Arbuscular-mycorrhizal colonization dynamics of cotton (Gossypium hirsutum L.) growing under several production systems on the Southern High Plains, Texas

The arbuscular-myocorrhizal (AM) colonization patterns of cotton (Gossypium hirsutum L.) growing under the range of management conditions that are employed for the production of this important crop on the Southern High Plains of Texas was examined in 1991 and 1992. Specifically, the mycorrhizal development of cotton grown under continuous center-pivot irrigation, noncontinuous linear-drive irrigation, continuous center-pivot irrigated cotton planted into terminated winter wheat, supplemental 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 more arbuscules and had higher levels of mycorrhizae earlier than any of the other production systems examined. During 1992, at 3 weeks after planting, 5 days of cold, wet weather resulted in almost 100% mortality of cotton not previously planted into terminated winter wheat. Mycorrhizal colonization levels were greater for cotton associated with winter wheat than for cotton grown under conventional practices. The higher colonization levels associated with young cotton plants that were grown with winter wheat as compared with cotton under conventional tillage practices suggests that AM-inoculum levels may have been greater before planting in the cotton + wheat management system for both the 1991 and 1992 studies. Maintenance of a hyphal network for developing cotton seedlings may be crucial for cotton to become colonized rapidly during the seedling stage. Seedling establishment on the Southern High Plains is a critical time for cotton because of abiotic stress from high or low temperatures or inadequate moisture. As a result, any benefit from the symbiosis at this time should have a positive effect on survival and subsequent yields.