bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Marketed Cellulases for Activity and Capacity to Degrade Forage1
Authors: Gabrielsen B. C.
Published: July 2010

Cellulase‐solubility procedures provide an alternative method for evaluating forage digestibility; however, variable activities of marketed cellulase preparations complicate determination of optimum enzyme‐substrate proportions. This study was conducted to evaluate and compare exo‐ (Cl) and endo‐ (Cx) β‐1,4‐glucanases plus β‐glucosidase, and filter paper (FP) activities of various cellulase preparations and the capacity of these preparations to degrade forage. The use of cellulase in an in vitro forage digestibility assay based on FP activity units was also examined. Cellulase components (i.e., Cl, Cx, and β‐glucosidase) and FP activities were determined in four marketed cellulase preparations using established procedures. Supplemental additions of a marketed β‐glucosidase preparation to cellulase digestions were also evaluated. The cellulase preparations exhibited considerable differences in component enzyme activities and these differences were reflected in estimates of FP activity and the capacity of the cellulases to degrade forage. High levels of forage degradation were associated with high Cl/Cx activity ratios. Separate additions of β‐glucosidase did not increase forage degradation over that of the cellulase used alone. Cellulase‐solubility of 30 warmseason and 27 cool‐season grasses was highly correlated with rumen fermentation in vitro dry matter digestibility. Cellulase‐solubility values were generally lower than those obtained by the rumen fermentation method, however, Spearman rank‐order correlations indicted similar sample rankings by either assay method. The results indicate that component enzyme activity is highly variable among marketed cellulases and these differences influence the capacity of enzyme preparations to degrade forage. Filter paper activity units may be used to determine optimum enzyme‐substrate proportions in a digestibility assay; however, cellulase‐solubility methods which utilize marketed enzyme preparations may be more suitable for applications in which prediction of absolute in vivo digestibility values is less important than detection of relative differences.
Relationships between Taproot and Crown Characteristics and Yield and Quality Traits in Sugarbeets1
Authors: Campbell L. G. , Cole D. F.
Published: July 2010

Increasing the yield or quality, or both, of a crop through plant breeding or changing production practices is often futile if one does not have some knowledge of plant response to environmental changes. Data from 17 environments (years ✕ locations) and nine sugarbeet (Beta vulgaris L.) cultivars were used as a basis for examining relationships among yield and quality characteristics and the corresponding changes in taproot and crown size and weight that occur over diverse environments. Root yield and sucrose loss to molasses were positively correlated with each other and negatively correlated with sucrose concentration. Except for lateral root weight and taproot length, all taproot and crown characteristics were positively associated with root yield and sucrose loss to molasses and negatively associated with sucrose concentration. The only morphological characteristics significantly correlated with sucrose loss to molasses were crown traits. Canonical correlation indicated that the relationships among yield and quality traits were strongly associated with relative crown size. Much of the ability to respond to more favorable environments appeared to be related to the production of larger crowns. Root circumference increased as environment improved but not as markedly as crown length and weight. Increases in taproot length appeared to be associated with low yields, high sucrose concentrations, reduced circumference, and lower crowns.
Competition for Nitrogen‐15‐Depleted Ammonium Nitrate between Arrowleaf Clover and Annual Ryegrass Sown into Bermudagrass Sod1
Authors: Morris D. R. , Weaver R. W. , Smith G. R. , Rouquette F. M.
Published: July 2010

Ability to compete for mineral N effects stand stability of arrowleaf clover (Trifolium vesiculosum Savi) and annual ryegrass (Lolium multiflorum Lam.). Two field experiments were conducted on a Darco soil (loamy, siliceous, thermic Grossarenic Paleudult) to investigate the competitive ability of ‘Yuchi’ arrowleaf clover and ‘Gulf’ ryegrass for uptake of 15N‐depleted ammonium nitrate when seeded into dormant bermudagrass (Cynodon dactylon L. pers.). When N was applied in February, ryegrass in pure stand recovered more than two times as much fertilizer N as did clover in pure stand and more than 80% of the fertilizer N when in a mixture with clover. The April application of N resulted in the clover in pure or mixed stand recovering as much or more fertilizer N as did the corresponding ryegrass in pure or mixed stand. Growing clover in mixed stand with ryegrass increased the percentage of the N in the clover derived from N fixation by an average of 23%. Application of fertilizer N reduced the percentage of total N in the clover derived from N fixation by an average of 19%. Total N in the clover from N fixation was either unchanged or reduced when clover was grown with ryegrass and when fertilizer N was applied. Efficiency of fertilizer‐N usage by either plant species ranged from a low of 5 to 70%, depending on timing of application and plant species.
Effects of Turf Cultivation Practices on the Efficacy of Preemergence Grass Herbicides1
Authors: Branham B. E. , Rieke P. E.
Published: July 2010

