Overwintered cauliflower can now be considered a crop of proven potential in the Willamette Valley. Trials at the North Willamette Station and by growers have usually given acceptable yields and quality. However, yields of early varieties, and particularly in cold springs, have occasionally been disappointing. Since plant nutrient uptake is limited on cold soils, these low yields may have been caused by inadequate availability of P or other elements. Past recommendations for overwintered cauliflower have called only for application of N in the spring. The effects of spring-applied P and the form of spring-applied N on cauliflower yield and quality have not been investigated. Likewise, the response of overwintered cauliflower to lime, which increases P availability, has not been studied. The purpose of these trials was to investigate the effects of lime, spring applied P, and source and rate of N on the yield and grade of overwinter cauliflower.
Methods
1983.
Agricultural limestone (95% CaCO3 equivalent) at 0, 2, 4, and 6 tons/acre was applied in 1979 to 2,300 square foot plots of Willamette silt loam with four replications of each treatment in randomized block design. Resulting soil pH in August 1982 averaged 5.5, 6.0, 6.2, and 6.6, respectively. After a broadcast, incorporated application of 0.75 pounds/acre trifluralin, 2.0 pounds/acre fonofos, and 700 pounds/acre of 10-20-20, 'Arminda' cauliflower was direct-seeded on approximately 3 feet x 4 inches spacing on August 4, 1982. Sprinkler irrigation was applied as necessary for stand establishment. In late September, the stand was thinned to 18 inches in the row. Diazinon (1 pounds/acre) was applied as a soil drench on August 30 and again on October 4. After a mechanical cultivation, napropamide was applied at 2.0 pounds/acre.
On February 15, 1983, the lime main plots were split into 5 subplots (2 rows x 24 inches) by band application of the following: 1) ammonium nitrate at 50 pounds N/acre, 2) urea at 50 pounds N/acre, 3) ammonium nitrate as above plus 100 pounds 0-45-0/A, 4) urea as above plus 0-45-0 as above, 5) no spring-applied fertilizer. Treatments 1-4 also received a band treatment of 30 pounds N/acre as ammonium sulfate. The ammonium nitrate and urea applications were repeated on March 25.
Leaf samples for plant tissue analysis were collected from plots receiving 0 and 4 tons lime/acre and all subplot treatments on March 24. The first harvest occurred on April 8, 1983, with additional harvests on April 15 and April 22. Heads were graded into #1 (free of any defect) and #2 (off color, mildew, slug damage, leaves or bracts in head, ricey etc.) before weighing.
1984.
Methods for the lime x P experiment were essentially the same as in 1982-1983, except as follows: seeding date was August 3, 1983; variety was 'Inca', pre-plant fertilizer was 500 pounds/acre of 10-20-20; chlorpyrifos and carbaryl were used for insect control. Subplot treatments were made on February 6, 1984, as follows: 1) ammonium nitrate at 50 pounds N/acre, 2) ammonium nitrate at 100 pounds N/acre, 3) ammonium nitrate at 50 pounds N/acre plus 0-45-0 at 150 pounds/acre, 4) ammonium nitrate at 100 pounds N/acre plus 0-45-0 at 150 pounds/acre. Gypsum, at 150 pounds/acre, and Solubor at 2 pounds B/A were applied to all plots on the same date. Nitrogen treatments were reapplied on March 9. Leaf samples were taken on March 14. First harvest was on March 14 and plots were harvested weekly through April 20.
In a separate experiment, 'Inca' cauliflower was seeded on an area of Willamette soil which had received a uniform application of lime at 3 tons/acre in 1980. Soil pH at planting was 6.1. All practices were as above, except that the following side dressed treatments were applied at 100 pounds N/acre on February 6, 1984: 1) ammonium nitrate, 2) ammonium sulfate (21-0-0-24), 3) calcium nitrate (15.5-0-0), 4) urea (46-0-0). Treatments were reapplied at 100 pounds N/acre on March 9. Leaf samples were taken from all plots on March 14.
Results and Discussion
1983.
