bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidation Status and Gas Composition of Wet Turfgrass Thatch and Soil1
Authors: Thompson D. C. , Smiley R. W. , Fowler M. Craven
Published: July 2010

Excess thatch in turfgrasses is often associated with decreased plant vigor and increased disease susceptibility. Thatch is the primary rooting medium for many grasses, and is a substrate that possesses many prerequisites for anaerobiosis. The oxidation status and the gas composition in unsaturated thatch of mature Kentucky bluegrass (Poa pratensis L.) were measured to determine if anaerobiosis occurs under field and greenhouse conditions. Soils under the sods included a Hudson silty clay loam (fine, illitic, mesic Glossaquic Hapludolf), a Riverhead sandy loam (coarse−loamy, mixed, mesic Typic Dystrochrept), and an Arkport fine sandy loam (coarse−loamy, mixed, mesic Psammentic Hapludalf). Measurements of redox potentials (Eh) and concentrations of oxygen (O2), carbon dioxide (CO2) and ethylene (C2H4) were made. Conditions of poor oxidation, including low Eh and O2 and CO2 concentrations, and accumulations of C2H4, were measured in thatch on poorly drained soils in the field and in the greenhouse. Applications of lime and calcium arsenate amplified the extent of poor oxidation in thatch, whereas calcium nitrate improved the oxidation status. Thatch depth and a coring procedure did not influence thatch oxidation. The Eh varied diurnally and was lowest in wet thatches during warm, sunny days when thatch became warmer (by up to 7°C) than the air. Poorly oxidized conditions for periods over 7 h were measured in moist but unsaturated thatch in the field. The temperature of thatch appeared to be important in governing the oxidation status. Measurements of Eh were considered to provide rapid and useful insights into the gaseous composition of wet thatches. Our results imply that phytotoxic products of poorly oxidized environments may accumulate in wet thatch on warm sunny days. Such conditions may also be common in field−grown cores of mature turfgrass which are moved to the greenhouse for study. The relevance of these results to the occurrence of diseases such as Fusarium blight are discussed.
Corn Response to Sulfur Application in Coastal Plain Soils1
Authors: Reneau R. B.
Published: July 2010

Sulfur (S) fertilization is expected to increase corn (Zea mays L.) yields in coarse‐textured, well‐drained, and low organic matter Coastal Plain soils. This increase is expected because of the reduced quantities of S applied to agricultural lands in the form of by‐products from fertilizers applied to satisfy other nutrient requirements, increased removal of S from soil with increased crop yields, and increased emphasis on reducing atmospheric pollutants (thus decreasing S additions from atmospheric sources). This study was conducted to determine if corn yields could be increased by S additions to Coastal Plain soils and to determine if extractable soil S or tissue analyses could be employed to predict this response. Ten S fertilization experiments were conducted over a wide range of soils during 1978,1979, and 1980. Results showed that increased corn yields can be expected with S application on soils that are moderately well to well‐drained, low in organic matter, and belong to the fine loamy or coarser textured family of soils, and have acid monocalcium phosphate extractable soil SO4‐S concentrations ≤ 2.3 mg kg−1 in the surface horizon. When extractable soil S present in the Ap horizon was related to actual yield increases (∆y max) with a refitted Mitscherlich equation, a significant relationship was evident and 62% of the observed variability in relative yield could be explained. Fertilizer applications ranging from 18 to 28 kg S ha−1 were required to achieve 90% of maximum yield. The requirements appeared to be dependent on the method of application (broadcast preplant or split between broadcast and sidedress). When the relationship between total S and N:S ratio in the leaf below and opposite the ear leaf at silking and ∆y max was examined, 67 and 82% of the observed variation in ∆y max could be explained by a refitted Mitscherlich and a linear equation, respectively. From these equations it was estimated that the critical concentration for total S and N:S ratio would be 1.7 g kg−1 and 16, respectively. These data indicate that extractable soil S or tissue analyses could be used to identify fields that might be S deficient.
Turf Quality of Kentucky Bluegrass Cultivars and Energy Relations1
Authors: Mehall B. J. , Hull R. J. , Skogley C. R.
Published: July 2010

Future turfgrass improvement will depend upon recognizing those physiological properties responsible for stress tolerance and recovery from injury. Once recognized, these properties may be incorporated into the screening program of cultivar improvement efforts. Because energy capture and transport are basic to plant growth, we measured the variation in these processes between several Kentucky bluegrass (Poa pratensisL.) cultivars of varied origin and growth habit. In turn, CO2‐exchange rate (CER), clipping growth rate, and nutrient factors were evaluated for their correlation with turf quality. Field plots were on an Enfield silt loam (coarse‐silty over sandy skeletal, mixed, mesic, Typic Distrochrept). Carbon dioxide exchange rate was measured on plots of 15 cultivars during mid‐summer, 1978, and nine cultivars during late summer, 1980. On both dates, CER differed between cultivars and in 1978 were positively correlated with turf quality. Correlations between CER and clipping growth were significant but apparent photosynthesis was not related to leaf P and K content or nutrient efficiency ratios (mg dry wt. mg−1K or P). No significant differences in photosynthate partitioning to roots were noted between 10 cultivars in August or October 1978. This was based upon 14C recovered from roots 2 days following exposure of turf to 14CO2for 15 min. Nevertheless, the percentage of current photosynthate translocated to roots was positively correlated with the size of the root system and negatively correlated with clipping production. Kentucky bluegrass cultivars which partition more energy to roots appear more likely to produce quality turf. Of the cultivars tested, ‘Enmundi’ possessed the most favorable energy distribution pattern and produced a quality turf.
Optimum Crop Water Application as Affected by Uniformity of Water Infiltration1
Authors: Letey J. , Vaux H. J. , Feinerman E.
Published: July 2010

