Factors which affects the growth of grain legumes on a solonized brown soil. I. Genotypic responses to soil physical factors

摘要

Lupins (Lupinus angustifolius cvv. Yandee and 75A-258 and L. pilosus cv. P. 20957) and pea n(Pisum sativum cv. Dundale) were grown in the field for 43 days on a solonized brown soil. nShoots of L. pilosus and peas grew most rapidly, while L. angustifolius cv. 75A-258 developed na relatively large root system. L. angustifolius cv. Yandee, a commercial lupin cultivar, was npoorly adapted; shoot growth was restricted and roots ceased growing 36 days after sowing. nThe soil factors responsible for these widely differing responses were investigated. nOnce primary roots of L. angustifolius were 20-30 cm deep, root extension was slow nor arrested. Indeed, primary root apices of Yandee were often necrotic in the soil below n20 cm. In contrast, roots proliferated rapidly in the surface 20 cm of the soil, particularly nin 7SA-258, suggesting that factors in the deeper soil layers restricted root growth most nseverely. The vigorous growth of lateral roots of 75A-258 was reflected in a 2 .&fold greater ntotal root length than for Yandee 43 days after sowing. nSoil physical properties were not considered a likely explanation for these observations; nsoil water status and porosity were always favourable for root growth and root sections nindicated that no cortical degradation, typical of 02 deficient roots, had occurred. nPenetrometer resistance and root tip osmotic pressures suggested that poor root growth ncould not be ascribed simply to soil mechanical properties. The results suggest, by inference, nthat soil chemical factors could underlie the phenotypic responses observed.