VEGETABLE CULTIVAR AND CULTURAL TRIALS

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1 VEGETABLE CULTIVAR AND CULTURAL TRIALS 27 PREPARED BY: D. WATERER W. HRYCAN FUNDED BY: AGRICULTURE DEVELOPMENT FUND Department of Plant Sciences University of Saskatchewan, 51 Campus Drive Saskatoon, Saskatchewan, Canada, S7N 5A8 Telephone: (36) Fax: (36)

2 Evaluation of Colored Mulches Use of plastic soil mulches has been shown to accelerate the development, improve yields and enhance the quality of various vegetable crops. Black mulch is most widely employed as it provides excellent weed control while also conserving soil moisture. Clear and wavelength selective types of mulches that increase soil temperatures may be beneficial in situations where growers are attempting to grow warm season vegetable crops in locations with a short and cool growing season. Conversely, white or reflective silver mulches tend to keep the soil cooler than normal which may be beneficial for cold adapted crops. Some research suggests that the light spectrum reflected back from colored mulches (red, blue or yellow) may alter growth and potentially enhance crop yields, while also repelling certain insect pests. Previous research by the University of Saskatchewan had shown some inconsistent effects of mulch color on yields. See: This trial evaluated the growth and yields of several vegetable crops on mulches of various colors. The trial was conducted in 27 at the University of Saskatchewan Horticulture Field Research Facility in Saskatoon. The heavy clay soil at the test site was prepared by rotovating 1 week prior to laying the mulch. The mulches tested were red, white, blue and yellow. The test crops were corn (cv. Fantastic), Spanish onion (cv. Vision), cucumbers (cv. Fanfare and Morden Early) and zucchini (cv. Goldrush). The cultivars selected have performed well in previous trials. The corn, cucumbers and zucchini were direct seeded by hand through the mulch on May 31. The corn was seeded in twin rows, with 15 cm between seedlings within the row. The zucchini were seeded one meter apart, while the cucumbers were seeded 3 cm apart. Eight week old onion seedlings were transplanted into the various mulch treatments on June 6. Two rows of onions were planted, with 15 cm between plants within each row. Six week old pepper seedlings and 3 week old cantaloupe seedlings were transplanted in to the various mulch treatments on June 6. The peppers were spaced in twin rows 3 cm apart, with 3 between plants within each row, while the melons were planted 3 cm apart in a single row. The peppers and melons were kept covered with low tunnels (Reemay for peppers, perforated polyethylene for the melons) until flowering in early July. The crops were drip irrigated. No herbicides were applied; weed escapes were controlled by hand weeding. No pest or disease problems were observed. The zucchini and cucumbers were harvested twice weekly. The fruit were graded according to size and freedom from defect. The corn was harvested weekly. Harvest continued until the first killing frost in mid-september, at which time all immature fruit were also harvested. The onions were taken in a once over harvest on Sept 11. Thermocouples were used to monitor soil temperatures at depths of 5 cm in all mulch treatments. 6

3 Results In June, all of the mulch treatments reduced soil temperatures relative to the non-mulched control - with the white and yellow mulch treatments resulting in the coolest temperatures. In July, the red and blue mulch treatments were warmer than bare ground, while the white and yellow were again cooler than the control. In August and September temperatures under all mulch treatments were higher than the bare ground. Weeds were a significant problem in both directly under the mulch and in the planting holes of the red and blue mulch treatments. By comparison, weed growth was minimal under the plastic and in the planting holes in the white and yellow mulch treatments. We could not determine the cause of this difference in weed pressure. Table 1. Mean monthly soil temperatures (oc) under various colors of soil mulch (27). June July August September Average No mulch Red Blue White Yellow The corn developed more quickly on the blue mulch than on the other colors, however, the blue mulch also produced the lowest cob yields. None of the mulch colors tested improved yields of corn relative to a non-mulched control. All of the mulch treatments produced greater marketable yields of zucchini than the nonmulched control. Differences between marketable yields for the various mulch colors were relatively minor. The yellow and white mulches produced more oversize fruit than the other treatments - a portion of this fruit would have been marketable if the crop had been harvested more frequently. Stand establishment for the onions in the red mulch (63%) and the blue mulch (65%) was less successful than in the yellow or white mulches, which both produced a full stand. Heavy weed pressure in the red and blue mulch treatments may have contributed to the stand establishment problems. The onions harvested from the red mulch were smaller, on average, than the other treatments. A near perfect stand coupled with the largest average bulb size resulted in the white mulch producing the highest overall yield. For both cultivars of cucumber, the white and yellow mulch colors produced substantially higher yields than the other mulch treatments. Mulch color had little impact on the size distribution of the fruit - the observed differences in yield instead largely reflect differences in numbers of fruit set. 7

4 Corn 6 Zucchini 2 5 Culls Marketable Oversize Cobs/m row 15 Fruit/m row No mulch No mulch Onion Morden Early Cucumber Bulb wt (kg) Large size Medium size Fruit wt (kg/plot) Large size Medium size Small size Fruit wt (kg/plot) Fanfare Cucumber X Large Large Medium Small 8

5 Conclusion The effects of the different colors of mulch on soil temperatures and crop growth were variable and often ran contrary to expectations. There were few differences between colors in the corn and zucchini crops. In both the onions and cucumbers, the white and yellow mulch treatments clearly enhanced yields relative to blue or red mulch. The yellow and white mulches appeared to cool the soil, at least early in the growing season and also provided an enhanced degree of weed control. These mulch effects could be expected to be of benefit to a slow growing, cold adapted crop like onions. However, cucumbers typically respond positively to mulch treatments that warm the soil and because of their sprawling growth habit have few problems with weed competition. Colored mulches are substantially more expensive than standard types (black, clear and wavelength selective). It is doubtful whether the limited and inconsistent benefits obtained from using the colored mulches would be sufficient to offset their higher cost 9