Effect of slow‐release nitrogen on the nitrogen availability in an andisol and the critical nitrogen concentration in wheat

Abstract

AbstractThe use of coated fertilizers and the concept of the critical N dilution curve are alternatives capable of improving the production efficiency of wheat (Triticum aestivum L.) crops in agro‐ecosystems. The objectives of this work were to evaluate the effect of a slow release urea‐coated fertilizer on (i) the production of wheat's shoot biomass at the anthesis stage, (ii) the concentration of N in the shoot biomass, and (iii) the N availability in the Andisol. Two fertilizers: urea and urea‐coated were evaluated using four increasing N rates and a control treatment (without fertilization), in three application strategies, during two growing seasons (late sowing [S1] and early sowing [S2]). Samples of shoot biomass and soil (0–20‐cm depths) were collected at five wheat growth stages (Z21, Z31, Z39, Z45, Z69 on the Zadoks scale). The average production of shoot biomass was 10.3 t dry matter (DM) ha–1 for S2 and 7.9 t DM ha–1 for S1 and N concentrations was between 1.0–3.0%. When using a coated urea fertilizer in this Valdivian agro‐ecosystem, no statistical differences (P < .05) in shoot biomass or wheat N concentrations were found at anthesis (Z69). Differences were principally between seasons. We therefore proposed a new adjustment to the dilution N curve, with a value concentration critical, Nc start of 3.80%, and 4.15%, for S1 and S2, respectively. Use demand parameters such as Nc adjusted to the agro‐ecosystem for wheat crop, allows to rationalize the fertilization according to inorganic N available from the soil.