As a result of the variety and planting date trials described above, overwintered cauliflower is now 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 type of spring-applied N on cauliflower yield and quality had not been investigated. Likewise, the response of overwintered cauliflower to lime, which increases P availability, had not been studied. The purpose of these trials was to investigate the effects of lime, spring-applied P, banded P at planting, gypsum, 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 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. 'Arminda' cauliflower was direct-seeded on approximately 3 feet x 4 inch 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. 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 feet) by banded surface application of the following: 1) ammonium nitrate at 50 pounds N/acre, 2) urea at 50 pounds N/acre, 3) ammonium nitrate at 50 pounds N/acre plus 100 pounds 0-45-0/A, 4) urea at 50 pounds N/acre plus 100 pounds 0-45-0, (5) no spring-applied fertilizer. Treatments 1-4 also received 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 x N rate experiment were essentially the same as in 1982-1983, except as follows: seeding date was August 3, 1983, and the variety was 'Inca'. Subplot treatments were surface banded 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 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 N sources were sidedressed at 100 pounds N/acre on February 6, 1984: ammonium nitrate, ammonium sulfate (21-0-0-24), calcium nitrate (15.5-0-0), and urea (46-0-0). The N sources were reapplied at 100 pounds N/acre on March 9. Leaf samples were taken on March 14.
1985
Methods for the lime experiment were similar to the above except as follows: 'Inca' was seeded on August 2, 1984. The lime main plots were split by a banded application of 0 or 90 pounds P205/acre, placed two inches to the side and two inches beneath the see row at planting. On February 6, 1985, the plots were again split by a sidedressed application of gypsum at 0 or 150 pounds/acre. Resulting sub/subplot size was three rows x 24 feet. Treatments, harvest rows, and plants sampled for tissue analysis came from the center row of each plot. Additional N as ammonium nitrate was applied to all plots at 75 pounds N/acre on February 6, and again on March 6. Leaf samples were collected for tissue analysis on March 25. Plots were harvested on April 15 and on April 22.
In a separate experiment, 'Inca' cauliflower was seeded on August 2, 1984, in three-foot rows on a uniformly limed area, pH 6.1. The seedling stand was thinned to 18 inch in-row spacing in late September. Napropamide was applied at 2.0 pounds/acre in October, following hand-hoeing. On February 6, 1985, the following N sources were applied at 75 pounds N/acre in a randomized block design with four replications: ammonium nitrate, ammonium sulfate, calcium nitrate, and urea. The N sources were reapplied at the same rate on March 6. Leaf samples were collected for tissue analysis on March 25. Plots were harvested on April 15 and 22.
Results and Discussion
1983
Initial seedling stands increased slightly with increasing lime rate (data not shown) but, after thinning, stands were essentially equal on all plots. Application of lime tended to increase yield of grade #1 heads at the first harvest only (Table 12). In general, yield of #1 heads was 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 12 and 13). 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 an equal N rate 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 yield or quality 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 may have resulted from low solubility and poor access to the root mass of the surface-banded application. Alternatively, the lack of response to P might be attributed to An unusually mild winter and spring. Phosphorus availability on warmer-than-normal soils may not have limited yields. 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 14). 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 14).
Table 12. 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 --tons/acre-- ----pounds--- 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 Ammonium 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 13. 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 --tons/acre-- ----pounds--- 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 Ammonium 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 14. 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 Ammonium 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% levels, 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 15). Lime had no significant effect, however, on production of #1 heads (Table 15). Lime slightly increased leaf Ca and decreased leaf Mn and Zn concentrations (Table 16).
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 15). Surface application of P in the spring tended to increase production of both total and #1 heads, but the increases were not significant. As in 1983, leaf tissue P was not affected by P application.
Lime and N significantly interacted in increasing total yield and #1 yield (Table 17): 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 17). 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.
In the N source experiment, early and total yield were highest with urea as N source. Mean head weight was not favored by urea, however. The yield increase was from a greater number of heads harvested (Table 18). The greater number of heads reflects a higher number of plants present on urea-treated plots. This was caused 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 could be drawn from this experiment.
Table 15. 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 16. 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 17. 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 18. 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
1985
Lime tended to increase total yield slightly at the first harvest but had no effect on head quality (Table 19). Gypsum had no effect on head weight or quality but fewer heads were harvested on gypsum-treated plots. This appeared to be from chance, a non-random decrease in number of plants present on gypsum-treated plots. Banded P at planting also tended to reduce the number of heads harvested/plot, with no effect on head weights when averaged over lime and gypsum treatments. There were no significant interactions affecting the first harvest.
Neither lime, gypsum, nor banded P affected yield or quality for the sum of two harvests (Table 20), when averaged over the other treatments. However, lime and banded P significantly interacted in their effects on total weight harvested for the two harvests. Banded P tended to increase yield at low soil pH but not at high soil pH (Table 21).
Treatments had no effect on leaf tissue concentrations of N, P, Ca, Mg, Zn, and Cu (data not shown). Gypsum increased leaf K level from 2.86% to 3.13%, and S level from 1.07% to 1.16%, when averaged over all treatments. In contrast to previous effects of lime application on leaf Mn levels, leaf Mn was increased from the range of 35 to 37 ppm for the lower rates of lime, to 49 ppm at the highest rate. However, only one replicate showed high leaf Mn levels at the high rate of lime.
