Martino asks: Martin, I have to plant 700 hectares of sunflowers with sowing date between 10/10 and 20/10 in the Villegas / Ameghino area with 2 machines, both with simple in-line fertilization. I will use a mixed starter (70% DAP + 30% Urea). What maximum dose of this starter would you recommend in the line to avoid N phytotoxicity?
Response from Martin Diaz Zorita: Matias, in the sunflower the initial contribution of P is very important and would not limit the dose to be applied due to the presence of N from urea. If it were only FDA, the planting effect is consistent with supplies between 10 and 12 kg / ha of P (element). In the sunflower, to reduce the risk of urgent plant failure due to the N of the fertilizer, assuming plantations at a distance between the rows of 52 cm, it would be avoided to exceed 10 kg / ha of N and if they were at 70 cm away, it would not exceed 7 kg / ha of N. With the proposed mixture it would be between 30 (at 70 cm) and 40 kg / ha (at 52 cm).
Always providing adequate regulation of the fertilizer distribution, which in the case of mixtures such as the one proposed by you, is very important during the day (linked to changes in temperature-humidity) of the environment. It is also important to sow in soil with adequate humidity and temperature to obtain rapid-emergence germination, since the risks of phytotoxicity of fertilizers increase with delays in emergence-germination and in coarse-textured soils with little organic substance content. The combination of failures in distribution and planting in cold or low humidity soils increase these risks.
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