EVALUATION OF WALNUTS UNDER HIGH DENSITY PLANTING AND MANAGEMENT SYSTEMS

D. Ramos, W. Olson, J. Osgood, W. Krueger, G. S. Sibbett, W. Reil, L. Hendricks,

K. Kelly, R. Snyder and K. Ryugo

ABSTRACT

Chico walnut trees planted in 1974 in hedgerows (22' x 11') trained into a

fruiting wall and mechanically pruned since 1978 continue to yield as much ormore crop than standard spaced and pruned trees. In 1989, the yields were as

follows: annual hedging- -two sides, 2.76 tons per acre; annual hedging- -one side(alternate), 3.52 tons per acre; and conventional spaced (22' x 22') and pruned,

2.31 tons per acre. A third hedging procedure in which the trees are hedged ontwo sides biennially (odd years) yielded 2.39 tons per acre. A fourth treatm~nt

consisting of biennial hedging two sides (even years) yielded 3.74 tons per acre.

Hedgerowed trees that were severely topped in 1988 (19% yield reduction) anduntopped in 1989 had significantly greater yield (8% increase) than trees notpreviously topped. Walnut cultivars are being evaluated for their performance

in a high density management system in Tulare, Merced, Stanislaus and YoloCounties. U.C. selections 67-11, 67-13 and 68-104 continue to show promise for

hedgerow planting.

OBJECTIVE

To develop and implement more efficient high density management systems for early

economic production and sustained high yield and quality of walnuts, examine

pruning systems and how they influence tree physiology and productivity, anddetermine adaptability of various walnut cultivars and proper tree spacing androw orientation for hedgerow plantings.

PROCEDURE

The Chico hedgerow trial (22' x 11') established in 1974 near Vina was maintained

and the two hedging treatments initiated in 1978 (one side hedged vs. two sides

hedged each year) were continued in 1989. Yield data were also obtained from

two other hedging treatments started in 1985 in which trees are pruned on twosides biennially, on even or odd years. As in previous years, mechanical pruning

of the hedgerowed trees was performed with a vertical boom hedging machinepositioned to cut about 4 feet from the trunk. No tree topping has been

performed on these trees since 1983. However, another experiment was establishedutilizing guard rows to evaluate the effect of topping to lower tree height.

The test consisted of four guard rows (40 trees each) cut back approximately one-third to a height of 20-22' in 1988 and another four paired rows left untopped.Both treatments were not topped in 1989.

Trials designed to measure the performance of walnut cultivars under a highdensity hedgerow management system are being developed in Tulare, Merced,Stanislaus and Yolo Counties in cooperation with Farm Advisors Sibbett,Hendricks, Kelly and Reil, respectively. The Visalia trial (20' x 10') wasplanted in 1982 and grafted in 1983 to fifteen cultivars in three replicationsof nine trees per plot with the rows oriented east-west. There are two trials

114-- -

in the Winters area. The trial in Solano County includes five cultivars (Chico,

Vina, Chandler, Howard and Amigo) at two different spacings (22' x 11' and 18'x 9'). The 350 trees in this trial were planted as Black walnut seedlings in

1983 and 1984 and allowed to grow one year before grafting in 1984 and 1985.The second Winters trial (22' x 11') is in Yolo County and consists of 520 Black

walnut trees planted in 1984 and grafted in 1985 to thirteen cultivars -- Amigo,

Ashley, Chandler, Chico, Howard, Payne, Pedro, Sunland, Tehama, Vina, 67-11, 67-13 and 68-104. There are four replications of ten trees per plot in this trial.

RESULTS AND CONCLUSIONS

Vina Hedgerow Trial

Yields from the Vina hedgerow trial (cv. Chico) in 1989 were among the highestobtained over the course of the experiment (Table 1). Biennial hedging-even

years (1989 unpruned) and annual alternate side hedging were significantlygreater in yield than the other treatments. This is consistent with the resultsobtained in other years and continues to support the conclusion that annual

alternate side hedging is preferable to hedging two sides each year. The data

also suggest that biennial hedging two sides where the orchard is divided so asto have some trees pruned odd years and others even may be a viable alternative.

