bluuebunny/crossref_metadata_2025 huggingface dataset:
Wing‐Chisel Plow for In‐Row Conservation Tillage
Authors: Heilman M. D. , Valco T. D.
Published: July 2010

Conservation tillage in the semiarid subtropical region of South Texas should both maintain soil moisture and reduce wind erosion. Farming in the area historically uses seven to 10 tillage operations to prepare land for planting. The newly developed wing‐chisel has been effective in the once‐over desiccation of stubble from recently harvested crops. Additional benefits have included deep tillage to break any existing hardpan, controlled tractor traffic by using the chisel as an in‐row implement for a ridge‐till planting configuration, increased infilatration rates, and maintaining plant residue on soil surface. The plow, which is simple in design, when added to either disc or lister bedders becomes a once‐over tillage implement that accomplishes all necessary soil preparation between harvest and planting. Winter weed control between grain harvest and planting is accomplished by the use of contact herbicides.
Kinetics of In Vitro Cell‐Wall Disappearance and In Vivo Digestion
Authors: Fisher D. S. , Burns J. C. , Pond K. R.
Published: July 2010

Understanding the dynamics or kinetics of digestion and passage may suggest ways to manipulate forages to improve the diet, and consequently the production, of domesticated ruminants. The methodology of fitting exponential curves was tested using simulated cell‐wall‐disappearance curves with both an exponential and a gamma‐distributed exponential driving function and normal‐random variation superimposed. Nonlinear regression gave more precise estimates of the true rates of digestion and lag times than linearization. The gamma distributed exponential gave lower residual sum of squares but estimates of digestible and indigestible fractions as well as lag times and disappearance rates were not improved over the simpler exponential function. Estimates were less precise when the gamma‐distributed exponential was the driving function for the disappearance curve and the gamma function was skewed. The use of the exponential decay constant (k) in studies of cell‐wall composition is confounded with extent of disappearance as a result of plant anatomy. A surface area fermentability index (SAFI) is proposed as (kCd)/(1000 − Ci) where Cd and Ci are the digestible and indigestible fractions, respectively, of the cell wall. The SAFI was used to adjust literature values for k as well as to partially explain observed negative correlations between extent and rate of cell‐wall disappearance (k) in bromegrass (Bromus inermis Leyss.) that had been selected for high and low in vitro dry matter disappearance. Study of in vivo kinetics is complicated by variable rate of passage, particle size, and extent and rate of particle size reduction. Models of in vivo kinetics offer an opportunity for synthesis of understanding of the animal system. However, the many interactions make interpretation and incorporation of in vitro data into models of in vivo ruminant digestion difficult.
Osmotic Potential of Winter Wheat Crowns for Comparing Cultivars Varying in Winterhardiness
Authors: DeNoma J. T. , Taylor G. A. , Ferguson H.
Published: July 2010

Cold hardening of winter wheat (Triticum aestivum L.) crowns results in decreased water content, and in increases and changes in solutes. These facts led us to hypothesize that osmotic potential (ΨII) of hardened wheat crowns might be used as a screening technique for winterhardiness. Winter wheat with different levels of winterhardiness, ranked from long‐term trials, were grown in the field. Periodically, during two winters, plants were removed and the ΨII of the crowns determined. Contrast comparisons between two hardy, and two or three less hardy cultivars showed significant differences, at every sampling date with the hardy lines having lower ΨII. During one winter the ΨII of 24 cultivars whose winter‐hardiness had been evaluated over several years in the field was determined on three dates. Linear correlations (r2) between field scores (5 = most winterhardy, 1 = least hardy) and ΨII were highly significant, and varied from 0.75 to 0.83. Based on these data, we suggest that measurement of ΨII of winter wheat crowns following cold acclimation may be a valuable tool in the selection of winterhardy wheat cultivars
Soybean Seed Quality in Relation to Days between Development Stages
Authors: Vaughan Duncan A. , Bernard R. L. , Sinclair J. B.
Published: July 2010

Seed quality in soybean, Glycine max (L.) Merr., considering infection by seed pathogens, overall visual quality, and seed weight, is affected by date of maturity. We report on the relationship between seed quality, genotype, and late reproductive growth periods and discuss these results in relation to breeding for improved seed quality. The objectives of this study were to: (i) measure seed quality in genetically similar germplasm, but which differ in date of maturity, and (ii) to determine the effects of different reproductive growth periods on seed quality. The field experiments were conducted on Brenton (fine‐silty, mixed, mesic Aquic Argiudolls), Flanagan (fine, montmorillonitic, mesic Aquic Argiudolls) or Proctor (fine‐silty, mixed, mesic Typic Argiudolls) soils at the Agronomy‐Plant Pathology Farm, Univ. of Illinois at Urbana‐Champaign. Delayed maturity in male‐sterile and depodded soybeans resulted in increased seed infection by field seed pathogens probably by lengthening the period during which infection and colonization could take place. Early maturing, maturity isolines were associated with increased infection by Phomopsis spp. which is related to favorable environmental conditions such as warm temperatures and high humidity, which favor spread and growth of this pathogen. A positive relationship was also found between the length of time for late seed fill (Reproductive growth stages R6 to R7) and seed infection by Phomopsis spp.
Growth and Yield of Winter Wheat as Influenced by Chlormequat Chloride and Ethephon
Authors: Cox W. J. , Otis D. J.
Published: July 2010

