Distribution and Growth of Sorghum Roots in Response to Irrigation Frequency

Merrill, S.D. and Rawlins, S.L. (1979) Distribution and Growth of Sorghum Roots in Response to Irrigation Frequency. Agronomy Journal, 71 (5). pp. 738-745.

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Root growth responds to alterations in timing and distribution of irrigation. In order to better understand crop response to irrigation regime, basic information is needed on the response of root growth, and in particular, root distribution, to differences of irrigation frequency. The lysimeter experiments reported here were designed to observe the growth of sorghum roots under conditions where soil temperature and bulk density were nearly invariant in time and over soil depth. Grain sorghum (Sorghum bicolor (L.) Moench) was grown on Pachappa sandy loam soil (mixed thermic, coarse loamy, mollic Haploxeralf) in lysimeters with artificial lighting. Three irrigation frequencies were used. Soil strength was measured with a constant rate penetrometer on undisturbed cores from the lysimeters. Root length density was measured on soil samples taken five times during 76 to 79-day growth periods. The relation between penetrometer soil strength (PSS) and matric potential (Ψ) was PSS = 3.717 - 21.52 Ψ (PSS in kg.cm-2, Ψ in bars), and for Ψ < -0.54 bar, PSS = 19.77 + 16.63 log10 (-Ψ). PSS, averaged over 12 to 14 day periods, differed by up to 20 kg.cm-2 from the upper to lower part of the profile in the least frequently irrigated treatment, in which part of the profile dried to -10 bars or less. In contrast, PSS variation with depth was no more than 2 kg.cm-2 under daily irrigation. While root penetration was as deep in the profile in all three treatments, root length density (cm . cm-3)was proportionally less in the upper profile of the less frequently irrigated treatments. The centroids of root length density profiles were located at a 10 to 15 cm higher depth under daily irrigation than under the least frequently irrigated treatment. Root length and dry weight yield were 20% to 30% higher under daily than under intermittent irrigation. The difference between growth in the least frequently irrigated treatment and that in the daily-irrigated at given depths correlated significantly with average PSS and logaveraged matric potential. Within a given treatment there were almost no significant correlations between percentages of root growth at various depths and average PSS or log-averaged matric potential. The relation between root growth and soil depth itself apparently obscurred these relations. It is concluded that PSS measurements, along with measurements of water, salt, and 0, status, will prove useful for interpreting the response of root growth to alteration of irrigation regime

Item Type: Article
Uncontrolled Keywords: Soil strength, Penetrometer, Root length, Soil matric potential
Author Affiliation: Soil Scientist, Northern Great Plains Research Center, USDA-SEA-AR, P. 0. Box 459, Rfandan, ND 58.554
Subjects: Plant Production
Divisions: Sorghum
Depositing User: Ms K Syamalamba
Date Deposited: 06 Jan 2012 05:18
Last Modified: 06 Jan 2012 05:18
Official URL: http://dx.doi.org/10.2134/agronj1979.0002196200710...
URI: http://eprints.icrisat.ac.in/id/eprint/2921

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