bluuebunny/crossref_metadata_2025 huggingface dataset:
Procedure for Evaluating the Biological Degradation of Turfgrass Thatch1
Authors: Martin D. P. , Beard J. B.
Published: July 2010

Thatch is a serious problem on intensively maintained turfs. Biological control of thatch would be desirable to eliminate the need for mechanical thatch removal. A controlled in vitro technique was developed for use in assessing the effect of chemical additives and environmental conditions on microbial decomposition of thatch. Pectinase, cellulase, sucrose, and ferulic acid were added to red fescue (Festuca rubra L.) thatch samples in vitro in an attempt to increase thatch decomposition. A sealed environment was maintained at 24 C for 24 hours at which time gas samples were analyzed for CO2, content as an indication of microbial activity. Thatched red fescue turfs were also treated with the same chemical additives in a controlled environment chamber. Increased carbon dioxide evolution occurred in vitro from all four treatments. Total cell wall content decreased in a controlled environment chamber. Environmental studies showed that a pH of 6 resulted in maximum microorganism activity, as measured by carbon dioxide evolution. These results indicate that this technique can be useful in studying microbial decomposition of thatch on turf.
Zinc Response in Corn as Influenced by Genetic Variability1
Authors: Shukla U. C. , Raj Hans
Published: July 2010

Influence of genetic variability on Zn response in recently improved corn (Zea mays L.) genotypes has not been investigated. Therefore, eight genotypes representing indigenous, hybrid, and composite varieties, were evaluated in the greenhouse using a Zn deficient loamy sand soil (Typic Torripsamments) at 0 (original soil), 5, and 10 ppm Zn applied to the soil. Zinc deficiency symptoms, dry matter yield response (6 weeks after sowing), Zn concentration, and P/Zn and Fe/Zn ratios were the criteria for evaluation. There was considerable variation among the eight genotypes in the severity of Zn deficiency symptoms, growth depression, Zn concentration, P/Zn, and Fe/Zn ratios under Zn stress conditions. The depression in shoot and root dry matter yield under Zn stress conditions ranged from 78 to 95 and 72 to 94%, respectively, as compared to 5 ppm supplemental Zn level. Zinc concentration in different genotypes under Zn stress condition varied from 7.4 to 20.5 ppm. The differential response among the genotypes was found to be associated with their capability to exploit soil Zn and/or translocate it to the shoot. The contribution of P/Zn and/or Fe/Zn balance in tissues to the variability in Zn responses was not significant.
Root Elongation along a Soil‐Plastic Container Interface1
Authors: Voorhees W. B.
Published: July 2010

Root growth is often studied in glass‐fronted containers which allow continuous observation of several growth parameters. These observations are generally assumed to extrapolate to root growth under field conditions. However, laboratory studies reported here show that root elongation rates along a soil‐container interface in soil cores are significantly lower than those measured within the bulk soil mass. These differences are probably due either to higher soil strength at the interface or to an attracting electrical charge on the container surface, or both.
A Rainout Shelter Installation for Studying Drought Stress1
Authors: Arkin G. F. , Ritchie J. T. , Thompson M. , Chaison R.
Published: July 2010

To eliminate the effects of erratic rainfall, which have limited field studies on drought stress, we designed and constructed a relatively large (12.2 ✕ 12.2 m), lightweight shelter that prevents rain from falling on a field plot area. The design overcame previous rainout shelter size limitations and permitted the reduction in the size of the power and drive assemblies needed and thus decreased construction costs. The design of the rainout shelter installation allows lengthening the shelter, controlling the water table, and collecting and storing rain water for irrigating the test area (beneath the shelter). The shelter is large enough to permit operation of planting and tillage equipment. Available soil water in the test area was effectively controlled during the 1974 growing season.
Evaluation of an Electronic Foliometer to Measure Leaf Area in Corn and Soybeans1
Authors: Hatfield J. L. , Stanley C. D. , Carlson R. E.
Published: July 2010

Known areas were measured with an electronic foliometer to determine the errors involved with this instrument. Good agreement between measured and known areas was found and there was high accuracy and precision for both the conveyor belt and sheath method. Tests were made comparing the foliometer, a planimeter, and maximum length times maximum width (LW) for soybeans and comparing foliometer and LW for corn. There was close agreement between planimeter and foliometer measurements for soybeans (r = 0.99). The foliometer compared favorably with LW for corn (r = 0.96). Coefficients for converting LW measurements to leaf areas were determined for soybeans and three corn hybrids.
Water Use by Dryland Corn as Affected by Maturity Class and Plant Spacing1
Authors: Alessi J. , Power J. F.
Published: July 2010

