Growth of field horsetail (Equisetum arvense) under low light and low nitrogen conditions

Field horsetail was grown from rhizome segments for 28 and 52 d under 35, 6 0, 120, 170, and 320 mu mol m(-2) s(-1) photosynthetic photon flux (PPF) an d four continuous nitrogen (N) supply rates corresponding to a total of 1 t o 6 tg N ha(-1) 28 d after planting (DAP) and 6 to 41 kg N ha(-1) 52 DAP. T here was no response to the supply of N in the first growth period, probabl y due to the mobilization of nitrogen available in the planted rhizomes, an d only dry weight (DW) of new belowground production, mostly roots, respond ed to increased light. Rhizomes were produced during the latter part of the 52-d period. Requirements for light and N during the 52-d period were low, because total new tissue production was only reduced at the lowest levels of light (35 mu mol m(-2) s(-1) PPF) and the two lowest N supply rates (6 a nd 18 kg N ha(-1)). The ratio of shoot DW to belowground organ DW increased only as the N supply increased. Shoot height response to an increased N su pply was also small. Field horsetail can therefore be considered tolerant o f low levels of N but will be overtopped by fast-growing species when compe ting for increased supplies of N. Both an increase in N supply and a reduct ion in light increased the reduction of DW of the planted rhizomes, whereas tuber production was favored by low N supply and high light intensities. F ield horsetail can tolerate low levels of N but is not likely to be competi tive in a dense crop stand.