Table 3 Impact of 75 years of inorganic N application rate (N rate) on soil micronutrients and soil pH of dryland winter wheat-fallow cropping system under disk tillage management compared to nearby undisturbed grass pasture (GP).

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

Nutrients Soil depth (cm) N rate (kg ha−1) GP Cultivation effect
0 45 90 135 180
mg kg−1
Manganese 0–10 124b 120b 134ab 138ab 139ab 166a 16% ↓
  10–20 103ab 84b 88b 104ab 103ab 130a 21% ↓
  20–30 77a 74a 73a 67a 75a 94a 18% ↓
  30–60 85a 74a 76a 72a 71a 95a 11% ↓
Zinc 0–10 2.6b 1.7b 3.5b 1.8b 1.4b 6.0a 43% ↓
  10–20 2.0a 2.2a 2.3a 1.4a 3.1a 2.8a 11% ↑
  20–30 1.5a 0.5a 2.3a 0.2a 3.2a 1.1a 49%↓ 43%↑
  30–60 2.3a 1.2a 3.1a 0.4a 1.6a 1.0a 28%↓ 63%↑
Copper 0–10 1.1b 0.9b 0.7b 0.6b 0.6b 2.3a 53% ↓
  10–20 1.5b 1.9b 1.6b 1.5b 1.6b 2.6a 28% ↓
  20–30 2.4bc 2.2bc 2.1bc 1.7c 1.9bc 2.8a 15% ↓
  30–60 2.6ab 2.5ab 2.1b 2.2b 2.4b 3.1a 11% ↓
Boron 0–10 6.6a 6.2a 6.5a 6.7a 6.1a 0.0b ND
  10–20 6.7a 6.2a 6.4a 6.5a 6.2a 0.0b ND
  20–30 1.3a 0.7a 1.9a 0.2a 2.4a 1.1a 34%↓ 17%↑
  30–60 6.6a 6.3a 6.4a 7.0a 6.3a 0.0b ND
pH 0–10 5.8b 5.4b 5.6b 5.1b 5.3b 6.8a 14% ↓
  10–20 6.1b 5.6b 5.9b 5.4b 5.6b 6.8a 11% ↓
  20–30 6.5ab 6.3b 6.5ab 6.4ab 6.5ab 7.0a 06% ↓
  30–60 6.6b 6.6b 6.8ab 6.6b 6.7ab 7.1a 05% ↓
  1. Means sharing the same letter within the rows are not significantly different at 5% level of significance.
  2. Percentage calculated from the difference in the value of grass pasture (GP) and the highest value (if GP is greater) or the lowest value (if GP is lower) for the treatments within each soil depths, so that minimum deviation from the GP is calculated in either case. The downward and upward arrow indicates decline or incline from the soils of GP after cultivation, respectively. The column with both upward and downward in the same cell indicates that respective soil depth has some treatments that have greater value than GP and some treatments with lesser value than GP.