A rain-covered orchard is also netted against cherry fly for organic cherry production. The additional black net serves as a windbreak.
Three hectares of covered cherries on Gisela 5 rootstocks. The cover is the Frustar Braendlin system with bird protection.
Rain covers on cherry orchards can increase the value of the fruit and improve the overall profitability of an orchard, Dr. Martin Balmer, horticulturist at the Rheinland-Pfalz Research Station, Germany, reported at the International Fruit Tree Association’s annual conference. Typically, orchards in the Rheinland district of western Germany receive almost half an inch of rain during the growing season, but only a small proportion of Germany’s cherry orchards are covered because of the cost, he said.
Rain covers have been available commercially for about the past 12 years. Germany now has about 125 hectares (about 300 acres) of cherries under cover. Elsewhere in Europe there are about 270 hectares (667 acres) of covered cherries, of which about 100 (250 acres) are in the United Kingdom, he estimated.
Balmer has studied how covers can affect a cherry orchard, apart from reducing fruit splitting. When an orchard is covered in the spring, frost damage can be significantly reduced. Under a cover, the light is less intense, which leads to more vegetative growth. The difference in light levels in covered and noncovered orchards is greatest during sunny weather.
In a 2008 study in a Regina orchard, Balmer noted a tendency for the shoots and internodes to be longer in the covered blocks and for the sugar content of the cherries to be slightly lower than in uncovered orchards. However, buyers prefer covered cherries, he reported. "Dealers who buy those cherries say they’re better quality, they’re more shiny and bigger, and equal color, and they hold much better in the store than standard cherries."
Balmer compared wholesale prices of Regina cherries from uncovered orchards with prices for covered cherries during each of the years 2005, 2006, and 2007. Uncovered cherries sold for between 2.15 and 2.51 euros per kilo (U.S.$1.29 to $1.51 per pound), while covered cherries sold for between 3.93 and 5.62 euros per kilo (U.S.$2.36 to $3.37 per pound). In 2007, prices for covered cherries were more than double those of uncovered.
Types of covers
Several different types of rain covers are available in Germany. The cheapest, at about 3.50 euros per square meter (U.S.$0.43 per square foot), is a single-row cover designed to be installed during ripening time when the fruit is susceptible to cracking. Though the cheapest to buy, it is difficult to install and requires more labor than other covers to put up and take down each year. Permanent covers have the advantage of reduced labor inputs, but, on the down side, less light reaches the trees and the planting needs to be irrigated.
Balmer made an economic comparison of a covered cherry block and an uncovered block. He assumed that the life of the orchard would be 15 years. The covering would be used from the fourth year and would be used twice each season, first on early maturing varieties and then on later varieties. The cover would require 180 hours per hectare per year for handling.
He assumed that the wages would be 7 euros per hectare (U.S.$9.25) for seasonal workers and 15 euros per hectare (U.S.$19.81) for permanent workers. The trees were on Gisela 5 rootstocks and planted 4 by 2 meters (13 by 6.5 feet) apart. Yields were estimated at 3 tons per hectare (1 ton per acre) in year three, reaching peak production of 12 tons per hectare (5 tons per acre) in year eight.
For the uncovered orchard, he assumed an average selling price of 2 euros per kilo (U.S.$1.20 per pound) for the fruit and 10 percent decayed fruit. Hail insurance would be required at a cost of 8 percent of returns.
For the covered orchard, he assumed a selling price of 3.50 euros per kilo (U.S.$2.10 per pound) and only 2 percent decay. It would require an annual investment of 1,000 euros (U.S.$1,320) for repairs to the cover.
His analysis showed that both orchards began to generate a return on investment in the tenth year. However, in subsequent years, the covered orchard was significantly more profitable and by the 15th year had a capital value of around 60,000 euros (U.S.$79,000) versus less than 20,000 euros (U.S.$26,400) for the uncovered.
When Balmer compared different covers, he found that the cherry block with the cheaper cover generated an earlier return on investment and achieved a slightly higher capital value after 15 years than a more expensive cover, despite the higher labor costs. Covers with plastic that needed to be replaced during the life of the orchard reached profitability later and had a lower capital value after 15 years than the other systems.
A rain cover can be used in combination with nets along the sides to enclose the orchard and keep insects out.
Balmer also studied the idea of growing cherries in a greenhouse that would be heated starting in January and would produce cherries in April for the high early market. However, tonnage was very low, and costs were high because of the high cost of oil for heating, he said.
Experiments using insulated plastic tunnels looked more promising because of higher fruit loads. Fruit ripened 12 to 19 days earlier than in standard orchards, fruit size was larger, and firmness was about the same. He believes high returns for early cherries might cover the cost of the tunnel.