Coastal Plain Research Station Research Articles

Efficacy of Soil-Applied Systemic Insecticides Against Tobacco Pests, 2014

Efficacy of several soil-applied insecticides (Table 1) was tested against key tobacco pests: TFB, TBW, GPA, and tobacco/tomato hornworms (HW). Two identical experiments were conducted at the Upper Coastal Plain Research Station (UCPRS) in Rocky Mount, NC, and the Lower Coastal Plain Research Station (LCPRS) in Kinston, NC. In each experiment, four replicates of the six treatments, including an untreated check, were arranged an RCB design. Each 0.018-acre plot consisted of four, ca. 25 plant, rows. At LCPRS, pre-transplant greenhouse tray drench (GTD) insecticide applications were made on 7 May 2014 in 1 L water using a CO2-pressurized sprayer fitted a single flat-fan nozzle. Twice the application volume was used to wash the material into the root zone immediately following treatment. GTD treatments were applied as above at UCPRS on 28 Apr. The plants were transplanted on 5 May at UCPRS and 8 May at LCPRS, and in-furrow transplant water (TPW) treatments were applied in ca. 160 gal/A of water using four 5-gal mini-tanks affixed to the planter. Plants received no additional insecticide treatments for the …

Efficacy of Soil Applied and Foliar Materials for Lepidoptera Control in Tobacco, 2014

The efficacy of one soil applied and several foliar insecticides against lepidopteran pests of tobacco were assessed at two locations, the Lower Coastal Plain Research Station (LCPRS) in Kinston, NC and the Upper Coastal Plain Research Station (UCPRS) in Rocky Mount, NC. At each location, eight treatments, including an unsprayed check, were arranged an RCB design with four replicates per treatment (Table 1). Each 0.018 acre plot consisted of four, ca. 25 plant, rows. All plants were treated in the greenhouse with Admire Pro 4.6F (Bayer Crop Sciences) at a rate of 0.6 fl oz/1,000 plants 1–7 d prior to transplanting to control aphids and flea beetles. Plants were transplanted on 8 May at LCPRS and on 5 May at UCPRS, and in-furrow transplant water (TPW) treatments were applied in ca. 160 GPA of water …

Enantioselective Demethylation of Nicotine as a Mechanism for Variable Nornicotine Composition in Tobacco Leaf

Nicotine and its N-demethylation product nornicotine are two important alkaloids in Nicotiana tabacum L. (tobacco). Both nicotine and nornicotine have two stereoisomers that differ from each other at 2'-C position on the pyrrolidine ring. (S)-Nicotine is the predominant form in the tobacco leaf, whereas the (R)-enantiomer only accounts for ∼0.2% of the total nicotine pool. Despite considerable past efforts, a comprehensive understanding of the factors responsible for generating an elevated and variable enantiomer fraction of nornicotine (EF(nnic) of 0.04 to 0.75) from the consistently low EF observed for nicotine has been lacking. The objective of this study was to determine potential roles of enantioselective demethylation in the formation of the nornicotine EF. Recombinant CYP82E4, CYP82E5v2, and CYP82E10, three known tobacco nicotine demethylases, were expressed in yeast and assayed for their enantioselectivities in vitro. Recombinant CYP82E4, CYP82E5v2, and CYP82E10 demethylated (R)-nicotine 3-, 10-, and 10-fold faster than (S)-nicotine, respectively. The combined enantioselective properties of the three nicotine demethylases can reasonably account for the nornicotine composition observed in tobacco leaves, which was confirmed in planta. Collectively, our studies suggest that an enantioselective mechanism facilitates the maintenance of a reduced (R)-nicotine pool and, depending on the relative abundances of the three nicotine demethylase enzymes, can confer a high (R)-enantiomer percentage within the nornicotine fraction of the leaf.

Genetic and epidemiological characterization of Middle Point orbivirus, a novel virus isolated from sentinel cattle in northern Australia

Middle Point orbivirus (MPOV) was isolated in 1998 from a healthy cow pastured at Beatrice Hill farm, Middle Point (formerly Coastal Plains Research Station), 50 km east of Darwin in Australia's Northern Territory. The isolate could not be identified by using conventional serological tests, and electron microscopy indicated that it belongs to the family Reoviridae, genus Orbivirus. Genetic sequencing of segments 2 and 3 revealed that this virus is related to Yunnan orbivirus, an orbivirus known only from China and not previously associated with a vertebrate host. A real-time RT-PCR test was developed to study the epidemiology of this virus in the field. Over 150 previously unidentified viruses isolated from cattle between 1994 and 2006 were positively identified as isolates of MPOV. Serology was used to demonstrate the development of antibody responses to MPOV in cattle from multiple locations across the Northern Territory.

