bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Tolerances of Turfgrass Cultivars to an Acid Soil High in Exchangeable Aluminum1
Authors: Murray J. J , Foy C. D
Published: July 2010

Soil acidity is a major problem in establishing and maintaining turfgrass in many areas. Aluminum toxicity is probably the most important factor limiting growth of turfgrass in many, if not most, acid soils, particularly below pH 5.0. Liming turfgrass soils to pH 6.0, or higher, to detoxify Al, is not always economically feasible. A promising alternative or supplementary approach is to select or develop cultivars tolerant to Al. To explore the possibilities of this approach, 35 Kentucky bluegrass (Poa pratensis L.), 15 fineleaf fescue (Festuca rubra L.), and 6 tall fescue (Fescue arundinacea Schreb.) cultivars were grown in greenhouse pots containing 1.0 kg of Altoxic Tatum soil (clayey, mixed, thermic, typic, Hapludult) at two pH levels (pH 4.6 and 5.7 for bluegrasses and pH 4.3 and 5.7 for fescues). Relative top yields (pH 4.6/pH 5.7)% of Kentucky bluegrass cultivars ranged from 8.0% for ‘Windsor’ to 91.0% for ‘Fylking’; relative root yields ranged from 5.3% for ‘Kenblue’ to 101.8% for ‘Victa’. Relative top yields (pH 4.3/pH 5.7)% of fineleaf fescues ranged from 17.1% for common creeping to 91.1% for ‘Wintergreen’; however, 11 of the 15 cultivars studied made satisfactory growth at pH 4.3. Relative top yields (pH 4.3/pH 5.7)% of the tall fescues ranged from 1.8% for ‘Fawn’ to 35.4% for ‘Kentucky 31’. Within several tall fescue cultivars, individual plants (in the same pot of unlimed soil at pH 4.3) showed wide growth differences which were largely equalized by liming the soil to pH 5.7. Results of our studies suggest appreciable potential for selecting or developing turfgrass cultivars for greater tolerance to acid soil stress factors (particularly Al toxicity) that may not be economically correctable. Such cultivars would be deeper rooted and better adapted to low maintenance conditions.
Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand1
Authors: Al‐Khafaf S. , Wierenga P. J. , Williams B. C.
Published: July 2010

A simple, reliable method for predicting evapotranspiration (ET) for crops is needed. The purpose of this study was to formulate and test empirical relationships far estimating soil evaporation and transpiration based on evaporative demand and crop development with limiting and non‐limiting soil water regimes. The relationships were compared with evaporation and transpiration data for irrigated cotton (Gossypium hirsutum L.).

Evaporation from the soil surface was determined by measuring diurnal changes in the surface soil‐water content and weight changes in embedded containers. Evapotranspiration was calculated from the quantity of irrigation water applied, rainfall, drainage, and changes in soil‐water content measured by the neutron scattering technique. Evaporation from the soil surface on the 1st day after irrigation (ESo) was related to potential evaporation (Eo) and leaf area index (LAI) as: ESo = Eo exp(−0.623 LAI). On successive days after irrigation, surface evaporation (ES) was computed as: ES = 5,8t0.6 − 5.8(t − l)0.6, where t is time in days. For transpiration on the day after irrigation (EPo), the following relationship was found: EPo = Eo(l − exp(−0.623 LAI)). l'or limiting soil‐water conditions, transpiration (EP) Mas computed with: EP = EPo/ (1 + 6.2 exp − 15.2 FAW), where FA W is the fraction of available water in soil. The results obtained with these equations agreed well with values for ES and EP measured in this study and with data presented by Ritchie (1972).
Value of Drip Irrigation Compared with Conventional Irrigation for Vegetable Production in a Hot Arid Climate1
Authors: Singh S. D. , Singh Panjab
Published: July 2010

The application of water by drip irrigation is a relatively new technique. Much remains to be learned about its effects on crops under soil and climatic conditions of hot desert areas. Studies were undertaken to evaluate the relative merits of water application by drip irrigation, overhead sprinkling, and furrow irrigation with respect to the yield potential and water‐use efficiency (WUE) of long gourd (Lagenaria siceraria (Molina) Standl.), ridge gourd (Luffa acutangula Roxb.), watermelon (Citrullus lanatus Thunb. Mansf.), and round gourd (Citrullus vulgaris var. Fistulossus (Stocks) Duthie and Fuller). The effects of daily water application by sprinkling (SP‐1) on the latter two crops were also evaluated. With drip irrigation and SP‐1, water was applied daily in amounts equal to 68% of the evaporation from a Class A pan. With furrow and overhead irrigation, water application commenced when the cumulative total of evapotranspiration reached 3.2 em.

Drip irrigation increased the yield of long gourd by 45 to 47%, of round gourd by 21 to 38%, and of watermelon by 10 to 22% compared with sprinkler and furrow irrigation. All irrigation methods gave similar yields of ridge gourd. Thus, drip irrigation showed the potential to increase the yield of most, if not of all, vegetable crops. The water use efficiency with drip irrigation was nearly twice as high as with other methods of water application. Daily irrigation by sprinkling (SP‐1) on watermelon and round gourd decreased yields from 20 to 32% when compared with drip irrigation. Hence, on loamy sand soils in hot arid regions, daily irrigation is advantageous when the water is applied by drip irrigation but probably not when the water is applied by sprinkler irrigation.
Water Economy and Saline Water Use by Drip Irrigation1
Authors: Singh S. D. , Gupta J. P. , Singh Panjab
Published: July 2010

In arid regions water is scarce and efficient use of poor quality water by means of drip irrigation has become a necessity. Drip irrigation with good quality water at 1.0, 0.75, and 0.5 and with saline water at 1.0 times the daily evapotranspiration (ET) rate was compared with furrow irrigation using sweet water applied at the rate 1.0 ET with respect to the yield of potatoes (Solanum tuberosum L.) on a loamy sand soil. Drip irrigation with sweet and with saline water at the rate equal to 1.0 ET was also evaluated with respect to the yield of tomatoes (Lycopersicon esculentum Mill.). Water was applied daily by drip irrigation and at intervals of about 7 days by furrow irrigation in amounts equal to 63% of Class A pan evaporation.

