Effect of nitrogen and plant density on direct-seeded or transplanted wild rocket

The effects of three nitrogen rates (0, 100 and 200 kg ha(-1)), two sources of N, ammonium nitrate and ammonium sulphate, and three plant densities (33, 50, and 100 plants m(-2)) were studied on direct-seeded and transplanted crops of wild rocket (Diplotaxis tenuifolia). Successive cuttings were made to evaluate plant survival, yield and quality. The effect of sources and application rate of nitrogen on yield was not evident, probably due to initially high soil fertility. Ammonium sulphate raised the sulphate content of leaves. No variations was observed in nitrate content due to different nitrogen or sources rates. Wild rocket also accumulated a high nitrate content in the control plot. Significant yield increases resulted when plant density was increased from 33 to 100 plants m(-2), although individual plants were heavier at the lowest density (33 plants m(-2)). No definitive response was obtained from the comparison of direct-seeded and transplanted crops. Successive cuttings did not affect plant stands, but successive cuttings were detrimental for both marketable yield and quality.