CRDP FINAL Report Understanding Nitrogen Dynamics in Cabbage April 1, 2014 to March 31, 2015

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1 CRDP FINAL Report Understanding Nitrogen Dynamics in Cabbage April 1, 2014 to March 31, 2015 PI: Christy Hoepting, CCE Cornell Vegetable Program, Albion, NY Technical Advisor: Stephen Reiners, Dept. of Horticulture, NYSAES, Geneva, NY Summary In 2013, the Cabbage Research and Development Program (CRDP) made nitrogen fertility one of their highest research priorities. In response, we studied nitrogen dynamics in cabbage with respect to total rate applied nitrogen and timing of application (proportion applied pre and/or at planting compared to side dressed) in order to determine the appropriate use and timing of nitrogen in cabbage in order to improve efficiency, optimize rates, and reduce environmental contamination from nitrogen leaching and/or lodging in following winter wheat crop. A small plot trial was set up in commercial field of storage cabbage (c.v. Constellation) with five rates of total applied nitrogen (31, 66, 132, 197 and 262 lb/a) and three application timings (100:0; 50:50 and 25:75 atplanting: side dress). To study the variability of available nitrate nitrogen remaining in the soil at harvest of summer cabbage, a small survey was conducted. Within a period of 8 days between Aug 25 and Sep 2, nine fields of summer cabbage that were either just harvested or being harvested were sampled for available nitrate N. The 2014 growing season had ample rainfall and was excellent for growing high yielding cabbage. Total rate of applied nitrogen most strongly affected head size and estimated yield. As rate of applied nitrogen increased, yield increased. The ceiling was not hit in 2014, which was conducive to excellent cabbage growth and yields: yield was still increasing with 262 lb/a of total applied nitrogen. Unfortunately, the small plot trial was affected by club root disease, the severity of which increased as rate of total applied nitrogen increased. It is unknown whether there would have been more or less of a crop response to nitrogen if the cabbage was healthy. Yield response to total rate of applied nitrogen was different among application timings. The 25:75 and 50:50 split applications between planting and side dressing peaked at 132 to 197 lb/a, while the 100:0 timing (all at planting) was still climbing at 262 lb/a. Yield response was not predicted by available soil nitrate N at mid season. The highest rate of applied nitrogen (262 lb/a) had significantly higher available nitrate N in mid season and at harvest than 31, 66, 132 and 197 lb/a, which were not significantly different from each other. Applications of 197 and 262 lb/a resulted in 33% (49 lb/a) and 69% (107 lb/a) more nitrogen than was estimated to be used by the cabbage crop. It is not known what happened to the excess nitrogen. There were no significant differences in potentially mineralizable nitrogen (PMN) at harvest. Most efficient use of nitrogen occurred when 132 lb/a was applied in a split application (25:75 or 50:50); the crop used what was applied. 1

2 In our survey of nine summer cabbage fields, total amount of nitrogen applied by the growers ranged from 72.5 to 210 lb/a and the proportion applied at or prior to planting ranged from 15 to 100% with the remainder being applied in 1 to 2 side dressings. In our survey of nine summer cabbage fields, the average available nitrate N at harvest was 9.0 lb/a and ranged from 2.1 to 43.3 lb/a. Thirty three percent of the individual soil samples had lower levels of available nitrate N than what occurred in our field trial, while only 1 sample (= 3.7%) had a higher value than the highest level that occurred in our research trial. Generally, these levels did not appear to be excessive prior to winter wheat, although there could be hot spots within a field. In our survey of nine summer cabbage fields, there were no consistent trends among total applied nitrogen, application timing and available nitrate N remaining in the soil at harvest. Introduction In 2013, the Cabbage Research and Development Program (CRDP) made nitrogen fertility one of their highest research priorities. This was in response to several growers experiencing lodging in their winter wheat when it follows cabbage. Lodging of wheat is caused when too much nitrogen fertilizer is used, especially when the growing conditions favor excessive growth. Lodged wheat can result in decreased combine speed because of the amount of straw that must be processed through the combine and decreased grain recovery. Despite choosing good varieties, establishing the correct stand and using the recommended amount of fertilizer nitrogen, lodging can still occur when there is a large carryover of residual soil nitrogen from the previous crop. For cabbage, Cornell recommends 100 to 120 lb N per acre with 40 lb broadcast and incorporated prior to planting, 40 lb in the band at planting and 20 to 40 lb side dressed 4 weeks after seeding. Some growers use 200 lb of nitrogen or more and the proportion applied prior to and at planting compared to the amount that is side dressed ranges from approximately 25% to 100%. The time to maturity of summer cabbage, which precedes winter wheat in rotation, ranges from 65 to 80 days. Previous studies have shown that storage varieties that take 90 to 120 days to mature were more likely to respond to higher rates of nitrogen, which suggests that nitrogen needs may vary according to days to maturity. In a recent study in Ontario, Canada ( ), no significant differences in cabbage yield occurred in a mid season variety among 0 lb, 75 lb, 150 lb, 225 lb and 300 lb of applied nitrogen per acre where 75% was applied pre plant and 25% was side dressed in a dry year. Alternatively, in a wet year, yield and head size increased significantly up to 235 lb/a. These results suggest that weather conditions can greatly affect the amount of nitrogen required by a cabbage crop and it is conceivable that a lot of nitrogen residual may remain following a cabbage crop in certain years. Objectives 1. To study nitrogen dynamics in summer cabbage with respect to total rate applied and timing of application (proportion applied pre and/or at planting compared to side dressed) in order to determine the appropriate use and timing of nitrogen in cabbage. 2. To refine use of nitrogen in cabbage to improve efficiency, optimize rates, and reduce environmental contamination from nitrogen leaching and/or lodging in following winter wheat crop. 2

