2011 Annual Report for FNC10-833
Field Grafting Improved Chestnut Cultivars to Increase Yield: An Operational Test in an Agroforestry System.
Summary
The expected timing of the SARE grant award in the spring of 2011 was late enough that I anticipated all the chestnut grafting work would take place in spring of 2012. However, the SARE grant was finalized early enough in 2011 for us to be able to initiate the experiment in the spring of 2011 by grafting about 10 percent of the trees in the study. The remainder of the trees will be grafted in late April or early May of 2012. As part of this process we finalized the experimental design and established the treatments (details below). Dr. Ken Hunt grafted a total of 37 trees (additional details below) with scion wood selected from Chinese chestnut varieties Qing, Gideon, Eaton, and Auburn Super. The 2011 graft success rate was 95 percent. Ken taught me the basics of caring for grafted trees, and I did so for those that were grafted in spring 2011.
Objectives/Performance Targets
The objective of this grant is to measure the increase in chestnut yields that can be gained by grafting scion wood selected from improved chestnut cultivars to young Chinese chestnut trees established in an agroforestry operation designed to simultaneously produce chestnuts and forage.
Performance will be measure by:
1. Establishment of an experimental design to test outplanting of three improved Chinese chestnut cultivars
2. Grafting trees according to the experimental design
3. Measuring graft success rates
4. Maintaining grafted trees
5. Measuring chestnut yield by cultivar for 5 subsequent years
6. Reporting results of the analysis
7. Providing demonstrations or other outreach activities
Accomplishments/Milestones
Experimental design and preliminary graft trial, 2011:
My primary chestnut orchard consists of 17 rows (Figure 1). Rows are variable in length; the longest have room for a maximum of 27 trees. Planting locations are on a 26-foot square spacing within and between rows. I planted unimproved Chinese chestnuts, mostly of the Qing variety, beginning in 2007. The actual number of live, graftable trees in each row varies depending on row length and tree survival; 12 to 14 trees per row are typical.
In the spring of 2011, I set up a complete, randomized block experimental design using an orchard row as a treatment unit. Each row was assigned one of four grafting treatments: (1) graft with Qing scion wood, (2) graft with Gideon scion wood, (3) graft with Eaton scion wood, and (4) control with no graft. Blocks were groups of four adjacent rows that together received a full set of treatments. There are four blocks (16 rows) in the experiment. Treatments were randomly assigned to each row within a block (Table 1).
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Table 1. Experimental design and results of preliminary trial in 2011.
(See the attached document for a fully formatted version of this table)
Orchard No. of trees grafted Number of surviving
row Block Treatment in spring 2011 grafts in 2012
B 1 Gideon 3 3
C 1 Eaton 3 2
D 1 Control 0 NA
E 1 Qing 3 2
F 2 Control 0 NA
G 2 Gideon 3 2
H 2 Eaton 3 3
I 2 Qing 4 4
J 3 Gideon 4 4
K 3 Qing 3 3
L 3 Eaton 3 3
M 3 Control 0 NA
N 4 Gideon 2 2
O 4 Qing 3 3
P 4 Eaton 3 3
Q 4 Control 0 NA
TOTALS 37 35
Dr. Ken Hunt grafted trees on April 30, 2011. He utilized three-flap (banana) grafts on trees up to about 1/2-inch in diameter at the graft union. For larger trees (1 to 5 inches bole diameter) he used an inlay bark graft with up to three pieces of scion wood grafted per tree. Nearly all of my established chestnut rootstocks are of the Qing variety (unimproved).
Table 1 identifies the assignment of treatments and the number of grafted trees in each treatment replicate for the preliminary trial in 2001.
The initial scion wood came from cultivars at the Center for Agroforestry at the University of Missouri (http://www.centerforagroforestry.org/ ) in New Franklin, Missouri. Cultivars in the trial are Qing, Gideon, Qing, and a control (no grafting). For demonstration purposes (not part of the formal experiment), Ken also grafted scion wood from the Auburn Super cultivar on four trees adjacent to the study site.
On March 10, 2012, Ken Hunt and I collected scion wood for 2012 grafting from the new growth of shoots that he grafted in 2011. Supplemental scion wood purchased from other sources.
Maintenance of grafted Chinese chestnut trees in 2011:
I staked each grafted tree with a heavy-duty steel stake (usually 1-inch galvanized electrical conduit). I caged each tree with welded wire to a height of 5 feet to minimize deer damage.
I applied a fertilizer (20-10-10) with slow release nitrogen beneath the drip line of each tree in April (shortly prior to leaf out) and again in mid-June.
I mowed tree rows twice during the growing season.
I applied glyphosate herbicide (1.5%) twice (April and July) around each tree at to achieve a treated diameter on the ground equal to approximately the tree height.
I watered grafted trees once per week when it did not rain. August and September 2011 were exceptionally dry with only 4.1 inches of total precipitation.
Graft success from preliminary graft trial:
Across all cultivars, 35 of 37 grafted trees survived in the preliminary trial, a 95 percent success. Larger trees (1 to 4 inches in diameter at the graft point) received two or three inlay bark grafts to reduce the amount of time required to completely heal the cut bole of the tree at the graft union (see Figure 2). Those grafts were considered a success if at least one graft per tree survived, but in most cases multiple grafts survived. One of grafted trees that failed was lost because the entire tree died due to drought after the graft was well established.
Chestnut yields in 2011:
As expected, the grafted trees produced virtually no chestnuts in the autumn of 2011. The remaining orchard trees (predominantly 3-year-old trees but including some 5 year-old-trees) also produced virtually no chestnuts, due to an extended drought. Although the trees are still young, in previous years many had produced small quantities of well-formed chestnuts. August and September 2011 were extraordinarily dry, and I did not irrigate the orchard trees that were not grafted. Consequently, few of the non-grafted trees produced burs (chestnut seed pods that typically contain 2 or 3 chestnuts), and the burs that formed failed to fill out and produce chestnuts of marketable size.
Discussion:
We decided to replace the Eaton cultivar in the study with the Peach cultivar. In the last year an exceptional number of graft failures have been reported for Eaton cultivars that were grafted about 8 years prior. Until the cause of this delayed graft failure in Eaton cultivars is resolved, it seems prudent to switch to another cultivar. Like Eaton, the Peach variety has high nut yields but has not shown similar problems with graft failure.
Activities scheduled for 2012
March 10: Collect Qing, Gideon, and Auburn Super scion wood from new growth on my trees that were grafted in spring 2011.
March: Arrange to purchase Peach scion wood (replacement for Eaton) from another Missouri grower.
March: Invite other interested individuals and local FFA to grafting demonstration.
April 7-15: Herbicide around individual trees with glyphosate (repeat in June and August)
April 15-20: Fertilize trees with 20-10-10 fertilizer (slow release N); repeat in June and August.
April 22-May 12: Graft the rest of the trees in my plantation according to the experimental design (Table 1).
May: Stake and cage all grafted trees.
May, June, and September: Monitor graft success
September: Measure yield by variety of trees grafted in spring of 2011. Trees grafted in spring of 2012 will have little or no nut yield.
Subsequent years: Continue fertilizer application and weed control around trees. Continue to measure yield by total weight for each plantation row where each row is an experimental unit assigned to a specific chestnut variety (Qing, Gideon, Peach, or Control).
Impacts and Contributions/Outcomes
There are no impacts to report at this early stage of the project.