Very early maturing hybrids of corn (Zea mays L.) have become available recently and appear to be adapted to semiarid regions. Water use information is needed for these hybrids. The purpose of this study, at Mandan, N.D., was to evaluate the effects of maturity class of corn hybrid and of plant spacing on water utilization under dryland cropping. In each of 3 years, 68 and 85‐day relative maturity class hybrids were grown at plant populations of 20, 30, 40, 60, and 74 thousand plants/ha in 50 and 100‐cm rows on Temvik silt loam (Typic haploboroll). The 20, 40, and 74 thousand plant populations were monitored for changes in soil water content by the neutron method both in the row and midway between rows. Neither row spacing nor location of the access tube in respect to the row had an appreciable effect upon soil water content at any sampling date. Water withdrawal by corn was generally confined to the upper 90‐cm soil depth, regardless of treatment. Increased population usually increased water use during vegetative growth, leaving less water for reproductive growth. Hybrids and row spacings had less effect upon water use. Except for dry matter production by the 85‐RM hybrid at the highest population, water use efficiency (WUE) was greatest at a population of 40,000 plants. While the early maturing hybrid was efficient in using water for grain production, the later maturing hybrid used water more efficiently for forage production. Results of regression analysis between yields and water use suggest that the earlier maturing hybrid would be less affected by severe drought than would the later hybrid.
Water Transport From Roots to Soil1
Authors: Molz Fred J. , Peterson Curt M.
Published: July 2010

Numerous studies have indicated that water can flow from roots to soil (negative direction) but little can be concluded about the magnitude of such a flow. Therefore, experiments were performed on potted cotton plants (Gossypium hirsutum L. ‘Auburn 7‐683’) to compare the magnitude of water transport in the positive (soil to roots) and negative directions. Experimental results were also compared qualitatively with the predictions derived from mathematical models simulating root water uptake. Each plant was left unwatered in an environmental chamber to dry the soil from field capacity to near the —15 bar percentage. After drying, the stem was severed under water and the resulting water flow from roots to soil recorded by weight changes. Results indicated that water flow in the negative direction is small (1:36 during a 110‐hour period) compared to flow in the positive direction. This difference is thought to be due to a hysteretic, unsaturated, and possibly non‐Darcian flow phenomenon or to the generation of growth‐related water potentials. Contemporary mathematical water extraction models ignore both phenomena and, therefore, would be expected to overestimate flows in the negative direction if “calibrated” to predict correctly flows in the positive direction.
Higher Fatty Acid Composition of Immature Forages as Affected by N Fertilization1
Authors: Mayland H. F. , Molloy L. F. , Collie T. W.
Published: July 2010

High levels of both N and total higher fatty acids (HFA) in forage have been associated with increasing the grass tetany hazard to grazing cattle. The objective of this study was to determine the relationship between forage N, total HFA, and HFA species distribution in several forages.

Forage N, HFA, HFA species concentration, and total chlorophyll were determined in immature vegetative growth of Agropyron desertorum (Fisch.) Schult., Cynodon dactylon L., Lolium perenne L., Trifolium repens L., and Triticum aestivum L. established with soil fertility levels up to 500 ppm N in the growth chamber. Forage HFA concentrations were positively and linearly related to forage N levels, but regression coefficients were not the same for all species. The HFA concentrations were as high as 16 mmol COOH/100g DM at 6% total N in first cutting Lolium perenne L. The relative HFA species distribution was the same within a given forage, even though total N concentrations ranged from 2 to 6%. The mean HFA specie concentrations (determined by gas‐liquid‐chromotography relative to mean total HFA concentrations determined by titration) when expressed as percent for the grasses were: C14:0 — 2%, C16:0 — 13%, C16:1 — 1%, C18:0 plus C18:1 — 1%, C18:2 —11%, and C18:3 — 67%. The total HFA concentrations were positively correlated with chlorophyll a + b concentrations which was expected, since the HFA of green plants is largely associated with chloroplast membrane.
Response of Soybean Cultivars to Narrow Rows and Planting Rates Under Weed‐free Conditions1
Authors: Cooper R. L.
Published: July 2010

With continued development of new and better herbicides for chemical weed control in soybeans, the potential exists for growing soybeans in very narrow rows (17 cm) without cultivation. The objective of this research was to examine the potential yield of soybeans [Glycine max (L.) Merr.] in 17‐cm rows under weed free conditions and also to determine the optimum seeding rate and relative yield of this row width compared to greater row widths.

Up to nine cultivars were grown in three different row widths and at five different populations in field plots in central Illinois over a period of 6 years. When seeding rate was low enough to prevent lodging, yield advantages of 10 to 20% (3 to 6 q/ha) were obtained from planting in 17‐cm rows compared to 50‐ or 75‐cm rows. Earlier maturing cultivars tended to be more responsive to 17‐cm rows, and under high yield conditions and irrigation, 30 to 40% (9 to 12 q/ha) yield responses were observed with one of the more responsive cultivars. The combination of early cultivars in 17‐cm rows provided the highest absolute yields. A seeding rate of 37.5 viable seeds per m2 was near optimum for most cultivars and for all three row widths tested. These results suggest that if an effective weed control program can be developed to control weeds in soybeans without cultivation, there would be a significant yield advantage from planting soybeans in 17‐cm rows.
Healing Potential of Creeping Bentgrass as Affected by Nitrogen and Soil Temperature1
Authors: Hawes D. T. , Decker A. M.
Published: July 2010

Maintenance of creeping bentgrass putting greens in the transition zone between the northern cool season grass region and the southern warm season grass region is difficult during July and August due to high temperatures. A management study on soil temperature plots with several N sources and levels was thought to be a suitable method of finding solutions to this maintenance difficulty. This paper reports the effects of N levels and temperature on what we have chosen to call healing potential.

‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) was maintained on field soil temperature plots with target temperatures of 32, 21, ambient and 10 C. The soil was a Sassafras silt loam (Typic Hapludults). Response to N from two sources was compared at three levels in five fertilizer treatments. The healing potential of the turf was determined by visually estimating the 3‐week growth of stolons from the surrounding turf as percent cover that developed into a 4.8 cm diameter bare area. Healing potential was compared with clipping yields which were taken from sub‐plots (N sources).

Healing was best under conditions of warm temperatures (ambient, 21 and 32 C) and high N levels for three dates in June and July. However, an adverse effect of high N was found at the 32 C soil temperature for three dates in August. Healing potential was closely related to clipping yield. Their linear correlation values ranged between + 0.82 and + 0.92. Clipping yields were found to be a good indicator of the healing potential of creeping bentgrass turf.
Fall‐ vs. Spring‐applied Sulfur‐coated Urea, Uncoated Urea, and Sodium Nitrate for Corn1
Authors: Frye W. W.
Published: July 2010

The practice of applying fertilizer in the fall for crops grown the next summer is advantageous to the fertilizer manufacturing and marketing sector as well as saving time for farmers in the spring planting season. Sulfur‐coated urea (SCU), NaNO3, and uncoated urea were applied in field experiments during 1972‐74 to compare their efficiency in fall application with spring application for the production of corn (Zea mays L.) grain on a Mountview silt loam soil (Typic Paleudult, fine silty, siliceous, thermic) at Cookeville, Tenn. Two dissolution grades of SCU were compared with NaNO3 and uncoated urea, at rates of 112 and 224 kg N/ha in 1972‐73 and 168 and 224 kg N/ha in 1974. Grain yields were measured and relative efficiency of fall application and response to rates, sources, and dates of application were calculated. Soil concentrations of ammonium and nitrate N were measured on some treatments. Soil temperature at 10 cm depth was recorded during the winter and early spring of 2 years.

There were little or no differences in corn grain yields between fall and spring applications of N at the 224 kg/ha rate. At the lower N rates, spring‐applied N increased yields compared to fall‐applied N. The relative efficiency of fall compared to spring application of the materials, averaged for 3 years, was 0.52 and 0.86 for NaNO3 at 112 and 224 kg N/ha respectively, 0.49 and 0‐95 for uncoated urea, 0.80 and 1.10 for SCU‐1, and 0.72 and 1.03 for SCU‐2. Nitrates leached to a depth of 45 cm or more during the winter and early spring in plots treated with NaNO3 and uncoated urea. Conditions were probably favorable for a slow but significant dentrification rate at times during the winter and early spring, leading to the belief that dentrification may have caused some of the decreased efficiency of fall‐applied N.

Although SCU was more effective than NaNO3 or uncoated urea, fall‐applied N from any fertilizer source would be less effective on subsequent spring and summer growth than spring‐applied N under similar soil and climate conditions.
Role of Changes in Solute Concentration in Maintaining Favorable Water Balance in Field‐Grown Cotton1
Authors: Cutler J. M. , Rains D. W. , Loomis R. S.
Published: July 2010

Cotton (Gossypium hirsutum L.) shows various adaptive responses to water deficits, including alterations in cellular osmotic concentrations. The role of changes in solute concentration in maintaining favorable water balance in field‐grown cotton was evaluated under wet and dry irrigation treatments. The experiments were conducted with a fine loamy mixed, calcareous thermic‐Typic Torriorthents soil in a semi‐arid environment. Leaf diffusive resistance, measured by a resistance porometer, was unaffected by leaf water potential (down to −29 bars in adapted leaves of the dry treatment) while the typical response to light was maintained. Leaf blade elongation rate was less in plants with low leaf water potential. The rate was maximal in the early evening and depressed during the midday water potential minimum and at night. Some blade enlargement occurred during time intervals when leaf water potentials were as low as −19 to −23 bars. The osmotica of primary importance in cotton leaves were K, nitrate, citrate, malate, and sugars; K and other soluble inorganic leaf constituents did not vary diurnally or with plant status. In contrast, sugar and malate concentrations (expressed on a dry weight basis) were 20 to 60% greater in leaves from the dry treatment than in leaves from the frequently irrigated treatment. In addition, diurnal variations in sugars and malate followed the variation in leaf water potential, with a slight lag, and a simple model of leaf osmotic relations suggested that these accounted for 10 to 40% of the diurnal changes in the calculated osmotic potential. A diurnal hysteresis of as much as 7 bars was observed in the relation between water potential and relative water content due largely to changes in the elasticity of cell walls. We conclude that the maintenance of low leaf diffusive resistance and continued leaf elongation despite reductions in leaf water potential indicates that turgor is also maintained. This was due partly to the accumulation of sugars and malate and partly to high cell wall elasticity.
Aluminum Tolerance of Soybean Cultivars Based on Root Elongation in Solution Culture Compared with Growth in Acid Soil1
Authors: Sartain J. B. , Kamprath E. J.
Published: July 2010

