bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Fertilizer‐N and Herbicides on the Growth and N Content of Soybeans and Cowpeas1
Authors: Behran Sh. , Maftoun M. , Sheibany B. , Hojjati S. M.
Published: July 2010

Little is known about herbicide‐N fertilizer interaction with respect to the growth and N content of soybeans (Glycine max (L.) Merr.) and cowpeas (Vigna unguiculata). This study was undertaken to evaluate the effect of added N and trifluralin (α, α, α‐trifluoro‐2, 6‐dinitro‐N, N‐dipropyl‐ρ‐toluidine), nitralin [4‐(methylsulfonyl)‐2, 6‐dinitro‐N, Ndipropylaniline] and diphenamid (N, Ndimethyl‐2, 2‐diphenylacetamide) on the growth and N uptake by these two crops.

Soybeans and cowpeas were grown in greenhouse for 74 days in soil treated with various levels of N (0, 25, and 50 ppm) and herbicide (0, 1, 2, and 3 ppm). Leaf chlorophyll, dry matter yields, N concentration and N uptake were determined. All N‐treated soybean and cowpea plants had greater chlorophyll content, produced more growth and contained higher N than untreated check. An increase in growth and N uptake suggests that symbiotic N fixation probably failed to supply all of N required for optimum growth.

Application of 1 ppm trifluralin slightly increased growth and N content of cowpea and enhanced chlorophyll content, N concentration and root dry weights of soybean. However, higher concentrations exhibited strong phytotoxic effects. Soybeans treated with 3 ppm of herbicide developed stunted and chlorotic leaves and had fewer nodules than untreated seedlings.

Soil amended with nitralin and diphenamid reduced leaf chlorophyll, growth and N uptake of soybeans and cowpeas. Moreover, nitralin exhibited a stronger inhibitory effects in roots than tops and was slightly less phytotoxic than trifluralin. Diphenamid‐treated plants developed chlorotic leaf margins, followed by necrosis at the leaf edge.

N addition to trifluralin treatment only affected N content of soybeans significantly, whereas there was increased chlorophyll content, N concentration and top dry weights of cowpea. On the other hand, N applied to nitralin and/or diphenamid‐treated soybeans and cowpeas resulted in an increase in dry weight and N content of tops, probably due to better nutrient and water supply to plants.
Depth of Lime Incorporation for Correction of Subsoil Acidity1
Authors: Doss B. D. , Dumas W. T. , Lund Z. F.
Published: July 2010

Since most Southeastern U. S. soils ate acid, crop yields can generally be improved by liming surface soil. However, it is not known if plants will respond to deep incorporation of lime. Field experiments were conducted on two soils (Rhodic Paleudult and Typic Paleudult) at three locations in central and south Alabama to evaluate the effect of depth of Incorporation of surface‐applied lime on root system development, plant growth, and yield on acid soils. Soil pH ranged from 4.1 to 4.8 before liming. Sufficient lime was surface‐applied and incorporated to the 15, 30, and 45‐cm soil depths to increase pH in the treated zone to at least 6.0. All plots were initially chiseled to the 45‐cm depth to reduce physical differences resulting from subsequent lime incorporation. Depth of rooting, soil water extraction, plant height, and cotton (Gossypium hirsutum L.) and corn (Zea mays L.) yields were increased by lime. Based on the results from these two soils, incorporating lime to the 30‐cm depth is sufficient to obtain a satisfactory root system for high crop yields of cotton and corn.
Correcting pH‐Induced Manganese Deficiency in Bermudagrass Turf1
Authors: Snyder G. H. , Burt E. O. , Gascho G. J.
Published: July 2010

Manganese deficiency of ‘Tifgreen’ bermudagrass (Cynodon ✕ magenissii Hurcombe) turf has been observed in South Florida when soil pH exceeded 7 as a result of irrigation with alkaline water. A 2‐year field study on Pompano fine sand (a siliceous, hyperthermic, typic Psammaquent) was designed to evaluate three approaches to correcting this deficiency: 1) soil pH reduction with acid forming N sources, 2) Mn fertilization at rates up to 5 g/m2 using MnSO4, a Mn‐chelate, or a Mn‐frit, and 3) MnSO4 fertilization in combination with a series of fungicidal drenches for suppressing Mn‐oxidizing soil fungi. Sulfate and chelate Mn sources provided short‐term correction of the deficiency, but little response to the frit source was noted. Sustained correction was achieved with MnSO4 in combination with the fungicidal drenches. However, adequate Mn nutrition was obtained even in the absence of Mn fertilization when soil pH was maintained below 7 with acid‐forming N sources. This treatment appears most suitable for turfgrass, since considerable N commonly is used in turfgrass production.
Persistence and Productivity of Tall Fescue in Bermudagrass Sods Subjected to Different Clipping Managements1
Authors: Fribourg Henry A. , Overton Joseph R.
Published: July 2010

