Root lodging in sunflower. Variations in anchorage strength across genotypes, soil types, crop population densities and crop developmental stages

SPOSARO, M. M., CHIMENTI, C.A., HALL, A. J.

FIELD CROPS RESEARCH

Elsevier Science BV

Lugar: Amsterdam; Año: 2007 vol. 106 p. 179 - 186

0378-4290

PROOF Abstract Root lodging is an important adversity affecting sunflower (Helianthus annuus L.) production in Argentina under current husbandry practices, and may limit progress towards the achievement of higher yields via increased plant population density. Although there are perceptions that lodging susceptibility varies across developmental stages, crop population densities, genotypes and soil types, these perceptions have not been tested for sunflower using a standardized experimental protocol. This study aimed at: (1) identifying the sources of the variation in root lodging susceptibility in response to variations in crop population density in two genotypes of reputedly different susceptibility; (2) detecting the crop developmental stages most susceptible to root lodging; and (3) examining the relationships between root failure moment, root plate diameter and soil shear strength. We mechanically induced lodging at three developmental stages in plants rooted in pre-wetted plots. The crops were grown at 5.6 plants m2 over 3 years on either Typic Argiudoll or Typic Hapludoll soils and at 3, 5.6, 10 and 16 plants m2 on a Typic Argiudoll Q1 . The force needed to induce root lodging (root failure moment) and root plate diameter varied across genotypes, plant densities and developmental stages. Root failure moment and root plate diameters were greater ( p < 0.05 for both variables) in the resistant hybrid across the three development stages and almost all crop population densities. For both hybrids, the most susceptible development stage was R2, and root failure moment and root plate diameter diminished ( p < 0.05) as crop population density increased. Although root failure moment did not differ between soil types, root plate diameter was greater ( p < 0.0001) in the coarser soil. The relationship between root failure moment and the product of root plate diameter cubed by soil shear strength (a measure of plant anchorage strength) for both hybrids, both soil types, and all crop population densities could be described by a single linear relationship (y = 0.2382x; R2 = 0.812; p < 0.025). # 2007 Published by Elsevier B.V. Keywords: Root lodging; Sunflower; Root failure moment; Root plate diameter; Helianthus annuus L.