Nitrogen Fertilizer Rate and Placement on Cauliflower Yield (1992)

Research report from OSU's North Willamette Agricultural Research and Extension Center

Delbert Hemphill
OSU Dept of Horticulture, NWREC

John Hart
OSU Dept. of Crop and Soil Science


Cauliflower is also planted at lower populations and with greater between-row spacing than is the norm for broccoli. The purpose of this trial was to study the response of cauliflower to several rates of applied N fertilizer and combinations of banded versus broadcast placement of both the initial and sidedressed fertilizer applications. A second purpose was to study soil N accumulation as a function of rate of applied N and presence of a winter catch crop, and to monitor movement of nitrate through the soil profile in the winter following the crop.


'Snowball Y' cauliflower was direct-seeded in a Willamette silt loam, pH 5.9, at the NWREC on 3 June. Rows were 12 inches apart with a plant density of about two/inch in the row. Plot preparation included a broadcast and incorporated application of 10N-8.7P-16.7K fertilizer at 600 pounds/acre, boron at 2.0 pounds/acre, trifluralin at 0.75 pounds/acre, and chlorpyrifos at 1.3 pounds/acre. On 14 July, the seedlings were lifted with a shovel and transplanted bare-root into their final location. Soil preparation was the same as for the seed bed. Transplants were set in rows 2.5 feet apart with 18 inches between plants in the row. Plot size was three rows, 20 feet long. All three rows were harvested. The initial application of 40 pounds N/acre, as urea, was either broadcast or banded 3 inches to the side and 2 inches deep immediately after transplanting and irrigated in. The remaining urea was broadcast or banded on the appropriate plots on 20 August (Table 1). Treatments were in randomized complete block design with four replications. The plots were sprinkler-irrigated as necessary and harvested on 29 September and 5 and 15 October. In addition to the combination of nitrogen rates and methods of fertilizer placement, one set of plots (treatment 12) was reserved for sequential sampling of shoot dry matter accumulation and N uptake. Another set of plots (treatment 11) received its initial N application in the form of 15N-enriched urea. These plots were harvested separately for refined determinations of N uptake. Two sets of plots (treatments 13 and 14) were interseeded with 'Wheeler' cereal rye on 3 September to determine the feasibility of overseeding in cauliflower as a means of establishing a winter N catch crop. Following the last harvest, soil in treatments 1, 2, 3, 4, 5, and 11 were sampled to 40-inch depth in 10-inch increments. The plots were maintained through the winter in order to resample for soil N content and cover crop biomass accumulation.

Results and Discussion

For the plots receiving only broadcast applications of urea, yield increased with increasing N rate to a maximum at 240 pounds/acre (Table 2). The same trend was true for mean head weight and the percentage of Grade No. 1 heads (defect-free). Previous work at the OSU vegetable farm suggested that the optimum rate of N application to cauliflower is in the range of 150 to 200 pounds/acre, somewhat lower than the results obtained in this trial.

Banded versus broadcast application of N at planting had no significant effect on yield or quality (Table 3), although there was a trend toward higher yield and head size with a banded application. Apparently, even with rows 30 inches apart, enough feeder roots establish in the soil between the rows that concentrating the fertilizer near the plant row is not a great advantage. This is in agreement with results obtained on broccoli grown on 16 or 20-inch row spacing.

Broadcast application of the sidedressed N resulted in significantly higher yield and mean head size than when the sidedressed N was banded. This was true at the 240 pounds/acre rate as well as the sub-optimal rate. The single greatest yield in this trial was with the combination of banded fertilizer at planting, broadcast sidedress fertilizer, and a rate of 240 pounds N/acre.

Overseeding cereal rye about four weeks before first harvest did not reduce cauliflower yield (Table 4). This is not surprising, as the stand of rye was sparse (approximately eight plants/square foot) and had not developed beyond the one-true leaf stage at harvest.

Results of soil tests for residual fertilizer after harvest, and for N uptake as a function of crop growth are not yet available. The soil and rye will be sampled in the spring as a function of rate of applied nitrogen to determine the amount of nitrogen leached versus that trapped in the rye shoots.


  Table 1. List of treatments, 1992 cauliflower N utilization trial, NWREC     No.   Total N applied   Placement at planting   Placement at sidedress             --------------------------lb/A----------------------------------       1           0              0                         0   2          80             40 broadcast              40 broadcast   3         160             40 broadcast             120 broadcast   4         240             40 broadcast             200 broadcast   5          80             40 banded                 40 broadcast   6         240             40 banded                200 broadcast   7          80             40 broadcast              40 banded      8         240             40 broadcast             200 banded   9          80             40 banded                 40 banded  10         240             40 banded                200 banded  11         160             40 broadcast-15N          120 broadcast-15N  12         160             40 broadcast             120 broadcast  13          80             40 broadcast              40 broadcast, overseed  14         240             40 broadcast             200 broadcast, overseed      Table 2. Effect of rate of broadcast nitrogen on yield, head size,   and quality of cauliflower, NWREC, 1992                             N rate         Mean head       Grade No. 1     Total yield  (lb/acre)       wt. (g)         heads (%)      (tons/acre)             0               430              68.3            4.8                  80               678              82.4            7.4                160               751              88.0            7.8                240               815              89.5            8.6                      LSD (0.05)  186              10.6            2.2                   Table 3. Effect of broadcast versus banded application of initial and   sidedressed N on yield, head size, and quality of cauliflower, NWREC, 1992    Placement    Placement      N rate    Mean head   Grade No. 1   Total yield  at planting  at sidedress  (lb/acre)   wt. (g)     heads (%)    (tons/acre)  Broadcast    Broadcast         80        678          82.4          7.4                                240        815          89.5          8.6                                    Mean   747          85.9          8.0                              Banded            80        633          80.6          6.6                                  240        736          90.1          7.7                                       Mean   684          85.4          7.2    Banded       Broadcast         80        727          86.2          7.0                                 240       1051          90.7         10.9                                    Mean   889          88.4          9.0                 Banded            80        549          88.7          6.2                                240        684          83.7          8.6                                    Mean   617          86.2          7.4                  Broadcast at planting mean   716          85.7          7.6              Banded at planting mean      753          87.3          8.2              Significance, planting        NS           NS            NS                Broadcast at sidedress mean  818          87.2          8.5              Banded at sidedress mean     651          85.8          7.3              Significance, sidedress       **           NS            *             Table 4. Effect of overseeding cereal rye on cauliflower yield, head size,  and quality at two rates of nitrogen, NWREC, 1992                           Treatment       N rate   Mean head   Grade No. 1     Total yield                 (lb/acre)  wt. (g)     heads (%)      (tons/acre)            Overseeded        80         649         81.0           6.4                   240         874         90.2           9.6                        Mean   762         85.6           8.0    Not overseeded    80         678         82.4           7.4                   240         815         89.5           8.6                        Mean   747         86.0           8.0                      Significance   NS          NS             NS