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Darlene Wilcox-Lee

There are approximately 17,000 acres of fresh market vegetables and potatoes being produced on Long Island where irrigation is a routine agricultural production practice. Irrigation water is obtained from individual wells which pump water from an extensive underground aquifer. Although the quantity of water available for irrigation is not limited at present and will not be in the foreseeable future, the combination of agricultural practices, sandy soils and low soil pH's have had an impact on water quality. Certain pesticides move easily through the porous Long Island soils and are not quickly broken down at the naturally low pH levels of these soils. The use of Temik (aldicarb) for potato production resulted in ground water contamination with this chemical and spurred action by horticultural researchers and county and state agencies to define the scope of, and provide a potential solution for, contamination of Long Islands ground water. Thus, considerable effort has been expended on research and implementation programs to prevent ground water contamination with agricultural chemicals. Much of this effort has involved attempts to alter cultural practices, such as irrigation and pesticide application methods in order to decrease the potential for leaching of contaminants into the ground water. In addition, alternate crops have been considered which may require less irrigation and fewer pesticides than those traditionally grown. Specific research projects and government agency policies pertaining to agricultural water usage on Long Island will be discussed.

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Dan Drost and Darlene Wilcox-Lee

Asparagus officinalis L. cv. Centennial established with seedling transplants in 1983 was maintained with a conventional tillage (CT) or a no-till) (NT) system with either metribuzin or metribuzin + napropamide being applied for weed control. Marketable yield was assessed from 1985-1989. In 1989, in addition to yield data, destructive harvests were made every three weeks from March to November to evaluate the effects of tillage on fern, crown and bud growth and root carbohydrate levels. Yields were reduced in CT when compared to NT during all years. Asparagus growth (crown and fern weight, bud cluster, bud and fern numbers) was greater in NT than CT throughout the year although seasonal patterns of growth were similar for both tillage systems. Root carbohydrate levels were higher in NT than CT before the harvest season began. Carbohydrates for both tillage systems reached their lowest level in late July before recovering to pre-harvest levels in late September. Use of metribuzin + napropamide did not reduce fern number or yield but significantly reduced the number of bud clusters, buds and fern when compared to metribuzin alone.

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Daniel Drost and Darlene Wilcox-Lee

Asparagus is considered a relatively drought tolerant plant, but few studies are available on the gas exchange response to soil moisture stress. Seedlings were grown in the greenhouse for six months before initiation of the water stress treatments. Soils were allowed to dry to matric potentials of -0.05, -0.3 and -0.5 MPa before rewatering to pot capacity. Gas exchange and fern water potentials were measured diurnally on asparagus plants when soil matric potentials reached their minima. Decreasing soil matric potentials decreased net carbon dioxide assimilation, stomatal conductance and fern water potential. Assimilation rates (6 am) were between 3 and 5 umols m-2 s-1 for all soil moisture treatments. Carbon assimilation rates of 10, 8, and 7 umols m-2 s-1 were recorded at 10 am for the -0.05, -0.3 and -0.5 MPa soil matric potentials, respectively. Assimilation rates decreased sharply over the remainder of the day. The diurnal pattern for conductance were similar to the assimilation rates. Fern water potentials were greater in the -0.05 MPa than in the -0.5 MPa treatment for all measurement periods with an intermediate response for soil matric potentials of -0.3 MPa. Fern water potentials were highest at 6 am (-0.2 to -0.6 MPa) before declining to their minima (-1.5 to -1.8 MPa) at 10 am. Water potentials remained at these low levels throughout the day before recovering slightly at 6 pm.

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Daniel Drost and Darlene Wilcox-Lee

Asparagus is considered a relatively drought tolerant plant, but few studies are available on the gas exchange response to soil moisture stress. Seedlings were grown in the greenhouse for six months before initiation of the water stress treatments. Soils were allowed to dry to matric potentials of -0.05, -0.3 and -0.5 MPa before rewatering to pot capacity. Gas exchange and fern water potentials were measured diurnally on asparagus plants when soil matric potentials reached their minima. Decreasing soil matric potentials decreased net carbon dioxide assimilation, stomatal conductance and fern water potential. Assimilation rates (6 am) were between 3 and 5 umols m-2 s-1 for all soil moisture treatments. Carbon assimilation rates of 10, 8, and 7 umols m-2 s-1 were recorded at 10 am for the -0.05, -0.3 and -0.5 MPa soil matric potentials, respectively. Assimilation rates decreased sharply over the remainder of the day. The diurnal pattern for conductance were similar to the assimilation rates. Fern water potentials were greater in the -0.05 MPa than in the -0.5 MPa treatment for all measurement periods with an intermediate response for soil matric potentials of -0.3 MPa. Fern water potentials were highest at 6 am (-0.2 to -0.6 MPa) before declining to their minima (-1.5 to -1.8 MPa) at 10 am. Water potentials remained at these low levels throughout the day before recovering slightly at 6 pm.

