bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Soil Mineral N Levels and Inoculation on Nodulation, Nitrogenase Activity, and Grain Yield of Pigeon Pea1
Authors: Quilt P. , Dalal R. C.
Published: July 2010

Since pigeon pea [Cajanus cajan L. (Millsp.)] has a considerable potential as a tropical legume, intensive research in the Caribbean is being undertaken with a view to increase production. There is a scarcity of information on the effectiveness of Rhizobium of the pigeon pea to fix atmospheric N and to meet the N needs of the crop. Moreover, conflicting results have been reported on the effect of fertilizer N on grain yield, presumably because of variable mineral N levels in soil. Therefore the present investigation was designed to study the effect of changes in soil mineral N levels (brought about initially by incorporation of coconut fibre and bagasse with soil at the rate of 25 metric tons/ha each) and five Rhizobium strains (two local, UWI 10004 and UWI 10013, and three exotic, iCPE(a), CB756 and CIAM/1001) on nodulation, nitrogenase activity and grain yield of the crop. Greenhouse and field experiments were conducted on a River Estate Loam, a fluventic eutropept, at the University Field Station, Trinidad. The results showed that the incorporation of coconut fibre and begasse reduced soil mineral N levels through immobilization and led to early nodule formation and nitrogenase activity. Although the incorporation of coconut fibre increased plant shoot weight after 14 weeks growth, that of bagasse immobilized so much mineral N (from initial level of 50 ppm N to 6 ppm N at 7 weeks after application) that plants were N starved. The dry pod yield was increased by all Rhizobium strains. However the grain yield was significantly increased by the exotic strains, iCPE(a) and CIAM/1001. Thus, by manipulating soil mineral N levels and by using effective Rhizobium strains, the pigeon pea grain yields can be increased.
Influence of Supplemental Irrigation and Pre‐Sowing Soil Water Storage on Wheat1
Authors: Singh N. T. , Singh Rachhpal , Mahajan P. S. , Vig A. C.
Published: July 2010

Water stress at certain physiological stages of growth reduces crop yields. The magnitude of water stress and the associated plant response depend upon the initial water content of the soil profile and the timing of additional input of water. A study was conducted to find out the influence of pre‐sowing profile water storage and the timing of supplemental irrigation on wheat (Triticum aestium L.) grown on Fatehpur loamy sand, a Typic Ustochrept. The storage levels were 25, 30, and 35 cm water in the 180 cm profile corresponding to approximately 15, 20, and 25‐cm of available water. The supplemental irrigation was applied at crown root initiation, boot, and grain development stages. Plant height, leaf area index, and number of tillers significantly increased with increase in the amount of profile stored water. The average grain yield increased from 26.1 to 33.1 q/ha when initial water storage increased from 25 to 35 cm. The increase in grain yield between the 25 and 30 cm storage levels was 0.80 q/ha per cm of additional storage, but with further increase in storage level from 30 cm to 35 cm, the increase per cm of additional water declined to 0.60 q/ha. The surface soil at crown root initiation dried to a water content of about 5%. The supplemental irrigation applied at this stage resulted in a maximum grain yield of 36.4 q/ha. Water use increased with increase in initial water storage in the soil and with the earliness of supplemental irrigation. Water use efficiency increased from 28.9 to 34.5 kg/ha per an water with an increase in the initial profile stored water from 25 to 35 cm. This study shows that in soils with water storage around 20 cm/m and substantial loss of soil water occurring early in the season, maximum yield of wheat is obtained when a supplemental irrigation is applied at the crown root initiation stage.
Seasonal Changes in Organic Acids, Water‐Soluble Carbohydrates, and Neutral Detergent Fiber in Tall Fescue Forage as Influenced by N and K Fertilization1
Authors: Hannaway David B. , Reynolds John H.
Published: July 2010

The seasonal trends of the major energy‐supplying constituents in tall fescue (Festuca arundinacea Schreb.) affect performance of beef cattle in the southeastern U. S. since this grass is usually grazed nearly year‐round.

Concern has been expressed about the effect of fertilization on tall fescue that would be grazed during the late winter and early spring when incidence of grass tetany is highest. The objective of this research was to determine the effect of N and K fertilization on three major organic constituents: organic acids, water‐soluble carbohydrates (WSC), and neutral detergent fiber (NDF) in tall fescue. The seasonal trends of these constituents were evaluated in relation to the eriod of incidence of grass tetany in the late winter and early spring, and to seasonal forage quality. Forage was sampled monthly in two 1‐year field experiments near Knoxville, Tennessee, on a thermic, Typic Paleudults soil. The freeze‐dried forage was analyzed for ash alkalinity, an estimate of total organic acids, as well as for WSC and NDF. Fertilization treatments reported are 0 and 112 kg N/ha for the first year and 0 and 168 kg K/ha for the second year. In the first year, N generally increased organic acids but in the second year, K generally decreased them. The most pronounced peaks for organic acids were in spring and summer. The seasonal change in organic acids did not appear to be enough to influence incidence of grass tetany. Nitrogen and K fertilization effects on WSC and NDF generally were not significant. Peaks of WSC occurred in early spring and fall with levels generally higher in the cooler months. The peak of NDF coincided with stemmy material in May. Levels of NDF were generally higher in the warmer months. Highly significant negative correlations between WSC and NDF in both years were the most salient relationships found. These negative correlations are probably the reason for the general impression that fast‐growing fescue forage is associated with incidence of grass tetany. The months with high NDF and low WSC were those in which tall fescue digestibility is usually lowest. The benefit from increased yields with N fertilization would have to be considered in relation to the possible increased incidence of tetany from increased N, K, and organic acid levels.
Growth of Subterranean Clover in a Range Soil as Affected by Microclimate and Phosphorus Availability. III. Comparative Growth of Subterranean and Rose Clovers at Cold Soil Temperatures1
Authors: Raguse Charles A. , Taggard Kenneth L.
Published: July 2010

