Blueberry Field Renovation
During the 30+ years we have been raising blueberries in the Missouri Ozarks, we have noticed a decline in the vigor and productivity of a field after it reaches 20 to 25 years of age. Typically at that time, in our area, growers who have found it necessary to replant in the same location have had problems getting new plants established. This is particularly a problem on you-pick farms where all of the farm facilities such as parking lots, check-out buildings, store, restrooms, restaurant, etc., are adjacent to a declining blueberry field. In this project, we are attempting to establish a protocol that will allow us to renovate, replant and reestablish an integral field, rebuilding it to once again be a productive part of our operation. I would also like to mention here that each phase of this project has captured the interest of our farm guests and provided an educational opportunity for them to better understand our approach to sustainable farming practices, from cover-cropping to planting. The project has not only generated many questions but it has our repeat customers pulling for our efforts to renovate one of their favorite fields.
There are five components of this project: Field Cleanup, Cover Crops, Preparation of Soil Amendments, Planting and Data collection/Data Analysis.
We have completed four of these primary project components successfully and have had one round of data collection and completed analysis for the new field’s first growing season. As we anticipated, we feel that a second year of data collection is necessary to really get a feeling for the relative value of each of the soil amendments. This may be due to the typical nature of the blueberry root growth. Blueberry roots have a tendency not to grow much out of the existing root ball over the first growing season. We feel that this characteristic minimizes any effect that our soil amendments could have had on plant growth. This theory seemed to be validated sometimes by an inverse relationship between growth and vigor of a plant and the application of amendments. While finding that a certain amendment might have a deleterious impact on plant growth or vigor, I feel that it requires an additional growing season to further verify such a finding. An alternative explanation might be that soil moisture could have been impacted by the addition of the full complement of soil amendments used. We are therefore requesting an additional unfunded extension for this project through the 2017 growing season, to be completed with the final report completed by December 15th of 2017. We will also continue Fall data collection over the next 3 years so that we will have a complete view of our efforts. This information will be made available in outreach efforts as well in years to come.
Our project is progressing well with regard to our objectives. Specifically, objectives achieved include:
1. Field clean-up (Completed July 2012) a. Old plants were removed, including the roots as fully as possible. b. Previous irrigation lines were removed. c. Soil that was previously mounded for the raised beds was distributed over the field so as to expose it to full cover crop treatments and to facilitate cultivation of cover crops.
2. Cover Cropping a. Sorghum Sudan cover crop (prepped field, planted, chopped up and incorporated by turning in with plow in Springs of 2012, 2013, 2014 & 2015) b. Mustard cover crop (prepared field, planted, chopped up, incorporated and rolled field to maximize bio- fumigative impact (early Spring 2013) (Late crop of Sorghum Sudan was also planted in 2013.)
3. Plants selected acquired and scheduled to arrive just prior to planting time. We selected the variety Duke as the trial variety, in that it has typically been a strong variety for us and it is an early variety appropriate for planting close to the location where farm guests enter our fields.
4. Preparation of soil amendments (Preparation was necessary to make sure soil amendments/treatments were ready for the time of planting.)
a. Worm casting tea. I attended a composting class which included a vermiculture component, conducted by Dr. Hwei Yiing Li Johnson of Lincoln University which added to my composting knowledge and aided us in establishing two worm beds for use to inoculate our worm casting tea.
b. Inclusion of worms into planting holes. We planted five worms at each planting site included in the project. We had to first select a variety of worm that would 1) have the desired impact and 2) could function in a blueberry root zone environment. Our research led us to Alabama Jumpers, which are large composting worms that work well in breaking up clay, which is one of our field issues. We tested these worms in soils rich in each of the amendments we were planning on incorporating and found that they did best in a mixture of all the amendments incorporated into soil. Alabama Jumpers were acquired and scheduled to be delivered at planting time.
Various media buckets were prepared and 40 worms were placed in each bucket with indicated media to determine if the worm were compatible. They were left for 34 days. The worms seemed most compatible with the full complement of amendments where nearly all of the worms remained in that media bucket.
c. Ground pine bark. We located a fence mill that stripped the bark from pine logs and we acquired approximately 40,000 pounds of bark and ran it through a shredder that produced an amendment with smaller than ¼-inch pieces. This was piled in a conical pile 8 to 10 feet tall. It heated up considerably prior to use but did not fully compost.
d. Composted shiitake logs. Our own existing spent shiitake logs were ground up using a rented commercial chipper. This process took a bit over a week and yielded two piles of shiitake log chips that were composted. We monitored the core temperatures of the piles and turned when temperature began declining. We added some nitrogen in the form of urea at a very low rate when we turned the piles.
e. Spent coffee grounds. Approximately 45,000 lbs. of spent coffee grounds were obtained from a commercial coffee brewing plant that produced iced coffees. These grounds were delivered to the farm and covered prior to incorporation into the soil.
