ARS | Publication request: Dryland soil nitrogen cycling influenced by tillage, crop rotation, and cultural practice

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 13, 2012
Publication Date: August 12, 2012
Citation: Sainju, U.M., Lenssen, A.W., Caesar, T., Jabro, J.D., Lartey, R.T., Evans, R.G., Allen, B.L. 2012. Dryland soil nitrogen cycling influenced by tillage, crop rotation, and cultural practice. Nutrient Cycling in Agroecosystems. 93(3):309-322.

Interpretive Summary: Information on soil N storage and mineralization as influenced by management practices is needed to optimize N need for crops, minimize N losses through leaching, volatilization, denitrification, and N2O emission, increase N-use efficiency, and reduce the cost and rate of N fertilization without compromising crop yields and quality. In the northern Great Plains, traditional farming systems, such as conventional tillage with the crop-fallow, reduces soil N storage because of increased erosion and mineralization of organic N and reduction in plant residue N returned to the soil due to absence of crops during fallow. Studies have shown that long-term tillage with crop-fallow has reduced soil N storage by 30 to 50% in the last 50 to 100 years. We evaluated the effects of tillage, crop rotation, and cultural practice on dryland crop biomass (stems and leaves) N, surface residue N, and soil N fractions at the 0- to 20-cm depth in a Williams loam from 2004 to 2008 in eastern Montana, USA. Treatments were two tillage practices (no-tillage [NT] and conventional tillage [CT]), two crop rotations (continuous spring wheat [CW] and spring wheat-barley hay-corn-pea [W-B-C-P]), and two cultural practices (regular [conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height] and ecological [variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height]). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH4-N, and NO3-N. Crop biomass N was 30% greater in W-B-C-P than in CW in 2005. Surface residue N was 30 to 34% greater in NT with the regular and ecological practices than in CT with the regular practice. The STN, PON, and MBN at 10 to 20 and 0 to 20 cm were 5 to 41% greater in NT or CW with the regular practice than in CT or CW with the ecological practice. The PNM at 5 to 10 cm was 22% greater in the regular than in the ecological practice. The NH4-N and NO3-N contents at 10 to 20 and 0 to 20 cm were greater in CT with W-B-C-P and the regular practice than with most other treatments in 2007. Surface residue and soil N fractions, except PNM and NO3-N, declined from autumn 2007 to spring 2008. No-tillage with the regular cultural practice increased surface residue and soil N storage but conventional tillage with diversified crop rotation and the regular practice increased soil N availability. Without N inputs from crop residue and soil amendments, surface residue and soil N storage decreased but N mineralization increased from autumn to spring.

Technical Abstract: Management practices may influence dryland soil N dynamics. We evaluated the effects of tillage, crop rotation, and cultural practice on dryland crop biomass (stems and leaves) N, surface residue N, and soil N fractions at the 0- to 20-cm depth in a Williams loam from 2004 to 2008 in eastern Montana, USA. Treatments were two tillage practices (no-tillage [NT] and conventional tillage [CT]), two crop rotations (continuous spring wheat [Triticum aestivum L.] [CW] and spring wheat-barley [Hordeum vulgaris L.] hay-corn [Zea mays L.]-pea [Pisum sativum L.] [W-B-C-P]), and two cultural practices (regular [conventional seed rates and plant spacing, conventional planting date, broadcast N fertilization, and reduced stubble height] and ecological [variable seed rates and plant spacing, delayed planting, banded N fertilization, and increased stubble height]). Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH4-N, and NO3-N. Crop biomass N was 30% greater in W-B-C-P than in CW in 2005. Surface residue N was 30 to 34% greater in NT with the regular and ecological practices than in CT with the regular practice. The STN, PON, and MBN at 10 to 20 and 0 to 20 cm were 5 to 41% greater in NT or CW with the regular practice than in CT or CW with the ecological practice. The PNM at 5 to 10 cm was 22% greater in the regular than in the ecological practice. The NH4-N and NO3-N contents at 10 to 20 and 0 to 20 cm were greater in CT with W-B-C-P and the regular practice than with most other treatments in 2007. Surface residue and soil N fractions, except PNM and NO3-N, declined from autumn 2007 to spring 2008. No-tillage with the regular cultural practice increased surface residue and soil N storage but conventional tillage with diversified crop rotation and the regular practice increased soil N availability. Without N inputs from crop residue and soil amendments, surface residue and soil N storage decreased but N mineralization increased from autumn to spring.