Lodging can be a constraint in wheat (Triticum aestivum L.) production, therefore interest exists for use of plant growth regulators (PGRs) such as Chlormequat chloride or CCC (2‐Chloroethyl‐N, N, N‐trimethylammonium chloride) and ethephon [(2‐Chloroethyl) phosphonic acid] for lodging control. Field experiments were conducted in New York in 1985 and 1986 on a Honeoye silt loam (fine‐loamy, mixed mesic Glossoboric Hapludalfs) to examine the influence of CCC (1.37 kg ha−1 a.i. at Zadoks Growth Stage (GS) 31) and ethephon (0.40 kg ha−1 a.i. at GS 39) on vegetative and reproductive growth of two winter wheat cultivars, Geneva and Houser. Leaf, stem, and spike phytomass were determined at 10‐d intervals from GS 25 to 95, and kernel number and weight were determined on 15 main‐culm spikes at 3 to 4‐d intervals during the grain‐filling period. The CCC application reduced culm and total phytomass by 9% at GS 45, whereas ethephon reduced spike and total phytomass by 10 and 8% at GS 55 and GS 75, respectively. Neither PGR had an effect on total or component phytomass at harvest. In 1985, a year when no lodging occurred, ethephon and CCC yielded the same compared with the yield of the check (6.12, 6.60, and 6.39 Mg ha−1, respectively). In 1986, a year of considerable lodging, ethephon reduced lodging compared with that of CCC and the check, which was reflected in a higher kernel growth rate (1.00, 0.84, and 0.81 mg kernel−1 day−1), kernel weight (43.4, 39.8, and 38.9 mg), and grain yield 5.73, 4.71, and 5.30 Mg ha−1, respectively) in the more lodging‐susceptible cultivar, Houser. The data indicate that, under the environmental conditions of this study, CCC does not benefit wheat and that ethephon should be utilized only under severe lodging conditions.
Weather and Seed Quality Variables to Predict Cotton Seedling Emergence
Authors: Kerby T. A. , Keeley M. , Johnson S.
Published: July 2010

Emergence of cotton (Gossypium hirsutum L.) seedlings was related to seed quality and temperatures following planting in a 3‐yr field study at Shafter, CA. Environmental conditions for seed production were selected to provide a broad range in seed quality. Seed quality, as determined by the standard germination test and the cool test, was combined with heat units (HU) after planting for predicting field emergence percentage. A total of 74 seed lots (11 in 1984, 39 in 1985, and 24 in 1986) were planted at two different dates, and emergence of 100 seed from each of four replications evaluated. Warm germination percentage (W%) was measured at 30 °C, and ranged between 25 and 90%, cool germination (C%) was measured at 18 °C, and ranged between 1 and 88%, and field emergence percentage ranged from 5 to 98% in these studies. Multiple regression was used to determine the degree of association between variables. Predicting field emergence with C + W% was better than either component alone (r2 = 0.352 for n = 148). The HU (base 60 °F) for 5 or 10 d after planting explained as much variation in field emergence as seed quality (r2 = 0.348 and 0.365), but HU 15 d after planting were not related to field emergence. When HU 5 d after planting, C + W% percentage, and the interaction between the two were considered in multiple regression, 68.5% of the variation in field emergence was explained. With 10 HU 5 d after planting there was a linear increase in field emergence percentage as C + W% increased, but at 25 HU, seed with C + W% of 110 had as many seedlings emerge as lots with C + W% of 175. Eliminating seed lots with warm germination percentages less than 80 from these regressions did not alter the predicted values for field emergence within the range of the data, but did reduce the statistical significance of the relationship. The HU for 5 d can be forecast on the National Oceanic and Atmospheric Administration's (NOAA) weather radio with reasonable accuracy in the San Joaquin Valley of California. If temperatures can be forecast accurately in other regions, cotton growers can adjust seeding rates and plant to a desirable stand, if warm and cool germination percentages of planting seed are known.
Crop Yield as Affected by Rotation and Nitrogen Rate. III. Corn
Authors: Peterson Todd Andrews , Varvel G. E.
Published: July 2010

Corn (Zea mays L.) is a widely grown crop in the USA that responds positively to crop rotation. This study compares yields of corn grown in continuous monoculture with that of a (i) 2‐yr soybean [Glycine max (L.) Merr.1‐corn rotation; (ii) a 4‐yr soybean‐grain sorghum [Sorghum bicolor (L.) Moenchj‐oat + clover [Avena sativa L. interseeded with 80% Melilotus officinalis (L.) Lam., 20% Trifolium pratense]corn rotation; and (iii) a 4‐yr oat + clover‐grain sorghum‐soybean‐corn rotation. Interactions between crop rotation and N rate were also determined. The study was conducted for 4 yr on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Continuous corn produced less grain (5.5 mg ha−1 yr−1) than corn grown in rotation (7.6 Mg ha−1 yr−1 average). Corn following a legume in rotation produced maximum grain yield with 90 kg N ha−1, while continuous corn required at least 180 kg N ha−1 for maximum yield. Corn following oat + clover produced maximum yield in a year of above‐average precipitation, but this rotation was vulnerable to soil‐water deficits. In 3 of 4 yr, corn following soybean in a 4‐yr rotation produced more grain than other rotations.
Calcium Stimulation of Ammonium Absorption In Radish
Authors: Fenn L. B. , Taylor R. M.
Published: July 2010

