Criteria for the irreducibility of groups of linear homogeneous transformations

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Tomato Irrigation Scheduling for Optimum Production

The most common irrigation scheduling practice by Iowa vegetable growers is the imperfect soil moisture ‘feel’ method. Even during a growing season with normal rainfall,supplemental irrigation is necessary to avoid moisture stress, particularly during the blossom and fruit bulking period, which can result in lack of fruit set, reduced fruit size,sunburn fruit, and a lack of uniform ripening. The main questions are: when to turn on the irrigation system, and how long to run the pump

Tomato Response to Soil Application of Boron and Potassium

Fresh market tomato production has a high demand for potassium (K) and may be responsive to the micronutrient boron (B). An excellent Iowa yield of 1,000 cwt/acre will remove 240 lb of K20/acre in the fruit alone. Thus, growers apply high rates of K20 fertilizer to achieve top yields and quality. Iowa research and soil surveys over the years have shown no need for B additions for corn,soybean, and alfalfa production (Dr. Randy Killorn, personal communication). However, our vegetable K research trials have shown low B leaf levels early in the growing season, 27 to 42 ppm. Tomato leaf sufficiency ranges vary from 20 to 75 ppm, depending on the region where the research was conducted and the crop stage of growth at the time of sampling

Tomato Variety Observations

We continued our yearly evaluation of tomato varieties for commercial growers. Each year the major fruit problems are uniformity, consistent shape and size, ripening disorders, and vegetative plant size and foliage cover. Our objective was to examine early-, mid-, and main-season maturities. All were large fruited fresh market varieties

Polyethylene Mulches and Preplant Incorporated Herbicides for Tomato Production

Fresh market tomato production consists of selecting a well drained site, an early variety, a plastic mulch, a row cover, and transplanting in the spring as early as possible. This procedure can result in advanced maturity and top early marketable yields when prices are usually highest. Our previous research has shown wavelength selective plastic (SRM-olive or red) coupled with a row cover has given consistent top early yields.Clear plastic was also superior provided there was excellent weed control. Early production was highly correlated (r = 0.74) to maximum soil temperature at the 4-in. depth. Thus, clear plastic would be the mulch of choice

Sweet Corn Plastic Mulch Comparison

Early sweet corn production is enhanced by use of clear plastic mulch. Some growers use this practice on their earliest plantings to gain a market advantage and higher price. In cool, wet springs the practice is highly profitable. In central and northern Iowa, the years with a yield advantage more than offset the costs for years with no gain. There are many color plastic choices with various advertised benefits such as increased soil temperature and reflective radiation that speeds plant growth and development. The sweet corn research is designed to evaluate a few color mulches that are reported to affect corn growth and development—specifically, the sugar content of the kernel at harvest. The blue is supposed to enhance photosynthesis and improve translocation of carbohydrates (sucrose) to the developing kernel. As sweet corn is harvested in the immature stage (as opposed to field corn) it is thought there might be a sugar boost (some Canadian work was indecisive). The mulches were manufactured using pigment resins of a proprietary nature that change the wavelength of reflective radiation – blue and red. Thus, we measured the reflective radiation to see if that is true. Some plastics are included that affect soil temperature more than reflective radiation (i.e, the olive and clear). Increasing soil temperature and resultant enhanced shoot growth and leaf surface area may have more to do with photosynthesis and sugar production than specific reflective radiation

Callisto Residual Evaluation Sweet Corn HerbicideTrial

Callisto (mesotrione) is a new grass herbicide for use in sweet corn. It is labeled for both PRE and POST application. Excellent control of most broadleaves is obtained, with the exception of purslane and common ragweed. Its efficacy can be extended by tank mixing with Dual and/or AAtrex. In 2005 we applied alone, or in combination, Callisto, Dual II Magnum, and AAtrex 4L to Precious Gem sweet corn grown on a Clarion loam soil at the Horticulture Station, Gilbert, IA. The normal Callisto rate is 6 oz/acre PRE or no more than two 3 oz/acre applications as POST. Our highest POST application of Callisto was 12 oz/acre, 6 oz on June 22 and 6 oz on June 29, 2005. Injury to sweet corn, in form of bleaching of 10% of leaves, on July 7 was noted. Nonetheless, yields were high, averaging 1,931 dozen/acre

Sweet Corn Topping Evaluation

Sweet corn “topping” is the removal of plant parts above the ear after pollination has occurred. This practice has been reported to hasten maturity, improve picking ease, reduce bird damage, improve pesticide application to ears, and reduce lodging problems. Disadvantages of topping have included a reduction in earsize, poor kernel fill,sunburn of exposed ears, and additional production costs. The objective was to determine what effect topping would have on ear maturity, yield, and ear quality under Iowa growing conditions

Sweet Corn Herbicide Study

Weed control in sweet corn is very important since the competition they create reduces yield and quality factors such as ear size and tip fill. Weeds filling row centers can also interfere with pest control sprays and make harvesting more difficult. Herbicides are an important tool in weed management programs and in April 2005, the EPA registered the use of Callisto in sweet corn. To help growers utilize this new product effectively, we looked at different combinations and application timings of Callisto with the herbicides Dual II Magnum and AAtrex 4L for crop safety and weed control effectiveness

Sweet Corn ToppingTrial

Topping of sweet corn a few weeks before harvest is practiced in western Washington state and Nebraska to improve harvesting efficiency. Reports of east coast growers indicate topping may hasten earliness by 2 to 3 days, improve hand picking ease, reduce bird damage, and reduce wind lodging. Another potential advantage would be better spray coverage of the ear to prevent corn borer and earworm damage. Some drawbacks to the practice might include: reduction in earsize and flavor, malformed ears from lack of good pollination,sunburn of exposed ears(particularly late plantings), and additional costs. Generally, topping refers to removing the top of the corn plant just above the ear after pollen shed and pollination of the ear has occurred