferior tall fescue control compared to chlorsulfuron or metsulfuron. Chlorsulfuron applied at 0.07 + 0.07 or 0.14 + 0.14 kg ha−1 did not reduce bluegrass cover at either site. Single applications of metsulfuron (0.07 or 0.14 kg ha−1) did not injure Kenblue; however, both rates injured the Kentucky bluegrass blend, and turf treated twice at the high rate required 1 yr for recovery. Single applications of chlorsulfuron (0.14 or 0.28 kg ha−1) or metsulfuron (0.07 or 0.14 kg ha−1) provided over 90% tall fescue control at the Kenblue site. Split applications of 0.07 + 0.07 or 0.14 + 0.14 kg ha−1 of either chlorsulfuron or metsulfuron provided over 90% control in the bluegrass blend. When compared to untreated turf, chlorsulfuron or split applications of metsulfuron applied in the fall, resulted in more bluegrass injury the following summer when turf was subjected to drought stress.
Spring Wheat Response to Enhanced Ammonium Supply: II. Tillering
Authors: Camberato J. J. , Bock B. R.
Published: July 2010

Spring wheat (Triticum aestivum L.) grain dry matter (DM) is increased by increasing the proportion of fertilizer N as NH4 in the presence of a nitrification inhibitor (enhanced ammonium supply, EAS). This yield increase is manifest in increased heads plant−1. The objective of this study was to determine the effects of EAS on the number and origin of vegetative and headed tillers and on the number of fertile spikelets and kernels of each tiller. Knowledge of these effects will aid in determining when and how EAS increases grain DM. Increased grain DM with EAS in this study resulted from an increase in the number of headed tillers plant−1, which, for the most part, resulted from an increase in the number of vegetative tillers plant−1. Increases in vegetative tillers plant−1 were detectable within several days after the onset of tillering and were similar for a low‐tillering and a high‐tillering cultivar. The rate of mainstem development was not affected by EAS, but several tillers appeared earlier with EAS. For some tillers, EAS also increased the proportion of vegetative tillers forming heads. Increased grain DM was not proportional to increases in heads plant−1, because the additional headed tillers produced with EAS treatments were primarily T0 (coleoptilar mainstem) tillers and subtillers that had fewer spikelets head−1 and kernels head−1. The number of fertile spikelets head−1 of several tillers was increased by EAS treatments, but the number of kernels head−1 was increased for the T1 and T20 tillers, only. Negative effects of EAS treatments on late‐appearing tillers (T4, T5, and T22) were thought to result from increased self‐shading, increased plant wilting, and reduced soil‐N supply occurring at anthesis and resulting from the much greater plant DM prior to anthesis in EAS treatments. However, in general, increased spring wheat grain DM with EAS can be ascribed to the positive effects of EAS on tiller development.
Area Harvests Equivalency Ratio for Measuring Efficiency in Multiseason Intercropping
Authors: Balasubramanian V. , Sekayange L.
Published: July 2010

Both area and time factors have to be considered to quantify resource‐use efficiency in multiseason intercropping. The land equivalent ratio (LER), commonly used as an indicator of efficiency, is not suitable because it considers only the area factor to estimate intercrop advantages. The area time equivalency ratio (ATER) unrealistically assumes continuous crop growth throughout the year, thus it underestimates the advantages of intercrops. To avoid these problems, some authors used the mean value of LER + ATER as an arbitrary compromise. This paper proposes a new concept called area harvests equivalency ratio (AHER). This ratio incorporates the time factor in the form of number of possible harvests of each component crop in a system that could be obtained during the full intercrop period, if each component was monocropped. Four cases of intercrops were used to compare the above concepts. The AHER has proved to be a better efficiency indicator than others, except when a component species occupies the land for one season plus a fraction of the succeeding season (l.5, 2.5 seasons). In this particular case, other concepts are also disappointing. The problem with any attempt to quantify resource‐use efficiency is that there is no “true value” for yield advantages in intercrops. However, intuitively, AHER does seem to be nearer to the “true value” than others.
Long‐Term Wheat, Soybean, and Grain Sorghum Double‐Cropping under Rainfed Conditions
Authors: Crabtree R. J. , Prater J. D. , Mbolda P.
Published: July 2010