Nitrogen loss processes in soils have been widely studied and there have been many suggestions for improving N‐use efficiency, such as using NH4‐NO3 fertilizers, split fertilizer applications, application timing, and other techniques. The objective of this research was to examine the use of Ca as a means to increase the rate of NH4 absorption by radish (Raphanus sativus L.). Short‐term 15NH4 absorption in the presence of variable Ca was measured in the greenhouse, long‐term plant growth responses to NH4 in the presence of variable Ca were measured both in the greenhouse and in field production trials. Ammonium absorption (15NH4) increased in plants with increasing solution Ca to a Ca/NH4 ratio of 0.5:1 in the tops and to 2:1 in the roots. Vegetative growth increased in two greenhouse experiments as Ca concentrations increased, all at a constant NH4 concentration. As the Ca concentration increased, the total N concentration increased in foliar tissue and decreased in the roots. In the 2 yr of field testing, dry weight yield of roots increased 77 and 55%, respectively, in the urea + Ca treatment compared with the urea treatment alone. In the second year field data, total plant absorption of the added urea‐N in the presence of added Ca increased by 109% compared with urea alone. Significant increases were found both in the root and foliar tissue N content, and growth in the 2 yr of field data. The addition of Ca with urea produced significantly improved plant N‐use efficiency in the field as was suggested from the greenhouse data.
Within‐Row Spacing Influences on Diverse Sorghum Genotypes: II. Dry Matter Yield and Foratge Quality
Authors: Caravetta G. J. , Cherney J. H. , Johnson K. D.
Published: July 2010

Research was conducted to determine changes in dry matter yield, cell wall composition, and digestibility of four diverse sorghum [Sorghum bicolor (L.) Moench.] genotypes as influenced by withinrow spacing. Genotypes (IS‐0469, IS‐0865, P‐954063, and IS‐2952) were selected to represent a range in morphology and cell wall composition, and were sown at five within‐row spacings of 5,10, 15, 30, and 60 cm at two field locations in 1986 and 1987. Harvested herbage was separated into stem, leaf sheath, and leaf blade components for main‐shoot and tillers. Forage dry matter yield declined linearly from 10.9 to 8.1 Mg ha−1 as within‐row spacing increased from 5 to 60 cm. Total forage neutral detergent fiber and permanganate lignin concentrations declined linearly from 717 to 700 g kg−1 and 79.5 to 71.5 g kg−1, respectively, as within‐row spacing increased from 5 to 60 cm. Main‐shoot permanganate lignin concentration in the stem component declined 15.3%, while leaf sheath and leaf blade components were relatively unchanged in lignin concentration with increased within‐row spacing. Total forage in vitro dry matter digestibility and N content increased 8.7 and 16.1%, respectively, as within‐row spacing increased. Reduced plant populations, through increased within‐row spacing, improved forage quality and increased digestibility and protein content, however, dry matter yield was significantly reduced. Within‐row spacing may significantly influence genotype selection for dry matter yield. Genotypic selection for improved forage quality in a breeding nursery should not be greatly affected by within‐row plant spacings of 15 cm or less.
Boll Shedding and Boll Load in Nitrogen‐Stressed Cotton
Authors: Jackson B. S. , Gerik T. J.
Published: July 2010

Boll shedding in cotton is thought to depend on the crop growth rate and the demand for plant assimilates by the growing bolls. This study was designed to test the hypothesis that the ratio of boll load (BOLL) and carrying capacity (CA), defined as the maximum boll load, could be used to index the boll shedding fraction for cotton plants with different crop growth rates. Cotton was grown in a greenhouse in 1987 and 1988 with 0, 18, 36, 72, and 144 mmol of N applied at 2‐wk intervals. In 1987, maximum leaf area index (LAI) for the five treatments ranged from 0.6 to 2.2 and maximum BOLL from 5.3 to 23.1 bolls m−2. In 1988, maximum LAI ranged from 1.2 to 4.2 and maximum BOLL from 9.1 to 39.5 bolls m−2. In both years boll sizes for the highest N treatment averaged 4.1 g seed cotton boll−1. Average boll sizes declined for treatments receiving less N, but only the 0 N‐treatment boll sizes were less than 80% of the 144 mmol N treatment. Boll shedding fractions depended on treatments and BOLL. However, for both years boll shedding fractions were highly correlated with the ratio BOLL/CA (R2 = 0.84). Assuming a 1:1 line, the standard error of estimate (SE) was 0.13. Values of CA were highly correlated with maximum LAI (R2 = 0.98) suggesting that the primary effect of N deficits was reduced light interception because of smaller LAI. This analysis suggests, therefore, that the ratio BOLL/CA can be used to index boll shedding fraction in cotton and, with some estimate of CA based on expected yields or LAI, may have value as an input for cotton crop management.
Development and Maturation of White Lupine Seed
Authors: Clapham William M. , Barnes Sarah L.
Published: July 2010

Unreliable ripening has limited production of white lupine (Lupinus albus L.) in northern temperate climates. Currently, there are no adequate methods to predict physiological maturity of this crop. The objectives of this study were to develop a descriptive index of maturation for white lupine pods and seeds, and to relate physiological maturity to the relationship between seed and pod moisture contents. Field data from a series of studies on the effects of planting date and plant density on white lupine growth and yield were used to generate the developmental index. The index was useful in determining developmental stages for both main‐stem and higher‐order lateral pods. Funicula detachment occurred between 55 and 80 kg kg−1 pod moisture content and was consistent with literature reports of physiological maturity, maturation drying and onset of desiccation‐tolerance. Rapid seed filling occurred when pod moisture content was greater than 83 kg kg−1 fresh weight. The relationship between pod and seed moisture content was linear and varied between years, but did not vary between main‐stem and lateral pods within year. At pod moisture content less than 83 kg kg−1, however, the relationship was curvilinear and did not vary over year or pod order (main‐stem or first‐order lateral pods). The change in slope of this relationship at 83 kg kg−1 pod moisture content may explicitly identify physiological maturity and the onset of maturation drying. Although lupine is harvested when seed moisture content falls below 20 kg kg−1, these data concur with reports in the literature suggesting that a lupine crop may be harvested when pod moisture content range from 55 to 80 kg kg−1 without loss of seed yield or viability.
Wind Profile Parameter Estimation Using Mathcad
Authors: Howell Terry A.
Published: July 2010