The biological yield potential of winter annual range legumes is influenced by the timing of rainfall adequate to ensure germination. If rains are late, the establishment phase of growth must occur at cold soil and air temperatures. On low‐P soils, this combination of abiotic factor constraints can limit symbiotic N fixation.

We conducted three controlled‐environment experiments to compare the seedling growth of rose clover (Trifolium hirtum All., ‘Hykon’) and subterranean clover (T subterrateum L., ‘Mt. Barker’, hereafter referred to as subclover) on a P‐deficient soil (Sobrante‐Las Posas association), simulating winter conditions of cold soils and low light. Comparative growth responses, especially intraplant dry matter partitioning and nodulation, were observed for several soil P availability levels.

A sunlit phytotron provided a common shoot environment of seasonal (fall/winter) ambient light intensity and photoperiod, with a programmed smooth diurnal temperature cycle of 20 C maximum and 5 C minimum. Three independently‐controlled water baths maintained soil temperature experiments at a constant 5 C, a constant 10 C, and a diurnal 5 C to 10 C alternation. Phosphorus levels were 0, 45, 90, and 180 kg/ha equivalents. Growth intervals (5 ± 0.5 trifoliolate‐leaf stage), varied between 58 and 114 days.

Leaf area of subclover was greater than that of rose clover, and responded more to increasing P levels. Leaf areas tended to increase with higher soil temperatures. Nodule weight was positively correlated with leaf area; nodule weight:leaf area regressions suggested that nodule development was adequate at 5 C and that nodule development was primarily related to time rather than to morphological development of the shoot. Nodule weights were similar for the two species, and low at 0 P.

The results suggest that while the practical soil threshold temperature for overall growth is near 5 C, some intraplant growth processes may proceed, but only at adequate, availability levels of mineral nutrients. These relationships may be particularly important where range annual legumes are being introduced as part of a more general range improvement program.
Effects of Premature Defoliation and Plant Kill on Germination of Cottonseed1
Authors: Minton Earl B. , Wanjura D. F. , Bilbro J. D.
Published: July 2010

Performance data on cottonseed (Gossypium hirsutum L.) harvested from plants following premature defoliation and premature plant kill are limited. The objective of this study was to determine the effects of premature defoliation following adverse weather, hand defoliation, and premature plant kill (plants cut off at the soil line and dried rapidly in the greenhouse) at different dates in the fall on germination of cottonseed. The seed were stored for several weeks in the laboratory at about 30% relative humidity and 21 C before they were germinated at alternating 20 to 30 C and at a constant 18 C. Means for germination percentage, germination rate index (GRI), and coefficient of velocity of germination (CVG) were separated by Duncan's multiple range test. Reduced germination and GRI were obtained with seed harvest from plants that set fruiting following late season irrigation, premature defoliation following low temperatures, leaf removal by hand, and prematurely killed in September. Premature plant kill in October increased germination when compared to 50 and 100% leaf removal by hand and the check (no leaves removed). Germination was similar for seed harvested from plants with 50% leaf removal and the check. Removal of all leaves had the most adverse effect on the performance of cottonseed. The lowest CVG was obtained from plants left intact in the field. Seed from a determinant cultivar appeared to be affected less than seed from an indeterminant one.
Relative Effectiveness of Several Mn Sources on Virginia‐Type Peanuts1
Authors: Hallock D. L.
Published: July 2010

Recently, Virginia farmers have experienced more cases of Mn deficiency in peanuts (Arachis hypogaea L.). More information was needed concerning the relative effectiveness of various commercial sources of Mn and methods of application on peanuts. Several sources of Mn were sprayed, broadcast, or banded on peanuts in 1975 and 1977 under conditions where considerable chlorosis typical of Mn deficiency was prevalent both years in a sandy Aquic Hapludult, pH 6.5.

Peanut yields in 1975 averaged 3,915 kg/ha where sources of Mn were sprayed on foliage. Soil‐applied (band or broadcast) sources averaged 3,385 kg/ha. Check plot yield was 2,620 kg/ha. Highest yields were obtained from the Sequestrene treatment (Chelate, 0.45 kg/ha Mn) followed closely by the Manzate 200 (C4H6MnN2S4, 1.1 kg/ha Mn) Sorba‐Spray Mn (MnSO4, 0.19 kg/ha Mn) and Manganese sulfate treatments (3.36 kg/ha Mn), each sprayed three times except Manzate (4 sprays). Five other products where the Mn source was either MnSO4, MnO, or both also were included.