Growth of soybean [Glycine max (L.) Merr.] roots into acid subsoils and utilization of subsoil moisture is limited in many soils of the southeastern U. S. because of Al toxicity. Laboratory and greenhouse experiments were conducted to obtain information on tolerance of soybean cultivars which would be helpful in selection of cultivars best adapted to acid subsoils. Root elongation measurements were made of 18 cultivars exposed for 48 hours to solutions containing 0, 0.25, 0.50, and 1.0 ppm Al and 10 ppm Ca. Eleven of the cultivars were selected for a greenhouse experiment in which plants were grown in a Lynchburg soil (Aerie Paleaquult) at 81 and 4% Al saturation. Measurements were made of top growth, root length, and the Ca, P, and Al concentrations of the plant tissue. Of the 11 cultivars used, ‘Lee’, ‘Lee 68’, ‘York’, ‘Ogden’, and ‘Dare’ were judged to be relatively Al tolerant according to the short term root elongation studies. Based on absolute top growth in the 81% Al saturated soi1 or relative top growth in the 81% Al saturated soil as compared with the 4% Al saturated soil the cultivars Lee, ‘Bragg’, ‘Pickett 71’, and York were more tolerant of Al than the other cultivars.
Zinc Nutrition of Rice as Influenced by Rates of Gypsum and Zn Fertilization of Alkali Soils1
Authors: Takkar P. N. , Singh Tarjit
Published: July 2010

Three field experiments were conducted on Zn deficient alkali soils, two on Natraquic calciorthids, and one on Aquic Camborthids, to determine the effect of gypsum and Zn fertilization alone and in combination on the Zn nutrition of rice IR 8 (Oryza sativa L.). Three rates of gypsum (0, 25, and 50% gypsum requirement of soil) and three rates of Zn (0, 11.2, and 22.4 kg Zn/ha, as ZnSO4‐7H2O) and their possible combinations were tried. At all the three locations, the growth of the rice crop was very poor and exhibited Zn deficiency symptoms in control plots. The yield and Zn uptake was higher in alkali soil high in CaCO3 and low in pH than in soils low in CaCO3 and high in pH. Gypsum application markedly decreased the soil pH, and significantly increased the yield and Zn uptake by rice. This resulted from a marked significant increase in soil and plant Zn concentration, though it remained within marginal levels. Zinc application decreased the pH, but not so appreciably as did gypsum; and markedly increased the available Zn from deficient to adequate levels. This in turn significantly increased Zn concentration and its uptake and resulted in a significant increase in rice grain and straw yield both over control and gypsum treatments. Optimum response of rice to Zn was observed at 11.2 kg Zn/ha except in one of the Natraquic calciorthids where it was 22.4 kg Zn/ha. Gypsum in conjunction with Zn application did not increase either the available Zn or the rice yield. The beneficial effect of Zn application to rice grown on the alkali soils under investigation was far more than that of gypsum.
Animal Preference, Nutritive Attributes, and Yield of Pennisetum flaccidum and P. orientale1
Authors: Burns J. C. , Timothy D. H. , Mochrie R. D. , Chamblee D. S. , Nelson L. A.
Published: July 2010

Warm‐season perennial grasses can make an important contribution to animal enterprises by providing forage for summer grazing. In the transitional belt, however, where cool and warm‐season grasses are used during the grazing season; both are hampered by periods of belownormal growth and frequently only the warm‐season species are available during midsummer. Six Pennisetum accessions initiated growth earlier in the spring in North Carolina than traditional warm‐season grasses, and continued growing through summer and into the fall until killed by frost. The objectives of this study were to evaluate these accessions for acceptance by free‐grazing animals, nutritive attributes, dry matter yield, and persistence. Plantings were made on a loam soil (Typic Hapludult, in the Clayey, Kaolinitic, Thermic family). Five accessions of Pennisetum orientale Rich (from India) and one selection of Pennisetum flaccidum Griseb. (from Afghanistan) were evaluated in one experiment (2 year study) for animal preference and associated nutritive value. Animals grazed all selections (each time forage reached 46 to 61 cm) but consistently preferred (P ≤ 0.01) P. flaccidum. In vitro dry matter disappearance (IVDMD) differed significantly among selections, but rank was not consistent from year to year. IVDMD ranged between 63.1 and 70.4%. Ranges for neutral detergent fiber (NDF) were: 55.0 to 57.9%; for acid detergent fiber (ADF), 28.5 to 34.1%; for lignin, 2.66 to 4.48%, and for N 2.95 to 3.78%. In a separate trial, dry matter yields (3‐year avg.) of the five P. orientale selections under a “short cut” regime (46 to 74 cm high cut to a 15‐cm stubble) were 7,948 kg/ha and for “tall cut” regime (76 to 102 cm tall cut to a 15‐cm stub ble) 12,393 kg/ha. P. flaccidum averaged 8,958 and 12,003 kg/ha for short cut and tall cut, respectively. Yields exceeded 15,700 kg/ha for several of the P. orientale selections managed under the tall cut regime. P. flaccidum produced more of its seasonal yield earlier (91% by 25 July) than did the P. orientale selections (only 77% by 25 July). The nutritive attributes of these forages were appreciably reduced by maturity. Mean values for the five P. orientale selections for the short and tall cut regimes and for P. flaccidum for each harvest regime respectively, were as follows: IVDMD 48.4, 44.0 and 54.7, 54.5%; NDF 61.4, 65.4 and 60.5, 61.1%; ADF 32.8, 35.8 and 33.9, 32.9%; lignin 3.07, 3.84 and 3.67, 3.30%; and N 2.39, 1.77 and 2.44, 2.13%. The Pennisetum accessions evaluated have potential as forage species in the southeastern U.S. In addition to their long growing season and high yield potential, their NDF concentrations were low compared with Coastal bermudagrass (Cynodon dactylon L.). This was especially noticeable in the more mature harvests. Such low fiber concentrations may contribute to an increased dry matter intake by grazing animals.
Photosynthetically Active Radiation, CO2 Uptake, and Stomatal Diffusive Resistance Profiles Within Soybean Canopies1
Authors: Hatfield J. L. , Carlson R. E.
Published: July 2010

