EFFECT OF PLANT GROWTH REGULATORS ON MAIZE (ZEA MAYS L.) AGRONOMIC CHARACTERISTICS, STALK LODGING AND YIELD UNDER HIGH PLANTING DENSITY IN NORTHEAST CHINA

Lodging is one of the major factors that constrain grain yield stability and quality worldwide. Stalk lodging often reduce maize (Zea mays L.) grain yield and also causes difficulties in harvest operations. Plant growth regulators (PGRs) are often used widely to control lodging in modern high input cereal management. Two years field experiments were conducted with commercial PGRs of Yuhuangjin (YHJ) to determine their effects on spring maize growth, agronomic characteristics, grain yield and stalk lodging under high planting density in Jilin province, Northeast China. The results showed that, in all experiments, maize lodging-related characters of plant height (PH), ear height (EH), gravity height (GH), dry matter accumulation (DMA), internode 2 to 7 length (IL) were consistently reduced, and stalk bending strength(BS) of node 2 to7 were consistently enhanced by application of YHJ in both years. It is much more significant about above-mentioned character to apply with two (Sprayed twice, before elongation stage and V8 stage, respectively) or three (Sprayed three times, before elongation stage, V8 stage and before tasseling stage, respectively) times YHJ treatment. Maize grain yield, lodging score and HI were significantly influence by PGRs (T), Hybrids (H), and Year (Y). Grain yield increased and lodging score deceased significantly under YHJ treatment in high lodging year, but had little influence on grain yield in low lodging years. Application of YHJ could increase maize harvest index (HI) in all experimental years by reducing maize DMA significantly. Based upon these results, we concluded that PGRs could enhance stem lodging resistance during growth period, provided that they are used in right quantity and time. This is the optimal agronomic management in maize crops cultivated under high planting density in Northeast China.