2008 Potato Research Report

Transcription

1 Keystone Potato Producers Association McCain Foods (Canada) Simplot Canada Limited 2008 Potato Research Report Prepared by: Gaia Consulting Ltd.

2

3 Introduction This is the 19 th report on potato research funded by Keystone Potato Producers Association (KPPA), McCain Foods Limited and Simplot Canada Limited. The Canada-Manitoba Crop Diversification Centres in Carberry and Portage la Prairie provided land and irrigation for a majority of the research trials. Other contributors are listed under the Funding heading at the beginning of each project report. On behalf of above sponsors we would like to thank everyone who contributed to the success of the 2008 potato research program. Copies of the this report can be downloaded at Anyone wanting additional information regarding the research trials can contact: Gaia Consulting Ltd. Box 314 Portage la Prairie, Manitoba R1N 3B5 Phone: (204) bgeisel@gaiaconsulting.mb.ca or dgibson@gaiaconsulting.mb.ca

4

5 Table of Contents Effect of Nitrogen and Potassium Rate and Timing on the Specific Gravity of Ranger Russet... 1 Field Survey to Determine Soil Factors Affecting Yield and Quality... 8 Effect of Hilling Type and Straw Mulch on Potato Quality Phosphorus Management for Irrigated Russet Burbank Potato Production Screening of Verticillium Wilt Resistant Potato Varieties

6

7 Effect of Nitrogen and Potassium Rate and Timing on the Specific Gravity of Ranger Russet Funding: Keystone Potato Producers 16.6% Simplot Canada 16.6% McCain Foods 16.7% Agricultural Sustainability Initiative 50% In Kind: Progress: Keller and Sons Farm Land and irrigation management Westman Aerial Spraying Aerial Spraying for insect and disease control Third Year Principal Investigators: Blair Geisel and Darin Gibson, Gaia Consulting Ltd. Introduction: The Ranger Russet potato variety is of lesser importance to the French fry processing industry than Russet Burbank, however, it does possesses desirable traits. Ranger Russet is moderately resistant to Verticillium wilt and produces higher yield than Russet Burbank in fields where the disease is present. Ranger Russet matures earlier than Russet Burbank and is used for processing approximately 6 weeks in late August and September before Russet Burbank has matured. Unfortunately, this variety produces very high specific gravities, which are undesirable for French fry processing. Previous research has demonstrated that the rate and timing of nitrogen and potassium fertilizer will affect specific gravity. The 2007 and 08 study was conducted on a coarse textured soil (Miniota Sand) in the Shilo area. Nitrogen management is challenging on these soils because frequent leaching events result in nitrogen losses. The results in this report may not apply to finer texture soils, which are less susceptible to leaching. In 2007, the early split application of urea nitrogen, the pre-plant application of ESN (slow release polymer coated nitrogen) and the application of additional potassium produced the highest yields. The application of additional potassium and the late split application of nitrogen produced the lowest and most desirable specific gravity for French fry processing. The early split application of nitrogen plus the application of higher than recommended amounts of potassium will maximize yield and optimize specific gravity. The results from 2007 trial and other trials conducted in the U.S. indicated that the K splits were applied too late to affect specific gravity. The results also left many questions unanswered such as 1) could the high specific gravity of the ESN treatment be improved by combining an at-plant ESN treatment with a urea split and 2) what would the be the effect on yield and specific gravity if urea was split multiple times throughout the growing season. This led to a revised protocol for the 2008 season which included earlier split applications of K, ESN/urea treatments and multiple split urea applications. In 2008, both the source of nitrogen and the application method had an effect on specific Page 1

8 gravity and yield. ESN/urea treatments produced higher yields and lower specific gravity than urea only treatments. In the urea only treatments, applying nitrogen in early season splits 35 and 56 days after planting (DAP) produced lower specific gravity and higher yields than applying all nitrogen pre-plant or in multiple splits 35, 56, 76 and 90 DAP. The application of extra potassium applied pre-plant or as an early season split had no effect on yield, but reduced specific gravity when compared to the pre-plant application of the recommended amount of potassium. The effect of extra potassium on specific gravity was more pronounced in the urea treatments where nitrogen was deficient. There was no difference in the specific gravity between the pre-plant or early season splits of extra potassium. Nitrogen management is challenging on coarse textured soils. The Ranger Russet requires most of the nitrogen in the first 60 days after planting (DAP) and any nitrogen deficiency during this period will reduce yield and increase gravity. Due to the high risk of leaching on coarse textured soils it is difficult to meet crop demands with urea fertilizer applied at plant. Ideally urea should be applied in a 50:50 split; 50% as a pre-plant application and 50% applied in two splits 35 and 55 DAP. This method will reduce, but not eliminate the risk of leaching and the resulting nitrogen deficiency. The pre-plant application of 50% ESN and 50% urea in two splits 35 and 55 DAP offers the best chance of meeting crop demands. The ESN component protects against leaching and provides a steady supply of nitrogen throughout the entire growing season. The split application of urea provides a readily available source of nitrogen to the plant early in the season when demand is highest. Objectives: 1. To compare the effect of polymer coated and conventional nitrogen sources on yield, grade, specific gravity and nitrate leaching. 2. To compare Ranger Russet yield, grade and processing quality between different fertility treatments on a coarse textured soil. 3. To develop a management program for producing high quality Ranger Russet with acceptable specific gravity for early harvest on coarse textured soils. Procedure: Plot size: 4 rows by 12 m (Assessments conducted on 2 centre rows) Trial design: RCB 4 replicates Plot location: Shilo Irrigated grower field Soil Texture: Miniota Sand Variety: Ranger Russet Intra-row spacing: 1 metre In-row spacing: 12.5 in. 32 cm. Residual Nutrients N-32 lb/ac, P-12 ppm, K- 114 ppm Planting date: April 29 Treatments: Table 1. Fertility Treatments. Pre-plant nitrogen and potassium Page 2