Weed Management in North Carolina Peanuts (Arachis Hypogaea) withS-metolachlor, Diclosulam, Flumioxazin, and Sulfentrazone Systems

Experiments were conducted at the Upper Coastal Plain Research Station near Rocky Mount and at the Peanut Belt Research Station near Lewiston-Woodville in 2002 and 2003. Peanut injury was minimal (< 5%) with all soil-applied programs. S-Metolachlor PRE alone or in mixture with sulfentrazone, diclosulam, or flumioxazin controlled annual grasses similarly (66 to 87%). The addition of imazapic plus 2,4-DB POST increased annual grass control (> 93%). Sulfentrazone or diclosulam in mixture with S-metolachlor were the best PRE options, with 94% and 92% control of yellow and purple nutsedge, respectively, with flumioxazin being least effective at 70%. Diclosulam and flumioxazin in mixture with S-metolachlor were the best PRE options, with 99% and 93%, respectively for common ragweed control, whereas sulfentrazone was the least effective at 65%. S-Metolachlor in mixture with sulfentrazone, diclosulam, or flumioxazin PRE were similar (87 to 90%) for common lambsquarters control. S-Metolachlor in mixture with sulfentrazone, diclosulam, or flumioxazin provided similar levels of entireleaf, ivyleaf, pitted, and tall morningglory control (87, 86, and 87%, respectively) and better than S-metolachlor alone at 64%. Flumioxazin in mixture with S-metolachlor was the best PRE option for control of Palmer amaranth at 96%, whereas diclosulam with S-metolachlor was the best PRE option for control of eclipta at 100%. The prepackaged mixture of acifluorfen and bentazon plus 2,4-DB POST and imazapic plus 2,4-DB POST were similar for all morningglory species (> 96%) and Palmer amaranth control (93 and 97%, respectively). Peanut treated with S-metolachlor plus diclosulam PRE numerically yielded the highest at 3,210 kg/ha, but were statistically equivalent to S-metolachlor plus flumioxazin PRE at 3,040 kg/ha. Peanut treated with imazapic plus 2,4-DB POST yielded the most at 3,400 kg/ha, while peanut treated with a prepackaged mixture of acifluorfen and bentazon plus 2,4-DB POST yielded less (3,070 kg/ha).Nomenclature: 2,4-DB, acifluorfen, bentazon, diclosulam, flumioxazin, imazapic, S-metolachlor, sulfentrazone, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L. AMBEL, eclipta, Eclipta prostrata L. ECLAL, entireleaf morningglory, Ipomoea hederacea var. integriuscula Gray IPOHG, ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE, Palmer amaranth, Amaranthus palmeri S. Wats. AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, purple nutsedge, Cyperus rotundus L. CYPRO, tall morningglory, Ipomoea purpurea (L.) Roth PHBPU, yellow nutsedge, Cyperus esculentus L. CYPES, peanut, Arachis hypogaea L., ‘NCV-11’, ‘VA-98R’

EFFICACY OF SELECTED INSECTICIDES ON CONVENTIONAL COTTON VS. A BOLLGARD II VARIETY AGAINST BOLLWORMS, 2006

Cotton was planted on 3 May in conventional tillage on an Acock very fine sandy loam soil at the Upper Coastal Plain Research Station near Rocky Mount, NC. Plots were 4 rows by 40 ft in a RCB design with 4 replications. All four rows treated with the insecticides indicated in the table, with the exception of the Bollgard II variety, which was untreated. The foliar treatments were made one 3 and 14 Aug with a CO2-powered backpack sprayer calibrated to deliver 8.0 gpa at 50 psi with a single TX-8 Spraying Systems nozzle per row. The initial rate of the experimental insecticide DPX-E2Y45 1.67SC was the same, but differed between the three treatments in the second application. On 7 and 21 Aug and on 6 Sep, 25 randomly selected bolls per plot (100 per treatment) were examined for bollworm injury. The center 2 rows of each plot were harvested with 2-row John Deere mechanical harvester on 20 Oct. All field data were entered into Gylling’s ARM 6.2 software and analyzed via ANOVA with LSD (P = 0.05) values shown in the table.