Three years of experiments on the effects of lime and P on overwinter cauliflower yield and quality indicate that the effect of lime is small but significant when averaged over the three years. Neither a subsurface-banded application of P at planting nor a sidedressed spring P application appreciably affected yield on this soil of high P content. A single year's work indicates no response to a spring application of gypsum.
Table 19. Main effects of lime, banded P, and gypsum on yield of overwintered cauliflower at the first harvest, 1985 Treatment Yield Mean head wt. Heads/plot % No. 1 No. 1 heads All heads No. 1 All No. 1 Total heads -------tons/acre------ ---pounds--- Lime (T/A) 0 1.1 3.6 1.25 1.34 2.9 8.9 33 2 1.1 3.6 1.22 1.32 2.9 9.5 29 4 1.5 4.2 1.40 1.33 3.5 10.5 34 6 1.3 3.8 1.24 1.33 3.1 9.5 33 LSD(0.05) NSZ 0.5 NS NS NS NS NS + Gypsum 1.1 3.6 1.27 1.30 2.8 9.1 31 - Gypsum 1.3 4.1 1.29 1.35 3.3 10.1 33 NS NS NS NS NS * NS + P 1.2 3.8 1.24 1.34 3.1 9.1 34 - P 1.2 3.9 1.31 1.31 3.1 10.1 30 NS NS NS NS NS * NS ZNS;*: no significant differences; significant differences among means at 5% level. Table 20. Main effects of lime, banded P, and gypsum on yield of overwintered cauliflower, total of two harvests, 1985 Yield Mean head wt. Heads/plot % No. 1 Treatment No. 1 heads All heads No. 1 All No. 1 Total heads -------tons/acre------ ---pounds--- Lime (T/A) 0 1.5 4.9 1.28 1.31 3.6 12.5 29 2 1.2 5.0 1.17 1.25 3.3 13.4 25 4 1.6 5.1 1.43 1.30 3.7 13.1 28 6 1.4 4.8 1.26 1.19 3.5 13.4 26 NSZ NS NS NS NS NS NS + Gypsum 1.4 4.8 1.30 1.26 3.4 12.8 27 - Gypsum 1.4 5.1 1.26 1.27 3.6 13.4 28 NS NS NS NS NS NS NS + P 1.5 4.9 1.31 1.27 3.7 13.1 30 - P 1.3 4.9 1.26 1.25 3.3 13.2 26 NS NS NS NS NS NS NS ZNo significant differences Table 21. Interaction of lime and banded P on total yield of overwinter cauliflower, 1985 Lime Rate P rate (pounds/acre) (tons/acre) 0 90 ---- tons/acre ---- 0 4.6 5.3 2 4.9 5.0 4 5.4 4.7 6 4.8 4.8 LSD(0.05) = 0.5
In the 1985 N source experiment, yield of grade #1 heads at the first harvest (Table 22) and for the season (Table 23) was higher with the strictly ammonium-N sources than with the strictly nitrate source, calcium nitrate. The mean weight of #1 heads was increased by ammonium-N at the first harvest but not for the sum of two harvests. Mean weight of all heads was not affected by N source.
For the sum of both harvests (Table 23), highest total yield but the lowest percentage of grade #1 heads was obtained with calcium nitrate. More foliar growth on ammonium N-fertilized plants may have provided more cover for the curd and improved curd color and quality.
Source of N had no effect on leaf tissue concentrations of N, P, K, Ca, Mg, S, Zn, and Mn (data not shown). Leaf Cu level was significantly higher with urea as N source (11.9 ppm) than with the other N sources (6.9-7.1 ppm).
While indicating a significant advantage to providing an ammonium-N source, these results do not agree entirely with results obtained in 1983 and 1984. Larger scale experiments will be needed to determine if there are significant advantages to use of a certain N source or if choice of N source should be determined only by price.
Table 22. Effect of N source on yield of overwinter cauliflower at first harvest, 1985 No. of heads Yield of Mean head wt. % No. 1 N source harvested/plot No. 1 heads All heads No. 1 All heads -------tons/acre------- ---pounds--- Amm. nitrate 8.8 1.3 3.3 1.38 1.27 37 Amm. sulfate 10.3 2.2 4.4 1.31 1.42 54 Calcium nitrate 9.5 0.7 4.4 1.01 1.49 24 Urea 10.0 2.5 4.2 1.50 1.37 53 LSD(0.05) NS 1.3 NS 0.35 NS 18 NS: no significant differences. Table 23. Effect of N source on yield of overwinter cauliflower, total of two harvests, 1985 No. of heads Yield of Mean head wt. % No. 1 N source harvested/plot No. 1 heads All heads No. 1 All heads ----- tons/acre ------ ---pounds--- Amm. nitrate 14.8 2.0 5.5 1.50 1.23 31 Amm. nitrate 13.5 2.3 5.1 1.28 1.33 44 Calcium nitrate 17.0 1.2 7.3 1.46 1.42 16 Urea 13.5 2.5 5.5 1.50 1.31 39 LSD(0.05) NS 0.9 1.0 NS NS 11 NS: no significant differences.