9 Table 1 List of Treatments treatments were broadcast and incorporated into the soil just prior to planting. 22-Apr 03-Jun 24-Jun 14-Jul 28-Jul At-Plant 35 DAP 1 56 DAP 1 76 DAP 1 90 DAP 1 Total Trt # Treatment N K N K N K N K N K N K 1 100% Preplant N & K % Preplant N & Extra Preplant K % Preplant N, 50% N Early Season Splits & Preplant K % Preplant N, 50% N Full Season Splits & Preplant K % Preplant N, 50% N Full Season Splits & Extra Preplant K % Preplant N, 50% N Full Season Splits & Extra Split K % Preplant ESN & K % Preplant ESN & Extra Preplant K % Preplant ESN, 50 % N Early Season Splits & Preplant K % Preplant ESN, 50% N Full Season Splits & Preplant K % Preplant ESN, 50% N Full Season Splits & Extra Preplant K % Preplant ESN, 50% N Full Season Splits & Extra Split K DAP = days after planting Harvest date: September 2 Specific Gravity Analysis: Specific gravity (SG) was determined by comparing the weight of a 4.5 kg tuber sample in air and in water. Fry Colour Analysis: The centre ½ inch fry strip from 10 tubers per plot was fried for 2 minutes 30 seconds in vegetable oil at 375 F. Fry colour was determined using the USDA scale, which ranges from "0" (light colour) to "4" (dark colour). Sugar End Analysis: If less than 1/3 of the French fry is darker than the remainder of the fry by 2 colour gradients on the USDA fry colour scale, it is defined as a sugar end. The fry colour is determined by assessing the remaining 2/3 of the fry. However, if the dark end affects more than 1/3 of the entire fry, colour is determined by assessing the dark end. Statistical Analysis: An ANOVA (analysis of variance) was performed on the assessment and yield data in tables 2-3. Mean separation was determined using the least significant difference (LSD) test. An ANOVA (analysis of variance) was performed on the transformed raw data as well as on the yield data in Table 1. Actual percent bonus tubers and hollow heart data is presented in Table 2. Mean separation was determined using the least significant Page 3

10 difference (LSD) test. Orthogonal contrasts were performed to compare specific treatments. Results: Specific Gravity Orthogonal contrasts (Table 2) and analysis of variance (Table 3) were used to analyze the data. The comments below are based on the orthogonal contrast. In 2008, both the source of nitrogen and the application method had an effect on specific gravity. ESN/urea treatments produced lower specific gravity than urea only treatments. In the urea only treatments applying nitrogen in early season splits 35 and 56 days after planting (DAP) produced lower specific gravity than applying all nitrogen pre-plant or in full season splits 35, 56, 76 and 90 DAP. The application of extra potassium applied pre-plant or as an early season split reduced specific gravity when compared to the pre-plant application of the recommended amount of potassium. The effect of extra potassium was more pronounced in the urea treatments where nitrogen was deficient. There was no difference in the specific gravity between the pre-plant or early season splits of extra potassium. The ESN/urea treatments (#s 7-12) produced specific gravity units lower than the urea only treatments (#s 1-6). Applying urea in early splits (#3) reduced specific gravity by units when compared to applying all urea pre-plant (#1). Applying all ESN pre-plant (#s 7 & 8) reduced specific gravity by units when compared to applying all urea pre-plant (#s1 & 2). Application of ESN/urea in full season splits (#s 10, 11 & 12) reduced specific gravity by units when compared to applying urea in full season splits (#s 4, 5, & 6) Applying extra pre-plant K (#s 2 & 5) reduced specific gravity by units compared to applying the recommended amount of K (#s 1 & 4). Applying extra K as a split (#6) reduced specific gravity by units when compared to the recommended amount of pre-plant K (#4) There was no difference in the specific gravity between the rate and method of potassium application in the ESN or ESN/urea treatments (#s 7-12). There was no difference in the specific gravity between the pre-plant or early season split applications of extra potassium. Full season splits of urea (#4) did not reduce specific gravity when compared to applying all urea pre-plant (#1). There was no difference in the specific gravity between the methods of nitrogen application in the ESN or ESN/urea treatments (#s 7-12). None of the ESN or ESN/urea treatments (7-12) produced a lower specific gravity when compared to applying urea in a single split application (#3). Page 4

11 Table 2 Effect of N and K on specific gravity Treatment Description Trt # Specific Gravity Trt# Specific Gravity Difference All urea to all ESN/Urea treatments * Preplant urea to early season splits of urea * Preplant urea to preplant ESN 1, , * Full season splits of urea to full season splits of ESN/urea 4,5, ,11, * Preplant recommended K to preplant extra K 1, , * Preplant recommended K to extra split K * Preplant urea to full season splits of urea 1,2 4,5 NSD Preplant ESN to early season splits of ESN/Urea 7 9 NSD Preplant ESN to full season splits of ESN/urea 7,8 10,11 NSD Early season splits of urea to early season splits of ESN/urea 3 9 NSD Preplant recommended K to preplant extra split K 7,10 8,11 NSD Preplant recommended K to extra split K NSD Extra preplant K to extra split K 5 6 NSD Extra preplant K to extra split K NSD * significant at 0.05 NSD = no significant difference Table 3 Effect of N and K on specific gravity Character Rated Sp. Gravity Rating Data Type Rating Unit 1 100% Preplant N & K a 2 100% Preplant N & Extra Preplant K abc 3 50% Preplant N, 50% N Early Season Splits & Preplant K bcd 4 50% Preplant N, 50% N Full Season Splits & Preplant K ab 5 50% Preplant N, 50% N Full Season Splits & Extra Preplant K bcd 6 50% Preplant N, 50% N Full Season Splits & Extra Split K cd 7 100% Preplant ESN & K bcd 8 100% Preplant ESN & Extra Preplant K bcd 9 50% Preplant ESN, 50 % N Early Season Splits & Preplant K bcd 10 50% Preplant ESN, 50% N Full Season Splits & Preplant K cd 11 50% Preplant ESN, 50% N Full Season Splits & Extra Preplant K cd 12 50% Preplant ESN, 50% N Full Season Splits & Extra Split K d LSD (P=.05) Standard Deviation CV 0.25 Treatment Prob(F) Page 5