Economic analyses of irrigated agriculture stress that yield levels which maximize profits can be attained with less water than maximum yields. A premise of such analyses is that irrigated soils have perfectly uniform rates of infiltration. A general method for evaluating the effects of nonuniform infiltration rates on optimal levels of water application is developed. Empirical analyses of the implications of non‐uniform infiltration rates on optimal levels of applied water, yields, and profits are reported for corn (Zea maysL.) and cotton (Gossypium hirsutumL.). The results are critically influenced by the nature of the water yield relationships postulated for these crops. For corn, where excessive water applications apparently have no effect on yield, nonuniform conditions reduce yield and profit. These outcomes can be offset by increasing water applications and optimal levels of applied water increase as the degree of uniformity declines. For cotton, nonuniformity leads to decreases in yields and profits that cannot be offset by increased water applications. This is attributable to the apparent sensitivity of cotton yields to excessive applications of water. For both crops, increases in the price of water provide little incentive to improve the uniformity of infiltration. The results demonstrate that conventional economic analyses which ignore infiltration uniformities, underestimate optimal levels of applied water, often substantially.
Yield Reduction from Defoliation and Plant Cutoff of Determinate and Semideterminate Soybean1
Authors: Pickle C. S. , Caviness C. E.
Published: July 2010

Research has been conducted on the response of determinate and indeterminate soybean [Glycine max(L.) Merr.] to various plant‐damage treatments, but information is limited on the response of genotypes with a semideterminate growth habit. Our objective was to determine the yield response of a determinate cv., Forrest, and a semideterminate strain, R74‐334, to different levels of defoliation and plant cutoff at two growth stages. Treatments consisted of plants being cut off at half height, cut off at half height and defoliated below the cut, or completely defoliated. The treatments were applied to 25, 50, 75, or 100% of the plants at growth stages V5 and R3. These field experiments were conducted on a Captina silt loam (fine‐silty, mixed, mesic Typic Fragiudult) during two growing seasons. Mean yields of Forrest were significantly higher than those of R74‐334 during both years. Most of the treatments at V5 did not significantly decrease yield and in three treatments significantly increased yield. Yields generally were significantly reduced at R3 by treatments involving 50% or greater plant damage. The greatest reduction in yield occurred when 100% of the plants were cut off at half height and then completely defoliated. Yield of Forrest was reduced by 51% and that of R74‐334 by 44% with this treatment. The yield of both genotypes was reduced 33% by 100% defoliaton at stage R3. None of the first order interactions involving genotypes was statistically significant, which indicates that the two genotypes responded similarly to these plant‐damage treatments. Although there was some variability in the response of the genotypes to certain treatments, the data indicate that determinate and semideterminate soybean recover about the same from plant cutoff and/or defoliation. Therefore, the same loss values that have been developed for determinate soybean probably should be used for semideterminate types.
Distribution Pattern of Yield Components in ‘Braxton’ Soybeans1
Authors: Ramseur E. L. , Wallace S. U. , Quisenberry V. L.
Published: July 2010

Nodal and other distribution patterns of seed yield and yield components are useful in modeling soybean [Glycine max(L.) Merr.] growth, in analyzing the factors responsible for yield differences between experimental treatments, and in predicting yield. The purpose of this study was to determine the influence of irrigation and intrarow spacing on the distribution of yield and yield components in a determinate soybean cultivar. ‘Braxton’ soybeans were grown in 0.91 m rows on a Cecil sandy loam soil (clayey, kaolinitic, thermic Typic Hapludults) at intrarow spacings of 43, 61, 102, and 305 mm between plants and under three irrigation treatments: full‐season irrigation (FSI), irrigation beginning at bloom (BI), and no irrigation (NI). At maturity, samples were collected to determine pod number, seeds per pod, seed number, yield, and single seed weight for the main stem positions at each node and for the branches originating at each node. Branches contributed more pods, seeds, and yield than did main stems in all treatments, while seeds per pod and single seed weight were similar on stems and branches. Increases in intrarow spacing increased seed number and yield on branches and decreased pod number, seed number, and yield on the stems. Irrigation had little influence on the branch/stem ratios of yield components. Full‐season irrigation and BI had greater numbers of pods, numbers of seeds, yield, and seeds per pod on stems and branches and greater single seed weight on stems than did NI. With the exception of stem seeds per pod which was greater for BI, there were no differences between the two irrigated treatments. Seed number, pod number, and yield were maximized in the lower half of the nodes whereas seeds per pod and single seed weight were greatest in the upper nodes. The upper six nodes contributed the least to yield in all treatments. Increases in intrarow spacing increased the contribution of the lower nodes to yield whereas irrigation decreased the relative contribution of the lowest nodal division. We concluded that the large contribution of lower nodes to yield was due to the large proportion of yield borne on branches produced from lower nodes. Increases in spacing resulted in greater contribution to yield of these large branches and thus to a greater concentration of yield at lower nodes. Irrigation influenced distribution of yield through influences on distribution of all yield components.
Annual Bluegrass Seedhead Emergence as Predicted by Degree‐Day Accumulation1
Authors: Danneberger T. K. , Vargas J. M.
Published: July 2010

