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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #324814
Title: Soil pH and exchangeable cation responses to tillage and fertilizer in dryland cropping systems

Author
item Reeves, Justin
item Liebig, Mark

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2016
Publication Date: 10/20/2016
Publication URL: http://handle.nal.usda.gov/10113/63332
Citation: Reeves, J.L., Liebig, M.A. 2016. Soil pH and exchangeable cation responses to tillage and fertilizer in dryland cropping systems. Communications in Soil Science and Plant Analysis. 47(21):2396-2404. doi:10.1080/00103624.2016.1243706.

Interpretive Summary: Long-term use of nitrogen fertilizers contribute to soil acidification and other chemical changes that can lead to lower fertility. Here, we present near-surface soil (0-3 inch) chemistry data from two different crop rotations in the US northern Great Plains: (1) continuous crop (spring wheat - winter wheat - sunflower) and (2) crop-fallow (spring wheat – fallow) that underwent tillage (no-, minimum, and conventional tillage) and nitrogen rate (no/low, medium, high) treatments for 16 years. For continuous cropping, nitrogen rate (but not tillage) had a significant effect on pH change, with the highest N rate leading to the largest pH decrease (-0.76 units). Nitrogen rate also had a significant effect on cation exchange capacity (CEC), whereby CEC increased with nitrogen rate. Within continuous cropping, high N fertilization resulted in a gain of exchangeable sodium and a loss of exchangeable calcium, whereas at low N fertilization the opposite occurred. For crop-fallow, the high N rate contributed to a significantly greater pH decline (-0.88) than the other N rates under no-tillage. Similarly, for conventional tillage, the high N rate had greater pH drop (-0.36) than the low N rate (-0.01). There were no treatment effects on CEC or individual exchangeable ions within crop-fallow. Agricultural producers utilizing high nitrogen rates to increase productivity need to be aware of the potential for soil acidification, particularly under no-till.

Technical Abstract: Long-term use of nitrogen (N) fertilizers can lead to soil acidification and other chemical changes that can lower fertility. Here, we present near-surface (0-7.6 cm) soil chemistry data from 16 years of two different crop rotations in the US northern Great Plains: (1) continuous crop (CC; spring wheat [Triticum aestivum L.] - winter wheat [T. aestivum] - sunflower [Helianthus annuus L.]) and (2) crop-fallow (C-F; spring wheat – fallow) that underwent factorial tillage (no-, minimum, and conventional tillage) and N rate (no/low, medium, high; N rates varied by rotation) treatments. For CC, N rate (but not tillage) had a significant effect on pH, with the highest N rate leading to the largest pH decline (-0.76). Nitrogen rate also had a significant effect on cation exchange capacity (CEC) for CC, whereby CEC increased with N rate. Responses of individual exchangeable cations within CC indicated a gain of Na+ and a loss of Ca2+ at high N compared to modest losses of Na+ and gains in Ca2+ at moderate and low N. For C-F, a significant N rate*tillage interaction showed that under no-tillage, the high N rate had a significantly greater pH decline (-0.88) than the other N rates. Similarly, for conventional tillage, the high N rate had greater pH drop (-0.36) than the low N rate (-0.01). There were no treatment effects on CEC or individual exchangeable ions for C-F. Managers utilizing high N rates to increase productivity need to be aware of the potential for soil acidification, particularly if no-tillage is utilized. Differential soil chemistry effects by rotation indicate that long-term soil chemical changes can be system- and management-specific, an important consideration when planning long-term management.