PLOUGH PAN IMPACTS MAIZE GRAIN YIELD, CARBON ASSIMILATION, AND NITROGEN UPTAKE IN THE CORN BELT OF NORTHEAST CHINA

This study aims to investigate the responses of carbon assimilation, grain yield, leaf stay-green rate, nitrogen uptake and distribution to soil compaction in the hard plow pan caused by repeated use of tractor-driven cultivator in Northeast China. The typical hybrid maize variety “Zhengdan 958” was exposed to two treatments of simulated plow pan (SP) and simulated subsoiling (SS, control) in pot experiments from 2012 to 2014. Compared with SS, SP significantly reduced net photosynthetic rate (Pn) during growth stage, leading to a decrease in dry matter accumulation (DMA) and grain yield (GY) in three consecutive experimental years. Leaf stay-green degrees (LSD), which showed a fast descending trend from 20 days after silking (DAS), significantly decreased in the later filling stage under SP treatment. The translocation eciency of the stored N (TEN) in stalk and leaf to the grain during pre-silking was enhanced, whereas leaf and grain N concentration (LNC/GNC), together with N accumulation amounts at maturity were significantly reduced under SP treatment. Also, plough pan reduced the N distribution to the organs of stalk, leaf and grain. In conclusion, subsoiling is a possible way to delay leaf senescence and achieve higher DMA and GY, and increased grain N in the corn belt of Northeast China.