A 2‐yr field study was conducted to determine the effects of cultivation operations on the efficacy of three preemergence herbicides used in turf. Cultivation is an important cultural practice used to relieve soil compaction and improve turf rooting, but it is often avoided in the spring for fear of disrupting the preemergence herbicide and reducing annual grass control. Benefin (N‐butyl, N‐ethyl‐α, α,α‐trifluoro‐2,6‐dinitro‐p‐toluidine) at 2.2 kg ha−1, bensulide [S‐(O,O‐di‐isopropyl phosphorodithioate) ester of N‐(2‐mercaptoethyl) benzenesulfonamide] at 11.2 kg ha−1, and DCPA (dimethyl tetrachloroterephthalate) at 11.8 kg ha−1 were applied to an annual bluegrass [Poa annua var. reptans (Hauskins)] turf growing on an Owosso‐Marlette sandy loam complex (fine‐loamy, mixed, mesic Typic Glossobic‐Hapludalfs). Four cultivation treatments consisting of core cultivation one pass or three passes, vertical mowing, and a control were applied at the time of herbicide application or 4 weeks after herbicide application. Crabgrass [Digitaria sangiunalis (L.) Scop.] populations were evaluated throughout the summer to determine the effects of the herbicide and cultivation treatments. Neither cultivation nor time of cultivation had a significant effect on the degree of crabgrass control afforded by the herbicides. The only significant difference in the study occurred when comparing the herbicide‐treated plots to an untreated control. Data indicate that cultivation operations can be safely performed in the spring without disrupting the preemergence herbicide barrier.
Forage Kochia Germination Response to Temperature, Water Stress, and Specific Ions1
Authors: Romo James T. , Haferkamp Marshall R.
Published: July 2010

Forage kochia [Kochia prostrata (L.) Schrad.] may be useful for revegetating salt affected soils. This study was designed to quantify the effects of temperature, water stress, and specific ions on the germination of ‘Immigrant’ forage kochia. Fruits and seeds were germinated at 10, 20 and 30°C in solutions of polyethylene glycol (PEG) with osmotic potentials ranging from −0.52 to −2.32 MPa. Seeds were also germinated at 20°C in PEG solutions containing 0 to 53 640 µmol L−1 potassium chloride (KCl‐PEG) and 0 to 68 480 µmol L−1 sodium chloride (NaCl‐PEG) with osmotic potentials ranging from −0.3 to −2.2 MPa. Germination was reduced by declining osmotic potentials. Total germination was highest at 20°C and lower at 10 and 30°C. Germination in NaCl‐PEG and KCl‐PEG solutions was primarily reduced by low osmotic potentials; percent germination was not affected by increasing NaCl concentrations but was reduced by increasing KCl concentrations. Number of days to 50% final germination was similar in both salts, increasing as osmotic potential declined and salt concentration increased. Forage kochia appears moderately tolerant of NaCl and KCl during germination and growth and may be well suited for revegetating salt affected soils in the Intermountain Region. Fruits are recommended for planting because abnormal germination was less than with seeds. Forage kochia should be sown prior to periods when soil temperatures are in the 10 to 20°C range, and cultural practices that extend the period of high soil osmotic potentials should be used to maximize seed germination.
Response of Tomatoes to Lime and Phosphorus on a Sandy Soil1
Authors: Rhue R. D. , Everett P. H.
Published: July 2010

Very little work has been done on the P requirements of tomatoes (Lycopersicon esculentum Mill.) when grown on acid, poorly drained sands using seepage irrigation and plastic mulch systems. To determine the response of tomatoes to P under these conditions, a study was conducted on an acid Immokalee sand (sandy, siliceous, hyperthermic Alfic Arenic Haplaquod) located near Immokalee, FL. Dolomitic lime was applied in November 1981 at 0, 2240, and 4480 kg/ha and P was applied in January 1982 at 0, 122, 245, and 367 kg/ha in a split‐plot design with lime as main plot and P as subplot treatments. Plots were split in 1983 and 1984 and P was applied at 0 and 20 kg/ha each year. A significant interaction between lime and P treatments occurred in 1982 with respect to yield. High rates of P without lime reduced yields by about 25 Mg/ha compared with the other treatments. The yield depression was not explained by differences in leaf P, Mn, or Zn concentrations, but was associated with leaf Mg that declined steadily to 4.5 g/kg or less by harvest. Yield responses to the dolomitic lime occurred in the second and third years when leaf Mg was also about 4.5 g/kg. Large applications of P without lime resulted in no increase in extractable soil P after 3 yr. Application of lime and P increased extractable P slightly, but the increase was not accompanied by a measurable increase in P availability to tomatoes.
Determining Transferability of Solar Radiation Data1
Authors: Trent Anthony , McKinion James M.
Published: July 2010

Solar radiation is the primary driver for most process level crop models, and because of the lack of solar radiation reporting stations available to the modeller, it is sometimes necessary to transfer data from the nearest reporting station for use at the desired locale. The reason for this investigation was to determine statistically if solar radiation collected at three different locales in Mississippi could be used interchangeably. The statistical procedure, spectral analysis, was used to examine the data collected at the three sites with the result that, statistically, data collected at one site could not be used at another site. Further work is needed in this area to determine the maximum distance solar radiation might be transferable.
Relationships of Soil Properties and Rainfall to Effects of Subsoiling on Tobacco Yield1
Authors: Vepraskas M. J. , Miner G. S. , Peedin G. F.
Published: July 2010