Yield and Physiological Response of Flue-Cured Tobacco to Simulated Glyphosate Drift

Field trials were conducted in 2001 at the Tobacco Research Station near Oxford, NC, and in 2002 at the Lower Coastal Plains Research Station near Kinston, NC, to determine tobacco yield, injury, and shikimic acid accumulation in response to simulated glyphosate drift. Glyphosate was applied to 12- to 13-cm-high tobacco ‘K326’ early postemergence at 0, 9, 18, 35, 70, 140, 280, 560, and 1,120 (1×) g ai/ha. Crop injury was rated 7 and 35 d after treatment (DAT) and shikimic acid accumulation in leaves at 7 DAT, tobacco yield, and leaf grade index (whole-plant index of harvest interval leaf value) were also assessed. Shikimic acid accumulation and injury symptoms increased similarly as glyphosate rate increased. Glyphosate rates of 140 g/ha (0.125 of recommended rate) or higher resulted in significant crop injury, reduced tobacco yield, and decreased leaf grade index. Shikimic acid accumulation at 7 DAT was inversely related to tobacco yield. Shikimic acid accumulation was found to be an effective diagnostic tool to determine glyphosate drift in tobacco; however, in-season data are needed to correlate shikimic acid accumulation with yield loss.

EVALUATION OF SELECTED INSECTICIDES AGAINST STINK BUGS, 2004A

Cotton was planted on 20 May into a Goldsboro fine sandy loam soil on 36 inch rows near at the Upper Coastal Plain Research Station near Rock Mount, NC. Plot size was 40 ft × 4 rows with 4 replications arranged in a RCB design. The fertility and herbicide programs followed extension recommendations for cotton in this region. Insecticides were applied on 22 Jul with a backpack-type, CO2-pressurized sprayer calibrated to deliver 10.0 gpa at 60 psi with a single TX-10 Spray Systems nozzle 18 inches over the row. On 3 Aug, 25 quarter-sized bolls per plot were picked, placed into plastic bags, and taken into the lab where they were examined for internal damage symptoms within 24 hr. Data were analyzed using ANOVA and means were separated using LSD (P ≤ 0.05).

EVALUATION OF EARLY SEASON APPLICATION OF TRIMAX, CENTRIC, VYDATE AND BAYTHROID FOR COTTON INSECT CONTROL AND YIELD ENHANCEMENT, 2004

Cotton was planted on 11 May on an Acock very fine sandy loam at the Upper Coastal Plain Research Station near Rocky Mount, NC. Plots were 6 rows by 50 ft with 4 replications and the treatments arranged in a RCB design. Insecticides were applied with a CO2-powered backpack sprayer calibrated to deliver 10.0 gpa at 60 psi with a single TX-8 Spraying Systems nozzle per row at square initiation on Jun 15. The Trimax, Centric and Baythroid plots were treated additionally on 22 and 29 Jun. Late season oversprays for stinks bugs and bollworms were made weekly with a Hi-Boy by research station personnel. On 15 July: 1) Fifty-sweep net samples were taken per plot (200/treatment) for all beneficial and pest insects , such as TPB, 2) Two small squares (one terminal and one lateral square) of approx. 1/8 inch length were checked for presence or a missing position in each of 25 randomly-selected cotton plants per plot (200 per treatment) as an indication of plant bug feeding, 3) Yellowed or blackened squares were counted as a missing position, and 4) Twenty-five blooms/plot (100/treatment) were scored as either normal or “dirty” (the presence of blackened or brownish pollen anthers in white blooms). On 3 Sep, number of opened bolls/50 ft was counted, and on 21 Sep when on average approx. half of the bolls had opened across the plots opened, closed and total bolls were counted in 7.5 ft of each plot (30 ft/treatment). The center 2 rows of each plot were harvested on 11Oct with a 2-row John Deere mechanical harvester. Data were analyzed with ANOVA and means were separated using an F-protected LSD (P ≤ 0.05).

