Broadcast Plots Research Articles

Fate and transport of antibiotics and antibiotic resistance genes in runoff and soil as affected by the timing of swine manure slurry application

Land application of swine manure slurry is a common practice to supplement nutrients to soil for crop production. This practice can introduce antibiotic residues and antibiotic resistance genes (ARGs) into the environment. Field testing is critical in identifying manure management practices effective in minimizing the environmental impacts of manure-borne antibiotic and ARGs. The objective of this study was to determine how the timing of swine manure application relative to rainfall events impacts the fate and transport of antibiotics and ARGs in surface runoff and manure-amended soil. Swine manure slurry was either broadcast or injected on test plots in the field. A set of three 30-min simulated rainfall events, 24 h apart, were initiated on manured plots 1 day, 1 week, 2 weeks, or 3 weeks after the manure application. Results showed that an interval longer than 2 weeks between application and rainfall often significantly reduced the levels of antibiotics and ARGs tested in runoff with the exception of tet(X). For soil samples from broadcast plots, concentrations of two of the three antibiotics tested (lincomycin and tiamulin) decreased substantially in the first two weeks after manure application. In contrast, concentrations of most of the ARGs tested (tet(Q), tet(X), and erm(A)) in soil did not change significantly during the test period. Information obtained from the study can be beneficial in designing manure management practices and estimating the environmental loading of antibiotics and ARGs resulting from manure application.

Soil Arthropod Abundance and Diversity Following Land Application of Swine Slurry

Soil arthropods play an important role in nutrient cycling and maintenance of soil structure, and their abundance and diversity provide an indication of the biological quality of soil. Land application of livestock manure provides crop nutrients and may also impact the soil arthropod community. This study was conducted to quantify soil arthropod abundance and diversity for a period of one year following swine manure application via broadcast or injection. Arthropods were extracted from plot soil samples using Berlese funnels, identified and counted, and the QBS index (Qualita Biologica del Suolo) was calculated for each soil sample. Collembola (Hypogastruridae and Isotomidae) populations were greater (p < 0.05) in the broadcast plots than the injection or control plots. Pseudoscorpiones were more abundant (p < 0.05) in the injection treatment compared to the broadcast and control treatments. Acari populations and the QBS index were not significantly impacted by manure application.

Load-discharge relationships reveal the efficacy of manure application practices on phosphorus and total solids losses from agricultural fields

Eutrophication and sedimentation are pervasive challenges in many agricultural watersheds. Recent research has promoted shallow-disk manure injection as a means of mitigating phosphorus (P) losses in runoff while maintaining the water quality benefits of no-till, such as reduced particulate P and sediment losses. However, the precision and accuracy of field studies seeking to quantify the effectiveness of shallow-disk injection as a P mitigation strategy are substantially constrained by hydrologic variability across spatial and temporal scales. In this study, overland and subsurface flow from twelve plots in central Pennsylvania (PA) were measured and sampled for all P constituents and total solids (TS) from January 2013 to May 2017. We regressed loads of total P (TP), dissolved P (DP), particulate P (PP), and TS against flow depths to evaluate how P and TS losses changed with increasing flow. The results revealed dilution of all P constituents and near-chemostatic behavior (little change in concentration with change in flow) for TS for both application methods. Shallow-disk injection was found to be more effective than broadcasting in promoting dilution of DP, and to a lesser extent, TP. In contrast, the broadcast plots showed stronger dilution patterns than did the injection plots for PP, and there was no difference between application methods for TS. Variability among plots within each manure application practice was largely dependent on relative contributions of overland and subsurface flow due to increased dilution of P by subsurface flow. Overall, shallow-disk injection appears to be an effective practice to reduce DP and TP losses without negating the erosion-reducing benefits of no-till.

Estrogen Transport in Surface Runoff from Agricultural Fields Treated with Two Application Methods of Dairy Manure.

