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The aim of this study was to investigate the effects of different fertilizing strategies applied during three successive cycles on lettuce growth and the nitrate evolution in the soil, leaching water, and the lettuce plant itself. Four fertilization treatments were compared: integrated production fertilization (IP), organic fertilization (ORG), slow-release N fertilizers (SRF), and plant-associative bacteria (PAB). The nitrate content of the pore water and leachate decreased toward harvesting time in each crop cycle. The accumulation of residual nitrates in the soil decreased in each successive cycle in all treatments. The greatest lettuce head weight was achieved by ORG and SRF in the first cycle and by IP in the third cycle; IP and SRF produced the greatest nitrate content in lettuce leaves, especially in the second and third cycles. The nitrate content of leaves fell in the last cycle, as nitrate levels in soil and in leaching fell in all treatments. [ABSTRACT FROM AUTHOR]

The present work studied the germination recovery of Arthrocnemum macrostachyum, Juncus acutus, and Schoenus nigricans seeds after submersion in hypersaline solution of different salt types. Germination recovery of seed lots incubated in 1, 2, 3, 4, or 5% saline solutions of NaCl, MgCl2, MgSO4, and Na2SO4 for 30 d was studied by transferring ungerminated seeds to distilled water. Seed germination of A. macrostachyum was only inhibited at the highest salinity (4% NaCl, 5% MgCl2) but these ungerminated seeds showed a high germination recovery (81% and 83%, respectively) in distilled water. Seed germination of S. nigricans was totally inhibited by salts and only 26% of them germinated in the control treatment. However, the germination recovery of this species could be stimulated by high salt concentrations (germination of ungerminated seeds incubated at 5% Na2SO4 reached 66% in distilled water). Juncus acutus germinated well without salt (95% in the control treatment) but high salt concentrations inhibited them from germination. However, ungerminated seeds were not damaged by salt, showing a high level of recovery (c. 100% in all salt types and concentrations). The chlorides were more inhibitory to germination than sulphates at equivalent concentrations. The germination-related characteristics of J. acutus and S. nigricans mean that both species may be considered halophytes although neither of them can tolerate such high salinity levels as A. macrostachyum, Juncus acutus, and A. macrostachyum produce nondormant seeds, whereas a high proportion of S. nigricans seeds are dormant. These laboratory results are related to the field ecology of the three species. [ABSTRACT FROM AUTHOR]