The severe mechanical tree topping performed experimentally on guard rows in 1988

resulted in a significant loss in production that season. The topped trees

yielded an average of 1.47 tons per acre compared to 1.80 tons per acre for the

untopped, a reduction of over 18%. In 1989, however, after leaving both

treatments untopped, the yield of the previously topped trees was significantly

greater. The trees that had been topped the previous year yielded 4.1 tons peracre compared to 3.8 tons per acre for tne control, an increase of 8%. Tree

height in the two treatments appeared to be the same, since many of the top

shoots produced in response to the topping in 1988 did not bend over with cropin 1989 as expected. Thus, dormant season mechanical topping by itself does not

appear to be effective in lowering tree height. It my be possible, however, to

combine dormant topping with subsequent summer topping in order to reduce the

vigorous regrowth of shoots on the tops of the trees, thereby lowering canopyheight. This approach will be explored in the coming season.

Performance of Walnut Cultivars in Hedgerow Confi~uration

The trees in the Visalia cultivar trial have completed their seventh year of

growth following field grafting. They were mechanically hedged at four feet fromthe trunk on the north side while the south side remained unpruned to maximize

crop. The trees were not topped. Cumulative yield data (Figure 1) and annualyields for four years (Figure 2) show that 67-11 and 68-104 continue to behighest yielding.

Performance data from the fifth leaf walnut hedgerow trial in Yolo County show

that Sun1and, Payne, Chico 67-13 and 68-104 were the highest yielding in 1989

(Table 2). Cumulative (Figure 3) and annual (Figure 4) yields over three years

also show these five cultivars to be the most precocious and consistently higher

yielding. Selection 67-13 produces catkins in abundance and is homogamous whichcauses some concern about possible autoregulation (Table 3).

115

The sixth leaf walnut hedgerow trial in Solano County is designed to provide

information relative to tree spacing and row orientation. The first three years'

yield data suggest that the 9' x 18' spacing does not justify the additional treeestablishment costs and may actually be detrimental when compared with 11' x 22'

planting (Table 4). A yield differential related to light exposure is apparent

in this east-west oriented planting with greater crop on the south side of the

tree than on the north side (Table 5). This differential is consistent amongthe four cu1tivars in the trial at the 11' x 22' planting, but is no longerevident in 1989 at the 9' x 18' planting (Table 6). This again suggests that

the higher tree density may be too close and already starting to show the adverseeffects of tree crowding and shading.

116- ---

TABLE 1. YIELD OF HEDGEROW WALNUTS -- CV. CHICO, PLANTED 1974

Treatment

Annual Hedgingone side

(alternate)

Annual Hedgingtwo sides 3.61 c 2.22 c 2. 70 ab 1. 31 bc 2.76 b

Biennial Hedging(odd years)two sides

3.75 bc 3.36 a 1.94 c 2.25 a 2.39 b

Biennial Hedging(even years)two sides

4.65 a 2.12 c 3.15 a 1.07 c 3.74 a

Standard densityand hand pruned

3.64 bc 2.54 bc 2.54 b 1.26 c 2.31 b

ZMeans within columns followed by the same letter are not significantly differentat R - 0.05, Duncan's Multiple Range.

