LEAFY REDUCED-STATURE MAIZE HYBRID RESPONSE TO PLANT-POPULATION DENSITY AND PLANTING PATTERNS IN A SHORT GROWING-SEASON AREA

Development of maize (Zen mays L.) types able to produce leaf area qui ckly and resist the stresses associated with high plant population den sities would increase maize yields in mid- to short-season areas. The leafy and reduced-stature traits each make contributions to this end. Our objective was to evaluate the effect of plant population densities (normal plant population density, 65,000 plants ha(-1); high plant po pulation density 130,000 plants ha(-1)) and planting patterns (76 cm r ow spacing, 38 cm row spacing, and paired rows with 20 cm between rows in a pair and 56 cm between roars of different pairs) on morphology a nd yield of one mid maturity commercial check hybrid [Pioneer 3902, (2 600-2700 corn heat units), non-leafy normal-stature (NLNS)] and the be st leafy reduced-stature (LRS) hybrid identified in previous work. The check (NLNS) and LRS hybrids responded differently to increased popul ation density, in terms of reproductive development and grain yield. C orn heat units from planting to tasselling, from planting to silking, and days from tasselling to silking were greater at the higher density , but the increase was less for the LRS genotype. Single plant grain y ield was decreased at the higher planting density for both LRS and NLN S; however, the decrease was greater for NLNS. Grain yield per unit ar ea was similar for NLNS under normal or high density, while the yield of LRS increased 30% under high density compared with normal density p lanting, to a level significantly greater than for NLNS. Plant height, internode length, ear height, and grain moisture content were all gre ater for NLNS, while above-ear leaf number and harvest index were grea ter for LRS, regardless of planting density or pattern. Plant height, internode length, ear height, and grain moisture content were greater under high density, while above-ear leaf area was greater under normal density, for both NLNS and LRS plants. Plant height, internode length , ear height, and grain moisture content were greatest for standard ro ws and least for narrow rows, while above-ear leaf area and grain yiel d per unit area were greatest for narrow rows and least for standard r ows, for both NLNS and LRS plants. The LRS hybrid matured one week ear lier than the NLNS hybrid. The LRS hybrid had earlier achievement of m aximum leaf area,more rapid silk extrusion. closer synchronization of pollen shed and silk extrusion, and more rapid growth of the first ear ; also, yield and harvest index were higher, and grain moisture conten t lower, than for the NLNS hybrid at the high plant population density , indicating better resistance to high plant population density stress for the LRS hybrid.