Bermudagrass (Cynodon dactylon (L.) Pers.) is a vigorous and productive forage crop in the U.S. mid‐South during the warm season, but is dormant from October through March. Tall fescue (Festuca arundinacea Schreb.) is semidormant in summer, grows well in spring and to some extent in autumn and winter. The objective of this study was to determine the effects of combinations of N fertilization level, harvesting management, and fescue row spacing, on the productivity and persistence of both bermudagrass and fescue in bermudagrass sods overseeded with fescue. ‘Kentucky 31’ tall fescue was overseeded in 25 or in 50‐cm rows in October, 1970 on an established ‘Midland’ bermudagrass sod growing on a coarse‐silty, mixed, acid thermic, aeric Fluvaquents soil at the West Tennessee Experiment Station, Jackson. Four rates of N fertilization included: none; or 200, 400, or 600 kg N/ha/year applied in four equal installments. Three clipping managements were superimposed: 5‐cm growth cut to a 2.5‐cm stubble, 10‐cm growth cut to a 5‐cm stubble, and 30‐cm growth cut to a 25‐cm stubble. Persistence of each species, composition of dry matter yield, and N content of harvested forage were measured from 1972–1975. When N was not applied, or when 200 kg N/ha/year were applied, fescue stands were excellent. Higher N rates resulted in half a stand. Fescue stands were less persistent in 50‐cm than in 2.5cm rows. Bermudagrass sods were maintained under all management conditions. Under the frequent 10 to‐5 cm and 5 to‐2.5 cm managements and with 200 kg N/ha/year, 1,500 kg dry matter/ha or more were harvested in each of four harvest periods (late winter to mid‐May, mid‐May to mid‐July, mid‐July to September, October through December) from the grass associations. The combination of the two species extended the season of production of the sod from 5 to 9 or 10 months/year during each of 3 years and increased dry matter production from 5,800 to 7,150 kg/ha/year. Most uniform production each year was obtained when fescue was seeded in 25‐cm rows and harvested from 10‐cm height to a 5‐cm stubble.
Soybean Desiccation by Paraquat, Glyphosate, and Ametryn to Accelerate Harvest1
Authors: Whigham D. K. , Stoller E. W.
Published: July 2010

Chemical desiccation is often desirable to hasten maturity so seed can be harvested earlier than normal. Soybeans {Glycine max (L.) Merr.} were sprayed with paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium ion) at 0.6 and 1.1 kg/ha, glyphosphate {N‐(phosphonomethyl) glycine} at 1.7 and 3.4 kg/ha, and ametryn }2‐(ethylamino)‐4‐isopropyl amino‐6‐methythio‐s‐triazine} at 1.1 and 2.2 kg/ha 4, 3, and 2 weeks before the estimated harvest date to desiccate the soybeans and accelerate harvest. The objective was to determine the effect of pre‐harvest chemical desiccation on seed yield and quality. In field experiments, on a fine, montmorillonitic mesic Aquic Arguidoll, Flanagan series soil, harvest was accelerated, but all chemicals significantly reduced yields when they were applied 3 and 4 weeks before harvest. Yields were not significantly reduced by applications 2 weeks before harvest. Paraquat was the most effective desiccant for accelerating soybean harvest. Paraquat also reduced yield and seed weight the most while glyphosate had the least effect. Growth chamber studies indicate that ametryn and paraquat did not affect seed germination or seedling vigor, but all glyphosate applications significantly reduced germination and soybean seedling vigor.

Chemical desiccation of soybeans prior to physiological maturity will significantly lower soybean yields. Glyphosate is not recommended as a desiccant.
Root Adjustments Associated with Salt Tolerance in Small Grains1
Authors: Bower C. A. , Tamimi Y. N.
Published: July 2010

Discovery of the physiological basis of salt tolerance in small grains and its use to obtain more tolerant cultivars especially of rice (Oryza sativa L.) by modern plant breeding procedures should permit substantial increases in world food production. The purpose of this study was to test the hypothesis that at a given level of root media salinity the salt tolerance of various small grain cultivare is directly related to the total salt concentration of the root water. Cultivars were grown in the greenhouse ;1 to 6 weeks after transplanting as seedlings on nonsalini: and saline culture solutions. Shoots of cultivars grown on saline solutions invariably had a lower water conteni: than shoots grown on nonsaline solutions, indicating thai: salt injury involves water stress. Salt tolerance of the various cultivars, expressed as relative yield on saline cultures, was highly related to the salt concentration of root water with two exceptions, and was highly related without exception when relative root growth on saline culture was taken into account.

In agreement with previous observations, it was found that the order of salt tolerance of small grains, at least in the vegetative stage, is barley (Hordeum vulgare L.) > rye (Secale cereale L.) ≅ wheat (Triticum aestivum L.) > oat (Avena sativa L.) > rice.
Utilization of 15N Fertilizer by Nodulating and Non‐Nodulating Soybean Isolines1
Authors: Deibert E. J. , Bijeriego Manuel , Olson R. A.
Published: July 2010

Uncertainty remains concerning the magnitude of symbiotic N fixation by the soybean crop [Glycine max (L.) Merr.] when grown under varied N management systems. For deriving further enlightenment on the issue, 15N‐enriched fertilizer was applied on two soybean isolines with objectives of measuring the fraction of N derived from symbiotic fixation, residual soil N and applied fertilizer N. Plant samples were collected at full bloom, beginning‐seed, and full‐maturity stages in a field experiment conducted at the University of Nebraska Field Lab on Sharpsburg soil (Typic Argiudoll) of 3.3% organic matter content. Nitrogen fertilizer was applied at rates of 45, 89, and 134 kg/ha at planting or at full bloom.

Nitrogen fertilization had no significant influence on yield or N and oil concentration of the nodulating isoline seed but increased these parameters of the non‐nodulating isoline, with delay in N fertilization being distinctly advantageous. Fertilizer utilization percentage by both isolines at later growth stages increased as fertilizer rate increased, contrary to N utilization patterns of cereal crops.