Wind profile parameters are required to estimate aerodynamic boundary layer resistances for heat, water vapor, and momentum transfer. Traditional methods used to compute these parameters take time to program, are slow to reach solutions, and often fail to achieve solution convergence. This study evaluated the applicability of a commercial mathematics software package, MathCAD, to estimate the three parameters—friction velocity (U*), zero‐plane displacement height (4, and the roughness length, Zo—of the adiabatic log‐law wind profile. The solutions were evaluated and compared to previous published solutions for several wind profiles using traditional methods. MathCAD was found to solve the wind profiles rapidly without convergence difficulty on the tested profiles. In all the comparisons, MathCAD produced almost exact duplications of previously published results. The ease, speed, and accuracy of the solution method employed in MathCAD appear to be superior to the more traditional methods.
Selenomethionine Uptake by Wheat Seedlings
Authors: Abrams M. M. , Shennan C. , Zasoski R. J. , Burau R. G.
Published: July 2010

Selenium acquisition by crops is of interest because it is an essential element for higher animals and because excessive levels are toxic to humans and livestock. This research was conducted to test whether uptake by plants of an important organic Se compound, selenomethionine, occurred through a metabolically active process. Selenomethionine absorption in 30‐d‐old wheat (Triticum aestivum L.) seedlings was measured by using a depletion method with two initial nutrient solution concentrations (0.5 and 1.0 μM) selenomethionine. Observed uptake rates were functions of solution concentration and were not affected by initial concentration. Uptake kinetics appeared to conform to the Michaelis‐Menten function but the initial concentrations were too low to estimate either Km or Vmax (maximum uptake rate when carrier or permease is saturated). Selenomethionine uptake was inhibited by a metabolic inhibitor, 2,4‐dinitrophenol, and by anaerobic conditions. Absorption resumed when aerobic conditions were restored to the anaerobic treatment. Experimental evidence shows that wheat seedlings can acquire the biologically important organic Se compound, selenomethionine. This acquisition is under metabolic control which further suggests that organic forms of Se must be considered as sources of plant available Se.
Barley Treated with Ethephon: III. Kernels per Spike and Kernel Mass
Authors: Moss J. , Stobbe E. H.
Published: July 2010

Treatment of barley (Hordeum vulgare L.) with ethephon [2‐chloroethyl)phosphonic acid)] may reduce lodging and increase kernel mass, but reductions in kernel mass and kernels per spike also are often observed. This study examined the effect of ethephon on kernels per spike and kernel mass for spikes on specific shoots which appeared before or after ethephon application. Ethephon was applied at Zadoks growth stage (GS) 35 and/or 45 at 240 g ha−1 to ‘Argyle’ conventional height and ‘Samson’ semidwarf barley grown at 100 and 300 plants m−2 at Winnipeg, MB. Tillers were tagged as they emerged on 10 plants per plot, and kernels per spike and kernel mass were determined for each spike produced. The cultivars did not differ in their response to ethephon. Kernels per spike was reduced as much as 26% by ethephon application. Such reductions were attributed to both the promotion of late‐appearing shoots with relatively few kernels, and the abortion of florets on main stems and early appearing tillers, which may be due to ethephon's gametocidal properties. Kernel mass was reduced by up to 17%, not affected, and increased by up to 12% by ethephon in 1987, 1988, and 1989, respectively. Differences in competition between developing kernels and late tillers, in lodging, and in nitrogen availability may account for the variable kernel mass responses observed. Kernels per spike and/or kernel mass reductions generally resulted in decreased yield per plant, especially for barley grown at 300 plants m−2, but such reductions were at least partially compensated by increased spikes per plant for barley grown at 100 plants m−2 in 1987 and 1989.
Yield Components in Three Meadowfoam Lines
Authors: Fiez Timothy E. , Norberg O. Steven , Jolliff Gary D.
Published: July 2010

Future development of high‐yielding meadowfoam (Limnanthes R. Br. spp.) cultivars may be enhanced if relationships between oil yield, yield components, and agronomical, phenological, and morphological traits can be established. To identify such relationships, two half‐sib L. floccosa Howell ssp. grandiflora Arroyo × L. alba Hartw. ex Benth. ssp. alba lines, ORL85‐765 and ORL85‐729, and ‘Mermaid’ meadowfoam were grown and compared in solid stand in 1987–1988 and 1988–1989 at the Oregon State University Schmidt Farm. Line 85‐765 produced the greatest oil yield in 1987–1988. Seed weight of line 85‐765 was 18 and 13% greater (P < 0.05) than lines 85‐729 and Mermaid, respectively, in 1987–1988. In 1988–1989, both lines 85‐765 and Mermaid produced greater oil yields than line 85‐729. Line 85‐765 produced a 7% greater seed weight and Mermaid produced 55% more seeds per flower than line 85‐729 (P < 0.05). Oil yields of lines 85‐765 and Mermaid were not significantly different in 1988–1989. Seed weight of line 85‐765 was 9% greater than Mermaid in 1988–1989, but Mermaid produced 31% more seeds per flower than line 85‐765 (P < 0.05). Seed weight differences were apparently due to variation in seed growth rate and not seed growth duration. Differences in seeds per flower were not related to pollinator activity or flower phenology. Both seed weight and seed number per flower were important yield components for determining the relative oil‐yield performance of lines 85‐765, 85‐729, and Mermaid.
Bulk Surface Resistance and Its Effect on Evapotranspiration Rates in Irrigated Wheat
Authors: Luchiari A. , Riha S. J.
Published: July 2010