Profiles of PPFD (photosynthetic photon flux density), CO2 uptake and stomatal diffusive resistance were measured in field‐grown canopies of Hark and Rampage soybeans [Glycine max (L.) Merr.]. These studies were conducted to examine and quantify the relationships between these parameters over the daylight period for discrete canopy stratum and the complete canopy. Measurements were made in the field with soybeans grown on a Huntsville silt loam. CO2 uptake was measured with a field portable 14CO2 leaf exposure chamber, PPFD with a quantum sensor attached perpendicularly to the chamber and stomatal resistance with a diffusion porometer. Each of the measurements was made within four strata of both canopies at various growth stages and under varying atmospheric conditions. Canopy distributions of CO2 uptake showed that most photosynthate was produced in the upper 20% of the canopies. This is approximately one‐third of the total canopy LAI (leaf area index) and represents the level of 90% interception of incident photosynthetically active radiation. Regression analyses of the relationship between PPFD and CO2 uptake produced a linear model, and the slope of the line was dependent upon the day. The variation between days was caused by environmental conditions, which reduced CO2 uptake by increased stomatal diffusive resistance. These reductions in CO2 uptake were caused by soil moisture stress and cold temperature shock. Hark exhibited the greater CO2 uptake rates and also the largest reduction in uptake with increased stomatal diffusive resistance. Stomatal diffusive resistance profiles showed an increase with canopy depth in both cultivars; this was attributed to low PPFD. Major photosynthetic production by soybean canopies occurs in the upper portion of the canopy and further understanding of the relationship between canopy behavior and the environment may lead to increased crop production.
Evaluation of Commercial and Experimental Three‐Way Corn Hybrids for Aflatoxin B1 Production Potential1
Authors: Widstrom N. W. , Wiseman B. R. , McMillian W. W. , Kwolek W. F. , Lillehoj E. B. , Jellum M. D. , Massey J. H.
Published: July 2010

Climatic conditions in the southeastern U.S. frequently favor infection by Aspergillus flavus Link ex Fr. and subsequent aflatoxin production on preharvest corn (Zea mays L.). Plant resistance to infection and toxin development in corn may be an important factor in reducing toxin levels. Ten full‐season and 10 short to mid‐season commercial corn hybrids from three locations in the Coastal Plain Region of Georgia were evaluated for aflatoxin concentration from natural infection by Aspergillus spp. over a 3‐year period. A higher incidence of aflatoxin positives and higher concentrations of toxin occurred at the Tifton, Georgia, location than at the Plains or Midville locations. Corn from plots infested with corn earworm, Heliothis zea (Boddie), had higher levels of toxin contamination than samples from noninfested plots. Significant differences for aflatoxin concentration occurred among the commercial hybrids sampled, but differences were not detected among dent or sweet corn inbreds tested as three‐way crosses. The lack of differences was generally attributed to insufficient replication and the possibility that the common single‐cross tester(s) had an extraordinary influence on aflatoxin production potential. Evaluation and selection for plant resistance to infection by A. flavus and aflatoxin production will probably be difficult.
Critical Boron Concentrations in Plant Tissues of Two Sunflower Cultivars1
Authors: Blamey F. P. C. , Mould Diana , Chapman J.
Published: July 2010

Marked responses of sunflowers (Helianthus annuus L.) to boron fertilization have been recorded but little information exists on the B nutritional requirements of this crop. In order to study this aspect, field trials were conducted in which five rates of B fertilizer (0 to 4 kg B/ha) were applied to two cultivars, ‘Smena’ and ‘SO 320’, on two soil types. The cultivars differed in visual susceptibility to B deficiency in the vegetative stage but differed only slightly in B uptake. B fertilization increased seed yields by an average of 48% in both cultivars. To establish critical B concentrations in plant tissues, relationships were investigated between seed yield and the B concentrations in I‐mo‐old seedlings and in the topmost mature leaf at flowering. Seedlings proved unsatisfactory as index tissue, particularly with SO 320, but meaningful relationships were recorded between seed yield and B concentration in the topmost mature leaf at flowering in both cultivars. Critical concentrations in this tissue were determined as 32 and 35 ppm B for Smena and SO 320, respectively. No significant differences were recorded between the two cultivars in the relationship between seed yield and the B concentration in the leaf below the critical levels, and the data were combined. The critical concentration in the topmost mature leaf at flowering was determined as 34 ppm B for both cultivars, the confidence interval (95%) being from 31 to 38 ppm B.
Simulation of Soil Water within the Root Zone of a Corn Crop1
Authors: Radcliffe D. , Hayden T. , Watson K. , Crowley P. , Phillips R. E.
Published: July 2010

Knowledge of the distribution and movement of soil water in the root zone of a row crop is important in farm and watershed management, and in research on the transport of soil nutrients and pollutants. The objective of this study was to develop a model that would calculate the infiltration, evaporation, transpiration, and deep drainage of soil water in the root zone of a corn (Zea mays L.) crop throughout a growing season, using readily obtainable climatic data as daily inputs. The model differed from existing models in that the effect on the distribution of rainwater due to channeling in the cracks and non‐capillary pores of a highly structured soil was considered. This distribution was obtained by adapting equations used to describe analagous distributions in ion exchange chromatography. Two methods of modeling plant uptake of soil water were compared. An empirical approach assumed that the plant took water from the layer in the root zone with the lowest energy level (determined four times daily) and the amount taken was given by a curve that related the ratio of actual and potential transpiration to the water content at that level. A mechanistic approach, similar to that used by Nimah and Hanks in 1973, considered root distribution, hydraulic conductivities, plant resistance, and root‐soil contact resistance.

