Response of mamey sapote (Pouteria sapota) trees to flooding in a very gravelly loam soil in the field

Abstract

Mamey sapote trees are periodically subjected to flooding in southern Florida but their flood-tolerance is not known. ‘Magaña’ mamey sapote (Pouteria sapota) trees were planted on 11 May 2006 in the field in mounds of Krome very gravelly loam soil at the Tropical Research and Education Center in Homestead, FL. Before planting, the soil was scraped to the bedrock, and a water-resistant tarp and plastic sheet (barrier) was placed on the bedrock. Native soil was mounded on each barrier for each tree. The barrier edges were raised above the soil surface to form a pool so that trees could be individually flooded. The response of trees to flooding was tested in two separate trials on 6 Nov. 2006 to 9 Jan. 2007 (Fall–Winter) and 23 Apr. to 11 June 2007 (Spring–Summer). Trees were divided into control (nonflooded) and flooded treatments. In the Fall–Winter Trial, flooding resulted in leaf epinasty after 2 weeks and reductions in net CO₂ assimilation (A) after 3 weeks; however, leaf abscission was not higher for flooded trees than nonflooded trees. By the end of 70 days of flooding, only one tree (12%) died. In the Spring–Summer Trial, A was significantly lower for flooded trees than nonflooded trees by the beginning of week 2. By the end of week 4, four out of eight flooded trees had no leaves and one had wilted leaves, while three trees were still in good condition. Six of the flooded plants were infected with Pythium splendens root rot, which was likely the cause of death. Therefore, mamey sapote appears moderately tolerant to flooding in a very gravelly loam soil. However, more work is needed to separate tree decline due to flooding from that due to P. splendens infection in this soil.