1 of 13Plant-Environment Interactions, 2025; 6:e70046 https://doi.org/10.1002/pei3.70046 Plant-Environment Interactions RESEARCH ARTICLE OPEN ACCESS Optimizing Maize Yield With Hybrids Tolerant of High Plant Density in West and Central Africa Wendm Ygzaw1   | Beatrice Elohor Ifie2,3  | Priscilla Francisco Ribeiro4  | Gloria Boakyewaa Adu5  | Eric Yirenkyi Danquah2  | Samuel Kwame Offei2  | Pangirayi Bernard Tongoona2 1Department of Plant and Horticultural Sciences, College of Dryland Agriculture and Natural Resources, Mekelle University, Mekelle, Ethiopia  |  2West Africa Centre for Crop Improvement (WACCI), University of Ghana, Accra, Ghana  |  3Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK  |  4CSIR – Crops Research Institute, Kumasi, Ghana  |  5CSIR-Savanna Agricultural Reseatch Institute, Tamale, Ghana Correspondence: Beatrice Elohor Ifie (bifie@wacci.ug.edu.gh) Received: 13 January 2025  |  Revised: 10 March 2025  |  Accepted: 11 March 2025 Funding: This work was supported by German Academic Exchange Service (DAAD); The Intra-Africa Academic Mobility Scheme; Africa Higher Education Centers of Excellence (ACE) Project. Keywords: F1 hybrid | maize | multiple environments | plant density ABSTRACT The use of high plant density tolerant maize hybrids was one of the most successful interventions that boosted maize yield in the developed world. However, very little research has been conducted in the improvement of maize for high plant density tol- erance in West and Central Africa (WCA). This study aimed to identify high plant density-tolerant maize hybrids adapted to multiple environments. Forty-eight maize hybrids were evaluated under three plant densities (low = 53,333, medium = 66,666, and high = 88, 888 plants ha−1). The experiment was conducted in four different environments in Ghana using 8 × 6 alpha lat- tice design with split plot arrangement. Plant density was the main plot and hybrids arranged in incomplete blocks within each plant density. The results revealed that the relative grain yield performance of the genotypes was dependent on plant density. Optimum plant density for the hybrids varied with growing environments. The highest grain yield of 9.5, 9.2, and 8.6 t ha−1 were obtained from the high plant density in Legon (minor season), Fumesua, and Legon (off-season), respectively, and it was 26.7%, 22.7%, and 30% increase in comparison to the respective yield under the low density. F1 hybrids M131 × CML16, CML16 × TZEI1, CML16 × 87,036, TZEI387 × CML16, and ENT11 × 87,036 are good candidates for high-density planting in high-yielding environ- ments. Grain yield performance of the maize hybrids was highest under high plant density for most of the growing environments. Thus, implementing high-density planting for maize hybrids could be one of the options for increasing maize yield in West and Central Africa. 1   |   Introduction Maize is an important cereal crop that ranks third after wheat and rice in its importance worldwide (Verheye 2010). It is the most widely cultivated and most important crop in Sub-Saharan Africa. In Ghana, it is the most widely cultivated crop with the highest area coverage next to cocoa (Ministry of Food and Agriculture (MoFA) 2021). However, the average yield of maize for the year 2021 in Africa and Ghana was 2.22 and 2.50 t ha−1, respectively, which is much lower than the world average of 5.88 t ha−1 (FAOSTAT 2024). Several factors are attributed to the low yield obtained in Ghana including pests and diseases, abi- otic stress, and agronomic practices. Globally, maize yield increased by more than double from 1961 to 2002 (Duvick  2005). Increased plant density was a single This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2025 The Author(s). Plant-Environment Interactions published by New Phytologist Foundation and John Wiley & Sons Ltd. https://doi.org/10.1002/pei3.70046 https://doi.org/10.1002/pei3.70046 https://orcid.org/0009-0005-3600-1851 mailto: mailto:bifie@wacci.ug.edu.gh http://creativecommons.org/licenses/by/4.0/ http://crossmark.crossref.org/dialog/?doi=10.1002%2Fpei3.70046&domain=pdf&date_stamp=2025-03-27 2 of 13 Plant-Environment Interactions, 2025 major change that had boosted the yield of maize, although different improved agronomic practices, improved varieties, and hybrids had also contributed to the yield increase (Fischer et al. 2014). The optimum plant density for maize depends on the nature of the genotype, agronomic practices, and the growing environment (Sangoi  2000). Plant density above the optimum for a particular genotype under a specific environment causes yield reduction due to increased competition between indi- vidual plants for necessary resources (Matthijs and Wu  2000; Sangoi 2000). In North America, maize is planted at an average density of 90,000 plants ha−1 or more as opposed to the 30,000 plants ha−1 which was practiced eight decades earlier (Assefa et al. 2018). It was also indicated that some varieties can give the highest yield when planted at 133,000 plants ha−1 in the USA (Mansfield and Mumm  2014). The good response of maize to increased plant density is partly attributed to its low tillering capacity (Fischer et  al.  2014). This low tillering ca- pacity makes it difficult for maize to fill the extra space when planted under low plant density (Sangoi 2000). However, old maize hybrids do not perform well under the contemporary high plant density (Fischer et al. 2014; Matthijs and Wu 2000; Sangoi  2000), indicating the role of genetic improvement in high plant density tolerance. The better performance of new hybrids under high plant den- sity indicates the possibility of exploiting the genetic basis of maize for improving high plant density tolerance. Moreover, the gradual and simultaneous increase of plant density and maize yield in the developed world (Duvick 2005; Fischer et al. 2014) indicates the possibility of increasing maize yield by improv- ing the high plant density tolerance of maize in the developing world. Plant spacing of 50 cm between plants and 75 cm between rows, with two plants per hill, or plant spacing of 25 cm between plants and 75 cm between rows, with one plant per hill (i.e., 53,333 plants ha−1) is the common practice of maize production in West and Central Africa. Adu et al.  (2014) recommended a higher plant density of 66,666 plants ha−1 for early maturing va- rieties in Ghana. Globally, the demand for maize is expected to increase by more than twofold in the coming 30 years due to an increase in population and changes in feeding habits (Aramburu-Merlos et  al.  2024). The increased demand should be fulfilled either by expanding the arable lands or by increasing the yield per unit area. The second alternative should, undoubtedly, be the preferred way of increasing maize production considering that arable lands are limited. In view of the improvements made in the developed world, there is a huge potential for increasing the yield of maize in Sub-Saharan Africa by introducing superior maize hybrids that are tolerant to high plant density. Despite its potential for increasing yield, only a few attempts have been made in Sub-Saharan Africa related to high plant density tolerance of maize, and most of them were either focused on the identification of optimum plant density for existing maize hy- brids, or they were tested only on a few locations with a limited number of hybrids (Ajayo et al. 2021; Buah et al. 2009; Kamara et al. 2020; Sibonginkosi et al. 2020; Worku et al. 2020). In most of these studies, 66,666 plants ha−1 were considered as high plant density which is, actually, very low compared to the 90,000 plants ha−1 average plant density in North America. Moreover, studies which were conducted in Ethiopia and Nigeria have integrated different levels of nitrogen fertilizer with the plant density ex- periment (Ajayo et  al.  2021; Worku et  al.  2020), which might obscure the real tolerance of the hybrids to high plant density. In Ethiopia, the highest yield was obtained from 90,900 plants ha−1 with the application of 360 kg ha−1 of nitrogen (Worku et  al.  2020). However, the experiment was conducted only in one location, two seasons, and one variety. Testing a substantial number of hybrids in many environments by applying similar ag- ronomic management and similar fertilizer rates to all plant den- sities would provide better results when selecting maize hybrids that are tolerant to high plant density. Therefore, this study was carried out to develop maize hybrids from existing inbred lines and identify hybrids that perform better under high plant density across different locations in Ghana and to determine the effect of high plant density on important agronomic traits of maize. 2   |   Materials and Methods 2.1   |   Planting Materials Forty-five single cross F1 hybrids of maize developed from a half diallel cross of 10 inbred parents, one three-way cross commer- cial check (PAN53), and two other single cross F1 hybrids were used in this study. The two additional single cross F1 hybrids were added to make the number suitable for alpha lattice. 2.2   |   Description of the Study Area The experiment was conducted in four different environments in Ghana in 2018 which included two seasons (minor season and off-season with irrigation) in Legon, the major season in Fumesua, and the rainy season in Nyankpala. The three differ- ent locations were selected because of the differences in their agro-ecological zones (Table 1). The sites also differed in their soil properties (Table 2). The same, fully fenced, experimental site was used in Legon for the minor season and off-season ex- periments. The difference between the minor season and the off-season experiments was mainly the temperature and method of water supply. Thus, the two different season experiments in Legon were considered as two different growing environments. Drip irrigation was used to water the plants in Legon during the off-season before the onset of rainfall and when there was a shortage of rainfall in the minor season. The agro-climatic con- ditions of the study sites are summarized in Table 1. Composite soil samples taken from at least nine random spots in each site were analyzed for selected soil properties in the labora- tory of the Department of Soil Science, University of Ghana. The results of the soil analysis are presented in Table 2. 2.3   |   Plant Densities and Field Evaluation The study had three factors, namely environment, genotype, and plant density with four, 48, and three levels, respectively. Forty-eight F1 maize hybrids were evaluated under three 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 3 of 13 different plant densities (low = 53,333, medium = 66,666, and high = 88,888 plants ha−1) in the four environments. The exper- imental design was an alpha lattice in a split plot arrangement. Each of the three plant densities was arranged in separate par- allel blocks (main plots of split plot design) where each of these main plots was divided into eight incomplete blocks, and each incomplete block contained six plots. Each plot was then as- signed with one random hybrid (8 × 6 alpha lattice within each plant density). A two-row plot of 4 m length each was used as an experimental unit. The inter-row spacing was kept at 75 cm for all plant densities, and thus, the intra-row spacing for the low, medium, and high plant densities were 25, 20, and 15 cm, respectively, resulting in each experimental plot being 6 m2. The plants at the start and end of each row were excluded during data collection to avoid border effect. Thus, the effective plot was 5.25, 5.4, and 5.55 m2 for the low, medium, and high plant density, respectively. Two seeds per hill were planted and later thinned to one plant per hill 14 days after planting. The treat- ments were replicated two times. Standard cultural practices including weeding and irrigation (when needed) were undertaken for each plot. Similarly, fer- tilizers (i.e., compound N P K and urea) were applied for each plot equally. The rate of fertilizer applied was 60 kg ha−1 P, 60 kg ha−1 K, and 120 kg ha−1 N. All the P and K and two thirds of the N fertilizers were applied 2 weeks after planting while the rest of the N fertilizer was applied 6 weeks after planting. A mix- ture of insecticides of Attack which contained 5% Emamectin Benzoate, and Hercules containing Fipronil (50 g l−1) was ap- plied two times a week to control termites and a fall army-worm infestation, until the plants started tasseling. Roundup, a non- selective herbicide, containing 360 g l−1 of glyphosate, was ap- plied pre-planting. After seedling emergence, hand weeding was carried out. Manual harvesting was carried out at maturity. 2.4   |   Data Collected Phenotypic data were taken using modified procedures de- scribed in Sangoi et  al.  (2001), Sharifi and Gholipouri  (2009), Alkhalifah (2013), Mansfield and Mumm (2014), and Al-Naggar et al. (2016) (Table 3). Plants at the start and the end of each plot (border plants) were not included in the data. Only plants that were properly bordered (spaced) were included in the data, and the effective plot size was adjusted. 