| Abstract: | Soil compaction, nematode damage, and fertility problems occurring singly and in combination appear to be responsible for low yields of soybeans (Glycine max (L.) Merr.) in some Coastal Plain soils. This study was designed to determine if these conditions could be corrected with certain fertility treatments, subsoiling, and a nematicide. A field study with ‘McNair 800’ soybeans was conducted in 1972–73 on a Marlboro sand (Typic Paleudult) which had a history of poor crop production. Treatments included: 1) lime, NPK, and a micronutrient mixture (B, Mn, Mo, and Zn) lime and NPK, lime and PK; 2) subsoiling under the row and no subsoiling; 3) a nemati cide, 1, 2-dibromo-3-chloropropane (DBCP), and no nematicide. Fertility, subsoiling, and nematicide treatments made up the main, split, and split-split plots, respectively. Soil samples for nematode assay were taken at a depth of 0 to 20 cm in 1972 and depths of 0 to 20, 20 to 33, and 33 to 46 cm in 1973. In 1972, subsoiling or DBCP increased yields more than 60% over those of the control (no subsoiling and no nematicide) and subsoiling plus DBCP increased yields 11.7 q/ha or 88%. In 1973, subsoiling without DBCP did not affect yields significantly, but DBCP without sub-soiling increased yields 10.6 q/ha or 74%. Subsoiling plus DBCP increased yields 13.7 q/ha or 95%. The micronutrient mixture was the only fertility treatment which increased yields significantly, but the element(s) responsible were not identified. Lance nematodes (Hoplolaimus columbus., 1963) were numerous both years but populations were reduced in DBCP-treated plots. In the nonsubsoiled plots without DBCP, the greatest number of nematodes occurred in the 0 to 20 cm depth and populations decreased at greater depths. In subsoiled plots, there was a relatively even distribution of nematodes for depths of 0 to 20, 20 to 33, and 33 to 46 cm. Results indicate the importance of DBCP and subsoiling for soybean production on compacted soils infested with lance nematodes. |
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