12 Results: Fry Colour and Sugar End Fry colour became darker during storage (October to March) for all treatments. There tended to be fewer sugar end defects in March than in the October and January assessment dates. There were no differences in fry colour or sugar end defects between treatments. Character Rated Mean Fry Colour Sugar End % Rating Date 10-Oct-08 7-Jan Mar Oct-08 7-Jan Mar-09 Trt Treatment 1 100% Preplant N & K 0.03 a 0.38 a 0.60 a 0.00 a 7.50 a 0.00 a 2 100% Preplant N & Extra Preplant K 0.05 a 0.50 a 0.78 a 7.50 a 5.00 a 0.00 a 3 50% Preplant N, 50% N Early Season Splits & Preplant K 0.00 a 0.65 a 0.73 a 5.00 a 5.00 a 0.00 a 4 50% Preplant N, 50% N Full Season Splits & Preplant K 0.03 a 0.81 a 0.63 a 2.50 a 0.00 a 2.50 a 5 50% Preplant N, 50% N Full Season Splits & Extra Preplant K 0.08 a 0.13 a 0.54 a 0.00 a 2.50 a 5.00 a 6 50% Preplant N, 50% N Full Season Splits & Extra Split K 0.00 a 0.43 a 0.18 a 2.50 a 2.50 a 2.50 a 7 100% Preplant ESN & K 0.05 a 0.33 a 0.66 a 2.50 a 5.00 a 0.00 a 8 100% Preplant ESN & Extra Preplant K 0.08 a 0.33 a 0.50 a 7.50 a 2.50 a 0.00 a 9 50% Preplant ESN, 50 % N Early Season Splits & Preplant K 0.05 a 0.52 a 0.90 a 5.00 a 7.78 a 0.00 a 10 50% Preplant ESN, 50% N Full Season Splits & Preplant K 0.08 a 0.68 a 0.85 a 2.50 a 0.00 a 0.00 a 11 50% Preplant ESN, 50% N Full Season Splits & Extra Preplant K 0.00 a 0.18 a 0.52 a 5.00 a 5.00 a 0.00 a 12 50% Preplant ESN, 50% N Full Season Splits & Extra Split K 0.05 a 0.18 a 0.54 a 2.50 a 0.00 a 0.00 a LSD (P=.05) NSD NSD NSD NSD NSD NSD Standard Deviation CV Results: Marketable Yield (Table 4) Orthogonal contrasts (Table 4) and analysis of variance (Table 5) were used to analyze the data. The comments below are based on the orthogonal contrast. In 2008, both the source of nitrogen and the application method had an effect on yield. ESN/urea treatments produced higher yields than urea only treatments. In the urea only treatments applying nitrogen in early season splits 35 and 56 days after planting (DAP) produced higher yields than applying all nitrogen pre-plant or in full season splits 35, 56, 76 and 90 DAP. The application of potassium had no affect on yield. The ESN/urea treatments (#s 7-12) produced 63.8 more cwt/acre than the urea only treatments (#s 1-6). Applying urea as a single split application (#3) increased the yield by 80 cwt/acre when compared to all urea applied pre-plant (#1). Applying ESN pre-plant (#s 7&8) increased the yield by 80 cwt/acre when compared to applying all urea pre-plant (#s 1&2). Applying full season splits of ESN/urea (#s 10, 11 & 12) increased the yield by 27 cwt/acre compared to applying full season splits of urea (#s 4, 5 & 6). There was no difference in yield between applying urea pre-plant (#1) or in all splits (#4). There was no difference in the yield between the methods of nitrogen application in the ESN or ESN/urea treatments (#s 7-12). Page 6

13 There was no difference in yield between the rate and method of potassium application for the urea, ESN or ESN/urea treatments. Table 4 Effect of N and K on Yield treatment Description Trt # Marketable Yield cwt/acre Trt# Marketable Yield cwt/acre Difference All urea to all ESN/Urea treatments * Preplant urea to early season splits of urea * Preplant urea to ESN 1, , * All season splits of urea to all season splits of ESN/urea 4,5, ,11, * Preplant urea to full season splits of urea 1,2, 269 4,5, 285 NSD Preplant ESN to early season splits of ESN/Urea 7 9 NSD Preplant ESN to all season splits of ESN/urea 7,8 10,11 NSD Early season splits of urea to early splits of ESN/urea NSD Preplant recommended K to preplant extra split K 1,4 2,5 NSD Preplant recommended K to extra split K 4 6 NSD Extra preplant K to extra split K 5 6 NSD Preplant recommended K to preplant extra split K 7,10 8,11 NSD Preplant recommended K to extra split K NSD Extra preplant K to extra split K NSD * significant at 0.05 Table 5 Effect of N and K on Yield and Grade Character Rated Bonus % Undersize Marketable Total Rating Data Type YIELD YIELD YIELD YIELD Rating Unit % CWT CWT CWT 1 100% Preplant N & K 7.3 a 80.8 a a e 2 100% Preplant N & Extra Preplant K 17.6 a 60.0 a a de 3 50% Preplant N, 50% N Early Season Splits & Preplant K 10.9 a 69.5 a a a-d 4 50% Preplant N, 50% N Full Season Splits & Preplant K 10.9 a 85.3 a a cde 5 50% Preplant N, 50% N Full Season Splits & Extra Preplant K 14.9 a 66.8 a a b-e 6 50% Preplant N, 50% N Full Season Splits & Extra Split K 14.2 a 62.7 a a a-e 7 100% Preplant ESN & K 18.0 a 67.0 a a abc 8 100% Preplant ESN & Extra Preplant K 20.0 a 54.1 a a abc 9 50% Preplant ESN, 50 % N Early Season Splits & Preplant K 20.0 a 49.9 a a ab 10 50% Preplant ESN, 50% N Full Season Splits & Preplant K 27.3 a 49.2 a a a-d 11 50% Preplant ESN, 50% N Full Season Splits & Extra Preplant K 19.4 a 77.8 a a a 12 50% Preplant ESN, 50% N Full Season Splits & Extra Split K 21.0 a 66.0 a a ab LSD (P=.05) Standard Deviation CV Replicate F Replicate Prob(F) Treatment F Treatment Prob(F) Page 7