2.5   |   Data Analysis Data were analyzed using SAS with PROC MIXED METHOD = REML. The denominator degree of freedom (DDF) was determined using the Satterthwaite method. Genotype, plant density, and environment were considered fixed while block and replication were considered as random effects. The model used in the data analysis (taking yield as an example) was: where, Yijklm is the yield of the ith genotype in the jth plant density, kth environment, lth block, and mth replication; μ is the overall mean; Gi is the fixed effect of ith genotype; Dj is the fixed effect of jth plant density; Lk is the fixed effect of the kth environment; GDij is the fixed interaction effect of the ith genotype and jth plant density; GLik is the fixed interaction Yijklm=μ+Gi+Dj+Lk+GDij+GLik+DLjk+GDLijk+Bljkm+Rmk+Eijklm TABLE 1    |    Agro-climatic conditions of the study sites. Environment Geographic location MAR (mm) MAT (°C) MT during experiment (°C) Agro-ecology Altitude (m.a.s.l) Legon-minor season 5°39′37″ N 0°11′28″ W 800 26.65 28.54 Coastal savanna 81 Legon-off season 5°39′37″ N 0°11′28″ W 800 26.65 27.75 Coastal savanna 81 Fumesua 6°42′53″ N 1°32′23″ W 1345 26.1 27.54 Transitional forest 293 Nyankpala 9°23′28″N1°00′28″ W 1075 28 27.93 Guinea savannah 180 Abbreviations: m.a.s.l, meters above sea level; MAR, mean annual rainfall; MAT, mean annual temperature; MT, mean temperature. Source: Abbam et al. (2018); AccuWeather (2019); Ghana Meteorological Agency (GMet) (2019); Ghana Statistical Service (2014a); Ghana Statistical Service (2014b); Kwame Nkrumah University of Science and Technology (KNUST) (2019); Ministry of Food and Agriculture (MoFA) (2016); Nkrumah et al. (2014); Savanna Agricultural Research Institute (SARI) (2019), Tontoh (2011). TABLE 2    |    Soil Chemical and Physical Properties of the Study Sites. Site/Soil properties Legon Nyankpala Fumesua pH (H2O1:1) 4.23 3.5 4.9 EC (μs/cm) 135.3 161.6 Avail P (mg/kg) 58.58 8.63 129.75 N (%) 0.05 0.046 0.025 C (%) 1.28 0.49 1.04 K (Cmol/kg) 0.4 0.02 0.06 CEC (Cmol/kg) 3.83 0.223 1.02 Particle Size (%) Sand 64.07 81.25 72.77 Silt 7.6 6.25 3.47 Clay 28.33 12.5 23.75 Texture Sandy Clay Loam Sandy Loam Sandy Loam 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 4 of 13 Plant-Environment Interactions, 2025 effect of the ith genotype and kth environment; DLjk is the fixed interaction effect of jth plant density and kth environ- ment; GDLijk is the fixed three-way interaction effect of ith genotype, jth plant density, and kth environment; Bljkm is the random effect of the lth block within jth plant density, kth en- vironment, and mth replication; Rmk is the random effect of the mth replication within the kth environment; and Eijklm is the experimental error. The data for percent root lodging, percent stem lodging, and per- cent barren plants were transformed with arc sin square root— Arc Sine (Y)1/2. Whenever significant differences were detected, pair-wise comparisons of the least square means were carried out using PDIFF of the LSMEANS statement in SAS which gives the “p” value for differences of LS-means together with standard error of the difference and t-value. From the pairwise com- parisons, only the comparisons of the performance of a given hybrid at the three plant densities were presented. This is to show if a given hybrid was tolerant to high plant density or not. The least square means of a trait for each plant density was presented, and similar letters were assigned to the least square means when the difference between the pair was not significant. TABLE 3    |    Methods of data collection on selected traits. Trait Method of data collection Number of upper leaves per plant Counting the number of leaves above the upper ear Chlorophyll content Taken from the leaf above the upper ear using SPAD 502 Chlorophyll Meter at the dough stage of the plant Leaf angle The angle between the vertical stem and the leaf was determined using an 11 cm length of protractor Plant height(cm) The length from the ground to the lowest branch of the panicle Ear heights The length from the ground to the node where the upper ear emerged Stem diameter The diameter of the second internode (from the ground), determined using a digital Vernier caliper Percent root lodginga (total number of roots leaning > 45°)/(total plant stand) ×100 Percent stem lodginga (total number of broken stems below the upper ear)/ (total plant stand) × 100. Determined 1 day before the harvesting date Tassel size Determined as (tassel branch number × tassel branch length); tassel branch length was determined as the average length of the lowest, middle, and upper tassel branches Days to 50% anthesis and 50% silkinga Number of days from planting to pollen shedding and visible silk in 50% of the plants, respectively Anthesis-silking interval (ASI)a Number of days between 50% anthesis and 50% silking. Days to physiological maturitya Number of days from planting until the husk of 90% of the plants changes to brown Percentage of barren plantsa (total number of plants bearing no ear or no kernel in their ears)/(total plant stand of the effective plot) × 100 Ears per planta (the total number of ears)/(total number of plants) Ear length and filled earl length The length of the whole ear and the length of the portion of the ear filled with kernels, respectively Ear diameter The diameter of the center of the ear, determined using a Vernier caliper Number of kernels per ear Rows per ear × kernels per row Hundred kernel weight Weight of 100 randomly sampled seeds Shelling percentage (grain weight/unshelled ear weight) × 100 Grain yield (t ha −1) at 15.5% moisture content ((grain yield per plot (kg) × 10,000 m2 ha−1)/ (effective plot area (m2)) × 1000 kg t−1). Grain yield per plant (g)a ((grain yield (kg ha−1) × 1000)/(respective number of plants in a hectare) aMeasurements were determined on a plot basis. The other traits were determined from five randomly selected samples. 