Use of the combination model to predict evapotranspiration (ET) from a crop has been limited by uncertainty in the value and behavior of the bulk sulface resistance (rb). The purpose of this study was to characterize rb for irrigated wheat (Triticum aestivum L.) and evaluate its use for predictive purposes. Hourly Bowen ratio measurements were made over a field of irrigated ‘Anahuac’ wheat during the entire growing season of 1983. Data from 4 d were used to calculate rb using both the energy balance and residual methods. Crop surface temperatures predicted from measurement of wind speed and air temperature at one height above the canopy were within 0.4 °C of infrared measured canopy temperatures. Both the energy balance and residual methods gave similar values for rb. From 0830 h to 1430 h the day before irrigation, values for rb ranged from 50 to 100 s m−1 whereas after irrigation, rb for the same period ranged from 15 to 50 s m−1. In both cases, rb rapidly increased after 1430 h to values above 200 s m−1 by 1630 h. At the same time, latent heat loss in proportion to net radiation increased and canopy temperature decreased more rapidly than air temperature, suggesting that the increase in rb at this time is not due to a lag in the supply of water to the canopy. The combination model was used to predict ET on both an hourly and daily basis for several periods during another crop growing season. Mean predicted values were within 6% of Bowen ratio measurements and were highly correlated with hourly and daily measured rates of ET, suggesting that the combination model can be used for predictive purposes when rb is well characterized.
Value of Selection for Osmotic Potential in Tropical Maize
Authors: Bolaños J. , Edmeades G. O.
Published: July 2010

Osmotic adjustment, the lowering of osmotic potential (ΨS) under drought, is considered a desirable component of drought tolerance since it has been shown to maintain turgor, growth, and photosynthesis at lower water potentials. This study attemped to determine the relative merits of selecting for osmotic adjustment and low ΨS under drought in lowland tropical maize (Zea mays L.). During 3 yr of trials in Mexico that examined 204 maize landacres, elite open pollinated populations (OPPs), experimental synthetics (ESs), and hybrids, osmotic adjustment averaged 0.10 MPa and ranged from 0.54 to −0.23 MPa. Only 7% of genotypes showed a capacity to adjust by more than 0.40 MPa, a level considered minimum for them to serve as sources for the trait. Variation for ΨS, under drought for 222 to 225 S1 progeny of three maize populations ranged from −1.04 to −1.79 MPa. Divergent selection within each population for high and low ΨS under drought resulted in the formation of ESs which differed in ΨS by an average of 0.17 MPa when grown under a line source moisture gradient. Realized heritability for ΨS averaged 0.46. The ESs selected for high and low ΨS did not yield differently from the cycle bulk, suggesting little adaptive value for ΨS Correlations between several traits indicative of performance under drought and osmotic adjustment or ΨS under drought generally were weak, inconsistent, and non‐significant. These studies suggest that selecting for increased capacity to adjust osmotically or low ΨS under drought does not appear advantageous in lowland tropical maize.
Barley Tiller Response to Plant Density and Ethephon
Authors: Lauer Joseph G.
Published: July 2010

Ethephon ([2‐chloroethyl] phosphonic acid), typically increases barley (Hordeum vulgare L.) spikes per square meter by increasing the frequency of late emerging green tillers, resulting in uneven crop maturity. This study was conducted to evaluate barley tiller grain yield and malting quality response to plant density and ethephon, with special reference to late‐emerging green tillers. Field studies were conducted at Powell, WY between 1987 and 1989 on a Garland clay loam (fine, mixed, mesic Typic Haplargid). Target plant densities of 150 and 300 plants m−2 were established. Ethephon was applied at the Zadoks growth stages (ZGS) of 13, 32, or 39, and one treatment was split‐applied at ZGS 32 and 39. Early emerging primary tillers (Tl, T2, and T3) and the main shoot contributed 86% of the total grain yield at high plant density vs. 73% at low plant density. In general, increasing plant density resulted in progressively greater differences for kernel plumpness and kernels per spike on the MS, Tl, T2, and T3. Ethephon applied at ZGS 39 reduced plant height 6 to 15 cm depending on year. Lodging was reduced by ethephon application, although the lodging level was low in every year of the study. Ethephon did not affect grain yield or protein content, but it often reduced volume mass and kernel plumpness compared to the untreated control. Regardless of ethephon treatment, kernels on late emerging tillers were of lower mass, volume mass, and plumpness than kernels on early emerging tillers. Ethephon applied at ZGS 39 increased the number of late emerging green tillers by 225 spikes m−2 compared with the control. These late emerging green tillers contributed 8% to the total grain yield but produced grain of substandard malting quality.
Resource Use and Plant Interactions in a Rice‐Mungbean Intercrop
Authors: Aggarwal P.K. , Garrity D.P. , Liboon S.P. , Morris R.A.
Published: July 2010