This study compares two methods of dairy manure application-surface broadcast and shallow disk injection-on the fate and transport of natural estrogens in surface runoff from 12 field plots in central Pennsylvania. Ten natural surface runoff events were sampled over a 9-mo period after fall manure application. Results show that the range of estrogen concentrations observed in surface runoff from the broadcast plots was several orders of magnitude higher (>5000 ng L) than the concentrations in runoff from the shallow disk injection plots (<10 ng L). Additionally, the transport dynamics differed, with the majority of the estrogen loads from the surface broadcast plots occurring during the first rainfall event after application, whereas the majority of the loads from the shallow disk injection plots occurred more than 6 mo later during a hail storm event. Total estrogen loads were, on average, two orders of magnitude lower for shallow disk injection compared with surface broadcast. Independent of the method of manure application, 17α-estradiol and estrone were preserved in the field for as long as 9 mo after application. Overall, injection of manure shows promise in reducing the potential for off-site losses of hormones from manure-amended soils.

Is Pile Seeding Wyoming Big Sagebrush (Artemisia tridentata subsp. wyomingensis) an Effective Alternative to Broadcast Seeding?

Sagebrush plays an important role in the ecological functions of sagebrush steppe plant communities and is a necessary component of habitat for a variety of wildlife including greater sage-grouse (Centrocercus urophasianus). At lower elevations, increased fire frequency associated with exotic annual grass invasion has heightened the need for effective sagebrush restoration strategies, but existing techniques have been largely ineffective. Our objective was to evaluate “pile seeding” (placing mature seed heads on the ground) of Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) as an alternative to broadcast seeding. We used a randomized block design (n = 5) replicated in 2 yr at two contrasting ecological sites in southeastern Oregon. Treatments applied to 100 × 1.5 m plots included 1) pile seeding (four mature seed heads · pile--1 × 10 piles · plot-1), 2) broadcast seeding (0.5 kg pure live seed [PLS] · ha-1), and 3) natural recovery (i.e., nonseeded). Planting occurred in fall 2008 and 2009, and plots were monitored for seedling establishment for three or two growing seasons postplanting. Seedling density was estimated at the plot scale within a 50-cm radius of each seed head pile (“island scale”). In the year following planting, sagebrush seedling density at the plot scale was up to 60-fold higher (P ≤ 0.05) in pile-seeded plots compared to natural recovery and broadcast plots. Seedling mortality was high (up to 98% reduction in density) for pile-seeded plots between the first and second growing seasons postplanting and differences between broadcast and pile-seeded plots dissipated by 2–3 yr postplanting. Although pile-seeding had higher initial density than broadcast seeding, neither technique had sufficient multiyear survival to suggest restoration efficacy at the plot scale. Seedling density at the island scale suggests that pile-seeding may be useful for establishing sagebrush islands, depending on year conditions. Research is needed to determine strategies capable of increasing long-term sagebrush seedling survival.

Seeding Method Influences Warm‐Season Grass Abundance and Distribution but not Local Diversity in Grassland Restoration

Ecological theory predicts that the arrangement of seedlings in newly restored communities may influence future species diversity and composition. We test the prediction that smaller distances between neighboring seeds in drill seeded grassland plantings would result in lower species diversity, greater weed abundance, and larger conspecific patch sizes than otherwise similar broadcast seeded plantings. A diverse grassland seed mix was either drill seeded, which places seeds in equally spaced rows, or broadcast seeded, which spreads seeds across the ground surface, into 24 plots in each of three sites in 2005. In summer 2007, we measured species abundance in a 1 m2 quadrat in each plot and mapped common species within the quadrat by recording the most abundant species in each of 64 cells. Quadrat‐scale diversity and weed abundance were similar between drilled and broadcast plots, suggesting that processes that limited establishment and controlled invasion were not affected by such fine‐scale seed distribution. However, native warm‐season (C4) grasses were more abundant and occurred in less compact patches in drilled plots. This difference in C4 grass abundance and distribution may result from increased germination or vegetative propagation of C4 grasses in drilled plots. Our findings suggest that local plant density may control fine‐scale heterogeneity and species composition in restored grasslands, processes that need to be further investigated to determine whether seed distributions can be manipulated to increase diversity in restored grasslands.

SEMIARID OLD‐FIELD RESTORATION: IS NEIGHBOR CONTROL NEEDED?