The effect of subsoiling on tobacco (Nicotiana tabacum L.) yield is variable across soils, and the reasons for this are not completely understood. As a result, it is difficult to identify soils where subsoiling will increase yields. This study evaluated relationships among relative yield increases due to subsoiling (RYI's), soil properties, and rainfall. Single‐season tillage experiments were conducted at 32 locations from 1981 through 1984. Soils were Paleudults and Hapludults. Tobacco yields were measured for subsoiled and nonsubsoiled (moldboard plow/disk) tillage treatments at all sites. Rainfall was measured daily. Soil properties evaluated included bulk density, cone index, texture, water retention, exchangeable cations, pH, and base saturation. Relative yield increases due to subsoiling ranged from −9.0 to 31.8% across locations. Twelve sites had yields significantly (0.05 level) increased by subsoiling. Stepwise regression analysis showed that selected weekly rainfalls and drought duration were major factors related to RYI variations, and with water retention of Ap and E‐B horizons, they accounted for 60% of the variation in RYI across all sites. Relative yield increases were greatest during dry years on sandy soils with low water retention values. Sites where relatively large RYI's (> 13%) occurred were characterized as having both bulk densities ≥ 1.63 Mg m−3 in the lower Ap or E‐B horizon and sand contents ≥ 73% in the Ap horizon.
Soybean‐Wheat Doublecropping: Implications from Straw Management and Supplemental Nitrogen'1
Authors: Hairston J. E. , Sanford J. O. , Pope D. F. , Horneck D. A.
Published: July 2010

Doublecropped soybean [Glycine max (L.) Merr.] following winter wheat (Triticum aestivum L.) is usually planted past the optimum date for monocropped beans. To make good yield, early growth of doublecropped soybean is very important. The purpose of this experiment was to determine wheat straw leachate, wheat straw management, and supplemental N effects on soybean germination, growth, and yield. Leachate concentrations of 0, 20, and 100 g L−1 (straw to deionized water) were used for germination and radicle growth studies. Leachate concentrations of 0, 2, and 20 g L−1 were used in sand culture and the Ap horizon of Okolona silty clay (fine, montorillonitic, thermic Typic Chromudert) to study germination and early growth of soybean. A 3‐yr experiment on Okolona silty clay, consisting of six management practices and two N levels (0 and 28 kg ha−1), was used to study soybean growth and yield in the field. Management practices consisted of monocropped soybean planted near the optimum date and at the doublecropped date and doublecropped soybean planted where wheat straw was either burned, physically removed, soil‐incorporated, or left standing. Germination was not significantly affected by leachate but was reduced by late planting in the field. The 100 g L−1 leachate inhibited radicle growth, while 20 g initially inhibited but then stimulated radicle growth. The 20 g L−1 leachate inhibited early growth in the laboratory but only in the silty clay, while the 2 g L−1 leachate stimulated growth, especially in the sand. Wheat straw inhibited growth and yield in the field. Supplemental N was most effective in overcoming depressed growth and yield where straw was left on the soil surface. Early monocropped soybean produced the largest average yield, but doublecropped soybean where straw was burned produced the greatest economic returns.
Growth Curve Analysis of Temperature‐Dependent Phenology Models1
Authors: Eskridge K. M. , Stevens E. J.
Published: July 2010

Much of the recent crop phenology research has involved estimation and comparison of crop growth curves for different treatments as a function of growing degree days. Usually, experimental units are set out in a certain type of design and repeatedly measured with approximately equal growing‐degree‐day intervals between measurements. The experiment is then analyzed as a split plot in time or as a repeated‐measures multivariate analysis of variance (MANOVA). However, the assumptions underlying the analysis as a split plot in time require (i) homogeneity of error variance among growing‐degree‐day levels and (ii) identical correlations between measurements for any two periods. Both assumptions are unrealistic when considering plant growth. Also, the MANOVA requires more degrees of freedom for error than growing‐degree‐day levels, which may not hold when a large number of repeated measurements are made on each experimental unit. Growth curve analysis is useful when the split plot in time is inappropriate and a MANOVA is not possible. Growth curve analysis is carried out by fitting a polynomial regression of stage of plant growth on growing degree days for each experimental unit and performing a MANOVA on the resulting regression coefficients. Growth curve analysis is applied to a crop phenology field experiment in Zea mays L. to (i) develop temperature‐dependent phenology models, (ii) test for coincidence of such models across treatments, and (iii) estimate confidence intervals for the final growth curves. It is concluded that growth curve analysis is a useful method in crop phenology modeling because the technique explicitly specifies the shape of the response profile, uses experimental information more efficiently, and is applicable to any type of experimental design.
Effects of Controlled‐Traffic on Soil Physical Properties and Crop Rooting
Authors: Gerik T. J. , Morrison J. E. , Chichester F. W.
Published: July 2010

Soil structural deterioration from wheel compaction can adversely affect crop development and root growth. This study was conducted to determine the effect of controlled‐traffic lanes on soil physical properties and crop rooting for no‐tillage and conventional tillage cropping systems on a swelling clay soil. Sorghum [Sorghum bicolor (L.) Moench], cotton (Gossypium hirsutum L.), and wheat (Triticum aestivum L.) were field grown over 3 yr on an Austin silty‐clay (fine‐silty, carbonatic, thermic Entic Haplustolls). Soil physical properties, including soil strength, bulk density, and total porosity, were not different between tillage treatments in the non‐trafficked area during the crop growing season, but soil strength and bulk density were higher in the traffic lane of the no‐tillage as compared to the conventional tillage treatments. Soil compaction in the traffic lanes was confined to the top 0.15‐m soil layer and did not restrict root development in early stages of crop development. Root densities were lower in the top soil layer of the no‐till traffic lane compared to the non‐trafficked area at harvest, but were representative of values reported for these crops in the literature under conventional management practice. At depths > 0.3 m, root density was not affected by crop species, tillage, or traffic. Although controlled‐traffic has been reported to improve soil physical properties and crop rooting, our data suggest it may not necessarily apply to all soils, especially soils with 40% or more 2:1 clay minerals. Soil moisture and nutrients under traffic lanes will be available to crops.
Nutrient Relations and Productivity of Prickly Pear Cacti1
Authors: Nobel Park S. , Russell Charles E. , Felker Peter , Medina Jorge Galo , Acuña Enrique
Published: July 2010

