Table 1. Fertilizer treatments in the Lanna long-term field experiment, C/N of the organic amendments and measured soil chemical factors.
Mean soil pH, total carbon (Tot C), total nitrogen (Tot N) and C/N of the soil in 2014 (https://www.slu.se/institutioner/mark-miljo/forskning/vaxtnaringslara-/vaxtnaring/langliggan de-vaxtnaringsforsok/r3-0130/). Different letters within each soil factor (column) indicate significant treatment effects (lme, Tukey p < 0.05, n = 4).
| Treatment |
C/N amendment |
pH (H2O) |
Tot C (%) |
Tot N (%) |
C/N soil |
|---|---|---|---|---|---|
| Unfertilized | – | 6.24 b | 2.01 e | 0.17 d | 11.7 a |
| Calcium nitrate (Ca(NO3)2)1 | – | 6.37 ab | 2.07 de | 0.17 d | 11.9 a |
| Ammonium sulphate ((NH4)2SO4)1 | – | 5.89 c | 2.09 cd | 0.18 cd | 11.7 a |
| Grass hay2 | 20.5 | 6.23 b | 2.13 c | 0.18 c | 11.7 a |
| Farmyard manure3 | 16.8 | 6.31 ab | 2.41 b | 0.20 b | 11.8 a |
| Household compost4 | 9.4 | 6.49 a | 2.70 a | 0.25 a | 10.9 b |
| Sewage sludge5 | 8.8 | 5.98 c | 2.35 b | 0.21 b | 11.4 a |
Notes.
1
80 kg N ha −1 yr −1, but in 1996 only 40 kg N due to residual N after peas grown in 1995.
2
Consisted mainly of Timothy.
3
From a cowshed with straw bedding.
4
Derived from domestic waste.
5
Dewatered anaerobically digested sewage sludge, only low levels of toxicants in the sludge (Börjesson, Kirchmann & Kätterer, 2014).