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Two field experiments were conducted during two consecutive summer seasons of 2014 and 2015 in an administrative field at Diarb Negm District, Sharkia Governorate, under Agronomy Department supervision, Faculty of Agriculture, Zagazig University, Egypt. The aim of this study was to investigate the response of two yellow maize hybrids (Single Cross 176 and Three-way Cross 352) to three plant densities (20000, 24000 and 30000 plants/fad.), and nitrogen-farmyard combination fertilizer levels (60, 80 and100 kg N/fad., without addition of farmyard manure (FYM) and 60 kg N/fad.+20 m3 FYM/fad., 80 kg N/fad.+ 20 m3 FYM/fad., and 100 kg N/fad.+20 m3 FYM/ fad.) under clay soils conditions. The obtained results could be summarized as follows: The tried three maize plant densities had different effects on plant height (cm), ear diameter and length (cm), number of rows/ear, number of kernels/row, 100-kernel weight, kernel weight/ear, and biological yield (ton/fad.) during both seasons and their combined analysis, but the differences among the tried three maize plant densities on aforementioned traits did not reach the level of significance. Results of the first season and the combined analysis detected significant differences among the tried plant densities on ear yield/fad. Where, ear yield/fad., and grain yield/fad., in the first season and combined analysis, harvest index and grain: stover ratio in the two seasons and their combined analysis were significantly increased due to increasing maize density from 20000 or 24000 and up to 30000 plants/fad. Maize SC 173 cultivar appeared to produced taller plants, longer ears and larger number of kernels/row than TWC 352 cultivar. The later produced larger ear diameter, number of rows/ear, 100-kernel weight, kernel weight/ear, ear yield/fad., grain and biological yields/fad., than SC 173 one. No significant differences between two maize cultivars regarding harvest index and grain: stover ratio was observed. The first and the second increments in nitrogen levels up to 100 kg N/fad., with or without addition of farmyard manure was accompanied by a significant increase in ear diameter (cm), ear length (cm), number of rows/ear, number of kernels/row, 100-kernel weight (g), kernel weight/ear (g), ear yield/fad., grain and biological yields (ton/fad.) but harvest index and grain: stover ratio were reduced during both seasons and their combined analysis. These results finally recommend sowing maize cultivar TWC 352 with dense planting of 30000 plants/fad., and raising nitrogen level up to 80 kg N/fad., with addition of farmyard manure to maximize grain yield/fad., under the experimental site and other likely environmental condition. [ABSTRACT FROM AUTHOR]