SOYBEAN GROWTH AND YIELD RESPONSE TO SATURATED SOIL CULTURE IN A TEMPERATE ENVIRONMENT

Saturated soil culture (SSC) is a production system developed in semia rid tropical Australia that reportedly increases soybean (Glycine mau L. (Merr.)) yield above that obtained with conventional irrigation. Wi th SSC, water is maintained in furrows between beds from early vegetat ive stages until maturity. The objective of this research was to evalu ate SSC of soybean as an option in temperate regions for rotations in a rice-based production system. Soybean was sown in 1994 and 1995 at K eiser, Arkansas, on 15 cm high beds, spaced Im apart in fields precisi on-graded to 0.15% slope. In 1994, the cultivars were Hutcheson (MG V) and Manokin (MG TV), and in 1995, the cultivars were Asgrow 6297 (MG VI) (A6297) and Hartz 5545 (MG V) (H5545). In both years, the irrigati on treatments were nonirrigated, furrow-irrigated at a 50mm soil water deficit, and SSC. In agreement with reports from Australia, the SSC t reatment resulted in leaf yellowing after treatments were established, this yellowing was associated with a lag in biomass and N accumulatio n in comparison with the furrow-irrigated treatment in 1994. In 1995, N accumulation rate decreased in SSC during the acclimation period, bu t there was no effect on biomass accumulation rate. In contrast to rep orts from Australia, yield was not increased by the SSC treatment. In 1994, seed yield from the SSC treatment averaged across cultivars was 40% below that from the furrow-irrigated treatment. A similar yield de crease for the SSC treatment was observed in 1995 for H5545. For A6297 , however, the SSC yields and furrow-irrigated yields did not differ. In 1994 for both cultivars and in 1995 for H5545, there was a strong n egative response of seed yield to depth of water in the furrow of the SSC treatment. It was concluded that there is no yield advantage from a SSC management system compared to furrow irrigation at the Arkansas site. A positive yield response of SSC may be limited to arid environm ents where warm temperatures and high irradiance levels contribute to overcoming the detrimental effects of SSC following treatment establis hment.