Table 5 Interaction effect of tillage system and year on total concentrations of copper, iron, and boron accumulation in wheat straw.

From: Micronutrients decline under long-term tillage and nitrogen fertilization

Nutrients

Tillage

Year

1995

2005

2015

mg kg−1

Copper

Moldboard

2.0aB†

3.4aA

0.6aC

Sweep

2.4aA

1.7bA

0.6aB

Disk

1.7aA

2.3abA

0.5aB

Iron

Moldboard

48aA

52aA

32aB

Sweep

50aA

30bB

29aB

Disk

48aA

49aA

30aB

Boron

Moldboard

3.7aB

5.8aA

2.3aC

Sweep

3.4aA

4.2abA

2.0bB

Disk

3.4aAB

3.1abA

2.3aB

  1. †Means followed by the same uppercase letter in a row indicate no significant differences between years for each tillage system and means followed by same lowercase letters in a column indicates no significant differences between tillage system in each year at 0.05 probability level.
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