Progress Report to the Maine Potato Board Research Subcommittee

January 19, 2005

 

Project Title:

 

Potato Management Studies with Emphasis on Nutrient Management, Supplemental Irrigation, and Crop Rotation

 

Investigators:

 

Gregory A. Porter and Paul C. Ocaya;  Department of Plant, Soil & Environmental Sciences. University of Maine, Orono.

 

Executive Summary

 

            Eight potato management experiments and four alternate crop experiments were supported by Maine Potato Board research funds during the 2004 growing season.  The project will result in new tissue testing tools and recommendations for micro-nutrient and potassium management, improved information on how to best manage new and established potato varieties, recommendations for crop rotations that help improve the profitability, and recommendations for barley, milling wheat, and canola production.  The micro-nutrient and potassium timing multi-year experiments were completed during 2004.  As specific studies in the project are completed the results will be presented to the industry and published in various popular, technical, and scientific outlets for use by the industry and other decision makers.  

           

            The goal of our potassium fertilization experiments is to improve Maine’s soil, tissue testing, and fertilization recommendations for potatoes.   Results obtained during 2004 will allow us to complete the revision of these recommendations.  Yield response to potash varies with the soil test potassium levels, weather conditions, and other management inputs.  Our data shows that potash fertilizer increases tuber potassium, calcium, and magnesium concentrations.  It also increases potassium concentrations of the foliage, while decreasing the foliage calcium and magnesium concentrations.   Potash fertilizer tends to decrease incidence of internal tuber defects (hollow heart, brown center, and blackspot bruise), improve fry color, and improve fresh market quality, while also decreasing specific gravity.  The depression of specific gravity is not usually of great concern with very high specific gravity varieties grown for chipping (e.g. Snowden and Atlantic) or for seed and fresh markets, but it can be a major concern for moderate specific gravity processing varieties like Russet Burbank and Shepody.   Each 100 increment of potash decreases Russet Burbank specific gravity by about 3.5 points.  Effects of potash application timing were generally small; however, late-applied potash had less effect on specific gravity than the earlier applications suggesting that the late-applied K is not taken up as efficiently. 

 

            Supplemental irrigation did not significantly affect yields in our 2004 Russet Burbank experiment.   Rainfall was abundant and the lack of a yield response was not surprising.  Irrigation did not affect U.S. #1 yields or tuber size during 2004; however, irrigation increased the percentage hollow large-sized tubers (42% vs 22%) and decreased specific gravity (1.078 vs 1.089) in this study.   Our data show that supplemental irrigation provides beneficial yield and quality increases in about 7 out of 10 years in central Aroostook County.

 

            A three-year micronutrient fertilization study was completed during 2004 to better understand the uptake efficiency of corrective boron and zinc applications.  Soil applied treatments were compared to early, mid-season, and late-season foliar treatments.   Boron and zinc did not significantly affect Russet Burbank yield relative to the check plots during 2004.     There were no major difference in yields or quality among the timing treatments (banded, tuber initiation, early bulking, versus mid-bulking).  Our studies since 1994, provide convincing evidence for continued use of boron fertilizer in our production system.  The evidence for zinc’s benefits is less consistent and applications should be based on soil tests for individual fields.  The final results of the project and conclusions about the timing treatments will be reported to the industry once all laboratory plant and soil analyses have been received.  

 

            A crop rotation experiment using Superior has demonstrated that US#1 yields over a 7-year period are highest (262 to 265 cwt/A) in a 3-year rotation or a 2-year rotation that received a single-year (1996) application of papermill sludge and compost.   Two-year rotations with either oats or vegetables were equal (245 to 247 cwt/A) and the continuous potato treatment was worst (217 cwt/A).  The goal of this very successful experiment is to study the effects of this amendment program and the crop rotations on both the soil and crop over time. The results show that the low organic matter inputs and intensive tillage of a potato crop quickly decrease soil structure and organic matter.  Amendment and rotation treatments have strongly affected soil properties; however, the results clearly show the seasonal fluctuation in yields result primarily from erratic rainfall (e.g. 1999, 2001, and 2002 were dry years with low yields) and that soil improvement approaches (crop rotation and soil amendment) cannot substitute for an adequate water supply.   Another crop rotation experiment using Shepody is looking at the effects of two-year rotations with oats, oats underseeded with Italian ryegrass, peas/clover, and a oat/pea/vetch green manure.  Short-term effects have been primarily on N fertility.  AF1753-16 continues to show promise as an alternative to Shepody for french fry processing.  It is higher yielding in virtually all side-by-side comparisons of the two varieties, has larger tuber size, higher specific gravity, and less hollow heart.   AF1753-16 does not show a strong yield response to nitrogen fertilizer.   A nitrogen and potassium response study was conducted for a promising, dual-purpose russet (AF1808-18).   This variety showed a strong yield and quality response to increasing rates of N fertility.  The major problem with AF1808-18 to date has been sunburn and the incidence of this defect was not greatly affected by fertility program.