Drip irrigation at a rate less than the ET rate decreased the yield of potatoes compared with the rate equal to ET. To obtain identical yields, drip irrigation required 50% less water than furrow irrigation. Saline water at 3,000 μmhos/cm applied by drip irrigation did not limit yields but at 10,000 μmhos/cm it reduced potato yields by 91% and tomato yields by 35%. The soil water content was about 15% beneath the emitter, 7% at a point 20 cm from the lateral, and 3 to 4% near the wetting front located 40 cm from the lateral. The wetted zone, extending 20 cm on either side of the lateral, could be used for twin‐row configurations. Salts were concentrated in the surface 15 to 20 cm of soil at the midpoint between the emitters and towards the wetting front. Salts were not leached to lower soil horizons with the treatments used in these experiments.
Alfalfa Root Development and Shoot Regrowth in Compact Soil of Wheel Traffic Patterns1
Authors: Grimes D. W. , Sheesley W. R. , Wiley P. L.
Published: July 2010

Reduced growth and fewer plants are common in wheel paths of post harvest equipment in alfalfa (Medicago sativa L.) fields of the San Joaquin Valley. Up to 70% of the soil surface may be covered by equipment wheels in a single harvest. Field and glasshouse studies were conducted to quantify plant and soil responses to wheel traffic in confined paths scheduled to simulate harvest operations. Three field compaction treatments simulated harvest, postharvest, and harvest plus postharvest wheel traffic. A no‐traffic area served as a control treatment. Compaction of a sandy loam soil (Typic Xerorthents) in traffic zones reduced root‐length density (cm of root per cm3 of soil) as much as 60% in a 15‐to‐30‐cm depth zone. Postharvest traffic reduced plant population and yield by damaging crowns and regrowth shoots. Field observations on soil‐compaction root‐growth relations were substantiated by a glasshouse study that char. acterized alfalfa root‐length density (Rd, cm of root per cm3 of soil) as a function of soil bulk density (Ds, g cm−3) and time (T, days) as Rd = −23.51 +27.88Ds +0.2210T −9.135D,s 2 −0.0003548T3 −0.08360DsT, R2 = 0.84. Root growth in a field study was enhanced by delaying the harvest for newly established seedings.
Seed and Fertilizer Patterns with Spinning and Oscillating Spreaders1
Authors: Wolf D. D. , Smith E. S.
Published: July 2010

Seeding and fertilization represent common operations where broadcast distributors increase efficiency of forage production and pasture renovation. The successful use of broadcast units has been something of an art with procedures based largely on trial and error experiences of the operator. In this paper we describe two broadcast delivery methods for application of fertilizers and forage seeds. Spinner and oscillating delivery methods were used to establish spread patterns and effective swath widths for phosphate (20% P) and potash (50% K) fertilizers, and seeds of red clover (Trifolium pratense L.), and tall fescue (Festuca arundinacea Schreb.) A mixture of P fertilizer, red clover, and tall fescue (100:12:6 ratio), typical of that appropriate for pasture renovation, was also tested. Both the spinner and oscillating units produced satisfactory spread patterns when properly adjusted. The spinner unit required adjustment for each material delivered to produce a symmetrical spread pattern while no changes were required with the oscillating type. The effective swath width was selected as the maximum width for a 15% coefficient of variation among rates at 0.6 m intervals across the field. The fertilizer‐seed mixture did not segregate seriously during delivery and the effective swath width was selected to achieve uniform coverage of the component with the smallest pattern.
Control by Tillage and Persistence of Volunteer Sunflower and Annual Weeds1
Authors: Robinson Robert G.
Published: July 2010

Volunteer sunflower (Helianthus annuus L.) is a major problem in crop rotations which include sunflower. This research was conducted to determine if the problem persists beyond the crop following sunflower and to learn if tillage methods affect populations of volunteer sunflower and annual weeds. Sunflower fields were harvested with a combine in 1973 and 1974 at Rosemount, Minn. Volunteer sunflower and annual weed numbers/ha were determined following five primary tillage treatments in combination with May and June planting of pinto bean (Phaseolus vulgaris L.) and a secondary preplanting rototiller treatment. Counts were made shortly after emergence in permanent 1‐m2 quadrats through 1977. Plots were rogued to prevent sunflower or weeds from producing seed. The weed seed population in the soil continued to supply weed plants every year, and there was no reduction in the last years of the trials. But volunteer sunflower populations in the 2nd year dropped to 2% of the first year's populations and were nearly 0 in the third and fourth years. Three treatment combinations that eliminated volunteer sunflower in 1 year were: no tillage in October followed by disk, plow, rototill in the spring; disk in October followed by plow, rototill in the spring; and rototill in October and again in the spring. Volunteer sunflower plants in the 1st year after sunflower were most numerous following rototilling in October and least numerous following no tillage in October. Weed plants were most numerous following moldboard plowing in October. About 90% of the volunteer sunflower emerged by 11 to 13 June.
Effects of Natrustoll Soil Horizons on Germination, Emergence, and Growth of Four Grasses1
Authors: McGinnies William J. , Ludwig Jim R.
Published: July 2010

