International audience | SUMMARY. Front the study of sample plots situated in the north-east, theeast ant the center of France; the following provisory conclusionscan be drawn.1° The Douglas is a fast growing species which can reach a highproductivity, greater than the one that can be expected from ourindigenous conifers: the annual increment being as much as 30 or40 cubic meters — total volume — per hectare and per year.2° This high productivity can only be expected in favourable ecologicalconditions.3° From the climatic stand point, the Douglas proves to be anaccomodating tree susceptible of thriving and giving large yieldsunder a wide range of climates, and even in the mountains underalready rather severe conditions. In this respect the question of thewater requirements of the plant is capital.4° Like all the species growing vigorously and quickly, the Douglas is particularly sensible to the edaphic conditions. It prefers arich, deep, porous and cool soil which induces an unusual growthand high yields.5° Its rather shallow rooting; exposes it to wind-storms, chieflyif the ground on which it grows is not deep (rocky bed or layer ofGley forcing it to develop a shallow root system) and if the soilis temporarily softened by rain.6° The Douglas must not be planted too closely — 3 000 plantsper hectare seems quite sufficient. A greater number is not onlyexpensive but detrimental.7° Being a fast-growing species the Douglas requises a sufficientgrowing space. It fears the competition of its associates and in itsyoung, age, that of the other species.It is particularly sensible to repeated thinnings. Too rare or toomoderate thinnings are immediately followed by a considerable. decreasein the yield.8° It would not be reasonable to maintain a dense stand with aview to favour natural pruning. In any way, the Douglas does notprune well naturally.On the contrary a careful artificial pruning is advised. It is profitable,for it corresponds to an important increase in the qualityof the products. 9° The question of productivity being put apart a great densityof the forest does not favour the elongation of the stems. The heightof the mean tree seems to be independent of this density-.Inversely, a moderately 'dense stand brings about an increase ofthe girth and consequently, interesting marketable products may beobtained earlier.10° The question of the races plays centainly a part in the possibilitiesof introducing the species under varied conditions, but perhapsalso from the stand point of mere productivity.11° The use of « slow » volume tables established by L. SCHAEFFER,seems more suitable, for the determination of the volume ofstanding trees, than that of the ALGAN tables.12° If the Douglas is to be introduced in mixture with otherconiferous species growing less quickly (particularly with indigenousconifers), it must be considered than the Douglas outgrowsits competitors rapidly and completely. A mixture in alternate rowsor alternatively in each row is not at all recommended. The secondaryspecies will disappear 'rapidly without any profitable productand its only use will have been to hamper the Douglas in its growth.A mixture in groups will be better or the Doug-las will be scatteredin small groups widely apart from one another (8 to to meters)in the middle of the secondary stand.13°' The proportion of bark in the volume of the standing treesit about 10 per cent.14° The experiments undertaken have shown the importance ofthe « border effect » and the usefulness of an efficient shelter almgthe edge exposed to the wind.(Traduction M. Grosdidier.)

One of the classic examples of plant response to Cu is found in the vast area of organic soils of Peninsular Florida. Most crops failed to grow on these soils until the middle 1920's when the need for Cu was first demonstrated. Tremendous growth response of various leafy vegetables, cruciferous plants, root crops, eggplant, tomatoes, and certain forage crops have been obtained with initial applications of 50 pounds an acre of copper sulfate. In recent years it has been found that copper oxide is at least as effective as copper sulfate in supplying sufficient copper for maximum plant growth. Results of greenhouse tests indicated that either source is as effective when added to the soil in mixed fertilizer as when added separately. Further work showed that plant response to Cu on virgin peaty muck soil was the same whether 12 or 24 pounds of Cu per acre was applied. A field experiment comparing two rates of copper oxide and copper sulfate showed the effects of plant varietal differences with respect to Cu deficiency symptoms. Southland oats and ryegrass were seeded in the test area where St. Augustinegrass cuttings had been planted. Copper deficiency symptoms of oat plants growing on the no-Cu plots were much more pronounced as indicated by reduced yields and chlorosis than were the symptoms for ryegrass. Copper contents of the oat plants were lower for the no-Cu plots but no differences were noted for plants treated with the oxide or sulfate at 12 or 24 pounds of Cu. St. Augustinegrass and pangolagrass (fertilized in a similar manner) showed similar findings. Copper analyses of various forages grown in the greenhouse with additions of 1,000 pounds of copper sulfate per acre, indicated that St. Augustinegrass, caribgrass, and paragrass, absorbed more Cu than bahiagrass, fescuegrass and “giant” pangolagrass. Copper contents of red clover and subterranean clover growing in the field, were significantly greater than ryegrass, oats, vetch, alfalfa, and hubam clover. Copper contents of forages taken from various soils in the area indicated that Cu deficiency, per se, of cattle should not be widespread in this area under proper fertilization, including Cu additions.

This is a continuation of an experiment conducted at the Virginia Truck Experiment Station in 1948³ to determine the influence of acid and neutral fertilizers on the soil reaction in the potato row during the growing season. Results from the 1948 study indicate that fertilizers applied in bands in the potato row had a marked influence on lowering the soil reaction, and that the degree of this influence was dependent upon where the sample was taken with respect to the fertilizer bands. The purpose of this study was to determine whether fertilizer materials might differ in their influence on the soil reaction, with some possibly being more effective than others in reducing the pH of soils where there was danger of scab. A commercial 5-10-5 fertilizer was used for treatment 1, and hand mixed materials were used for the other five treatments. In treatment 2, all the nitrogen was derived from NH₄NO₃, while in treatment 3, it was derived from (NH₄)₂SO₄. In treatments 4 and 5 the nitrogen was derived from NH₄NO₃, and 50 and 100 pounds of sulfur, respectively, were added per ton of fertilizer. All of the treatments were applied at the rate of 2,000 pounds per acre except treatment 6 where the fertilizer mixture was applied at the rate of 3,000 pounds per acre. Soil samples were taken 2, 4, 8, and 12 weeks after planting at certain locations around the band. Phosphorus, potassium, pH, nitrate and conductivity tests were run on all samples. The six fertilizer mixtures markedly lowered the soil reaction in the potato row during the 1949 and 1950 growing seasons. This influence varied with the sampling location or position of the soil sample with respect to the fertilizer bands, with the greatest influence being exerted above the bands. The lowering of the pH was associated with increases in salt concentration in nitrates and in potassium. There was no important differences in the influence of the six different mixtures on the soil acidity except where the soil samples were taken from the fertilizer bands.³Dunton, E.M., Jr. et. al. Agro. Journ. 42:512 (1950).

The relationship existing between the effects of potash fertilizers, physical and chemical properties of the soils and moisture tension treatments on the yield and potassium and sodium uptake by sugar beets in south central Montana have been studied. Small sugar beet yield increases due to potash fertilizer were obtained on calcareous soils containing quantities of exchangeable potassium much in excess of what is usually thought to be adequate for maximum growth (i.e., from 0.82 to 1.79 m.e. per 100 grams soil). Another experiment having moisture tension variables was conducted on a soil with relatively few large pores particularly at the 6 inch depth. Late in the season, sugar beets growing on low tension treatments showed evidence of potassium deficiency and petioles contained 31% less potassium than petioles from high tension treatments. Since yield increases due to potash were obtained on soils with a very few large pores and maintained at low moisture tensions, it is suggested that poor soil aeration was a major factor contributing to the low potash availability. The lack of any relation between potassium uptake and the amounts exchangeable also may suggest that potassium absorption was dependent on soil aeration.