117

Dry Tons per Acre

1985 1986 1987 1988 1989

4 . 24 abz 2.90 ab 2.68 b 1.70 b 3.52 a

Figure 1. Walnu.t CV Yields in Hedgerow ConfigurationTotal Tons/ac (1986 - 1989) Visalio

15

10(1)L-oo

""-(I)co

5

Cultivor

~18-- --

00 Q) t: 0 0 I"') 0 ..- v L- 0C7I C Q) 0 c ..- E ...... 0 L- ..9? I.. c'E

>. I/) :c :c > I :e I ,... '=' "U "U 00 0 c CP C< a.. () "'- .r:. 0 "'- I 0 0 a.to Q1 :I: to IX) :J

t- to J: .s:: V>()

- - - - - - _.. -

Figure 2. Walnut CV Yields in Hedgerow ConfigurationL. Bennetts- VisalioI Co (210 trees/ ac)

<I)L..oo

' 2encoI-

- - - -

4

1

o

119

~ 1986

~ 1987

~ 1988

~ 1989

-

a 4) L- a 0 rt') a ..- v "U L- a "Uen c L- 0 c: E 0 L- L- c:CD ..- ..-

]If) :c :2 > I =t I ..- 0 '0 " 00 CD

a. u ..... .£: 0 ..... I 0c: a. C

to CD :::I: to CO 0 :JI- to :::I: .£: VJ0

Table 2. 1989 Yield Evaluation of Yolo County 5th LeafWalnut Hedgerow 11x22 Foot Planting with North-South Rows

Data represents mean of 4 replicates of 10 trees.

1. Pounds per acre2. Value followed by the same letter are not significantly dlfferent -

Duncan's Multiple Range - 5~ level

120

-----

1Yield

Variet:i 1989 1988 .!lli Total

2 2Payne 4059 AB . 2173 AB 232 646467-13 3604 ABC 2481 A 337 6422Sunland 4241 A 1406 CD 384 6031Chico 3860 AB 1305 CD 243 540868-104 3220 BC 1887 BC 216 5323Ashley 2976 CD 1278 0 136 439067-11 2956 CD 1334 CD 78 4368Vina 2787 CDE 1409 CD 94 4290Howard 2347 DEF 1066 DE 138 3551Pedro 2196 DEF 1089 DE 94 3379Amigo 2039 EF 1033 . DE 140 3212Tehama 1917 FG 548 E 50 2515Chandler 1155 G 859 DE 94 2108

-----------------------------------------------------------------------------L.S.D. 784 534

Figure 3. YOLO COUNTYWALNUTHEDGEROWCUMULATIVEYIELD (180 TREES/AC.)

4

121.

3 l'f l't r--, 1989. 5th leaf

w

2fi.rqn1988a:::u ,4th leaf-=

.......en

1fl1z

[Ill 1987:: 3rd leaf

------------- --- --- --- ----

1- - ---

'"GotC .-

II. -Got ('I') fa 0 0 - '" f 0c - - u - - - fa fa en fa c>.. I c . I J: I C ! - J: fafa .... = .J:: co In .... - Got .i Got J:Q. \Q en u \Q -= \Q > :: Q. to- u

Cult1var

Figure4.

- --

YOLO COUNTYWALNUTHEDGEROW

YIELD PERFORMANCEOF CULTIVARS FOR LAST 3 YEARS

2

QJ~uc:(

';;;- 1coI-

122

- --.---...-

1989

1988

1987

- - - -- -.--- ._- --- -- --

1/

[/ -

,

E f t "' ... SI

-a QJc <:T >, -a '"':0

QJ C') '" 0 <:) QJ ..... 0 0 Ec ...... C u ......

'C...... '" '" 0> '" C>, I I I C -a . .J:: '"'" r-... .J:: co V1 r-... 0 QJ E QJ .J::0.. \.D (/) U \.D C:(, \.D :> =c 0.. c:( I- U

Table 3. 1989 Evaluations of Yolo County 5th LeafWalnut Hedgerow 11x22 Foot Planting with North-South Rows

1. 3rd leaf grafts2. Vigor '

1 = No new growth2 = Few new shoots, one foot of new growth3 = Moderate no. of new shoots; 2-3 feet of new growth4 = large no. of new shoots; 3-4 feet of new growth5 = Profuse new shoots; 4-5 feet of new growth