3 Methods To study nitrogen dynamics in cabbage, a small plot trial was established in a commercial field of storage cabbage (c.v. Constellation) in Hamlin, NY. The grower cooperator left an area 85 feet wide by 175 ft long without any pre plant or side dress fertilizer applications, but fitted, transplanted and managed the trial area for weeds, diseases and insect pests, as he did the rest of the field. The trial was arranged as a randomized complete block design with 18 treatments and 5 replications. Five rates of total applied nitrogen included 31, 66, 132, 197 and 262 lb N per acre, which were applied at three application timings including atplanting: side dress ratios of 25:75, 50:50 and 100:0. Also, an untreated check with no applied nitrogen was included, which contained 2.2 lb/a of nitrogen, which could not be avoided due to nitrogen being a component of mono ammonium phosphate (MAP) fertilizer. Also, 66 and 132 lb/a at 100:0 timing without sulfur were included. Each treatment replicate was 7.5 ft x 19 ft and included 3 rows of cabbage with 2.5 ft row spacing and 1.5 ft plant spacing. Phosphorous (12.1 lb/a), potassium (136 lb/a) and sulfur (66.15 lb/a) were included in each treatment and were the same as what the grower applied to the rest of his field according to soil test recommendations. Fertilizer blends were made individually for each treatment replicate using urea (46 0 0), MAP ( ), potash (0 0 62) and elemental sulfur (90% S) for nitrogen (N), phosphorous (P), potassium (K) and sulfur (S) sources, respectively. One day after the field was planted on June 10, the trial was set up and dry fertilizer applied by hand and then raked in (Fig. 1). Five weeks after the trial was transplanted on July 10, the nitrogen side dress treatments were applied using liquid urea ammonium nitrate (30 0 0). To apply the nitrogen side dress, a 2 3 inch deep drench was dug with a hoe halfway between the first and second, and between the second and third rows of cabbage in each treatment replicate, then 2000 ml of nitrogen solution were evenly poured by hand into the trenches, and covered up using the hoe (Fig. 2). In mid season on August 18, composite soil samples were taken from each treatment in reps 1,3 and 5 and sent to Cornell Nutrient Analysis Laboratory (CNAL) for available nitrate nitrogen (NO 3 N) analysis. At harvest on October 18, composite soil samples were taken from each treatment in reps 3 5 and sent to CNAL for available nitrate N and potentially mineralizable nitrogen (PMN) analysis. At harvest, rep 1 was abandoned due to heavy weed pressure. Only the inside marketable cabbage heads (starting 2 heads in from each side) of the inside row of cabbage were harvested for about 6 8 heads per treatment replicate. Because club root occurred in the trial, each plant was uprooted, scored for club root severity and weighed individually after trimming to two wrapper leaves. Club root was scored on a scale of 0 to 3 with 0 = no club root, 1 = some club root, but mostly healthy roots, 2 = a lot of club root with some functioning roots and 3 = severe club root with no functioning roots (Fig. 3). Estimated yield in ton/a was extrapolated from the area that the number of sound heads per treatment replicate would have taken up. Onion thrips severity was assessed only in rep 5, because the time consuming assessment was abandoned when no obvious treatment effect was observed. On 5 cabbage heads per treatment replicate, the number of layers with thrips damage were counted and overall severity of damage (scale: 0 5; 0 = none; 1 = minor; 2 = minor moderate; 3 = moderate; 4 = moderate severe, 5 = severe) scored. Differences among all 18 treatments were analyzed using General Analysis of Variance (ANOVA) and means separated using Fisher s Protected Least Significant Difference (LSD) test with 5% significance. Yield data was analyzed with club root severity as a covariate and since a significant covariate did not occur, data was analyzed with club root infected plants included. When treatments were analyzed according to total rate of nitrogen and application timing, the untreated and non sulfur treatments were dropped. Relationships between factors were analyzed using Pearson correlations with 5% significance. To estimate how much nitrogen was used up by the cabbage crop, estimated yield in ton/a was used, cabbage heads were assumed to be 90% water and 10% dry matter, and of the dry matter 2% was assumed to be nitrogen. To study the variability of available nitrate N remaining in the soil at harvest of summer cabbage, a small survey was conducted. Within a period of 8 days between Aug 25 and Sep 2, nine fields of summer 3