Prickly pear cacti (Opuntia spp.) are widely used for cattle forage and fodder as well as human food, but their nutrient responses have received little attention. Therefore, soil levels of 13 elements were compared with growth over a 3‐yr period for Opuntia engelmannii Salm‐Dyck and O. rustrera Weber at 11 sites in Coahuila, Mexico. Also, various levels of N and P were applied to O. engelmannii growing for 1.5 yr at Kingsville, TX. The tenfold differences in growth at the Mexican sites were not correlated with soil element level, except for N (r2=0.44; P<0.05) and B (r2=0.64; P<0.01); 84% of the site‐to‐site variation in productivity could be accounted for by these two elements. Fertilizer studies in Texas showed that dryweight gain could be increased 73% by 160 kg N ha−1 and 48% by 80 kg P ha−1 compared to controls without N or P applications (P< 0.01 in both cases), and that some N ✕ P interaction occurred. Cladodes from the control plots in Texas had 21.1 g N kg−1 and 1.97 g P kg−1, which was at least twofold higher than for the Mexican sites, and 23 mg B kg−1, which was over fivefold higher than the average for the Mexican sites. Thus, N, P, and possibly B fertilization can increase the growth of these cacti, which can achieve a relatively high dry weight productivity of about 15 Mg ha−1 yr−1 in semiarid areas without irrigation
Seeding Rate and Row Spacing Effects on Yield and Yield Components of Drill‐Seeded Rice1
Authors: Jones D. B. , Snyder G. H.
Published: July 2010

Although plant population effects on crop performance have been thoroughly investigated in transplanted rice (Oryza sativa L.), less information is available for drill‐seeded rice. Previous studies evaluating the response of rice cultivars to various seeding rates and row spacings were performed before semi‐dwarf cultivars were available in areas where drill‐seeding is practiced. Two contrasting plant types, tall (cv. Lebonnet) and semi‐dwarf (cv. Bellemont and Lemont), were drill‐seeded at rates of 50, 100, and 150 kg seed ha−1 in 0.15‐, 0.20‐, and 0.25‐m row spacings in three tests conducted on an organic soil. Narrow row spacings increased grain yield for both plant types when reproductive growth occurred during a period of relatively high solar radiation and moderate temperatures. Increased seeding rates increased panicles per square meter in all tests for both plant types. This increase was compensated for by decreased filled grain number per panicle, resulting in no significant yield differences among seeding rates. It appears that seeding rates of 80 to 100 kg ha−1 are sufficient to obtain optimum stands in southern Florida.
Dry Matter, Nitrogen, Phosphorus, and Potassium Accumulation Rates by Corn on Norfolk Loamy Sand1
Authors: Karlen D. L. , Sadler E. J. , Camp C. R.
Published: July 2010

The maximum amount and rate of nutrient accumulation by irrigated corn (Zea mays L.) must be known so that farmers do not waste money or pollute water resources by applying excessive amounts of fertilizer. Aerial whole plant samples were therefore collected from irrigated field experiments conducted on Norfolk (Typic Paleudults) loamy sand in 1980, 1981, and 1982, to determine seasonal dry matter, N, P, and K accumulations for corn yielding 10 Mg ha−1 or more in the southeastern Coastal Plain. Rates of accumulation were derived by differentiating compound cubic polynomial equations that described seasonal accumulation patterns. Total dry matter accumulation averaged 23.1 and 24.9 Mg ha−1 for two population treatments that averaged 7 ✕ l04 or 10 ✕ l04 plants ha−1. Aerial N, P, and K accumulation respectively averaged 228, 58, and 258 kg ha−1 in 1980; 264, 37, and 372 kg ha−1 in 1981; and 225,37, and 335 kg ha−1 in 1982. Grain yields averaged 13.4, 11.7, and 10.9 Mg ha−1 in 1980, 1981, and 1982, respectively. Lower P accumulations in 1981 and 1982 were the result of lower grain yields that were apparently caused by excessive K accumulation. Calculated peak dry matter, N, P, and K accumulation rates were 650, 10, 1.6, and 28 kg ha−1 day−1 in this study, compared to rates of 247, 4.5, 0.6, and 3.2 kg ha−1, respectively, in previous midwestern studies. Peak accumulation rates during both vegetative and reproductive growth stages emphasize that cultural, nutrient, and water management practices must be coordinated to provide a minimum stress production environment for high corn yield.
Increasing Importance and Control of Mayweed Chamomile in Forage Crops1
Authors: Smith A. E.
Published: July 2010

