EFFECT OF DAMAGE DUE TO SIMULATED HAIL IN JURY IN DIFFERENT PHENOPHASES ON THE GRAIN-YIELD FORMATION AND STALK STABILITY OF MAIZE

The aim of the experiments was to determine the leaf areareducing effe ct of hail, during various phenophases in the vegetation period of mai ze. It was found that the date at which damage took place was of prime importance. The most severe damage was caused during tasseling and du ring the phenophase following tasseling. A reduction in the leaf area also caused a reduction of dry matter content in the stalk, In agreeme nt with literary data, it was concluded that after mechanical leaf inj uries, the grain extracts nutrients from the stalk during the yield-fo rming period, manifested as a deterioration in the structure of the st alk. This leads to increased lodging in over-ripe maize, and facilitat es Fusarium infection. It was found that ear development was influence d to the greatest extent by at least 50% leaf area reduction after the beginning of tasseling Plants are able to respond to mechanical stres s arising prior to tasseling or during the tasseling phenophase by low er rates of seed set (kernel number reduction), while in phenopases la ter than tasseling the same injuries lead to a reduction in thousand k ernel mass. Even in the most sensitive periods, a leaf are damage of 2 5% led to no demonstrable loss of yield. The yield may be 15% lower th an im intact plants as the result of 50% leaf damage and 30% lower if leaf damage reaches 75%; the losses differ from one genotype to the ot her. The lowest yields are understandably combined with high thousand kernel mass (phenopases preceding tasseling), and poorer seed quality. In addition to results corresponding by and large to the literary dat a, great importance is attached to the date and degree of damage and t o the genotype suffering the damage. Work will be continued in this di rection.