4 cabbage that were either just harvested or being harvested were sampled for available nitrate N. Composite samples were collected from three sections of the field, front, middle and back and sent to CNAL for analysis. Background information was collected from the grower cooperators including planting date, variety, fertilizer applied and crop rotation to compare if management practices influenced the amount of nitrogen remaining in the crop at harvest. Results: Club root: Unfortunately, the small plot trial had club root. Significant differences in club root severity occurred among treatments with a significant trend that club root severity increased as total applied nitrogen increased, (Table 1, Fig. 4). Significant positive correlations occurred between club root severity and available nitrate N both in mid season (R = ; p = ) and at harvest (R = ; p = ) (data not shown). Such results imply that club root is favored by higher nitrogen. Since club root is favored by lower ph, it is possible that the acidic nature of the nitrogen fertilizer may have created a slightly more acidic environment that was more favorable for club root in the higher nitrogen treatments. When severity of club root was analyzed as a covariate, it did not appear to significantly confound the yield results. Trends among treatments were the same whether the data was analyzed with or without club root infected plants (Table 1). Thus, healthy and infected heads were analyzed together. Despite slightly higher damage from club root as applied nitrogen increased, average head size and yield still increased as applied nitrogen increased. We wonder if we would have saw an even greater response to nitrogen in the absence of club root? Head size and Estimated Yield: The most important factor driving head size and total yield was the total rate of applied nitrogen (Fig. 5). When total rate of nitrogen was pooled across application timings, the results suggest that the cabbage crop would continue to respond to increasing rates of applied nitrogen beyond 262 lb/a. For example, we could extrapolate that 483 lb/a and 615 lb/a of nitrogen would need to be applied to achieve 50 ton/a in yield and 10 lb head size, respectively (Fig. 5). However, a significant interaction occurred between total rate of nitrogen applied and application timing for head weight (p=0.0043), which means that head weight responded differently to nitrogen rate depending on the application timing (Fig. 6). When 100% of the nitrogen was applied at planting, there was a general increase in head weight as rate of applied nitrogen increased; at 262 lb/a head weight was still increasing as rate of applied nitrogen increased (Fig. 6a). When nitrogen was applied in split applications, there were no significant differences in head weight among 132, 197 and 262 lb/a of applied nitrogen, which implied that the maximum response to nitrogen when applied in split applications occurred at 132 lb/a (Fig. 6 b & c). Similar trends, although not a significant interaction, occurred for estimated yield (Fig. 7). For example, 262 lb/a 100:0 applied all at planting (40 ton/a) yielded numerically the same as 197 lb/a 25:75 when 25% was applied at planting and 75% at side dressing (41.9 ton/a). This suggests that lower rates of total nitrogen applied in split applications may be as effective as when higher rates are applied at once at planting, and thus, a more efficient use of nitrogen fertilizer. Leaving sulfur out of the fertilizer blend at planting did not have any effect on head size or estimated yield (Table 1). Available Soil Nitrogen: When application timing was pooled across total rate of applied nitrogen, levels of available nitrate N in the soil were higher in mid season than at harvest (Fig. 8). The highest rate of applied nitrogen (262 lb/a) had significantly higher available nitrate N in the soil than all of the other treatments in both mid season and at harvest. There were no significant differences among 31, 66, 132 and 197 lb/a in available nitrate N in mid 4