Seedhead production of annual bluegrass (Poa annuaL.) during the spring reduces annual bluegrass root production and disrupts the aesthetic and playing qualities of the turf. A method of predicting when annual bluegrass seedheads visually emerge through maximum production would be a benefit to turf managers in that management practices such as vertical mowing and core cultivation could be suitably adjusted. A model to predict the number of seedheads from visual emergence through maximum production for a perennial annual bluegrass turf was developed from three field locations in Michigan. The proposed model is seedhead no. = −6249.4 + 41.099 (DD) − 0.08573 DD2+ 0.0000575 DD3where DD = degree‐day accumulation above 286 K beginning April (R2= 0.65).
Tall Fescue and Kentucky Bluegrass Response to Fertilizer and Lime Seed Coatings1
Authors: Hathcock A. L. , Dernoeden P. H. , Turner T. R. , McIntosh M. S.
Published: July 2010

Slow establishment of turfgrasses from seed is frequently associated with inadequate or improper application of fertilizer and lime. Coating of these items on seed may enhance germination and seedling growth, and reduce time and energy involved in seedbed preparation, particularly when establishing turf on steep slopes or over large areas of land. The objectives of this greenhouse study were to determine the effects and potential benefits of coating ‘Kentucky‐31’ tall fescue (Festuca arundinacea Schreb.) and ‘Adelphi’ Kentucky bluegrass (Poa pratensis L.) seed with various rates and combinations of N, P, and K fertilizers and lime (L). Seedlings were grown in either a Sassafras sandy loam (fine‐loamy, siliceous, mesic Typic Hapludult) or an Evesboro sandy loam (mesic, coated Typic Quartzipsamment) soil. Seed of both species coated with treble superphosphate exhibited little or no germination. The harmful effect of treble superphosphate seed coatings was probably due to hydrogen ion toxicity to developing embryos. Dicalcium phosphate (P‐source), urea (N‐source), sulfate of potash (K‐source), dolomitic limestone, and seed coating adhesives (Methocel A‐15 and gum arabic) had no deleterious effects upon seed germination or seedling growth. Seed of both species coated with P (22 kg ha−1) alone or in combination with N (24 kg ha−1) generally exhibited significantly improved germination percentages when compared to other treatments. Seedlings from NP and NPKL treatments generally exhibited improved growth compared to seedlings grown without N and P combined. This study provides evidence that coating seed with L and fertilizer improves germination and seedling development in Kentucky bluegrass and tall fescue. Seed coatings therefore may provide an alternative to soil incorporation of lime and fertilizers in situations where proper seedbed preparation is not feasible.
Nitrogen Uptake Patterns of Potatoes with High‐Frequency Sprinkler‐Applied N Fertilizer1
Authors: Lauer D. A.
Published: July 2010

In order to understand utilization of N by Russet Burbank, a commonly grown indeterminate potato (Solanum tuberosum L.) cultivar, it is necessary to determine the partitioning of N in the plant. Fertilizer N efficiency is closely related to the latter. The objective of this research was to examine differences in N uptake patterns of Russet Burbank potatoes with N applied at excessive, adequate, and deficient levels in daily sprinkler irrigation. The N levels were selected on the basis of statistical significance of yield response to N fertilization. Experiments in 1980 and 1981 were done on a Quincy sand to loamy sand (mixed, mesic, Xeric Torripsamments) typical of coarse‐textured soils used for potato production in the Western United States. Daily mid‐season applications of a urea‐NH4NO3 solution were made for about 10 weeks through solid set sprinklers. Samples of vines and tubers were collected weekly and analyzed for total N. To show partitioning and time changes of vine and tuber N, regression curves were fitted to data for N uptake with time after emergence. Rate of N uptake functions were derived and used to determine N sink dominance by vines or tubers. At fertilizer rates greater than adequate for optimum tuber yield, the excess N showed up as increased N in vines and tubers with vines as the dominant N sink. At adequate and deficient N levels tubers were dominant N sinks, however, the deficient plants did not have a sufficient N supply for optimum yield. A desirable N uptake pattern is associated with the following: (i) A fertilizer N level that is adequate such that tuber yield and economic return on fertilizer investment are optimized which is about 340 kg N/ha for these experiments and (ii) The tubers express N uptake dominance (highest rate) from the start of rapid tuber development causing peak quantity of vine N uptake in the first one‐third to one‐half of the post‐emergent growth period.
Seed Yield Response of Three Switchgrass Cultivars for Different Management Practices1
Authors: Kassel P. C. , Mullen R. E. , Bailey T. B.
Published: July 2010