3. Uprightness1 = Normal (upright)2 = Some "willowing" of new growth3 = Excessive "will owing" of new growth

4. Catkin ratingo = absent1 = less than 10 per tree2 = 10-20 catkins per tree3 = Adequate 20-40 catkins per tree4 = Plentiful 40-80 catkins per tree5 = Abundant 80+ catkins per tree

5. Date 1st or last catkin or pistillate bloom occurred

123

-- --

Catkins Pisti11ate B100m2 3 4 5 5 5 5

Variety Vigor Uprightness Rating 1st Last 1st Last------- ------ ------------ -------Payne 2.6 2.6 3 3/28 4/6 4/1 4/1067-13 3.7 1.2 4 4/1 4/13 4/7 4/13Sunland 4.0 2.6 5 3/23 4/6 3/27 4/12Chico 3.3 1.3 3 4/3 4/18 3/26 4/768-104 3.5 1.6 4 4/4 4/25 4/11 4/18AShley 3.3 2.7 2 3/28 4/7 4/3 4/1167-11 4.0 1.3 3 4/5 4/17 4/8 4/17Vina 3.6 2.6 3 4/4 4/14 4/8 4/17Howard 2.2 1.6 2 4/4 4/14 4/10 4/25Pedro '3.4 2.5 4 4/4 4/16 4/7 4/24Amigo 2.8 1.7 3 4/10 4/22 4/6 4/12Tehama 3.7 2.3 3 4/7 4/15 4/10 4/18Chandler 2.8 1.3 2 4/5 4/15 4/12 4/24

1Cisco 3.5 1.1 3 4/14 5/1 4/17 5/10--------------------------------------------------------------------------------

Table 4. . . 1989 SOLANOCOUNTY6TH LEAF WALNUTHEDGEROWTRIALEAST-WEST ORIENTED ROWS

Table 5. 1989 SOLANOCOUNTY6TH LEAF CHICO WALNUTHEDGEROWTRIALEAST-WEST ORIENTED ROWS 11X22 SPACING

ALTERNATESIDE HEDGING

11 X 22 Planting - (180 Trees/Acre)

Varietv 1989 1988 1987 Total

Chico 5065 3870 2282 11,217Vina 3857 2651 1537 8,045Chandler 2203 2725 1732 6,660Howard 3155 2648 1583 7,386Amigo 3928 1665 629 6,222

9 x 18 Planting (269 Trees/Acre)

VarietY 1989 1988 1987 Total

Chico 4445 4563 2759 11,767V1na 3487 2398 1079 6,964Chandler 2149 3447 1855 7,451Howard 3443 3301 1803 8,547

Comparison of the Two Spacings - Average of the Four CommonVarie1es Lbs/Ac.

11 x 22 3570 2974 1784

9 x 18 3381 3427 1874

9x18/11x22 -5% +13% +5%

Table 6.

1.Ratio of the south side yield divided by the north stde yield.

125

--- -- - ----

1989 SOLANOCOUNTY- 6TH LEAF WALNUTHEDGEROWTRIALEAST-WESTORIENTED ROWS

Yield in Lbs. Per Acre Per Side of Tree

11 x 22 Planting

Variety Side of Tree 1989 1988 1981

Chico N 2005 1620 1121S 3060 2250 1154

Vina N 1645 1058 651S 2212 1593 880

Chandler N 905 1215 889S 1298 1510 846

Howard N 1368 1115 860S 1181 1414 125

Average N 1481 1261 884S 2090 1108 902

1.Average SIN 1. 41 1.35 1.02

9 x 18 Planting

Chico N 2119 2159 1335S 2266 2408 1426

Vina N 1196 1143 411S 1691 1254 609

Chandler N 1191 1506 831S 952 1940 1026

Howard N 1833 1500 820S 1611 1802 985

Average N 1152 1511 864S 1631 1853 1012

Average SIN 0.93 1.11 1.11