Inadequate amounts and distribution of rainfall are most often the major limiting factors to crop production in the southern Great Plains. This is especially true for summer crops, whether grown in mono‐ or double‐cropping situations. This study was conducted at the Oklahoma Vegetable Research Station, Bixby, OK from 1976 to 1987 on a Wynona silt loam soil (Cumulic Haplaquolls) with 0 to 1% slope. The objective was to determine the effects of long‐term double‐cropping on the potential for sustaining grain yields of wheat [Triticum aestivum (L.) em. Thell], soybean [Glycine max (L.) Merr.], and grain sorghum (Sorghum bicolor L. Moench) produced on the same land under rainfed conditions. Over a 12‐yr period monocropped wheat averaged 3050 compared with 2510 and 2450 kg ha−1 when double‐cropped with soybean and grain sorghum, respectively. Conventionally tilled monocropped soybean and grain sorghum and no‐till double‐cropping of both soybean and grain sorghum after wheat produced grain 11 out of 12 yr. Monocropped soybean averaged 2470 compared with 1930 kg ha−1 for no‐till double‐cropped soybean. Monocropped grain sorghum averaged 5130 compared with 4200 kg ha−1 for double‐cropped grain sorghum. During the years of near 30‐yr average rainfall amounts and distribution (5 out of 11), yields of double‐cropped soybean and grain sorghum were competitive with those of monocropped soybean and grain sorghum. These results indicate that yields of double‐cropped wheat, soybean, and grain sorghum can be sustained over long periods of time. In eastern Oklahoma double‐cropping on a deep medium textured soil produced more total grain that resulted in more efficient use of climatic, land, labor, and equipment resources when compared with monocropping.
Yield Dynamics of Canopy Components in Alfalfa‐Grass Mixtures
Authors: Mooso G. D. , Wedin W. F.
Published: July 2010

Relationships between alfalfa (Medicago sativa L.) and associated grasses in a plant community are complex. A concern has developed whether alfalfa was, in fact, benefiting from grass association. A field study was conducted to describe the changes in canopy components of alfalfa‐reed canarygrass (Phalaris arundinacea L.) and alfalfa‐orchardgrass (Dactylis glomerata L.) mixtures. Alfalfa‐grass mixtures of one row of grass between two rows of alfalfa and one row of alfalfa between two rows of grass were planted in a repeating pattern. Monocultures of each species and four binary mixtures were sampled for total, alfalfa and grass component, and stratified alfalfa yields were measured at 10, 20, 30, 40, and 50 d of spring and summer regrowth for 2 yr. Planting pattern, grass species and season of growth affected botanical composition and yield of alfalfa‐grass mixtures. Alfalfa‐grass mixtures yielded more than alfalfa monocultures during only one spring growth cycle. During summer regrowth, alfalfa‐grass mixtures were less productive than alfalfa monocultures. In spring, reed canarygrass accounted for a greater proportion of the total yield than orchardgrass, whereas the two grasses were similar during summer. Grass yields of mixtures were not affected by alfalfa association. The results of this study suggest that alfalfa‐grass mixtures offer little yield advantage over alfalfa monocultures when harvested as hay.
Canopy Temperature and Stomatal Conductance of Water‐stressed Dormant and Nondormant Alfalfa Types
Authors: Hattendorf M. J. , Evans D. W. , Peaden R. N.
Published: July 2010