Rehabilitation of low‐value saltgrass [Distichlis stricta (Torr.) Rydb.] meadows involves elimination of the existing vegetation and establishment of palatable forage grassy. The seeded forage grasses have frequently failed to become established in field plantings on Natrustoll (Solonetz) soils, particularly where the B and C horizons have been brought to the surface by plowing. To determine how soil material from the Natrustoll soil horizons affects grass establishment, soil from A, B, and C horizons was placed in pots in a greenhouse, and emergence, establishment, and growth of four promising range grasses were measured. We found that Agropyron elongatum, A. desertorum, Elymus junceus and Bromus inermis could readily be established on soil from the A and B horizons of the Natrustoll soil found in the saltgrass meadows. On the C horizon, all species would germinate and emerge (although germination and emergence were slower), but only A. elongatum could become established. Herbage yields on the C horizon were less than 5% of yields on A or B horizons. We attributed the poor establishment and yield on the C horizon to its saline‐alkali nature (a pH of 8.8, a conductivity of 12.6 mmho/cm, and a sodium adsorption ratio of 78.6).
Large Crabgrass Control in Turfgrasses with Fall‐applied Herbicides1
Authors: Johnson B. J.
Published: July 2010

Herbicidal control of both winter and summer annual weeds in turfgrasses usually requires fall and spring treatments which utilize excessive amounts of chemicals. Management studies were conducted for 3 years on common bermudagrass [Cynodon dactylon (L.) Pers.] at Griffin and Kentucky bluegrass (Poa pratensis L.) at Blairsville, Georgia, to determine the effectiveness of fall and fall + reduced spring rates of herbicides applied for large crabgrass [Digitaria sanguinalis (L) Scop.] control to minimize chemicals applied. The experiments were conducted on Cecil (Typic Hapludult) sandy loam at Griffin and Hatboro (Typic Fluvaquents) sandy loam at Blairsville.

Bensulide [0,0‐diisopropyl phosphorodithioate S‐ester with N‐(2‐mercaptoethyly)benzenesulfonamide] was the only herbicide that consistently controlled at least 82%, of large crabgrass the summer after fall treatment. All other herbicides required fall and repeated spring treatments for consistent control.
A Hand‐Held Grafting Device for Making Uniform Wedge Cuts1
Authors: White M. C.
Published: July 2010

The design of a hand‐held device for making uniform wedge cuts for reciprocal grafts is described. The Plexiglas device uses two changeable stainless‐steel, single‐edge razor blades to simultaneously cut a uniform wedge and its receptacle in a plant stem. This reduces considerably both plant handling and the time required to perform numerous reciprocal grafts. In plants of similar age and stem diameter, the uniform cuts should allow more efficient tissue matching and increased survival of the grafted plants.
Fertilization of Switchgrass in the Greenhouse with Various Levels of N and K1
Authors: Smith Dale
Published: July 2010

Switchgrass (Panicum virgatum L.) is a warm‐season, native grass that may have value in humid areas for summer pasture. The objective of this research was to obtain additional information on its response to N and K fertilization. Soil cores of ‘Forestburg’ switchgrass were removed from the field before spring growth started and transplanted into plastic pots in a warm greenhouse (27 to 35 C). The soil was a Dodge silt loam (Typic Argiudoll) with low levels of N and K. Potted plants were fertilized with 0,50,100,200, and 400 kg/ha of N as NH4NO3 in all combinations with 0 and 200 kg/ha of K as KCl. Plants were harvested 52 days later at near anthesis. Fertilization with N significantly increased the dry matter yields (g/pot) of herbage and of stem base tissue (stubble), percentage and content (mg/pot) of N in the herbage, and content of total nonstructural carbohydrates (TNC) in the stubble. Fertilization with N decreased significantly the percentage of K in the herbage, but did not influence the content of K in the herbage and the percentage of TNC in the stubble. Fertilization with K significantly increased stubble dry matter yields, but did not influence the yields of herbage. Fertilization with K significantly increased the percentage and content of K in the herbage and content of TNC in the stubble, but did not influence the percentage and content of N in the herbage or percentage of TNC in the stubble. It was concluded that the vegetative growth of switchgrass is very responsive to N fertilization to the highest rate applied (400 kg/ha), but was not affected greatly by fertilization with K.
Laboratory and Field Response of Preconditioned Upland Cottonseed to Minimal Germination Temperatures1
Authors: Fowler J. L.
Published: July 2010

Hydration of cottonseed (Gossypium hirsutum L.) prior to germination is known to desensitize the seed to chilling injury. Little has been reported, however, on the effects of these hydration treatments on germination and subsequent growth of cotton subjected to minimal germination temperatures, especially in the field. This study evaluated the effect of pregermination hydration treatments on stand establishment, seedling vigor, yield, and earliness of the crop. Hydration of ‘Acala 1517‐70’ cottonseed in water or saturated CaSO4 solution for 6 hours at 31 C, or in hot water for 1.5 min at 85 C and dried overnight in ambient air, stimulated germination and seedling elongation at 14 C in the laboratory. Preconditioned seed responded similarly at 14 C after chilling at 5 C for 24 hours. The effects of these treatments on emergence, seedling vigor, crop earliness, yield, and fiber properties were field evaluated ova a 2‐year period using several planting dates to provide a range of weather conditions. No advantages of using hydrated seed were demonstrated in the field tests as hydration of cottonseed decreased seedling vigor and, under favorable germination conditions, reduced stands.
Crude Protein Levels in Turfgrass Clippings1
Authors: Turgeon A. J. , Stone G. G. , Peck T. R.
Published: July 2010

Leaf clippings are a by‐product of turfgrass culture and they are frequently collected and discarded where a high level of turfgrass quality is desired. The purpose of this investigation was to determine the value of turfgrass clippings as a source of protein for animal feed.