Sources in 1977 included only Man‐Gro (MnSO4), Manganese sulfate, and Dithane M‐45 (C4H6MnN2S4), but combination treatments with Mn banded on the row and sprayed on foliage were included. Average yields obtained from soil‐only (broadcast or banded), combination soil and foliar, and foliar‐only treatments were 2,640 kg/ha, 2,720 kg/ha, and 2,820 kg/ha, respectively. The check plot yielded 2,035 kg/ha. Highest yields were obtained from 4.48 kg/ha of Mn as MnSO4 in three sprays (2.24 kg/ha in first spray), whereas the yield from a broadcast treatment (44.8 kg/ha) of Mn was nearly as high. Drought probably limited yield potentials particularly in 1977.
Corn Response to Foliar Application of Dinoseb1
Authors: Hicks D. R. , Lueschen W. E. , Ford J. H. , Nelson W. W. , Overdahl C. J. , Evans S. D. , Peterson R. H.
Published: July 2010

Foliar application of dinoseb (2‐sec‐butyl‐4‐.6‐dinitro phenol) has been reported to increase the grain yield of corn (Zea mays L.) The objective of our work was to evaluate the response of dent corn hybrids adapted to the northern region of the Corn Belt to foliar applications of dinoseb. Several rates of dinoseb were evaluated on corn grown at two locations for 4 years.

Dinoseb with a surfactant was applied as a foliar spray at the rate of 190 to 238 liters/ha. In 1974–73, dinoseb rates evaluated ranged from 0 to 70 g a.i./ha and were applied 2 weeks prior to tassel ing. 1974–73 one rate (12.5 g a.i./ha) of dinoseb was applied when the unemerged tassel was 1.3 or 17.8 cm in length. Three hybrids of differing maturity were planted on two dates for the test. Grain yield and ear or kernel moisture percentages were determined for all experiments. Tasseling and silking dates, test weight, barrenness, and 100‐kernel weight were recorded in some experiments.

In general, grain yields were not statistically affected by dinoseb foliar application. Yield differences were small and in many cases the numerical difference between dinoseb treated and nontreated plots was negative. Percent moisture at harvest, tasseling and silking dates, kernel test weight, 100‐kernel weight, and barrenness were not statistically affected by foliar application of dinoseb. The lack of a significant yield increase, the low mean response, and the inconsistent response do not support foliar application of dinoseb to enhance corn grain yield.
Physiological Maturity in Soybean1
Authors: TeKrony D. M. , Egli D. B. , Balles J. , Pfeiffer T. , Fellows R. J.
Published: July 2010

A visual indicator of physiological maturity (maximum dry seed weight) in soybean [Glycine max (L.) Merrill] would be useful to researchers and soybean producers. Experiments were conducted utilizing two cultivars in the greenhouse and six cultivars in the field to characterize the color of soybean seeds and pods at physiological maturity. In greenhouse experiments where plants were exposed to 14CO2 as they neared maturity, it was found that the 14C content of the seed decreased as the yellow coloration of the seed coat increased. Practically no 14CO2 was recovered from yellow seeds, regardless of the color of the pod, suggesting that the seed stops importing assimilates and is physiologically mature when it is completely yellow (free of green color). Normally, yellow seeds were found only in yellow or brown pods. The respiration rate of seed, measured as CO2 evolution, declined rapidly as the seedcoat began to turn yellow and reached a low level when the seed were completely yellow at a seed moisture content of 55 to 60%.

Physiological maturity of an entire plant, estimated from dry seed weight data in the field, occurred when 26% of the seed were yellow and 35% of the pods were yellow or brown. The seed moisture content ranged from 54 to 62%. The date of physiological maturity estimated in the field was slightly early in comparison to complete physiological maturity (all seed completely yellow) due to the sampling variation associated with estimating dry seed weight and the variation in pod maturity on an individual plant.

The data suggest that the occurrence on the main stem of one normally colored mature pod per plant represents a useful and acceptable indicator of physiological maturity, even though all the pods or seed were not completely yellow at this stage of development.
Dry Weight and Leaf Area Production Rates of Irrigated Determinate Soybeans1
Authors: Scott H. D. , Batchelor J. T.
Published: July 2010

Quantitative measurements are needed to determine the effects of irrigation on production rates of dry matter and leaf area of soybeans [Glycine max. (L.) Merr.]. A field experiment was conducted on a Typic Albaqualf (Crowley silt loam) and a Vertic Fluvaquent (Kobel clay) for three seasons. The objectives were to evaluate dry matter and leaf area production and to use growth analysis techniques to quantify these growth rates for irrigated (I) and nonirrigated (N) soybeans. Growth analysis parameters computed include crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR), leaf weight ratio (LWR), and specific leaf area (SLA). Little or no plant response to irrigation was found during the wetter than normal season in 1974. Differences in plant growth due to soil moisture regime were obtained in the two dry seasons (1975 and 1976). These differences initially were found during late vegetation and early bloom growth stages in both leaves and stems on or near the same date. Generally, the irrigated soybeans accumulated greater amounts of dry matter and leaf area and had higher seed yields than did the nonirrigated soybeans.

Values of crop growth rate for I and N soybeans increased to a maximum during late July and early August of 1974 and declined thereafter. Similar results were found with the I soybeans in 1975. The period of maximum CGR corresponded to late vegetative and early reproductive growth. The maximum CGR of the N soybeans was found at mid‐August during 1975, the season when rainfall deficits were observed. This period of maximum CGR corresponded to mid‐podfill growth stages.