Alfalfa (Medicago sativa L.) from diverse origins may respond differently to water stress. Objectives were to assess dormant and nondormant‐type alfalfa response to water stress as inferred from canopy temperature and stomatal conductance. The effects of continuous deficit irrigation produced by a line‐source sprinkler system on ‘Vernal’ (dormant type), ‘Vernema’ (intermediate dormancy type), and ‘CUF 101’ (nondormant type) were investigated at Prosser, WA, on a Warden loam (coarse‐silty, mixed, mesic Xerollic Camborthids). Water stress was expressed as the Crop Water Stress Index (CWSI), a canopy‐temperature (Tc) based indicator of water stress. The Y‐intercepts of Vernal and CUF 101 canopy‐air temperature/vapor pressure deficit (Tc–TaVPD) curves were significantly different (P = 0.05) with CUF 101 0.6 °C (28.5%) higher than Vernal. Mean canopy resistance to vapor transport (rcp) was 33% greater for CUF 101 than for Vernal. Slopes of stomatal conductance/CWSI curves were similar, but stomatal conductance at zero CWSI of CUF 101 was 60% of Vernal. Total water use and yields of Vernal, Vernema, and CUF 101 were not significantly different (P = 0.05) among cultivars, although CUF 101 mean daily water use was 2.1 mm greater than Vernal water use early in the growth cycle. Higher Tc for CUF 101 was consistent with lower CUF 101 stomatal conductance. The differences in Tc and stomatal conductance were related to dormancy type. Lower transpiration of CUF 101 at full canopy cover has implications for development of more water‐use efficient alfalfa.
Irrigation of Turfgrass with Secondary Sewage Effluent: II. Turf Quality
Authors: Hayes A. R. , Mancino C. F. , Forden W. Y. , Kopec D. M. , Pepper I. L.
Published: July 2010

Due to limited water resources, golf course irrigation with municipal sewage effluent is a common practice, and, in some areas of the USA Desert Southwest mandatory. However, effluent irrigation changes soil properties and therefore different management practices are needed for good quality turfgrass. This field experiment evaluated the continuous use of secondary treated municipal sewage effluent on turfgrass quality over a 64‐wk period. In April 1987, common bermudagrass (Cynodon dactylon L. Pers.) was seeded to a Sonoita gravelly sandy loam (coarse‐loamy, mixed, thermic Typic Haplargid) and maintained under fairway conditions. In October of that year, perennial ryegrass (Lolium perenne L.) was overseeded to maintain an actively growing turf. Plots were irrigated identically with either effluent or potable water. Effluent irrigation led to significantly lower seed emergence but improved seed establishment. Turf quality was assessed under each irrigation with four N fertilization rates of 0, 16.1, 32.3 and 48.4 kg N ha−1 (4 wk)−1. Established effluent irrigated turf did not show signs of osmotic stress with the leaching fraction employed. Effluent provided significant amounts of nutrients at high application rates. No single fertilization rate or irrigation regime consistently produced a superior turf quality over the course of the whole study. Effluent irrigated turf showed signs of overfertilization, greater heat stress and chlorosis of overseeded ryegrass stands during the summer months on plots receiving N fertilizer amendments. Municipal effluent did produce a high quality turf, but, the greater soluble salt and nutrient content of the water necessitate special management strategies.
Soybean Growth and Yield as Affected by Surface and Suboil Compaction
Authors: Johnson J. F. , Voorhees W. B. , Nelson W. W. , Randall G. W.
Published: July 2010

Axle loads from wheel traffic on farmland ranges from less than 4.5 Mg axle−1 to over 20 Mg axle−1. Loads of <4.5 Mg axle−1 generally cause compaction only in the upper 0.3 m of the soil (surface compaction), while higher loads have caused soil compaction below this surface layer (subsoil compaction). A replicated field study was conducted on a Webster clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll) in southern Minnesota and on two Ves clay loams (fine‐loamy, mixed, mesic Udic Haplustoll) in southwestern Minnesota to assess the effect of surface and subsoil compaction on the growth and yield of soybean (Glycine max L. Merr.). Surface compaction treatments consisted of no interrow traffic on either side of the row at any time during the experiment and annually applied interrow wheel traffic on both sides of the row from an axle load <4.5 Mg. Subsoil compaction treatments consisted of control (no subsoil compaction), 9 and 18 Mg axle−1 loads applied once at the beginning of the experiment. Surface compaction, when averaged over years on both Ves sites, decreased yield by 15% overall and up to 27% in a single year. Yield response to surface compaction on the Webster site was climate dependent, in general, decreasing yield during a wet year but increasing yield during a dry year. Subsoil compaction from the 18 Mg axle−1 treatment reduced plant height and integrated leaf area index on the Webster site each year of the experiment, and tended to decrease yield. The response to the 18 Mg axle−1 load on the Ves was inconsistent. Yield was increased significantly in 5 out of 14 location‐years by the 9 Mg axle−1 treatment when compared with the control treatment. Soybean growth parameters and yield were affected more by annual surface compaction than by a one‐time application of subsoil compaction. A decrease in vegetative growth did not necessarily result in a comparable decrease in seed yield.
Increasing Soybean Productivity through Selection for Nitrogen Fixation
Authors: Burias N. , Planchon C.
Published: July 2010