Mayweed chamomile (Anthemis cotula L.) is a cool‐season annual weed that germinates during March and matures by mid‐May in the southeastern United States. The economic importance of this weed in the pasture ecosystem has not been determined. The objectives of this study were: (i) to determine the forage quality of mayweed chamomile foliage; (ii) to survey the potential allelopathic influence of mayweed chamomile tissue extract on the development of certain forage species; and (iii) to evaluate herbicides for the control of this weed. The in vitro dry matter digestibility of mayweed chamomile ranged from 630 to 790 g kg−1, with the highest values residing in foliage harvested during the vegetative stage of plant development. Results of laboratory bioassays and growth chamber experiments indicated that water extracts of mayweed chamomile leaf material are potentially allelopathic to alfalfa (Medicago sativa L.) and Italian ryegrass (Lolium multiflorum Lam.) seedlings. Leaf tissue mixed in potting soil significantly reduced alfalfa and Italian ryegrass plant development. The extract and tissue concentrations used in this research were estimated to be similar to concentrations expected to occur within the pasture ecosystem. Paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) at 0.6 kg a.i. ha−1 and glyphosate [N‐(phosphonomethyl) glycine] at 1.2 and 2.4 kg a.i. ha−1 controlled mayweed chamomile in sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] and bermudagrass [Cynodon dactylon (L.) Pers.] forage systems.
Effect of Soil pH on Crop Yield in Northern Idaho1
Authors: Mahler R. L. , McDole R. E.
Published: July 2010

Heavy application of ammonium‐based N fertilizers on cereal crops has resulted in the acidification of soils in northern Idaho. The objective of this 5‐yr study initiated in 1981 was to determine the effect of soil pH on the yield of lentil (Lens culinaris, cv. Tekoa and Chilean), spring pea (Pisum sativum, cv. Columbia and Alaska), winter wheat (Triticum aestivum, cv. Daws, Hill 81, and Stephens), and spring barley (Hordeum vulgare, cv. Advance and Steptoe). Data were compiled from 39 field studies conducted on Mollisols and Alfisols to produce mathematical models to describe soil pH‐yield relationships. Linear‐plateau regression models consisting of intersecting straight lines were fitted to percent maximum yield data for each crop or crop cultivar. The point where the two lines intersected was called the minimum acceptable pH for maximum yield. Lentil and pea were least tolerant to acid conditions, with minimum acceptable pH values required for maximum yields of 5.65 and 5.52, respectively. Cereals were more tolerant, with a minimum acceptable pH value of 5.23 for spring barley. The three winter wheat cultivars reacted differently to soil pH, as Daws, Hill 81, and Stephens had minimum acceptable pH values of 5.19,5.37, respectively. Even though Hill 81 did not have the lowest minimum acceptable pH value, it was considered the most acid‐tolerant winter wheat cultivar because the slope of the line describing the relationship between pH and yield in the limiting region was less than those of the other two cultivars.
Soil Coring Machine for Microplots and Large Soil Cores1
Authors: Swallow C. W. , Kissel D. E. , Owensby C. E.
Published: July 2010

A self‐contained, hydraulically operated soil coring machine was constructed that can push large open‐ended cylinders or boxes into the soil to establish microplots or obtain large soil cores. This machine reduces the time required to create microplots by inserting open‐ended tubes into the soil profile with minimum disturbance to surrounding areas. The equipment is mounted on two wheels and can be towed across the plot area by any small vehicle. The machine has been successfully used to establish undisturbed microplots up to 760 mm in diameter by pushing cylinders up to 1 m deep into the soil. This machine can also remove soil cores of 250 mm in diameter and 900 mm deep from the soil profile.
Asymptotic and Parabolic Yield and Linear Nutrient Content Responses to Rice Population Density1
Authors: Counce Paul A.
Published: July 2010

Knowledge of optimum rice (Oryza saliva L.) population densities and the response of rice nutrient status to population density is necessary for rice producers and researchers to achieve maximum productivity. The objectives of this study were to determine (i) the responses of rice yield to population, (ii) critical populations for experiments with asymptotic yield responses to population, (iii) optimum populations for experiments with parabolic yield responses to population, and (iv) Y‐leaf (youngest mature rice leaf of a plant) nutrient content responses to population. Seeding rates were used to obtain broad ranges of populations over 2 yr for three rice cultivars at three Arkansas locations. Asymptotic and parabolic area yield equations were determined for area yield and population data. In 11 experiments, asymptotic yield responses to population were found; in five experiments, parabolic yield responses were found; in three experiments, linear responses were found; and in three experiments there was no significant relationship between yield and population. Critical and optimum populations were 87 to 308 plants m−2, with most in the range of 159 to 270 plants m−2. In some experiments, the effects of population on N, P, K, and Fe contents were negative. The effect of population was positive for Mn in six of 14 experiments. Reductions in yield at excessive populations appeared to be associated with population‐dependent stresses such as water deficits, disease, and nutrient deficiencies.
Effect of Subsoiling a Compacted Clay Loam Soil on Growth, Yield, and Yield Components of Wheat1
Authors: Oussible Mohamed , Crookston R. Kent
Published: July 2010

Over the past three decades, soil compaction, especially of subsurface horizons, has become a serious problem in irrigated areas of Morocco. This study was designed to determine if subsurface compaction of a clay loam soil in Morocco could be effectively alleviated by subsoiling–to the extent that grain yields of wheat (Triticum aestivum L.) would be improved. A second objective was to document the nature of any resulting yield improvement in terms of changes in root and shoot growth, as well as in the standard components of grain yield. Field experiments were conducted in 1983 and 1984. A single‐tooth subsoiler was pulled through the soil at 0.4‐m intervals, to a depth of 0.7 m. Within the zone through which the tooth passed, soil bulk density was reduced by 11%, while soil porosity and air‐filled porosity were increased by 17 and 50%, respectively. Soil mechanical resistance of subsoiled plots was decreased by 19 to 33% at the 0.2‐ to 0.35‐m depth. At this same depth, roots were 54% longer per unit weight in subsoiled plots. Throughout the growing season, plants grown on subsoiled plots were consistently and significantly taller. These taller plants had more reproductive shoots, each with more and larger kernels. This resulted in an average yield increase of 48% for grain, and 28% for straw.
Herbage Intake Rates of Beef Cattle Grazing Alfalfa1
Authors: Dougherty C. T. , Bradley N. W. , Cornelius P. L. , Lauriault L. M.
Published: July 2010

