Cultivar and planting date effects on soybean root growth

Abstract

To avoid late summer drought, soybean [Gylcine max (L) Merrill] producers in many southern and border states of the USA modify their cropping systems. Options include use of unadapted cultivars and changing planting dates. Because root function is important to plant health and yield, this study was conducted to determine if planting date and soybean cultivar affect root growth and distribution. Seeds of one cultivar from each of four maturity groups (MG III, IV, V, and VI) were sown in mid-April, mid-May, and mid-June in 1992 and 1993 on a Tiptonville silt loam near Portageville, MO. Root observations were performed 30 and 60 days after emergence (DAE) using a minirhizotron system. Cultivars differed for root length density (RLD) only in the 15 to 28 cm depth in 1992 and in the 15 to 28 cm and 29 to 42 cm depths in 1993, but differences were not related to maturity classification of cultivar. Average RLD was 1.02 cm -3 for MG III and IV cultivars and 1.21 cm cm 3 for MG V and VI cultivars. Average RLD for the mid-June planting date was 1,65 cm cm -3 but only 0.73 cm cm -3 for the mid-April planting date. An increase in RLD between 30 and 60 DAE occurred at all soil depths. For both years, MG V and VI cultivars produced higher yields than the MG III cultivars. Earlier than normal planting dates inhibited early root growth, but did not reduce yield. Cultivars differed only slightly for the rooting characteristics measured in this study. These rooting characteristics may not be important criteria for cultivar selection.Abbreviations: M G -maturity group, V C R -videocassette recorder, D A E -days after emergence, R L D -root length density, CRLD-change in root length density.

Characterization of a soybean (Glycine max L. Merr.) germplasm collection for root traits

“…However, maturity groups did not influence any root traits [P-values for the effect of maturity groups on total root length, total root surface area, total root volume, average root diameter, fine root length, and fine root surface area were 0.72, 0.54, 0.35, 0.06, 0.74, and 0.51, respectively, and for root penetration, 0.19 (Run 1) and 0.89 (Run 2)]. Similar observations were made by Turman et al [ 56 ], who observed that root length density (total root length in unit soil volume) of soybean was not related to maturity groups under field conditions.…”

Effect of Planting Date on Soybean Growth, Yield, and Grain Quality: Review

“…Considering the importance of root function to soybean plant growth, Turman et al (1995b) found that mid‐May planted soybean in Missouri had more extended root depth at 30 d after emergence than mid‐June and early July planting. Another experiment conducted by Turman et al (1995a) indicated that earlier than normal planting date of four maturity groups (MG III, IV, V, and VI) soybean inhibited early root growth, but did not reduce yield, suggesting that the root may not be an important factor in cultivar selection.…”

Effect of Sowing Date and Cultivar on Root System Development in Pea (Pisum sativum L.)

“…This result is consistent with the findings of Tsegaye et al (1995), who estimated a root elongation rate of the main root axis of between 0.015 and 0.021 m day )1 and those of Tricot et al (1997), who reported a root elongation rate of 0.022 m day )1 . Pea RSER was within the range of variation observed for winter wheat, for which an RSER of 0.012 m day )1 has been observed ( Barraclough and Leigh, 1984) and soybean, for which RSER has been reported to vary from 0.004 to 0.013 m day )1 (Turman et al, 1995).…”

“…Thus, changes in crop management (particularly the sowing period) should make it possible to increase pea root depth and reduce the risk of water stress at the end of the cycle, as shown for soybean (Taylor, 1980), potentially increasing yield stability and seed protein content. The effects on root development of seasonal variations in temperature and radiation due to spring or autumn sowing have never been compared as most previous studies (Barraclough and Leigh, 1984;Vincent and Gregory, 1989b;Turman et al, 1995) have compared root growth and development in field conditions for different sowing dates in the same season only. The effect of highly contrasted sowing dates (autumn and spring) has yet to be investigated in field conditions.…”