14 Field Survey to Determine Soil Factors Affecting Yield and Quality Funding: Keystone Potato Producers Association 50% Agricultural Sustainability Initiative 50% In Kind: Progress: Siemens Seed Potatoes Border Farms Ltd. Grenville Farms Limited Simplot Canada First Year Principal Investigators: Blair Geisel and Darin Gibson, Gaia Consulting Ltd. Introduction/Summary: A study funded by Keystone Potato Producers Association, Simplot Foods and McCain Foods Limited in 2005, 2006 and 2007 demonstrated that maintaining Available Soil Water (ASW) above 65% reduced plant stress and the incidence of sugar end disorder. Commercial potato producers in the Portage and Winkler production areas observed that maintaining ASW above 65% did not always reduce sugar end defect incidence to a level acceptable to the French fry processors. This lead researchers and producers to question if there were other field variables that were contributing to sugar ends. In 2008, an detailed survey of three 10 acre fields indicated that marketable yield, percent bonus and specific gravity were inversely correlated to salinity. The incidence of sugar end defect was positively correlated to the level of salinity. There was also a strong association between the 1:1 soil:water slurry analysis of soil and the Veris EC sensor methods of determining salinity. Objective: To determine the effect of soil variables (soil texture, salinity, elevation, soil-borne disease) on the incidence of sugar end defects yield and quality. Procedure: Plot locations: Variety: Site Selection 1 field in Portage la Prairie, 2 fields in Winkler (Figure 1, Figure 2 and Figure 3) Russet Burbank, Irrigated Two fields in the Winkler area were selected because of the presence of salinity. The field in the Portage area was selected because it was composed of a variety of soil textures along with large differences in elevation. A 10-acre area within each field was selected and 20 to 21 sites were sampled. Page 8

15 Sampling Two 10 foot samples were hand harvested at each of the sampling sites in a 10 acre area and graded to determine yield and quality. Ten 0-6 inch soil samples were also collected at each sampling site and analyzed for Verticillium dahlia and salinity (1:1 soil:water slurry). Specific Gravity Analysis: Specific gravity (SG) was determined by comparing the weight of a 4.5 kg tuber sample in air and in water. Fry Colour Analysis: The centre ½ inch fry strip from 10 tubers per plot was fried for 2 minutes 30 seconds in vegetable oil at 375 F. Fry colour was determined using the USDA scale, which ranges from "0" (light colour) to "4" (dark colour). Sugar End Analysis: If less than 1/3 of the French fry is darker than the remainder of the fry by 2 colour gradients on the USDA fry colour scale, it is defined as a sugar end. The fry colour is determined by assessing the remaining 2/3 of the fry. However, if the dark end affects more than 1/3 of the entire fry, colour is determined by assessing the dark end. Statistical Analysis: Correlation analysis was conducted between the X and Y variables in Table 6. The correlation coefficient is a statistical measure of the interdependence of two variables. Fundamentally, the value indicates how much of a change in one variable is explained by a change in another. Correlations coefficients range from -1.0 to +1.0 in value. A correlation coefficient of 1.0 indicates a perfect positive relationship in which high values of one variable are related perfectly to high values in the other variable, and conversely, low values on one variable are perfectly related to low values on the other variable. A correlation coefficient of 0.0 indicates no relationship between the two variables. That is, one cannot use the scores on one variable to tell anything about the scores on the second variable. A correlation coefficient of -1.0 indicates a perfect negative relationship in which high values of one variable are related perfectly to low values in the other variables, and conversely, low values in one variable are perfectly related to high values on the other variable. A correlation of 0.9 may be very low if one is verifying a physical law using high-quality instruments and few complicating factors, but may be regarded as very high in the agricultural sciences where there may be a greater contribution from complicating factors. The value of the correlation coefficient r squared is typically taken as the percent of variation in one variable explained by the other variable. Page 9

16 Table 6 Data collected in field survey. Variable X Verticillium dahlia VPPG Salinity Elevation Soil Texture Variable Y Total Yield Marketable Yield Bonus >10 oz Hollow Heart Specific Gravity Fry Colour Sugar End Figure 1 Veris salinity map of Siemens Seed Potatoes field showing sampling sites Page 10

17 Figure 2 Veris salinity map of Border Farms Limited field showing sampling sites Figure 3 Varis elevation map of Grenville Farms Limited field showing sampling sites Page 11

18 Results: Salinity Surface salinity varied from , and mmhos/cm at the Border, Siemens and Grenville locations respectively. Salinity readings greater than 1.0 mmhos/cm will affect potato yield and quality. Below are the results of correlations between salinity readings and Y-variables (Table 7). There was no correlation between salinity and the Y-variables at Grenville with the exception of specific gravity because there was only a small variation in salinity readings and readings were generally below the impact threshold of 1.0 mmhos/cm. At the Border and Siemens locations, were there were higher salinity values and a wider range of values. Marketable yield, percent bonus and specific gravity were inversely correlated to salinity. Sugar end defect was positively correlated to the level of salinity. At the Grenville location, marketable yield varied from cwt/acre. None of the factors measured in this study including salinity affected yield. Marketable yield varied from and cwt/acre at the Border and Siemens locations respectively. At these locations, significant yield and revenue losses resulted from salinity. The relationship between salinity and yield was strong; and for the Border and Siemens locations respectively. Sugar end defect varied from and 0-40 percent at the Border and Siemens locations respectively. Increasing salinity contributed to sugar end defect at these locations. Verticillium propagules per gram of soil (VPPG) were negatively correlated to salinity. There is a strong correlation between soil salinity values bases on soil analysis (1:1 soil:water slurry) and Veris readings. This is especially true at the Border and Siemens locations. Page 12

