Responses of Maize to Plant Population Density. II. Reproductive Development, Yield, and Yield Adjustments

Plant population density (PPD) exerts a strong influence on maize (Zea mays L.) growth and grain yield. Most PPD studies have usually confounded plant number with spatial arrangement, since row width remained constant and only spacing between plants in row was varied. This study used a systematic design (fan) to observe the effect of 15 PPD (0.8∓15.4 plants m⁻²) on maize reproductive growth in constant spatial arrangement on Lake fine sand (hyperthermic, coated Typic Quartzipsamments) at Gainesville, FL (29°38'N), in 1985 and 1986. All plants produced at least one ear over the 15 PPD range. Ear 2 and Ear 3 were lost at 4.3 and 2.8 plants m 2, respectively The kernel row number per ear (KRNE), kernel number per ear row (KNER), and kernel number per ear (KNE) were influenced by PPD and differed (P Ear 2 > Ear 3). Mean kernel weight (WK) was unaffected by PPD. Yield component vulnerability due to PPD for three-ear plants was: KNE and KNER > ear number per plant (ENP) > KRNE > WK. Kernel, stalk, and total dry matter yield per plant decreased reciprocally with increasing PPD. Kernel yield per land area increased parabolically up to a maximum yield of 1080 g m⁻² at about 10.0 plants m⁻², whereas stalk and total dry matter yield increased asymptotically up to 12.5 plants m⁻². Shelling percentage was constant with inceasing PPD, but harvest index decerased, though not significantly. We conclude that as PPD pressure is gradually removed over a wide PPD range, yield is adjusted in prolific maize hybrids first by KNE and KNER, followed by ENP, KRNE, and WK, which remained relatively stable. Contribution from the Inst. of Food and Agrcultural Sciences, Florida Agric. Exp. Stn. Journal no. 8406.