Values of relative growth rate, net assimilation rate and leaf area ratio were highest during early vegetative growth and decreased as the season progressed. Generally, in a given year the I soybeans had greater values of the growth parameters during reproductive stages. The decline of LAR of the N soybeans during 1975 was attributed to the decrease in leaf weight ratio during vegetative growth and to the decrease in both LWR and specific leaf area during reproductive growth. The greater LAR values of the I soybeans during reproductive growth was due to the longer period during which the assimilates were converted to leaf area production.
Elongation of Wheat Leaves Exposed to Several Levels of Matric Potential and NaC1‐Induced Osmotic Potential of Soil Water1
Authors: Sepaskhah A. R. , Boersma L.
Published: July 2010

Leaf elongation is a major indicator of plant growth. It is partly controlled by turgor potential which, in turn, is affected by soil water potential and/or by the osmotic potential of the soil water. This study was conducted to determine the interaction of osmotic potential of Soil water induced by NaCl (0, −4, −8, and −12 bars) and soil matric potential induced by carbowax 4000 (−0.3, −2.5, −5.0, and −7.5 bars) on the turgor potential and elongation rate of leaves of 2‐week‐old wheat seedlings (Triticum aestivum L.). Relationships between rate of leaf elongation and leaf turgor potential and rate of leaf elongation and leaf water potential at all combinations of the experimental variables were obtained. Seedlings of spring wheat (Triticum aestivum L. ‘Fielder’) were grown in a Xerollic Durargids loam soil separated from the surrounding nutrient solution by a semipermeable cellulose‐acetate membrane. The rate of leaf elongation of the 2‐week‐old plants, growing in a walk‐in growth room, was measured at 24‐hour intervals with a ruler. Turgor potential of leaves was obtained as the difference between leaf water potential measured with a pressure chamber apparatus and osmotic potential of leaf cells measured with a thermocouple psychrometer.

At the matric potential of −0.3 bars, where cell dehydration does not occur, accumulation of salt in the leaves at osmotic potentials of −4, −8, and −12 bars appeared to increase the turgor potential of leaf cells. Under moderately low to very low soil water potentials of −2.5 to −7.5 bars combined with low osmotic potentials of the soil water, leaf water potential decreased more strongly than could be counteracted by osmoregulation through a decrease in the osmotic potential of the cell; consequently, the turgor potential decreased as the osmotic potential of soil water decreased. We found significantly different linear relationships between rate of leaf elongation and turgor potential and between rate of leaf elongation and leaf water potential at the experimental osmotic potentials of the soil water. The “gross extensibility” and threshold turgor potential of the leaves were different at the various osmotic potentials of the soil water, ranging from 5.29 to 2.01 μm/min‐bar and from +0.33 to +1.33 bars, respectively. The rates of leaf elongation decreased at an accelerated rate as the osmotic potential of the soil water decreased. Leaf elongation ceased at leaf water potentials of −18.2, −20.7, −24.4, and −29.7 bars at osmotic potentials of the soil water of 0, −4, −8, and −12, respectively. The toxic effects of NaCl on metabolic processes of cell wall extension have been discussed.
Phosphorus Response of Maize Grown on Alfisols of Southern Nigeria1
Authors: Kang B. T. , Osiname O. A.
Published: July 2010

Phosphorus plays an important role for food crop production in the forest zone of tropical Africa but very little information is available on the phosphate requirement for maize production there. Field trials were, therefore, conducted with maize (Zea mays L.) at two locations on Alfisols in southern Nigeria to investigate the P response and the residual effect of applied P. The experimental sites were recently cleared from fallow and the vegetation was removed after land clearing.

On the Egbeda soil (Oxic Paleustalf), which is derived from basement complex rocks, five seasons of maize croppings were done from 1971 to 1973 using a split‐plot design with three replications. Four periods of fresh P applications (major and minor seasons 1971 and major and minor seasons 1972), formed the main plots and each of these fresh P applications consisted of five P rates (0, 26, 52, 78 and 104 kg P/ha) which made up the sub‐plots. Maize culture T2A ✕ TZB was planted at a spacing of 75 ✕ 25 cm (53,300 plants/ha). The minor season maize received supplementary irrigation. On the Alagba soil (Oxic paleustalf) which is derived from sedimentary rocks, five P rates (0, 20, 40, 80, and 160 kg P/ha) were compared using a randomized complete block design with four replications. Phosphate was broadcasted as single superphosphate and incorporated in the soil to the various treatments. The residual effects of applied P were followed up at both locations. With removal of fallow vegetation following land clearing, significant responses to P applications were observed at both locations. The P requirement for obtaining significant yield increases was not very high, ranging from 26 to 52 kg P/ha depending on season and location.

Higher yield response to P was observed during the main season (April to July) than during the minor season (August to November) planting. At both locations significant residual effects of applied P was observed on maize yield and Bray P‐1 soil test levels. On the Egbeda soil it was possible to build up and maintain adequate amounts of extractable P for two to three maize crops with one addition between 52 to 104 kg P/ha.

Good relationship was observed between maize grain yield and Bray P‐1 test values on the Egbeda soil. The critical Bray P‐1 test values was estimated to be about 14 ppm P. Results of incubation studies showed that under laboratory conditions 2.5 to 3 ppm of fertilizer P was required to increase the Bray P‐1 test level by 1 ppm for the Egbeda and Alagba soils respectively. Under field conditions for the Egbeda soil the P rate required was estimated to be 3.5 ppm P.