Clippings were collected during mowing in seven different field experiments and crude protein (CP) levels were calculated from a measurement of total N (CP = N ✕ 6.25) by the Kjeldahl procedure. In some studies, nitrate N and ammonium N levels were measured in clippings. All turfgrasses were growing in an Aquic Argiudoll (Flanagan silt loam) soil. The CP content of the clippings varied with species, cultivars, mowing height and nitrogen (N) fertilization rate. Among 53 Kentucky bluegrass (Poa pratensis L.) cultivars maintained under the same cultural regime, CP levels varied from 22.0 to 32.7%. Comparing eight perennial ryegrass (Lolium perenne L.) cultivars, CP varied from 26.3 to 30.2%. The CP levels of clippings from ‘Kenblue’‐type Kentucky bluegrass and ‘Kentucky‐31’ tall fescue (Festuca arundinacea Schrebs.) turfs, that were each maintained under different cultural intensities, were inversely proportional to the mowing height and directly proportional to the N fertilization rate. (The highest CP level measured was 38.7% in early October.) The level of NO3‐N in the Kentucky bluegrass clippings varied with mowing height and frequency, fertilizationn rate, and season. The highest level measured was 0.16% which is below that considered toxic to ruminants. These experiments have shown that turfgrass clippings can be an important source of protein for use in some animal feeds, and that high concentrations of crude protein can occur depending upon season, turfgrass cultivars, and mowing and fertilization practices.
Research Plot Planter with Wide Versatility1
Authors: Knapp W. R. , Trenchard G. D.
Published: July 2010

Field research with small grains or row crops often involves a number of different treatments at planting. Since no presently available, or previously described, individual planter provides all the flexibility needed for a wide range of experiments, a planting unit was constructed that permits simple changes in species, cultivars, seeding rates, row spacing, and fertilizer rates and materials. The three‐point hitch mounted unit consists of a steel framework with seven double disk coulters, two fertilizer boxes, a cone‐spinner and distributor, and an operator's seat. The planter can be adjusted to plant plots ranging from 1 to 75‐m long at any seeding rate and with row spacings of 16, 36, 54, and 72 cm. Fertilizer rates of 20 to 800 kg/ha can be applied through each box. A number of crop species, including forages, have been successfully planted with the machine over the past 2 years. The unit is easily transported and can plant as many as 100 8‐m long plots/hour.
Heat Stress as a Special Purpose Alternative to Clipping in Alfalfa1
Authors: Venuto B. C. , Laude H. M.
Published: July 2010

Regrowth in alfalfa (Medicago sativa L.) usually is studied following cutting. The possibility that regrowth after a different type of defoliation might reveal useful information led to the present greenhouse and chamber study. By exposing plants for 5 or 6 hours to heat reaching 52 C, aerial tissues were killed but crown buds survived to regrow. The heat‐stressed plants were delayed from 7 to 14 days in attaining the shoot numbers of clipped plants, but this regrowth appeared morphologically normal and initially was not influenced by the living residual leaf or buds found on stems below a cutting height. Certain attributes of regrowth, following high temperature exposure may prove useful in future research. When plants 50 to 92 days of age received the same stress, the older plants produced shoots in regrowth more rapidly than did the younger. Within an age group, those plants in flower when stressed produced more shoots than did those not yet showing flower buds when stressed. Individual plants with larger shoot numbers before either clipping or heat stress produced more shoots during regrowth.
Influence of Nutrition on Stripe Smut Severity in Kentucky Bluegrass Turf1
Authors: Hull R. J. , Jackson N. , Skogley C. R.
Published: July 2010

Stripe smut, caused by the fungus Ustilago striiformis (West.) Niessl., is highly destructive to several fine turf cultivars of Kentucky bluegrass (Poa pratensis L.). while there is evidence that turf management practices can modify disease injury, the role of nutrient status in disease development is uncertain. Stripe smut severity and fertility management was studied using ‘Merion’ Kentucky bluegrass plots fertilized with four nutrient combinations (N:O:O, N:P:O, N:O:K, and N:P:K) applied at three rates (12:2:4, 24:4:8, and 48:8:16 g N, P, and K per m2 per year). A natural infection of stripe smut occurred throughout the plot area in 1972 and persisted through 1975. After infection, a close correlation between turf quality and disease incidence was noted. Heavily infected plots, as indicated by disease scores and counts of infected tillers, were those fertilized at high rates with incomplete fertilizers. Grass receiving high rates of N‐P‐K fertilizer was less diseased than that receiving high N alone or N plus P or K. Tiller counts revealed stand thinning in all plots as the disease continued but low fertility plots contained more plants than heavily fertilized plots. Stripe smut severity in susceptible Kentucky bluegrass cultivars is influenced by fertility level and balance.
Long‐Term Potassium Requirements of Nitrogen‐fertilized Smooth Bromegrass1
Authors: George J. R. , Pinheiro M. E. , Bailey T. B.
Published: July 2010