 

             Two malting barley variety trials and a spring milling wheat variety trial were conducted during 2004.   Garnet and Conlon are promising two-row malting barley varieties.  Lacey and B1602 have been the top-performing, six-row malting barley varieties.   Information from these trials should help the industry maximize the value of its small grain rotation crops. 

 

Project Objectives:

 

            1.         Optimize management practices for Maine potatoes:

1a) Improve potassium fertilization recommendations by determining the interaction between water availability and the timing of potassium uptake from supplemental fertilizer applications.

                        1b) Study timing responses to boron and zinc application

                        1c) Develop information on the herbicide tolerance of new potato varieties

 

            2.         Study the effects of nutrient (nitrogen and potassium) and storage management on          tuber sugars (glucose and sucrose), bruise susceptibility, and processing quality. 

 

            3.         Develop rotation crop recommendations for potato production systems:

3a) Study potato responses to crop rotation and determine the effects of crop rotation and soil amendment use on soil properties.  

                        3b) Conduct malting barley and spring wheat variety trials

                        3c) Conduct other rotation crop research as needed

 

Grant Received for 2004 Growing Season:

 

            $24,000

           

Accomplishments to Date:

 

            Eight potato management experiments and four alternate crop experiments were supported by Maine Potato Board research funds during the 2004 growing season.  The project will result in new tissue testing tools and recommendations for micro-nutrient and potassium management, improved information on how to best manage new and established potato varieties, recommendations for crop rotations that help improve the profitability, and recommendations for barley, milling wheat, and canola production.  Several of the multi-year experiments were completed during 2004.  As specific studies within the project are completed the results will be presented to the industry and published in various popular, technical, and scientific outlets for use by the industry and other decision makers.  

 

            Potassium Fertilization and Supplemental Irrigation Experiments.  Supplemental irrigation did not significantly affect yields in our 2004 Russet Burbank experiment (Table 1).   Rainfall was abundant and the lack of a yield response was not surprising.  Irrigation did not affect U.S. #1 yields or tuber size during 2004; however, irrigation increased the percentage hollow large-sized tubers (42% vs 22%) and decreased specific gravity (1.078 vs 1.089) in this study (Tables 1 and 2).   Response to supplemental irrigation depends largely on the weather conditions and, like the 1992 growing season, the 2004 growing season was not a year that required supplemental irrigation.  Our long-term weather data suggest that supplemental irrigation is beneficial in about 7 out of every 10 years in central Aroostook County.

 

            The goal of our potassium fertilization experiments is to improve Maine’s soil, tissue testing, and fertilization recommendations for potatoes.   Results obtained during 2004 should allow us to complete the revision of the soil and tissue testing recommendations.  Our data shows that potash fertilizer increases tuber potassium, calcium, and magnesium levels (Table 3).  It also increases potassium concentrations of the foliage, while decreasing the foliage calcium and magnesium concentrations.   Potash fertilizer tends to improve fry color and decrease incidence of internal tuber defects (hollow heart, brown center, and blackspot bruise), while also decreasing specific gravity (Tables 1 to 3).  The depression of specific gravity is not usually of great concern with very high specific gravity varieties grown for chipping (e.g. Snowden and Atlantic), but it can be a major concern for moderate specific gravity processing varieties like Russet Burbank and Shepody.  Yield response to potash varies with the soil test potassium levels, weather conditions, and other management inputs.  During 2004, we observed a weak yield response to increasing potash rate under non-irrigated conditions (+53 cwt/A, pr>F = .06) over the range of rates used in the study (0 to 300 lbs/A, Table 1).   This effect was not observed in the irrigated plots.  Potash tended to increase tuber size and decrease hollow heart incidence (Tables 1 and 2).   Each 100 increment of potash decreased Russet Burbank specific gravity by 3.5 points (Table 1) .  This specific gravity effect is similar to the results obtained during 2003.   These data confirm our recent studies which point to potash fertilizer’s key effects on tuber internal quality and specific gravity.  Effects of potash application timing were generally small and non-significant during 2004; however, late-applied potash had less effect on specific gravity than the earlier applications suggesting that the late-applied K is not taken up as efficiently as earlier-applied K (Tables 1 and 2).   We will be able to complete our potash fertility studies and get our recommendations to the potato industry as laboratory data becomes available this winter.