Nitrogen fixation and accumulation are major factors of soybean [Glycine max (L.) Merr.] production. Investigations were carried out to determine whether higher N2 fixation could be considered as a criterion for the improvement of productivity. A selection for N2 fixation, which was based on acetylene reduction estimates, was carried out at Growth Stage R5. A set of 210 F2 plants issued from three crosses and developed in nutrient solutions was studied in phytotronic chambers, under temperature and mineral N nutrition conditions that were favorable for the maximum expression of the symbiosis. The seed yield of the F4‐derived lines was evaluated under normal population density on a Typic Udifluvent loamy‐sand soil (pH 6.0, organic matter 1.5%, and total N 1 g kg−1). Seed yield and N2 fixation were expressed with respect to the mean value of the genotypes with the same date of maturity. Seed yields of the F4‐ derived lines were significantly correlated with the N2 fixation of the F2 parent plants. This correlation was observed for all of the plants investigated including all crosses (r = 0.294**, significant at P = 0.01) and for each of the three crosses: Weber × Maple Arrow (r = 0.433**), Weber × Jiling 14 (r = 0.394*, significant at P = 0.05), Weber × Kingsoy (r = 0.597**). The seed yield of the F4 lines was also significantly correlated with nodule volume and nodule dry weight, particularly at each cross level. High nodulation ability and high N2 fixation rates appear to increase soybean seed yield. Early breeding for these traits may therefore be expected to result in a genetic gain in seed yield in the progeny.
Nitrogen Fertilization of Wheat Double‐Cropped Following Grain Sorghum in a No‐Tillage System
Authors: Howard Donald D. , Lessman Gary
Published: July 2010

Utilization of wheat (Triticum aestivum L. em Thell.) as a cash crop or cover crop in a double‐cropping system is desirable to prevent excessive soil erosion on loess‐derived soils in the southern USA. Fall and spring N application to winter wheat double‐cropped following grain sorghum (Sorghum bicolor L.) was evaluated on a Grenada silt loam (fine‐silty, mixed, thermic Glossic Fragiudalf). The experimental design was a randomized complete block with a split‐plot arrangement of treatments. Rates of N applied at planting; (0, 34, and 67 kg ha−1) were the main plots, with N rates applied in the spring (0, 34, 67, 101 and 134 kg ha−1) the sub‐plots. Fall N (Nf) increased both yield and plant height. Spring N (Ns) had a. greater effect on yield and plant height than Nf. Yields increased from 0.83 to 2.61 Mg ha−1) by increasing Ns from 0 to 134 kg ha−1) without Ns. Yields increased from 1.50 to 2.67 Mg ha−1) by increasing Na from 0 to 67 kg ha−1 with 67 kg ha −1>/ Nf. Yield variation was expressed by Y = 0.822 + 0.0098 Nf + 0.0248 Ns − 8.5 × 10−5) N2s + 1.45 × 10−5 NfNs − 7.41 × 10−7 NfN2s. Plant height increased from 56 to 85 cm by increasing Ns from 0 to 134 kg ha−1 without Nf, but increased from 67 to 80 cm by increasing Ns from 0 to 67 kg ha−1 with 67 kg ha−1 Nf One‐hundred‐kernel weight decreased from 2.35 to 2.11 g by increasing Ns from 34 to 134 kg ha‐1. Grain N increased from 19.9 to 23.2 g kg‐1 by increasing Ns from 34 to 134 kg ha−1.
Temperature Effect on Growth and Development of Cotton During the Fruiting Period
Authors: Reddy V. R. , Reddy K. R. , Baker D. N.
Published: July 2010