Alfalfa (Medicago sativa L.), a forage crop unique in that it has high potential in terms of both yield and quality, has considerable capacity for animal production when grazed under management that is based on its growth and development. Two grazing experiments, using balanced change‐over designs, were set up to measure the ingestive behavior of beef heifers (Bos taurus) during the first, second, and third hours of grazing sessions on alfalfa pastures established on Maury silt loam (fine, mixed, mesic Typic Paleudalfs). In Exp. I where the herbage mass, in terms of dry matter (DM), was 3.06 Mg ha−1 and the herbage DM allowance was 6.1 kg h−1 per heifer, animals ingested DM at 2.96, 1.88, and 1.56 kg h−1 during their first, second, and third hours of grazing, respectively. The mean rates of biting were 26, 21, and 19 bites min−1 for the same periods. Herbage DM intake per bite declined linearly from 1.96 to 1.54 to 1.36 g for each hour increment in grazing time. Forage utilization was 51, 32, and 27% for the same increments. In Exp. II where the herbage mass (DM) was 1.74 Mg ha−1 and the allowance was 3.4 kg h−1, heifers ingested 2.35, 1.47, and 1.20 kg h−1 during their first, second, and third hours of grazing, respectively. The mean rates of biting were 34, 22, and 18 bites min−1 during the same periods within the grazing session. Herbage DM intake per bite averaged 1.17 g and did not vary within the grazing session. Forage utilization was 75, 47, and 37% during the three consecutive hours within the grazing session. Maximum rates of herbage intake were characterized by larger bites and relatively slow rates of biting. Rates of herbage intake were considerably higher during the first hour of grazing than during the second and third hours. In a 3‐h grazing session, animals consumed 47, 29, and 24% of their intake during the first, second, and third hours, respectively.
Animal Evaluation of Forages Following Several Methods of Field Renovation1
Authors: Koch D. W. , Holter J. B. , Coates D. M. , Mitchell J. R.
Published: July 2010

Sod‐seeding is the only practical method to introduce improved forage species on many fields. Animal data are needed to adequately evaluate the viability of sod‐seeding. This study determined animal responses to changes in forage composition following several methods of renovation. Two fields with fine, sandy loam soils were used. Bradford Field (Typic Dystrochrepts) was dominated by smooth brome (Bromus inermis L.). Walker Field (Typic Fragiochrepts) was low in fertility and had a diverse sward. Treatments consisted of an N‐fertilized control and sod‐seeding of legumes following either paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) or glyphosate [N‐(phosphonomethyl)glycine] application. Additionally, red clover (Trifolium pratense L.) and timothy (Phleum pratense L.) were seeded conventionally at the Walker site. Nutritive value of three harvests from Bradford Field and one harvest from Walker Field was determined in feeding trials with 250‐kg dairy heifers (Bos primigenius). Greater legume content of renovated swards (avg. 720 g kg−1 the year following seeding) compared to N‐fertilized controls (avg. 230 g kg−1) resulted in greater forage crude protein (CP) content (all four harvests) and greater dry matter (DM) intake (two of four harvests), greater N intake (NI) (all four harvests), and greater body tissue retention of N (three of four harvests) by dairy heifers. Metabolizable and digestible energy were similar for all harvests and improvement methods. There were no differences in animal response to forages from sod and conventional seedings, except that NI was greater from sod‐seedings. The year following seeding, there was an average 48 and 75% increase in digestible DM and CP yield, respectively, from treatments introducing legumes compared to N‐fertilized controls. These results show that when existing species are not highly responsive to N, improved forage species can be seeded without tillage and without N, and result in improved forage quality and animal performance.
Characteristics of Exposed Subsoil—At Exposure and 23 Years Later1
Authors: Eck Harold V.
Published: July 2010

The effects of topsoil removal on subsoil characteristics and productivity are usually studied at or soon after removal, with little attention to changes with time. The objective of this study was to evaluate the effects of 23 yr of exposure on the chemical and physical characteristics and productivity of various layers of Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls). An area on a 1% slope was leveled in 1960, giving plots with 0, 0.10, 0.20, 0.30, and 0.41 m of topsoil removal. The area was cropped to grain sorghum [Sorghum bicolor (L.) Moench] in fertility studies for 6 yr, fallowed for 2 yr, then planted to tall wheatgrass (Agropyron elongatum) and left undisturbed until 1983. The study was then reactivated with grain sorghum being grown without fertilizer 1 yr to determine fertilizer residual effects. In 1984 the previous N fertilizer treatments were reinstituted. During the 23 yr, organic matter (OM) and total N decreased in uncut surface soil but increased in exposed subsoil where initial levels were low. Extractable P levels and particle size distribution remained essentially unchanged. The proportion of large water‐stable aggregates (4.0–12.7 mm) decreased, especially in the surface soil where OM decreased with time. Decreases in large aggregates were accompanied by increases in the 0.25‐ to 1.0‐mm size range. Productivity of exposed subsoil layers increased over time. In relation to yields on similarly treated surface soil, yield reductions from soil removal (avg 0.10, 0.20, 0.30, and 0.41 m) in 1960 to 1962 and 1984 were as follows: unfertilized, 55 and 33%; P fertilized, 52 and 38%; N fertilized, 31 and 16%; N and P fertilized, 2 and 14%. Productivity increases were associated with increases in both N and P supplying capacity.
Particle Size and Soil Texture Effects on Elemental Sulfur Oxidation1
Authors: McCaskill M. R. , Blair Graeme J.
Published: July 2010