5 season or at harvest (Fig. 8). There was a significant interaction between total rate of applied nitrogen and application timing on available nitrate N in mid season (Fig. 9). When 262 lb/a of total nitrogen was applied, the split applications had significantly double (50:50) and triple (25:75) the amount of available nitrate N in the soil at mid season compared to when all of the nitrogen was applied at planting (100:0) (Fig. 9). In the split applications, available nitrate N in the soil was significantly higher in the 262 lb/a treatment, and there were no differences among 31, 66, 132 and 197 lb/a of applied total nitrogen. When 100% of the nitrogen was applied at planting, there were no significant differences in available soil nitrate N among any of the applied rates of nitrogen. Available soil nitrate N was not a predictor of final yield (Fig. 10). Interestingly, when only 2.2 lb/a of nitrogen was applied as a component of MAP fertilizer, available nitrate N in mid season (31 lb/a) and at harvest (11.2 lb/a) was not significantly different than any of the treatments except for the split applications of 262 lb/a (Table 1). These results suggest that the soil in this trial site already had a nitrogen source. Estimated crop use of nitrogen (Table 2): Where no additional nitrogen was applied other than 2.2 lb/a from MAP fertilizer, we estimated that the resulting 22 ton/a crop used approximately 87 lb/a of nitrogen from the soil. Again, these results suggest that the soil at our trial site had a source of nitrogen other than the applied fertilizer. A pre fertilizer soil test would have been informative. Where 31 and 66 lb/a of total nitrogen were applied, the amounts used by the crop exceeded the amount that was applied. The amount used by the crop was equal to the amount applied when 132 lb/a was applied. When 197 and 262 lb/a of nitrogen was applied, these amounts exceeded the amount used by the crop by 49 lb (= 33% excess) and 107 lb (= 69% excess), respectively. It is unknown where the excess nitrogen may have gone as only 21% and 31% of available nitrate N was in the soil at harvest in the 197 and 262 lb/a total applied nitrogen treatments, respectively. Theoretically, it could have leached, or been tied up in weeds or microbial bodies, the latter two of which could serve as a source of nitrogen for a future crop. Interestingly, there were no significant differences among treatments for potentially mineralizable nitrogen (PMN) at harvest, which averaged 42.6 lb/a across the trial and ranged from 30.5 to 50.7 lb/a (Table 1). Onion thrips: Onion thrips damage was only evaluated in one replicate (5 sound heads per treatment), because it did not appear that there were any differences. In general, thrips damage was very similar among treatments with perhaps slightly more damage in the 262 lb/a treatments. For nitrogen to have a meaningful effect on onion thrips, we would expect very little damage where no or low levels of nitrogen was applied and high levels of damage where higher rates of nitrogen was applied; our preliminary data do not suggest a relationship between applied nitrogen and onion thrips injury. Summer Cabbage Harvest Nitrogen Survey (Tables 3 & 4): The average available nitrate N of the nine fields at harvest was 9.0 lb/a and ranged from 2.1 to 43.3 lb/a. Thirty three percent of the individual soil samples had lower levels of available nitrate N than what occurred in our small plot research field trial, while only 1 sample (= 3.7%) had a higher value than the highest level that occurred in our research trial. In the some fields the variability (standard deviation) was quite high and ranged from 8 to 85% of the field average. The total amount of nitrogen applied by the growers to their summer cabbage crops ranged from 72.5 to 210 lb/a. All of the nitrogen was applied at planting (100:0) in two fields, while it was applied in split applications in the other seven fields. Of the fields with split applications of nitrogen, three were close to 50:50 splits between at planting and side dressing, two had the majority of nitrogen applied at side dressing and the other had a 43:57 split between winter manure and at planting. The field that had the lowest available nitrate N at harvest (mean 2.29 lb/a) had 105 lb/a of total applied nitrogen applied all at planting (100:0) to 5

