Understanding of maize (Zea mays L.) canopy structure and light transmission over a wide range of plant population densities (PPD) is necessary in the formulation of maize intercrop associations. Experiments using a systematic (fan) design were conducted on Lake fine sand (hyperthermic, coated Typic Quartzipsamments) at Gainesville, FL (29°38′N), in 1985 and 1986 to assess the interrelationships among maize canopy structure, light interception, and vegetative growth over 15 PPD (0.8 to 15.4 plants m−2). Fractional light transmission (by canopy levels at different times up to noon), leaf area index (LAI), total dry matter (TDM) yield, plant height, and tiller number were recorded. Light interception was similar at 5 and 3 h before and at solar noon for each PPD measured at ground, ear, and below‐tassel levels. Leaf area and light interception were highly concentrated at ear level, but level of light interception shifted upward with increasing PPD. Maxima LAI were 1.7, 2.6, and 4.0 at tasseling for the 1.7, 2.6, and 6.3 plants m−2 respectively. Light interception by tassels was approximately 2, 30, and 40% for 1.9, 3.5, and 6.3 plants m−2, respectively, while that for whole canopy was 75, 90, and 97%, respectively. As early as 35 d after planting (DAP) canopy interception was 40, 60, and 75% for 1.9, 3.5, and 6.3 plants m−2, respectively. Leaf area index, TDM, crop growth rate, and plant height were significantly influenced by PPD. Tiller number decreased linearly with increasing PPD to no tillers at 3.5 plants m−2. We conclude that increasing PPD of maize increases LAI and vegetative DM yield but alters light distribution within the canopy by shifting it from lower to upper canopy strata and increasing fraction intercepted by tassels.

Soybean [Glycine max (L.) Merr.] seed yield is influenced by planting date, pattern, and density of seeding, but cultivars differing in growth habit may vary in response to cultural treatments. Narrow‐row compared to conventional wide‐row plantings have consistently produced higher seed yields in the northern USA, where early maturity groups (MG) and indeterminate (INDT) types are commonly used. Positive responses to narrow rows have been less consistent in the southern USA, where late MG and determinate (DT) cultivars are common. Therefore, we hypothesize that this disparity in seed yield response to narrow‐row culture between the two areas is due to inherent differences in DT‐ and INDT‐type canopies resulting from their growth habits. This study, conducted in Gainesville, FL (29 ° 38′N) in 1984 and 1985, employed ‘Duocrop’ (INDT) and ‘Kirby’ (DT), May and July planting dates, 0.91‐, 0.61‐, and 0.30‐m interrow spacings, and 0.18‐ and 0.08‐m intrarow spacings in a Randomized Complete Block (RCB) design. Node and pod numbers, leaf area index (LAI), crop growth rate (CGR), total biomass, and seed yields were significantly increased (per unit land area) with increasing plant population density (PPD) up to a certain PPD, depending on spatial arrangement. The greatest seed yield of both INDT and DT types was from the May planting, narrow‐row culture (0.30 m), and high PPD, but response to PPD was confounded with squareness (ratio of intra‐ to interrow distance among plants) of planting pattern. High PPD (18 to 42 plants m−2 and high squareness values gave higher seed yields than combinations of lower PPDs and lower squareness values. We conclude that seed yield of both DT and INDT soybean in subtropical latitudes is optimized by May seeding, high PPD (40 plants m−2), and use of square planting patterns as approximated by narrow‐row culture.

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 < 0.05) among ears (Ear 1 > 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.

Planting peanut (Arachis hypogaea L.) in narrow rows with greater spacing between plants in order to approach a square pattern of plant arrangement can reduce competition and increase growth, especially during juvenility. Thus, this study was designed to assess the effects of planting pattern, genotype, and their interaction on seasonal vegetative growth, fruit growth and development, pod and kernel yields, and market quality. Seven genotypes, ‘Florunner’, ‘Tamnut’, and five experimental lines were used. Planting patterns (interrow × intrarow spacing) of narrow row (0.46 × 0.15 m), row [(0.69−0.23) × 0.15 m], and conventional row (0.91 × 0.08 were each established at 15 plants m−2 (150 000 ha−1) in mid‐April of 1985 and 1986. The soil was an Arreodondo loamy sand (loamy, siliceous, hyperthermic, Grossarenic Paleudult) on The Agronomy Farm located near Gainesville, FL. Plots were 6.1 m long and three rows wide (conventional) or four rows wide (narrow and twin row). Florunner, Tamnut, and line 84‐516 from the seven genotypes were sampled biweekly for growth analysis. Plants in the narrow‐ and twin‐row planting patterns, compared to the conventional, had significantly greater ground cover, leaf area indices, canopy light interception, crop growth rates, and yields of total dry matter, pods, and kernels. Planting pattern had no significant effect (P > 0.05) on market quality. Florunner and Tamnut were superior to the experimental lines in growth and kernel yield. Planting pattern and genotype interaction effects on pod and kernel yields were not significant. We conclude that planting patterns that approach equidistant spacing or a square arrangement can produce higher pod and kernel yields than conventional (wide) rows. Furthermore, either narrow‐ or conventional‐row patterns are suitable for screening or testing genotypes of diverse growth habit and market type.