           

            Micronutrient Uptake Experiment.  A three-year micronutrient fertilization study was completed during 2004 to better understand the uptake efficiency of corrective boron and zinc applications.  Soil applied treatments were compared to early, mid-season, and late-season foliar treatments.   Boron and zinc did not significantly affect Russet Burbank yield relative to the check plots during 2004 (Table 4).  There were no major difference in yields or quality among the timing treatments (banded, tuber initiation, early bulking, versus mid-bulking, Tables 4 and 5).  The results of this three-year experiment (2002 to 2004) differed somewhat from the results obtained prior to 2002.  In total, our studies provide convincing evidence for continued use of boron fertilizer in our production system.  The evidence for zinc’s benefits is less consistent.  The final results of the project and conclusions about the timing treatments will be reported to the industry once all laboratory analyses for plant tissue nutrient levels has been received.  Additional experimental details are available upon request.

 

     Crop Rotation Studies:    Our studies on the effects of crop rotation and soil management continued during 2004.   One experiment (Table 6) using Superior and no irrigation demonstrates that mean US#1 yields over a 8-year period are highest (265 to 262 cwt/A) in a 3-year rotation or a 2-year rotation that received a single-year (1996) application of papermill sludge and compost.   The two-year rotations with either oats or vegetables were equal (245 to 247 cwt/A) and the continuous potato treatment was worst (217 cwt/A).    The goal of this very successful experiment is to study the effects of this amendment program and the crop rotations on both the soil and crop over time.  We have studied soil fertility, organic matter, bulk density, and water stable aggregates in this experiment because one major set of crop rotation effects is on soil properties (data not shown).  The results show that the low organic matter inputs and intensive tillage of a potato crop quickly decrease soil structure and organic matter.  Surprisingly, extending the rotation to three years and including one year of timothy/clover (which adds organic matter and provides a full year without tillage) has quickly improved soil organic matter and structure.  The amendment treatment quickly enhanced soil properties, but its effects have declined over time as expected.  Table 5 summarizes that potato yield response from 1996-2004.  The results clearly show the seasonal fluctuation in yields that results primarily from erratic rainfall (e.g. 1999, 2001, and 2002 were dry years with low yields) and that soil improvement approaches (crop rotation and soil amendment) cannot substitute for an adequate water supply.   The soil management approaches clearly have more subtle effects on productivity than rainfall patterns; however, differences in yields among the rotation treatments are evident.  We have also looked at rhizoctonia incidence and severity in this experiment (data not presented)  These and other results from this experiment should help growers and the industry make rational choices regarding crop rotation, amendment application, water use, and land management programs in the coming years.

 

            We are continuing our studies on selected two-year rotations and their impacts on soil properties and potato productivity (cv. Shepody).  Potatoes are currently rotated with oats, oats underseeded with Italian ryegrass, peas/clover, and a oat/pea/vetch green manure in this study.  Short-term effects have been primarily on N fertility.  The green manure crop has decreased the need for nitrogen fertilizer by 40 to 60 lbs/A relative to the oat rotation, but none of the two-year crop rotations have increased tuber yields.  High rates of N fertilizer in combination with any of the rotation crops tended to decrease specific gravity without improving yield (data not shown).  Tuber size tended to increase with increasing rate of N.  Depending on the rotation and the year, specific gravity decreased by 3 to 4.6 points per 100 lbs of N fertilizer applied.  As N fertilizer rate increased, a greater fraction of the N taken up by the crop remained in the tops rather than being removed in the tubers (i.e. nitrogen use efficiency declined dramatically from 60-70% to near 30%).  Detailed results are available on request.   These two-year rotations have not had dramatic effects on soil organic matter or structure to date, but we anticipate that their effects will increase over time.

 

            AF1753-16, A Possible Shepody Replacement.   In another experiment, AF1753-16 nitrogen rate response was compared to that of Shepody (Tables 7 and 8).  AF1753-16 continues to show promise as an alternative to Shepody for french fry processing and has been higher yielding in virtually all side-by-side comparisons of the two varieties.   AF1753-16 produced 62 cwt/A more yield than Shepody, it had larger tubers, higher gravity, equal external defect incidence, and less hollow heart.  Our results from 2004, show that AF1753-16 does not show a strong yield response to nitrogen fertilizer and that lower rates of N fertilizer can improve maturity.   Results from the first year of this study were presented at the Maine Potato Conference in January 2004.  Additional details are available upon request.

