| Summer drought is a major yield limiting factor for soybean [ Glycine max (L.) Merr.] in the mid-South. A crop that matures by mid- to late July is required to avoid summer drought. This could be achieved by growing maturity group (MG) 00 through II soybean with early plantings. This production system is called Ultra-Short Season Production System (USSPS). The objective of this research was to evaluate MG 00 through II soybean under the USSPS for drought avoidance, seed quality, and yield potential. A total of 498 MG 00 through II lines were evaluated in Arkansas and Missouri from 2000 to 2004. The MG 00 through II lines had potential to avoid drought that starts in mid-July to mid-August, requiring one or two irrigations. Average germination rate was relatively high (63 to 82%) and infection of seed-borne fungal pathogens was minimal (8%). Average yields of lines maturing in 86-92 d, 93-99 d, and ≥ 100 d were 2950, 3301, and 2775 kg ha-1, respectively, under irrigation across environments. Average yields on dryland were 2196 and 2445 kg ha-1 for lines maturing in 86-92 d and 93-99 d, respectively, across environments. Thus, yield potential of the USSPS is competitive to those of full- or early-season production systems under both irrigated and dryland conditions. Genotypic variations for yield and other agronomic traits were large, and thus genotype selection is critical. The MG 00 through II lines are bred for superior performance in the northern U.S. and Canada. Genotype by environment interaction (GEI) and selection analyses of MG 00 through II lines among northern and southern USSPS sites revealed that despite significant GEI, most of the high yielding lines selected in the northern sites could be directly introduced to the southern USSPS sites. Stability analyses of MG 00 through I soybean in the mid-South indicated that selection for superior lines with high yield and high stability across environments was possible. The potential of the USSPS to produce a viable crop in about three months may have a significant implication as water supplies become more limited in the mid-South. |