Cotton (Gossypium hirsutum L.) requires warm days and relatively warm nights for optimum growth and development. However, in many areas of the cotton belt, sub‐ and super‐optimal temperatures frequently occur, both early and late in the season, resulting in altered growth and development. The purpose of this research was to quantify plant responses to temperature, so that these responses could be incorporated into plant growth models used to manage cotton crops. Plants, initially grown out of doors in pots, were moved into sunlit, temperature‐controlled growth chambers 5 d prior to initial bloom. Growth and development were studied in 20/10,25/ 15,30/20,35/25, and 40/30 °C day/night temperature regimes from initial bloom. Temperature significantly affected phenology, leaf expansion, internode elongation, biomass production and the partitioning of assimilates to different plant parts. Optimum temperature for biomass production was 30/20 °C, with 40 and 50% less biomass at 20/10 and 40/30 °C, respectively. By 49 d after initial bloom, 13, 15 and 43% of the biomass had been partitioned to bolls and squares at 20/10,25/15 and 30/20 °C, respectively, reflecting to some extent slower development at the temperatures lower than 30/20 °C. Above 30/20 °C, most of the squares and bolls were aborted. The growth of the main‐stem and its successive leaves at 30/20 °C was rapid initially, but was restricted later due to competition with bolls for available carbohydrates. The quantification of growth and developmental rates over a wider range of temperatures will enable us to predict crop performance if temperature increases as a result of global climate change.
No‐Till Warm‐Season Grass Establishment as Affected by Atrazine and Carbofuran
Authors: McKenna J. R. , Wolf D. D. , Lentner M.
Published: July 2010

Tall growing, perennial, warm‐season grasses that produce 65 to 75% of their yield in mid‐summer may provide needed summer grazing; however, establishment is often slow and inconsistent when compared to cool‐season grasses. Improved establishment would make these warm‐season grasses less vulnerable to annual weed competition. No‐till plantings of switchgrass (Panicum virgatum L.) and Caucasian bluestem (Bothriochloa caucasica (Trin.) C. E. Hubbard] were made at Blacksburg, VA (37° 11' N° 80° 25' W, 610‐m elevation) on a Groseclose loam soil (clayey, mixed, mesic Typic Hapludult). Eight experiments included carbofuran (2,3‐Dihydro‐ 2,2‐dimethyl‐7‐benzofuranol methylcarbamate) at 0 and 1.1 kg a.i. ha−1 and atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) at 0, 1.1, and 2.2 kg a.i. ha−1 in all possible combinations. Seedling growth, leaf appearance rates, seedling weights, density, leaf elongation rates, and heights were measured. Yields of weedfree perennial warm‐season grasses were determined in the year of planting and the year after planting. Carbofuran at 1.1 kg a.i. ha−1 placed in the row with the seed at planting enabled seedlings to develop faster, elongate more rapidly, and provided more and heavier seedlings than without carbofuran. In the year after seeding, yields of warm season grass were higher where carbofuran was applied at seeding in seven of eight experiments. Atrazine reduced herbage yields as well as population, weight, development, and leaf elongation rate of seedlings in the seeding year. Atrazine at 1.1 kg a.i. ha−1 was not detrimental to either grass in the second year of the study. Atrazine at 2.2 kg a.i. ha−1 appeared to injure switchgrass more than Caucasian bluestem. Yields in the year after planting further confirmed these observations. Atrazine at 1.1 kg a.i. ha−1 increased yields over untreated controls. However, in one of four switchgrass experiments, yields of grass treated with atrazine at 2.2 kg ai. ha−1 were lower than controls the year after planting. A yield reduction was observed in two of four caucasian bluestem experiments. All stands were nearly pure with planted species the year after planting. Carbofuran and atrazine at 1.1 kg a.i. ha1 was considered the best recommendation for establishment of switchgrass and Caucasian bluestem under the conditions of the experiment.
Water Status Effect on Dinitrogen Fixation and Photosynthesis in Soybean
Authors: Djekoun A. , Planchon C.
Published: July 2010