6 sandy loam soil following field corn. The second lowest available nitrate N at harvest (mean 2.91 lb/a) had 150 lb/a total applied nitrogen applied in a 40:60 split between planting and two side dressings to silt loam following wheat and a wheat/radish/rye cover crop. Thus, there were no consistent trends between the two fields that had the lowest available nitrate N at harvest. The field that had the highest (21.83 lb/a) and most variable (std dev.: ± 85%) available nitrate N at harvest had an unknown amount of nitrogen applied at planting and 130 lb/a of nitrogen applied in two side dressings to silt loam following soybeans. The field that had the highest total applied nitrogen (210 lb/a) applied at 43:57:0 (winter: planting: side dressing) actually had a fairly low amount (4.97 lb/a) and one of most variable (std dev.: 61%) levels of available nitrate N at harvest, which was applied to a field of gravelly sandy loam/loamy fine sand following potatoes. Comparatively, the field with the second highest total applied nitrogen (185 lb/a) applied in 23:77 split application between planting and side dressing to silt loam following soybeans had almost double the amount of available nitrate N at harvest (9.73 lb/a); a trend similar to what we observed in our research trial. The field that had the least total nitrogen (72.5 lb/a) applied all at planting (100:0) to loam following field corn with rye cover crop had similar available nitrate N at harvest (10.03 lb/a) as the 185 lb 23:77 field; opposite to our observations in the research trial. The Cornell Guidelines for field crops recommend 80 to 120 lb/a of nitrogen for winter wheat. Once a wheat crop takes up 150 lb/a it is prone to lodging. Although there may be some opportunity to reduce rate of applied nitrogen fertilizer proceeding winter wheat in a field following summer cabbage, generally these levels do not appear to be excessive prior to winter wheat. However, there may be some hot spots within a field where the nitrogen is much higher. Future Research: Weather conditions can greatly affect the amount of nitrogen required by a cabbage crop. Therefore, it would be ideal to repeat the field trials in multiple years with different weather. It would be ideal to repeat the field trials in the absence of club root. More research is required to understand nitrogen dynamics in cabbage production, especially with respect to application timings. Where does the nitrogen go? Ideally, soil samples should be collected before the field is fertilized and soil and tissue analysis should occur throughout the growing season. An increased response to nitrogen is expected with longer day varieties (storage vs. summer cabbage). It would be interesting to study the effect of days to maturity on nitrogen dynamics in cabbage. 6

7 Fig. 1. Within a day of transplanting cabbage (c.v. Constellation), dry formulations of fertilizer were individually blended per treatment and spread by hand and hoed in in each plot. Fig. 2. Five weeks after transplanting, nitrogen side dressings were applied by first digging a trench halfway between each row with a hoe (left), then evenly pouring 2000 ml of fertilizer solution into the trench (middle), and then covering up the trench (right). 7

8 Club Root Severity None = 0 Minor = 1 Moderate = 2 Severe = 3 No club root All healthy roots Club root starting, mostly healthy roots A lot of club root, some functioning roots Virtually no functioning roots Fig. 3. Club root severity scale (0 3). Fig. 4. Effect of total applied nitrogen (application timings pooled) on club root severity (scale: 0 3) in storage cabbage. 8

