Recovery of Deep‐Point Injected Soil Nitrogen‐15 by Switchgrass, Alfalfa, Ineffective Alfalfa, and Corn

Abstract

Abstract Removal of nitrates that have leached below the corn ( Zea mays L.) rooting zone may be accomplished by deep‐rooted plant species. This study evaluated the capacity of corn (‘Pioneer 3732’), alfalfa ( Medicago sativa L. ‘Saranac 7061’), ineffective alfalfa (‘In Saranac 7496’), and switchgrass ( Panicum virgatum L. ‘Sunburst’) to use point‐injected 15 N. A 20% enriched 15 N KNO 3 was injected at 120 cm in the soil profile. Three points were injected in each plot with four replicates. One corn plant nearest the injection point and one 30 by 30 cm area surrounding the injection point in the other species were sampled. The amount of NO 3 ‐N removed by switchgrass from the soil profile below 120 cm was 20 kg ha −1 per year, compared with 1, 8, and 9 kg ha −1 for corn, alfalfa, and ineffective alfalfa, respectively. Switchgrass may be a management alternative for removing NO 3 ‐N from the soil at depths below the rooting zone of most crops.