Revegetation of waste fly ash lagoons II. Seedling transplants and plant nutrition

Abstract

As an alternative or in addition to direct seeding, container-grown transplants provide a means of economically and rapidly revegetating waste fly ash lagoons through the expeditious establishment of vegetation islands. Survival and growth of Enchylaena tomentosa and Nitraria billardierei transplants were largely dependent on the size of the root volume at transplanting. Growth response of both species in fly ash increased significantly as transplant container size increased from 110 ml to 800 ml. Fly ash incorporated into the potting mix during the containerised stage of growth generally reduced plant growth and survival following eventual transplantation. Gradual hardening of Enchylaena tomentosa seedlings to increasing concentrations of fly ash in the potting mix (25 to 50 to 75% fly ash), however, improved immediate survival following transplantation, into pure ash. Nitrogen deficiency in Port Augusta fly ash was a major nutritional limitation to growth of these two species. Growth and dry matter production responded optimally to application of N fertiliser (NH4NO3) at 100-150 kg Nha-1. Although bicarbonate-extractable P levels in fly ash were high (over 250 mg kg-1), a response of Enchylaena tomentosa to supplementary P application [Ca(H2PO4)2.H2O] at 100-200 kg P ha-1 was observed. N. billardierei did not respond to supplementary P, and it was suggested that fly ash P may be selectively available to plants on a species dependent basis. No growth responses to K application (KCI) at rates of up to 400 kg K ha-1 were found.