9 Table 1. Understanding nitrogen dynamics in cabbage (cv. unknown storage variety), field trial, Hamlin, NY, Treatment (Applied Nitrogen in lb/a) 1 Total Ratio Plant: Side Rate at Planting (Jun 10) Rate at Side dress (Jul 10) Available NO 3 N in soil (lb/a) Mid Season (Aug 18) Harvest (Oct 14) PMN 2 in lb/a Harvest (Oct 14) Onion Thrips (Oct 14) Depth (No. layers damaged) Severity (scale: ) Club Root Rating 4 (Scale 0 3) (Oct 14) Average Head Size (lb) (Oct 14) 3 With Club root Without Club root Estimated Yield (Ton/A) (Oct 14) With Club root Without Club root na cd cde ef 3.4 g 4.0 g 21.7 f 27.3 e 31 25: cd 15.2 cde a d 3.9 fg 4.7 g 23.1 ef 29.4 e 31 50: cd 5.4 e f 3.9 fg 4.8 g 24.1 d f 28.6 e : d 12.4 cde def 5.4 de 6.4 f 32.2 b e 36.3 cde 66 25: cd 6.9 de ab 4.9 ef 6.7 def 28.6 c f 38.5 a e 66 50: cd 7.0 de def 5.3 de 6.6 ef 31.1 b f 37.5 b e : cd 6.1 de b e 5.7 cde 6.7 ef 33.2 a e 39.9 a e 66 no S 100: cd 5.5 e def 5.6 de 6.2 f 32.7 b e 34.6 de : cd 7.2 de a d 6.1 b e 7.7 cde 36.4 abc 42.3 a d : cd 22.3 abc ab 6.1 b e 8.2 a d 34.6 a d 48.9 abc : cd 21.1 bc abc 4.9 ef 6.3 f 28.5 c f 35.1 de 132 no S 100: cd 16.9 cd a 5.7 b e 7.9 b e 32.0 b f 46.6 a d : cd 10.5 cde b e 7.3 a 8.9 abc 42.7 a 50.6 ab : cd 9.8 cde a 6.9 abcd 9.1 ab 37.7 abc 51.5 ab : c 10.5 cde ab 5.3 de 6.7 ef 29.5 c f 38.2 b e : a 20.4 bc a 6.9 abc 8.7 abc 40.2 ab 50.3 ab : b 39.6 a a 6.3 a d 9.2 ab 36.2 abc 48.3 abc : c 38.8 ab abc 6.9 ab 9.3 a 40.0 ab 53.8 a P Value (α=0.05): NS 8 NA NA Reps evaluated: 1,3,5 3,4,5 3,4, ,3,4,5 2,3,4,5 2,3,4,5 2,3,4,5 2,3,4,5 1 All treatments include 10.6 lb P lb K lb S (except where indicated). 2 PMN: potential mineralizable nitrogen. 3 Because of club root in the trial, each plant was rated for club root severity and then weighed. Only marketable heads were included (usually 7 9 heads/plot). Without club root includes heads with no (=0) or minor (=1) club root. 4 Club root severity rating per plant: 0 = none; 1 = minor (trace); 2 = moderate (healthy root tips present); 3 = severe (no healthy roots left). 5 Onion thrips severity scale: 0 = none, 1 = minor (trace); 2 = minor moderate; 3 = moderate; 4 = moderate sever; 5 = severe. 6 from 11% N in MAP fertilizer. 7 Numbers followed by the same letter in a column are not significantly different, Fisher s Protected LSD test (p< 0.05). 8 NS: Not significant. 9 Na: Not applicable. 9

10 Pooled Data Mean Estimated Yield (Ton/A) Application timings pooled across applied nitrogen rate a ab bc abc c y = x R² = p = lb 66 lb 132 lb 197 lb 262 lb Rate of Total Nitrogen Applied (lb/a) Mean head weight (lb) Application timings pooled across applied nitrogen rates ab a bc abc c y = x R² = p = lb 66 lb 132 lb 197 lb 262 lb Rate of Total Applied Nitrogen (lb/a) Fig. 5. Effect of total applied nitrogen (lb/a) (application timings pooled) on mean estimated yield (above) and mean head weight (below): as applied nitrogen increases, yield and head weight increase. The ceiling was not yet reached during a year conducive for excellent cabbage growth. 10

11 a) b) c) Fig. 6. Effect of total applied nitrogen on harvested head weight of storage cabbage when applied at different timings. Response to total applied nitrogen varied according to application timing with most efficient use with split applications. 11

12 Cabbage Yield (ton/a) c Effect of Nitrogen Timing on Yield Maximum response to applied 132 lb bc ab 31 lb 66 lb 132 lb Fig. 7. Effect of timing of nitrogen application on cabbage yield (cv. Constellation): Response varied according to application timing with most efficient use of nitrogen with split applications Total Rate of Applied Nitrogen (lb/a) a a Maximum response to applied N at 262 lb 197 lb 262 lb Ratio of Total Rate Applied At plating: side dress 25:75(p = ) 50:50:00 100:00:00 Fig. 8. Effect of total applied nitrogen on available nitrate N in the soil in mid season (Aug 18) and at harvest (Oct 14) (application timings pooled) of storage cabbage. 12

13 Fig. 9. Effect of timing of nitrogen application on available soil nitrate N in mid season (Aug 18) in storage cabbage: Response varied according to application timing with highest levels occurring in the split applications. 13

14 a) b) c) Fig. 10. Comparison of available soil nitrate in mid season to estimated cabbage yield at different application timings: available soil nitrate in mid season is not a predictor of yield. 14

