J. R. van HAARLEM, Horticultural Experiment Station, Vineland Station, Ontario
Fruitgrowers with high priced land, such as we have in the Niagara Peninsula, are not much interested in using such land for a crop not yet proven commercially sound. Plantings, whether large or small, are likely to be made on low-priced marginal land needing good care. It is doubtful if these locations are best suited to proper nut culture since most nut trees are deep rooted with extensive root systems requiring the best soils.
At the Vineland Station we have three plantations made up of 110 walnuts, 240 filberts, 14 chestnuts and 6 pecans. These comprise named varieties and seedlings of black, Carpathian, and other Persian walnuts, filberts, chestnuts and pecans.
During the first years of the life of these plantations we maintained a clean cultivation program during the spring and early summer followed by the planting of a green-manure crop about July 1st each year. Such crops as buckwheat, millet, rye, and weeds, have been used on occasion. We soon found that the treatment was not good enough for the trees and we then changed to a grass sod with mulch around each tree within the spread of the branches. Since this sod-mulch treatment was applied the trees have done very much better, making fine growth and maintaining a large leaf area of good color. This treatment is fairly representative of the many trees planted in dooryards under sod conditions, where the grass is cut and left on top.
Most of our Ontario soils are deficient in organic matter and, depending on location, deficient in phosphate or potash, or both together. The mineral deficiency should first be corrected by liberal applications of the required fertilizer before placing the plantations in sod, in fact it would pay to do this several years before setting out the trees, growing alfalfa on this land and returning all the hay back into the soil. For plantations already set out these minerals could be placed in a furrow cut just under the outer spread of the branches. Our soils have a high fixation factor for phosphate and potash and we have found that the best practice is to place the fertilizer under the surface either with a deep-placement machine or as outlined above.
After the plantation is in sod an application of 500 to 1,000 lbs. of a 4-8-10 fertilizer every fifth year should take care of the mineral requirements. However, our experience with fruit in general where planted in sod is that not sufficient care is taken to keep the trees well supplied with nitrogen, many growers laboring under the mistaken idea that just the sod is sufficient. Liberal applications of either manure or nitrate in the spring is necessary to make sure that the tree gets its required nitrogen and not just the sod alone. Mineral fertilizers should be applied in the late fall, for under our conditions fixation of phosphate and potash is considerably less at that time. The plantation may be seeded down in the early spring but mulch should not be added until late fall. Applying the mulch in late fall will allow the material to fill up with water from the fall rains and winter snows, and so prevent the serious withholding of water from the trees during dry spells in the summer, because the light summer rains are seldom sufficient to soak through the dry mulch material. We have had several instances where a summer-applied mulch has seriously robbed the tree of needed moisture during dry weather. Do not look for immediate improvement from sod-mulch, it will take at least two years to become well established. Improvement should begin to show up the second year after applying.
We sometimes see a chlorotic condition of the foliage, different from the pale yellow foliage due to nitrogen deficiency, which occurs on marginal or shallow soil and often where the soil remains too moist, as along a water course or low spot. We frequently see this same trouble on grape foliage in such locations. This is probably due to a lack of sufficient iron intake caused by a deficiency of manganese. It can be cured by either spraying with a 1% solution of magananese sulphate or applying the dry salt under the spread of the branches. The spraying method seems to give better and faster results.
It has been reported from British Columbia that some die-back is due to deficiency of boron. Perhaps some of the die-back we see on nut trees during the summer is due to this cause and not all to winter injury. The very erratic results from ground application of borax would indicate that borax should be incorporated with one of the regular sprays as a 1% mixture.
Our conclusions therefore are that nut plantations should be placed in sod as soon as possible and a mulch established the fall of the year the grass is sown. Each year cut the grass and draw in around the tree to supplement the mulch. If not enough material is gathered in this way it can be supplemented by straw or old hay. Manure or nitrate should be applied each spring and trace elements where needed can be incorporated in the regular spray program.
Discussion after J. R. van Haarlem's paper.
Dr. MacDaniels: "I realize that there are more trees which are starving to death than are being overfed."
Silvis: "Do you recommend that freshly cut hay be used as mulch?"
Van Haarlem: "Any crop refuse can be used as mulch. Anything that will rot down. The pH of the soil should be 6.2 to 6.5."
O'Rourke: "Would you use clean cultivation for the first year?"
Van Haarlem: "There is nothing against it. We use sod mulch at Vineland. The reason that our growers are not growing nut plantations is that good land, that is good soil, sells for $1,000 per acre. Nut trees grown on poor land, cheap land, do not produce."
McCollum: "I am surprised that rain would not go through loose straw and will go through old straw. Where does the rain go when it falls on the loose straw?"
Van Haarlem: "It is absorbed before it gets through the straw. Dry mulch should be 18 inches deep."
Member: "How would you prevent erosion on rolling land?"
Van Haarlem: "Plant on the contour."
Dr. Crane: "How often do you renew mulch under trees?"
Van Haarlem: "After first application additional may be needed but after that enough is grown under trees which when cut and raked will suffice."