Switchgrass (Panicum virgatum L.) is a valuable warm‐season native forage grass in Midwest grazing systems prompting interest in seed production to obtain adequate amounts of seed for planting purposes. Switchgrass seed production studies, however, have been primarily conducted in the Great Plains states. This study was conducted to evaluate cultivar response to row spacing and N fertilization for increasing seed yields in a more humid area of the species' natural adaptation. ‘Cave‐in‐Rock’ (C), ‘Blackwell’ (B), and ‘Pathfinder’ (P) switchgrass were established on a Webster loam (fine‐loamy, mixed, mesic Typic Haplaquoll) soil near Ames, IA, in 1978 in 20‐, 60‐, and 100‐cm rows and fertilized with N at 0, 90, and 180 kg ha−1 in 1979 and 1980. Seed yield and selected seed yield components were measured in 1979 and 1980. Seed yields averaged over 2 years, three N levels and three row spacings were 908, 319, and 388 kg ha−1 for C, B, and P, respectively. Greater lodging resistance, and greater seed yields in response to increased N level and decreased row spacing, contributed to the significantly greater seed yields of C. Seed yields of B and P were similar for all N and row‐spacing treatments. Cultivar rankings in percent fertile tillers varied between years. Inflorescences per unit area did not differ among cultivars, but total seed weight infloresence−1 averaged over years was 268 g for C, which was 54 and 40% greater than for B and P, respectively. Total seed weight inflorescence−1 seemed to be the most important seed yield component, followed by 100 seed weight for explaining seed yield differences among cultivars. Cave‐in‐Rock showed superior lodging resistance and a greater potential for increased seed production in narrow rows and at higher N levels in 2‐ and 3‐year‐old stands. Results showed that N management and row spacing of young stands of switchgrass grown for seed production in the humid Midwest varied according to the cultivar used. Cultivar susceptibility to lodging may be the most limiting factor to obtain high seed yields of some cultivars in the more humid areas of natural adaptation of switchgrass.
Effects of N and Growing Season on Root‐Rhizome Characteristics of Turf‐Type Bermudagrasses1
Authors: Horst G. L. , Baltensperger A. A. , Finkner M. D.
Published: July 2010

Root‐rhizome growth responses of bermudagrasses (Cynodon spp.) in relation to shoot growth interactions with the environment and cultural systems are not well understood. Effects of four N levels on the root‐rhizome organic matter, root viability, and turf color response of five bermudagrass cultivars grown on a Thermic, Typic, and Torrifluvent soil, were determined in the field for two spring shoot initiation periods. Significant differences in rate of decline during spring and increase during the summer growing season in root‐rhizome organic matter were observed for ‘Common’, ‘Tifgreen’, ‘Santa Ana’, ‘FB‐49’, and ‘Texturf‐10’ cultivars. ‘Tifgreen’ was the most responsive and ‘Common’ the least to changes in season and fertilizer N levels. Root viability scores of all cultivars increased during the spring of 1981, declined slightly during the summer of 1981, and declined moderately from 3.5 to 2.7 during spring 1982. Nitrogen application reduced the rate of decline in spring 1982. There was no significant interaction of bermudagrass cultivar × N level for root‐rhizome organic matter, visual root viability, or turf color.
Early‐, Mid‐, and Late‐Spring Establishment of Switchgrass at Several Seeding Rates1
Authors: Vassey T. L. , George J. R. , Mullen R. E.
Published: July 2010

Concerns of forage producers about seed cost and difficult stand establishment have limited the popularity and use of switchgrass (Panicum virgatum L.) as a summer forage alternative in the humid northern USA. ‘Cave‐in‐Rock’ switchgrass was seeded with atrazine (2‐chloro‐4‐ethylamino‐6‐isopropyl amino‐1,3,5‐triazine) for weed control in 1981 and 1982 on a Webster‐Nicollet soil complex (fine‐loamy, mixed, mesic, Typic Haplaquoll‐Aquic Hapludoll) at three seeding dates (April, May, and June) and five rates, ranging from 3.4 to 16.8 kg pure live seed (PLS) ha−1. Precipitation patterns primarily accounted for differences in mean seedling numbers of 27.8,13.0, and 28.0 seedlings m−1 of row for April, May, and June seeding dates, respectively. Mean tiller numbers of 118 m−1 in 1981 and 131 m−1 in 1982 suggest that tillering compensated for observed differences between years in initial seedling number, and producers should not hastily attempt to reestablish new seedings which initially appear to be marginal. Greater seeding rates increased seedling number, tiller number, and forage dry matter (DM) yields, but slightly decreased forage in vitro dry matter disappearance (IVDMD) and crude protein (CP). Seeding date had a greater effect than seeding rate on switchgrass forage yield and quality. Seeding‐year forage DM yields were 8.5, 6.5, and 4.5 Mg ha−1 for April, May, and June seedings, respectively. Forage IVDMD and CP concentrations were greatest for June (619 and 120 g kg−1, respectively) and least for April (524 and 84 g kg−1, respectively) seeding dates. Results suggest that highly productive switchgrass stands can be obtained during the establishment year with mid‐April to early May seeding dates at rates of only 3.4 kg PLS ha−1 when atrazine is used for weed control.
Soybean Irrigation Serially Timed During Stages R1 to R6. I. Agronomic Responses1
Authors: Kadhem F. A. , Specht J. E. , Williams J. H.
Published: July 2010

