Surfactant Impact on Nitrogen Utilization and Leaching in Potatoes

Some producers face a unique problem with potato (Solanum tuberosum) production on sandy soils where a dry zone can develop in the potato hill. Surfactants may reduce this dry zone by decreasing water surface tension, thus enhancing water and nutrient uptake. A study was established to determine if band applying nonionic surfactant at 9.35 L ha(-1) in the seed furrow at planting would reduce nitrate-nitrogen (NO(3)-N) leaching and increase potato yield and quality. Nitrogen (N) fertilizer was applied at 34, 168, 236, and 303 kg N ha(-1). Porous cup samplers were installed beneath the row at 1-m depth in three treatments, with soil solution samples collected weekly. Nitrate-N concentration and irrigation + rainfall data were used to estimate nitrate leaching. Surfactant application resulted in changes of total NO(3)-N load between + 6.0 and -46.7% for this 3- year study; however, because of high within-treatment variation for the soil water NO(3)-N samples, these differences were not statistically significant at the < 0.10 p-value, although a two sample t-test of +/- surfactant treatments across N rates and years resulted in a < 0.01 p-value. Nitrate-N leaching increased with increasing N fertilization rate. Soil NO(3)-N concentration 20 days after the last N fertilization was significantly less (30.1%) with surfactant application across all years and N rates. Soil NH(4)-N at this time also tended to be decreased with surfactant application (19.7% reduction, p = 0.12). Total potato yield was not affected by surfactant use, but increased with increasing N rate. Tuber N content increased with surfactant use, resulting in increased crop N uptake.