Some physical parameters in relation to water extraction by roots of two pigeonpea genotypes
 
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National Cereals Research Institute, P.M.B. 8, Bida, Niger State, Nigeria
 
Int. Agrophys. 1996, 10(1): 11–19
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ABSTRACT
In modeling water extraction by roots and in whole crop modeling, careful selection of the factors for their parameterization which could differ from genotype to genotype is a prerequisite. Some physical parameters of soil hydraulic resistance, root conductivity, root length density, yield and some yield components in relation to water extraction by roots of two pigeonpea genotypes (ICPL 87 and ICP 1-6) were investigated in the field. Soil hydraulic resistance was found to be negligible in the upper soil layers but concentrated where there was maximum root length density along the profile. Lower soil hydraulic resistance and higher rate permeability was exhibited by ICPL 87 (short duration) than in the medium duration pigeonpea, ICP 1-6. Root permeability was found to be closely associated with the position of the root front, soil moisture status and age of the plant. The most effective part of the root front for water extraction was found to be determined by the degree of aeration at that zone. Higher plant density, lower soil hydraulic conductivity, and higher root conductivity resulted in higher water extraction by ICPL 87 than for ICP 1-6 when moisture was adequate. Higher water extraction rate by root of ICP 1-6 than ICPL 87 under drought or water stress condition was associated with higher specific leaf area of ICP 1-6 than the latter. The results also indicated an inverse relation between total profile water extraction rate and the total root length density. The extraction rate was directly linked with precipitation. The genotype, ICPL 87 produced higher grain yield than ICP 1-6.
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