Nitrogen fertilization of smooth bromegrass (Bromus inermis Leyss.) has been extensively studied, but relatively little is known about its K requirements. A field study was conducted on a Clarion loam (Typic Hapludoll) site in central Iowa to evaluate the long‐term K requirements of smooth bromegrass grown under high N fertility and intensive harvest management. Forage yield and percent K was observed over 4‐ and 3‐year periods, respectively. Changes in soil exchangeable K and pH at 0 to 7.5‐ 7.5‐ to 15‐, and 15‐ to 30‐cm soil depths were monitored during 1970–75 and 1970–73, respectively. Ammonium nitrate (33.5‐0‐0) was applied at rates of 0, 125, and 500 kg N/ha in 1970, and 0, 250, and 500 kg N/ha during 1971–74 (N0, N1, and N2 treatments, respectively). Applications were made as single levels in 1970. Rates were split in subsequent years, with half applied in early spring and the rest after the second harvest. Potassium treatments consisted of a check and 125 kg K/ha applied each year in early spring as Cl‐ and S‐ containing sources (KC1 vs. K2SO4 and K2SO4 • MgSO4).

Nitrogen fertilization produced more of a linear than quadratic increase in bromegrass yield. Yields were not increased by K fertilization even when soil exchangeable K approached “minimal” levels. No yield differences among K sources were observed, suggesting that yields were not enhanced by either Mg or S contained in the K sources.

Nitrogen fertilization reduced forage percent K concentrations. Potassium fertilization without N had no effect, whereas, NK fertilization increased forage percent K. Differences in forage percent K among K sources occurred only in 1972 with higher concentrations observed for KC1 compared with K2SO4 and K2SO4 • MgSO4.

Fertilization with N reduced soil exchangeable K. Decreases were most evident for the 0‐ to 7.5‐cm soil layer, but were significant to a depth of 15 cm. Potassium fertilization without N increased K in the 0‐ to 7.5‐cm soil layer. Soil K decreased 47% when no K was applied, suggesting that a severely N deficient bromegrass sward, if harvested, requires some applied K to maintain soil K concentrations. When both N and K were applied, soil K decreased to 137 kg/ha in the 0‐ to 7.5‐cm soil layer. These trends observed over time suggest that bromegrass obtains most of its K from surface soil layers.

Fertilization at N1 and N2 levels reduced pH in the 0‐ to 7.5‐cm soil layer from 6.3 to 6.0 and 6.2 to 5.3, respectively. Most of the pH change developed during the 1st year as evidenced by linear regression coefficients of —0.0017, —0.0020, and —0.0025 pH units/kg N/ha applied in 1971, 1972, and 1973, respectively. Fertilization with K produced little change in surface soil pH. No effect of N and K fertilization on soil pH was observed below the 7.5‐cm depth.
Effect of Prices and Moisture Stress on Nitrogen Rates that Maximize Two Economic Criteria for Corn1
Authors: Escamilla Emilio , Voss Regis , Webb J. R.
Published: July 2010

Fertilizer rates, which maximize certain economic criteria for crop production, are affected by the yield response to fertilizer, the ferti1izer:crop‐price ratio, the crop price, and the cost of production. The purpose of this study was to evaluate the effects of different fertilizer N:crop‐price ratios (P,), corn (Zea mays L.) prices (Py), and moisture‐stress levels (S) on the rates of fertilizer N that maximize net return (m) and rate of return (M) to total investment in corn production per unit of land area.

Fifteen site‐years of data were used from two continuous‐corn fertilizer rate experiments conducted under different crop management and environmental conditions. Moisture stress had a different effect in each experiment on yield and yield response to N.

Net return from corn production and the rate of return to investment per hectare at the economic optimum N rate were affected by all factors considered. They were affected more by decreasing Py by half from 13.77 to 6.88¢/kg than by increasing the Pr ratio fourfold from 2.8 to 11.2 on a kg N:kg corn‐price basis. Only a severe deleterious effect of moisture stress on yields and yield reponse to N decreased the net return and rate of return more than decreasing the price of corn.

At a constant PrM, decreasing the corn price caused the N rate that maximized M to increase and approach the economic optimum N rate. At a constant N price and a decreasing corn price, the economic optimum N rate decreased, but the N rate that maximized M remained static. In either case, these two N rates approached each other. A deleterious moisture‐stress effect also caused both N rate to decrease but approach each other.

These results suggest that, if there are increasing production costs and(or) decreasing crop prices, an overreduction of a divisible responsive input such as fertilizer N on corn could markedly affect the return to total investment on per‐land‐area basis.
Inhibition by Some Allelochemicals of Intake of Individual Meals by Meadow Voles1
Authors: Kendall W. A. , Hill R. R. , Shenk J. S.
Published: July 2010

A large number of allelochemicals may occur in forage plants but only a few of them can be studied in detail with large animals. Therefore, studies with small animals are essential to provide information that may be common to many animals or contribute towards the justification of further research with large animals. The objective of these experiments was to determine the relative importance of allelochemicals that are common in forages as they affect feed intake by the meadow vole (Microtus pennsylvanicus). The allelochemicals were fed alone or together in single meals to meadow voles. Gramine, hordenine sulfate, and tryptamine‐HCl, which occur in reed canarygrass (Phalaris arundinacea L.) were diluted to various concentrations with potato starch. Crownvetch (Coronilla varia L.) plants were grown with adequate or limiting levels of N and irradiation to the lowermost leaves to provide plants with different levels of β nitropropionic acid (NPA). Semisynthetic diets with various levels of NPA or combinations of NPA with one of the alkaloids were prepared by mixing the test chemicals with potato starch.

