FACTOR-ANALYSIS OF WINTER-WHEAT YIELD COM PONENTS IN VARIOUS YEARS AND CROP-ROTATION SCHEMES

Under the climatic conditions of Hungary, provided the biological basi s and production technology are satisfactory, the yield of winter whea t is determined by fertilisation, forecrop, irrigation and soil cultiv ation and preparation. The paper presents the results of studies made in order to clarify the correlations between these factors and yield c omponents, within the framework of a long-term experiment set up the L atokep Experimental Station of the Debrecen University of Agricultural Sciences. As regards water supplies, the following conclusions can be drawn from factor analysis on two different years (1988 and 1995). Th e effect of fertilisation was determined by the nature and water suppl ies of the year, to different extents depending on the crop rotation s cheme. In a year with average rainfall, i.e. if there is no drought, y ield stability can be assured by NPK fertilisation, which leads princi pally to an increase in plant number (spike number), associated with t he development of longer spikes (higher spikelet and grain numbers). I n a dry year after an unfavourable forecrop larger quantiliser active agent tend to reducenthe yield and the thousand grain mass due to the water deficiency. In a year with average rainfall increasing rates of NPK fertiliser play a dominant role in determining the yield of wheat grown after maize, while in a triculture (with pea as forecrop) only a loose correlation can be demonstrated between fertilisation and yield . The yield-increasing effect of irrigation is only of economic import ance in dry years, after both favourable and unfavourable forecrops. I n a dry year, after both maize and pea as forecrop, the thousand grain mass can be increased by irrigation at the right time, with the right method and with the right quantity. In the case of average rainfall a higher yield was not associated with an increase in thousand grain ma ss. The results of factor analysis give a good reflection of the corre lations between the various yield components. There is a close correla tion between plant and spike mass, the number of spikelets and grains per Spike and the grain mass per spike. In the case of water deficienc y (dry weather) this correlation is unable to promote an increase in y ield. The manner and depth of soil cultivation did not influence the s ize of the yield in either crop rotation scheme under the experimental conditions. Both soil loosening and ploughing were satisfactory for w inter wheat when carried out properly at the correct time.