“A ” value increases with increased N fertilizer rates suggested a soil N priming and/or root extension effect. Less plant N came from the soil with delayed N fertilizer application. Fertilizer applied at planting at rates above 45 kg N/ha reduced the symbiotically fixed N fraction, whereas delaying fertilizer application had no such influence at any rate of N employed.
Differential Use of Fe3+ and Fe2+ by Oats
Authors: Brown J. C.
Published: July 2010

Plants have specific Fe requirements, dependent on their ability to make Fe available in a useful form. They are classed Fe‐efficient if they respond to Fe‐deficiency stress by inducing biochemical reactions that make Fe available in a useful form, and Fe‐inefficient if they do not. This study was conducted to characterize the use of Fe by Fe‐inefficient oats (Avena byzantina K. Koch) ‘TAM 0‐312,’ and Fe‐efficient oats ‘Coker 227.’ These cultivars were grown in nutrient solutions where they were subjected to different degrees of Fe stress induced by variable concentrations of either phosphate, CaCO3, or Fe. The oat plants were grown in an environmentally‐controlled chamber with 16 hours of light at approximately 320 µEm‐3 sec‐1 and 8 hours of darkness at a temperature of 24 ± 2 C. Coker 227 was more Fe‐efficient than TAM 0‐312 regardless of how Fe stress was induced and usually contained less Ca than TAM 0‐312. TAM 0.312 required 1.2 mg Fe/liter in the nutrient solution before it was green, whereas Coker 227 required only 0.6 mg Fe/liter. Susceptibility to Fe chlorosis in these cultivars was caused by the inherent nature of the plant to use either Fe8+ or F2+ and by the greater use of Ca by TAM 0‐312 than by Coker 227. The plant plays a key role in maintaining a proper nutrient elememt balance and the availability of a nutrient element for plant use.
Performance of Spring Barley in Narrow Rows1
Authors: Brinkman M. A. , Luk T. M. , Rutledge J. J.
Published: July 2010

Several researchers in the U. S. and Canada have investigated the effect of row spacing on yield and other agronomic traits of small grains with variable results. The objective of this study was to compare the performance of spring barley (Hordeum vulgare L. emend Bowden) seeded in a very narrow row spacing (7.5 cm) with two row spacings (15 and 30 cm) commonly used in production agriculture and in experimental research. Three genotypes were planted at Madison, WI, in 1975 and 1976, in a St. Charles silt loam soil (Typic Hapludalf, fine‐silty, mixed, mesic) and at Arlington, WI, in 1977, in a Plano silt loam soil (Typic Arguidoll, fine‐silty, mixed, mesic). A seeding rate of 134 kg/ha was used in all row spacings. The three environments had yield levels ranging from high to low, due primarily to differences in rainfall.

When results were combined over environments, 7.5 cm‐rows yielded 4% more grain than 15‐cm rows and 12% more grain than 30‐cm rows. These differences were significant, but differences were not always significant for a single environment. Straw yield response to row spacing was similar in magnitude to the grain yield response. The increased grain and straw yields in narrower rows were attributed to greater tillering. There was significantly less lodging in 7.5‐cm rows than in 15 and 30‐cm rows in the two environments in which lodging occurred.

Although the grain and straw yield improvements in this study may not be large enough to encourage changing to grain drills with a row spacing narrower than 15 cm, the reduced lodging in 7.5‐cm rows may be an added advantage when lodging is substantial.
Bermudagrass Survival as Influenced by Deacclimation, Low Temperatures, and Dormancy1
Authors: Chalmers D. R. , Schmidt R. E.
Published: July 2010

Winter survival is the most relevant problem in using bermudagrasses (Cynodon sp.) for turf in the northern limit for adaptation of semitropical grasses (upper south, U.S.). This research was conducted to investigate the effects of deacclimation, freezing temperatures, and duration of dormancy after exposure to freezing temperature on survival of bermudagrasses. ‘Tifgreen’ bermudagrass was taken from the field in February 1976, and deacclimated for 0, 2, 4, or 8 days at 27/13 C (day/night). Subsequently, rhizomes and stolons were subjected to temperatures of +2, 0, −2, −4, or −6 C for 24 hours. One‐third of the samples from each treatment were maintained in dark storage for 0, 45, and 90 days at 2.7 C ± before being grown in a greenhouse for 4 weeks.

Rhizomes and stolons subjected to −1 or −6 C did not survive. Deacclimation with subsequent low temperature and extended dormancy duration appeared to have a compound influence on viability of stolons. Rhizomes were not so affected. At temperatures of −2 C or higher, viability of stolons did not decrease with deacclimation up to 4 days. However, with deacclimation up to 4 days, rhizome bud survival was enhanced. Survival of rhizome buds was significantly better at 0 C than −2 C; whereas, survival of stolon buds was not. Prolonged dormancy after exposure to low temperatures reduced the viability of both stolons and rhizome buds.