Initial seedling stands increased slightly with increasing lime rate (data not shown) but, after thinning, there were essentially equal stands on all plots. Application of lime tended to increase yield of grade #1 heads at the first harvest only (Table 1). In general, yields of #1 heads were lower at the highest rate of lime than at the intermediate rates. Lime had no effect on mean head weight of all heads but did increase weight of # 1 heads at the first harvest. The number of grade #1 heads harvested/plot also tended to be higher with lime at the first harvest, but the increase was not statistically significant. Both the increase in mean weight of #1 heads and the increased number of heads harvested appeared to contribute about equally to the increase in #1 yield with lime. Lime had no effect on total yield over three harvests. Thus, lime appeared primarily to hasten maturity, particularly of quality heads. No specific defect affecting grade was found to be related to lime rate.
Providing N in the spring increased total yield through increased head size and increased yield of #1 heads both through increased numbers and head size (Tables 1 and 2). The N effect was equally strong through all harvests. Form of spring-applied N affected yield of #1 heads, but not total yields; the number of grade #1 heads harvested was greater with ammonium nitrate than with urea as N source. Mean head weight was not affected by N source. Greater foliar growth on ammonium nitrate-fertilized plants may have provided better curd cover and, thus, better color.
Spring-applied P application had no effect on any yield or quality parameter and there was no interaction of P and N source affecting yield or quality. There were also no significant lime x N or lime x P interactions. Highest yields of #1 heads were obtained with 4 tons/acre lime and spring-applied ammonium nitrate, either with or without P.
The lack of yield response to spring-applied P and the small response to lime might be attributed to an unusually mild winter and spring. Phosphorus availability on warmer-than-normal soils may not have limited yields. Alternatively, the lack of response to P may have resulted from low solubility and poor access to the root mass of the surface-banded application. Results of plant tissue analysis tend to confirm that neither lime nor applied P increased P availability to the plants since neither affected tissue P concentration (Table 3). Applied P also did not affect levels of the other elements.
Application of lime increased leaf Ca concentration, and decreased leaf Mn and Cu levels. Since leaf Mn levels were low even on unlimed soil, Mn toxicity is apparently not a problem at pH 5.5. Spring application of N increased leaf P, K, Mg, Zn, and Mn levels. Form of spring-applied N had no effect on the levels of measured elements (Table 3).
Table 1. Main effects of lime, rate of spring-applied N, form of spring-applied N, and spring-applied P on yield of overwintered cauliflower at first harvest, April 8, 1983 Yield Mean Mean wt. No. of grade No. of total of #1 Total head of #1 #1 heads heads Treatment heads yield wt. heads harvested/plot harvested/plot ---- T/A ---- -----lb----- Lime(T/A) 0 1.1 2.1 2.0 1.7 4.1 7.6 2 1.5 2.5 1.9 1.8 5.4 9.2 4 1.5 2.7 2.0 2.1 4.7 9.2 6 1.0 2.7 1.9 1.6 3.8 9.4 LSD(0.05) 0.5 0.5 NS 0.3 NS NS +N 1.4 2.6 2.1 1.9 4.7 8.6 -N 0.7 1.9 1.3 1.2 3.8 9.8 **Z ** ** ** * NS Amm. nitrate 1.6 2.6 2.1 1.9 5.3 8.5 Urea 1.2 2.7 2.2 1.9 4.1 8.6 * NS NS NS * NS +P 1.5 2.7 2.1 1.9 4.9 8.7 -P 1.3 2.6 2.2 1.9 4.4 8.4 NS NS NS NS NS NS Z**, *, NS: significant at 1% and 5% levels, and nonsignificant, respectively. Table 2. Main effects of lime, rate of spring-applied N, form of spring-applied N, and spring-applied P on yield of overwintered cauliflower, sum of three 1983 harvests Yield Mean Mean wt. No. of grade No. of total of #1 Total