Intercropping of upland rice (Oryza sativa L.) with short‐duration grain legumes has shown promising productivity and resource use efficiency. To better understand intercrop relationships, we used aboveand underground partitions, residue removal, and plant removal to investigate the interactions between upland rice (120‐d crop duration) and mungbean [Vigna radiata (L) Wilczek, 65‐d crop duration]. Treatments were evaluated during two rainy seasons on an unfertilized Typic Tropudalf at Los Baños, Philippines. Nitrogen uptake by intercropped rice (33.4 and 41.1 kg N ha−1) approximated that of sole rice (35.4 and 38.1 kg N ha−1). Intercropped rice yielded 73 to 87% of sole rice and intercropped mungbeans yielded 59 to 99% of sole mungbean. Root barriers did not affect rice N uptake or dry matter accumulation prior to the maturity of the mungbean, but reduced N uptake, dry matter, and grain yields substantially by the time of rice harvest. Sole rice with every third row removed at mungbean harvest had N, grain, and dry matter yields similar to the intercropped rice with every third row occupied by the legume. Sole rice with every third row vacant during the entire growing season yielded similarly (2.6 Mg h−1) to sole rice (2.3 Mg h−1) and intercropped rice (2.0 Mg h−1). There was no evidence that N transfer from the legume to the rice increased N availability to rice above that expected with a sole rice crop with the same planting scheme. Rice yield compensation in the intercrop was apparently due to the increased soil volume for N extraction and increased aerial space available after mungbean harvest.
Peanut Root Response to Drought Stress
Authors: Meisner C. A. , Karnok K. J.
Published: July 2010

Knowledge concerning the response of peanut [Arachis hypogaea (L.)] root growth during stress and to irrigation after stress is limited. This study was conducted to determine the effect of timing of water stress imposition on peanut root growth, reproductive development, and pod yield. Root growth was measured weekly using nondestructive methods in rhizotron chambers containing a 4:1 mixture of sand and fritted (calcified) clay. A portable rain shelter was used to impose 30‐d stress treatments beginning at 20, 50, 80, and 110 d after planting (DAP), in addition to a well‐watered control. Root growth was significantly reduced in the upper 40‐cm depth during stress from 20 to 50 DAP compared to root growth during the same period of the wellwatered control. No other stress periods resulted in significantly altered root growth compared to the control. Root growth was not affected in the lower depths of this treatment by stress because of adequate soil moisture. Upon rewatering, there was a trend for root growth to recover and continue further into the season for the two stress treatments beginning at 20 and 50 DAP. By the end of the season, there were no differences in overall average root growth among treatments. Peanut root growth may be temporarily reduced during early stress but appears to recover once rewatered. Pod yields were reduced, 49 and 37%, compared with the control by stress imposed at 50 and 80 DAP, respectively. Thus, adequate moisture during 50 to 80 and 80 to 110 DAP is critical for obtaining maximum yields.
Scanning Electron Microscopy for Studying Root Morphology and Anatomy in Alfalfa Autotoxicity
Authors: Hegde Ramesh S. , Miller D. A.
Published: July 2010

The aqueous extract of alfalfa (Medicago sativa L.) shoots inhibits root elongation, shoot elongation, and/or germination of alfalfa itself‐a phenomenon termed autotoxicity. The study of the mode of action of allelopathic and/or autotoxic compounds at the plant organ and cellular levels is limited by the depth of field, resolution, and magnification of a light microscope compared to a scanning electron microscope. Scanning electron microscopy techniques were used to study the morphology and anatomy of the roots inhibited by the water‐extract of alfalfa shoots. Investigations on the morphology of shoot‐aqueous‐extract‐inhibited, 5‐d old ‘WL‐316’ alfalfa roots revealed a 46% reduction in density and 54% reduction in length of root hairs compared to the control. Anatomical differences between the inhibited and uninhibited alfalfa roots were also observed. Shoot aqueous extract did not cause clogging of xylem vessels. The scanning electron microscope is a valuable tool in the study of the mode of action of allelopathic or autotoxic compounds at the plant organ as well as cellular levels.
Genotype‐by‐Tillage Interactions in Hard Red Winter Wheat Quality Evaluation
Authors: Cox D. J. , Shelton D. R.
Published: July 2010

Winter wheat (Triticum aestivum L.) is grown under both conventional‐till and conservation‐till systems in the Northern Great Plains. A benefit of sowing winter wheat into standing stubble is the protection the crop receives from trapped snow and the resultant reduction in winter kill. A 5‐yr study was conducted at four locations in North Dakota to measure cultivar‐by‐tillage interactions for quality parameters of wheat and to determine whether testing under both conventional‐till and no‐till systems was advantageous. Fourteen hard red winter wheat cultivars were planted during 1984‐1985 through 1988‐1989 in a Max loam (fine‐loamy, mixed, Typic Haploborolls) at both Williston and Minot, in a Svea loam (fine‐loamy, mixed, Pachic Udic Haploborolls) at Langdon, and in a Bearden silty clay (fine‐silty, frigid, Aeric Calciaquolls) or Gardena silty loam (coarse‐silty, mixed, Pachic Udic Haploborolls) at Fargo. Significant cultivar‐by‐tillage interactions (P < 0.05 or P < 0.01) were obtained for volume weight, protein content, and flour yield when the analysis was restricted to environments in which wheat winter killed. A change in rank order of cultivars was detected only for volume weight. For the other quality parameters measured, evaluation of winter wheats grown in conventional‐till and no‐till plots resulted in similar relative performance of cultivars.
Efficiency, Competitiveness, and Persistency of Chinese Rhizobium fredii in Iowa Soils
Authors: Manjanatha M.G. , Loynachan T.E. , Atherly A.G.
Published: July 2010