Water deficiency brings about a marked limitation in soybean (Glycine max. L. Merr.) yield by impairing photosynthesis and symbiotic N2 fixation. The objective of this study was to determine the photosynthetic and N2‐fixation response to short‐ and long‐duration water status variations in leaves and nodules. Plants were grown in pots in a greenhouse. Carbon dioxide exchange rate was measured by gas analysis and N2 fixation by the acetylene reduction method. Leaf water status was determined with a pressure bomb and nodule water potential with a psychrometer. Dinitrogen fixation decreased steadily throughout the water deficiency period whereas photosynthesis first decreased only slightly, and then dropped dramatically. After a severe water stress, partial recovery was slower for N2 fixation than for photosynthesis. The N2‐fixation response appeared to be directly related to a reduction in nodule mass, which affected nodule structural constituents after a severe stress. During the water deficiency period, the water status of the nodules responded only partially to water status variations within the plant during the day. Dinitrogen fixation depended more on the water status of the nodules than on the changes in nodule mass. There was a higher dependence of N2 fixation on nodule water content than on nodule water potential, particularly for values <‐1.2 MPa. The N2‐fixation activity maintained during the severe phase of water stress, when photosynthesis was zero, resulted from the relative independence of the nodules on the daily water variations within the plant and from the strong binding of the nodule water.
Separation of Mesophyll from Non‐Mesophyll Cell Wall Tissue in Indiangrass Leaf Blades
Authors: Piwonka Edward J. , MacAdam Jennifer W. , Kerley Monty S. , Paterson John A.
Published: July 2010

A method to isolate large quantities of non‐mesophyll cell wall material for studying factors that limit the susceptibility of these cell wall polysaccharides to microbial degradation was evaluated. Mesophyll cells were separated from non‐mesophyll cells in indiangrass (Sorghastrum nutans [L.] Nash) leaf blades by ball milling to separate cells and then sieving to isolate non‐mesophyll cells. The mesophyll fraction was comprised of non‐lignified mesophyll cells contaminated with some fiber (sclerenchyma, xylem, and bundle sheath) particles. The non‐mesophyll fraction was virtually free of mesophyll cells and consisted primarily of lignified cell wall material. The weight ratio of mesophyll to non‐mesophyll cell wall material was 1.2:1. Non‐mesophyll cell walls were similar to mesophyll cell walls in their concentrations of arabinose, mannose, and galactose, and higher in their concentrations of xylose, glucose, p‐coumark acid, and ferulic acid. The ratio of xylose to arabinose was significantly greater for the non‐mesophyll fraction. Compositional differences between non‐mesophyll and mesophyll cell walls may in part explain the lower susceptibility of non‐mesophyll cell wall material to microbial degradation compared to mesophyll cell wall material.
Growth Rate and Water Use by Legume Species at Three Soil Temperatures
Authors: Zachariassen J. A. , Power J. F.
Published: July 2010