Previous research has shown that irrigation timing during the reproductive development of soybean [Glycine max (L.) Merr.] J genotypes is a crucial determinant in ultimate yield response. To obtain more detailed information on this relationship we evaluated the agronomic responses of 16 soybean cultivars to nine irrigation treatments in a 3‐year field experiment. The experiments were conducted in 1980, 1981, and 1982 near Mead, NE on a Sharpsburg silty clay loam (fine, montmorillitic, mesic Typic Arguidoll). In treatments T1 thru T7, only a single irrigation was applied, which coincided with the average R stages 1.1, 2.5, 3.7, 4.7, 5.6, 5.9, and 6.4, respectively. “Check” treatments included T0, which was not irrigated, and T8, which received a total of seven irrigations coincident with those for T1 thru T7. Averaged over years and cultivars, the seed yield responses (kg/ha) were: T0: 3470c, T1: 3595abc, T2: 3530bc, T3: 3740a, T4: 3670ab, T5: 3630abc, T6: 3575bc, T7, 3560bc, and T8: 3540bc. The irrigation treatment X cultivar interaction was significant, primarily because T3 (R3.7) or T4 (R4.7) generally resulted in the highest yields for indeterminate cultivars, whereas T8 resulted in the highest yields for determinate cultivars. Averaged over irrigation treatments and years, the determinate cv. Hobbit was the highest yielding, both with and without irrigation. Significant increases in plant height, nodes/plant, and lodging occurred with the T1, T2, T3, and T8 treatments, but only with the indeterminate cultivars. Precise irrigation timing and proper cultivar choice seem to be crucial if high yields with minimum lodging are to be attained.
Equivalent Wind‐Erosion Protection from Selected Growing Crops1
Authors: Armbrust D. V. , Lyles Leon
Published: July 2010

The wind erosion equation, which estimates annual potential erosion, requires that all vegetation (dry weight per area) be expressed as a small grain equivalent (SG)e. Wind‐tunnel tests were used to determine that equivalent for five growing crops. These are corn (Zea maysL.), cotton (Gossypium hirsutumL.), grain sorghum [Sorghum bicolor(L.) Moench], peanuts (Arachis hypogaeaL.), and soybean [Glycine max(L.) Merr.] in rows both perpendicular and parallel to flow. Compared with the small grain standard, all the growing crops evaluated in rows perpendicular to flow effectively prevented erosion. Because measured or estimated amounts of aboveground biomass are needed in determining (SG)es, simple power equations relating biomass to plant height were developed. For short‐term application of the wind erosion equation by crop stage period or in models with daily time steps, an equation was derived for calculating (SG)e from time‐after‐emergence growth curves.
Effect of Potassium Fertilizers on Malting Barley Infected with Common Root Rot1
Authors: Timm C. A. , Goos R. J. , Johnson B. E. , Sobolik F. J. , Stack R. W.
Published: July 2010

Malting barley (Hordeum vulgareL.) in North Dakota has a history of yield and quality responses to small additions of KCl fertilizer on soils with ample native supplies of exchangeable potassium (K). Five field experiments were established in central or western North Dakota in 1983 to determine if a chloride (Cl)‐induced repression of common root rot, incited by Cochliobulus sativus, was a possible explanation for these past responses. The soils were fine loamy Haploborolls, Argiborolls, or Haplaquolls with greater than 800 kg K ha−1exchangeable K in the plow layer. Experimental design was a factorial combination of two K rates, 23 and 94 kg K ha−1, by two K sources, KCl and K2SO4, plus a control treatment. A randomized complete block design with five or six replicates was employed. Fertilization with KCl significantly decreased root rot incidence at the boot stage at two of five sites and significantly decreased disease severity at the dough stage at three of the five sites. The high rate of KCl visually reduced the severity of spot blotch symptoms on the flag leaves at one site. Nitrate concentrations in plant foliage tended to be depressed at the highest rate of KCl. Chloride concentrations in plant foliage were dramatically increased by KCl application, although concentrations of Cl in control treatments appeared adequate enough to preclude an actual Cl nutritional deficiency. Grain yields were significantly increased by the high rate of KCl at one site. Fertilization with K2SO4significantly increased disease severity at two sites but otherwise had no effect on disease incidence, severity, or grain yield. This research substantiated that Cl‐induced disease repression may explain the history of KCl response in North Dakota, but the reason for this effect is not known.
Potential Yield Response of Corn to Treatments that Conserve Fertilizer Nitrogen in Soils1
Authors: Blackmer A. M.
Published: July 2010

Recent 15N‐tracer studies have provided evidence that a substantial portion of the fertilizer N applied for corn (Zea mays L.) production in Iowa may be lost by leaching and (or) denitrification before plants have an opportunity to utilize this N. Because this finding seems contradictory to the results of studies showing that corn yields usually are not increased significantly by treatments known to reduce these losses, a study was conducted to assess the sensitivity of yield response measurements for evaluating the cost‐effectiveness of using treatments that prevent losses of N from soils. Models were developed from responses observed to N fertilizers in the long‐term crop rotation experiments conducted at various locations in Iowa. These models were used to identify combinations of conditions (rates of N application, percentages of fertilizer N saved by the treatment, and sufficiency levels of soil‐derived N) that could be expected to cause statistically significant yield increases from ideal treatments in studies having various levels of precision. Ideal treatments were considered to be 100% effective at preventing losses of fertilizer N and to have no effects other than increasing the availability of fertilizer N to plants. The results suggest that many experiments to evaluate the cost‐effectiveness of treatments that prevent losses of fertilizer N have been conducted under conditions where statistically significant yield responses could not have been expected, even if the treatments were cost‐effective for the crop producer. This finding indicates a need to reevaluate the methodology commonly used to evaluate the cost‐effectiveness of using treatments that reduce losses of fertilizer N from soils.
Irrigation and Planting Date Effects on Soybean Grown on Clay Soil1
Authors: Heatherly L. G. , Elmore C. D.
Published: July 2010