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 5 of 13 3   |   Results 3.1   |   Performance of Vegetative, Phenology, and Tassel Related Traits of Hybrids Under Three Plant Densities Across Four Environments Plant density (PD) significantly affected most of the traits of the hybrids including ear height (EH), plant height to ear height ratio (PH/EH), anthesis-siking-interval (ASI), percent root lodging (RL), leaf angle (LA), stem diameter (SD), tas- sel size (TS), and chlorophyll content (ChC). However, the ef- fect of plant density was not significant for plant height (PH), days to 50% anthesis (DA), days to 50% silking (DS), percent stem lodging (SL), and upper leaf number (ULN) (Table  4). Environment (E) was also significant for most of the traits ex- cept in root lodging, stem lodging, and the tassel-related traits of the hybrids. Genotype × plant density interaction was sig- nificant only for ear height and plant height to ear height ratio. Genotype × environment interaction significantly affected all of the vegetative and phenology-related traits tested. Plant density × environment interaction significantly affected most of the traits tested except days to 50% anthesis, days to 50% silking, and percent stem lodging of the hybrids. However, the three-way interaction of genotype, plant density, and environ- ment was significant only for ear height, and plant height to ear height ratio of the hybrids. Days to maturity (DM), which was recorded only in Legon (off-season), was significant only for genotype but neither significant for plant density nor gen- otype × plant density interaction (Table 4). Ear height, leaf angle, and percent root lodging were signifi- cantly higher under the high plant density compared to the other densities (Table 5). Stem diameter and tassel size were sig- nificantly higher under the low density than the other densities. The lowest stem diameter, plant height to ear height ratio, and chlorophyll content were recorded under the high plant density. Anthesis-silking interval was lowest under the low plant density. 3.2   |   Yield and Yield Components of Hybrids Under Three Plant Densities Across Four Environments Genotype, environment, and plant density significantly affected grain yield, grain yield per plant (YPP), ears per plant (EPP), ear length (EL), filled ear length (FEL), ear diameter (ED), kernels per row (KPR), kernels per ear (KPE), hundred kernel weight (HKW), shelling percentage (SP), and percent barren plants (BP) (Table  6). However, rows per ear (RPE) were affected only by genotype. Similarly, the genotype × environment interaction and plant density × environment interaction were also significant for most of the traits including grain yield, ear length, filled ear length, ear diameter, kernels per row, kernels per ear, and shell- ing percentage. Ears per plant were significantly affected by the interaction of plant density and environment but not the inter- action of genotype and environment. Grain yield per plant, rows per ear, and hundred kernel weight were significantly affected by genotype × environment interaction, but plant density × envi- ronment interaction was not significant for these traits. Percent barren plants was not affected by any of the two-way interac- tions. The genotype × plant density interaction was significant only for grain yield and grain yield per plant. However, the gen- otype × environment × plant density interaction was not signifi- cant for all the traits (Table 6). Shelling percentage and percentage of barren plants were sig- nificantly higher under the high plant density compared to the medium and low plant densities for the hybrids (Table  7). However, ears per plant, ear length, filled ear length, ear diame- ter, kernels per row, kernels per ear, and hundred kernel weight were significantly lower under the high plant density compared to the other densities. The shelling percentage and percentage of barren plants were significantly lower under the low density compared to the other densities. However, ears per plant were significantly higher under the low plant density compared to the other densities. The performances of the other traits under the low density were similar to the medium density (Table 7). When the analysis was carried out for each environment for the hybrids, both genotype and plant density were significant in all four environments (Table 8). However, the genotype × plant den- sity was significant only in Fumesua but not in the other three environments. At each of the four locations, grain yield for the hybrids was low- est under the low density except at Legon during the off-season where yield under low and medium densities was not signifi- cantly different (Table  9). Grain yield was highest (p < 0.05) under high density in three of the locations while in Nyankpala, the fourth environment, yield under the medium density was significantly higher than yield under high density. When the grain yield of each hybrid under one plant density was compared to the respective yields under the other two densities, all the top 10 hybrids had significantly higher yields either in the high or medium densities than the low density in Fumesua (Table 10). The highest grain yield in nine of the top 10 hybrids was recorded under the high density but some of them were not significantly different from the medium den- sity. CML16 × 87,036, the highest yielding hybrid in Fumesua had a significantly higher grain yield (9.2 t ha−1) under high density than the low density (7.5 t ha−1) but the yield of the medium density was intermediate (8.3 t ha−1). Similarly, the second highest yielding hybrid in Fumesua, CML16 × 1368, had a significantly higher grain yield (9 t ha−1) under the high density than the medium density (7.0 t ha−1) and low density (6.2 t ha−1). The highest yielding hybrid in Legon (minor sea- son), M131 × CML16, produced a significantly higher grain yield (9.5 t ha−1) under high density than under the low density (7.5 t ha−1) but the yield of the medium density was intermedi- ate (8.2 t ha−1). Similarly, the second highest yielding hybrid, CML16 × ENT11, produced a significantly higher grain yield (8.4 t ha−1) under the high density than the medium density (6.6 t ha−1) and the low plant density (6.1 t ha−1) in Legon (minor season). However, the response of the top-yielding hybrids to differences in plant density in Legon (off-season) was lower than in Fumesua and Legon (minor season). Among the top four hybrids, only the highest-yielding hy- brid (ENT11 × 87,036) had a significantly higher grain yield (8.6 t ha−1) under the high plant density than under low plant density (6.6 t ha−1) in Legon (off-season) although the means were always higher under the high plant density (Table  10). 