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Cotton Root Growth and Soil Water Extraction
Author(s) -
Bland William L.,
Dugas William A.
Publication year - 1989
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1989.03615995005300060039x
Subject(s) - lysimeter , loam , soil water , environmental science , extraction (chemistry) , water content , neutron probe , water extraction , soil horizon , growing season , soil science , mollisol , agronomy , chemistry , geology , biology , neutron , neutron temperature , neutron cross section , physics , geotechnical engineering , chromatography , quantum mechanics
The inherent productivity of many fine‐textured soils depends on timely extraction of water stored deep in the profile. Growth of crop roots and their ability to extract water are of central importance to efficient utilization of these soil resources. We observed the rate at which the soil volume was explored and water was extracted by cotton ( Gossypium hirsutum L. ‘GP3774’) roots in a fine‐textured soil in a subhumid environment. Measurements of root growth and water extraction were made for 2 yr in a 2.3 m deep weighing lysimeter, 3.0 m 2 in area and containing an intact core of a Frio taxadjunct silty clay loam (fine, montmorillonitic, thermic Cumulic Haplustoll). Water extraction was measured with neutron probes at 10 or 11 soil depths in the lysimeter at approximately 5‐d intervals. Root length density [ L v , cm root (cm 3 soil) −1 = cm −2 ] was estimated at 7‐d intervals by counting roots visible against clear observation tubes installed horizontally in the lysimeter every 0.2 m between 0.5 and 2.1 m. Depth of rooting increased up to 35 mm d −1 for part of the season. Maximum L v at 0.5 m was 1.5 and 0.8 cm −2 in 1984 and 1985, respectively; at 2.1 m comparable values were 0.24 and 0.04 cm −2 . When the lysimeter surface area was divided into six 0.5‐m 2 regions of soil, the coefficient of variation in L v among the regions reached 100% both early and late in the season and both at 0.5 and 2.1 m. Crop rows did not affect the spatial distribution of L v at depths measured. Growth of the root system required about 90 kg ha −1 d −1 for part of the season. Maximal water uptake rate per length of root was approximately 5 mm 3 water (mm root) −1 d −1 and occurred at 1.7 to 1.9 m. Redistribution of dry matter invested in roots near the soil surface to deeper in the profile would probably increase total water extraction by the crop.