In the southern Mississippi River alluvial plain, adverse weather conditions and the time required for seedbed preparation can often cause delays of 2 to 3 weeks in planting soybean [Glycine max (L.) Merr.] on fine‐textured soils. Because about 2.6 million ha of these soils are planted to soybean, we conducted field experiments in 1980, 1981, and 1982 on Sharkey clay (Vertic Haplaquept, very‐fine, montmorillonitic, thermic) to determine if yields and yield components of mid May (early) and late May or early June (late) plantings would be similarly affected by irrigation. Plantings of ‘Bedford’ and ‘Bragg’ or ‘Braxton’ were made each year and furrow irrigation was initiated at growth stage R1 (I) and continued through stage R6 on designated plots. A nonirrigated (NI) treatment received only rainfall. Planting date did not significantly affect yield in the NI plots in any year, although the trend each year was toward higher yields from the late plantings. With the I plots, seed yields from the early plantings of 1980,1981, and 1982 averaged 65,370, and 475 kg ha−1 more than from the later plantings, respectively, with the increase in 1982 being significant (P = 0.02). Irrigation of the early planting increased average yields by 1970,2020, and 1490 kg ha−1 in 1980,1981, and 1982, respectively; with the late planting, yield increases averaged 1730,1285, and 975 kg ha−1 for the same years. Increased number of seed was responsible for most or all of the yield increases resulting from irrigation. Irrigation of both plantings essentially ensured canopy closure of all cultivars. These results indicate that maximum benefit derived from irrigation applied to soybean grown on a clay soil can be realized if plantings are made in mid‐May.
Leaf Number at Topping and Yield, Grade Index, and Leaf Chemistry of a Mammoth‐Type Tobacco1
Authors: King Mark J.
Published: July 2010

Tobacco (Nicotiana tabacum L.) cultivars containing a mammoth gene have not been evaluated at leaf numbers greater than 18 to 20 leaves per plant. In addition, they have not been evaluated with respect to potential for mechanical topping. Flue‐cured tobacco cultivar NC 22NF containing the mammoth gene, was grown in 1982, 1983, and 1984 at Blackstone, VA. Plants were topped (apical meristem removed) to determine the effect of leaf number per plant on yield, grade index, and leaf chemistry at constant soil fertility. Leaves remaining on the plant after topping were 14, 18, 22, and 26 per plant. Yield increased with leaf number. This study demonstrated that the accepted practice of topping at 18 to 20 leaves may be extended to 26 leaves, increasing yield and value with no detrimental alteration in leaf chemistry or decline in leaf grade index. The lack of difference in grade index compared to earlier studies may be due to the different genomes. In a duplicate set of treatments, four additional leaves per plant were allowed to develop before being removed to study the effects on yield, grade index, and leaf chemistry at 14, 18, 22, and 26 leaves per plant. The delay in topping until four additional leaves were produced did not significantly decrease yield, grade index, or leaf chemistry and may be advantageous for mechanical topping.
Phosphorus Uptake from Soil Layers Having Different Soil Test Phosphorus Levels1
Authors: Pothuluri J. V. , Kissel D. E. , Whitney D. A. , Thien S. J.
Published: July 2010

The effect of available P in subsoil on plant uptake of P from surface soil layers and consequently on fertilizer recommendations is largely unknown. Our objective was to determine how much P may be removed by crops from subsurface soil layers and how the subsurface P level influences crop drawdown of P from the surface layer. Soil columns were prepared that contained all four possible combinations of low or high P levels in the surface soil and low or high P levels in the subsurface layer. The soil used was a Farnum fine sandy loam (fine‐loamy, mixed, thermic Pachic Argiustoll). Phosphorus removal was monitored by growing hybrid sorghum‐sudangrass [Sorghum bicolor (L.) Moench cv. ‘Honey Chow’] 84 days with an intermediate harvest after 35 days. Compared to when both the surface and subsurface layers had low P levels, P uptake increased when either or both layers had high P levels. Root growth and morphology responded to the P level of the soil layers. For all conditions, P uptake demonstrated a high correlation (R2=0.94) to an accessibility factor defined as the product of the available P level and root length summed for both soil layers. Comparing ratios of crop P removal to the change in soil test showed that P drawdown from the surface layer was reduced when the P‐supplying capacity of the subsurface layer was high. We concluded that available P in the subsurface layer can supply P to the crop, especially if the surface layer cannot supply sufficient P to meet crop demand. These results suggest that subsoil fertility should be considered in evaluating P available to crops and in estimating crop drawdown of available P.
Forage Quality Responses of an Aeschynomene‐Limpograss Association to Grazing Management1
Authors: Sollenberger L. E. , Quesenberry K. H. , Moore J. E.
Published: July 2010