Restoration practice suggests that neighbor control is essential in semiarid grasslands, but ecological theory predicts that neighbor effects are relatively small in young fields. We investigated the effectiveness of neighbor control (mowing and herbicide) for establishing native grasses in a recently abandoned field in southwestern Saskatchewan, Canada. We also examined its interactions with common restoration techniques, such as mulching (straw and sawdust) and contrasting sowing methods (drilling, and broadcasting cleaned seeds, cleaning remainders, and native hay). The experiment was repeated over three years to examine the effect of weather. Neighbor control had no effect on establishment and rarely any effect on first‐year survival. This contrasted with significant effects of neighbor control on community and ecosystem‐level variables (species richness, water, N). The lack of neighbor effects is concordant with theory which predicts low competition intensity from ruderal annuals. Establishment in seeded plots varied two‐fold among years in drilled plots and 50‐fold in broadcast plots, and it was lowest during a cool, dry summer. Thus, variables beyond human control are a major factor determining restoration success. Overall, broadcasting was as effective as drilling. The highest long‐term establishment of native species was produced by broadcasting cleaning remainders. Almost no seedlings emerged from plots supplied with native hay. Straw mulch increased soil moisture and available N, and sawdust decreased N, but neither had any long‐term effect on native grasses. Our results suggest that restorations of semiarid old fields should focus less on neighbor control and more on strategies for exploiting suitable years for germination, either by monitoring soil moisture or through repeated seeding.

CONTINGENCY OF GRASSLAND RESTORATION ON YEAR, SITE, AND COMPETITION FROM INTRODUCED GRASSES

Semiarid ecosystems such as grasslands are characterized by high temporal variability in abiotic factors, which has led to suggestions that management actions may be more effective in some years than others. Here we examine this hypothesis in the context of grassland restoration, which faces two major obstacles: the contingency of native grass establishment on unpredictable precipitation, and competition from introduced species. We established replicated restoration experiments over three years at two sites in the northern Great Plains in order to examine the extent to which the success of several restoration strategies varied between sites and among years. We worked in 50-yr-old stands of crested wheatgrass (Agropyron cristatum), an introduced perennial grass that has been planted on >10 × 106 ha in western North America. Establishment of native grasses was highly contingent on local conditions, varying fourfold among years and threefold between sites. Survivorship also varied greatly and increased significantly with summer precipitation. No consistent differences were found between drilling and broadcasting in their effects on establishment, but survivorship was nearly threefold higher in broadcast plots. Plots without seed added, or with native hay added, had almost no seedlings of native grasses. In contrast, broadcasting the residue remaining after cleaning seeds from native hay produced the highest seedling densities of any treatment. Competition from A. cristatum was significantly and consistently reduced through annual application of a generalist herbicide (glyphosate), which increased native grass establishment and survivorship and the richness and total cover of native species. Herbicide decreased standing crop and increased soil moisture and available nitrogen. A. cristatum was controlled without suppressing native vegetation, both by spraying in early spring, which selectively killed the cool-season A. cristatum, and by application with a wick, which selectively killed the taller A. cristatum. A. cristatum persisted over four years, however, in spite of annual herbicide application. A. cristatum cover in control plots increased significantly with summer precipitation. In summary, broadcasting and drilling differed little in their effects on establishment, but broadcasting increased survivorship and will allow the emergence of plant-induced heterogeneity. Competition from introduced species can be reduced but not eliminated by continuing herbicide application. Lastly, the positive relationships between precipitation and both A. cristatum and native seedling survivorship suggest that management should focus on controlling A. cristatum during dry years and on introducing native species during wet years. Corresponding Editor: I. C. Burke.

Root distribution of field-grown crisphead lettuce (Lactuca sativa L.) under different fertilizer and mulch treatment

We determined the seasonal changes in the root system of field-grown crisphead lettuce under different fertilizer treatment (stripe, broadcast, and no-nitrogen (absence of nitrogen)) and polyethylene film mulch treatment. Soil blocks less than 1 L volume were sampled from 1 quarter of a plant's rooting volume and roots were separated from the soil blocks by boiling. The root length was determined by the modified line intersect method. Root development in the broadcast plots was better in the 0–30 cm layer but worse below this depth compared to the no-nitrogen plot. In the stripe plots, the rooting pattern was similar to that in the broadcast plots in the 0–30 cm layer and similar to the no-nitrogen plot below that depth. Roots in the stripe plots showed characteristics of both broadcast and no-nitrogen application. With the mulch, the root length density was the highest in the 0–10 cm layer, while without mulch it was highest in the 10–20 cm layer. The root / shoot ratio for nitrogen absorption was ca. 10%. The 0–30 cm layer accounted for more than 80% of the total root length due to the abrupt increase in soil hardness below this depth. Total root length ranged from 1,021 to 1,931 m plant−1 at harvest (50 cm deep). The fine root length / weight ratio was 363 m g−1 dry root and the fine root diameter averaged 207 μm. Constraints on methodologies such as sampling depth, removal of debris, saving of labor, and core sampling were outlined.

