Soil CNPK and Enzyme Activities in Non-flood and Flood Irrigation of Late Rice Cultivation in Jiangxi, China.

The conservation of water resources and alternative irrigation systems for rice cultivation are under investigation. A long-term field experiment has been carried out since 2003 in Yujiang —]], Jiangxi Province. The aim is to compare the effects of nonflood-irrigation of rice (Oryza sativa L.) cultivation - with straw mulching (SM) , zero straw mulching (ZM), to flood-irrigation (F) on rice growth, soil biological and chemical properties.

Results indicated that SM increases grain yields and root systems. Also, it increases soil organic carbon, soil microbial biomass carbon and soil microbial basal respiration rate. The soil microbial biomass carbon was significantly increased following the sequence of SM>ZM>F, especially in 2006. Soil microbial basal respiration rates were significantly higher in SM and ZM than that in F.

Soil catalase activity was significantly higher in SM than that in F in 2005, but no significant difference among the three treatments was observed in 2006. Soil urease activity was significantly higher in SM than that in ZM and F in 2005 and significantly higher in SM than in F in 2006. Soil invertase activity was significantly higher in SM than in F in 2005 and significantly higher in SM and ZM than in F in 2006.

Soil macro nutrients are greatly influenced by SM. In comparison of SM to F and ZM, the total N, available N, and available K showed an increased trend and significant differences had occurred among treatments. However, Soil available P was lower in SM and ZM than that in F in 2006 suggesting a sign of chemical p-fixation in nonflood-irrigation treatment. Improving N and P management is necessary for sustaining SM and ZM in the long-run. Evaluating the long-term effects of nonflood-irrigation, such as treatment SM and ZM, on soil quality and environmental impacts are important.