Commercial production of bunched broccoli on the Eastern Shore of Virginia has been limited because of shortened internodes resulting in thick, tough stalks. A field study was completed to examine the influence of plant type (transplants or direct seeded), plant population (5800 or 8700 plants/ha), and N application (112 kg/N with zero, one, or two sidedress applications of 40 kg·ha–1) on marketable yield, head diameter, and stem diameter of `Packman' broccoli. None of the measured characteristics improved significantly with sidedress N application. Marketable yield and average head weight were significantly correlated (P = 0.01) to the total number of heads harvested (r = 0.70 and r = –0.91, respectively). More heads were harvested for the high population, direct-seeded treatment and fewer for the low-population transplants. Average stem diameter of transplants was slightly greater than that of direct-seeded broccoli being significant (P = 0.05) in the second and third harvests. However, few stems were of commercially acceptable diameter regardless of treatment combination. Additional evaluation of cultural management strategies and cultivar selection is needed to successfully promote commercial production of bunched broccoli in this growing area.
S.B. Sterrett and C.P. Savage Jr.
John Speese III and S.B. Sterrett
The effect of crop rotation was investigated on the efficacy and the economics of various insecticide strategies for Colorado potato beetle (CPB) control in potatoes (Solanum tuberosum L.) in 1995-96. These included broad-spectrum insecticides and biorational (environmentally friendly, naturally occurring) combinations that targeted specific CPB life stages. CPB pressure was greater in the nonrotated than the rotated plots. Although all materials gave better CPB control than the check, significantly more spray applications were required to reduce CPB numbers below treatment thresholds in the nonrotated plots than the rotated plots in both years. Overall yields and economic returns were significantly greater in the rotated plots in 1995. Efficacy of insecticide strategies varied, with little defoliation and few CPB larvae found in the imidacloprid treatment in 1995 and 1996. All insecticide strategies except endosulfan resulted in significantly higher estimated returns to management than the untreated check; the greatest returns occurred with permethrin and cryolite. No yields or returns could be obtained in 1996 due to excessive rainfall before harvest. These results indicate that yield and the cost of the insecticide strategy should be considered as well as insecticide efficacy in developing an effective integrated pest management program.
S.B. Sterrett and C.P. Savage Jr.
A procedure is described for maintaining root quality in a foundation seed program that serves a primarily processing industry. Trueness-to-cultivar root type and color is maintained through hill selections within the prefoundation seed at harvest. Internal color is examined after sprout production, but prior to planting. Each root of the prefoundation seed is lifted and cut. If any sectorial chimeras are visible or the internal color is lighter than expected for that cultivar, all sprouts from that root are discarded. Otherwise, sprouts are planted to generate prefoundation seed. Prefoundation roots not selected by hill selection are given to designated growers for production of foundation seed. Contracts with growers for foundation seed and seed distribution are the responsibility of the Virginia Crop Improvement Assn. (P.O. Box 78, Mt. Holly, VA 22524). Hill selection of `Hayman', a white-skinned, white-fleshed cultivar, over the past 20 years has essentially eliminated strings and nonenlarged roots. Improved root shape and smoothness has resulted in increased regional consumer demand for this specialty crop.
S.B. Sterrett, B.B. Ross and C.P. Savage Jr.
New Jersey `Syn 4' asparagus (Asparagus officinalis, L.) was grown on a sandy loam soil to compare plant survival and yield of asparagus grown from crowns and transplants under four irrigation treatments: sprinkler (SPR), surface trickle (ST), subsurface trickle (SST), and no irrigation (NI). While plant survival of crowns was not appreciably influenced by any irrigation treatment, survival of transplants was significantly increased by SST. Total and marketable yields from crowns and transplants were similar in the first harvest season (year 3). However, in years 4 and 5, the yield of crowns was higher than that of transplants. Subsurface trickle increased yield from transplants in years 4 and 5 and increased yield from crowns in year 5. All irrigation methods significantly increased both spear production (spear/ha) and average spear weight. Subsurface trickle irrigation resulted in the largest increase over NI in total yield and spear production.
