walnuts on system and

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1 WALNUT HEDGEROW PLANTING ON MARGINAL SOILS Bill Krueger, John Edstrom, Wilbur Reil, Bill Olson, Ron Snyder ABSTRACT A north-south 12 ft. by 18 ft. Walnut Hedgerow planting was established at the Nickel's Soils Laboratory in Arbuckle, California, in the spring of The soil is less than ideal and not traditionally considered suitable for walnut production. The performance of two varieties (Chandler and Howard) and two rootstocks (Paradox and Northern California Black) are being compared on slip plowed and non-slip plowed soil. Significant production occurred for the first time in Of the three things being compared (rootstock, variety, and soil modification), rootstock has had the greatest impact on yield with Paradox having significantly higher yield in Although there was a trend for higher production for Howard compared to Chandler it was significant only on Northern California Black (NCB) in the slip plowed section and on Paradox in the non-slip plowed section. Slip plowing had no significant impact on yield except with Howard on NCB, the least vigorous variety on the least vigorous rootstock, where yields were significantly greater for slip plowed than nonslip plowed trees. OBJECTIVES To investigate the feasibility of producing English less than desirable soils using a hedgerow planting low volume irrigation. walnuts on system and To assess the effect of soil modification (slip plowing to a depth of 6 feet on 5 ft. centers) on tree growth and performance under the soil conditions found at the Nickel's Soils Laboratory. To compare the performanceof Northern California Black and Paradox rootstocks on soils of the type found at the Nickel's Soils Laboratory. To test the adaptability of two relatively new walnut Chandler and Howard, to the hedgerow system under the found in the trial. cultivars, conditions PROCEDURE The trees were planted during the spring of 1986 at the Nickel's Soils Laboratory in Arbuckle. The planting configuration was a hedgerow, 12 ft. between trees in the row and 18 ft. between the rows giving 202 trees per acre with a north-south row orientation. Prior to planting half of the plot was slip plowed to a depth of 6 ft. on 5 ft centers. Six replications of four treatments consisting of combinations of two varieties (Chandler

2 ~ and Howard) and two rootstocks (Paradox and Northern California Black) were planted in a randomized complete block design in both the slip plowed and non-slip plowed sections. Because Howard on Paradox was unavailable at planting time Paradox rootstock was planted in its place in 1986 and grafted to Howard in Rootstocks were planted around the outside of the 2.2 acre plot and, during 1987 through 1988, grafted to cisco or Franquette to insure adequate pollination. The trees were drip irrigatedand cultural practices were what was considerednecessary to insure good growth and development. The trees were trained and pruned to develop a fruiting wall. Significant production occurred for the first time during 1990 and the yields were recorded. RESULTS Rootstock Comparisons When all plots with Paradox as the rootstock were considered as replications and compared to all plots using Northern California Black as the rootstock Paradox significantly outyielded NCB, 1041 lbs/ac versus 866 lbs/ac. Chandler on Paradox significantly outyielded Chandler on NCB, 979 lbs/ac vs. 757 lbs/ac. Additionally, Chandler on Paradox in the slip plowed section significantly outyielded Chandler on NCB in the slip plowed section, 1028 lbs/ac vs. 707 lbs/ac. Although Paradox consistently outyielded NCB there were no significant differences using Duncan's Multiple Range Test at the 5% level of confidence for any of the other comparisons made (Table 1). Variety comparisons Although there was a trend to higher yield for the Howard variety compared to Chandler the difference was significant only when the varieties on NCB in the slip plowed section were compared and when the varieties on Paradox in the non-slip plowed section were compared (see Table 2). This occurred despite the fact that Howard was not grafted to Paradox until the second year. Slip Plow Comparison There were no statisticallysignificantdifferences for any of the Slip Plowed versus Non-Slip Plowed comparisons with the exception of Howard on NCB (Table 3). DISCUSSION Currently, of the three things being tested rootstock appears to have the greatest effect on yield. These differences will probably increase as yield increases