Findings indicate that below freezing temperatures and prolonged dormancy durations after freezing hinder the survival of bermudagrass whereas, short deacclimation periods before freezing do not.
Use of Segmented Regression in the Determination of the Base Temperature in Heat Accumulation Models1
Authors: Gbur E. E. , Thomas G. L. , Miller F. R.
Published: July 2010

An accurate determination of the base temperature in heat accumulation models is extremely important if the model is to be used for predictive purposes. A modification of the simple linear regression is proposed for estimating the base temperature from laboratory data. The results of a small simulation study indicate that the proposed method is more accurate than a commonly used method. A numerical example of the use of the proposed method is presented.
Test of the Stress‐Degree‐Day Concept Using Multiple Planting Dates of Red Kidney Beans
Authors: Walker G. K. , Hatfield J. L.
Published: July 2010

Canopy temperature measurements indicate crop water stress and should be related to crop yield. In this study, several planting dates and soil moisture levels were used to evaluate the stress‐degree‐day (SDD) concept as an indicator of crop yield. Red kidney beans (Phaseolus vulgaris L.) were planted on four dates, equally spaced, during a 9 week period from mid‐May to mid‐July, 1978. Beans were hand‐planted in 20 ✕ 5 m field plots on a silt loam with 76 cm row spacing at 165,000 ha‐2 Five irrigation treatments within each planting date provided a wide range of soil moisture conditions. The driest treatment in each planting didn't receive additional water after germination, while the wettest was continually well supplied with water. Moisture extraction in all treatments was measured to 180 cm three times weekly with the neutron scattering technique. Canopy temperatures were measured with an infrared thermometer each day throughout the growing season about 1 hour after solar noon. Stress‐degree‐days were calculated for each treatment by using air temperature recorded next to the plot area. Linear regression demonstrated that seed yields were strongly dependent on the accumulation of stress degree days from flowering to maturity (r2 = 0.82), indicating the importance of the post‐vegetative stage to final yield. Inclusion of the SDD summation from emergence to flowering as a second independent variable did not significantly improve the regression (R2 = 0.83). Individual regression lines for each planting were not significantly different (P = 0.05), demonstrating that the yield‐stress degree day relationship was stable over a wide range of planting dates. Total water use was negatively correlated with stress‐degree‐days summed from flowering to maturity (r = −0.83), verifying the potential for using the SDD concept in water management. The data also confirm that the SDD concept is a valid representation of the effect of moisture stress on yield, and point to the potential for using remotely determined canopy temperatures in estimating yields over large areas.
Estimating the Contribution of a Perched Water Table to the Seasonal Evapotranspiration of Cotton1
Authors: Wallender W. W. , Grimes D. W. , Henderson D. W. , Stromberg L. K.
Published: July 2010

Water supplied to a growing crop by capillary rise from a shallow water table can be an important resource. Several thousand hectares in the western San Joaquin Valley in California have a perched water table created by irrigation and a slowly permeable subsurface zone. When irrigations are made according to a schedule that is optimum for soils without a shallow water table, cotton (Gossypium hirsutum L.) frequently shows plantgrowth that is characteristic of excessive irrigation. Field studies were conducted to evaluate the contribution of a perched water table to the evapotranspiration (ET) demand of cotton and to develop an irrigation schedule that uses the resource effectively.

Two independent procedures were used to estimate the water table contribution (WT) through capillary rise. A water budget method used a previously developed yield‐ET function to estimate ET from observed production levels. Soil moisture depletion (SMD), stored irrigation water (IW), and deep percolation (PW) were determined from neutron thermalization measurements on volumetric soil water content. WT was determined by rearranging the relation ET = SMD + IW − PW + WT. A second approach, associated the chloride in the water table (17.4 meq/l) with increased chloride concentrations in the soil above the water table. The equivalent water depth necessary to effect this change was calculated. Both procedures estimated WT to be near 36 cm for the growing season. A high standard deviation (18.7 cm) was caused, however, by considerable spatial variability for the chloride tracer method.

A revised irrigation schedule for cotton was developed that uses water, of acceptable quality, derived from a water table as a beneficial raource.
Row‐Plant Spacing and Broiler Litter Effects on Intercropping Corn in Tall Fescue1
Authors: Harper L. A. , Wilkinson S. R. , Box J. E.
Published: July 2010

Conservation tillage methods are needed to produce grain and forage for an important livestock industry on the highly erosive soils of the southeastern U. S. The objective of this research was to evaluate the effect of row widths, corn spacing within the row, and fertility level on the yield of corn (Zea mays L.) and Kentucky‐31 tall fescue (Festuca arundinacea, Schreb) when the corn was no‐till planted into 20‐cm killed strips of tall fescue grown under irrigated conditions in Cecil sandy loam (Typic Hapludult, clayey, kaolinitic, thermic). Corn row widths of 51 and 102 cm were the main plots, within‐row plant spacings of 16, 29, 38, and 47 cm were subplots and fertility levels of 9 and 18 metric ton/ha broiler litter and conventional fertilizer (358,134, and 268 kg/ha N‐P‐K, respectively) were sub‐sub lots in a randomized block design. The study was conducted for two corn seasons and two tall fescue seasons on the same plot area.

Optimum corn plant density for obtaining the highest possible possible corn yields, while simultaneously maintaining the tall fescue sod, averaged 60,0000 plants/ha for the three fertility treatments. Average corn grain yields at this optimum plant density were 6.3 metric tons/ha for the 9 metric tons/ha broiler litter, 10.8 metric tons/ha for the 18 metric tons/ha broiler litter, and 8.7 metric tons/ha for the conventional fertilizer treatments. Based on total‐N analysis of broiler litter, the N from broiler litter was about 77% as efficient as N supplied from NH4NO3, in producing corn yield. Comparing similar plant densities with different row and plant spacings, we found that fescue yields were 2.6 times greater during the winter period under a 102‐cm wide row with plants spaced 16 cm apart in the row than under a 51‐cm wide row with plants spaced 29 cm apart within the row. Corn yields or corn plant populations were not significantly different at these two planting configurations. Despite the reduced sod area due to the herbicide killed strip, annual yields of tall fescue were also reduced at narrow row spacings because of decreased stand and sod vigor. This study illustrates the corn plant population and planting geometries which can result in good yields of tall fescue and interplanted corn under irrigation.
Planting Date and Water Deficit Effects on Development and Yield of Irrigated Winter Wheat1
Authors: Musick J. T. , Dusek D. A.
Published: July 2010