Legumes may be used to reduce fertilizer inputs, provide ground cover for soil erosion protection, and reduce residual soil nitrates. Little data are available to guide a producer in selecting a legume that matches water and temperature conditions and produces acceptable growth and N2‐fixation rates. The purpose of the experiment reported here was to provide such information. After a 14‐d germination period at 20 °C, we grew eight legume species at soil temperatures of 10, 20, and 30 °C (± 2 °) for 105 d in a greenhouse. Daily water use was recorded, and plant dry weights were measured every 21 d. Initially annual species such as soybean [Glycine max (L.) Merr.] and fababean (Vicia faba L.) grew fastest at all temperatures. For the first 42 d at 10 °C, white clover (Trifolium repens L.), crimson clover (Trifolium incarnatum L.), and hairy vetch (Vicia villosa L.) also exhibited rapid growth. With warmer temperatures and longer growth periods, lespedeza (Lespedeza stipula L.) as well as soybean grew rapidly. At 20 and 30 °C, soybean growth was often more than double that of most other species. Growth was maximal at 10 °C for fieldpea (Pisum arvense L.), hairy vetch, and crimson clover; at 20 °C for fababean and white clover; and at 30 °C for soybean, sweetclover (Melilotus alba L.), and lespedeza. Average water‐use rates and water‐use efficiency generally paralleled growth, except water use increased and water‐use efficiency decreased as soil temperature increased. These results indicate that growth and water use differed greatly among legume species, that each legume species has its own characteristic optimum growth temperature, and that this optimum temperature for a given species may change as growth progresses.
HERB: Decision Model for Postemergence Weed Control in Soybean
Authors: Wilkerson G. G. , Modena S. A. , Coble H. D.
Published: July 2010

To efficiently use postemergence herbicides, decision makers must determine when weed populations exceed economic treatment thresholds. An interactive microcomputer program named HERB has been developed to help evaluate potential crop damage from multi‐species weed complexes in soybean [Glycine max (L.) Merr.] and determine the appropriate course of action. Seventy‐six weed species were rated on a scale of zero to 10 according to their competitiveness with soybean. Potential yield loss is estimated from these rankings, the number of weeds of each species present in the field, and expected weed‐free yield. The recommendation whether to apply a herbicide and, if so, which one, is based on herbicide cost and efficacies under different conditions and expected soybean selling price. Alternative herbicide choices are ranked according to expected net return. HERB is intended to provide the latest research information in an organized and easily usable format. The approach should be applicable to other crops and pests.
Forage Yield and Nutritive Value of Elephantgrass as Affected by Harvest Frequency and Genotype
Authors: Woodard K. R. , Prine G. M.
Published: July 2010

Elephantgrass (Pennisetum purpureum Schum.) is known throughout much of the wet tropics for its prolific growth and usage as a forage for ruminants. In a 3‐yr study conducted on a welldrained, infertile soil (loamy, siliceous, hyperthermic, Grossarenic Paleudult) and under subtropical conditions near Gainesville, FL, the response of this forage to three harvest frequency regimes was measured. Genotypes evaluated were four tall elephantgrasses (PI 300086, ‘Merkeron’, N‐43, and N‐51), a dwarf elephantgrass (Mott), and a semi‐dwarf Pennisetum glaucum (L.) R. Br. × P. purpureum Schum. hybrid (Selection 3). Forage dry matter (DM) yields for Merkeron, N‐43, and N‐51 did not differ. For these three genotypes, 3‐yr mean DM yields (1986‐1988) were 24.3, 21.1, and 17.0 Mg ha−1 yr−1 for one, two, and three harvests per year, respectively. Two‐year mean (1986‐1987) crude protein (CP) concentrations for all four tall genotypes were 40.3, 57.5, and 75.7 g kg−1 DM while in vitro digestible organic matter (IVDOM) concentrations were 399, 492, and 555 g kg−1 organic matter (OM) for one, two, and three harvests per year, respectively. For Mott, 3‐yr mean DM yields were 11.8, 11.8, and 11.7 Mg ha−1 yr−1 for one, two, and three harvests per year, respectively. Two‐year mean CP concentrations were 52.7, 69.4, and 85.6 g kg−1 DM whereas IVDOM concentrations were 396, 549, and 580 g kg‐1 OM, respectively. Merkeron, N‐43, N‐51, and Mott persisted well. In PI 300086 plots harvested multiple times, major stand losses occurred over the 1987–1988 winter. Selection 3 did not persist. Adapted elephantgrass genotypes can persist in colder regions of the subtropics and should provide substantial quantities of forage.