Low crude protein concentration (CP) in limpograss [Hemarthria altissima (Poir.) Stapf et C.E. Hubb.] forage may limit the performance of grazing animals. Aeschynomene (Aeschynomene americana L.) is a legume that has potential with limpograss. Effects of grazing management on aeschynomene, limpograss, and total canopy forage quality were measured on a sandy, siliceous, hyperthermic UItic Haplaquod in 1983 and 1984. Experimental variables were (i) limpograss stubble height when aeschynomene was seeded, (ii) legume seedling growth stage when early season grazing of limpograss ended, and (iii) aeschynomene height when summer grazing was initiated. After initiation of summer grazing, all pastures were grazed rotationally every 5 weeks. Aeschynomene leaf had CP and in vitro digestible organic matter concentrations (IVDOM) of approximately 250 g kg−1 DM and 700 g kg−1 OM, respectively. Legume leaf quality was minimally affected by grazing management, but stem quality and leaf/stem ratio decreased as initiation of grazing was delayed. Limpograss CP was generally less than 40 g kg−1 DM. Depending on year and grazing treatment, 8 to 23% aeschynomene was required in herbage accumulated for the CP of herbage consumed to be 70 g kg−1 DM or higher. When limpograss was grazed for 2 weeks after aeschynomene seedlings exserted two true leaves, grass competition to the establishing legume was reduced, percentage legume in the sward was increased, and CP in herbage consumed was maximized. The IVDOM of total herbage accumulated decreased linearly as initiation of grazing was delayed. Seasonal consumption of DOM was greater in treatments where grazing was initiated at 0.20 instead of 0.60 or 0.80 m, despite OM accumulation being greater for the taller initiation heights. Peak legume production occurred in late summer when limpograss quality was low, and these data suggest that incorporation of aeschynomene into grass swards may improve animal performance during this period.
Spring Grazing Effects on Components of Winter Wheat Yield1
Authors: Sharrow S. H. , Motazedian I.
Published: July 2010

Livestock grazing of cereal grain crops during the early portion of their growing cycle is practiced to some degree in many parts of the world. While a substantial body of literature relating grain yields to defoliation practices has been accumulated, most of this work lacks detail concerning the effects of grazing on individual components of plant yield. Reports of grazing effects on grain yield have been quite variable, ranging from substantial decreases to modest increases in grain yield. Understandably, many grain producers are confused about the exact impact that livestock grazing has on their grain crop. The effects of a single intense March‐grazing by sheep, on the components of biomass yield in 'Yamhill' soft white winter wheat (Triticum aestivum L. em Thell.) were evaluated near Corvallis, OR, during the 1979‐to‐1981 harvest years. Grazing increased total plant biomass yield each year. The greatest increase was in the grain component, which averaged 16% greater on grazed than on ungrazed plots 'during the 3 yr of the study. Contrary to widely held opinion, grazing had no effect on the number of fertile flower heads produced by the crop. Likewise, grazing did not affect either the number of seeds produced per spikelet or the average seed weight. Increased grain yield on grazed plots largely resulted from an increased number of fertile spikelets produced per wheat head on those plots. These data suggest that components of wheat grain yield that are determined prior to tiller elongation may respond to grazing management.
Volatilization of Ammonia from Granular and Dissolved Urea Applied to Turfgrass1
Authors: Titko Steve , Street John R. , Logan Terry J.
Published: July 2010

Urea, applied in either granular or dissolved form, is a commonly used N fertilizer source for turfgrass, and volatilization of NH3 produced by urea hydrolysis is considered to be a major contributor to reduced N fertilizer utilization by established turf. Ammonia volatilization losses from urea applied to turfgrass were studied in a controlled environment chamber. Kentucky bluegrass (Poa pratensis L., var. Merion) sod was placed on a Crosby silt loam soil (fine, mixed, mesic Aerie Ochraqualfs) in 17.5‐L plastic containers with surface areas of 434 cm2. Covers fitted to the containers had intake and exhaust ports such that air could be passed over the sod and NH3 collected in a boric acid trap. Experiments were conducted to examine the effects of temperature, relative humidity, wetting and drying cycles, and irrigation on NH3 loss from surface‐applied urea. Ammonia losses were higher from granular than from dissolved urea in all cases, except where urea application was immediately followed by a 25.4‐mm irrigation: Ammonia loss from granular and dissolved urea increased as temperature increased from 10 to 22.2°C, but there were no significant effects on NH3 loss as temperature increased from 22.2 to 32.2°C. Ammonia losses from dissolved urea at 68% R.H. were greater than losses at 31% R.H., but NH3 loss from granular urea was not significantly affected by relative humidity. Ammonia losses increased rapidly following periodic wetting of the turf fertilized with dissolved urea. Irrigation (25.4 mm) following urea application decreased NH3 losses from both dissolved and granular ureas.
Yield and Quality of Semidwarf and Standard‐Height Sunflower Hybrids Grown at Five Plant Populations1
Authors: Majid Hashim R. , Schneiter A. A.
Published: July 2010

Information on yield and agronomic performance of semidwarf sunflower (Helianthus annuus L.) is limited. The objectives of these field studies were: (i) to acquire information on seed yield and other agronomic characteristics of two semidwarf and two standard‐height sunflower hybrids; and (ii) to determine an optimum plant population for hybrids representing both plant types. Two experimental semidwarf (SD) and two standard‐height (SH) hybrids of similar maturity from Cargill and Sigco research breeding programs were grown at populations of 32 123,49 420,66 717,84 014, and 101 311 plants/ ha over a 3‐yr period (1982‐1984) under dryland conditions at Fargo, Carrington, and Prosper, ND. Yield differences were observed dependent on the hybrid but not on plant type. The Cargill SD and Cargill SH genotypes had similar but higher yields than both 894 SH, a commonly grown hybrid, and Sigco SD, which were not significantly different from each other. Yield differences among hybrids were the consequence of differences in seed weight and seed per head. Cargill SH had the highest oil percentage and test weight. It was concluded that the semidwarf hybrids did not possess any yield superiority when compared to the two standard‐height sunflower hybrids. A plant population of 32 123 plants/ha resulted in the highest yield for hybrids representing both plant types. Plant populations above 32 123 plants/ha decreased yield, seed weight, seed per head, and head diameter, but increased percent oil.
Effects of Nitrogen and Potassium on Growth and Cation Composition of Corn Genotypes Differing in Average Ear Number1
Authors: Ebelhar S. A. , Kamprath E. J. , Moll R. H.
Published: July 2010