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 6 of 13 Plant-Environment Interactions, 2025 T A B L E 4      |     E ffe ct s o f g en ot yp e, p la nt d en si ty , a nd e nv ir on m en t o n ve ge ta tiv e, p he no lo gy , a nd ta ss el re la te d tr ai ts o f m ai ze h yb ri ds . So ur ce /t ra it PH E H PH /E H R L SL U L N L A N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p G 47 44 8 ** 47 45 9 ** 47 49 5 ** 47 49 3 ** 47 53 8 ** 47 54 1 ** 47 52 6 ** PD 2 14 7 N S 2 13 9 ** 2 49 5 ** 2 13 2 ** 2 82 N S 2 62 N S 2 97 * E 3 4 * 3 4 ** 3 49 5 ** 3 4 N S 3 4 N S 3 4 * 3 4 ** G  ×  P D 94 44 6 N S 94 45 6 ** 94 49 5 ** 94 48 9 N S 94 53 0 N S 94 52 9 N S 94 52 0 N S G  ×  E 14 1 44 3 ** 14 1 45 3 ** 14 1 49 5 ** 14 1 48 5 ** 14 1 51 5 * 14 1 50 6 ** 14 1 50 9 ** PD  ×  E 6 14 7 * 6 13 9 ** 6 49 5 ** 6 13 2 * 6 82 N S 6 62 * 6 97 ** G  ×  P D  ×  E 28 2 43 9 N S 28 2 44 8 ** 28 2 49 5 ** 28 2 47 9 N S 28 2 50 0 N S 28 2 48 2 N S 28 2 50 1 N S So ur ce /t ra it SD T S C H C D A D S A SI D M N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p G 47 49 7 ** 47 39 8 ** 47 25 4 ** 47 48 4 ** 47 49 2 ** 47 50 4 ** 47 11 6 ** PD 2 11 4 ** 2 56 ** 2 48 ** 2 11 9 N S 2 11 8 N S 2 10 4 ** 2 24 N S E 3 4 ** 2 3 N S 1 2 * 3 4 ** 3 4 ** 3 4 ** G  ×  P D 94 49 3 N S 94 39 0 N S 94 24 9 N S 94 48 0 N S 94 48 8 N S 94 49 9 N S 94 11 3 N S G  ×  E 14 1 48 6 ** 94 39 0 ** 47 25 4 * 14 1 47 5 ** 14 1 48 2 ** 14 1 49 1 ** PD  ×  E 6 11 4 ** 4 56 ** 2 48 ** 6 11 9 N S 6 11 8 N S 6 10 4 ** G  ×  P D  ×  E 28 2 48 0 N S 18 8 37 7 N S 94 24 9 N S 28 2 46 8 N S 28 2 47 6 N S 28 2 48 5 N S A bb re vi at io ns : A SI  , a nt he si s- si lk in g in te rv al ; C H C , c hl or op hy ll co nt en t; D A , d ay s t o 50 % a nt he si s; D D F, d en om in at or d eg re e of fr ee do m ; D M , d ay s t o m at ur ity ; D S, d ay s t o 50 % si lk in g; E , e nv ir on m en t; EH , e ar h ei gh t; G , g en ot yp e; LA , l ea f a ng le ; N D F, n um er at or d eg re e of fr ee do m ; N S, n ot si gn if ic an t ( p ≥  0. 05 ); p, p ro ba bi lit y va lu e (i. e. , P r >  F ); PD , p la nt d en si ty ; P H , p la nt h ei gh t; PH /E H , p la nt h ei gh t t o ea r h ei gh t r at io ; R L, ro ot lo dg in g; S D , s te m d ia m et er ; S L, st em lo dg in g; T S, ta ss el si ze ; U LN , n um be r o f u pp er le av es p er p la nt . ** p <  0. 01 , * p <  0. 05 . 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 7 of 13 The highest yielding hybrid in Nyankpala (CML16 × 87,036) had a significantly higher yield (7.9 t ha−1) under the me- dium density than the high density (5.0 t ha−1) and low density (5.3 t ha−1). Only one hybrid (TZMI740 × CML16), among the top ten hybrids, had a significantly higher grain yield (6.3 t ha−1) under the high density than the low density (4.3 t ha−1) in Nyankpala. Seven of the hybrids, among the top 10 highest yielding hybrids, in Nyankpala did not show yield differences across the three plant densities (Table 10). 4   |   Discussion 4.1   |   Response of Vegetative, Phenology, and Tassel Related Traits of Hybrids to Differences in Plant Density and Environment The non-significant interaction effect of genotype and plant density for most of the morphological and phenology-related traits and the non-significant three-way interaction effects for all these traits implies the relative performance of the hybrids for these traits was not dependent on plant density. The signif- icant interaction effect of genotype and environment implies the relative performance of the genotypes for these traits was dependent on the growing environment. The significant effect of genotype on almost all the vegetative, phenology, and tassel related traits tested except the tassel branch number implies the hybrids were genetically diverse for the vegetative, phenology, and tassel-related traits tested. The non-significant effect of plant density on plant height, in the current study, contradicts the findings of other re- searchers who have reported an increased plant height with an increase in plant density (Al-Naggar et  al.  2017; Brekke et al. 2011; Dawadi and Sah 2012; Mansfield and Mumm 2014; Nwogboduhu  2016; Sangoi and Salvador  1998). Generally, plant height increases with an increase in plant density. This is a mechanism that plants use to avoid being shaded by neigh- boring plants (Ford 2014). Crowded planting might reduce the ratio of red to far red radiations that reach the plant leaves, and this, in turn, initiates an increased apical dominance (Holalu and Finlayson 2017) which causes an increase in plant height especially in herbaceous plants (Ford 2014). However, under low plant density, there is a possibility of increased far-red ra- diation from horizontal reflection of light by the lower plant parts of neighboring plants which generally receive more light than under high density. Therefore, the plants under low den- sity which are exposed to horizontally reflected light could also grow taller depending on the proportion of the red and far-red radiations (Ford  2014). Similarly, plant height is also affected by the availability of soil nutrients, especially nitro- gen. Plant height at supra-optimum density was shorter than the plant height under the low densities when nitrogen fertil- izer was not applied (Boomsma et al. 2009). Thus, the effect of plant density on plant height is dependent on many other con- ditions including the nutrient status of the soil and the quality and intensity of the solar radiation. In the current study, the same amount of fertilizer was applied to all plots regardless of plant density, which means individual plants under the high plant density received lower amount of fertilizer than their counterparts under the low density. Therefore, it is possible that the lower amount (on plant basis) of fertilizer, especially nitrogen in the high density compromised the effect of shad- ing on increasing plant height. Similar to the current findings, Biswas et  al.  (2014) have reported that plant height did not change with increased plant density. Brekke et al. (2011) also reported no change in plant height with increased plant den- sity for maize plants from an unselected population. The increased ASI with increased plant density in the current study agrees with the findings of Sangoi et  al.  (2002) and Al- Naggar et al. (2017). However, Brekke et al. (2011) reported an increase in ASI with an increase in plant density in the unse- lected or less advanced selected population but not in the more advanced selected population. The non-significant effect of plant density on leaf angle in the current study is in contradic- tion to the findings of Al-Naggar et al. (2017) who reported that leaf angle decreased with an increase in plant density. However, Brekke et  al.  (2011) did not find any differences in leaf angle among plant densities. It was also reported that, generally, leaves of modern maize hybrids tend to be more upright and thus the shading effect of their leaves on the neighboring plants is minimized (Ford  2014). However, plants can also tend to shade neighboring plants by expanding their leaves so as to sup- press and outcompete the neighboring plants. The function of the leaves of plants when there is crowding is to photosynthesize and at the same time to shade neighboring plants (Ford 2014). Thus, in the current study, the tendency for shading neighboring plants might have caused the slight increase (2.9%) in leaf angle under high density. This indicates improvement in the erectness of the leaves of the hybrids is needed in order to make them more suitable for high-density planting. TABLE 5    |    Comparison of least square means of vegetative, phenology, and tassel related traits of hybrids among the three plant densities. Hybrids Trait/ Density EH (cm) ASI (days) SD (mm) PH/EH RL (%) LA (°) TBL (cm) TS CHC (spad value) High 92.1A 1.2A 17.3C 2.13B 6.7A 24.6A 20.4B 293.5B 47.4B Medium 88.1B 1.2A 18.8B 2.21A 3.8B 23.8B 21.2A 302.4B 51.8A Low 87.0B 1.0B 19.6A 2.22A 2.6B 23.9B 21.5A 313.3A 51.0A Note: Means with the same letter are not significantly different from each other. Abbreviations: ASI, anthesis-silking interval; CHC, chlorophyll content; EH, ear height; LA, leaf angle; PH/EH, plant height to ear height ratio; RL, root lodging; SD, stem diameter; TBL, tassel branch length; TS, tassel size. 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 8 of 13 Plant-Environment Interactions, 2025 T A B L E 6      |     E ffe ct s o f g en ot yp e, p la nt d en si ty , a nd e nv ir on m en t o n gr ai n yi el d an d yi el d co m po ne nt s o f h yb ri ds . So ur ce /t ra it G ra in y ie ld Y PP E PP E L FE L E D N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p G 47 46 9 ** 47 46 8 ** 47 53 5 ** 47 51 7 ** 47 51 6 ** 47 50 3 ** PD 2 13 0 ** 2 13 0 ** 2 61 .7 ** 2 93 .4 ** 2 10 0 ** 2 96 .3 ** E 3 4 ** 3 4 * 3 4 * 3 4 ** 3 4 ** 3 4 ** G  ×  P D 94 46 6 * 94 46 5 ** 94 52 3 N S 94 51 1 N S 94 51 0 N S 94 49 8 N S G  ×  E 14 1 46 2 ** 14 1 46 1 ** 14 1 50 2 N S 14 1 50 0 ** 14 1 50 1 ** 14 1 48 9 ** PD  ×  E 6 13 0 ** 6 13 0 N S 6 61 .7 * 6 93 .4 ** 6 10 0 ** 6 96 .3 ** G  ×  P D  ×  E 28 2 45 6 N S 28 2 45 5 N S 28 2 48 1 N S 28 2 49 3 N S 28 2 49 5 N S 28 2 48 3 N S So ur ce /t ra it R PE K PR K PE H K W SP B P N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p N D F D D F p G 47 53 7 ** 47 52 1 ** 47 51 4 ** 47 53 8 ** 47 53 3 ** 47 53 9 ** PD 2 59 .3 N S 2 87 .2 ** 2 86 ** 2 85 ** 2 91 .6 ** 2 71 .6 ** E 3 4 N S 3 87 .2 ** 3 4 ** 3 4 ** 3 4 ** 3 4 * G  ×  P D 94 52 4 N S 94 51 4 N S 94 50 7 N S 94 53 0 N S 94 52 6 N S 94 53 0 N S G  ×  E 14 1 50 1 ** 14 1 50 2 ** 14 1 49 6 ** 14 1 51 6 ** 14 1 51 4 ** 14 1 51 1 N S PD  ×  E 6 59 .3 N S 6 87 .2 ** 6 86 ** 6 85 N S 6 91 .6 * 6 71 .6 N S G  ×  P D  ×  E 28 2 47 8 N S 28 2 49 1 N S 28 2 48 8 N S 28 2 50 2 N S 28 2 50 2 N S 28 2 49 3 N S A bb re vi at io ns : B P, p er ce nt b ar re n pl an ts ; D D F, d en om in at or d eg re e of fr ee do m ; E , e nv ir on m en t; ED , e ar d ia m et er ; E L, e ar le ng th ; E PP , e ar s p er p la nt ; F EL , f ill ed e ar le ng th ; G , g en ot yp e; H K W , h un dr ed k er ne l w ei gh t; K PE , k er ne ls pe r e ar ; K PR , k er ne ls p er ro w ; N D F, n um er at or d eg re e of fr ee do m ; N S, n ot si gn if ic an t ( p ≥  0. 05 ); p, p ro ba bi lit y va lu e (i. e. , P r >  F ); PD , p la nt d en si ty ; R PE , r ow s p er e ar ; S P, sh el lin g pe rc en ta ge ; Y PP , G ra in y ie ld p er p la nt . ** p <  0. 01 , * p <  0. 05 . 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 9 of 13 4.2   |   Response of Yield and Yield Components of Hybrids to Differences in Plant Density and Growing Environment Significant genotype × plant density interaction for grain yield of the hybrids implies that the hybrids differed in their re- sponse to changes in plant densities. Similarly, significant plant density × environment interaction indicates the optimal plant density for the hybrids differed with growing environments. Moreover, significant genotype × environment interaction de- notes the relative performance of hybrids differed with envi- ronment. This signifies the need for selecting specific superior hybrids for specific growing environments. This is in line with the findings of Gebre (2005) who reported significant genotype and environment interaction in maize hybrids. Similar find- ings were reported by Seyoum et al. (2019) and Mansfield and Mumm  (2014) where the interactions of genotype and density were significant in maize hybrids. The interaction effect of genotype and plant density was, gen- erally, significant in the combined analysis. However, when a separate analysis was made for each environment, the inter- action effect of genotype and plant density was significant in Fumesua but not in the other environments. This implies the relative grain yield performances of the hybrids in the other three environments were not dependent on plant density. When the grain yield of each of the top ten hybrids at one plant den- sity was compared to the other two respective densities within each environment, the hybrids showed a differential response to plant density. For example, in Fumesua, the grain yield of CML16 × 87,036 was significantly higher under the high plant density than the low density but there was no difference in the yield of this hybrid at medium and low densities. The grain yield of M131 × CML16 was significantly higher under the high den- sity than the medium and low densities while the yield under the medium density was also higher than the low density. This means M131 × CML16 showed a significant yield increase both when the density changed from low to medium and from me- dium to high. However, the grain yield of CML16 × 87,036 sig- nificantly increased only when the density was changed from low to high, indicating the differential yield response of the genotypes to differences in plant density. Similarly, in the other three environments, some hybrids did not show variations in grain yield with changes in plant density while others showed significant variation in grain yield across plant densities which also indicated the differential response of the hybrids to plant densities. TABLE 7    |    Comparison of least square means of yield components of hybrids at three plant densities. Trait/Density EPP HKW (g) SP (%) BP (%) EL (cm) FEL (cm) ED (cm) KPR KPE High 0.94C 30.3B 83.2A 5.4A 13.8B 12.4B 42.9B 26.7B 377.9B Medium 0.98B 31.1A 82.8B 2.8B 14.6A 13.2A 43.8A 28.7A 407.2A Low 1.00A 30.9A 82.3C 1.1C 14.7A 13.4A 43.8A 28.8A 411.2A Note: Means with the same letter are not significantly different from each other. Abbreviations: BP, percent barren plants; ED, ear diameter; EL, ear length; EPP, ears per plant; FEL, filled ear length; HKW, hundred kernel weight; KPE, kernels per ear; KPR, kernels per row; RPE, rows per ear; SP, shelling percentage; YPP, grain yield per plant. TABLE 8    |    Effects of genotype and plant density on grain yield (t ha−1) of hybrids in each growing environment. Environment G PD G × PD Fumesua NDF 47 2 94 DDF 109 35.7 107 Pr > F < 0.0001 < 0.0001 0.01 Legon (off-season) NDF 47 2 94 DDF 114 35 112 Pr > F < 0.0001 0.0027 0.8395 Legon (minor season) NDF 47 2 94 DDF 111 31.3 109 Pr > F < 0.0001 < 0.0001 0.0811 Nyankpala NDF 47 2 94 DDF 123 23 120 Pr > F < 0.0001 0.0002 0.2948 Abbreviations: DDF, denominator degree of freedom; E, environment; G, genotype; NDF, numerator degree of freedom; PD, plant density. TABLE 9    |    Comparison of least square means of grain yield (t ha−1) of hybrids among the three plant densities in each of the growing environments. Environment/ Density Fumesua Legon (Minor) Legon (off-season) Nyankpala High 6.9A 6.4A 6.6A 4.6B Medium 6.2B 5.7B 5.9B 5.1A Low 5.5C 5.2C 5.5B 4.3C Range 3.7–9.2 2.4–9.5 3.3–8.6 0.9–7.9 Median 6.3 5.8 6 4.9 Note: Means with the same letter along the column are not significantly different from each other. 