Intakes of semisynthetic diets by the voles were inhibited by each of the allelochemicals. Inhibition by gramine and tryptamine were similar and greater than the inhibition with hordenine when measured on a weight basis. Inhibition by the three alkaloids was similar on a molecular basis. The intake of fresh leaves of crownvetch was probably limited by NPA and some additional inhibitor(s). The inhibitory effect of the alkaloids on intake was additive when they were fed in mixtures in synthetic diets. A synergistic effect on intake was obtained with diets that contained mixtures of gramine and NPA. We conclude that the biological activity of hordenine is of sufficient magnitude to warrant further work to determine its prevalence‐in the field and effects on animals.
Volunteer Legume Control in Legume Seed Crops with Carbon Bands and Herbicides. I. White Clover1
Authors: Rolston M. Philip , Lee W. Orvid , Appleby Arnold P.
Published: July 2010

In legume seed production, volunteer legumes from seed in the soil may result in contamination of seed lots. No herbicides are available which can selectively control volunteer legumes in seeded legumes when both are exposed to the herbicide. Greenhouse and field experiments on white clover (Trifolium repens L.) were conducted in western Oregon to determine the potential of using activated carbon applied in bands over the seed row, with nonselective herbicides, to selectively control volunteer legumes. A 25‐mm band of activated carbon was applied to the soil surface over the seeded row during planting and a nonselective herbicide was applied broadcast immediately. Weed control was visually evaluated, and stand and seed yield of the white clover was measured. The carbon: herbicide ratios required for protection with 0.5 kg/ha of diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea], atrazine [2‐chloro 4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine], and simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine] were 50:1, 200:1, and 200:1, respectively. This reduction resulted in seed yields of 80, 40, and 14% of the check at first harvest of fall‐planted white clover. Atrazine and simazine at 1.25 and 1.5 kg/ha, respectively, reduced seedling numbers to the same extent as diuron at 2 kg/ha. In the second harvest of these treatments, seed yields from plots established with diuron at 2 and 3 kg/ha were similar to those from the check plots. Seed yields from white clover established with carbon bands in the spring were not reduced by diuron. White clover injury was greatest when diuron was applied to soil that was wet on the surface. Seed germination and seed weight were not influenced by the herbicides used in these experiments. Weed control between the carbon bands was good but grasses and broadleaf weeds also were protected by the carbon band. With carbon banding, volunteer white clover and volunteer narrow birdsfoot trefoil (Lotus tenuis Waldst. & Kit) were both reduced 95% by diuron applied at 2 and 3.3 kg/ha. Individual circumstance will determine whether the increase in seed lot quality that results from the control of volunteer legumes will offset the reduction in the quantity of seed produced.
Compensatory Growth in the Crown Root System of Sorghum1
Authors: Jordan W. R. , McCrary Marion , Miller F. R.
Published: July 2010

The number of crown roots which develop on grain sorghum (Sorghum bicolor (L.) Moench) plants under field conditions is often reduced far below the genetic potential. As a first step toward understanding the significance of the number of crown roots to total function of the root system, we conducted experiments to determine the capacity for growth when root numbers were restricted by clipping treatments and water and nutrients were not limiting. When grown in hydroponics, ‘RS610’ sorghum plants developed an average of 20.6 crown roots by 50 days after planting (DAP). Root clipping treatments, initiated when plants were young, gave groups of plants in which 3, 6, and 10 crown roots were allowed to develop. For plants with at least six roots, leaf areas, shoot, and root dry weights were not different from controls. Plants maintained with only three roots had reduced leaf areas and lower shoot and root dry weights by 50 DAP; however, branching and growth of second and third order lateral roots were promoted. When compared at equal leaf areas, total root lengths and root volumes were equivalent for all treatments. Thus, compensatory growth within the existing root members was capable of maintaining root length and volume, but not root dry weight when crown root numbers were severely reduced.
Managed Soil Moisture System for Studying Plant Water Relations under Field Conditions1
Authors: Reetz H. F. , Hodges H. F. , Dale R. F.
Published: July 2010

A Managed Soil Moisture System (MSMS) was installed at the Purdue Univ. Agronomy Farm for plant water relations research. Sixteen plots, each 6.1 m ✕ 9.8 m, can be controlled individually for water application and removal. The MSMS was designed on the principle of the Prescription Athletic Turf (PAT) system developed at Purdue. The area was excavated and lined with a moisture barrier. After the drainage/irrigation system was installed, the plots were filled to a depth of 40 cm with dune sand. During normal. “non‐moisture stress” operation a water table is maintained at a depth of 35 cm. Each plot has its own supply tank for monitoring the water use. An overflow allows drainage of excess rainfall, and a pump can be used to hasten drainage. Given a period of dry weather, this facility allows rapid adjustment of soil moisture for studying the effect of drought stress on plant growth. The plot size permits plant measurements and periodic destructive sampling without significantly affecting the crop canopy environment. In preliminary experiments in 1974, corn (Zea mays L.) grew normally to maturity with a water table at 35 cm. During a hot, dry period, severe leaf curling began on the stress plots 4 days after the drainage system was opened. Coupled with meteorological and soil water data, plant growth, and water potential measurements, this facility provides a relatively low cost means for studying environmental‐plant response data under near‐natural environments.
Tolerance of Cotton to the Herbicide Glyphosate1
Authors: Jordan T. N. , Bridge R. R.
Published: July 2010