19 Table 7 Correlation of salinity to potato yield and quality and soil variables Y Factor Marketable Yield NSD Bonus >10 oz NSD Specific Gravity Hollow Heart NSD NSD NSD Fry Colour NSD NSD NSD Sugar End NSD VPPG NSD NSD Veris Salinity Reading Significant at P = Significant at P = Significant at P = 0.10 Border Siemens Grenville Combined Results: Verticillium dahlia The number of VPPG varied from 14-86, 4-90 and 4-68 at the Border, Siemens and Grenville locations respectively. Levels greater than 10 will affect yield and quality. There were only 5 of 61 soil samples with readings less than 10 VPPG. The correlation analysis indicated that the number of Verticillium propagules per gram of soil was poorly correlated with the Y variable. This does not mean that Verticillium does not affect these variables, but very few sample sites had propagule values below the disease threshold. Below are the results of correlations between Verticillium dahlia readings and Y-variables (Table 8). The concentration of Verticillium wilt in the soil correlated negatively with marketable yield at the Border site and positively at the Siemens site. The positive correlation at the Siemens site was due the negative association between salinity and disease levels (Table 7). The concentration of disease (VPPG) in the soil is lower as salinity readings increase. Since salinity has a greater impact on yield than Verticillium dahlia, the yield is lower in the saline sampling sites where disease levels are low and higher in the sampling sites where salinity is lower and disease levels are higher. The negative correlation between disease levels (VPPG) and salinity results in a positive correlation between disease levels and marketable yield. The same relationship applies to percent bonus and specific gravity at the Siemens site. Page 13

20 Table 8 Correlation of the concentration of Verticillium dahlia (VPPG) in the soil to potato yield and quality Y Factor Marketable Yield NSD NSD Bonus >10 oz NSD NSD NSD Specific Gravity NSD NSD Hollow Heart NSD NSD Fry Colour NSD Sugar End NSD NSD NSD Significant at P = Significant at P = Significant at P = 0.10 Border Siemens Grenville Combined Results: Elevation (Table 9) The elevation varied by 2.1, 3.2 and 5.2 feet at the Border, Siemens and Grenville 10-acre locations respectively. An analysis of the combined data indicates that yield, percent bonus, fry colour and percent sugar end were negatively correlated with elevation and specific gravity was positively correlated with elevation. This may be due to differences in drainage, soil texture and moisture status of the soil at various elevations. Higher areas might be moisture deficient resulting in a lower yield and reduced size. This same condition would increase maturity resulting in lighter fry colour and increased specific gravity. The relationship between elevation and these variables is weak. There is a weak negative correlation between elevation and salinity at Border and Siemens. There is a positive correlation between elevation and disease levels at Siemens and Grenville locations. This relationship is strongest at the Grenville location. As discussed earlier, there was no relationship between concentration of Verticillium wilt in the soil and yield because at a majority of the sampling sites the fungus levels exceeded the disease threshold. Page 14

21 Table 9 Correlation of elevation to potato yield and quality and soil variables Y Factor Border Siemens Grenville Combined Marketable Yield NSD NSD NSD Bonus >10 oz NSD NSD Specific Gravity NSD NSD Hollow Heart NSD NSD Fry Colour NSD NSD Sugar End NSD NSD NSD Salinity NSD NSD VPPG NSD Significant at P = Significant at P = Significant at P = 0.10 Page 15

22 Effect of Hilling Type and Straw Mulch on Potato Quality Funding : Keystone Potato Producers Association 100% Principal Investigators: Blair Geisel and Darin Gibson, Gaia Consulting Ltd. Curtis Cavers, CMCDC Portage la Prairie, MB Objective: To determine the effect of hill shape and mulching on the incidence of sugar end defect in Russet Burbank Procedure: Plot size: 4 rows by 12 m (Assessments conducted on 2 centre rows) Trial design: RCB 4 replicates Plot location: CMCDC Portage Crop: Potatoes Variety: Russet Burbank Row spacing: 1 metre Soil type: Neuhorst clay loam Planting date: May 23 Treatments: 1. Disc Hiller (wide, low hill) pre-emergence, no mulch 2. Disc Hiller (wide, low hill) pre-emergence, with straw mulch 3. Power hill pre-emergence (narrow and high peaked hill) no mulch 4. Power hill pre-emergence (narrow and high peaked hill) with straw mulch 5. Disc Hiller (wide, low hill) post-emergence, no mulch 6. Disc Hiller (wide, low hill) post-emergence, with straw mulch Hilling dates: Treatment 1 and 2: June 3 Treatment 3 and 4: June 6 Treatment 5 and 6: July 2 Mulch spreading: Treatments 2 and 4: June 6 Treatment 6: July 2 A thin layer of straw was spread by hand and covered approximately 85-90% of the ground surface. Specific Gravity Analysis: Specific gravity (SG) was determined by comparing the weight of a 4.5 kg tuber sample in air and in water. Fry Colour Analysis: The centre ½ inch fry strip from 10 tubers per plot was fried for 2 minutes Page 16

23 30 seconds in vegetable oil at 375 F. Fry colour was determined using the USDA scale, which ranges from "0" (light colour) to "4" (dark colour). Sugar End Analysis: If less than 1/3 of the French fry is darker than the remainder of the fry by 2 colour gradients on the USDA fry colour scale, it is defined as a sugar end. The fry colour is determined by assessing the remaining 2/3 of the fry. However, if the dark end affects more than 1/3 of the entire fry, colour is determined by assessing the dark end. Results Soil Temperature: Hobo temperature data loggers were installed 15 cm below the surface in the centre of the hill on June 18 th (Figure 4 - Figure 8). Straw mulch tended to keep the hill cooler during the tuber initiation period, particularly for the pre-emergence hilling treatments (Figure 4, Figure 5). There was less of an effect on the post-emergent treatments (Figure 6). Figure 4. Effect of mulch on hill temperature (15 cm depth) disc hiller, pre-emergence. Page 17

