Micronutrients decline under long-term tillage and nitrogen fertilization

Area of Science:

• Agricultural Science
• Soil Science
• Agronomy

Background:

• Tillage and nitrogen (N) fertilization significantly influence soil and plant micronutrient dynamics over time.
• Quantitative data on the long-term effects of varying tillage methods and N application rates on micronutrient distribution and plant uptake is limited.
• Understanding these effects is crucial for sustainable agricultural practices and maintaining soil fertility.

Purpose of the Study:

• To evaluate the long-term impact of different tillage methods (moldboard, disk, sweep) and N application rates (0-180 kg N ha⁻¹) on soil micronutrient distribution (Mn, Cu, Zn, B, Fe).
• To assess the accumulation of these micronutrients in wheat (Triticum aestivum L.) tissues under a dryland winter wheat-fallow rotation.
• To compare micronutrient levels with undisturbed grassland to quantify long-term changes.

Main Methods:

• Long-term field study under a dryland winter wheat-fallow (WW-F) rotation.
• Investigated three tillage methods: moldboard plow (MP), disk plow (DP), and sweep plow (SW).
• Applied five nitrogen (N) fertilization rates: 0, 45, 90, 135, and 180 kg N ha⁻¹.
• Analyzed Mehlich III extractable soil micronutrients (Mn, Cu, Zn, B, Fe) and their concentration in wheat tissues.

Main Results:

• Higher soil manganese concentrations were observed under disk tillage (DP) compared to moldboard plow (MP).
• Inorganic N application decreased extractable soil copper but increased manganese accumulation in wheat grain over time.
• After 75 years, WW-F plots showed significant losses of extractable zinc (≥43%) and copper (≥53%) compared to undisturbed grassland.
• Disk tillage (DP) and inorganic N application showed potential to mitigate micronutrient decline in soil and wheat grain.

Conclusions:

• Long-term tillage and N fertilization practices in dryland winter wheat-fallow systems significantly alter soil micronutrient levels and plant accumulation.
• Disk tillage and the application of inorganic nitrogen appear to be more effective in preserving soil and wheat micronutrient status compared to moldboard tillage and no N fertilization.
• These findings highlight the importance of judicious tillage and N management strategies for maintaining soil health and crop nutrition in semi-arid agricultural systems.