Cattle manure amendments can increase the pH of acid soils

Crop production on acid soils can be improved greatly by adjusting the pH t o near neutrality. While soil acidity is commonly corrected by liming, ther e is evidence that animal manure amendments can increase the pH of acid soi ls. The effect of fresh cattle manure on soil acidity and nutrient availabi lity was determined in the laboratory for two acid soils from Beaverlodge a nd Fort Vermillion in the Peace River region of Alberta, Canada. The effect of manure on soil pH was immediate and persisted during an 8-wk incubation . Manure-amended soil had significantly higher pH than unamended soil, and the highest rate (40 g manure kg(-1), dry weight basis) increased the pH of Beaverlodge and Fort Vermillion soils from 4.8 to 6.0 and 5.5 to 6.3, resp ectively. The higher pH in manure-amended than unamended soils was attribut ed to buffering from bicarbonates and organic acids in cattle manure. Miner al N (NH4-N + NO3-N), available P, K, Ca, and Mg increased immediately afte r manure application, and available P and K remained significantly higher i n manure-amended than unamended soil after the 8-wk incubation, Soils amend ed with 40 g manure kg(-1) had three to four times more plant-available P a nd K than unamended soils after incubation. Available S concentrations did not differ significantly in manure-amended and unamended soils. Extractable Al and Fe declined slightly after manure application, but did not differ i n manure-amended or unamended soils after incubation. No change in the cati on-exchange capacity (CEC) of manure-amended soils compared to unamended so ils was observed in this study, and it appears that appreciable changes in Al, Fe, and CEC from manure application do not occur in the short-term (wee ks). Our results indicate that, in the short-term, cattle manure amendments can increase the pH and the quantity of plant-available P and K in acid so ils.