COMPARATIVE EFFICACY OF BOLLGARD AND BOLLGARD II AGAINST BOLLWORMS IN STRIP TILL COTTON, 2003

Cotton was planted on 7 May in conventional tillage on a Nahunta sandy loam soil at the Upper Coastal Plain Research Station near Rocky Mount, NC. Plots were 4 rows × 40 ft in 36-inch rows and arranged in a RCBdesign with four replicates. All plots were treated with an Orthene overspray at 0.75 lb (AI)/acre on 24 Jul to enhance bollworm establishment. The treated plots were sprayed on 29 Jul, and on 5, 13 and 19 Aug with a CO2-powered backpack sprayer calibrated to deliver 8 gpa at 50 psi of Karate 2.08 CS at 0.04 (AI)/acre, with a single Spraying Systems TX-8 hollow cone nozzle per row. Twenty five bolls per plot were assessed for bollworms and their damage on 21 Aug and on 1 Oct. No supplemental water was used in this test. Cotton was harvested from the middle 2 rows on 23 Oct with a 2-row John Deere mechanical spindle picker. Data were analyzed using ANOVA and means were separated using LSD (P ≤ 0.05).

COMPARATIVE EFFICACY OF BOLLGARD AND BOLLGARD II AGAINST BOLLWORMS, 2002

Cotton in Table 1 was planted on 3 May on an Coxville sandy loam soil at the Upper Coastal Plain Research Station near Rocky Mount, NC. In Table 2, cotton was planted on 9 May on a Goldsboro sandy loam soil near Richlands. Plots were 40 ft × 4-rows, with 10-ft alleys and four replications arranged in a RCBD. Temik 15 G was applied in furrow at planting at 0.75 lb (AI)/acre for thrips control. Recommended fertility and weed management practices for this area were followed. The treated plots in Table 1 were sprayed on 23 and 29 Jul, and on 6 Aug; Table 2 was sprayed on the same dates, plus on 14 Aug. A CO2-powered backpack sprayer calibrated to deliver 8 gpa at 50 psi of Karate 2.08 CS at 0.04 (AI)/acre, with a single Spraying Systems TX-8 hollow cone nozzle/row, was used for all applications. On 9, 16, and 28 Aug in Table I, and on 9 and 15 Aug in Table 2, 25 bolls/plot were assessed for bollworm (BW) damage and live BW. In both tests, cotton was picked with a two row John Deere mechanical harvester on 8 Nov. All data were entered into Gylling's ARM 6.2 software and analyzed via ANOVA and LSD procedures.

Efficacy of Selected Insecticides Against Bollworms on Cotton, 1997

Abstract Cotton was planted on 12 May in 38-inch rows at the Upper Coastal Plain Research Station near Rocky Mount in central North Carolina. The fertility and herbicide programs followed extension recommendations for cotton in this region. Temik at 5.0 lb (AI)/acre was used at planting. Plot size was 50 ft X 6 rows with 4 replications arranged in a RCBD. Insecticide applications were applied on 20 and 26 Aug with a backpack-type, CO2-pressurized sprayer calibrated to deliver 8.0 gpa at 50 psi with a single TX-8 Spray Systems nozzle 18 inches over the row. All treatments were evaluated for fruit damage and live caterpillars on 2 and 26 Sep. Twenty-five squares and bolls were examined for BW, FAW, and ECB damage and live larvae per replicate (total 100 per treatment). Plots were harvested from the middle 2 rows with a 2-row John Deere picker on 23 Oct. Seed cotton yields were converted to lint cotton/acre using 40% gin turnout. All data were analyzed by ANOVA and DMRT.

Efficacy of Selected Insecticides Against Bollworms on Bt Cotton, 1997

Abstract Cotton was planted on 12 May in 38-inch rows at the Upper Coastal Plain Research Station near Rocky Mount in central North Carolina. The fertility and herbicide programs followed extension recommendations for cotton in this region. Temik at 5.0 lb (AI)/acre was used at planting. Plot size was 50 ft X 6 rows with 4 replications arranged in a RCBD. Insecticide applications were applied on 22 Aug with a backpack-type, CO2-pressurized sprayer calibrated to deliver 8.0 gpa at 50 psi with a single TX-8 Spray Systems nozzle 18 inches over the row. All treatments were evaluated for fruit damage and live caterpillars on 2 and 29 Sep by examining 25 squares and bolls per replicate (total 100 per treatment). Plots were harvested from the middle 2 rows with a 2-row John Deere picker on 23 Oct. Seed cotton yields were converted to lint cotton/acre using 40% gin turnout. All data were analyzed by ANOVA and DMRT.

