Tillage and Nitrogen Placement Effects on Nutrient Uptake by Potato

Deep tillage of compacted soils can improve potato ( Solanum tuberosum L.) tuber yield and quality if no other production factors are limiting. We hypothesized that within‐row subsoiling and N placement would affect tuber yields and availability of plant nutrients. Potato (cv. Russet Burbank) was grown after winter wheat ( Triticum aestivum L.) in 1989 and after dry bean ( Phaseolus vulgaris L.) in 1990 on a furrow irrigated Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthid). Fall tillage treatments (disking, chiseling, and moldboard plowing) were split with zone subsoiling after planting. Nitrogen was broadcast before planting or banded beside the seed piece at planting across all tillage combinations. We estimated plant nutrient status and uptake each year with whole‐plant and petiole samplings during tuber growth. Final tuber yield and quality were determined in early October. Fall tillage did not influence nutrient concentration and uptake, tuber yield, or quality. Zone subsoiling increased average plant dry weights 9%, total tuber yields 10% (4 Mg ha −1 ), and quality, and increased P uptake an average of 11.6% (1.8 kg P ha −1 ) without appreciably changing whole‐plant or petiole P concentrations. Banding N increased average plant dry weight 6.4%, total tuber yield 9%, and N uptake 28% compared with broadcast N. Petiole NO 3 ‐N, P, K, and Zn concentrations were higher where N was banded. There were no consistent zone subsoiling × N placement interactions. Higher nutrient applications may be required with zone subsoiling or to compensate for soil compaction problems.