Abstract
Nitrate leaching is of great environmental concern, particularly with potatoes grown on sandy soils. This 3-year study evaluated the effect of three N rates (100, 150, and 200 kg ha−1) of single applications of polymer-coated urea (PCU) and a 75% PCU + 25% urea mixture, plus a conventional split application of 200 kg N ha−1 of a 50% ammonium sulfate + 50% calcium ammonium nitrate mixture (CONV) on NO3−-N leaching, potato yield, and N uptake under irrigated and non-irrigated conditions on a sandy soil in Quebec (Canada). Fertilizer N application increased growing season NO3−-N leaching only under irrigation. On average, irrigation increased seasonal NO3−-N leaching by 52%. Under irrigated conditions, PCU reduced NO3−-N leaching compared to PCU + urea. However, both PCU and PCU + urea significantly increased NO3−-N leaching compared to the CONV at the equivalent N rate of 200 kg N ha−1. This was attributed to the timing of soil N availability and deep-water percolation. Total (TY) and marketable (MY) yields in the CONV were similar to those in the PCU applied at the equivalent N rate of 200 kg N ha−1. Despite lower plant N uptake, PCU resulted in greater TY and MY compared to PCU + urea. Residual soil inorganic N was greater for PCU and PCU + urea compared to the CONV, providing evidence that PCU products have the potential to increase NO3−-N leaching after the growing season. In this study, PCU was an agronomically and environmentally better choice than PCU + urea. The results also showed that the efficiency of PCU to reduce seasonal NO3−-N leaching may vary according to the timing of precipitation and irrigation.
Highlights
Nitrogen (N) and water are two major inputs for improving potato (Solanum tuberosum L.)growth and yield
This study evaluated the use of polymer-coated urea (PCU) alone and a PCU + urea mixture, banded all at planting, compared with split applied CONV treatment in irrigated and non-irrigated potato production
Irrigation significantly increased growing season NO3 − -N leaching, but not TY and marketable yield (MY). These findings were attributed to the low moisture deficits during the
Summary
Nitrogen (N) and water are two major inputs for improving potato (Solanum tuberosum L.)growth and yield. Potatoes are highly responsive to N fertilization, and it is a common practice in Quebec (Canada) to apply fertilizer N at rates greater than the local recommendations (125 to 200 kg N ha−1 ) to ensure maximum yield [1]. Potato production in this region is primarily rain fed. The high input of N, coupled with irrigation, has the potential to cause high NO3 − -N leaching, especially on sandy soils [3]. To minimize leaching on these soils, the N fertilizers are commonly split applied, with granular fertilizer applied at planting and 30–40 days after planting (DAP) at hilling [2]
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