 

            AF1808-18 Nitrogen and Potassium Experiment.   AF1808-18 has potential as a dual-purpose russet.  This study was conducted to look a its response to N and K fertility programs.  Results are presented in Tables 9 and 10.  AF1808-18 had good yields, large tubers, high gravity, and high external defects incidence.  It showed a strong yield response to N fertilizer.  Sunburn incidence was very high in this experiment and for all AF1808-18 trials during 2004.  Sunburn incidence appears to be a major limiting factor for this clone.  Sunburn incidence and external defects were not strongly influenced by fertility program.  Perhaps cultivation practices could be adjusted to reduced the incidence of sunburn in this clone.  Additional details are available upon request.

 

            Metribuzin/Rimsulfuron Sensitivity Study.  Sixteen potato varieties and lines were evaluated in 2004 to determine their sensitivity to post-emergence applications of metribuzin (e.g. Sencor) and rimsulfuron (e.g. Matrix).   Results from this type of experiment help UM and industry make recommendations concerning herbicide applications and they also are useful to our variety development efforts as we make decisions about commercial testing and management profiles for new breeding lines.   Of the sixteen lines tested in 2004, one was very sensitive to postemergence metribuzin, another was sensitive, and five were moderately sensitive (data not presented).  Six of the lines were sensitive to moderately sensitive to foliar injury by  rimsulfuron, but none showed any significant yield loss.

 

            Small Grain and Canola Experiments.   Two malting barley variety trials were conducted during 2004.  In one trial, five two-row malting barley varieties were compared to B1602, a six-row standard variety.   The two-row barley varieties with the highest yields were Merit and Metcalf; however, Merit had low test weight and Metcalf was the most lodging susceptible variety in the trials (Table 11).   Conlon was the best performing two-row barley in 2004.  Garnet and Harrington were high yielding and had a good test weights in 2003, but were low yielding in 2004.  Conlon and B1602 had the highest test weights.   Garnet and Harrington were the earliest varieties in the experiment.  In the six-row malting barley test, all of the varieties produced between 85 and 94 bu/A and were not significantly different in yields (Table 12).   Stander was the most resistant to lodging, while Sizzler was the most susceptible.  Robust, B1602, and Lacey had the best test weights.   Lacey appears to provide a good combination of yield potential, test weight, and lodging resistance.  It has done well through three years of testing.  This information should help the industry maximize the value of its barley rotation crop.  Additional experimental details are available upon request.

 

            A spring milling wheat variety trial was conducted during 2004.  The objective of this trial was to evaluate the potential of several promising new milling wheat varieties and compare them with an established feed variety.  The feed quality variety, AC Belvedere, produced the highest yields (59.4 bu/A).  The highest yielding milling quality wheats were AC Barrie and  AC Walton (Table 13).  Test weights were low for all varieties, especially Grandin, Oxen, and Russ.   AC Barrie, Alsen, and Ingot had the best test weights.   AC Walton showed very good lodging resistance.  Oxen and Russ had severe lodging problems.  Additional experimental details are available upon request.



Table 1.  Supplemental Irrigation and Potash Treatment Effects on Yield, Percent Stand, Tuber Size, and Specific Gravity of Russet

Burbank Potatoes.  Aroostook Research Farm, Presque Isle, ME -- 2004.

____________________________________________________________________________________________________________

 

Irrigation and                                             Yield (cwt/A)1         Percent Tuber Size Distrib. (% wt. Basis)       Specific  

Potash                                                  Total    US#1   US#1      Stand            <2"       2" to    > 10    >3"     >3.5"     Gravity   

Treatments                                                                   >2"       (June 22)                      10 oz.  oz.      Long   Long                      

____________________________________________________________________________________________________________

Irrigation Main Effect (n=32):

 Check                                                 415       339    300         98                11        52        37        86        73           1.089

 Irrigated                                              397       315    276         98                12        52        36        85        73           1.078

 

Potash Treatments [lbs/A, (n=8)]:

At-Planting   Broadcast

 0                                                         403      344      290        99                 16        56        28        85        72           1.097

 100                                                     401      338      294        99                 13        52        35        84        73           1.087

 200                                                     401      340      301        99                 12        54        34        83        69           1.083

 300                                                     413      325      289        99                 11        51        38        86        74           1.080

 100                 200 before 1st cult.       418      331      293        99                 12        50        38        86        74           1.078

 100                 200 at last hilling           420      322      286        97                 11        52        37        87        76           1.082

 200                 100  before 1st cult.      391      312      280         99                 11        51        38        84        71           1.080

 200                 100  at last hilling          398      302      274        97                   9        51        40        86        77           1.081

LSD0.05                                                 38        37        35           3                   3          5          6          4          5       0.004    

AOV Results3:

            Irrigation                                   .06      ns        ns           ns                  ns        ns        ns        ns         ns              *

            Potash Treatment                        ns       ns        ns           ns                  **       ns        **       ns         *              **

                                                                                                                        **L                  **L                                   **L

                                                                                                                                                                                          *Q      

            Irrig. X Potash                          ns         .09      .08         ns                  ns        ns        ns        ns         ns              ns

                                                            .06L     *L        *L                                                                   

____________________________________________________________________________________________________________

1US#1 yield was calculated as total yield minus yield of tubers with external tuber defects (external defects are listed in Table 4).