15 Table 2. Comparison of total applied nitrogen (pooled among application timings) to cabbage (cv. Constellation) yield, available soil nitrate at mid season and at harvest, and to the estimated amount of nitrogen used by the crop. Hamlin, NY: Total Rate of Applied Nitrogen (lb/a) Estimated Yield (ton/a) 1 Available soil nitrate N (lb/a) Mid season (Aug 18) Harvest (Oct 14) Estimated amount of nitrogen used by crop 2 (lb/a) Difference between amount of nitrogen applied and used by crop b 11.2 b c b 11.0 b bc 20.5 b 7.0 b abc 29.0 b 16.8 b ab 42.6 b 10.3 b a 95.8 a 32.9 a P value Na (α=0.05) 5 Na 5 1 Estimated yield: total weight of only the number of healthy heads harvested per plot is extrapolated to a per acre basis based on the area that the number of healthy heads would occupy; thus, estimated yield is skewed towards a higher than actual yield. 2 Estimated amount of nitrogen used by crop: Used mean yield (ton/a), assumed cabbage is 10% dry matter by weight, and of that it was assumed that 2% was nitrogen. 3 single treatment, not included in dataset for statistical analysis. 4 Numbers in a column followed by the same letter were not significantly different, Fisher s Protected LSD test, p> Na: not applicable to conduct statistics, used means to estimate nitrogen used. 15

16 Table 3. Survey of summer cabbage at harvest for available nitrate N, 2014: Field Information. Field No. County Location Soil Type 2013 Crop Cover Crop Variety Planting Date 1 Genesee Elba Ontario loam Corn Rye Grand Vantage, Vantage Point May 23 2 Genesee North Byron Lima/Appleton silt loam/ontario loam Corn None Bronco May 12 3 Genesee North Byron Loam, Ontario/Hilton/Ovid/Lima Soybeans Oats Bronco May 20 4 Genesee Elba Silt loam Lima/Appleton/mucky Soybeans None Capture May Monroe Hamlin Collamer silt loam Wheat Wheat, radish, rye?? 6 Monroe Hamlin Silt loam Collamer/Dunkirk/Niagara Soybeans None Bayonette May 15 7 Monroe Spencerport Colonie loamy fine sand Alton gravelly sandy loam Potatoes None Super Star May 6 8 Niagara Newfane Sandy loam Super Elite, Bronco, Corn None Galen/Minoa Super Red 80 3 rd week of May 9 Ontario Flint Silt loam Lima/Honeoye Corn None Bronco May

17 Table 4. Survey of summer cabbage at harvest for available nitrate N, 2014: Nitrogen fertilizer applications and soil test results. Nitrogen Fertilizer Application Harvest Available Nitrate Nitrogen at Harvest Field Total Ratio Type Sampling No. Standard Rate Timing Applied N (plant: NO3 N (N P K) Date (lb/a) side dress) (lb/a) 1 Average deviation and in % lb/a PPI Total: :0 Aug B 10S 32% UAN liquid B 10S 32% UAN liquid 4?? 5 6 7?????? S 0.4B 32% UAN liquid Dairy manure lb/a 20 gal/a 20 gal/a 700 lb/a 40 gal/a 6000 gal/a 400 lb/a PPI Side dress 4 weeks PPI Side dress 4 weeks PPI Side dress 2 weeks Side dress? weeks PPI & transplant Side dress 4 weeks Side dress 6 weeks PPI & transplant Side dress 4 week Side dress 6 week Top spread in winter PPI Total: Total: 157? Total: Total: Total: Total: :52 Aug 25 48:52 Aug 25?:? Aug 25 40:60 Aug 28 23:77 Aug 28 43:57:0 Aug lb/a PPI Total: :0 Aug ? 300 lb/a? PPI? Total: :85 Sep abc (48%) 7.22 bc ab a 2.91 d 9.73 abc 4.97 cd 2.29 d ab 1 composite samples taken from the front, middle and back section of field. 2 yellow highlights indicate values lower than what we found in our trial (< 5.4 lb/a). Blue highlights indicate values higher than what we found in our trial (> 39.6 lb/a). 3 Numbers in a column followed by the same letter are not significantly different, Fisher s Protected LSD test, p = (8%) 2.02 (17%) (85%) 0.88 (30%) 3.35 (34%) 3.01 (61%) 0.19 (8%) 1.61 (16%) 17