| Abstract: | Studies on N balance due to N inputs and outputs and soil N retention to measure cropping system performance and environmental sustainability are limited due to the complexity of measurements of some parameters. We measured N balance based on N inputs and outputs and soil N retention under dryland agroecosystem affected by cropping system and N fertilization from 2006 to 2011 in the northern Great Plains, USA. Cropping systems were conventional tillage barley (Hordeum vulgaris L.)–fallow (CTB‐F), no‐tillage barley–fallow (NTB‐F), no‐tillage barley–pea (Pisum sativum L.) (NTB‐P), and no‐tillage continuous barley (NTCB). In these cropping systems, N was applied to barley at four rates (0, 40, 80, and 120 kg N ha?1), but not to pea and fallow. Total N input due to N fertilization, pea N fixation, soil N mineralization, atmospheric N deposition, nonsymbiotic N fixation, and crop seed N and total N output due to grain N removal, denitrification, volatilization, N leaching, gaseous N (NOx) emissions, surface runoff, and plant senescence were 28–37% greater with NTB‐P and NTCB than CTB‐F and NTB‐F. Total N input and output also increased with increased N rate. Nitrogen accumulation rate at the 0–120 cm soil depth ranged from –32 kg N ha?1 y?1 for CTB‐F to 40 kg N ha?1 y?1 for NTB‐P and from –22 kg N ha?1 y?1 for N rates of 0 kg N ha?1 to 45 kg N ha?1 y?1 for 120 kg N ha?1. Nitrogen balance ranged from 1 kg N ha?1 y?1 for NTB‐P to 74 kg N ha?1 y?1 for CTB‐F. Because of increased grain N removal but reduced N loss to the environment and N fertilizer requirement as well as efficient N cycling, NTB‐P with 40 kg N ha?1 may enhance agronomic performance and environmental sustainability while reducing N inputs compared to other management practices. |
