Effect of application of lime and fertilizers on cultivated peat soil

Abstract

Soil samples were analysed from a long-term liming trial (38 years) and a fertilizing trial (36 years) on woody sedge peat soils at Tohmajärvi Experimental Station in eastern Finland. Five applications of 4000 or 6000 kg/ha of ground limestone increased the soil pH from 4.4 to 4.8 or 5.0, respectively. The cation exchange capacity was increased from 72 me/100 g to 76 or 80 me/100 g, and the base saturation from 43 per cent to 56 or 61 per cent, respectively, if the exchangeable cations were extracted by ammonium acetate at pH 7. The relative increases in the cation exchange capacity and base saturation percentage were even higher when determined by the method of Teräsvuori. The contents of exchangeable calcium and magnesium were increased and that of potassium decreased by liming. A lower application of lime, five times 2000 kg/ha, did not cause statistically significant changes. Owing to the large variation no significant effect of liming on the content of organic phosphorus or of various fractions of inorganic phosphorus in this soil could be detected. Liming did not increase the total amount of mineral nitrogen extracted by K2SO4-solution from the samples incubated under the labotatory conditions, but the highest application enhanced nitrification. Annual applications of 22 kg P/ha as superphosphate, 66 kg K/ha as 40 % or 50 % potassium fertilizer, and 15 kg N/ha as calcium nitrate alone or in any combination did not change the acidity or the cation exchange capacity of the soil in the fertilizing trial. The application of superphosphate was detectable as higher Bray 1 test values and higher contents of inorganic phosphorus in various fractions. The content of exchangeable potassium was about 0.2 me/100 g in plots N, P, and NP, about 0.3 me/100 g in plots PK and NPK, and more than 0.5 me/100 g in plots K and NK. This is well in accordance with the significant response in yields produced by phosphate in this trial. The accumulation of mineral nitrogen in the samples incubated under the laboratory conditions was highest in soil from plots K and NK, and lowest in soil from the plots PK and P.