An increasing group of weed pests in U.S. cotton (Gossypium hirsutum L.) are the perennial grasses which can be controlled with glyphosate [N‐phosphonomethyl) glycine], but cotton is also sensitive to this herbicide. Field studies were initiated to determine if certain cotton genotypes could be selected with sufficient tolerance to glyphosate to allow its use in a cotton‐weed control program. In 1974,405 genotypes were evaluated for tolerance to glyphosate at rates of 0.84, 1.68, and 3.36 kg/ha applied as an over‐the‐top treatment in the early bloom stage. In 1975, 24 genotypes selected from 1974 studies were screened at rates of 0.56 and 0.84 kg/ha of glyphosate ap lied over‐the‐top of cotton plants. Six genotypes selected from previous studies were evaluated with glyphosate applied over‐the‐top or directed under cotton plants 50 to 62 cm in height in the very early square stage. Glyphosate toxicity varied with cotton genotypes and increased with increasing rates. In 1976 and 1977, all genotypes that received an over‐the‐top treatment of glyphosate yielded significantly less seed cotton than the untreated checks. Glyphosate applied as a directed post‐emergence treatment did not cause significant injury symptoms in treated cotton, however, none of the treated genotypes produced seed cotton yields equal to their untreated controls. Cotton injury was only 10% or less when the herbicide was directed to the base of the plants as compared with 65 to 80%, injury when the herbicide was applied over‐the‐top. Two genotypes (DES 04‐11 and DES 04‐606) yielded over 100% of their untreated controls when one or two separate applications of 0.56 kg/ha of glyphosate was directed to the base of the cotton plants in 1977. The increase in yield of these two genotypes was not significant, but indicated a level of glyphosate tolerance which could be used in the development of commercial cultivars possessing enough tolerance to glyphosate to allow its use for perennial weed control in cotton.
Relationship of Stelar Lesions to Radicle Growth in Corn Seedlings1
Authors: Cohn Marc Alan , Obendorf R. L. , Rytko G. T.
Published: July 2010

Chilling during imbibition of Zea mays L. kernels resulted in anatomical lesions across the stele of radicles, and subsequently in reduced growth of radicles. The objective was to determine if stelar lesion formation accounted for the radicle growth reduction. Inheritance patterns, source of seedstodrs, maturity of kernels, and surgical treatments of pericarp and endosperm were used to compare lesion occurrence and radicle growth in laboratory evaluations of field‐grown seedstocks. Chilling injury of 5% (low) moisture kernels was measured as radicle growth reduction after a 48 hour hydration treatment at 5 C followed by 4 days at 25 C when compared to Similarly treated controls with 13% moisture kernels. Chilling injury was also measured as stelar lesion formation. In cresses between the sensitive inbred ‘Oh51A’ and the injury resistant inbred ‘B8,’ both radicle growth reduction and stelar lesion formation were receive characters. While the inheritance of either character was not altered substantially by the maternal parent in studies of intact kernels, pericarp damage in chilling sensitive crosses resulted in more severe radicle growth reduction without increasing lesion frequencies. Removal of the endosperm prior to imbibitional chilling resulted in lower lesion frequencies in sensitive inbreds and hybrids. Various sources of the Oh51A inbred had markedly different sensitivities to imbibitional chilling. Maximum sensitivity occurred before kernel maturation. Increasing kernel moisture to 13% before hydration at 5 C reduced or avoided injuries caused by imbibitional chilling of 5% moisture kernels. The embryo, pericarp, and endosperm each influenced the severity of imbibitional chilling injury. While the stelar lesion may contribute to radicle growth reduction, it was not the only factor responsible for imbibitional chilling injury of corn.
Effects of Crop Sequence and N Fertilizer Levels on Soil Bulk Density
Authors: Hageman N. R. , Shrader W. D.
Published: July 2010

The effect of intensive corn (Zea mays L.) production on soil properties and on the productive capacity of soils is a matter of continuing concern. A 20‐year comparison of continuous corn (CCCC) and a corn‐oats (Avena sativa L.)‐meadow‐meadow (COMM) rotation with various N rates on Webster silty clay loam, a Typic Haplaquoll, in north‐central Iowa, provided the opportunity to measure soil changes induced by these two widely differing cropping systems.

It was found that, at the 15 cm depth, the soil bulk density in the CCCC and COMM rotations was 1.17 and 1.13 g/cm8, respectively. The difference was attributed to less machinery travel and greater organic matter production on the COMM rotation. When the N fertilizer treatments were compared at the 15 cm depth, the soil bulk density of the 134 kg N/ha treatment was 1.10 g/cm8, and the 0 kg N/ha treatment was 1.20 g/cm8. The difference here was attributed to greater production of organic matter in the higher N treatment.