The model was tested using seasonal soil moisture records from 4 years on one soil and a single year on a second soil. Mean squared error of prediction for the seasons ranged from 0.05 to 0.15%. Use of the partial displacement infiltration component improved the accuracy of the results in all but one trial. The two methods of modeling plant uptake of soil water, mechanistic and empirical, differed very little in accuracy.
Nitrogen in the P Band for Forage Establishment1
Authors: Sheard R. W.
Published: July 2010

Band seeding, a recommended practice for forage establishment, increases seedling growth primarily because of early P uptake. Ammonium N (NH4+) has been demonstrated to increase P uptake with several crop species. The objective of the experiments reported herein was to determine if the inclusion of N as NH4+ in the P band would result in a further increase in the seedling weight of forage species.

Five field experiments were conducted on a Typic Hapludalf soil using hand placement of the fertilizer band and seed in 1 m rows of alfalfa (Medicago sativa), bird'sfoot trefoil (Lotus corniculatus), and bromegrass (Bromus inermis). Monocalcium phosphate, labelled with 32P, was placed in a band 5 cm directly below the surface placed seed with NO3‐ supplied as Ca(NO3)2 or NH4+ supplied as (NH4)2 SO4. Dry weight per plant, total uptake of P and uptake of fertilizer P were measured 5 weeks after seeding.

Band seeding up to 30 kg P/ha increased seedling growth as much as five‐fold in all experiments regardless of species or soil test level for P. Consistent evidence that NH4+ was increasing the concentration and/or uptake of fertilizer P and hence the concentration and/or uptake of total P by forage species was not established. In one experiment, up to 52% greater seedling growth of alfalfa, in addition to that obtained with P alone, was obtained by including NH4+ in the band in contrast to a 20% increase with NO3‐. In a second experiment, inclusion of N in the band increased growth by 11% without a preference for the form of N. Using 32P techniques one of two experiments showed the increased growth associated with the N applications was due to enhanced fertilizer P concentration and uptake, and hence increased total P uptake resulting from including the NH4+ nitrogen in the P band. It is concluded that NH4+ in the P band is of minor importance for increasing early seedling growth of cool season forage species.
Residual Effects of Dairy Cattle Manure on Plant Growth and Soil Properties1
Authors: Lund Zane F. , Doss Basil D.
Published: July 2010

Land spreading of dairy manure is effective both in disposing of waste and in utilizing plant nutrients in the manure. This study was conducted to determine the residual effect of manure after three annual applications at rates of 0, 22.5, 45, 90, 180, and 270 metric tons/ha were each incorporated into two soils. Plots were double‐cropped each of those 3 years with pearl millet [Pennisetum americanum (L.) K. Schum ‘Gahi I’] and rye (Secale cereale L. ‘Wren's Abruzzi’). During the residual phase of the experiment, plots were double‐cropped with rye and corn (Zea mays L. ‘Funks 5757’) for a period of 4 years. Residue from high application rates of dairy cattle manure increased yields of corn on both Dothan loamy sand (Plinthic Paleudults) and Lucedale sandy loam (Rhodic Paleudults) for 4 years after the manure was applied. On the Dothan soil high rates of manure adversely affected rye growth. Most years, the residue increased N uptake in both crops on both soils. The high rates of manure increased pH to a depth of over 100 cm on the Dothan soil. Potassium accumulated in the subsoil to the 100‐cm depth. Phosphorus was increased to the 60 to 75‐cm soil depth. Magnesium also moved into the subsoil, but there was little movement of Ca below the surface 30 cm. The effect on pH, K, P, and Mg movement was much smaller on the Lucedale soil than on the coarser‐textured Dothan soil.

The high rates of manure increased soil pH and soil contents of K, Mg, and P and increased the cation exchange capacity of soils. These factors contribute toward higher crop yields on manure‐treated plots. Response to dairy manure may be measured for 4 years or more after high rates of manure applications have been stopped.
Osmotic and Specific Salt Effects on Growth of Cotton1
Authors: Thomas J. R.
Published: July 2010