5. Planting was accomplished in The Early Spring of 2016.
a. Field was plowed and disked.
b. A blade was used to throw up the raised beds for planting, as is the SOP for planting blueberries at our farm. (Blueberries are planted in raised beds for drainage, preventing the roots from remaining in standing water.)
c. Beds were further cleaned up with a drag, and large rocks were removed from the field.
d. Our planting lister/sub-soiler was used to open up a planting trench down the middle of each raised bed.
e. We used our mulch wagon to haul and apply coffee grounds, ground pine bark and composted shiitake logs down the middle of each trench, with the exception of row 81, in which we tested each individual amendment separately.
f. Row 81 was laid out so that the first 5 plant spaces were guard plants with no amendments. The next 14 plant spaces were marked for the first amendment, then 5 more guard plants with no amendments, then 14 more for the second amendment and so on. Each amendment trial was marked with a metal stake with a trial #.
#15 Composted Shiitake Logs
#19 Coffee Grounds
#150 Pine Bark
#12 Worm Casting Tea
#155 Earthworm Inclusion
Figure 3. Trial plant identification stake numbers for row 81.
g. A rototiller (approx. 18 inches wide) was used to thoroughly mix amendments.
h. Irrigation line was laid out in preparation of planting.
i. Plants were spaced at 4-foot intervals in the row.
j. As a row was completed, irrigation line was placed and the plants were watered in.
k. Each row was mulched with hardwood chips, as per farm SOP for planting blueberries.
l. Plants were maintained, as per farm SOP
i. Weekly fertigation
ii. Weekly foliar fish emulsion
iii. Irrigated as needed.
6. Data Collection
a. Plants were maintained through the growing season and data was collected after the plants became dormant.
b. 4 data items were collected for each plant in test row 81. We are including data from the guard plants — the 5 untreated plants between each trial — as controls. We also recorded the same observations from a random sample of plants that received what we termed full treatments (all amendments, worm inclusion and worm castings tea.)
i. Height of plant measured to its longest cane.
ii. Number of new shoots sent up.
iii. Grower interpretation of its vigor, with 1 being least vigorous and 4 being the most vigorous. All observations were made in the same day by the same person, and attempts were made to be consistent in evaluation of all plants.
iv. Fall coloring scale 1 – 4, where 1 = early fall coloring (stress), and 4 = later fall coloring (less stress)
7. Data analysis was accomplished using SAS software to evaluate whether the difference between data compared for 2 treatments was statistically significant at the .05 level.
a. As we compare the various trial groups, it seems important to extend the project through an additional growing season because either many of the amendments have had the exact opposite effect than anticipated, or as previously related, the roots have yet to extend out of the root ball far enough for the soil amendments to significantly impact the plant growth and vigor.
b. Of particular interest is the data generated from the full treatment trial. Data relating to growth and vigor are lagging well behind many of the separate amendments.
c. Another interesting trend in our data is that our control trial is outperforming many of the treatment trials. Once again, I feel that another growing season is in order for us to better understand the full impact of the amendments/treatments used.
While our study project is laid out for us to better understand the value of the treatments under consideration, we have yet to accumulate enough information to draw any conclusions. We have found that it is extremely unusual for plants to flourish in their first year on our farm. More typically, they have more significant growth in their second and third years. I believe that as we collect data for the second growing season, we will be more able to attribute the relative value of the various amendments we are considering. Please find below some data trends, much of which is inconsistent with our experience and not what we anticipated, but nevertheless what has been observed to date. All relational comparisons were deemed “statistically significant” at the 5% level.
• With regard to the control plants
o Control plants had higher vigor ratings than either full treatment plants or those treated with pine bark.
o Control Plants had greater growth than either plants treated with worm casting tea or plants treated with pine bark.
• With regard to full treatment plants
o Plants treated with worm castings tea, amended with shiitake compost, amended with coffee grounds or that had earthworm inclusions all received higher vigor ratings than did plants that received all treatments.
o Plants that received earthworm inclusion also had greater growth than did the plants that received all of the treatments.
• Plants treated with coffee grounds received higher vigor ratings than did those receiving worm casting tea, and also initiated fall color later which may indicate that they were less stressed.
• With regard to earthworm inclusion
o Plants that received earthworm inclusion had greater growth than plants treated with shiitake compost, coffee grounds or with pine bark.
o Plants that received earthworm inclusion had a higher vigor rating than did those treated with pine bark. It seems very premature to attempt to explain these results as they may, as stated previously, be due to the nature of blueberry roots’ nature to not extend far from the original root ball over the first year in the field. We anxiously await data from next fall that will give us a better idea of the relative value of the treatments used.
Impacts and Contributions/Outcomes
To date, with the exception of a few interested grower visits/conversations, I have had little in the way of contributions to other operations, as we have yet to accumulate enough data to understand what is going on with the amendments involved in our project. I did have a conversation with Dr. Ben Fuquay, Soils Professor Emeritus at Missouri State University, with regard to mycorrhizae/inoculum as it relates to blueberry plants. He is presenting a talk at the Blueberry School held at Missouri State University Department of Agriculture next week (April 2017) regarding blueberry roots and Mycorrhizae. I was able to relate our experience to date and told him I would be happy to share the limited information we have to date.
Patrick Byers (MU Extension) is advising the project, Dr. Hwei Yiing Li Johnson of Lincoln University advised with regard to composting and vermiculture and Andrew Thomas (MU) conducted the statistical analysis of the data.