Die optimale K2O-Gabe zu Stärkekartoffeln in Abhängigkeit vom KDL-Gehalt auf nordwestdeutschen Sandböden

The results of 35 K fertilizer experiments on potatoes were evaluated. The double lactate soluble K contents in soil varied between 1,7 mg and 15 mg/100 g, the starch yield between 22 dt/ha (drought) and 115 dt/ha, and the economically optimum K 2 O application rate between 0 kg/ha and 295 kg/ha. The optimum K 2 O rate decreased significantly with increasing K contents in soil. The regression equation was: K 2 O [kg/ha] = 191-10,8 K DL [mg/100 g]. The K uptake and rainfall had no significant influence. Fertilizer recommendations with acceptable accuracy can be deducted on average, though not for each single harvest, because of the large deviation. The transformation of the experimental results into fertilizer recommendations for all sandy soils in Lower Saxony was discussed. As compared to the regression the current recommendations are by 50, 40 and 30 kg/ha K 2 O higher in soil test classes A, B and C, respectively. All recommended K rates are essentially lower than the K uptake.