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?"