The critical P in the ear leaf was estimated at 0.3% P. High rate of P application was shown to depress the Zn status in the ear leaf.
Water Balance and Profile Moisture Loss Patterns of an Alfisol1
Authors: Singh Piara , Russell M. B.
Published: July 2010

In order to match the water availability with the crop water requirement in the semi‐arid tropical (SAT) areas of the world, the distribution and magnitude of various water balance components and the moisture dynamics in the soil profile during crop growth periods need to be understood. Since Alfisols (fine, clayey mixed udic Rhodustalf) constitute the major soil group of SAT areas, its water balance and water loss pattern in sorghum (S. bicolor L. Moench) was studied during both the monsoon and post‐monsoon season of 1977 to 1978.

During the monsoon season, water losses as evaporation, transpiration, and drainage constituted 21, 35, and 29%, respectively, of the total seasonal available water (Rainfall + irrigation + profile available water to 127 cm depth). In the post‐monsoon season, the only unproductive loss of water was soil evaporation which formed about one‐fourth of the total seasonal available water. The major amount of moisture depletion during the postmonsoon season was confined to the top 90 cm profile depth.

The data obtained on water balance and the ability of Alfisols to supply water to crops suggest the need for better water management by adopting improved cultural practices, like water harvesting, and improved cropping patterns for optimizing water availability and its use for crop production in the SAT.
Utilization of Labeled‐N Fertilizer by Silage Corn Under Conventional and No‐till Culture1
Authors: Legg J. O. , Stanford George , Bennett O. L.
Published: July 2010

The influence of tillage methods on the utilization of N from soil and fertilizer sources by crops has not been investigated previously by tracer methods to any great extent. The objectives of this study were to compare yields and N utilization of silage corn (Zea mays L.) in conventional and no‐till culture, using a double‐cropping system of corn and smooth bromegrass (Bromus inermis Leyss.). The experiment was initiated in 1974 on a Wharton‐Cookport (Aquic Hapludults‐Aquic Fragiudults) silt loam soil with an established stand of smooth bromegrass in West Virginia. Labeled (15N‐depleted) ammonium sulfate was surface‐applied annually at rates of 85, 170, and 340 kg N/ha over a 4‐year period. Herbicides (2.2 kg/ha atrazine; 1.1 kg/ha paraquat) were applied annually to the grassed and plowed plots to suppress the grass sod but allow bromegrass to resume growth after corn silage was harvested. The grass was not harvested for hay, but left as a cover crop for erosion control. Yields of corn plants were determined at midseason (11 to 12 leaf stage) and at the silage stage. The proportions of total N uptake contributed by the soil and fertilizer were determined by mass spectrometry.

In 1974 and 1977 when soil water regimes were most favorable, total dry matter (TDM) yields were similar under the two systems of tillage, but in the intervening years of subnormal rainfall, yields were substantially higher from no‐till than from plowed plots. Amounts of available water in the surface 30 cm of soil were consistently higher in no‐till than in tilled plots during the growing season, but differences were not discernible in the underlying 30 an layer. The 4‐year average yields of silage TDM for all N rates were 13,400 and 11,570 kg/ha, respectively, for no tillage and conventional tillage. Because of the lower attainable yields on plowed plots in 1975 and 1976, the corresponding average amount of applied N required for near‐maximum yield under conventional tillage was about one‐half that required for no‐tillage. Soil N uptake tended to decrease with increasing rate of N applied, generally was unaffected by method of tillage, and differences among years were relatively small. For both samplings and all N rates in 1975 and 1976, uptake and recovery of fertilizer N were substantially higher under no‐tillage than under conventional tillage. In 1974 and 1977, enhanced recovery under no‐tillage was evident only at the highest N rate. Four‐year midseason recoveries from 85, 170, and 340 kg N/ha, respectively, were 42, 32, and 26% for no‐till and 35, 27 and 16% for conventional tillage. Corresponding average annual recoveries at silage harvest were 46, 53, and 46% for no‐till, and 53, 55, and 347, for conventional tillage.
Seed Set and d2 Gene Effects on Pearl Millet Forage Quality1
Authors: Hanna W. W. , Gaines T. P. , Monson W. G.
Published: July 2010

Tall and dwarf pearl millet [Pennisetum americanum (L.) Leeke.] hybrids are commercially available and can be either cytoplasmic‐genic male‐sterile or fertile depending on whether the male parent is a restorer line. No information is available on the effects of seed set on forage quality in the tall and dwarf pearl millet hybrids. The purpose of this research was to study effects of seed set and the d2 (dwarf) gene in in vitro dry matter digestibility (IVDMD) and total nonstructural carbohydrates (TNC) in pearl millet forage at anthesis and at 2 and 4 weeks after anthesis. In 1976 and 1977, forage samples were taken from pollinated and unpollinated cytoplasmicgenic male sterile tall and dwarf pearl millet growing in the field. Seed set did not affect IVDMD of the whole plant and leaf or stem components at 2 and 4 weeks after anthesis. Seed set reduced total sugars at 4 weeks after anthesis because of conversion of sugars to starch. Forage from dwarf plants was significantly higher in IVDMD than forage from tall plants; however, there were no differences in the leaf and stem components, which indicates that after anthesis, the higher IVDMD of the dwarf forage is due to the higher leaf percentage of the dwarf. Forage from tall pearl millet had significantly higher levels of total sugar, but significantly lower IVDMD than dwarf pearl millet, which indicates that the nonstructural carbohydrates were not responsible for the higher quality of forage from dwarf pearl millet.
Effects of Mycorrhizae on Establishment and Performance of Forage Species in Mine Spoil1
Authors: Lambert D. H. , Cole H.
Published: July 2010