Major variability occurs in yield response of irrigated winter wheat (Triticum aestivum L. em Thell.) to water deficits and irrigation in the Southern High Plains. Evaluation of plant growth and development and yield components are needed to better understand water relations and to develop and test growth and yield models. The study was conducted to evaluate the effects of three planting dates, four to six water deficit treatments during stages of plant development, and two short wheats, ‘TAM W‐101’ and ‘Vona,’ differing in yield components. Planting dates were early (15 September), normal (12 October), and late (7 November). Water deficits were established by withholding irrigation and were terminated at selected plant stages by applying irrigation to level border plots. The study was conducted on a slowly permeable Torrertic Paleustoll (Pullman clay loam). We evaluated development stages, tillering, plant water potential, grain and dry matter yields, and yield components of heads per m2 spikelets per head, grain per spikelet, grain weight and number per m2.

Early to normal planting, as compared with late planting (i) advanced the dates of phenological development, (ii) lengthened the time in the vegetative period, (iii) lengthened the time from floral initiation to inflorescence, (iv) increased tillering during vegetative growth and tiller senescence during jointing, and (v) increased dry matter and grain yields. Plant water deficits reduced yields by increasing tiller and stem senescence, which reduced harvested heads, and by reducing grain numbers (spikelets per head and grain per spikelet). Vona produced more secondary tillers and grains per head, but tiller‐stem senescence and smaller grain size resulted in harvested head numbers and grain yield similar to those of TAM W‐101.

High yields (5,580 kg/ha) were associated with adequate fall‐tillering and irrigation during spring vegetative growth that minimized stress‐associated tiller‐stem senescence and reduction in spikelets per head. TAM W‐101 was more resistant than Vona to severe desiccation and tillerstem senescence under severe water deficits. A fall irrigation applied before winter dormancy delayed the need for a spring irrigation until jointing. Irrigation just before a period of above average rainfall did not affect yields. Yields comparisons of TAM W‐101 and Vona indicate that similar high yields can be produced by varieties having large differences in seed size and number per m2, suggesting that specific yield components may not be closely correlated with high yield potential.
Determining Winter Wheat Stand Densities Using Spectral Reflectance Measurements1
Authors: Aase J. K. , Siddoway F. H.
Published: July 2010

Remote sensing would be a valuable tool to decision making and crop forecasting groups to gain knowledge of winter wheat acreage, extent of winterkill, and the potential acreage that may be reseeded to spring crop. To simulate winterkill, seven winter wheat (Triticum aestivum L.) stand variables of 0, 10, 20, 40, 60, 80, and 100% of full stand (full stand = seeding rate of 67 kg/ha) were established by seeding to stand. The plots, 20 ✕ 20 m, were located on Williams loam (fine‐loamy mixed, Typic Argiborolls) near Sidney, Mont. An Exotech Model 100‐A ground truth radiometer, corresponding to LANDSAT multispectral scanner (MSS) bands 4, 5, 6, 7, (0.5 to 0.6, 0.6 to 0.7, 0.7 to 0.8, and 0.8 to 1.1µm), was used to measure reflected radiation at 0930 hours MST on clear or nearly clear days. We chose the comparatively simple, but physically meaningful normalized difference vegetation index, VI7 = (MSS7 − MSS5)/(MSS7 + MSS5), with the variant of substituting MSS6 for MSS7 to illustrate crop cover differences. In an attempt to better distinguish soil background from crops and to improve on the crop‐vegetation index relationship, we included the more complex, but also physically meaningful, perpendicular vegetation index, PVI = [(Rgg5 − Rp5)2 + (Rpp7 − Rp7)2]1/2 with the variant of substituting MSS6 for MSS7.

Early in the season, VI7 delineated stands ≥40% from those <40%, allowing a judgment as to whether or not a field would need to be reseeded to spring crops. A winter wheat survival of about 40% is generally considered adequate to provide a reasonably good stand if plants are properly spaced. The 10 and 20% plots became distinguishable from the soil background at a biomass accumulation of about 30 kg/ha (LA1 ≃ 0.06).

There was no advantage of using either variant of the PVI over the VI7 when plotted against leaf area index (LAI) or leaf dry matter (LDM). Both yielded a family of straight lines, with indices of determination ranging from 0.796 to 0.942, and slopes decreasing from the 10% plot to similar slopes for the 80 and 100% plots.
Yield Trends and Soil Chemical Changes Resulting from N and Manure Application to Continuous Corn1
Authors: Magdoff F. R. , Amadon J. F.
Published: July 2010

Many Vermont dairy farms are located in a region where clay soils are common and represent much of the land topographically suited to row crops. Since these soils frequently have restricted drainage, soils are used for corn (Zea mays L.) that would be considered unsuitable in other regions. To evaluate long‐term yield trends and the effects of various treatments on crop and soil, corn silage was grown for 11 years on a somewhat poorly‐drained Panton clay soil (Typic Ochraqualf). Four rates of manure (0, 22, 44, and 66 metric tons wet weight/ha) and five rates of ammonium nitrate‐N (0, 56, 112, 168, and 224 kg N/ha) were combined factorially and applied annually to plots from 1965 through 1975.