Root distribution of field-grown Chinese cabbage (Brassica campestris L.) under different fertilizer treatment

We determined the seasonal changes in the root system of field-grown Chinese cabbage under different fertilizer treatment (stripe, broadcast, and no-nitrogen application (absence of nitrogen)). Soil blocks less than 1 L volume were sampled from 1 quarter of a plant's rooting volume and roots were separated from the soil blocks by boiling. The root length was determined by the modified line intersect method. The fertilizer treatment did not affect substantially the root development. In deep soil layers, roots developed better in the broadcast plots than in the stripe plots in 1995, but the trend was not clear in 1996. With polyethylene mulch, the root length density of Chinese cabbage was the highest in the 0–10 cm soil layer and it decreased drastically below a 30 cm depth, due to the abrupt increase in soil hardness below this depth. The 0–30 cm layer accounted for more than 70% of the total root length. The root/shoot ratio for the nitrogen content was ca. 1.7%. Total root length ranged from 4,842 to 5,579 m plant−1 at harvest (70 or 80 cm deep). The fine root length / weight ratio was 939 m g−1 dry root and the fine root diameter averaged 92 μm. The differences in the strategy of root development in Chinese cabbage and crisphead lettuce were discussed. Constraints on methodologies such as sampling depth, removal of debris, and saving of labor were discussed.

Quantification of Yield Benefits from Incorporation of Virus-Resistant White Clover Germ Plasm into Grass-Legume Systems

Taylor, N. L., Ghabrial, S. A., Pederson, G. A., and McLaughlin, M. R. 1995. Quantification of yield benefits from incorporation of virus-resistant white clover germ plasm into grass-legume systems. Plant Dis. 79:1057-1061. The performance of the virus-susceptible white clover (Trifolium repens) cultivar Regal was compared in broadcast and spaced-plant plots with three experimental breeding populations (Southern Regional Virus Resistant synthetic [SRVR], Brown Loam Synthetic No 2 [BL Syn. 2] and Florida Experimental No. 4 [FL Exp. 4]) expressing varying levels of resistance to viruses endemic to forage legumes in the southeastern United States. The experimental plots were established with and without grasses in fields at Lexington, Ky., and Mississippi State, Miss., with the objective of comparing the magnitude of yield losses from virus diseases in spaced-plant nurseries with those in broadcast plots that more closely resemble farm conditions. Data from virus incidence in spaced plants in both locations indicated that SRVR had significantly (least significant difference, P = 0.05) lower incidence of peanut stunt virus (PSV) and clover yellow vein virus (CYVV) than Regal. Although significantly lower estimates of PSV and/or CYVV incidence were also obtained with BL Syn. 2 and FL Exp. 4 at some testing dates, there were little or no differences at others. Furthermore, higher estimates of PSV and CYVV incidence were determined for spaced plants grown in plots without grass than those with grass. Unlike PSV and CYVV, incidence of alfalfa mosaic virus was similar among treatments. Data on yield, stand, and virus incidence in broadcast plots closely paralleled those of spaced plants. Percentage of virus incidence in broadcast plots in Kentucky, however, was generally lower than that in the spaced plants. The overall data indicated that the performance of SRVR, based on yield (14 to 55% higher than Regal) and resistance to PSV and CYVV, was superior to the other germ plasms and suggest that without virus resistance improved white clover yields and persistence cannot be obtained.

Land application of poultry litter and water quality in Oklahoma, U.S.A.