Boll Worm Threshold Evaluation in Northeastern North Carolina on Bt Cotton, 1997

Abstract Cotton was planted on 12 May in 38-inch rows at the Upper Coastal Plain Research Station near Rocky Mount. The fertility and herbicide programs followed extension recommendations for cotton in this region. Temik at 5.0 lb (AI)/acre was used at planting. Plot size was 50 ft X 6 rows with 4 replications arranged in a RCBD. The entire test was oversprayed with 0.75 lb (AI)/acre Orthene 75S to encourage bollworm establishment via destruction of beneficial arthropods. Karate IE at 0.04 lb (AI)/acre was applied to the DP-5415 and NuCOTN-33b 50% terminal bollworm egg threshold plots on 22 Aug. On 26 Aug, Karate at 0.025 lb (AI)/acre was applied as a 2nd application to the above NuCOTN-33b line at the 20% terminal egg threshold, and as the initial, and only, application to the NuCOTN-33b 3% live bollworm threshold. The final NuCOTN-33b plot never reached the 100% terminal or the 20% fruit egg threshold. All insecticide applications were applied with a backpack-type, CO2-pressurized sprayer calibrated to deliver 8.0 gpa at 50 psi with a single TX-8 Spray Systems nozzle 18 inches over the row. All treatments were evaluated for fruit damage and live larvae on 25 Aug, 4 and 26 Sep by examining 25 squares and bolls per replicate (total 100 per treatment). Plots were harvested from the middle 2 rows with a 2-row John Deere picker on 23 Oct. Seed cotton yields were converted to lb of lint cotton/acre using 40% gin turnout. All data were analyzed by ANOVA and DMRT.

EHDV-1, a new Australian serotype of epizootic haemorrhagic disease virus isolated from sentinel cattle in the Northern Territory

In 1992, a virus (DPP2209) isolated from sentinel cattle located at Coastal Plains Research Station, latitude 12°39′S, longitude 131°20′E, approximately 60 km east of Darwin, Northern Territory. This virus was identified as a serotype of epizootic haemorrhagic disease (EHD) of deer virus previously undescribed in Australia. An additional 17 isolations of this virus were made from eight animals during the period February to May. Electron microscopic studies showed the presence of orbivirus-like structures. Serogrouping ELISA, indirect immunofluorescence assay and the serogrouping plaque reduction neutralisation test indicated the virus was a member of the epizootic haemorrhagic disease serogroup. Serotype specific plaque reduction neutralisation tests, indicated the virus was a member of the epizootic haemorrhagic disease serogroup not previously isolated in Australia. Analysis of the VP3 gene confirmed this observation. Cross neutralisation testing of the isolate with known epizootic haemorrhagic disease serotype viruses including endemic Australian and exotic strains identified isolate DPP2209 as epizootic haemorrhagic disease virus serotype 1.

Effect of Selected Insecticides for Thrips Control on Cotton in North Carolina, 1995

Abstract Granular insecticides were applied in-furrow at planting from a positive displacement device mounted above the planter on 25 May at the Upper Coastal Plain Research Station in Edgecombe County, NC. Liquid at-planting treatments were applied from a tractor at 3.5 mph with 20 gpa water through 8003 flat fan nozzles at 20 psi directed into the seed furrow. The foliar treatments were applied on 8 and 13 Jun via a CO2-pressurized sprayer calibrated to deliver 8.0 gpa at 50 psi with a single TX-8 Spray Systems nozzle 18 inches over the row. Plots were 4 rows X 50 ft, with 4 reps, arranged in a RCBD. The 11 treatments were evaluated for plant height, adult and immature thrips establishment, fruit load, percent opened bolls and yields. All data were subjected to ANOVA and DMRT. Plots were harvested with a 2-row John Deere mechanical picker from the middle 2 rows on 19 Oct.

