Effects Of Soil Nematodes On Nutrient Cyclng And Plant Growth

The interactions between nematodes and bacteria and their effects on wheat growth and transfer of soil N and P were studied in gnotobiotic systems by inoculating nematodes and in pot culture by killing nematodes with nematocide or oven—dry. The effects of nematodes on ¹⁵N absorption by wheat and ¹⁵N loss from soil —plant system were also studied using ¹⁵N isotope tracer technique. In gnotobiotic systems, both the number of bacteria and nematodes in rhizosphere was evidently higher than that in non—rhizo-sphere. The inoculation of soil nematodes significantly promoted the bacteria population . The interactions between nematodes and bacteria evidently increased the content of soil mineral N, with about 35% more than that treatment with bacteria only at the end of incubation(40 days). Soil available P was not affected by nematodes,while soil microbial biomass P increased obviously with the inoculation of nematodes. The wheat biomass and N absorption by wheat in nematodes+bacteria treatment increased by 6. 5% and 5. 8 % respectively at the end of incubation when compared with that in bacteriaonly treatment, but the P absorption by wheat decreased by 9. 1 %. The interactions between nematodes and bacteria mainly increased shoot bimass and shoot N absorption by wheat and had little effects on root biomass and root N absorption.In the absence of parasitic nematodes, the N and P absorption by wheat and wheat biomass evidently decreased after kiiling soil nematodes by nema-tocide and oven—dry. The mineralization of soil N and P were also restricted by killing soil nematodes, however,soil N mineralization was more sensitive to nematodes removing than soil P mineralization.The results obtained from 15N isotope tracing systems indicated that the inoculation of nematodes increased the absorption of (NH^&Oi—N by 10. 3%, favoured the transfer of N nutrient to spike, and reduced the loss of fertilizer N by 18. 2% compared with no nematodes treatment.