Studies of plant response to a saline environment are generally performed using nutrient culture techniques or on soils artificially salinized with a single salt or a salt mixture, usually NaCl and CaCl2. The soil is frequently irrigated to maintain a low matric suction, in contrast to the multiple salt system and variable soil water content encountered in normal field conditions. The objectives of this study were to determine the effects of seasonal changes in water availability on growth and ionic composition of cotton (Gossypium hirsutum L.) and the relative importance of water stress and ion accumulation on growth under field conditions. Plots were established on the saline and non‐saline phases of Raymondville clay loam (Vertic Calciustolls). Total soil water suction (TSWS), osmotic suction of root zone (OS), plant height, and leaf mineral composition were determined periodically on each plot through the growing season. Cotton stem elongation decreased with increasing TSWS, and ceased as TSWS approached 12 bars. Regression coefficients suggested that an increase of 1 bar in the TSWS decreased growth by 3.4 and 0.9 cm, respectively, during the 70 to 85 and the 85 to 115‐day growth periods. However, plant size differences at the same TSWS suggested that growth depression on the saline soil was related to ionic composition effects in addition to an osmotically. induced water deficit. The Ca, Mg, and Na concentration of the cotton leaves increased significantly as TSWS increased, whereas K was not affected. Consequently, the K/(Ca+Mg) ratio decreased as OS and TSWS increased. The Cl concentration of the cotton leaves increased with increasing TSWS. On day 85, the leaf Mg concentration and OS were almost equally correlated with plant size. Later in the season (115 and 128 days after planting), plant size was significantly related to the OS and Na concentration of the leaves. The results indicated that plant analyses could be used to separate the specific nutritional effects from the osmotic effects on growth in a saline environment.
N‐Source and Irrigation Effects on Nitrate Leaching1
Authors: Bauder J. W. , Montgomery B. R.
Published: July 2010

abstract

Efficiency of N fertilizer sources and N leaching below the root zone of irrigated crops are concerns of agronomists and environmentalists alike. Practical data comparing the efficacy and leaching susceptibility of various N sources are necessary for resource management and as input to current nutrient transport models. This study was conducted to evaluate the effects of N fertilizer source and irrigation management on distribution of N and on leaching of NO3−‐N within the root zone of a small‐grain crop.

Undisturbed columns of Maddock fine sandy loam, a well‐drained Udorthentic Haploboroll, were ciopped to wheat (Triticum aestivum L. cv. 'Era') in a greenhouse study. Three N source, Ca(NO3)2, (NH4)2SO4, and CO(NH3)2, and a check treatment were compared in factorial combination with two irrigation levels. Nitrate and NH4+‐N concentrations in leachate were measured throughout the study. Total‐N and NO3−‐N in the soil columns were measured at harvest. Percolation from the columns was the same for all treatments. Essentially, none of the applied N leached below the rooting depth as either NH4+‐N or NO3−‐N. Maximum depth of NO3−‐N leaching, which was approximately 60 cm, occurred with Ca(NO3)2 and high volume‐low frequency irrigations. No NO3−‐N accumulated below 20 cm when (NH4)2SO4, and CO(NH2)2 were applied, followed by low volume‐high frequency irrigations. Total amount and depth of NO3−‐3‐N leached were dependent on irrigation method and N source. High volume‐low frequency irrigations leached solutes to a greater depth than did low volume‐high frequency irrigations. Contribution of N source to NO3−‐N leaching was generally CO(NH2)2≤ check<(NH4)2S04<Ca(NO3)2, although NO3‐N leaching from urea treatments may have been offset by ammonia volatilization following treatment applications. Nitrate leaching from N fertilizers under irrigation may be minimized by timely applications of ammonia based fertilizers and low volume irrigations to minimize leaching below the crop root zone.
Planting Sugarbeets to Stand when Establishment is Erratic1
Authors: Winter S. R.
Published: July 2010

Planting sugarbeets (Beta vulgaris L.) to stand is desirable if yields can be maintained. Low seeding rates eliminate the need to thin; however, yield and quality suffer if harvest stand is low. Sugarbeet stand establishment is erratic on the Southern High Plains. Therefore, planting to stand has been assumed to be unworkable. These studies were undertaken to determine the feasibility of planting to stand where establishment is erratic.

Sugarbeets were planted to stand at a wide range of seeding rates and compared to an overplanted, handthinned check. Rows were 76‐cm apart on Pullman clay loam (fine, mixed, thermic Torrertic Paleustolls order Mollisol). Yield and harvest loss were determined on the center two rows of four‐row field plots with commercial harvesting equipment.

Establishment of planted seed ranged from 31 to 63% and averaged 46%. Harvested mot yield and percent sucrose were reduced if harvest stand fell below four . More than 10.0 plants/m reduced root yield thin stands, less in thick stands, and least in near optimum stands (five to seven plants/m). Optimum seeding rate depended on establishment conditions; however, results were consistently good when planting to stand at 16.7 seeds/m of row. At this seediing rate, harvested sucrose yield ranged from 94.5 to 100.2% and averaged 97.8% of the hand‐thinned check. Thus, sugarbeets were successfully planted to stand even with low and erratic establishment. Planting sugarbeets to stand should be successful in other areas. The key to success is using a seeding rate high enough to guard against the lowest commonly expected establishment.
Root Length Measurement with a Computer‐Controlled Digital Scanning Microdensitometer1
Authors: Voorhees W. B. , Carlson V. A. , Hallauer E. A.
Published: July 2010

Root length measurements are often neglected in research because of the time and labor involved. A technique is described that greatly facilitates measuring root length using a computer‐controlled digital scanning microdensiometer. This equipment systemically scans a photographic image of the roots and assigns numerical values to the light brightness from small areas of the image. These digitized light brightness values are used to determine the number of intersects between plant roots and a scanning line. The number of intersects is linearly related to root length. Resolutions of 1 µm can be obtained with photographic enlargement or microscopic lens. Calibration is obtained by scanning photographic images of known lengths of string, with a calibration regression coefficient for a linear fit > 0.98. A photographic image can be scanned three times in less than 5 sec and root length estimated with a coefficient of variation of < 5% among the three replicated scans. Computer programming, digitizer adjustment, and photographic modification can be used to adjust for different types of root systems.
Mammoth Genotypes and Tobacco Management Regimes for Reduced Production of Downstalk Tobaccos1
Authors: Wernsman E. A. , Matzinger D. F.
Published: July 2010

Demand for flue−cured tobacco (Nicotiana tabacum L.) from basal leaf positions has decreased in recent years, and production systems which maximize higher quality, upstalk, leaf grades are needed.