24 Figure 5. Effect of mulch on hill temperature (15 cm depth) power hiller, pre-emergence. Figure 6. Effect of mulch on hill temperature (15 cm depth) disc hiller, post-emergence. Page 18

25 Power hilled treatments had slightly higher hill temperature on average compared to disc hilling (Figure 7). Hilling method was not as great an influence as the presence of straw. Figure 7. Effect of hilling method on hill temperature (15 cm depth). Timing of disc hilling did not have much influence on hill temperature (Figure 8). Figure 8. Effect of hilling timing on hill temperature (15 cm depth). Page 19

26 Results Soil Moisture: Soil moisture was monitored in the first rep of the trial. Table 10 shows irrometer readings on Aug 5 which are typical of the readings through July and August. Soil moisture at an 18 depth appears to be improved with mulch. Table 10. Effect of hilling and mulch treatments on soil moisture. Irrometer Aug 5 Treatment 12" 18" 1 Disc hill pre-emerg, no mulch Disc hill pre-emerg, mulch Power hill, no mulch Power hill, mulch Disc hill post-emerg, no mulch Disc hill post-emerg, mulch Results Yield and Grade: There were no significant differences between treatments for yield or grade (Table 11). The trial was somewhat less vigorous throughout the season and average yield was approximately 60 cwt lower as compared to nearby yield trials. Later planting date and seed source are two variables that may have contributed to this difference. Table 11. Effect of hilling and mulch treatments on potato yield and grade. Yield (cwt) Undersize Marketable Bonus Treatment (<2") (>2") Total (>10 oz) 1 Disc hill pre-emerg, no mulch 40.6 a a a 28.1 a 2 Disc hill pre-emerg, mulch 49.7 a a a 19.0 a 3 Power hill, no mulch 35.6 a a a 25.6 a 4 Power hill, mulch 52.2 a a a 18.2 a 5 Disc hill post-emerg, no mulch 41.9 a a a 19.2 a 6 Disc hill post-emerg, mulch 42.4 a a a 23.5 a LSD (P=.05) CV Treatment Prob(F) Page 20

27 Results Hollowheart: There were no statistical differences between treatments for incidence of hollowheart when measured by the percentage of tubers expressing the defect (Table 12). When expressed by the percentage of tuber weight expressing hollowheart, significant differences are detected. The most notable differences are: higher incidence of hollowheart in pre-emergent hilling without mulch (treatment 1) compared to post-emergent hilling without mulch (treatment 5); significantly higher incidence of hollowheart in power hilling treatment without mulch (treatment 3) compared to power hilling with mulch (treatment 4). Table 12. Effect of hilling and mulch treatments on incidence of hollowheart. Hollow Heart Incidence Treatment % by Number % by Weight 1 Disc hill pre-emerg, no mulch 15.1 a 26.6 a 2 Disc hill pre-emerg, mulch 12.5 a 18.1 abc 3 Power hill, no mulch 11.8 a 21.7 ab 4 Power hill, mulch 2.3 a 4.0 c 5 Disc hill post-emerg, no mulch 2.7 a 3.5 c 6 Disc hill post-emerg, mulch 5.2 a 8.5 bc LSD (P=.05) CV Treatment Prob(F) Results French fry quality: No differences were found between treatments for specific gravity, fry colour or sugar ends (Table 13). Table 13. Effect of hilling and mulch treatments on quality. Oct Jan 8 09 Fry Sugar Fry Sugar Colour Ends Colour Ends Treatment (0-4) (%) (0-4) (%) (0-4) (%) 1 Disc hill pre-emerg, no mulch 0.87 a 12.1 a 0.95 a 12.5 a 0.73 a 21.1 a 2 Disc hill pre-emerg, mulch 0.58 a 17.1 a 0.31 a 12.3 a 0.18 a 22.5 a 3 Power hill, no mulch 0.63 a 14.6 a 0.70 a 20.0 a 0.64 a 16.8 a 4 Power hill, mulch 0.30 a 15.0 a 0.35 a 17.5 a 0.53 a 25.0 a 5 Disc hill post-emerg, no mulch 0.75 a 14.6 a 0.88 a 15.0 a 0.76 a 7.3 a 6 Disc hill post-emerg, mulch 0.58 a 4.8 a 0.68 a 10.0 a 0.49 a 21.6 a LSD (P=.05) CV Treatment Prob(F) Mar Fry Colour Sugar Ends Page 21

28 Phosphorus Management for Irrigated Russet Burbank Potato Production Funding: Keystone Vegetable Producers 16.6% Simplot Canada 16.6% McCain Foods 16.7% ARDI 50% In kind contribution of land and irrigation was provided by Don Dickson, CMCDC Portage, Beaver Creek Farms and Rick and Derrik Fiskel Progress: Second Year Principal Investigators: Blair Geisel and Darin Gibson, Gaia Consulting Ltd. Introduction: Due to reactivity with soil, P is often in a form less available to crops. Standards for what are adequate levels of P in the soil and in potato petioles in Manitoba are not well defined. The impact of phosphorus as a non-point source contaminant has increasingly become an issue in agriculture in recent years. Concerns over water quality are a driving force in the desire to make more efficient use of P. In 2007 and 2008, 4 trials comparing different phosphorus rates and application methods were conducted in the Portage and Carberry production areas. The sites had residual phosphorus concentrations in the soil ranging from 8-32 ppm (Olsen). At all four locations, the petiole phosphate concentrations were sufficient to maximize yield. Petiole P concentrations were between % early season, % mid-season and % late season (data not shown). A response in petiole P concentration to additional phosphorus fertilizer was measured in both the side-banded and broadcast applications at three of the four sites. A yield response occurred at 2 of the 4 sites, but only in the side-banded treatments. There was no yield response at rates higher than 40 lbs P/acre applied as a sideband. The addition of phosphorus had no effect on tuber size (bonus tuber >10 oz.), specific gravity, fry colour or the incidence of hollow heart or sugar end defect. The yield response to phosphorus occurred at the two sites with the highest residual P concentration in the soil (18 and 32 ppm). The inconsistent response to P fertilization is explained in a paper titled Agroeconomics of Phosphate Fertilizer in Manitoba by Rigas E. Karamanos of the Western Cooperative Fertilizers Limited. Soil testing has been a pillar in deriving fertilizer recommendations. However, one has to consider that existing soil testing databases were developed based on the Law of Minimum and for that only soils that were not previously fertilized were used. Nowadays it is virtually impossible to find such soils and the behaviour of P in a soil is quite different once the soil has been fertilized for a prolonged period of time. A compilation of yield data from 155 experiments showed that when soil test levels were less than 10 lb P/acre (deficient), not all crops responded to P fertilization in all cases. At Page 22

