Planting Dates and Rate of Nitrogen on Cauliflower

The varieties Armado April and Armado Quick (Elsoms, Ltd.) were seeded in 2-inch pots in the greenhouse on August 1, August 16, and August 30, 1978, and were transplanted to the field on August 21, September 12, and September 26, respectively. Plots consisted of two 25-foot rows. Treatments were 1) 50 pounds N/acre as ammonium nitrate applied on December 22, 1978, and again on February 26, 1979, and 2) 100 pounds N on the same dates. Treatments were in randomized block design. Heads were harvested twice weekly from April 13 until May 9, 1979.

Table 2 presents the main effects of variety, transplant date, and nitrogen rate on yield, head size, and winterkill of cauliflower. Only main effects are presented since there were no significant 2-way or 3-way interactions among varieties, dates, or N rates.

Mean head weight decreased with later transplant dates and increased with the higher N rate. Armado April produced larger heads than did Armado Quick. Since the number of plants surviving the winter was lowest for the first planting date, part of the increased head weight for this planting could be caused by reduced competition between plants. However, the extra three weeks for plant growth probably accounted for most of the increase.

Planting date had little effect on timing of curd production. Peak maturity differed by no more than one week with more than a month difference in transplant dates.

Total yield on an area basis did not vary significantly with planting date because of greater winterkill of the earliest planting. The higher rate of N increased total yield and, in contrast to 1978, Armado April outyielded Armado Quick.

Winterkill was not affected by variety or by the winter-applied nitrogen. The larger plants from the earliest planting were most susceptible to winterkill. The winter of 1978-79 was colder than average. The plants were subjected to several days of minimum temperatures below 20°F and one night of 13°F in January, 1979. Plants appeared to be most susceptible after onset of curd formation. The greater incidence of early curd formation in the first planting may explain the greater winterkill.

Observations of the variety Ferry Morse April were made on several off-station locations with grower cooperators. In a field 4 miles southwest of the Station and transplanted on October 1, winterkill was approximately 25% with a minimum recorded temperature of 9°F. Yield was excellent but quality was poor because of poor cover of the curd.

In a second field 12 miles south of the Station, also transplanted on October 1, winterkill averaged 80% with a low temperature near 0°F. An interesting pattern of plant survival was noted. Where the transplanter press wheel made an extra deep furrow, survival was about 60%. Survival of more exposed plants was close to zero.

In a third field 30 miles northeast of the Station in an area where overwinter cauliflower has been grown for decades, the winterkill was nearly 70% with a low temperature of 15°F. This exposed hillside location appeared to suffer more wind and ice storm damage than did the valley floor sites.


Table 2. Effects of transplant date, variety, and N rate on overwinter cauliflower, 1979                     Mean head wt.   Gross yield   Winterkill   Harvest span  Treatment             (pounds)      (tons/acre)      (%)                                  Transplant date  8/21                    1.3            6.8            24      4/14 - 4/25  9/12                    1.1            7.2             6      4/17 - 4/27  9/26                    1.0            6.6            11      4/19 - 5/05             LSD (0.05)   0.2             NSZ           11  Variety  Armado Apri             l.3            7.8            22      4/18 - 4/31  Armado Quick            1.0            5.9            19      4/15 - 4/28             LSD(0.05)    0.2            1.5            NS                   Sidedressed N rate  100 pounds              1.07           6.3            12      4/16 - 4/29  200 pounds              1.21           7.5            15      4/16 - 4/30                            *             *             NS                                  ZNS, *: no significant difference, differences significant at 5% level, respectively.