Mine soil not containing topsoil usually lacks the normal endomycorrhizal fungi which improve the P uptake of many plants. The establishment of mycorrhizae might be useful for low‐cost, low‐maintenance revegetation of abandoned strip mines or other mineral wastes low in available P. The value of establishing endomycorrhizae to improve the growth of forage grasses and legumes on a low‐P strip mine spoil (Schlickig udispolent) was investigated using 1‐cm layers of field soil as mycorrhizal inoculum. In replicated l‐m2 field plots receiving lime but not fertilizer, yields of flatpea (Lathyrus sylvestris L.), crownvetch (Coronilla varia L.), and birdsfoot trefoil (Lotus corniculatus L.) after two seasons were 7, 13, and 18‐fold greater, respectively, in mycorrhizal treatments. Survival after two winters averaged 51 vs. 6% for nonmycorrhizal treatments. In 0.25 m2 plots receiving 0, 41, 81, and 162 kg/ha P or mycorrhizal inoculum at the two low rates of P, the yields of mycorrhizal and nonmycorrhizal plants converged as P was increased. The response of mycorrhizal trefoil improved over 2 years relative to nonmycorrhizal treatments receiving only initial applications of P. Growth of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) in 600‐ml pots in the greenhouse was not significantly improved by mycorrhizae. Mycorrhizal fungi from different sources varied in their adaptation to low‐pH mine spoil. The establishment of mycorrhizae in mining wastes is useful if indigenous inoculum is absent or nonadapted, if available P is low, and if the plant species used for revegetation responds to mycorrhizae. Under these conditions, mycorrhizal plants are more persistant and less affected by the immobilization of fertilizer P.
Stand Thinning in Seed Production of ‘Cougar’ Kentucky Bluegrass1
Authors: Evans David W.
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) seed production typically decreases as the stand ages. Eliminating or reducing this decrease would greatly benefit growers. In earlier research, stand thinning by gapping (removing sections of sad from the row) increased Kentucky bluegrass seed yield for one season where stands were fertilized with low to moderate rates of N. The present study was conducted to determine the effects of single and repeated gapping on seed yield, seed yield components, and the age‐associated seed yield decline in Kentucky bluegrass fertilized with different rates of N.

‘Cougar’ Kentucky bluegrass was grown in rows under sprinkler irrigation and fertilized yearly with 100, 200, or 300 kg N/ha. Alternate 23‐cm sections of the row were removed after harvest in 2 consecutive years, in the 1st year only and in the 2nd year only. Also, alternate 23‐cm sections of ungapped rows were clipped for 2 consecutive years to remove panicles at panicle emergence.

Gapping increased seed weight per panicle by 12% the 1st year and panicles per meter of row and seed yield by up to 39 and 32%, respectively, the 2nd year. Repeated gapping was as effective as first‐time gapping in either year. Clipping, while it decreased panicle numbers and seed yield, increased seed weight per panicle by 20% or more each year and 1,000‐seed weight by 5 to 8%. Seed production was highest for 200 kg N/ha in 1969 and 1970 and for 100 kg N/ha in 1971. Nitrogen rates did not affect gapping or clipping responses.

Density of panicle production within the bluegrass sod was the principal factor affected by gapping. Gapping consistently increased panicle density. Density was increased as much by repeated as by first‐time gapping.

Results of the study indicate that appropriate sod management can increase seed yield and reduce the rate of age‐associated seed yield decline.
Biochemical and Morphological Responses of Cannabis sativa L. to Postemergent Applications of Paraquat1
Authors: Coffman C. B. , Gentner W. A.
Published: July 2010

Paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) has been used to control illicit fields of Cannabis sativa L. (marihuana). Little is known concerning the effects of paraquat on the growth and cannabinoid concentrations of C. sativa. Therefore, three greenhouse experiments were conducted to 1) apply paraquat postemergent to C. sativa plants under controlled conditions; 2) evaluate the morphological responses of C. sativa to paraquat applications; and 3) determine the effect of paraquat applications on the concentrations of cannabidiol (CBD) and Δ9tetrahydrocannabinol (Δ9THC) in marihuana. Paraquat was applied at 0.07, 0.14, and 0.28 kg/ha. In the first experiment, plants were treated 51 days after seeding (DAS) and harvested 23 days after treatment. CBD and Δ9THC concentrations were reduced 70 and 67% respectively over all herbicide applications. Plants were treated 49 DAS in the second experiment and harvested 0, 1, 2, 4, and 8 hours and 1, 2, 4, 8, and 16 days after treatment. Delta‐9‐THC concentrations were significantly reduced by paraquat applications. Plants were treated with paraquat 25, 35, 65, and 75 DAS in the third experiment and harvested 10 days later. Plant growth, marihuana production, and Δ9THC concentrations were generally significantly lower for the herbicide‐treated plants relative to the untreated controls. These experiments revealed that Δ9THC concentrations in marihuana were generally reduced by the application of lethal or sub‐lethal rates of paraquat to C. sativa plants of varied chronologic and physiologic ages.
Plant Uptake and Leaching of Applied and Indigenous Potassium in Dothan Soils1
Authors: Sparks D. L. , Martens D. C. , Zelazny L. W.
Published: July 2010