29 the same time when soil test levels were greater than 30 lb P/acre (sufficient) still a number of crops were responding to high P levels. Although the frequency of responses was higher at lower soil test P levels, there were no clear trends, which would suggest that response to phosphate fertilizer is indeed affected by factors other than the soil test level and in any event application of P would be necessary almost at any soil test level. A long-term (23-year) study showed that elimination of P fertilization results in immediate yield losses. Given the high levels of P that have been built up in Manitoba soils and the low correlation of yield response to soil test P, the best strategy is to apply maintenance amounts of P to replace what is removed by the crop. Potatoes require 0.14 lbs P2O5/cwt. Objectives: 1. Determine the effect of phosphorus placement on potato yield and quality. 2. Determine the effect of phosphorus rate on potato yield and quality. 3. Determine the effect of coated phosphorus product on efficient use of phosphorus, potato yield and quality. 4. Determine critical soil and tissue levels at which a response to P can be expected. 5. Improve the efficiency of phosphorus use. Procedure: Plot size: 4 rows by 12 m (Assessments conducted on 2 centre rows) Trial design: RCB 4 replicates Site Description Table 14 Table 14 Site Description Year Location Soil type Residual P (ppm) 2007 Portage Clay Loam Carberry Loamy Sand Portage Fine Sandy Loam Carberry Loamy Sand Ph Crop: Variety: Seed spacing: Row spacing: Potatoes Russet Burbank 13.5 inches 1 metre Treatments: Table 15 Page 23

30 Table 15 List of fertilizer treatments Rate Trt # Method Product (lbs/ac) 1 Untreated Check 2 Side band Mono Ammonium Phosphate (MAP) 20 lbs P Side band Mono Ammonium Phosphate (MAP) 40 lbs P Side band Mono Ammonium Phosphate (MAP) 80 lbs P Side band Mono Ammonium Phosphate (MAP) 160 lbs P Side band Avail Coated MAP 40 lbs P Broadcast Mono Ammonium Phosphate (MAP) 20 lbs P Broadcast Mono Ammonium Phosphate (MAP) 40 lbs P Broadcast Mono Ammonium Phosphate (MAP) 80 lbs P Broadcast Mono Ammonium Phosphate (MAP) 160 lbs P Results: Yield (Table 16) A yield response to additional phosphorus only occurred at two of the four sites (2008 Carberry and Portage sites) and only in the side-banded treatments (#s 2-5). There was no yield response at rates higher than 40 lbs P/acre applied as a sideband (#s 3-5). There was no response to additional phosphorus when broadcast and incorporated (#s 7-10). Avail coated MAP applied as a sideband at 40 lbs P/acre (#6) produced a greater yield than the check (#1). There was no difference in yield between MAP at 40 lbs P/acre (#6) and Avail coated MAP at 40 lbs P/acre (#3). The pre-plant residual soil P concentration at the sites which responded to the addition of side banded phosphorus fertilizer was 18 and 32 ppm. Page 24

31 Table 16 Effect of phosphorus rate and method of application on potato yield Yield cwt/acre Trt No. <2" Marketable tubers >2" Total (Undersize + Marketable) cd b a b de b a b d b a e b a ab a abc a ab a ab a a a a a ab a abc a bc a cde a abc a bcde a abc a bcde a abc a abcd a Prob no value CV% LSD = 0.05 NSD NSD NSD NSD NSD LSD = 0.10 NSD NSD 22.5 NSD 19.9 Means within a column followed by the same letter are not significantly different Results: Quality (Table 17) The addition of phosphorus had no effect on tuber size (bonus tuber >10 oz.), specific gravity, fry colour or the incidence of hollow heart or sugar end defect. Table 17 Effect of phosphorus rate and method of application on potato quality Trt No. Bonus >10 oz. Hollow Heart % by No. Hollow Heart % by wt Specific Gravity Mean USDA Fry colour Sugar End % Prob no value no value no value no value CV% LSD = 0.05 NSD NSD NSD NSD NSD NSD LSD = 0.10 NSD NSD NSD NSD NSD NSD Page 25

