02108nam a2200217 a 450000100080000000500110000800800410001910000220006024500590008226000370014130000110017850000190018952015440020865000110175265000090176365000090177265300140178165300360179565300380183165300210186913273012002-11-22       1988    bl uuuu  m   00u1 u    #d1 aFREITAS, P. L. de  aEffects of soil structure on root growth and function.  a[S.l.]: Cornell Universityc1988  a213 p.  aTese Doutorado  aSoil physical properties affecties effect plant growth, by providing the conditions for root growth and function. The effect of soil structure, recognized as one the most important physical properties of soil, on plant growth is reviewed. In order to better understand how soil structure and other related properties affect root growth and function, soil physical and plant physiological aspects are discussed. Some questions are raised about the validity of explaining differences in crop yield by the evaluation of soil productivity and tillage systems using macroproperties, such as soil density and mechanical impedance. It is suggested that the best characterization of a soil is based on microproperties, such as pore-size distribution and size, density, strength,and stability of aggregates. To validate this hypothesis a method was developed to simulate soil aggregates of different size and density. A silty soil was prepared and compressed to densities of 1.4, 1.6, and 1.8 Mg. m3, shaped to different cubical sizes (25 and 50 mm sides), and placed face-to-face in soil columns 25 cm high and 20 cm in diameter. A main check treatment was included to simulate field conditions. In these artificial, homogeneous soil columns, corn (Zea mays L.) plants were grown for 33 days. Plant behavior was determined by characterization of shoot and root growth. Shoot dry weight, leaf area, and shoot apex height were measured at the end of the growth period. From the soil columns, final density of soil and aggregates were determined. ...  aManejo  aRaiz  aSolo  aEstrutura  aSistema radicular - crescimento  aSistema radicular - funcionamento  aSolo - estrutura