Cotton and Corn Root Development in Two Field Soils of Different Strength Characteristics
1975
Many agriculturally important soils in the San Joaquin Valley, being compact and of high strength, may pose special problems in water management. The higher than normal frequency of irrigation often required to meet evapotranspiration demand suggests that plant root development has been limited. This study was conducted to determine the influence of high penetrometer soil strength, found naturally occurring in the field, on the root development of cotton (Gossypium hirsutum L.) and corn (Zea mays L.). Additional objectives were to determine if root distribution could be influenced by planting geometry and density, and to relate soil water depletion to observed root density (cm of root/cm³ of soil). Cotton and corn plots, having a variable row width and plant density, were established on each of two field soils that differed considerably in strength as measured with a recording soil penetrometer. Root densities of the two crops were related to the independent variables penetrometer strength (measured in situ), and soil depth m a regression model that accounted for 75% of the observed variation. A high-density plant population of cotton caused higher root densities in the 30 to 122 cm-depth zone in a low-strength soil than that with normal plantings. A linear relation between water depletion and root density indicated average water uptake values for fully transpiring corn and cotton to be respectively 2.33 × 10⁻ᵃ and 7.86 × 10⁻⁸ cm⁸/cm/day. Field measured soil strength was effective for diagnosing or predicting mechanical root growth restrictions of well drained soils.
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