S.B. Sterrett, M.R. Henningre and G.S. Lee
The progression of internal heat necrosis (IHN) of `Atlantic' potato was studied in seven plantings in two locations (Virginia and New Jersey) over 3 years. The incidence (percentage of tubers with necrosis), severity (rating), and distribution (percentage of 1/8 pieces with necrosis per tuber) of IHN increased with successive harvests, but varied with year and location. Significant but weak linear correlation coefficients were found for the IHN variables of incidence, rating, and distribution with either time in days after planting (DAP), yield, or percentage of tubers >64 mm in diameter. Models were developed using stepwise regression to relate IHN variables with DAP, yield, percentage of large tubers, and various temperature and rainfall measurements. Time (DAP), penalty (DAP to first occurrence of three consecutive days of negative accumulated heat units), and rainfall (1 to 60 DAP) were significant variables in regression models for incidence and rating. While DAP and penalty were significant variables in the regression model for distribution, the variable rainfall was not included in the model. These findings indicate that the potential of IHN in `Atlantic' varies with the growing season, and is influenced by more than one environmental
S.B. Sterrett, K.G. Haynes and C.P. Savage Jr.
Sixteen broccoli (Brassica oleareacea var. italica) cultivars were evaluated for yield, head maturity, and quality attributes in the fall of 1997. `Liberty', `Sabre', `Barbados', and `XPH12211' were dropped after 1997 because of poor yield, coarse stems with severely shortened internodes, or lack of seed availability. Thus, three new cultivars, `Nomad', `Sussex', and `XPH12212', were included in the 1998 trial. Head yield was generally higher in 1998 than in the cooler and drier 1997. In each year, cultivars were ranked into early and main season based on yield over sequential harvest dates. Only `Windsor' was rated as a main-season cultivar in 1997, but an early-season cultivar in 1998. Cluster analyses were then used to group cultivars within year and season by head quality attributes. Based upon these analyses, `Captain' is recommended for early production because of favorable head quality and moderately high yield potential. After 2 years of tests, none of the main-season cultivars could be recommended. `Arcadia', `Decathlon', and `Windsor' were either too late or inconsistent in maturity. Yield was low for `Excelsior' and `Arcadia'. Head quality of `Laguna' and `XPH12212' was poor or inconsistent. In the 1998 trial, `Nomad' and `Sussex' warranted additional evaluation because of improved yield, head and stem diameter and head quality.
S. B. Sterrett, C. P. Savage Jr. and K. M. McManus
Studies were conducted in 1988 and 1989 to evaluate the influence of planting time and method on plant establishment and yield of fall broccoli. In 1988, plant establishment of direct-seeded broccoli was not improved with application of vermiculite (63 kg/ha). a cross-linked polyacrylamide polymer (17 kg/ha), or both as anti-crustants over the untreated check (37.6%, 32.2%, 24.6%, and 31% of target population, respectively). In 1989, transplants were compared with double-seeding (planting two seeds 25 mm apart). With seed. germination of 55% in the early planting (8 Aug.). plant populations of double-seeding and transplants were similar, but 42% germination of double-seeding in the late planting (28 Aug.) resulted in lower plant populations than from transplants. While yield reflected differences in plant populations, the percentage of marketable heads from transplants was significantly greater (90.6%) than from seedlings (78.9%). These data suggest that broccoli transplants are a viable option when high soil temperatures may be detrimental to seed germination.
