Abstract: It is difficult to increase grain yield (above 15 tha^-1) in irrigated plain of Inner Mongolia because of unclearness in exploring the productivity potential of high-yield spring maize colony. To solve this problem, we analyzed the yield components the yield performance parameters, and the effects of plant density on yield performance of different hybrids in split plot designs for 52 high yield maize colonies in four years,. The result showed that ear number and grain number per ear were the main factors affecting the yield of maize colony (above 15 tha^-1). The yield components of high yield colonies (above 15 t ha^-1) were as follows: 7.08×10⁴–9.60×10⁴ ears per hectare, 477–654 grains per ear, 324.7–388.7 g per 1000-grains and 168.9–234.0 g per ear. The rational indexes for high yield maize colony (above 15 t ha^-1) included the maximum LAI (leaf area index) of above 6.5, the MLAI (mean of leaf area index) of about 5.0, and the LAI at harvest stage was above 3.5. However, different hybrid cultivars demonstrated different rational yield components: cultivars with high stalk and large ear (yield over 15 tha^-1) should have 67 500–75 000 ears per hectare, 610–640 grains per ear, about 380 gram per 1000-grains, and 220–240 gram per ear; cultivars with medium or little ear on medium stalk (yield above 16.5 tha^-1) should have 75 000–97 500 ears per hectare, 520–600 grains per ear, 340–355 gram per 1000-grains, and 180–220 gram per ear. Enhancing plant density increased yield by high MCGR (mean of crop growth rate) and TGN (total grain number), but the decline in net assimilation capacity per plant resulted in remarkable reduction of GN (grain number) and thus restricted TGN potential. Adjusting population structure by increasing plant density brought about high yield above 15 tha^-1, which results from the compensation of population yield gain for individual productivity loss. Individual productivity in structure-optimized colony should be improved to break the limit of individual sink, and synchronous improvement in colony structure and individual function is the important approach to further raise yield of spring maize.

Key words: Spring maize, Yield performance, Quantitative analysis, High yield