With the rapid growth of the poultry industry in Oklahoma, U.S.A., more litter is applied to farm land. Thus, information is required on the impact of applications on regional soil and water resources. The effect of soil and poultry litter management on nitrogen (N) and phosphorus (P) loss in runoff and subsurface flow from four 16 m2 plots (Ruston fine sandy loam, 6 to 8% slope) was investigated under natural rainfall. Plots under Bermudagrass (Cynodon dactylon) received 11 Mg litter ha−1, which amounts to contributions of approximately 410 kg N and 140 kg P ha−1 yr−1. In spring, litter was broadcast on 3 of the plots; the upper half of one and total area of the other two. One of the total-area broadcast plots was tilled to 6 cm, the other remained as no till. The fourth plot served as a control. Relative to the control, litter application increased mean concentrations of total N and total P in runoff during the 16-week study for no-till (15.4 and 5.8 mg L−1) and tilled treatments (16.7 and 6.1 mg L−1). However, values for the half-area application (5.6 and 2.0 mg L−1) were similar to the control (5.7 and 1.3 mg L−1). Interflow (subsurface lateral flow at 70 cm depth) P was not affected by litter application; however, nitrate-N concentrations increased from 0.6 (control) to 2.9 mg L−1 (no till). In all cases, < 2 % litter N and P was lost in runoff and interflow, maintaining acceptable water quality concentrations. Although litter increased grass yield (8518 kg ha−1) compared to the control (3501 kg ha−1), yields were not affected by litter management. An 8-fold increase in the plant available P content of surface soil indicates long-term litter management and application rates will be critical to the environmentally sound use of this nutrient resource.

Relative Effectiveness of Hill and Row Plots for Evaluating Alfalfa Yield

Plant breeders usually use multiple‐row or broadcast plots grown from 2 to 4 yr to evaluate alfalfa (Medicago sativa L.) populations for yield and agronomic performance. The requirements of land and seed and the cost of evaluation often limit the number of populations that can be evaluated. The objective of this study was to compare the yield of alfalfa populations grown in hill plots planted on either 0.3‐ or 1.0‐m centers and 1‐row (0.5 by 6.1 m) and 6‐row (1.1 by 6.1 m) plots. The study was conducted for 2 yr in Minnesota with 16 alfalfa populations ranging in dormancy, yielding ability, and biological N fixation. The experimental design was a randomized complete block with four replicates at three locations. The strongest association for forage yield between any two plot types was between the 0.3‐m hill plots and the 1‐row plots. Phenotypic and Spearman rank correlations for forage yield between 0.3‐m hill plots and the 1‐row plots in 1984 were 0.73 and 0.67, respectively. No significant correlation was observed in yield between hill plots and 6‐row plots. Yield in 6‐row plots was positively correlated to that in 1‐row plots. A few populations were consistent in rank for forage yield in both years and across all plot types. Forage yield in some populations ranked low in hill plots and high in 6‐row plots, whereas other populations ranked high in hill plots and low in 6‐row plots, illustrating that a population's performance in an evaluation trial could be influenced by the plot type used. Visual estimates of forage yield and actual harvested yield were highly correlated in the hill plots for all three harvests during 1983. These correlations decreased as stands aged, suggesting that use of visual estimates of forage yield would be useful only during the establishment year. Hill plots may be useful in early phases of a breeding program but should not be considered as a replacement for multiplerow yield evaluation plots during the later stages of a breeding program.

Mole Cricket Control on Golf Course Fairways in North Carolina, 1993

Abstract Three granular insecticides were evaluated for the control of mole crickets on the bermudagrass fairway of the 10th hole at Fox Squirrel Golf and Country Club in Brunswick County. The test area was showing damage from a moderate infestation prior to treatment. Plots 16 ft × 75 ft were established and treatments were randomly assigned with four replicates. Surface broadcast treatments were applied using a standard push-type Lesco fertilizer spreader to deliver a weighed portion of chemical to the broadcast plots. All other treatments were applied using a tractor drawn Gandy® slit-seeder modified for granular formulation application and operating at 1.9 mph. Subsurface treatments were applied on 18 Aug and surface treatments were applied the following day. Soil was moist from rain the night of the 17th. Air temperature was 88°F and soil temperature was 84°F. Soil type was mineral with 0.9% humic matter and a pH of 6.1. The test area was irrigated with 0.5 inch of water after the chemicals were applied. Plots were evaluated for fresh damage on 1 Sep (14 DAT) and 15 Sep (21 DAT). Damage evaluations were conducted by using the damage grid method as developed by Dr. Pat Cobb, Auburn University. Five random damage ratings (0—9) were taken from each replicate and an average rating for the plot was determined. All data were transformed Vx + 0.5 prior to analysis.