Most previous experiments examining factors affecting the conversion of elemental S into plant‐available forms have used indirect methods, such as measuring sulfate accumulation, and have at times resulted in exaggerated estimates of elemental S oxidation rates. Direct measurement of residual elemental S offers a more reliable estimate of conversion rate, but only some of the factors known to affect conversion rate have been investigated by direct methods. A pot experiment was conducted over 238 days to measure conversion rates under a range of elemental S particle sizes (0.1–2.0 mm) and soil textures, and with and without inoculation with sulfur‐oxidizing bacteria. Conversion rates were measured by two indirect methods—S uptake by plants and 35SO4 dilution‐and one direct method—acetone extraction of remaining elemental S. Initial surface area of elemental S was the prime determinant of conversion rate, but three other factors had to be considered to fully explain observed release characteristics. These were (i) a gradual particle disappearance in 0.1‐ and 0.2‐mm particles, which caused a reduction in conversion rate with time, (ii) a depression in conversion rate for particle sizes ≧ 0.4 mm on noninoculated treatments, and (iii) shape considerations that were imputed to the observed lower conversion rates for the more spherical 2.0‐mm size. Three of the four soils—an Arenic Haplustult, a Plinthic Haplustult, and a Typic Torrert—showed increased conversion rates in response to inoculation, with inoculation responses most marked for the larger (> 0.4 mm) particle sizes. The other soil—a Udic Ustochrept—was not responsive to inoculation. No relationship was detected between soil texture and elemental S conversion rate over a range of clay contents from 9 to 52%.
Market Grade Effects on Fatty Acid Composition of Five Peanut Cultivars
Authors: Mozingo R. W. , Coffelt T. A. , Wynne J. C.
Published: July 2010

Peanut (Arachis hypogaea L.) seeds are sized into market grades before processing into manufactured products. Therefore, manufacturers need to consider the effect of market grade and cultivar on fatty acid composition and storage quality. Previous studies have not considered the effect of market grade on oil quality. Sized seed of five Virginia‐type peanut cultivars grown in field plots at the Peanut Belt Research Station in Lewiston, NC, on a Norfolk sandy loam soil (Typic Paleudults), and at the Tidewater Agricultural Experiment Station in Suffolk, VA, on an Eunola loamy fine sand soil (Aquic Hapludults) for 3 yr (1982–1984) were evaluated for fatty acid composition. Seed of ‘NC 7’, ‘VA 81B’, ‘NC 6’, ‘Florigiant’, and ‘GK 3’ were sized into three shelled market grades (extra large, medium, and No. 1) for analysis. Significant differences were observed among cultivars for all fatty acids, oleic/linoleic (O/L) ratio, and computed iodine value. A change in market grades from No. 1 to medium to extra large resulted in a significant increase in the percentage of stearic, oleic, and arachidic acids and a significant decrease in the percentage of palmitic, linoleic, eicosenoic, behenic, and lignoceric acids. Significantly lower computed iodine values and significantly higher O/L ratios were recorded for the larger size seed. Significant environment × cultivar interactions were recorded for iodine value, O/L ratio, and all fatty acids except palmitic and oleic. Environment × market grade interactions were significant for all fatty acids, O/L ratio, and iodine value. Significant cultivar × market grade interactions were obtained for palmitic, oleic, and linoleic acids, iodine value, and O/L ratio. These results show market grade, cultivar, and environment affect fatty acid composition, computed iodine value, and O/L ratio. Larger size seed produced fatty acid distribution, iodine values, and O/L ratios that indicated better stability and longer shelf‐life of the peanut.
Alterations in Plant Growth and Dry Matter Distribution in Soybean
Authors: Egli D. B.
Published: July 2010

The partitioning of assimilate between vegetative and reproductive plant parts of soybean [Glycine max (L.) Merrill] during flowering and fruit set could be related to fruit and seed number, and yield. Experiments were conducted in the field (cv. Cumberland) for 2 yr to investigate the effect of alterations in plant growth on the distribution of dry matter during flowering and fruit set. Alterations in plant growth were created by reducing the insolation (63%) during flowering and fruit set by using commercial shade cloth and by low density plantings (spaced plants, approximate equidistant spacing with 0.9 m between plants). The control and shade treatments were grown in 0.76‐m rows (0.71‐m in 1984), and conventional cultural practices were used. Partitioning ratios (reproductive mass/total biomass) were calculated from four samples collected between R1 and R6. Leaves (uppermost fully expanded leaf and the leaf four nodes below it) were sampled during flowering and fruit set for carbohydrate and N analysis. Shade reduced crop growth rate (R1‐R5), vegetative mass at R5, seed number per square meter, and yield. The spaced plants were much larger and had nearly 80% of their reproductive mass on the branches at R6 compared with 5% for the control plants. Leaf starch and soluble sugar concentrations tended to be reduced by the shade treatment and increased in the spaced plants. There were no treatment effects on leaf N concentration. The treatments had a minimal effect on the partitioning ratios, indicating that distribution of dry matter between vegetative and reproductive plant parts was relatively constant across large differences in plant size and growth rate. This suggests that the fruit and seed numbers may be more closely related to crop growth rate than to the partitioning of assimilate.
Recovery of Anhydrous Ammonia‐Derived Nitrogen‐15 During Three Years of Corn Production in Iowa
Authors: Sanchez C. A. , Blackmer A. M.
Published: July 2010

