Table 1.
Field experimental details
| Gongzhuling (GZL) | Shangzhuang (SZ) | Qiyang (QY) | Changwu (CW) | Shouguang (SG) | |
|---|---|---|---|---|---|
| Latitude | 42°57′N | 39°48′N | 26°45′N | 35°14′N | 36°55′N |
| Longitude | 148°57′E | 116°28′E | 111°52′E | 107°41′E | 118°45′E |
| Altitude (m) | 150–220 | 40 | 120 | 1200 | 22 |
| Mean annual precipitation (mm) | 450–600 | 500–700 | 1255 | 565 | 558 |
| Mean annual temperature (°C) | 4–5 | 11.4 | 18 | 9.1 | 12.4 |
| Soil texture | Silt loam | Silt loam | Clay | Clay loam | Silt loam |
| 31% clay | 20% clay | 61.4% clay | 33% clay | 2% clay | |
| 30% silt | 57% silt | 34.9% silt | 21% silt | 52% silt | |
| 39% sand | 23% sand | 3.7% sand | 46% sand | 46% sand | |
| Organic C (g kg−1) | 12. 9–24.0 | 3.3–5.4 | 4.3–12.0 | 4.3–9.5 | 3.4–10.3 |
| pH (1:5 w/v in 0.01 mol l−1 CaCl2) | 7.3–7.7 | 6.7 | 3.7–5.7 | 7.9–8.0 | 6.2–7.3 |
| Cropping system | Maize | Wheat-maize | Wheat-maize | Wheat | Two-season tomato |
| Year of establishment | 1980 | 2006 | 1990 | 1984 | 2004 |
| Fertilizer treatment (N, P, K, M)* | |||||
| CK | 0, 0, 0, 0 | 0, 0, 0, 0 | 0, 0, 0, 0 | 0, 0, 0, 0 | 0, 0, 0, 0 |
| Nopt | 165, 36, 57, 0† | 220, 70, 75, 0 | 300, 53, 100, 0† | 120, 0, 0, 0 | – |
| Nhigh | – | 560, 70, 75, 0 | – | – | – |
| M | 0, 0, 0, 60 | – | 0, 0, 0, 27 | 0, 0, 0, 75 | 0, 0, 0, 36 |
| M Nopt | 165, 36, 57, 60† | – | 90, 53, 100, 19 | 120, 0, 0, 75 | 368, 79, 382, 36 |
| M Nhigh | – | – | – | – | 1290, 79, 382, 36 |
| Type of manure | Mixture of swine manure, plant residues, and soil. | – | Pig manure 1.1% N | Cow manure | Chicken manure 1.5% N |
| 10–20% C | 10% C | ||||
| 0.5–1% N | 0.26% N | ||||
The average annual amount of nitrogen (kg N ha−1), phosphorus (kg P ha−1), potassium (kg K ha−1), and farmyard manure (Mg ha−1) input.
A treatment without P and K (but identical N level) was included.