The K fertilization requirement for corn (Zea mays L.) frequently is overestimated by soil test procedures for Atlantic Coastal Plain soils having sandy Ap horizons and high K concentrations in clayey subsoil. It seemed probable that the lack of response could reflect availability of subsoil K. This field and laboratory research was conducted to evaluate the availability and origin of subsoil K and the downward movement of K in two Dothan soils (Plinthic Paleudults). These soils had low CEC in the Ap, A2, and B21t horizons; fine sandy loam Ap horizons; higher clay contents in the B21t horizons than in the Ap horizons; and very acidic B21t horizons. Mineral suites in the clay‐sized fraction of the two soils were predominantly 14 A intergrade minerals, kaolinite, and quartz. The three horizons in these two soils contained high levels of total K ranging from 6.5 to 12.0 meq/100 g. Over 90% of the total K in the A2 and B21t horizons of the two soils was in feldspar and mica forms indicating that parent material, rather than leaching of applied K, was the main origin of K in these horizons. Decreases in exchangeable K occurred during the first growing season in the A2 and B21t horizons of control plots in field experiments on the two soils. These decreases in exchangeable K indicated K uptake by corn plants from the subsoil horizons. With time, two‐annual broadcast applications of 83 and 249 kg K/ha as KCl increased the exchangeable K in the A2 and B21t horizons of the two soils. These increases were ascribed to leaching of K into the subsoil horizons. This leaching of K suggests that downward movement of applied K could result in an accumulation of K in clayey subsoil. The K in subsoil, either from leaching of applied K or from genetic origin, would be available to plants unless root growth into the subsoil was restricted by adverse chemical and physical properties.
Small Plot Liquid Applicator1
Authors: Walker M. E. , Shannon J. E.
Published: July 2010

The application of liquid fertilizer and other solutions to small experimental areas creates a problem because most equipment is constructed for farm application. There was a need for a small plot applicator that would accurately dispense liquid fertilizer 10‐34‐0, as well as other solutions. A two‐row cultivator (Pittsburg) frame was equipped with a system activated by carbon dioxide. A 19‐liter stainless steel tank (Firestone) was used for mixing chemical solutions.

This system allows surface and subsurface application of fertilizer solution and can easily be converted to a sprayer for application of solutions to plant foliage. Various combinations of solutions, rate, and pressure are available to meet the applicator's specifications.
Greenhouse Evaluations of Strains of Rhizobium for Peanuts1
Authors: Wynne J. C. , Elkan G. H. , Meisner C. M. , Schneeweis T. J. , Ligon J. M.
Published: July 2010

The use of effective strains of Rhizobium can increase the yield of peanuts (Arachis hypogaea L.) substantially. Preliminary screening of rhizobial strains for effectiveness in leguminous crops is generally done in greenhouse tests. This study was conducted to develop reliable greenhouse procedures for the evaluation of rhizobial strains for peanuts and to determine the variability in N‐fixing ability of rhizobial strains in symbiosis with genetically diverse peanut hosts.

Using ‘Argentine’ (a Spanish genotype) and ‘NC 4’ (a Virginia genotype), 18 rhizobial strains, 9 in each of two tests, were compared with an uninoculated control for N‐fixing ability. Strains of Rhizobium varied in their N‐fixing ability in both tests as evaluated by nodulation, nitrogenase activity, plant color and weight and N content. Plants of NC 4 were larger and greener and had larger nodules, greater nitrogenase activity and higher N content than plants of Argentine. Host‐strain specificity was found for several traits indicative of N‐fixing activity.

Nodulation, plant color and weight, nitrogenase activity, and N content were significantly correlated. The high significant correlation of total nitrogen and plant dry weight (r = 0.99** and r = 0.97**) and total nitrogen and plant color (r = —0.95** and —0.97**) indicates that either plant color and/or plant dry weight can be used as a measure of strain effectiveness in preliminary tests.

Greenhouse screening of rhizobia for effectiveness on peanuts using plant weight or color was determined to be an excellent initial evaluation of strain efficiency. Because of host differences and host‐strain specificities, the peanut genotype should also be considered in rhizobial testing.
Germination of Three Species of Atrifilex1
Authors: Young J. A. , Kay B. L. , George Harry , Evans R. A.
Published: July 2010

