Root Distribution Patterns of Two Hybrid Grain Sorghums Under Field Conditions¹

Abstract

Senscence is sorghum [Sorghum bicolor (L.) Moench] is manifested as pre‐mature shedding of the lower plant leaves. This process occurs during grain filling and is much more pronounced in senescent than in nonsenescent cultivars. Since roots are the plant organs responsible for water and nutrient accumulation, it is important to understand their relationship to total plant development. The root development of a senescent and a nonsenescent hybrid grain sorghum was investigated in the field. The purpose of this investigation was to determine the influence of senescence on root distribution of two grain sorghum hybrids. Root samples were collected on approximately biweekly bases to measure their rate of growth and extent of distribution. Samples were collected on both sides of, and perpendicular to the row at 5‐, 15‐, 22.5‐, and 30‐cm intervals to a depth of 105 cm. Root distribution and density were similar for each hybrid 3 weeks after planting (3 June). The nonsenescent hybrid, represented by ‘ Pioneer 42004’, established its aventitious root system earlier than did the senescent hybrid, represented by ‘Pioneer 22516’. Differences were based on visual inspection of the roots and root diameter measurements. Root density of both hybrids increased until grain filling with the senescent cultivars generally exhibiting greater root density. From week 11 (5 August) to week 13 (19 August), both hybrids decreased in root density with a greater decrease noted for the senescent hybrid. The more dramatic decrease in density for the senescent hybrid was also reflected in a lesser grain yield.

Sorghum root length density and the potential for avoiding striga parasitism

“…The R L D found in this study was within range of but generally less than for field grown corn (0.1 to 4 c m c m 3, Mengel and Barber, 1973), or that of sorghum grown in 155 liter lysimeters (0-25 cm cm -3, Merrill and Rawlings, 1979) which had a depth of 108 cm. Root length density here was much greater than that reported for commercial sorghum hybrids grown in the field (0.001-0.03 cm cm -3, Zartman and Woyewodzic, 1979). In the USA field trials the R L D of the resistant lines, Framida and P-967083 were significantly less than that of the susceptible Dabar in the first 10 cm of the soil core (Table 2).…”

The Influence of Sorghum‐Sudangrass Roots on Nutrient Leaching1

“…The effectiveness of the sorghum-sudangrass roots in reducing nutrient leaching is evident from the above discussion. Other hybrids may have different root distribution, as reported by Zartman and Woyewodzic (1979). Sorghum-sudangrass roots appear to be more efficient than corn roots relative to nutrient uptake.…”