THE EFFECT OF FERTILIZER COATING ON THE N UTRIENT RELEASED FROM NPK FERTILIZERS

The behaviour of four coated samples of combined fertilizers with diff erent solubility was investigated in leaching experiments, in germinat ion test and three years model pot experiment conducted with silage oa t. The samples of coated fertilizers were prepared from the granules o f NPK fertilizer and coated the ureaform mixture. All treatments of co ated fertilizers were compared with an uncoated fertilizer. The basic properties and symbols of applied fertilizers are summarized in Tab. I . The positive effect of coated samples was shown in higher germinatio n of lettuce (Fig. 1) and in lower nitrogen leaching. The leaching of different forms of nitrogen is shown in Fig. 2 (medium-texture soil) a rid Fig. 3 (light-texture soil), leaching of total nitrogen in Fig. 4 (medium-texture soil) and Fig. 5 (light-texture soil). The best result s were found out with two lowest soluble samples. A different behaviou r of coated samples was not found in pot experiment. The yield drop an d lower nitrogen utilization by silage oat in coated fertilizers' trea tments were influenced by very low nitrogen release from the ureaform shell (Tabs II and III). The release of phosphorus and potassium from coated fertilizers was higher, it is other positive effect of fertiliz er shell (Tab. III).