3 -- Although there was a trend for higher production with the Howard variety it was significant only on NCB in the slip plowed section and Paradox in the non-slip plowed section. This trend will be followed in future harvests. Slip plowing had a significantimpact on yield only with Howard on NCB, the least vigorous variety on the least vigorous rootstock. The trends and differences which are beginning to appear will followed in future years. be 95

4 TABLE 1. Com arisons Rootstock Comparison Treatment Means Inshell lbs Ac 1 Paradox 1032 A * Northern California Black (NCB) 866 B 2 Paradox Slip Plowed 1041 A ** NCB Slip Plowed 910 A 3 Paradox Non Slip Plowed 1022 A ** NCB. Non Slip Plowed 822 A 4 Paradox - Chandler 979 A ** NCB - Chandler 757 B 5 Paradox - Howard 1085 A ** NCB - Howard 976 A 6 Paradox - Chandler - Slip Plowed 1028 A *** NCB - Chandler Slip Plowed 707 B 7 Paradox - Chandler Non Slip Plowed 930 A *** NCB - Chandler Non Slip Plowed 806 A 8 Paradox - Howard Slip Plowed 1055 A *** NCB - Howard Slip Plowed 1114 A 9 Paradox - Howard Non Slip Plowed 1115 A *** NCB - Howard Non Slip Plowed 838 A Comparisons followed by the same letter are not statistically significantat the 5% level of confidenceusing Duncan's Multiple Range Test. * Means of 24 replications ** Means of 12 replications *** Means of 6 replications

5 TABLE 2. Variety Comparison Treatment Means Com arison Inshell lbs Ac 1 Howard 1030 A * Chandler 868 A 2 Howard on Paradox 1084 A ** Chandler on Paradox 979 A 3 Howard/NCB 976 A ** Chandler/NCB 757 A 4 Howard Slip Plowed 1084 A ** Chandler Slip Plowed 867 A 5 Howard Non Slip Plowed 976 A ** Chandler Non Slip Plowed 867 A 6 Howard/Paradox Slip Plowed 1055 A *** Chandler/Paradox Slip Plowed 1028 A 7 Howard/Paradox Non Slip Plowed 1115 A *** Chandler/Paradox Non Slip Plowed 930 B 8 Howard/NCB Slip Plowed 1114 A *** Chandler/NCB Slip Plowed 707 B 9 Howard/NCB Non Slip Plowed 838 A *** Chandler/NCB Non Slip Plowed 806 A Comparisons followed by the same letter are not statistically significant at the 5% level of confidence using Duncan's Multiple Range Test. * Means of 24 replications ** Means of 12 replications *** Means of 6 replications 97

6 TABLE 3. Slip Plow Comparison Comparisons Treatment Means lbs/ac 1 Slip Plowed 976 A * Non Slip Plowed 922 A 2 Slip Plowed Paradox 1041 A ** Non Slip Plowed Paradox 1022 A 3 Slip Plowed NCB 910 A ** Non Slip Plowed NCB 822 A 4 Slip Plowed Chandler 867 A ** Non Slip Plowed Chandler 868 A 5 Slip Plowed Howard 1084 A ** Non Slip Plowed Howard 976 A 6 Slip Plowed Chandler on Paradox 1028 A *** Non Slip Plowed Chandler on Paradox 930 A 7 Slip Plowed Chandler on NCB 707 A *** Non Slip Plowed Chandler on NCB 806 A 8 Slip Plowed Howard on Paradox 1055 A *** Non Slip Plowed Howard on Paradox 1115 A 9 Slip Plowed Howard on NCB 1114 A *** Non Slip Plowed Howard on NCB 838 B Comparisons followed by the same letter are not statistically significant at the 5% level of confidence using Duncan's Multiple Range Test. * Means of 24 replications ** Means of 12 replications *** Means of 6 replications