Across a landscape, soil texture controls the optimum rate of N fertilizer for maize production

• We assessed how within soil texture variations affect maize N response, soil N availability and residual soil nitrate.
• We analyzed how N fertilization based on economic optimum N rate would help decreasing residual nitrate levels.
• Soil texture variations affected maize N fertilizer response with higher yield and N uptake in coarse than in finesoils.
• Nitrogen rate equivalent to economic optimum N rate would have allowed decreasing residual soil nitrate levels.
• Variable rate N application according to soil texture and to the optimum N rate can reduce input production costs.

In maize (Zea mays L.) production, appropriate N management needs to consider the specific relations between soil texture, growing season characteristics, and N fertilizer rates. Our main objective was to assess the interaction effect of soil texture (clay, clay loam, and fine sandy loam), and N fertilizer rates (0 to 250 kg N ha−1) on maize N response, soil N availability, and residual soil nitrate (RSN) at harvest. The study was conducted over three years (2000–2002) on a 15-ha field near Montreal (Canada). Crop responses parameters included yield, N uptake, and economic optimum N rate (Nop). Soil and crop-based measures of soil N availability indices were composed of nitrate desorbed from ion exchange membranes measured before (AEM-N1) and after seeding (AEM-N2). The effects of N fertilization, soil texture (fine sandy loam > clay loam > clay), were highly significant on maize yield and N uptake. Averaged across years, Nop was 181, 161, and 125 kg N ha−1 in the clay, clay loam, and fine sandy loam, respectively. Estimated RSN at Nop (13–77 kg NO3-N ha−1) were much lower than the measured ones (22 to 173 kg NO3-N ha−1). Nitrogen rate equivalent to Nop would have allowed decreasing RSN by 100 kg NO3-N ha−1. Variable rate N application according to soil texture and to the Nop can reduce input production costs and therefore environmental risks by decreasing RSN.