2Significance of AOV F-tests is presented were: ns=no significant effect; * and ** indicate significance at P<0.05 and <0.01, respectively.  Potash rate response was tested using trend analysis where: L=linear; Q=quadratic; C=cubic.  Pr>F is presented for AOV results when Pr>F is between 0.05 and 0.1.

Table 2.            Irrigation and Potash Effects on Percent External Defects (% weight basis) and Percent Hollow Heart (% count basis) by Size Class of Russet Burbank Potatoes.  Aroostook Research Farm, Presque Isle, ME -- 2004.

____________________________________________________________________________________________________________

 

Irrigation                                                  External Tuber Defects. (% wt. Basis)            Percent Hollow Heart by Size Class (% by Count)1  

and Potash                                           Total    Sun-     Mis      Growth  Scab  Rot                   < 2"        >2" to 10 oz.    > 10 oz.     Overall

Treatments                                                       burn     -shapen Cracks                                    tubers        tubers       tubers

____________________________________________________________________________________________________________

Irrigation Main Effect (n=32):

Check                                                  18.2     1.3       15.4         1.3       0.0   0.3                     2.5           8.8            22.2                            8.8

 Irrigated                                              20.5     1.1       17.3         1.7       0.0   0.5                     1.6           4.4            41.8                            8.5

 

Potash Treatments [lbs/A, (n=8)]:

At-Planting   Broadcast

    0                                                      14.8     0.8       12.8         1.0       0.0   0.2                     3.8          15.0            48.8                        14.0

100                                                      15.4     0.8       12.5         1.1       0.0   1.1                     1.3           3.8            33.8                            7.6

200                                                      14.9     0.6       12.2         1.5       0.0   0.7                     2.5           2.5            31.3                            6.8

300                                                      21.6     1.1       18.6         1.7       0.0   0.3                     0.0           6.3            28.3                            7.4

100                  200 before 1st cult.       20.9     1.0       16.8         2.4       0.0   0.6                     1.3           6.3            28.8                           7.0

100                  200 at last hilling           23.8     2.3       19.7         1.7       0.0   0.1                     0.0           3.8            31.3                            6.6

200                  100 before 1st cult.       19.9     1.2       17.4         1.2       0.0   0.0                     1.3           8.8            20.1                            8.4

200                  100 at last hilling           23.8     1.5       20.8         1.4       0.0   0.1                     6.3           6.5            33.8                           11.3

LSD0.05                                                              5.9     0.8       5.5          1.3        ns    0.9                     5.8            8.2            18.9                          5.3

 

AOV Results2:

            Irrigation                                     ns       ns         ns             ns        ns     ns                        ns              ns   *                 ns           

            Potash Treatment                        **      **        **            ns        ns     ns                        ns             .10            ns               .07

                                                            .08L                                                                                                 *Q           *L                *L

                                                                                                                                                                  .07L                              .06Q

            Irrig. X Potash                          ns         ns         ns             ns        ns     ns                        ns              *              ns                ns

                                                                                                                                                                  .07Q             *L                        *L

____________________________________________________________________________________________________________

1Percent hollow heart is based on 10 tubers per replicate per size class (50 tubers per size class for each individual treatment).

2Significance of AOV F-tests is presented were: ns=no significant effect; * and ** indicate significance at P<0.05 and <0.01, respectively.  Potash rate response was tested using trend analysis where: L=linear; Q=quadratic; C=cubic.  Pr>F is presented

 

Table 3.           Summary of potash rate effects on chip color, incidence of internal tuber defects, and tuber nutrient concentrations,  Atlantic variety (2000 to 2002).  Aroostook Research Farm, Presque Isle, ME

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Potash                                                  Chip                         Incidence of Internal Defects        Tuber Nutrient Conc. (ppm d.w. basis)

Rate                                                     Color               %                     %                     %

(lbs/A)                                                  Agtron              Brown              Hollow Blackspot         K                     Ca        Mg

                                                            Jan. 50F           Center              Heart                Bruise                          

____________________________________________________________________________________________________________

Three-year Average Experimental Results:

 

0                                                          64.2                 20.5                 5.1                   8.2                   15009              171            788           

200