Native Bradyrhizobium japonicum occupy the majority of Midwest soybean [Glycine max (L.) Merr.] nodules despite inoculation with more effective N2‐fixing bradyrhizobia. The objective of this study was to determine whether three fast‐growing strains of Rhizobium fiedee obtained from soybean fields in China could displace the highly competitive native strains from the nodules of commonly grown Iowa‐soybean cultivars. Before introducing these nonnative organisms into Iowa soils, we evaluated their effectiveness under greenhouse conditions compared with the effectiveness of B. japonicum strains USDA 110 and USDA 123. There was a dominant strain‐by‐cultivar interaction, and two of the three fast‐growers were as effective in N2 fixation as was USDA 123, but were less effective than was USDA 110. Furthermore, we evaluated the competitiveness of the fast‐growers against native bradyrhizobia in six different soils in the greenhouse. Nodule occupancy by the fast‐growers ranged from 1.5 to 38.7%. Results indicated significant cultivar‐by‐soil, strain‐by‐soil, and soil‐by‐strain‐by‐cultivar interactions. For field tests, two separate sites were selected each year in the summers of 1987 and 1988. Each of the three strains was introduced into soils at approximately 106 colony forming units (CFU) cm−1 row. Nodule occupancies for the four site years on Corsoy 79 and Williams 82 soybean cultivars ranged from 3.8 to 13.3%. The saprophytic survivability of fast‐growers, based on nodule occupancy of field‐collected soil in the greenhouse, was tested 2 and 3 yr after inoculation. Fast‐growing rhizobia isolated from nodules were identified by their acid production on an artificial medium, and the reliability of this method was verified by comparing restriction‐endonuclease‐digestion patterns of plasmid DNA of test and reference strains. The nodule occupancies by strains of R. fredii on Williams 82 ranged from 8.6 to 13.3% and 4.4 to 11.3%, 2 and 3 yr after inoculation, respectively. Thus, the strains of R. fredii were able to persist in soil reasonably well as saprophytes.
Corn Growth Following Cover Crops: Influence of Cereal Cultivar, Cereal Removal, and Nitrogen Rate
Authors: Tollenaar M. , Mihajlovic M. , Vyn T. J.
Published: July 2010

Rye (Secale cereale L.) cover crops often delay development and reduce yield of corn (Zea mays L.). A 3‐yr study (1982‐1984) conducted to investigate the influence of four rye cultivars and one wheat (Triticum aestivum L.) cultivar, rate of N application in the spring, and removal of above‐ground cereal phytomass on growth and development of corn. Experiments were carried out at the Elora Research Station, Ontario, in a split‐plot design, with two N levels (145 and 220 kg ha‐1) and five cereal cultivars as main plots, and cereal phytomass removal or retention as sub‐plots. Cereal cultivars were planted in September after corn harvest and corn was planted in the spring. Corn leaf number and height were monitored during early corn development and whole‐plant dry matter and moisture of corn were measured in September. The response of corn dry matter accumulation to cereal cover crop cultivar, N rate, and above‐ground cereal phytomass varied among the 3 yr the study was conducted. Cereal phytomass was largest in 1983 and the impact of the cereal cover crop on corn growth and development was largest during this year. In contrast, the impact of cereal cultivar on corn was not associated with phytomass production among the five cereal cultivars. The effects of cereal cultivar cover crop on corn growth and development were largest for the rye cu|tivar Kodiak and the wheat cultivar Gordon, but these cultivars ranked third and fifth, respectively, in above‐ground phytomass production in the spring. Increased N application could partially overcome the reduction in corn growth and development due to the cereal cultivars Kodiak and Gordon, but this was not the case for the other cereal cultivars. Removal of above‐ground cereal phytomass before corn planting generally did not influence the delay in development and reduction in yield of the subsequent corn crop. In conclusion, the reduction in corn dry matter accumulation in response to cereal cover crops is a complex phenomenon, involving quantity of cereal residue, cereal cultivar and, occasionally, N application.
Cation and Nitrate Leaching in an Oxisol of the Brazilian Amazon
Authors: Cahn M. D. , Bouldin D. R. , Cravo M. S. , Bowen W. T.
Published: July 2010

High rates of N fertilizers are often necessary to achieve yield goals in the humid tropics, where subsoil acidity prevents deep crop rooting. However, leaching of fertilizer nitrate may accelerate the leaching of bases from the crop rooting zone, leading to an acidification of the topsoil and a reduction in crop yields. Our ojective was to investigate the influence of urea and legume green manure sources of N on crop yields, leaching of cations, and the fertility of the plow layer of a clayey Oxisol (Typic Acrudox) of the central Amazon basin. We established a split‐plot field experiment near Manaus, Brazil where main plots received 2 levels of lime (0 and 4 Mt/ha CaCO3) and sub‐plots were cropped with (i) a legume green manure (Canavalia ensiformes L. or Mucuna aterrima L.) followed by maize (Zea mays L.); (ii) maize receiving 300 kg ha−1 of urea‐N, or (iii) left bare‐fallow with an application of 300 kg ha−1 of urea‐N. Plots were periodically sampled to 1.2 m during three cropping seasons. The field site received 4265 mm of rain during the experiment (16 mo). Legume crops accumulated between 142 and 280 kg ha−1 of N. The distribution of NO3 in the soil profile changed in a pattern consistent with leaching. All treatments lost Ca and Mg from the plow layer during the experimental period. Losses were greatest (500–1000 kg ha−1 for Ca and 50 kg ha−1 for Mg) in plots treated with urea and lime. Leaching of bases and the generation of acidity decreased base saturation in the plow layer of all treatments, but was minimized in plots receiving legume green manure N, perhaps because less inorganic N was applied and/or the legume crops recycled leached bases. Unlimed plots receiving urea, had the highest increase in acidity in the 0 to 30‐cm layer and a corresponding 44% reduction in grain yield between the first and third maize crops.
Forage Quality, Mineral Constituents, and Performance of Beef Yearlings Grazing Two Crested Wheatgrasses
Authors: Vogel K. P. , Gabrielsen B. C. , Ward J. K. , Anderson B. E. , Mayland H. F. , Masters R. A.
Published: July 2010