32 Screening of Verticillium Wilt Resistant Potato Varieties Funding: Keystone Vegetable Producers 16.6% Simplot Canada 16.6% McCain Foods 16.7% Agricultural Research Development Initiative 50% Progress: Fifth Year Principal Investigators: Blair Geisel and Darin Gibson, Gaia Consulting Ltd. Introduction: A six station-year trial studying the resistance of French fry processing varieties to Verticillium dahlia was conducted between 2004 and Over the 5 years, 10 varieties (Russet Burbank, Shepody, Umatilla, Ranger Russet, Prospect, Aluras, Premier Russet, Summit Russet, Defender and Bannock Russet) were entered in the trial. Alturas, Summit Russet, and Defender were dropped from the study because of poor performance. Premier Russet was only included in The 2008 data indicated that Premier Russet produced high yields, very high specific gravity, high incidence of hollow heart, good fry colour and low incidence of sugar end defect. Bannock was only entered in 4 of the possible 6 stationyears due to seed availability. This report includes the results from 4 station-years of data (2004, 2007 and 2 sites from 2008) for six of the 10 varieties (Russet Burbank, Shepody, Umatilla, Ranger Russet, Prospect and Bannock Russet). Data from 2005 were not used because the site received excessive precipitation and many of the plots were destroyed. Data from 2006 were not included because Bannock Russet was not entered in the trial. A summary of the results are listed in Table 18. Table 18 Summary of results from 4 station-years of study Variety # Variety Name Marketable Yield >2" Specific Gravity Hollow Heart % Vascular Discolour ation % Mean Fry Colour 1 Russet Burbank poor excellent good high low high 2 Shepody poor good good high low high 3 Umatilla Russet good good good low medium low 4 Ranger Russet very good poor good high low low 5 Prospect excellent excellent good low low low 6 Bannock Russet good excellent poor low low low Sugar end % Objective: To compare the yield and quality of standard French fry processing varieties to recently released Verticillium wilt resistant varieties. Page 26

33 Procedure: Plot size: 2 rows by 12 m. Trial design: RCB with 4 replicates. Plot locations: 3 sites in Portage la Prairie (2 rain-fed and 1 irrigated) and 1 irrigated site in Winkler. Disease levels ranged from 28 to 522 verticillium propagules per gram of soil (VPPG). Row spacing: 1 metre Seed spacing: Table 19 Planting Date: 2004-June 4 th, 2007-May 17 th and 2008 May 13 th Treatments: Table 19 Table 19. Variety list. Processed Var # Variety Name Seed Spacing (cm) Verticillium Resistance Maturity US Canada 1 Russet Burbank 38 Susceptible Late to very late Yes Yes 2 Shepody 30 Susceptible Early Yes Yes 3 Umatilla Russet 38 Moderately Susceptible Mid-season to late Yes Yes 4 Ranger Russet 30 Moderately Resistant Medium-late Yes Yes 5 Prospect 30 Resistant Mid-season Yes Yes 6 Bannock Russet 30 Resistant Late Yes No Specific Gravity Analysis: Specific gravity (SG) was determined by comparing the weight of a 4.5 kg tuber sample in air and in water. Fry Colour Analysis: The centre ½ inch fry strip from 10 tubers per plot was fried for 2 minutes 30 seconds in vegetable oil at 375 F. Fry colour was determined using the USDA scale, which ranges from "0" (light colour) to "4" (dark colour). Sugar End Analysis: If less than 1/3 of the French fry is darker than the remainder of the fry by 2 colour gradients on the USDA fry colour scale, it is defined as a sugar end. The fry colour is determined by assessing the remaining 2/3 of the fry. However, if the dark end affects more than 1/3 of the entire fry, colour is determined by assessing the dark end. Page 27

34 Statistical Analysis: An ANOVA (analysis of variance) was performed on the combined data from 5 stationyears of research. Mean separation was determined using the least significant difference (LSD) test. Results Yield and Size (Table 20): All resistant varieties (#s 3-6) produced a greater yield than the standard varieties (#s 1 and 2). Of the resistant varieties (#s 3-6) Umatilla #3 produced the lowest yield. Umatilla produced a high total yield with a smaller tuber profile resulting in more grade out and lower marketable yield than the other varieties. Evidence of this is the high undersize yield and low percent bonus. A wider in-row seed spacing might improve the marketable yield of this variety. Ranger Russet (#4) produced a yield similar to Bannock Russet (#6) and Prospect (#5). In this study, Prospect (#5) and Ranger (#4) produced the highest yields. An analysis of 5 station-years of data comparing varieties #s 1-5 (not included in this report) indicated that Prospect produced a higher yield than Ranger (p=0.05). Table 20 Yield and size Variety # Variety Name Yield cwt/acre Undersize <2" Marketable >2" Total Bonus % 2 Shepody 28.5 b d c 24.1 b 1 Russet Burbank 49.3 a d b 16.4 c 3 Umatilla Russet 54.7 a c a 16.8 c 6 Bannock Russet 23.6 bc b ab 33.4 a 4 Ranger Russet 27.1 b ab a 33.5 a 5 Prospect 18.2 c a a 37.3 a Prob CV % LSD Page 28

35 Results Quality (Table 21): Specific Gravity A narrow range of specific gravity is suitable for French fry processing. The following method of ranking specific gravity was developed by Washing State University. Ranking goes from 0 (poor quality) to 5 (highest quality) according to the following categories 5= = and = and = and = and or higher 0 = or lower Russet Burbank, Bannock Russet and Prospect produced specific gravity between and 1.089, which is ideal for French fry processing. Shepody and Umatilla produced good specific gravity ( ), which was somewhat higher than the ideal range for French fry processing. Ranger Russet produced a specific gravity of 1.100, which is unsuitable for French fry processing. Hollow Heart The incidence of hollow heart was low with the exception of Bannock Russet. Vascular Discolouration Vascular necrosis, also known as stem-end browning, stem-end discoloration or necrosis, vascular discoloration or browning and phloem necrosis is an internal brown discoloration of tuber tissue in the region of the vascular ring, which can be caused by several environmental conditions and diseases including Verticillium wilt. The disorder is characterized by a light tan to reddish brown speckling or a dark brown streaking in the vascular tissue. The speckling or streaking usually extends to about a half inch from the attachment point, but in severe cases may extend in the vascular system the length of the tuber. Bannock Russet, Prospect and Umatilla had the lowest incidence of vascular discolouration. Ranger Russet, a variety, which exhibits resistance to Verticillium wilt had a high incidence of vascular discolouration. The standard varieties Shepody #2 and Russet Burbank #1 had the highest incidence of vascular discolouration. Page 29