Effect of Phosphorus and Nitrogen Fertilization on Sunflower (Helianthus annus L.) Nitrogen Uptake and Yield |
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| Authors: | M M Zubillaga J P Aristi R S Lavado |
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| Institution: | Authors' address: Drs;M. M. Zubillaga (corresponding author;e-mail: ), J. P. Aristi and R. S. Lavado, Cátedra de Fertilidad y Fertilizantes, Facultad de Agronomía, Universidad de Buenos Aires, Avenida San Martín 4453 (C1417DSQ), Buenos Aires, Argentina |
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| Abstract: | Little is known about the effect of combined phosphorus and nitrogen (P‐N) fertilization on the N requirement of sunflower (Helianthus annus L.). This study was carried out to evaluate the effects of varying levels of P and N, as well as the interaction P × N, on the N uptake, yield and N apparent utilization efficiency under field conditions. Split‐plot design experiments were conducted in the mid‐western Pampas in Argentina. Four levels of N (0, 46, 92 and 138 kg N ha?1) and three levels of P (0, 12 and 40 kg P ha?1) were applied to two Typic Hapludolls over two growing seasons (1997–98 and 1998–99). N uptake and soil N‐NO3 contents were determined at the V7, R5 and R9 growth stages. The sunflower yield ranged from 2.5 to 5.0 Mg ha?1. The total N requirement was around 45 kg N Mg?1 grain, and this result suggests that it is not necessary to use different N requirements (parameter b) for fertilized crops when a yield response is expected. To achieve a 100 % yield maximum a N supply (soil plus fertilizer) of 181 kg N ha?1 at P40 was needed. However, at P0, the highest yield was about 80 % of the maximum yield with a N supply (soil plus fertilizer) of 164 kg N ha?1. P application increased the apparent use efficiency of the supplied N. |
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| Keywords: | grain yield N uptake P-N fertilization soil nitrates sunflower |
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