The highest yields were produced by combining 44 metric tons of manure and 224 kg N (44M to 224N). However, the 22M to 112N treatment yields were not significantly different from the highest treatment yields. The check treatment (OM‐ON) was initially 82% of the highest treatment yield, but by the end of the experiment was about 54% of the maximum yields. Annual yield fluctuations were correlated with variations in rainfall.

The effect of inorganic‐N fertilizer on lowering soil pH was counteracted by manure. N application caused decreased extractable P, K, Ca, and Mg while manure application caused increased organic matter, P, Ca, and K levels. Manure did not increase soil Mg.

Low yields should be expected when corn silage is grown on the Panton clay. Both manure and N applications were necessary to obtain maximum yields. Manure application at the rate of 44 metric tons/ha/year was necessary to maintain soil organic matter levels during continuous corn.
Yield, Quality, and Breeding Behavior of Pearl Millet ✕ Napiergrass Interspecific Hybrids1
Authors: Hanna Wayne W. , Monson Warren G.
Published: July 2010

High quality forage production is needed in late summer and fall until frost. The pearl millet (Pennisetum americanum ✕ napiergrass (P. purpureum Schum.) interspecific hybrids have potential for producing high quality forage during this period but more than 1 year's data on a number of hybrids using different female parents is limited. In 1976, 1977, and 1978, 20 pearl millet ✕ napiergrass interspecific hybrids were seeded in the field in a Fuquay soil (Arenic Plinthic Paleudults : loamy, siliceous thermic) and evaluated for dry‐matter yield percent in vitro dry‐matter digestibility (IVDMD), percent crude protein, agronomic characteristics (seed Production, pest resistance, yield distribution), and breeding behavior (effects of male and female parents on dry matter yield). Most of the interspecific hybrids were equal to the best pearl millet hybrids in yield, IVDMD, and protein. In 1977 and 1978, six and two interspecific hybrids, respectively, were significantly (P = 0.05) higher in dry matter yield. One hybrid, Tift 23A ✕ N23, yielded 34 and 27% more dry matter in 1977 and 1978, respectively, than the best pearl millet hybrid. Hybrids with ‘Tift 23A1’ yielded over 25% more dry matter than hybrids with ‘Tift 23D2A1 when the same male parents were used on both female parents. One of the major advantages of the interspecific hybrids is that they produced almost 50% of their forage from after the middle of August until early December.

This study also showed that of the three female parents tested, Tift 23A1 produced the highest yielding hybrids and that much variability for maximizing yield exists among the napiergrass clones used as male parents in the interspecific hybrids.
Thatch Influence on Mobility and Transformation of Nitrogen Carriers Applied to Turf1
Authors: Nelson K. E. , Turgeon A. J. , Street J. R.
Published: July 2010

Thatch frequently exists as part of the edaphic environment of a turfgrass community and thus, should be considered when attempting to determine the fate of topically applied fertilizers in turf. The purpose of these investigations was to determine the influence of a thatch layer on the vertical mobility and transformation of soluble and slowly soluble N carriers following application.

Measurements of N leaching, retention, and volatilization were made using cores of thatch and Flanagan silt loam (Aquic Argiudoll) soil extracted from fieldgrown turf of Kentucky bluegrass (Poa pratensis L.). Urea was selected as the soluble N carrier, and isobutylidene diurea (IBDU) was the slowly soluble N carrier. Application of urea resulted in 2.5 times as much N leaching and correspondingly lower N retention, in thatch than in soil. Where IBDU was used as the N source, leaching from the thatch was reduced from 81 to 5% of the applied N, and leaching from the soil was reduced from 32 to 23% compared to urea‐treated cores. In the volatilization studies, 39% of the applied N from urea was lost as ammonia from thatch cores compared to only 5% from the soil cores. Where IBDU was the N source, little N volatilization (4% from thatch, 2% from soil) occurred. In conclusion, where a substantial thatch layer exists, and turfgrass rooting is largely confined to the thatch layer, use of a slowly soluble N carrier might be preferable over soluble urea for reducing N losses due to leaching and volatilization. As an alternative, effective measures for controlling the thatch may result in greater efficiencies in the use of fertilizer N by the turfgrass community.
Effects of Plant‐Water Stress on Root Distribution of Corn, Soybeans, and Peanuts in Sandy Soil1
Authors: Robertson W. K. , Hammond L. C. , Johnson J. T. , Boote K. J.
Published: July 2010

The efficient recovery by crops of added nutrients and water is influenced by plant rooting characteristics. Published data on the relationship of irrigation water and root distribution of certain crops grown on sandy soils in humid regions are lmited and needed. This field study was a part of an investigation on three soil types to determine the effect of plant‐water stress and irrigation on root distribution of corn (Zea mays L.), soybeans [Glycine max (L.) Merr.], and peanuts (Arachis hypogaea L.). The basic irrigation plan was to replenish the water deficit in only the top 30 to 60 cm of the soil profile. Depth of wetting and the degree of soil water depletion below the irrigated soil layer varied with irrigation frequency and amount of water per application. Although treatments were not the same in the four experiments reported, the major part of the study involved four water management treatments: 1) no irrigation; 2) light, infrequent irrigation; 3) light, frequent irrigation; and 4) medium, infrequent irrigation. Seed yields were obtained at maturity and root length measurements were made at full canopy. Root lengths per unit volume of soil were measured by the Line intercept method. Yields of corn and peanuts increased with total amount of irrigation water used, but there was no yield response to irrigation in the soybean experiment. Peanut and soybean root growth (root length per unit area to a depth of 150 cm) was not affected by water management. In the corn experiments, irrigation increased the length of roots in the 150 cm soil profile. The largest root length value was found in the light, infrequent irrigation treatment. Crops vary in rooting response to plant‐water stress and irrigation strategy. Limited rooting of corn under water stress very likely decreases the efficiency of water and fertilizer use.
Water Status of Cotton as Related to Taproot Length1
Authors: Meyer Wayne S. , Ritchie Joe T.
Published: July 2010