Evaluation of Granular Insecticides for Mole Cricket Control on Golf Courses in North Carolina, 1993

Abstract A bermudagrass fairway at Brierwood Golf Course in Shallotte was chosen to evaluate rates and methods of application of several granular insecticides for control of the newly hatched nymphs of the tawny mole cricket. Plots 18 ft × 95 ft were established and treatments were randomly assigned with four replicates. The broadcast treatments were applied using a standard push type Lesco fertilizer spreader to deliver a weighed portion of insecticide to the broadcast plots. All other treatments were applied using a tractor drawn Canaan TG70 subsurface granular applicator and overseeder (Canaan Industries, Inc., Dothan, AL) to place the materials one inch deep in the soil. Treatment took place on 28 Jul for all subsurface treatments, 29 Jul for all surface treatment except for the Mocap (7.5 lb [AlJ/acre) and the Crusade (4.0 lb [AI]/acre) surface treatments which were applied on 4 Aug. Air temperature was 100°F. The soil was 90°F and moist at the time of application. Soil type was mineral with 1.5% humic matter and a pH of 6.1. The entire test was irrigated with 0.5 inch of water after the chemicals were applied. Pretreatment sampling showed the presence of young nymphs. Plots were evaluated on 11 (14 DAT) and 25 Aug (28 DAT). Damage evaluations were conducted using the damage grid rating method as developed by Dr. Pat Cobb, Auburn University. Plots were evaluated by randomly placing a grid divided into 9 subsections in each plot and examining each subsection of the grid for fresh damage. A damage rating is given from 0 to 9 depending on the number of squares that contain fresh damage. This was done 5 times/plot and the damage averaged. All data were transformed x + 0.5 prior to analysis. Actual means are presented in the table.

Establishment and Survival of Illinois Bundleflower Interseeded into an Established Kleingrass Pasture

The introduction of perennial legumes into warm-season grass pastures has been shown to improve both forage quality and animal performance. Illinois bundleflower (Desmanthus illinoensis (Michs.) MacM.) appears to have potential for pasture and range interseeding. This study investigated establishment methods and the competitive ability and longevity of this species when interseeded into kleingrass (Panicum coloratum L.) swards. Sabine Illinois bundleflower was drilled or broadcast into a mature kleingrass pasture either intact or suppressed by disking, paraquat (1-dimethyl-4-4 dipyridinium dichloride), or mefluidide (N-[2,4 dimethyl-5 (trifuromethyl) sulfonyl-amino-phenyl]acetamide). Seed was sown in broadcast plots at 6.8 kg PLS/ha compared to 3.4 kg PLS/ha in drilled plots. Establishment data were only collected for 1 year. The establishment year had a wetter than normal spring. Treatment effects on legume establishment could differ substantially from those found in this study in drier years. Both paraquat and disking treatments resulted in good establishment of the legume (greater than 10 seedlings m-2 in the establishment year). With the exception of disked plots, broadcasting at twice the rate of drilled plots resulted in similar seedling legume densities between the 2 seeding methods. Illinois bundleflower proved to be quite competitive under the conditions of this study. The legume component increased from 14% in the establishment year to 52% by the third year after establishment. Individual Illinois bundleflower plants survived for the 4 years of the study. Interseeding increased total plot yield in the second, third, and fourth years after establishment. Interseeded plots produced more biomass than noninterseeded plots 1, 2, and 3 years after interseeding.

Responses of Vegetation and Deer Forage Following Application of Hexazinone

Abstract Vegetation responses were studied on a loblolly pine (Pinus taeda) plantation that had received intensive mechanical site preparation and hexazinone (1 lb/ac a.i.) for herbaceous weed control. Vegetation on plots treated by a broadcast application of granular hexazinone (Pronone® 5G) was compared to vegetation on plots that received a banded (top of bed only) application of liquid hexazinone (Velpar® L). Total plant biomass was significantly greater (P &lt; 0.10) on control plots (2,512 lb/ac, dry wt) than on broadcast (1,089 lb/ac) or banded plots (1,481 lb/ac) in September of the first growing season, but differences disappeared by the end of the second growing season. Total number of plant species on control plots (105) and banded-treated plots (97) was similar, but fewer plant species (60) were found on broadcast-treated plots the first year. At the end of the second growing season, the number of plant species was similar on all treatments. White-tailed deer (Odocoileus virginianus)forage was significantly greater on control plots (1,481 lb/ac) than on broadcast (393 lb/ac) and banded plots (534 lb/ac) in September of the first year's growth, but there were no differences after the second growing season. Pine seedling survival was lower on herbicide treated plots, but seedling height and ground line diameter were greater on herbicide treated plots. South. J. Appl. For. 11(4):176-180.

