The annual losses of calcium due to leaching have to be compensated. Also, all the acids which are introduced into the soil via rainfall, acidic fertilizers, etc. have to be neutralized. If this is not done, soil fertility will get worse every year.
Keeping the soil calcium content and the pH value at a propper level is called maintenance liming. Maintenance liming should be done every year or at least every 2-3 years.
To find out how much lime is needed for maintenance liming, we built a calculator to estimate the needed amount. Based on the reasearch of Dr. C.M.J. Sluijsmans (Institute for Soil Fertility Netherlands)