The organic matter content was 5.02 and 5.52% in the CCCC and COMM rotations, respectively. In the 0 kg N/ha treatment and the 134 kg N/ha treatment, the organic matter content was 5.21 and 5.33%, respectively. As the soil organic matter increased, the soil bulk density decreased.
Rate of Fill and Length of the Grain Fill Period for Nine Cultivars of Spring Oats1
Authors: McKee G. W. , Lee H. J. , Knievel D. P. , Hoffman L. D.
Published: July 2010

We hypothesized that yield differences among cultivars of spring oats, Avena saliva L., can be partially explained by differences in the daily rate of grain fill and length of the grain fill period. To obtain information on these factors, nine cultivars of spring oats were sampled three times weekly in the field in 1975. The time between anthesis and physiological maturity was considered to be the fill period. Physiological maturity was considered to be the date beyond which there were no differences in grain yield significant at the 5% level of probability and half of the glumes and kernels no longer took up a red water soluble dye. In 1975, the mean grain fill period for nine spring oat cultivars, planted and fertilized at recommended rates, was 23 days with a range of 20 to 24 days. In 1976, for eight of the same nine cultivars, the mean grain fill period was 24 days with a range of 23 to 26 days. One variety, ‘Pennfield,’ was tested over a 3 year period. Lengths of the grain fill period were 22, 26, and 25 days, respectively, in 1975, 1976, and 1977. In 1975, the mean daily rate of grain fill at 0% moisture was 95 kg/ha with a range of 88 to 100 kg/ha. Data on rate of grain fill were not secured hi 1976. Grain yield in 1975 was significantly correlated at the 1% level with rate of grain fill, length of the grain filling period, leaf area duration, and accumulated heat units and solar and sky radiation during the grain fill period. Multiple correlation and regression analysis indicated that low rates of grain fill and short leaf area duration limited grain yield in 1975. These data suggest that it may be easier to increase spring oat yields by altering the rate of grain fill than to greatly increase the length of the fill period.
Nitrogen Rate‐Yield‐Precipitation Relationships and N Rate Forecasting for Corn Crops1
Authors: Isfan Daniel
Published: July 2010

The purpose of this study was to determine relationships between precipitation, N rate, and yield, and to develop a criterion that would permit to forecast in the spring the most probable optimum N rate. The study was carried out on a chernozem soil, in a continental temperate climate, characterized by an average annual precipitation of about 500 mm that vanes greatly between years and between seasons. Regression analysis of 14 years of data has shown that optimum N rate was more highly correlated with November to February inclusive; accumulated precipitation (r=0.77**) than with May to August precipitation (r=0.41). The multiple correlation coefficient of optimum N rate and the two precipitation periods was highly significant (r=0.94**). In years with roughly normal summer precipitation, November to February precipitation was more important (I=0.86**). In years with less than 100‐120 mm in November to February, the applied N was less efficient even when the summer precipitation was greater than normal. The May to August precipitation had a higher direct effect on the N rate only in wet winter years, (with precipitation of over 200 to 220 mm in November to February); here, the simple correlation of the N rate with the winter precipitation decreased (r=0.50) and that with May to August precipitation increased (r=0.84**; 0.01 level), but the interaction effect of winter and summer precipitation was still significant (R=0.89**). This suggests that in all cases, winter precipitation can be used to predict the optinum rate of N fertilizer. To calculate the optimum N rate in March,the following equation is proposed:

N rate = 19.53 + 0.2854X1 + 0.0066X1X2 (R=0.90)

If the November to December precipitation exceeds 220 mm and the spring continues to be wetter than normal, the N rate can be calculated again in June, using the following equation:

N rate = 28.37 + 0.0021X1X4 + 0.0032X3X4 ‐ 0.2538X4 (R=0.97)

where: X1, X2, and X4 are the November to January, February and May‐ July precipitation (mm), respectively. Estimating the N rates in March and reestimating in June with the above two regressions gives an average yield increase of 69% and a profit 200% greater than with annual application of the long‐term average N rate. The yield increase was also more highly correlated with November to Februay (r=0.63; 0.05 level) than with May to August precipitation (r=0.59*; 0.05 level), and the interaction effect of these two variables was high (r=0.92**; 0.01 level). Yields can be predicted in summer using both winter and summer precipitation.
Fescue Yield Response to Sewage Sludge Compost Amendments1
Authors: Sikora L. J. , Tester C. F. , Taylor J. M. , Parr J. F.
Published: July 2010

The agronomic benefits of applying sewage sludge compost to land have yet to be defined. The study reported is part of a series designed to assess the benefits. It deals specifically with fescue yield response to sewage sludge compost and fertilizer. An Evesboro loamy sand (Typic Quartzipsamments) and a Fauquier silt loam (Ultic Hapudalfs) soil were amended with four rates of sewage sludge compost (0 to 6% equal to 0 to 134.4 metric ton/ha, dry weight), plus an additional lime control and two rates of N, P or N plus P (0 and 195 kg/ha) in a factorial greenhouse study. —Kentucky 31― tall fescue (Festuca arundinacea Schreb.) was grown and harvested at 40, 76, 120, and 167 days and the clippings were dried and weighed. A significantly greater grass yield was obtained from the compost amended Evesboro than the compost amended Fauquier which contained a vermiculite clay fraction. Yields were linearly related to compost amendment for both soils. Yields were significantly increased by the addition of N, P, or N plus P to compost amended soils. The largest yield increase was obtained by the addition of N plus P. The mineralization of compost organic N was the limiting factor in grass yield. Regression models were derived from the data using compost and days as independent variables for each soil, N, and P combination. In most cases, a quadratic term for compost amendment was necessary for explaining the variation in yield. Regression model equations based on cumulative yield data contained similar terms for each soil, N, and P combination except for the Fauquier soil with N and P added for which no model was obtained.