Trailing saltbush (Atriplex semibaccata R. Br.), quailbush [A. lentiformis (Torr.) Wats.], and fat‐hen [A. patula ssp. hastata (L.) Hall & Clem.] are adapted for growth in saline‐alkaline areas and provide valuable cover, browse, and/or feed for waterfowl. We undertook this study to evaluate the germination characteristics of these species which have potential as artifically‐seeded revegetation species. Germination tests were conducted at 55 constant and alternating temperatures. The constant temperatures were 0, 2, and 5 C and in 5° increments through 40 C. Alternating temperature regimes consisted of 16 hours at each constant and 8 hours daily at each higher constant temperature. Tests were conducted in both lighted and dark germinators for entries that responded to light at six constant temperatures. In addition, tests were conducted with presoaked seeds at eight constant temperatures. Germination was evaluated on sand, loam, and clay textured substrates. The optimum germination for all three species tended to occur with alternating rather than constant temperatures. Fat‐hen was the only species whose germination was enhanced by light during the warm period. Seeds of this species were highly germinable with optimum germination averaging 96%. ‘Corto’ trailing saltbush and quailbush seeds were also highly germinable. However, overall mean germination and optimum germination were somewhat lower than those observed for fathen. Presoaking and rinsing the false‐fruits increased the germination of the other two species at some incubation temperatures, but not the germination of fat‐hen. The species differed in requirements for seed burial with fat‐hen germinating on the surface of sand, loam, and clay soils but quailbush largely requiring burial. Trailing saltbush exhibited intermediate germination requirements relative to seed burial. Although each species had a different germination profile, seedbed temperatures within moderate ranges will not be limiting to their use as revegetation species.
Soybean Cyst Nematode and Rhizobium Strain Influences on Soybean Nodulation and N2‐fixation1
Authors: McGinnity P. J. , Kapusta George , Myers Oval
Published: July 2010

The spread of the soybean cyst nematode (SCN) (Heterodera glycines Ichinhoe) has required the breeding of resistant soybean [Glycine max (L.) Merr.] cultivars. The SCN causes a reduction in nodulation and N2‐fixation which may explain part of the yield reductions associated with SCN infestations. This study was designed to determine the interaction effects of SCN resistant and susceptible cultivars, Rhizobium japonicum (Kirch.) Buchanan strains, and SCN races on nodulation and N2‐fixation.

The susceptible cultivar ‘Williams’ and resistant cultivars ‘Bedford’, ‘Forrest’, and ‘Franklin’ were grown on sterile sand culture in the greenhouse and inoculated with all possible combinations of SCN races 3 and 4 and R. japonicum strains 3, 110, and 123. Bedford and Forrest inoculated with strain 110 had the highest specific N2(C2H2)‐fixation activity (SA), but Bedford, Forrest, and Franklin inoculated with strain 123 had the largest nodule mass (NM). SCN race 3 did not reduce NM, but reduced both total N2(C2H2)‐fixation activity (TA) and SA. Race 4 did not influence TA and was inconsistent in its influence on SA and NM.

Total N2(C2H2)‐fixation activity and SA was estimated at the R2 (determinate) and R4 (indeterminate) stages on several field‐grown soybean cultivars. The number of SCN cysts per 250 cc of soil (cyst index) also was determined. Resistant cultivars had low cyst indices and high N2‐fixation potentials. Susceptible cultivars had higher cyst indices and generally lower N2‐fixation rates but ‘Williams’, ‘Wayne’, and ‘York’ exhibited high fixation potentials despite high cyst indices. Nodule serology indicated a significant cultivar ✕ strain interaction which may account for the TA and SA differences.

These results indicate that nodulation and N2‐fixation are influenced by cultivar ✕ Rhizobium strain and SCN race interactions and that the SCN is not equally deleterious to all susceptible cultivars. Williams and Wayne may be especially valuable in breeding resistant cultivars since they exhibited good nodulation and N2‐fixation despite high cyst indices.
Yield Reduction from Defoliation of Irrigated and Non‐Irrigated Soybeans1
Authors: Caviness C. E. , Thomas J. D.
Published: July 2010

Hail adjusters, entomologists, and others frequently use defoliation percentages to estimate soybean [Glycine max (L.) Merr.] yield loss caused by hail, insects, or diseases. Little information is available on the percent yield loss from defoliation under drought stress and adequate moisture. Thus, the objective of this research was to measure yield response of a determinate soybean cultivar ‘Lee 74’ to different levels of defoliation under irrigated and non‐irrigated conditions. Field experiments were conducted on a Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualfs) at Stuttgart, Ark., during a 3‐year period to study effects of four levels of defoliation (0, 50, 75, and 100%) applied at three stages of development (V5, R2, and R4) in 1974 and 1975 and two stages (V3 and R5) in 1976 on yield of irrigated and nonirrigated soybeans.

Irrigation significantly increased yield 7% in 1974, 38% in 1975, and 51% in 1976. Mean squares for levels of defoliation, stages of treatment, and the defoliation × stage interaction were highly significant each year. The least reduction in yield occurred when plants were defoliated at vegetative stages, V3 and V5, and the most at reproductive stages, R4 (full pod) and R5 (beginning seed). Average yield reductions for 50, 75, and 100% defoliation were 11, 17, and 37%, respectively.

Percent yield reductions under irrigated and non‐irrigated conditions were similar because all interactions with irrigation treatments were non‐significant. This same pattern existed regardless of whether the season was extremely dry as hi 1975 and 1976 or moderately dry as in 1974. Reduction in number of pods appeared to be the yield component primarily responsible for yield losses from defoliation. Results from these experiments indicated that percent reduction in yield from defoliation is similar for soybeans grown with adequate moisture or under drought stress.
A Small Plot Drag for Use on Bermudagrass or Similar Sods1
Authors: Keisling T. C. , Holt Edwin
Published: July 2010

Many types of drags and spike tooth harrows have been used in pasture work. Most are not suitable for small plot work with bermudagrass because of lack of uniformity resulting from the dragging operation, fouling and clogging of the teeth with plant parts, and their cumbersome operation. This note describes a small unit which drags a plot uniformly, exhibits essentially no fouling or clogging of the teeth and is easily maneuverable around and through a plot area.