EFFECT OF PLANTING DENSITY AND SKIPPING IRRIGATION AT CERTAIN GROWTH STAGES ON YIELD POTENTIALITY OF SOME MAIZE HYBRIDS

Two field experiments were conducted in the Experimental Farm of Gemmeiza Agriculture Research Station, Agricultural Research Center (ARC), Egypt during two growing seasons (2011 and 2012) to study the effect of three planting densities (20, 24 , and 28 thousand plants/fad.) and two missing irrigations (the 3^rd and 5^th irrigations or missing the 4^th and 6^th irrigations) out of six irrigations normally scheduled at 15 days intervals on yield potentiality of four maize hybrids (S.C. 10, S.C. 173, T.W.C. 324 and T.W.C. 352). Concerning the obtained results, the combined analysis revealed that applied 6 irrigations gave the highest means of the different studied characters, skipping the 3^rd and 5^th irrigations gave lower growth and grain yield attributes followed in descending order by missing the 4^th and 6^th irrigations. Then, both irrigation treatments caused significant reduction in grain and biological yields/fad., which reached 17.54 and 9.75% in grain yield as well as 10.36 and 11.19% in biological yield compared with normal irrigation, respectively. Maize hybrid S.C. 10 was superior in most growth and yield attributes as it recorded the highest grain and biological yields/fad., followed by S.C. 173 and T.W.C. 324 as well as T.W.C. 352 in descending order. Meantime, S.C. 173 produced the highest ear length and chlorophyll content. While T.W.C. 352 gave the highest mean for each of cob diameter, number of rows/ear and grain protein content. Data of the combined analysis revealed also, that increasing planting density from 20 to 24 and 28 thousand plants/fad., significantly increased leaf area index and grain and biological yields/fad., but, significantly decreased ear length. Planting density had significant effect on each of days to 50% tasseling and silking, LAI, stem diameter, plant height, ear height and diameter, cob diameter, number of rows/ear, number of kernels/row, thousand grain weight and protein content. Where their averages were decreased with the increase of density. The most interacting effect was observed between maize hybrids on one hand and each of water stress and planting density on the other hand. S.C. 10 and S.C. 173 as well as T.W.C. 324 had the highest grain yield averages under both normal and skipping the 4^th and the 6^th irrigations. However, under skipping the 3^rd and the 5^th irrigations, S.C. 173 and both S.C. 10 and T.W.C. 324 had higher grain yields than T.W.C. 352. Under both low and medium densities, each of S.C. 10, S.C. 173 and T.W.C. 324 recorded almost equal grain yield (ard./fad.) averages being heavier than T.W.C. 324 and T.W.C. 352. For both S.C. 10 and S.C. 173 any increase in planting density caused a significant increase in grain yield. For T.W.C. 324 both medium and high densities gave equal grain yield being heavier than low density whereas T.W.C. 352 recorded the highest grain yield from high density.