A high-density system using nursery trees is the most economically viable system for a new pear orchard, despite the high cost of the trees and trellis at planting, a study in California shows.

Rachel Elkins, pomology advisor with University of California Cooperative Extension in Lake County, said an economic analysis based on a systems and rootstock trial shows that a high-density planting of fresh pears, using a precocious rootstock, becomes profitable sooner than either a standard orchard or a high-density orchard planted as sleeping eyes.

Speaking during the International Fruit Tree Association’s annual meeting, Elkins described how she began her trial on pear systems and rootstocks in the early 1990s, after noticing that pear orchards in California tended to have very tall trees, whereas in other tree fruits, the trend was shifting towards smaller trees. In Europe, pear growers are adopting high-density systems not only because of the prospect of an earlier return on investment, but in order to mechanize orchard operations and make more efficient use of the land, she said.

At the time she began the study, many of the pear orchards in California were interplanted in hedgerow-type orchards, which was causing shade problems. Although Old Home by Farmingdale rootstocks were available, they were not being widely used. In the heavy soils of the north coastal area, the standard rootstock, Pyrus betulaefolia, grows well but produces very vigorous trees and is not suitable for high-density systems.

Elkins set up a trial in 1993 in a commercial orchard in Lake County, planting Golden Russet Bosc on five different training systems and nine commercially available rootstocks, making a total of 45 system/rootstock combinations. Six of the rootstocks (OHxF.69, 97, 217, 333 and 513 and P. betulaefolia) were planted as grafted trees.

The three other rootstocks (OHxF.40 and 87, and Quince BA29C on a Comice interstem) were only available as seedlings, so they were grafted that year to Bosc and were not included in the results of the study, since their growth was delayed a year.

Elkins took yield data from the fourth to tenth leaf, and then again in the thirteenth leaf to see if earlier findings still held true. She found that the “honeymoon” years for rootstocks were years three to five. Some that looked good in the early years did not look as good from year six onwards.

The training systems she compared were:

—Central leader on a 9- by 15-foot spacing

—A three-leader system that was similar to the central leader but had more leaders as a hedge against fireblight, also planted 9 by 15 feet apart

—A parallel hedgerow (the grower’s system), which was a single- or two-leader tree similar to a vertical axis but taller, spaced 9 by 15 feet apart

—A perpendicular fan, which was a freestanding V system with trees 4.5 by 15 feet apart, and

—Tatura trellis, also on a 4.5- by 15-foot spacing

The freestanding trees grew about 15 feet tall, but the height of the Tatura trees was limited to 8 feet to avoid ladder use.

Combination

After comparing all the various combinations, Elkins concluded that it was not just the training system that was important, nor just the rootstock, but the combination of the rootstock and training system. A rootstock might look good with one training system, but not another, and a training system might work with one rootstock but not another.

“You do run the risk of losing money if you make the wrong decision, and that’s very difficult to predict when you’re looking at all these choices,” she warned.

The amount of light interception determines if a system will be successful or not, and Elkins found that the Tatura and parallel hedgerow systems had better light interception than the other three systems. From the fourth through the tenth leaf, the Tatura trellis and parallel hedgerow were the most productive systems, and the OHxF.69 and 97 were the most productive rootstocks in terms of gross returns. Tatura on OHxF.69 was the most productive, with acceptable fruit size.

In the thirteenth leaf, the highest-grossing combinations were the perpendicular fan on OHxF.97 and Tatura on OHxF.69, while the central leader on OHxF.513 generated the lowest gross returns.

Agricultural economists at UC-Davis created a cost-and-returns analysis for fresh-market specialty pears based on the data from the trials combined with actual f.o.b. returns. It was assumed that a standard nursery tree would cost $6.40 versus $2.50 for a sleeping eye. Pest management, irrigation, and fertilizer costs were assumed to be the same for each system.

Costs

Establishment costs for a standard orchard with 242 trees per acre were estimated at $5,328 per acre. Costs for the high-density system (Tatura with 1,244 trees per acre) would be more than double, at $13,362 per acre, because of the greater number of trees, more costly pruning and training, and more expensive harvest. Establishment costs for a high-density orchard using sleeping eyes would be intermediate at $8,628 per acre. It would cost less to plant because the sleeping eyes are cheaper, but tree losses would be higher, and more training and pruning would be required, Elkins said. Establishment would take an additional year.

The high-density system would start to produce fruit in the third year and reach maximum production by year seven, the study showed. The sleeping eyes would come into production a year later, but the peak production level would be similar. A standard planting would start to produce fruit at about the same time as the sleeping eyes, but it would take much longer to reach full production, and the maximum production would be less than in the other two systems.

Looking at accumulated net returns above operating costs, the study showed that a high-density planting would be in the black by year nine, whereas a high-density sleeping eye tree would not begin to generate a return on investment until year 14. The standard planting would never reach profitability.

Elkins said sleeping eyes are not as economically viable as full-grown nursery trees because of management problems and a higher rate of replant. She begins a trial with sleeping eyes this year.

The shorter trees in the high-density Tatura system could result in lower costs for pest management, which would make the economics of the system look even more favorable, she said, and this is ­something she would like to study further.

She concluded that a high-density orchard will pay back the grower faster than a standard planting and that the OHxF series rootstocks offer viable alternatives to the rootstocks generally used in California, such as Winter Nelis and P. betulaefolia.