Evaluation of In-Furrow Insecticides for Thrips Control on Cotton, 1994

Abstract Granular insecticides were applied in furrow at planting from a Gandy box mounted on the planter and the liquid insecticide applied with a CO2-powered flat fan nozzle oriented parallel and directly into the open furrow on 27 May at the Upper Coastal Plain Research Station in Edgecombe County, NC. Plots were 4 rows × 50 ft with 4 reps and arranged in a RCBD. The 6 products along with an untreated check were evaluated for effect on stand reduction, plant height, thrips establishment, boll load, bollworm-damaged bolls and yield. Thrips adults and immatures were collected on 26 May, 6 and 15 Jun, processed via the wash method and counted under a binocular dissecting microscope. Yields were take with a one row John Deere mechanical harvester from the middle 2 rows. Insect, plant and yield data were subjected to ANOVA and DMRT.

Paecilomyces Lilacinus, a Colonist of Aspergillus Flavus Sclerotia Buried in Soil in Illinois and Georgia

(1990). Paecilomyces Lilacinus, a Colonist of Aspergillus Flavus Sclerotia Buried in Soil in Illinois and Georgia. Mycologia: Vol. 82, No. 3, pp. 393-395.

A water balance model for rain-grown, lowland rice in northern Australia

A simple water balance model was developed for rain-grown, lowland rice on the heavy clay soils of the sub-coastal plain of the Adelaide River in northern Australia. The rice farming system is based on short duration (100 days) photoperiod-insensitive varieties. The seed bed is prepared in the flooded state with a tractor-driven rotary tiller. Aircraft are used to broadcast seed, fertilizer, and pesticides into the flooded fields. The crop is sown during mid-January to early February when rainfall and tillage criteria are satisfied. The model is based mainly on field measurements of evapotranspiration. Estimated dates of soil saturation and depths of ponded water at Coastal Plains Research Station agreed remarkably well with observed values in five wet seasons having widely different rainfall patterns. The model was used to estimate the success frequency of rain-grown, lowland rice at Darwin, Koolpinyah, and Humpty Doo with 93, 48, and 24 years of rainfall records respectively. A computer program was written to obtain daily estimates of soil water storage and depth of ponded water for each wet season from September 1 to May 31. In the program provision was made for maximum field pondage to be successively 6, 8, 10, and 12 inches. Rainfall was regarded as adequate providing there were (a) at least 14 days pondage ≥3 inches between December 31 and February 18 for wet tillage before sowing, (b) at least 80 days between sowing date and the last date at which ponded water was present on the field, (c) not more than 10 consecutive zero pondage days between 50 and 80 days after sowing, corresponding to the stage of panicle initiation through flowering. A 23-year comparison showed that on the average, the water availability was similar at the three stations, although differences sometimes occurred within individual seasons. The results indicate that the expectation of crop failure due to inadequate rainfall at Darwin is about 1 year in 30. In addition there is an expectation of major yield reduction of about 1 year in 10. The seasons of crop failure and low yield tended to occur in groups after relatively long runs of seasons of adequate rainfall. Designing for a maximum field pondage greater than 10 inches did not reduce the estimated number of crop failures at any station. The results are discussed in relation to practical farming operations.

Nitrogen response of IR8 rice at Coastal Plains Research Station in northern Australia

An initial evaluation of the yield potential of IR8 rice in northern Australia was carried out in the 1968 dry season, in the form of a nitrogen trial. The mechanically harvested grain yields (oven dry) varied from 1700 kg/ha with no nitrogen to a calculated maximum of 7335 kg/ha with a nitrogen application of 216 � 11.3 kg N/ha. The highest rate of application (269 kg N/ha) caused a small but significant reduction in mechanically harvested yields. Hand-harvested quadrat yields were closely related to machine-harvested yields (r = 0.90) ; they were some 20 per cent higher, and were not significantly reduced by the highest rate of nitrogen application. The yield response to nitrogen was mainly due to increased panicle numbers per unit area and secondarily to increased numbers of grains per panicle. Mean individual grain weight was only slightly, though significantly, affected by the treatments. The highest calculated yield was recorded with LA1 at flowering of 12.3 � 1.05. With an increase in LA1 to the highest value of 13.5 there was no significant decline in hand-harvested yield. Nitrogen uptake was linearly related to rates of nitrogen application throughout the range of treatments. Apparent nitrogen recovery was 103 per cent at flowering and 71 per cent at maturity in all treatments.