In the central Great Plains, crested wheatgrasses [Agropyron cristatum (L.) Gaetner and A. desertorium (Fischer ex Link) Schultes] are best utilized for early spring and late fall grazing. The principal objective of this study was to determine if beef (Bos taurus L.) yearlings grazing ‘Ruff’ (A. cristatum) during the spring grazing season had higher average daily gains and gains per hectare than cattle grazing ‘Nordan’ (A. desertorum). These cultivars were evaluated in grazing trials (four replications) in eastern Nebraska in 1985, 1986, and 1987. The 0.8‐ha pastures were seeded in the fall of 1983 on a Typic Argiudoll soil and were fertilized annually with 68 to 90 kg N ha−1. Grazing was for 6 wk each spring by yearling steers with a beginning average weight of 250 kg. Averaged over 3 yr, Ruff produced higher gains per hectare than Nordan (272 vs 245 kg ha−1) probably because it produced more herbage because of its better persistence. At the end of the trial, the averge basal cover of Ruff and Nordan were 21 and 6%, respectively. Three‐year mean average daily gains were Ruff = 1.28 vs. Nordan = 1.34 kg d−1, which were unexpected, because Ruff generally had higher forage quality as measured by an array of parameters. Ruff forage had a higher, less desirable grass tetany ratio [K/(Mg+Ca)] than Nordan (2.6 vs. 2.3) averaged over 3 yr. Cattle grazing Ruff had lower blood serum Mg levels than rattle grazing Nordan (15.4 vs. 16.2 mg −1, both of which were below the hypomagnesemia threshold of 18 mg L−1. This condition may have reduced intake and animal gains. These results indicate the need for evaluating pasture and range grass cultivars under grazing conditions.
Monoculture and Rotation System Effects on Precipitation Use Efficiency of Corn
Authors: Varvel Gary E.
Published: July 2010

Development and utilization of cropping systems in rainfed areas are highly dependent on their water use efficiencies, especially in subhumid areas. The objective was to evaluate the effect of crop rotation and N fertilizer rates on precipitation use efficiency by dryland corn (Zea mays L.). Corn was grown under rainfed conditions at Mead, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) in four cropping systems: (i) continuous corn, (ii) a 2‐yr soybean [Glycine max (L.) Merr.]‐corn rotation, (iii) a 4‐yr rotation of oat [Avena sativa (L.)] + clover [80% Melilotus officinalis Lam. and 20% Trifolium pratense L.]‐grain sorghum [Sorghum bicolor (L.) Moench]‐soybean‐corn, and (iv) a 4‐yr rotation of soybean‐grain sorghum‐oat + clover‐corn. Nitrogen fertilizer rates used for corn were 0, 90, and 180 kg N ha−1 as NH4NO3. Corn grain precipitation use efficiency was significantly affected by year, rotation, and N fertilizer rates from 1984 through 1991. Precipitation use efficiency ranged from 36 to 137 kg ha−1 cm−1 for continuous corn and from 57 to 165 kg ha−1 cm−1 for corn grown in rotation from 1984 through 1991. Precipitation use efficiency was greater in rotation (101.8 kg ha−1 cm−1) than in continuous corn (83.6 kg ha−1 cm−1). In dryland production areas, cropping systems with greater and more stable precipitation use efficiency can reduce crop failures.
Sorghum Germination and Development as Influenced by Soil Temperature and Water Content
Authors: Anda A. , Pinter L.
Published: July 2010

In Hungary, the seed‐bed temperature at the customary planting time for sorghum [Sorghum bicolor (L.) Moench] is typically close to the base temperature, 10°C (the temperature at which there is zero development). At low soil temperatures, soil water may also be critical. This 30‐d phytotron study examined the combined effect of low soil temperature at two soil water levels on sorghum emergence and early development. Ten initial soil temperatures (7–16°C) and two soil water treatments (high and low: −0.04 and −0.2 MPa water pressure, respectively) were used. Since, after 19 d (5–24 June), there was no emergence at soil temperatures below 9°C, soil temperature in all pots was increased to 20°C and was maintained at this level until the end of experiment on 5 July. Percent emergence increased with increasing initial soil temperatures. The slope of this curve was four times steeper with −0.04 than −0.2 MPa water pressure. The improved microclimatic conditions caused by higher initial soil temperatures led to faster emergence, which may have produced better sorghum seedling establishment. Although seeds sown in soil with alternating low (below base temperature) and high seed‐bed temperatures can emerge, quick emergence and adequate plant density is less likely. In Hungary, where both air and seed‐bed soil temperatures vary a great deal around sorghum planting time, it is better to wait until the upper soil temperature stabilizes above 10°C, the base temperature for sorghum.