In dryland crop areas it is common for plants to depend on subsoil water for some part of the growing season. In this situation, water moves through a considerable length of root axis to reach the plant top. Resistance to this movement of water (axial resistance) can become significant. This experiment was designed to assess the interaction of root geometry and plant water status and to compare values of root resistance calculated for two contrasting cotton (Gossypium hirsutum L.) root systems. Cotton plants were grown in a greenhouse either in pots (26‐cm‐deep) or in soil‐filled tubes (120 cm‐long) supported in base pots. After initial watering of the soil in tubes, only the base pots were watered, so that plants developed long taproots and depended on water in the base pots.

Except for the strong development of the taproot with in the tube, little other root growth occurred there because of soil drying. The taproots of pot‐grown plants were not well defined 20 cm from the plant base because of extensive branching. Rooting density in the base pot of plants with long taproots was 5.2 ± 0.7 cm cm−3 and compared with 13.7 — 5.6 cm −3 for plants grown in pots. Plants of the two treatments had similar leaf area, rate of water uptake, and value of both covered and exposed leaf water potential. Within the long taproots many secondary xylem vessels had been laid down. Individual xylem vessel size tended to increase with distance from the plant base. Calculated values of axial resistance (0.0097 cm−3 day bar) for long taproot were less than for the taproot of pot‐grown plants (0.0153 cm−3 day bar) because the increase in equivalent xylem vessel size more than offset the effect of the increased length. Values of total root resistance were calculated from the potential difference between covered leaf water potential and soil water potential divided by the water uptake rate. Total root resistance values were similar, and so, by difference, radial root resistance was larger for the long‐rooted plants. This difference is explained by the difference in rooting density. We concluded that a balance was apparently maintained between the absorbing length of the root system and the longitudinal transport system.
Evaluation of Commercial Soybean Inoculants by Various Techniques1
Authors: Hiltbold A. E. , Thurlow D. L. , Skipper H. D.
Published: July 2010

Much of the expanding production of soybeans (Glycine max L.) in the southeastern United States and in other countries is on soils without naturalized populations of Rhizobium japonicum. Effective inoculation is essential where soybeans are planted for the first time. Considering the frequency of inoculation failures and the variety of inoculant products available to growers, research was initiated, to determine relative effectiveness of inoculants and to compare evaluation techniques. Commercial soybean inoculants sold in Alabama in 1976, 1977, and 1978 were evaluated by rhizobial plate counts in two laboratories, most probable number (MPN) determination, greenhouse pot test and acetylene reduction assay, and by field experiments in R. japonicum free soil. Serial dilution and standard plating techniques, along with MPN by soybean nodulation, provided measures of viability in the inoculants. Products were applied in greenhouse and field experiments according to manufacturer's instructions. Nodulation, N fixation, and yield of soybeans were measured relative to numbers of rhizobia applied per seed by various products.

More than 1,000‐fold differences were found among products in viable rhizobia content. Plate counts adequate discriminated products when 107 rhizobia per gram was considered to be the lower limit for acceptability. The close correlation of plate counts and MPN (soybean nodulation) indicated reliability of plate counts despite the difficulty of enumerating rhizobia among numerous contaminants. Nodulation of soybeans in greenhouse and field plantings in soil free of R. japonicum was directly related to the number of rhizobia applied per seed, with no nodulation produced by products supplying fewer than 108 rhizobia per seed, and generally abundant nodulation by products providing 105 to l06 rhizobia per seed. Some products performed poorly despite apparent adequate viability; for example, where a fungicide was added at planting. Various strains of R. japonicum and formulation processes, as well as number of rhizobia applied, may account for differences in nodulating effectiveness. In no case, however, was a product of low plate count found to be an effective inoculant. Plate count provides a relatively rapid, inexpensive evaluation that is supported by other techniques involving soybean nodulation response.
Phosphorus Influx and Growth Characteristics of Corn Roots as Influenced by Phosphorus Supply1
Authors: Anghinoni I. , Barber S. A.
Published: July 2010

Knowledge of the effect of P status of corn (Zea mays L.) plants and P distribution in the toot zone on P influx and root growth is important for simulation modeling of P uptake by corn. Only limited information is available. The objective of this research was to determine the relation between plant P status and the portion of the roots supplied with P on plant P influx and root growth and morphology. Two solution culture experiments were conducted in controlled climate facilities. Phosphorus influx was measured on 18‐day‐old corn plants that had been starved for P for 1 to 6 days. Split‐root experiments were used to measure the effect of P distribution on root growth and P uptake. Starving the plant for P reduced P concentration in the shoot and root and this resulted in a 55% increase in the maximum P influx, Imax. Supplying P to only part of the root system also resulted in a lower plant P concentration and higher Imax by the roots in P solution. When less than 50% of the roots were supplied with P, root growth rate in the P solution was 25% greater than in the minus P solution. Phosphorus uptake was correlated with root surface exposed to P (R2 = 0.88).
Design and Testing of a Microlysimeter for Wetland Rice1
Authors: Tomar V. S. , O'Toole J. C.
Published: July 2010

Assessment of water loss as transpiration and evapotranspiration for each hour or for each day in the field is difficult because the available methods are either very expensive or inaccurate. This paper introduces a simple, sensitive, and accurate microlysimeter for wetland rice (Oryza sativa L.) fields.