In this study we tested production regimes utilizing photoperiod−sensitive genotypes to prevent flowering and produce additional upstalk leaves as a substitute for discarded basal leaves.

Normal and photoperiod−sensitive (mammoth) versions of four cultivars were grown in field experiments at two locations in 2 years. Apical meristems of mammoth genotypes were removed when plants had produced the same number of leaves as normal cultivars, four leaves more than normal in 1977, and two leaves more than noma1 in 1978.

Mammoth genotypes allowed to produce the same leaf number as normal cultivars provided higher yields, with leaf quality equal or superior to the controls. Total alkaloids were lower than in normal cultivars in 1977, but equal in 1978. Reducing sugar contents were equal in both types in 1977, but significantly higher for mammoths in 1978.

Permitting mammoth plants to produce four more leaves than normal, with the bottom four leaves removed from the plants and discarded, resulted in yield overcompensation with slight reductions in leaf alkaloids and increases in reducing sugars. Two additional top leaves on mammoth entries did not compensate adequately for yield reductions caused by discarding the bottom four leaves. Leaf alkaloids and sugar contents in the latter production regime did not differ from those of control cultivars.

These regimes could reduce the production of downstalk tobaccos without significant yield reductions and would eliminate all premature flowering. The maintenance of apical dominance in mammoths would enhance axillary bud control.
Nodulation and N Fixation of Field‐Grown California Cowpeas as Influenced by Well‐Irrigated and Droughted Conditions1
Authors: Zablotowicz Robert M. , Focht Dennis D. , Cannell Glen H.
Published: July 2010

The cowpea, (Vigna unguiculata (L.) Walp.), is considered a drought‐tolerant legume. The N fixation process, however, is sensitive to water stress. This study was conducted to describe the development of nodulation and N fixation of field‐grown Californian cowpeas as influenced by stage of growth and drought. California No. 5 blackeyes were evaluated for nodulation and N fixation (as measured by acetylene reduction assay) utilizing four strains of Rhizobium sp. applied as seed inoculum. Two water regimes were utilized in this study: 1) the well‐watered regime was irrigated when the soil matric potential reached ‐0.6 bars at a depth of 20 cm, 2) the droughted regime received sufficient irrigation to allow good seed emergence, followed by a 42‐day period free of rain or irrigation. Maximum nodulation of 175 mg/plant was observed at flowering in the well‐watered plots versus 15 mg/plant in the droughted plants. Following this development stage, there was no significant difference in nodulation between water regimes. Maximum total nitrogenase activity was 22.5 and 18.8 µmoles of ethylene/plant/hour, respectively at flowering and pod‐fill in the well‐watered plants. The dry regime by contrast achieved a maximum nitrogenase activity of 5.3 and 4.5 µmoles ethylene/plant/hour at pod‐fill and pod yellowing stages of maturity, respectively. Consequently, there was a significant reduction in total nitrogenase activity (mmoles of ethylene/plant/growing season) averaged over four Rhizobium strains from 14.5 in the well‐watered to 3.7 in the droughted regime. This decrease in N fixation capacity did not decrease seed yields of droughted plants below those of well‐watered plants.
Potassium Response of Alfalfa in Solution, Sand, and Soil Culture1
Authors: Romero N. A. , Sheaffer C. C. , Malzer G. L.
Published: July 2010

Information on yield response to K by alfalfa (Medicago sativa L.) cultivars should be useful for determining the possibility of improving K utilization. Our objectives were to compare plant culture systems as methods of assessing K fertilization effects on alfalfa yield and K uptake, and to determine the effect of cultivar winterhardiness on yield. Growth chamber and glasshouse studies were conducted in which alfalfa cultivars were grown in sand and solution culture with nutrient solutions containing 0, 35, 60, 85, and 110 mg K/liter and in three soils receiving 0, 100, 200, 400, and 800 mg K/kg.

Sand culture was not effective in evaluating potential cultivar yield differences in response to K fertilization because K levels were insufficient for plant growth. Solution culture provided a wide range of K availability which allowed for evaluation of differential yield response by cultivars. Alfalfa yields for soil culture were less than for solution culture and K additions did not produce as wide a range of herbage K concentrations as solution culture.

In solution and soil cultures, cultivars differed in yield and in herbage K concentration responses to increasing K concentrations, but these responses were not related to cultivar winterhardiness. Cultivars also differed in herbage K concentrations at maximum dry matter yields and at the onset of K deficiency symptoms. Our results show that no relationship existed between cultivar winterhardiness level and yield response to K fertility. However, it may be possible to select cultivars which perform under low soil K fertility levels.