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Darlene Wilcox-Lee and Daniel T. Drost

Crowns and tranplants of `Martha Washington' (MW) and `Jersey Prince' (JP) asparagus were planted in 1985. Plots were harvested for 0,2,4 weeks (traditional schedule); 1,2,6 weeks (moderate harvest pressure); or 2,4,8 weeks (severe harvest pressure) in 1986, 1987, and 1988, respectively. All plots were harvested for 8 weeks after 1988. An AOV was performed to test the main effects of cv, planting technique and harvest schedules and interactions on early and total season yield of large, medium-sized and total spears. MW produced a significantly higher yield of both early and total season large spears than JP in all years. Total yields did not differ between cvs. There was no significant effect of planting technique on yield in any year. Harvest schedules imposed in the first 3 years had significant long term effects on yield. Although severe harvest pressure produced larger yields than the other schedules in 1986-1988, from 1989-1991 yields were lowest in the severe harvest pressure plots. The traditional harvest schedule produced similar yields to the moderate pressure schedule. There were no consistent interactions between cultivar, planting technique and harvest schedule These data indicate that a slightly more aggressive harvest schedule in the early years of an asparagus planting would not have long term deterimental effect on yield. However, severe cutting pressure can reduce yields compared to traditional cutting schedules for at least 3 years after initial harvest pressure treatment

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Daniel Drost, Darlene Wilcox-Lee, and Richard Zobel

Published data on the spatial patterns and periodicity of root growth in asparagus are limited. During the 1989 growing season growth and distribution of both fleshy and fibrous roots were monitored in a 7 year old asparagus planting. Soil cores were removed at 15 cm intervals to a depth of 90 cm at 40 and 80 cm from the plants in asparagus beds which had been maintained under conventional (CT) and no-till (NT) production systems. Fleshy and fine roots were separated from the soil and root length densities calculated. Harvests began in late March and continued at three week intervals until early November. Fine root growth was greater in the NT than CT in all depths and at both locations in March. Greatest lengths of fine roots were at the 15-60 cm depths for both CT and NT. This pattern was consistent throughout the season. Fine root lengths decreased by one half by the middle of the year (July) and remained at those levels until the last harvest (Nov). Fleshy root lengths were more variable, however NT generally had greater lengths than CT. Greatest length of fleshy roots were located in the 15-60 cm depths for both CT and NT treatments. Few fleshy roots were found below the 60 cm depth.

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Darlene Wilcox-Lee and Daniel T. Drost

Seedlings of the asparagus cvs Mary Washington (MW) and Syn 4-56 (4-56) were grown at minimum soil matric potentials (SMP) of -0.05, -0.10, and -0.30, -0.50 or -1.5 MPa. Decreases in shoot dry weight leaf area, storage and fibrous root dry weights, and total root and plant dry weight were an exponential function of soil moisture in both cvs. Most of the growth inhibition occurred between the -0.05 and the -0.30 MPa levels of soil moisture, with little further response to SMP drier than -0.30 MPa. Consistent differences between the two cvs, regardless of SMP were apparent in leaf area, shoot dry weight, storage and fibrous root dry weights and root/shoot ratios. MW produced greater leaf area and shoot dry weights than did 4-56 at high SMP and exhibited greater inhibition of shoot dry weight by low SMP than did 4-56. Conversely, 4-56 produced greater storage root dry weight than MW at all SMP., although in mature field-grown plants, 4-56 produced greater fern weight, crown weight and number and stem numbers than MW. Root/shoot ratios generally increased with decreasing SMP. However, the root/shoot ratio of 4-56 was greater than that of MW over the entire range of soil moisture and increased more with decreasing SMP than did MW. Stomatal conductance (gs), fern xylem potential (), and net C02 assimilation rates decreased with decreasing SMP in a similar manner in both cvs. were

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Darlene Wilcox-Lee and Daniel T. Drost

Asparagus officinalis L. cv. Centennial established with transplants in 1983 was maintained with tillage or a no-till (NT) system to evaluate effects of tillage on yield and plant growth in a mature asparagus planting. Metribuzin or metribuzin + napropamide at 1.12 and 1.68 kg a.i./ha, respectively, were used for weed control in both tillage regimes. Marketable yields were assessed for 5 years. In 1989, in addition to yield data, destructive harvests of entire plants were made every 3 weeks from March to November to evaluate the effect of tillage on fern, crown, and bud growth, and carbohydrate status. Yields were reduced by tillage from 12% to 50% from 1985 to 1989. There were no herbicide effects nor was there an effect on yield due to an interaction between herbicides and tillage. All indices of growth measured for NT exceeded those in tilled plots, although seasonal patterns of growth were similar in both. Crown and fern weight, bud cluster, and bud and fern counts were higher by 178%, 175%, 152%, 161%, and 195%, respectively, in NT than in tilled plots. The metribuzin + napropamide combination did not reduce fern fresh weight or yield, but significantly reduced the number of bud clusters, buds, and ferns when compared to metribuzin alone. Chemical names used: 4-amino-(1,1-dimethylethyl)-3-(methylthio)-l (metribuzin); 2,4-triazin-5(4H) -one, N,N-diethyl-2-(naphthalenyloxy)-propanamide (napropamide).