The microlysimeter was designed and tested to measure transpiration and evapotranspiration in wetland rice fields. It consists of a poly‐vinyl‐chloride cylinder, sealed at the lower end and connected to a water reservoir/manometer through flexible tubing. A constant water level is maintained in the microlysimeter with a Mariotte system and water loss from the reservoir/manometer is measured. Total water loss as evaporation from free water surface in the cylinder and transpiration from canopy was measured as evapotranspiration. To measure transpiration, the cylinder was covered to stop evaporation from free water surface in the cylinder.

The microlysimeters were laboratory‐calibrated and compared in the field with large square tanks. Water use pattern as evapotranspiration per unit land area was essentially the same with both the units. The microlysimeter is accurate even for time intervals as short as 1 hour and can be fabricated locally.
Comparison of Sprinkler, Trickle, Subsurface, and Furrow Irrigation Methods for Row Crops1
Authors: Sammis Theodore W.
Published: July 2010

Trickle, subsurface, and sprinkler irrigation have been attributed to higher yields and water‐use efficiencies than the conventional furrow irrigation method.

The purpose of this study was to determine the extent to which these irrigation systems could be used to increase water‐use efficiency while maintaining reasonable yields, compared to furrow irrigation, and to determine what effect the frequency of irrigation would have on resulting yields and water‐use efficiency.

Potatoes (Solaneum tuberosum) ‘Kennebec’, and lettuce (Lactuca sativa) ‘GL‐659’ were watered by sprinkler, trickle, subsurface, and furrow irrigation to maintain a minimum soil‐water potential of −20 kPa and −60 kPa.

When potatoes were grown on a Glendale clay‐loam soil (mixed calcareous thermic family of Typic Torrifluvent) at a location where rainfall did not supply a significant portion of their water requirements the highest yield and water‐use efficiency were achieved using a subsurface irrigation system with water applications occurring when the soil‐water potential at the 15 cm depth reached −20 kPa.

When potatoes were grown on a Pedrick sandy‐loam soil (coarse‐loamy, mixed calcareous, Mesic Ustic Torriorthent) and rainfall contributed a significant portion of the water requirements throughout the growing season, the highest water‐use efficiency was obtained with trickle and subsurface systems with water applications occurring when the soil‐water potential at the 15 cm depth reached −60 kPa. Differences in yields at this study site were non‐significant for all irrigation methods.

The subsurface irrigation method appears to offer the best method of supplying uniform soil moisture in the root zone to the plant throughout the growing season, resulting in highest yields and high water‐use efficiencies.

Comparable lettuce yields and water‐use efficiencies were achieved by trickle, sprinkler, and frequent subsurface irrigation treatments due to good stand establishment and avoidance of moisture‐stress conditions. Infrequent sprinkler irrigations reduced yields due to moisture stress. Furrow irrigation, using proper management and short furrow runs, resulted in yields and water‐use efficiencies as high as those of the other irrigation methods. Yield and water‐use efficiency were reduced when flooding of the beds occurred at germination.
Effect of Field Weathering on the Viability and Vigor of Soybean Seed1
Authors: TeKrony D. M. , Egli D. B. , Phillips A. D.
Published: July 2010

The quality of soybean [Glycine max (L.) Merr.] seed at harvest is dependent on the field production environment during development, maturation, and storage on the plant. These investigations were conducted to evaluate the effects of field weathering after physiological maturity (maximum dry seed weight) on seed viability and vigor. Five production environments were compared for two cultivars (‘Cutler 71’ ‐ 1973, ‘Kent’ and Cutler 71 ‐ 1974 and 1975). Seed was hand‐harvested at physiological maturity, harvest maturity (first time the seed dried to less than 14% moisture content), and at regular intervals for up to 3 months after harvest maturity. All seed were evaluated for viability (standard germination test) and vigor (accelerated‐aging germination test).

Physiological maturity occurred at a seed moisture content of approximately 55% for both cultivars. The time interval from physiological maturity to harvest maturity (desiccation period) ranged from 10 to 20 days and was closely related (R2 = 0.88) to the mean open pan evaporation during the period. Seed viability and vigor were highest at physiological maturity and remained high (>80% germination) until harvest maturity for all but one production environment. Viability was maintained at these high levels for 1 to 2 months following harvest maturity for four of five production environments. However, seed vigor declined rapidly, reaching levels that were significantly (α = 0.05) less than those at harvest maturity within 4 to 39 days after harvest maturity. In four of the production environments, seed vigor reached a level of less than 50% germination within 1 month of harvest maturity. The time required for seed vigor to significantly decline following harvest maturity was closely related to mean air temperature (R2 = 0.90), mean minimum relative humidity (R2 = 0.94), and precipitation per day (R2 = 0.75). The wide range in seed vigor observed shortly after harvest maturity emphasizes the importance of timely harvest of seed fields and evaluation of seed viability and vigor soon after harvest.