ARBUSCULAR-MYCORRHIZAL COLONIZATION DYNAMICS OF COTTON (GOSSYPIUM-HIRSUTUM L.) GROWING UNDER SEVERAL PRODUCTION SYSTEMS ON THE SOUTHERN HIGH-PLAINS, TEXAS

The arbuscular-mycorrhizal (AM) colonization patterns of cotton (Gossy pium hirsutum L.) growing under the range of management conditions tha t are employed for the production of this important crop on the Southe rn High Plains of Texas was examined in 1991 and 1992. Specifically, t he mycorrhizal development of cotton grown under continuous center-piv ot irrigation, noncontinuous linear-drive irrigation, continuous cente r-pivot irrigated cotton planted into terminated winter wheat, supplem ental dryland, strict dryland, and supplemental dryland cotton planted into terminated winter wheat was evaluated. During 1991, colonization levels were highest for cotton planted into terminated winter wheat. Furthermore, cotton planted into terminated winter wheat developed mor e arbuscules and had higher levels of mycorrhizae earlier than any of the other production systems examined. During 1992, at 3 weeks after p lanting, 5 days of cold, wet weather resulted in almost 100% mortality of cotton not previously planted into terminated winter wheat. Mycorr hizal colonization levels were greater for cotton associated with wint er wheat than for cotton grown under conventional practices. The highe r colonization levels associated with young cotton plants that were gr own with winter wheat as compared with cotton under conventional tilla ge practices suggests that AM-inoculum levels may have been greater be fore planting in the cotton + wheat management system for both the 199 1 and 1992 studies. Maintenance of a hyphal network for developing cot ton seedlings may be crucial for cotton to become colonized rapidly du ring the seedling stage. Seedling establishment on the Southern High P lains is a critical time for cotton because of abiotic stress from hig h or low temperatures or inadequate moisture. As a result, any benefit from the symbiosis at this time should have a positive effect on surv ival and subsequent yields. (C) 1998 Elsevier Science B.V.