Location: Agricultural Systems ResearchTitle: Weed management practice and cropping sequence impact on soil residual nitrogen
|HATFIELD, PATRICK - Montana State University|
|RAGEN, DEVON - Montana State University|
Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/10/2018
Publication Date: 3/3/2018
Citation: Sainju, U.M., Hatfield, P., Ragen, D. 2018. Weed management practice and cropping sequence impact on soil residual nitrogen. Proceedings of Great Plains Soil Fertility Conference. p. 86-91.
Technical Abstract: Inefficient N uptake by crops from N fertilization and/or N mineralized from crop residue and soil organic matter results in the accumulation of soil residual N (NH4-N and NO3-N) which increases the potential for N leaching. The objective of this study was to evaluate the effects of weed management practices and cropping sequences on soil NH4-N and NO3-N contents at the 0-30 cm depth after crop harvest in the fall from 2012 to 2015 in southwestern Montana. Weed management practices were sheep grazing with no chemical input (GO), no-tillage with chemical inputs (NT), and conventional tillage with no chemical input (TO). Cropping sequences were clover cover crop following safflower/clover intercrop (C-SC), lentil following winter wheat (L-W), winter wheat following clover cover crop (W-C), and winter wheat following lentil (W-L) in a 5-yr crop rotation of safflower/clover cover crop – clover cover crop – winter wheat – lentil – winter wheat. At 0-15 cm, NH4-N and NO3-N contents were greater with C-SC than W-C for GO and TO and greater with C-SC, W-L, or W-C than L-W for NT from 2013 to 2015. At 15-30 cm, NH4-N content was greater for NT than GO and TO and greater with W-C than C-SC and L-W. In contrast, NO3-N content was greater with C-SC than other cropping sequences in 2013 and 2014. Nitrogen mineralized from clover cover crop residue in C-SC and N fertilization to spring wheat in NT increased soil residual N. As the potential for N leaching is low in dryland cropping systems due to limited precipitation in the northern Great Plains, such residual N can reduce the rate of N fertilization to nonlegume crops. The effect of such treatments on crop yields will be further examined.