We have grown wild rocket (arugula) in our home garden and under home garden conditions it does not require any fertilizer. All it needs is good quality compost and continuously moist soil conditions.
After seeing your question, I did a Google search and found the following paper that may be useful. I am adding the abstract of the paper and the internet link for the full paper. Hope that you would be able to get the full paper, otherwise, please let me know. I can forward a copy.
Factors influencing tissue nitrate concentration in field-grown wild rocket (Diplotaxis tenuifolia) in southern England ( available at: http://www.tandfonline.com/doi/abs/10.1080/19440049.2012.696215?journalCode=tfac20)
Abstract
Wild rocket (Diplotaxis tenuifolia) is a leafy vegetable known for its high tissue nitrate concentration (TNC) which can exceed the limits set in the relevant European legislation designed to protect human health. The aim of this work was to understand the factors influencing TNC and to develop best practice guidelines to growers. Commercial crops of field-grown wild rocket were studied over two seasons. In 2010, ten separate crops were sampled representing a range of soil types and time periods during the summer. Two fields sampled using a ‘W’- or ‘X’-shaped sampling pattern demonstrated that 10 incremental samples bulked to make 1 kg of fresh material could be used to provide an adequate sample for determination of TNC in the wild rocket crop, as is the case for other leafy vegetables. Of eight commercial crops sampled in 2010 with an average nitrogen (N) fertiliser application of 104 kg N ha−1, two exceeded the limit of 6000 mg kg−1 set in the legislation. In 2011, six N response experiments were carried out, and only two sites showed a significant yield response to N fertiliser. The reason for the lack of response at the other sites was principally due to high levels of soil mineral N prior to drilling, meaning the crops’ requirement for N was satisfied without additional fertiliser N. In the experimental situation at an N fertiliser application rate of 120 kg N ha−1, 50% of crops would have exceeded the 6000 mg kg−1 limit. In both seasons, low radiation levels in the 5 days prior to harvest were shown to increase TNC, although the relationship was also influenced by N supply. Strategies for optimising N nutrition of field-grown wild rocket are discussed.