NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 49 



Analysis of various crops shows that plants remove from the soil 

 at least 10 chemical elements. These are nitrogen, phosphorus, 

 potassium, calcium, magnesium, sulfur, sodium, iron, chlorine, and 

 silicon. Voorhees and Haskell (40, p. 3) state that many plants can 

 grow to maturity without sodium, silicon, and chlorine, but that the 

 other elements obtained from the soil must be present for norma] 

 growth. Additional elements found include manganese, carbon, 

 hydrogen, and oxygen, the last 3 obtained from the air or water. 



More recent developments in the field of soil chemistry indicate 

 that boron, copper, and zinc are necessary for normal development 

 of plants and some startling results have been obtained with certain 

 soils and crops by very light applications of chemicals containing 

 these elements. Remarkable increases in yield and reduction of 

 disease occurred in a number of instances. 



All the evidence at hand indicates that the so-called minor elements 

 may be very important in some cases, and it is confidently expected, 

 as more field experiments are performed and better methods of 

 quantitative analysis developed, that their true role in plant growth 

 and disease resistance will be brought to light. 



The functions of the various elements in the growth of a plant are 

 numerous and complex. Van Slyke (39, pp. 48-55) states that 

 nitrogen promotes growth of foliage and stem, gives leaves a dark- 

 green color, and acts as a food reserve; phosphorus stimulates germi- 

 nation, increases root development, and is vitally necessary in seed 

 production; potassium aids in formation of carbohydrates, is impor- 

 tant in transference of starch from one part of the plant to the other. 

 and increases seed production. Lime in moderate amounts increases 

 availability of phosphorus, prevents excess acidity, stimulates 

 growth, improves tilth of fine-textured soils, and has an ameliorating 

 effect on toxic substances in the soil. If present in excessive amounts 

 it may reduce availability of iron and manganese, resulting in 

 chlorosis. 



it is a well-known fact among nurserymen that an excess of nitrogen 

 in readily available form causes undesirable succulence and top- 

 heaviness in plants, decreases drought resistance, and increases sus- 

 ceptibility to fungus diseases. The beneficial effect of superphosphate 

 fertilizers in stimulating root development and developing well- 

 balanced, drought-resistant nursery stock is becoming generally 

 recognized. 



In most soils, if nitrogen, phosphorus, or potassium, or sometimes 

 calcium or sulfur, are sufficiently depleted, plant growth will be 

 influenced. In the soils of the prairie-plains region, potassium, cal- 

 cium, and sulfur are invariably present in adequate amounts, but in 

 some instances nitrogen, phosphorus, and iron may be so low that, for 

 optimum growth of the seedlings, corrective measures may be required. 

 This is especially true of phosphorus, because this element is the one 

 which is most likely to be the limiting factor in production of drought- 

 hardy planting stock. It is believed that lack of sufficient manganese 

 in some plains soils accounts for chlorosis in nursery stock, but to 

 date this has not been proved experimentally. 12 



: - At the Woodward, Okla.. field station of the Bureau of Plant Industry, experiments by I.. F. Locke 



are reported as indicating that lack of availahle iron is the critical factor, and that chlorosis in nursery stock 

 may in most instances be corrected by the application of iron sulfate. 



297878° — 41 i 