head of #1 #1 heads heads Treatment heads yield wt. heads harvested/plot harvested/plot -----T/A---- -----lb----- Lime(T/A) 0 2.6 6.5 1.5 1.6 10.8 28.0 2 2.8 6.3 1.5 1.6 11.4 27.6 4 3.1 6.7 1.7 1.7 11.7 26.7 6 2.5 6.7 1.6 1.6 10.0 27.8 NSZ NS NS NS NS NS +N 3.1 7.0 1.7 1.7 16.8 27.5 -N 1.4 4.6 1.1 1.2 7.6 27.5 ** ** ** ** ** NS Amm. Nitrate 3.4 6.8 1.7 1.8 12.9 27.4 Urea 2.7 7.1 1.7 1.7 10.8 27.7 * NS NS NS * NS +P 3.0 7.0 1.7 1.7 11.7 27.3 -P 3.1 7.0 1.6 1.7 11.9 27.8 NS NS NS NS NS NS Z**, *, NS: significant at 1% and 5% levels, and non-significant, respectively. Table 3. Main effects of lime, rate of spring-applied N, form of spring-applied N, and spring-applied P on leaf elemental concentrations of overwintered cauliflower Treatment P K Ca Mg Zn Mn Cu -----------%----------- -------ppm-------- Lime(T/A), 0 0.49 3.32 1.38 0.19 32 48 7.4 4 0.48 3.29 1.84 0.18 24 29 7.3 NSZ NS * NS * * NS +N 0.51 3.35 1.61 0.19 29 40 7.9 -N 0.41 3.13 1.63 0.17 24 34 5.2 ** * NS * * * NS Amm. nitrate 0.51 3.36 1.62 0.20 29 40 6.9 Urea 0.51 3.35 1.59 0.19 29 40 8.8 NS NS NS NS NS NS NS +P 0.52 3.40 1.65 0.19 28 42 7.5 -P 0.50 3.31 1.57 0.19 30 38 8.2 NS NS NS NS NS NS NS Z**, *, NS: significant at 1% and 5% level, and nonsignificant, respectively.
1984.
The winter of 1983-84 was unusually severe. Low temperatures of 5°F combined with 20 mph winds to severely damage the crop. Most mature leaves were broken from the plants and approximately 20% of the plants were killed. The freeze damage appeared to be responsible for several crop responses observed in 1984: 1) reduced head size, probably related to reduced plant size, 2) early onset of head formation, perhaps stress-related, 3) extension of the normal three-week harvest to more than five weeks, and 4) greatly reduced head quality with a high percentage of loose curds, leaves in the curd, and early bolting.
For the lime x P x N rate experiment, no treatment significantly affected early yield (March harvests, data not shown). Total season yields tended to be increased by liming and mean head weight was significantly increased by liming (Table 4). Lime had no significant effect, however, on production #1 heads (Table 4). Lime slightly increased leaf Ca and decreased leaf Mn and Zn concentrations (Table 5).
Total yield and mean head weight were higher with 200 rather than 100 pounds/acre of spring-applied N. The higher N rate also increased the total yield and mean head weight of #1 heads (Table 4). Leaf tissue N tended to be higher at the higher rate of N fertilizer but the effect was not statistically significant. Spring-applied P tended to increase production of both total and #1 heads, but the increases were not significant. Leaf tissue P was not affected by P application.
Lime and N significantly interacted in increasing total yield and #1 yield (Table 6): the higher N rate was much more effective in increasing yield at the 6 tons/acre lime rate than at the lower lime rates. Highest total yields were obtained with 6 tons lime/acre and 200 pounds/acre spring applied N. Highest yields of #1 heads, however, were obtained at 2 tons lime/acre and 200 pounds N.
Several interactions affected mean weight of #1 heads (Table 6). Averaged across lime rates, P increased mean head weight of #1 heads at the high N rate but not at the low N rate. The high rate of N increased mean #1 weight on limed, but not on unlimed, soil. The statistically significant lime x P interaction on #1 head weight does not appear to follow any biologically meaningful pattern. There was also a significant 3-way interaction of lime x P x N affecting mean weight of #1 heads (data not shown): the higher N rate increased head weight for all lime x P combinations except for the unlimed soil which received spring-applied P. Again, there is no apparent biological explanation for this interaction, which was probably by chance.
