Overwintered cauliflower 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 this trial, the third in a series, was to investigate the effects of lime, banded P at planting, gypsum, and source and rate of N on the yield and grade of overwinter cauliflower.
Methods
'Inca' cauliflower 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 seed 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' 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
Lime tended to increase total yield slightly at the first harvest but had no effect on head quality (Table 1). 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.
Lime tended to increase total yield slightly at the first harvest but had no effect on head quality (Table 1). 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 2), 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 3).
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 1. 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 2. 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 3. 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 N source experiment, yield of grade No. 1 heads at the first harvest (Table 3) and for the season (Table 4) was higher with the strictly ammonium-N sources than with the strictly nitrate source, calcium nitrate. The mean weight of No. 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 5), highest total yield but the lowest percentage of grade No. 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 4. 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 5. 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.