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James E. Ells and Ann E. McSay

Growth chamber tests demonstrated that alfalfa (Medicago sativa L.) residue is toxic to cucumber (Cucumis sativus L.) seed germination and seedling growth. Ground alfalfa roots at 0.5% (w/w, dry weight) inhibited germination when added to the growing medium. Alfalfa roots at 0.5% were also toxic to pregerminated cucumber seed. However, cucumber seedlings grew normally if this same medium was watered and incubated for >1 day before planting. Alfalfa particle size in media influenced cucumber performance, with the intermediate size (1 to 2 mm) being lethal to cucumbers.

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James E. Ells, Ann E. McSay and E.G. Kruse

Irrigation scheduling programs were developed for cabbage and zucchini squash that produced high yield and water-use efficiency with a minimum number of irrigations. The irrigation programs are based on a soil water balance model developed by the USDA. The procedure involved selecting irrigation programs developed for similar crops and using them as standards for cabbage and zucchini for three growing seasons. The treatments involved irrigation levels higher and lower than the standard. After the third year, the best treatment for each year was selected. Coefficients for the standard model then were adjusted by trial and error to produce a program that called for the same number of irrigations and the same amount of water as the best-performing treatment when using the same weather data. These revised programs for cabbage and zucchini squash are available on computer disks and may be used on any IBM compatible PC provided wind, temperature, solar radiation, humidity, and precipitation data are available,

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E. Gordon Kruse, James E. Ells and Ann E. McSay

A 3-year irrigation scheduling study on carrots (Daucus carota L.) was conducted at the Colorado State Univ. Horticulture Research Center near Fort Collins to determine the irrigation schedule that produced the best combination of high water use efficiency and marketable yields with the least amount of water and fewest irrigations. This study used an irrigation scheduling program developed by the U.S. Department of Agriculture/Agricultural Research Service with crop coefficients calculated for carrots. Maximum carrot production and water use efficiency were obtained when the scheduling program simulated a 30-cm rooting depth at planting, increasing linearly to 60 cm in 75 days. Best yields and water use efficiency were attained by irrigating whenever 40% of the available water in the root zone had been depleted. The computer program for irrigation scheduling is available on diskette from the authors.

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James E. Ells, E. Gordon Kruse and Ann E. McSay

An irrigation scheduling program has been developed for zucchini squash that produced high yields and high water use efficiency with, a minimum number of irrigations. The irrigation program is based upon a soil water balance model developed by the USDA. This irrigation program is available in diskette form and may be used with any IBM compatible personal computer provided wind run, temperature, solar radiation, humidity and precipitation data are available.

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James E. Ells, E. Gordon Kruse and Ann E. McSay

Roots of acorn squash were washed from soil cores, dried and weighed. The cores were taken in a pattern about individual plants to reflect the roots present in each selected zone at different periods during the season. A different plant was sampled at each period so that there would be no effect from previous sampling. The root weights were multiplied by factors commensurate with the volume of soil represented by each core sample. Two years data have indicated that irrigation level effects the size of the root system but not its distribution. Density of roots was always greatest in the top 15 cm of soil and this zone of the greatest density progressively moved out from the center of the plant with time. Pattern of root distribution was not effected by plastic mulch, bare ground, trickle or furrow irrigation treatments. Root distribution was the same on all sides of the plant.

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James E. Ells, Ann E. MeSay and Stephen M. Workman

Chopped alfalfa (Medicago sativa L.), alfalfa hay extract, and ammonium hydroxide produced free ammonia in media and inhibited both germination and seedling growth of cucumber (Cucumis sativus L.). Toxic levels of ammonia were not produced by the quantities of manure added to the media. Alfalfa extract enhanced cucumber seedling growth in sand medium while inhibiting growth in sand-soil media. This difference is attributed to a reduced level of microbial activity in the sand. With higher levels of microbial activity, rapid decomposition of the extract may have resulted in a burst of ammonia evolution that proved damaging to cucumbers. The natural buffering capacity of the soil medium apparently mitigated the effects of the ammonia. Ammonium hydroxide, which did not depend on microbiological activity to release ammonia, proved lethal to cucumbers grown in sand. A diminished effect on growth was observed as the cation exchange capacity of the medium increased. Because high levels of alfalfa hay and ammonium hydroxide were required to produce toxic levels of ammonia in soil, it is unlikely that cucumbers would be harmed under normal field usage of alfalfa hay.

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Tim D. Davis, James E. Ells and Ronald H. Walser

Seeds of Lycopersicon esculentum Mill. cv. UC 82L were treated with hypertonic priming solutions containing KNO3 and K3PO4(10 g·liter-1 each), and various concentrations of uniconazole before sowing. Treatment of the seed with priming solution only hastened emergence by ≈ 2 days compared to untreated seed sown directly from the packet, but did not affect total emergence after 12 days. Addition of uniconazole to the priming solution had no significant effect on speed of emergence or total emergence after 12 days compared to the primed control. Seed priming plus uniconazole at 1 or 10 mg·liter-1 reduced seedling height after 2 weeks by ≈ 20% compared to the primed control. Uniconazole had no effect on the mortality of either hardened or nonhardened seedlings exposed to below-freezing temperatures for 3 hr. These data suggest that treatment of tomato seed with hypertonic solutions containing uniconazole would be of little practical value in protecting seedlings from freeze damage. Chemical names used: (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-yl)penten-3-ol (uniconazole).

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James E. Ells, Ann E. McSay, E. Gordon Kruse and Gregory Larson

Squash (Cucurbita pepo L. var. pepo) plants were grown on black polyethylene mulch or on bare ground, with trickle or furrow irrigation, and received only natural rainfall, or natural rainfall plus half or all of the estimated supplemental irrigation water required as determined by an irrigation scheduling program. The squash roots predominate in the upper 6 inches of soil throughout the season, with no less than 60% of the root mass located in this layer. The proliferation of roots increased as they extended horizontally from the vertical center line of the plant from 0 to 24 inches. Neither the irrigation treatments nor black polyethylene mulch had any influence on the pattern of root development. Water stress, however, reduced the size of the root system and the crop yield. Yields were not influenced by either furrow or trickle irrigation on the short rows that were used in this study. However, black polyethylene mulch and full irrigation offered the best chance of maximizing squash yields under the conditions of this study.