Spreading of manure water from biological treatment : Effect of high potassium level on maize

The liquid fraction obtained after settling of aerated swine manure represents 60 to 70 % of the total initial volume, and requires a spreading plan. To gain time and lower costs, it is generally spread with an irrigation system. A survey show that almost every year manure water is spread at an average level of 324 m3/ha, corresponding to an input of 780 kg of K2O per hectare. Repeated spreading thus enriches soil reserves of K2O. Two farm plots were monitored to detect any side effects on crops. Annual potassium oxide import targets were set at 0.2 and 5 times the levels of average exports in maize forage. On the experimental plots monitored since the end of 2001, only wheat/maize rotation was used. The soils that received manure water showed higher exchangeable K2O levels, but no visible effect on maize crops was observed.