EFFECT OF FERTILIZING AND PRUNING ON CHESTNUT LITTER PRODUCTION AND NUTRIENT RELEASE

A 49-year old chestnut (Castanea sativa Mill.) grove was studied from 1992 to 1999 in order to determine the effect of changing management practices on chestnut yield, litter production and nutrient release by litter components. From April 1992 to March 1996 the chestnut grove was only tilled 3 times per year, while from April 1996 to March 1999 it was fertilized, pruned and tilled 4 times per year. Management intensification increased total litter from an average of 4 Mg ha^-1 to 5 Mg ha^-1 due to an increase in leaves, burs and fruits. The biggest effect was in nut production which, on average, increased from 0.9 to 1.6 Mg ha^-1 of dry matter. As before the changes in management, leaves were the main litter component and the largest amount of nutrients released by the trees was in fallen leaves. In the 96/99 period, fertilization increased leaf nutrient concentration. This, together with the bigger amount of leaves produced in this period, resulted in a higher nutrient return to the soil. When the nutrient output due to removal of pruned biomass was considered, only the Ca, Mg and S litter balances were positive. However, the small amounts of fertilizers applied were appropriate to minimize the higher outputs. Results from soil samples collected in 1993 and 1999 showed higher exchangeable Ca, Mg, K, and extractable P in1999 than in 1993 and similar soil OM levels.