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 10 of 13 Plant-Environment Interactions, 2025 T A B L E 1 0     |      C om pa ri so ns o f g ra in y ie ld (t  h a−1 ) o f t op te n hy br id s a m on g th e th re e pl an t d en si tie s i n ea ch o f t he g ro w in g en vi ro nm en ts . Fu m es ua L eg on (o ff -s ea so n) L eg on (m in or s ea so n) N ya n kp al a G en ot yp ea PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) C M L1 6 ×  87 ,0 36 H 9. 2A EN T1 1 ×  87 ,0 36 H 8. 6A M 13 1 ×  C M L1 6 H 9. 5A C M L1 6 ×  87 ,0 36 H 5. 0B M 8. 3A B M 7. 0A B M 8. 2A B M 7. 9A L 7. 5B L 6. 6B L 7. 5B L 5. 3B C M L1 6 ×  13 68 H 9. 0A M 13 1 ×  C M L1 6 H 8. 5A C M L1 6 ×  E N T1 1 H 8. 4A M 13 1 ×  C M L1 6 H 5. 6A M 7. 0B M 6. 9A M 6. 6B M 6. 7A L 6. 2B L 6. 9A L 6. 1B L 7. 1A TZ EI 1 ×  87 ,0 36 H 8. 1A C M L1 6 ×  T ZE I1 H 8. 4A C M L1 6 ×  87 ,0 36 H 7. 0A PA N 53 H 6. 9A M 8. 7A M 7. 8A M 8. 0A M 7. 0A L 6. 0B L 6. 7A L 5. 1B L 5. 5A EN T1 1 ×  87 ,0 36 H 8. 5A C M L1 6 ×  87 ,0 36 H 8. 4A TZ dE I5 01  ×  E N T1 1 H 7. 1A B EN T1 1 ×  87 ,0 36 H 5. 1B M 7. 5A B M 7. 8A M 6. 2B M 6. 7A L 7. 1B L 7. 3A L 7. 9A L 5. 0B M 13 1 ×  C M L1 6 H 8. 3A TZ dE I5 01  ×  E N T1 1 H 8. 3A M 13 1 ×  E X P1 24 H 7.7 A M 13 1 ×  T ZE I7 H 4. 1B M 6. 9B M 5. 9B M 5. 0B M 6. 3A L 6. 5B L 5. 7B L 5. 8B L 5. 0A B 13 68  ×  87 ,0 36 H 8. 3A TZ dE I5 25  ×  M 13 1 H 8. 1A C M L1 6 ×  T ZE I1 H 7. 4A M 13 1 ×  E N T1 1 H 5. 1A B M 7. 6A M 7. 0A B M 6. 6A B M 6. 3A L 6. 0B L 5. 5B L 5. 5B L 4. 2B M 13 1 ×  T Zd EI 50 1 H 8. 2A M 13 1 ×  E N T1 1 H 7. 9A TZ dE I5 01  ×  C M L1 6 H 7. 4A TZ M I7 40  ×  C M L1 6 H 6. 3A M 7. 0A M 7. 5A M 6. 2A B M 5. 9A L 5. 4B L 6. 3A L 5. 6B L 4. 3B PA N 53 H 8. 0A TZ M I7 40  ×  E N T1 1 H 7. 8A EN T1 1 ×  87 ,0 36 H 7. 3A M 13 1 ×  T ZE I3 87 H 5. 4A M 6. 7B M 5. 6B M 6. 4A M 6. 0A L 7. 3A B L 5. 6B L 6. 5A L 4. 5A (C on tin ue s) 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 11 of 13 The better grain yield performance under the high density than the low density for most of the top ten hybrids in Fumesua and some of the top ten hybrids in Legon (off-season) and Legon (minor season) might imply the suitability of these environ- ments to high-density planting. Moreover, the highest grain yield in each of these environments was also obtained from the high-density planting which indicated the potential of these en- vironments, especially Fumesua, to support high-density plant- ing. Most of the top ten hybrids in Nyankapala did not respond to variations in density but some of them were better under the medium density compared to the high and low densities. This could imply that Nyankpla was not productive enough to sup- port the growth of more crowded maize plants in comparison to the other three environments. The soils in Nyankpala were rel- atively more acidic compared to other environments, and thus, this might hinder phosphorus absorption by plants (Tandzi et al. 2018) although the recommended fertilizer per unit area was applied. Moreover, the organic carbon content and cation exchange capacity (CEC) of the soil of Nyankpala were also very low compared to the other environments. Therefore, it could be because of these limitations in soil nutrients that Nyankpala was not productive enough for high-density planting, but it was suit- able for the medium density. It was reported that in general maize yield increased with an increase in plant density up to a certain limit but it declined with further increase of plant density except for very marginal conditions (arid environments) where maize may not respond to variations in plant density (Haarhoff and Swanepoel  2018). The peak might go up to 120,000 to 150,000 plants ha−1 depend- ing on the genotypes and growing environments (Haarhoff and Swanepoel 2018; Kosmelj et al. 2005). This implies that the hy- brids which performed best under the high plant density, in the current study, might or might not have reached the peak plant density beyond which their yields would decline. The same amount of fertilizer per hectare was applied to all three densi- ties. Moreover, the yield variability of the hybrids in response to plant density implies the importance of determining the op- timum planting density for a given maize hybrid rather than using blanket recommendations. The interaction of genotype and plant density was non-significant for almost all the yield components indicating the relative performances of the hybrids for these yield components did not show variations across plant densities. The reduction in the performance of the yield components such as ears per plant, number of kernels per ear, and hundred ker- nel weight with increasing plant density were in line with the findings of Al-Naggar et al. (2017). Similar to the findings of the current study, Sangoi et al.  (2002) reported an increase in the percent of barren plants with an increase in plant density. The reduction in the performance of most of the yield components and the increased of percentage barren plants under the high plant density could be because of the competition among the individual plants for limited resources. Under increased plant densities, inter-plant competition may cause the suppression of some plants by others, and the dominant plants will grow taller and shade the suppressed plants (Rossini et  al.  2011). In the current study, the increased shelling percentage with increased plant density implies the high plant density had a more drastic effect on the cob than on the kernels.Fu m es ua L eg on (o ff -s ea so n) L eg on (m in or s ea so n) N ya n kp al a G en ot yp ea PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) G en ot yp e PD L SM (t  h a− 1 ) C M L1 6 ×  T ZE I1 H 7. 9A C M L1 6 ×  T ZE I3 87 H 7.7 A M 13 1 ×  E N T1 1 H 7. 2A C M L1 6 ×  T ZE I7 H 5. 4A M 6. 6B M 4. 9B M 5. 