Genetic improvements for increased grain yield through selection for prolificacy in corn (Zea mays L.) may affect plant responses to fertilizers. A field study was conducted on a Dothan loamy sand (Typic Plinthic Paleudult) to determine the effects of N and K rates on growth, grain yield, and concentrations of N, K, Ca, and Mg in the leaves of corn genotypes differing in average ear production. Nitrogen rates of 50, 150, and 250 kg N ha−1 and K rates of 0, 50, and 100 kg K ha−1 were used in factorial combination with prolific (Pr), semi‐prolific (SP), and nonprolific (NP) genotypes at plant densities of 34 000 and 68 000 plants ha−1. Leaf weight and grain yield of all three genotypes were increased with N fertilization. Response above 150 kg N ha−1 was relatively small. Yield response to K was obtained at 150 kg N ha~' but not at 250 kg N ha−1 in a year with optimum conditions for yield. Lack of K response at the high N rate was a result of greater uptake of soil K. Nitrogen rate had a greater effect on K uptake than K rate. Leaf concentrations of Ca, Mg, and K increased with N rates and were greatest with the Pr and SP genotypes. The Pr and SP genotypes had considerably higher leaf concentrations of Ca and Mg and total cation concentration than the NP genotype. However, the NP genotype had the highest leaf N concentration. Increasing K rates decreased Ca and Mg concentrations in the leaves but had little effect on total cation concentration.
Intercropping Soybean into Standing Green Wheat1
Authors: Reinbott T. M. , Helsel Z. R. , Helsel D. G. , Gebhardt M. R. , Minor H. C.
Published: July 2010

Scientists and farmers have been evaluating the intercropping of soybean [Glycine max (L.) Merr.] into wheat (Triticum aestivum L.) before harvest as an alternative to doublecropping in the lower Midwest. It was our objective to examine the interrelationships of soybean row spacing, planting date, and N applied to wheat in a wheatsoybean intercropping system. The experiment was conducted near Columbia, MO, in 1983, 1984, and 1985, on a Mexico silt loam (Udollic and Mollic Ochraqualf). Whole‐plot treatments consisted of two cropping systems (conventional and intercropped), drilled and skiprow planting patterns (0.2‐ and 0.8‐m row spacings of soybean), and three soybean planting dates coinciding with wheat growth stages. Subplots consisted of spring applied N treatments (0, 56, and 112 kg ha−1). A wheat‐soybean double crop was also included. Wheat yields were reduced 23 and 16% when soybean was intercropped in the drilled and skiprow patterns, respectively. The date of planting did not significantly (P < 0.05) influence wheat yield in the skiprow patterns. However, wheat yield was significantly (P < 0.05) decreased as planting date was delayed in the drilled pattern because of mechanical damage. Intercropped soybean yielded 27% less than conventional soybean but 28% more than doublecropped soybean over all years and treatments. Drilling soybean at the heading stage of wheat resulted in greatest yields. In 1985, N applied in excess of 56 kg ha−1 produced excessive wheat vegetative growth resulting in competition for light which caused a reduction in drilled, intercropped soybean yield. Where mechanical damage to wheat can be minimized, drilling soybean in wheat at heading can result in optimum intercrop performance.
Effect of Temperature, Moisture, and Soil Texture on DCPA Degradation
Authors: Choi J. S. , Fermanian T. W. , Wehner D. J. , Spomer L. A.
Published: July 2010

Turf managers sometimes experience poor or early loss of control of targeted weeds, even when herbicides are applied at recommended rates. This study was conducted to determine the influence of soil temperature and moisture on the rate of DCPA (dimethyl tetrachloroterephthalate) degradation in soil. The effect of six soil temperatures, three soil moistures, and three soil textures on the degradation of DCPA was measured in the laboratory through HPLC analysis. Soil temperature influenced the rate of DCPA degradation in the following order: 10<<15<<20<25=30>35°C. The average half‐life ranged from 92 d at 10°C to 18 d at 30°C. Soil moisture content influenced the rate of degradation in the following order: low (0.1 kg H2O kg−1 soil)≤ medium (0.2 kg H2O kg−1 soil) = high (0.4 kg H2O kg−1 soil). The average half‐life values of DCPA were 49, 33, and 31 d for the low, medium, and high soil moisture levels, respectively. A mathematical model of DCPA loss was utilized to determine the relative contribution of time, soil moisture, and soil temperature to the rate of degradation. Faster degradation of DCPA was observed from a sand/soil moisture (47.5:52.5, w/w) than from either a sand or a soil (Flanagan silt loam [fine, montmorillonitic, mesic Aquic Argiudoll]). It was concluded that the dissipation rate of DCPA is largely dependent on soil environmental conditions including soil temperature, soil moisture, soil texture, and the time interval since the application to the soil. Thus, it is suggested that soil environmental factors be considered in determining the timing of second or subsequent applications when necessary rather than following a fixed application schedul