Inheritance and Backcross Breeding of the Hypersensitive Reaction to Bean Yellow Mosaic Virus in Red Clover1

Bean yellow mosaic virus (BYMV) is an important pathogen of red clover (Trifolium pratense L.). A hypersensitive reaction to the most prevalent strain of BYMV in Kentucky (designated 204‐1) conveys resistance. The objectives of the present study were to backcross the genes for the hypersensitive reaction into 10 clones of ‘Kenstar’ to widen the BYMV resistance of this cultivar and to further investigate the inheritance of resistance. Populations of Fl’s and five backcrosses to each of the 10 parental clones of Kenstar were produced using the clones as recurrent parents and a hypersensitive reacting clone as the nonrecurrent parent. Four Kenstar parental clones were found to possess the hypersensitive reaction, and two had a different type of resistance. Inheritance of the hypersensitive reaction to BYMV strain 204‐1 was similar to that reported earlier. Incorporation of the hypersensitive reaction to strain 204‐1 into the Kenstar clones did not increase virus resistance under spaced‐plant field conditions as compared to Kenstar polycross progenies. Lack of infection in broadcast plots prevented a complete assessment of the potential effect of the hypersensitive reaction. A new strain of BYMV was discovered and designated the red clover or ‘RC’ strain. This strain is similar to previously described isolates of BYMV from soybean, and it was hypothesized that the RC strain may have occurred as a result of the increase in soybean acreage in Kentucky. Phenotypic recurrent selection under spaced‐plant conditions where opportunity exists for infection by many different strains of BYMV and other viruses is suggested as aneffective breeding procedure.

Studies on baby carrot production

Abstract Effects of sowing rates, times, and methods on baby carrot production were investigated. Plant survival averaged approximately 50% 4 weeks after emergence started, and 20% at harvest. In early- and mid-season sowings survival at harvest was 5-10% higher and more consistent from year to year than in late-season sowings. It decreased with increasing sowing rate and was lower after sowing pelleted seed than after sowing natural seed. Survival after sowing with a perforated drum was higher than with a Stanhay drill in early-and mid-season sowings, but in late-season sowings the reverse occurred. In each year yield was similar in early-season, more variable in mid-season, and more variable still in late-season sowings. It increased nearly linearly over the range of populations at harvest at each sowing time. At Levin, yields reached 55 t/ha and at Ohakune, in lighter soil, 70 t/ha. The maximum yield of baby carrots reached a peak at each population for about 1 week in early- and mid-season sowings and for about 2 weeks in late-season sowings. Maximum yield was reached later in late-season sowings and with high populations at harvest. Root quality in precision sown and broadcast plots was similar. Root length decreased with increasing plant population in all sowings. Roots were longer in light soil.

Performance of Rice Composites Dimorphic for Plant Height and for Pubescence1

The effects on yield of two contrasting rice (Oryza sativa L.) plant characteristics (tall vs. short, pubescent vs. glabrous) were studied. These plant types were developed from a cross between a pubescent short cultivar and a glabrous tall one with related parentage. Four plant types, glabrous short, glabrous tall, pubescent short, and pubescent tall, were selected in the F2 and increased in panicle rows in the F3. These panicle rows were composited and evaluated in broadcast plots in the F4.The two short types produced grain yields about 10% greater than the two tall types at optimum N fertility levels. Differences were attributed to a combination of factors including greatly reduced lodging of short types, production of significantly more panicles per unit area, more grains per panicle, and a higher percentage of fertile florets (filled grains). The 100‐grain weight was similar for short and tall types.The pubescent and glabrous leaf and hull characteristics did not affect grain yields significantly but number of grains per panicle and percent of sterile florets were significantly less in the pubescent than in the glabrous types. The four plant types were evaluated at six N fertility levels applied as urea. Rates of application were from 33.5 to 201 kg/ha with 33.5 kg increments. Optimum yields were obtained at 167.5 kg/ha. A progressive increase, in internode length occurred with N rate increments. The lower internodes (fourth and fifth from the top) elongated relatively more than upper ones with increased nitrogen fertilizer applications. Internodes of tall types elongated more than short types with increased N rates.