Micronutrients decline under long-term tillage and nitrogen fertilization

Authors: SHIWAKOTIA, SANTOSH - Oregon State University; ZHELJAZKOV, VALTCHO - Oregon State University; Gollany, Hero; KLEBER, MARKUS - Oregon State University; XING, BAOSHAN - University Of Massachusetts, Amherst

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2019
Publication Date: 8/19/2019
Citation: Shiwakotia, S., Zheljazkov, V.D., Gollany, H.T., Kleber, M., Xing, B. 2019. Micronutrients decline under long-term tillage and nitrogen fertilization. Scientific Reports. 9. https://doi.org/10.1038/s41598-019-48408-6.
DOI: https://doi.org/10.1038/s41598-019-48408-6

Interpretive Summary: Tillage and nitrogen (N) fertilization can be expected to alter micronutrient dynamics in the soil and in plants over time. However, quantitative information regarding the effects of tillage and N application rates on micronutrient dynamics is limited. The objectives of this study were (a) to determine the long-term effect of different tillage methods as well as variation in N application rates on the distribution of extractable manganese, copper, zinc, boron, and iron in soils and, (b) to assess accumulation of the same nutrients in wheat tissues. The system studied was under a dryland winter wheat-fallow rotation. Tillage methods included moldboard, disk and sweep, and the N application rates were 0, 40, 80, 120, and 160 lb/ac. The concentration of soil manganese was greater under disk (131 ppm) than under moldboard (111 ppm) tillage. Inorganic N application reduced extractable soil copper while, it increased manganese accumulation in wheat grain over time. Comparison of micronutrients with adjacent long-term undisturbed grass pasture since 1931 revealed that the wheat-fallow plots had lost at least 43% and 53% of extractable zinc and copper, respectively, after 75 years of N fertilization and tillage. The results indicate that disk tillage and inorganic N application could reduce the rate of micronutrient decline in soil and winter wheat grain over time compared to moldboard and no N fertilization.

Technical Abstract: Tillage and nitrogen (N) fertilization can be expected to alter micronutrient dynamics in the soil and in plants over time. However, quantitative information regarding the effects of tillage and N application rates on micronutrient dynamics is limited. The objectives of this study were (a) to determine the long-term effect of different tillage methods as well as variation in N application rates on the distribution of Mehlich III extractable manganese, copper, zinc, boron, and iron in soils and (b) to assess accumulation of the same nutrients in wheat (Triticum aestivum L.) tissues. The system studied was under a dryland winter wheat-fallow (WW-F) rotation. Tillage methods included moldboard (MP), disk (DP) and sweep (SW), and the N application rates were 0, 45, 90, 135, and 180 kg/ha. The concentration of soil manganese was greater under DP (131 mg/kg) than under MP (111 mg/kg). Inorganic N application reduced extractable soil copper while, it increased manganese accumulation in wheat grain over time. Comparison of micronutrients with adjacent long-term (since 1931) undisturbed grass pasture revealed that the WW-F plots had lost at least 43% and 53% of extractable zinc and copper, respectively, after 75 years of N fertilization and tillage. The results indicate that DP and inorganic N application could reduce the rate of micronutrient decline in soil and winter wheat grain over time compared to MP and no N fertilization.