In summary, high yields of overwinter cauliflower are favored by soil pH above 6.0, and high rates of spring-applied N. As in 1983, sidedressed spring-applied P had little effect on yield.
In the second experiment, early and total yield were highest with urea as N source. Mean head weight was not favored by urea, however, and the yield increase was from a greater number of heads harvested (Table 7). The greater number of heads reflects a higher number of plants present on urea-treated plots. This was caused, however, by non-random variability in plant stands; there was no evidence for increased plant survival resulting from urea application. Source of N had no effect on leaf tissue concentrations of any element analyzed (data not shown). No conclusions concerning relative effectiveness of different N sources can be drawn from this experiment.
Table 4. Response of 'Inca' cauliflower to lime, spring-applied P, and rate of spring-applied ammonium nitrate, main effects, 1984 Total yield Mean head Yield of #1 Mean wt. of #1 Treatment (T/A) wt. (lb) heads (T/A) heads (lb) Lime, 0 T/A 3.4 0.66 0.7 0.89 2 T/A 3.6 0.84 0.8 0.97 4 T/A 3.5 0.79 0.6 0.94 6 T/A 4.0 0.87 0.6 1.05 LSD(0.05) NSZ 0.10 NS NS N, 100 lb/A 3.3 0.75 0.5 0.88 200 lb/A 3.9 0.83 0.8 1.04 ** * * ** P 0 lb/A 3.6 0.78 0.6 0.96 30 lb/A 3.7 0.80 0.7 0.96 NS NS NS NS Z**, *, NS: significant at 1% and 5% levels, and non-significant, respectively. Table 5. Main effects of lime, N, and P on cauliflower leaf elemental concentrations, 1984 Treatment N P K Ca Mg Zn Mn Cu -------------%-------------- -----ppm----- No lime 5.15 0.57 5.0 1.61 0.23 46 46 5.1 Lime, 4 T/A 5.15 0.58 5.0 1.90 0.22 41 31 5.8 NS NS NS * NS * ** NS -P 5.13 0.57 5.0 1.71 0.22 44 40 5.6 +P 5.18 0.58 5.1 1.80 0.23 43 37 5.3 NS NS NS NS NS NS NS NS N, 100 lb/A 5.05 0.58 5.1 1.69 0.22 44 38 5.4 N, 200 lb/A 5.25 0.57 4.9 1.81 0.23 43 39 5.5 NS NS NS NS NS NS NS NS Table 6. Interactions of lime and N, lime and P, and N and P rates on yield of 'Inca' cauliflower, 1984 Total yield Yield of #1 Mean wt.of #1 Treatment (T/A) heads (T/A) heads (lb) Lime(T/A) N(lb/A) 0 100 3.3 0.8 0.90 200 3.5 0.6 0.88 2 100 3.6 0.5 0.85 200 3.6 1.2 1.09 4 100 3.3 0.5 0.82 200 3.6 0.8 1.06 6 100 3.0 0.4 0.94 200 4.9 0.7 1.15 LSD (0.05) 0.4 0.3 0.11 Lime (T/A) P (lb/A) 0 0 0.83 30 0.95 2 0 1.01 30 0.93 4 0 0.88 30 1.00 6 0 1.14 30 0.95 LSD (0.05) 0.07 N (lb/A) P (lb/A) 100 0 0.89 100 30 0.86 200 0 1.03 200 30 1.06 LSD (0.05) 0.03 Table 7. Effect of form of spring-applied N on yield of 'Inca' cauliflower, 1984 Early yield Total yield #heads Mean head Mean wt. of N source (T/A) (T/A) harvested/plot wt. (lb) #1 heads (lb) Ammonium nitrate 0.1 2.9b 23.5b 0.80 0.88 Ammonium sulfate 0.1 3.3b 24.0b 0.88 1.17 Calcium nitrate 0.1 3.1b 24.5b 0.84 1.19 Urea 0.2 4.4a 35.0a 0.81 1.00 LSD(0.05) NS 0.6 4.9 NS NS