Studies were conducted at two locations to determine recovery of anhydrous ammonia‐derived 15N applied with and without nitrapyrin [2‐ehloro‐6‐(trichloromethyI) pyridine] during corn (Zea mays L.) production over a 3‐yr period in which N fertilizers were applied annually at rates commonly used in the Corn Belt. The results showed that 13 to 33% of the labeled N was removed from the plots during grain harvest in the first crop after application. Recovery of labeled N in the whole plants ranged from 29 to 45%, but the stover was returned to the plots. Nitrapyrin increased the amount of N recovered in plant tissue at only one of the six site years studied. Only small percentages (0.3‐1.5%) of the labeled N were recovered in the second and third crops after application, and nitrapyrin had negligible effects on amounts of labeled N recovered by these crops. Analysis of soil samples collected 1 yr after application of labeled N showed that 19 to 23% of this N remained in the soil. Only small portions of this N existed as exchangeable ammonium and nitrate. Most of this N was in the KMI‐N (Kjeldahl minus inorganic‐N) fraction, which includes N from both organic matter and nonexchangeable ammonium. Large portions (47‐94% of the labeled N found in the KMI‐N fraction 1 yr after application were still present 3 yr after application. The results of this study show that a substantial portion (49–64% of the labeled N was lost from the surface 1.5 m of soil during the first year by processes other than plant uptake. A probable explanation as to why the losses reported here are greater than those reported from many comparable studies is that our determinations included the amounts of fertilizer N lost during the fall‐tospring period. These losses must be considered when evaluating the long‐term efficiency of N fertilization practices and the effects of these practices on environmental quality.
Root Length Density from Minirhizotron Observations
Authors: Bland William A. , Dugas William A.
Published: July 2010

Root length density (L; cm root/cm3 soil) measurements are important for developing and testing many water extraction equations. Clear tubes buried in the soil (minirhizotrons) allow continuous and nondestructive observations of rooting that may be used to estimate L. In a field experiment, counts of roots at the walls of horizontally installed minirhizotrons were converted to L with L = C × (counts/ area of tube wall), using published theoretical values of C (1.0, 2.0, and 3.3). These calculated values of L were then compared to measurements of L from roots washed from soil samples. For cotton (Gossypium hirsutum L.), C = 2.0 provided the best estimate of L from the minirhizotron counts, and the data were sufficient to reject the C = 1.0 model. For sorghum [Sorghum bicolor (L.) Moench], a simple relationship between minirhizotron counts and measured root length was not found. Verification of a theoretical model for the conversion of minirhizotron observations of cotton roots to root length density increases the utility of the method.
A Comparison of pH Measurements using the Antimony Microelectrode and Glass Electrode
Authors: Conkling B. L. , Blanchar R. W.
Published: July 2010

Microelectrodes are useful for making in situ soil pH measurements. A study was done to compare soil pH measurements made with a standard glass pH electrode with those made using an antimony (Sb) microelectrode. Soil‐water and soil‐water‐citrate systems were prepared using soil samples from various horizons of four Missouri soils, and the pH values of the same samples were measured with glass and Sb microelectrodes. Over all soils, the average difference between pH measurements made with the Sb and the glass electrodes in the soil‐water system was 0.36 pH units. In the soil‐water‐citrate system, pH measured with the Sb electrode was consistently higher than pH measured with the glass electrode, and the average difference was 0.64 pH units.
Productivity and Water Use of Proso Millet Grown under Three Crop Rotations in the Central Great Plains
Authors: Shanahan J. F. , Anderson R. L. , Greb B. W.
Published: July 2010

Proso millet (Panicum miliaceum L.) is a shallow‐rooted, short‐season summer annual that is well adapted to the semiarid conditions of the western Central Great Plains. However, cropping systems for proso millet have not been well established in this region. Three proso millet cultivars were grown under three crop rotations, millet‐millet (M‐M), winter wheat (Triticum aestivum L.) ‐millet (W‐M) and fallow‐millet (F‐M), for five growing seasons (1973–1977) to determine water use and productivity of the second component (proso millet) in each rotation. The research was conducted on a mesic Pachic Argiustoll soil at the Central Great Plains Research Station located near Akron, CO. Precipitation during the noncropped period for the W‐M and F‐M averaged 26 and 145% more, respectively, than the M‐M rotation. The W‐M and F‐M rotations exhibited 7 and 19% more seasonal crop water use, respectively, than the M‐M sequence over the 5‐yr period of the study. These differences in water use resulted in the W‐M and F‐M rotations producing 38 and 75% more total dry matter and 50 and 116% more grain yield, respectively, than the M‐M sequence. The three cultivars responded similarly to the three crop rotations. Since grain yields were low and variable for the M‐M rotation and the noncropped period was quite long (86 wk) and inefficient in soil water storage for the F‐M rotation, the W‐M rotation appears to be the most efficient rotation of the three rotations evaluated for producing proso millet in this region.