Nitrogen uptake and nitrogen use efficiency of fertigated potatoes

Field experiments were carried out to assess the nitrogen use efficiency (NUE) of two fertigation treatments (Static and Dynamic) in comparison with a Non-Irrigated/Non-Fertilised (NINF) and an Irrigated/Non-Fertilised (INF) control. In the Dynamic fertigation treatment, water and nutrient supplies were determined from daily calculations of crop dry matter (DM) production and root zone volume. The Static treatment was based on the expected yield with the root zone fixed at the maximum depth from emergence and fertigation schedule on a weekly basis determined from a standard uptake curve. Static and Dynamic received at least 50% of N requirements from organic fertilisers. NUE, expressed as marketable DM yield per kg available N, was 229.0, 188.2, 166.2 and 173.5 kg kg(-1) N for NINF, INF, Static and Dynamic treatments, respectively. In humid and sub-humid areas and on soil with adequate fertility, a high NUE for the NINF treatment was expected as a consequence of the good average yield obtained without irrigation and fertilisation (30.8 t ha(-1)). NUE, calculated considering only the fertigation supply (NUEFERT) differed between the Static and Dynamic treatments for total DM yield (87.0 and 95.4 kg kg(-1) N) but was similar in terms of marketable DM yield (62.4 and 61.4 kg kg(-1) N). Nitrogen uptake was 159, 166, 95 and 83 kg ha(-1) y(-1) for Dynamic, Static, INF and NINF, respectively. At leaf senescence, Dynamic, Static, NINF and INF yielded 80.6, 77.2, 89.5 and 80.6 kg of total DM per kg of nitrogen uptake, respectively. Partition of nitrogen taken up into leaves, stems and tubers was assessed as well as nitrogen concentration in aboveground and storage organs.