6B M 5. 9A L 6. 1B L 5. 9B L 5. 8B L 5. 1A TZ M I7 40  ×  13 68 H 7. 9A TZ EI 1 ×  87 ,0 36 H 7. 5A C M L1 6 ×  T ZE I7 H 7. 2A TZ dE I5 01  ×  C M L1 6 H 4. 9A M 6. 0B M 6. 1A M 6. 3A M 5. 9A L 5. 2B L 6. 3A L 6. 1A L 5. 3A N ot e: M ea ns w ith th e sa m e le tt er a lo ng th e co lu m n ar e no t s ig ni fic an tly d if fe re nt fr om e ac h ot he r. A bb re vi at io ns : H , h ig h pl an t d en si ty ; L , l ow p la nt d en si ty ; L SM , l ea st sq ua re m ea n; M , m ed iu m p la nt d en si ty ; P D , p la nt d en si ty . a H yb ri ds a re se le ct ed b as ed o n th ei r h ig he st g ra in y ie ld in a ny o f t he th re e pl an t d en si tie s i n ea ch e nv ir on m en t. T A B L E 1 0     |     ( C on tin ue d) 25756265, 2025, 2, D ow nloaded from https://onlinelibrary.w iley.com /doi/10.1002/pei3.70046 by U niversity of G hana - A ccra, W iley O nline L ibrary on [23/04/2025]. See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense 12 of 13 Plant-Environment Interactions, 2025 Farmers in Sub-Saharan Africa could boost their maize yield by adopting hybrids that have superior performance under high plant density. Thus, policymakers in Sub-Saharan Africa should consider high plant density-tolerant maize hybrids as a means for increasing productivity and encourage studies on improving high plant density tolerance of maize. Among the limitations of the current study is the use irrigation in some experiments when most of the small-scale farmers in Africa do not have access to irrigation. Days to maturity, chlo- rophyll content, and tassel size were determined only from one, two, and three environments, respectively. Moreover, the eco- nomic trade-off between the increase in yield and cost of high- density planting was not examined. High plant density requires more labor for planting and fertilizer application. It also requires more seeds, but it might need less labor for weeding as high- density planting might suppress weeds. Therefore, further study of selected promising hybrids under more than three plant den- sities would provide more comprehensive understanding of the optimum plant density. Similarly, evaluations of selected supe- rior hybrids under different fertilizer levels across different plant densities would offer better information on the potential yield of hybrids under different plant densities. The cost-benefit analysis of high plant density should also be studied in the future. 5   |   Conclusion High plant density significantly reduced important yield com- ponents such as ear per plant, ear length, filled ear length, ear diameter, kernel per ear, and kernel per ear. However, the shell- ing percentage and percentage of barren plants were significantly high in the high plant density. The relative grain yield perfor- mance of the hybrids was dependent on plant density and on the growing environment. Similarly, the optimum plant density for the hybrids varied with growing environments. The highest grain yield in each environment was obtained from the high density except in Nyankpala where the highest yield was obtained from the medium density. A yield increase between 22.7% and 30% was obtained from the highest-yielding hybrids under high plant den- sity in the high-yielding environments compared to the respective yield under the low plant density. The increased number of plants per hectare in the high density compensated for the reduction in the ear per plant, ear length, filled ear length, ear diameter, kernel per row, and kernel per ear accounting for the high grain yield. This could also be attributed to the hybrids ability to tolerate high plant density which in this study is 88,888 plants ha−1. Generally, high-yielding environments were suitable for high plant den- sity while low-yielding environments for medium plant density. F1 hybrids M131 × CML116, CML16 × TZEI1, CML16 × 87,036, TZEI387 × CML16, and ENT11 × 87,036 are good candidates for high-density planting in high-yielding environments. Acknowledgments We acknowledge Intra-Africa Academic Mobility Scheme, German Academic Exchange Service (DAAD), Africa Higher Education Centers of Excellence (ACE) Project, and West Africa Centre for Crop Improvement (WACCI), University of Ghana for funding this study. We are also grateful to CSIR-Crop Research Institute (CRI), and CSIR-Savanna Agricultural Research Institute (SARI) for providing research infrastructure including research farms and laboratory instruments required during the multi- environment trials in their respective institutions. Conflicts of Interest The authors declare no conflicts of interest. Data Availability Statement The data that support the findings of this study are openly available in Dryad at https://​doi.​org/​10.​5061/​dryad.​sbcc2​frj9. References Abbam, T., F. A. Johnson, J. Dash, and S. S. 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See the T erm s and C onditions (https://onlinelibrary.w iley.com /term s-and-conditions) on W iley O nline L ibrary for rules of use; O A articles are governed by the applicable C reative C om m ons L icense https://www.fao.org/faostat/en/#data/QCL https://doi.org/10.3389/fpls.2014.00275 https://doi.org/10.2135/cropsci2018.01.0003 https://doi.org/10.1093/jxb/erw479 https://doi.org/10.2135/cropsci2013.04.0252 https://doi.org/10.2135/cropsci2013.04.0252 https://doi.org/10.4236/ijg.2014.57060 https://doi.org/10.4236/ijg.2014.57060 https://doi.org/10.9790/2380-0910010106 https://doi.org/10.1016/j.fcr.2011.01.003 https://doi.org/10.1016/j.fcr.2011.01.003 https://doi.org/10.1016/j.eja.2018.12.011 https://doi.org/10.9734/APRJ/2019/v3i3-430066 https://doi.org/10.3390/agronomy8060084 https://doi.org/10.1080/23311932.2020.1770405 https://doi.org/10.1080/23311932.2020.1770405 Optimizing Maize Yield With Hybrids Tolerant of High Plant Density in West and Central Africa ABSTRACT 1   |   Introduction 2   |   Materials and Methods 2.1   |   Planting Materials 2.2   |   Description of the Study Area 2.3   |   Plant Densities and Field Evaluation 2.4   |   Data Collected 2.5   |   Data Analysis 3   |   Results 3.1   |   Performance of Vegetative, Phenology, and Tassel Related Traits of Hybrids Under Three Plant Densities Across Four Environments 3.2   |   Yield and Yield Components of Hybrids Under Three Plant Densities Across Four Environments 4   |   Discussion 4.1   |   Response of Vegetative, Phenology, and Tassel Related Traits of Hybrids to Differences in Plant Density and Environment 4.2   |   Response of Yield and Yield Components of Hybrids to Differences in Plant Density and Growing Environment 5   |   Conclusion Acknowledgments Conflicts of Interest Data Availability Statement References