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Submitted to: HortTechnology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/13/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Most soils planted with citrus in Florida are sandy and in these kinds of soils citrus roots are subjected to greater stress due to fluctuating soil moisture and other factors. There is an increased interest in using soil amendments and organic wastes in citrus sites to improve soil texture, and organic matter content. This study examined the influence a large number of soil amendments, deep-tilled at preplant in citrus plantings, had on infection of citrus roots by beneficial mycorrhizal fungi. In three plantings limestone, phosphoclay, humate, shrimp hull waste, peat, gypsum, bentonite clay, and phosphogypsum had no detrimental effect on percent infection, but none significantly improved infection. Similar observations were made in studies done in pots with citrus grown in soil amended with Glomus species and four soil amendments. Only one amendment, calcium humate, at the highest rate suppressed plant growth and fungus infection. The use of most of these amendments should be safe for development of mycorrhizae on citrus. Technical Abstract: Three sites were prepared for citrus groves in Florida from 1985 to 1986. Seven soil amendments were preplant deep-tilled 1.2 to 1.5 m deep and 1.5 m wide in the row. Treatments were limestone, phosphoclay, humate, shrimp waste, and peat. Deep-tilled controls and a no-till control were established at sites A and B and a deep-tilled control at site C. A fourth grove (site D) was planted in 1970 and included the treatments surface tillage (ST), deep tillage (DT), and deep tillage plus lime (DTL). Mycorrhizal fungus infection was determined in roots in 1987 at sites A and B and in 1989 in site C. Fungus infection ranged from 6 (no-till control) to 64% in site A; 64 to 81% in site B; and 15 to 47% in site C. In all sites, amendments did not improve percent infection, and vesicle and hyphae ratings significantly over the deep-tilled control. In site A, percent infection in the limestone treatment was the highest (64) and was significantly better than infection in phosphogypsum peat, and no-till control treatments. No treatment had a suppressive effect on infection. Mycorrhizal infection in roots was high (98 to 95%) at site D but did not differ significantly between treatments. Phosphogypsum and phosphoclay applied to soil in pots amended with Glomus intraradices and planted with rough lemon did not affect fungus infection in roots. |