S. B. Sterrett, D. V. Midkiff and C. P. Savage Jr.
The influence of nitrogen source (commercial vs two slow-release sources), nitrogen rate at planting (56 vs 112 kg/ha) and nitrogen sidedress at early bloom (0, 56 lb N) on potato yield and soil nitrate concentrations was examined in a 3 year field study on a Bojac sandy loam soil. In each year significantly lower yields were recorded for one of the slow-release forms of N, but not the same source each year. Increased N applied at planting increased yield in 1992 and 1993, while sidedress N increased yield only in 1992. Soil nitrate concentrations in 1991 were substantially higher throughout the growing season than in 1992, particularly in the O-23 cm (surface) layer. Sidedressed nitrogen significantly increased soil nitrate concentration at 0-23, 23-46, and 46-99 cm depths, with the greatest increases recorded in 1991. The rain-fall during the growing season in 1991 was 23.5 cm, while in 1992 and 1993 rainfall was 38 and 31 cm, respectively. This study suggests that late N applications can contribute to nitrate movement through the soil profile without consistently improving tuber yield.
S.B. Sterrett, H.E. Hohlt and C.P. Savage Jr.
Off-site movement of sediment, nutrient and agricultural chemicals from plasticulture production of green-pack tomatoes on water quality is a serious environmental concern, particularly for the clam aquaculture industry of eastern Virginia. Thus, the development of ecologically sound, economically sustainable cultural management strategies for tomato (Lycopersicon esculentum Mill.) production is needed. Two plantings were made within each of the three tomato harvest seasons [summer, bridge (late summer) and fall] in 1998 and 1999 (one summer crop in 1999). Between-bed treatments included clean culture or pearl millet [Pennisetum glaucum(L.) R. Br.] sown at bed establishment. On-bed treatments included standard plasticulture with fumigation on a 76-cm-wide bed (std), plasticulture without fumigation on a 76-cm-wide bed (std-fum), plasticulture on a 61-cmbed with fumigation (narrow) and organic mulch [wheat straw (Triticum aestivum L.) in 1998; desiccated hairy vetch (Vicia villosa Roth.) in 1999]. Total and marketable yields for the three plasticulture on-bed treatments (std, std-fum and narrow) were similar in 1998 and 1999. Yield was suppressed for the organic mulch on-bed treatments in all but the bridge plantings in 1999. Improved yield with plasticulture treatments and high market price for the summer crop in 1998 resulted in elevated crop value and return to land and management (return) compared to that of organic mulch. The return for later plantings was low, but positive. Return was negative for both bridge and the first fall crops in organic mulch in 1998. Low yields in all treatments and low prices in 1999 resulted in negative to negligible return for on-bed treatments in all but the summer planting using plasticulture. Return was consistently lower with organic mulch compared to plasticulture for the high value summer crop in Virginia with between-bed millet in 1998 and with or without millet in 1999. The use of organic mulch on the beds in this study was not economically feasible for the high value summer crops. Adjustments (desiccation of cover, control of weeds) in cultural management of the between-bed management strategy are needed before large-scale commercial implementation will occur.
S.B. Sterrett, C.P. Savage Jr. and H.E. Hohlt
Tomatoes (Lycopersicon esculentum Mill.) were grown under plastic culture on a Bojac sandy loam soil in 1991, 1992, and 1994 to determine influence of nitrogen rate at planting and water application scheduling by pan evaporation (PAN) on crop yield and fruit size. Marketable yield and percentage of large fruit was significantly increased in 1991, 1992, and 1994 as irrigation application increased from 0.5 to 1.0 or 1.5 PAN (one application per day). Nitrogen applications exceeding 168 kg–ha–1 resulted in lower yield and reduced fruit size in 1992. In 1994 (late planting followed by hot, dry growing season), yield was increased with increasing N to 213 kg–ha–1 with 1.0 PAN, but not influenced by N at 1.5 PAN. Residual soil nitrate concentration was increased with reduced irrigation or increased nitrogen application. Nutrient management plans to address non-point source pollution concerns of EPA will need to reflect crop irrigation needs to maintain yield and fruit size while minimizing nitrate accumulation within the soil profile.