Abstract: Experiments un the relationship of breaking plough pan in cultivated soils and the root growth of winter wheat plants were conducted during the last 3 years. It was observed that in the most of cultivated soils there existed a plough pan,the depth,thickness and solidity of which depended upon the methods of ploughing previously used,soil texture,etc.It usually lays at the depth of 15-30 cm with a mode of about 3U cm, a thickness of 5-10 em, a solidity of seve-ral to tens times as that of plough layer,twice to several times as that of sub-soil layer and a larger density than top and subsoil layers.Its existence pre-vented roots from growing down through it seriously. It was proved that breaking down the plough pan appropriately by ploug-king had a possitive effect on the improvement of its ecological conditions with a 2-3 times reduce of solidity,a significant decrease of density, an easy of per-eolation of soil water,an inc:ease of soil capasity on water depositing and holding,and an increase of the moisture content under 30 cm depth by '? to 2.5%.All of these benefited plant roots,reduced the horizontal roots by Z.7 to 13.6%and increased the vertical r outs by 4.1 to 7.6%."1'he number of secun-dart' roots and tuta.l weight of routs increased obviously.These effects were even evident when breaking plough ha.n was combined with a deep application of Y-fertilizer ofN-1' compound fertilizer into soil.It had a better effect un the #u1-lowing crops:runt activity incrf:ased inure and lasted longer than the first crop immediately after the measure,、、hick led to:、better drought and heat re-sistance in wheat hlanis,an increase of about U.t to:.J crams her I UOU gra-ins with an average of above 2 trams. T he total increase of grain yield ranged fro m 4.3%to 10.6%in first season but from 8.9%to 10.6%in the following seasons. In short,breaking plough pan could increase the grai:[yield for several ye-ars by putting into labour in one year.

Key words: Winter w heat, Rout, liesistance