INTRODUCTION  

 It has been reported that maize producers in many  parts of the world, particularly in developing countries  where good-quality data from local trials are not  available, rely on published information to make  agronomic decisions. Observing that many papers  have been published on the effects of plant  population on yield, but the results are associated  with prevailing local environmental conditions and  agronomic practices of each study. Stating that this  could lead to confusion among maize producers  regarding the most appropriate agronomic  management decision for their specific conditions and  farming systems. Thus, there is a need to indigenize  such studies to identify how plant population affects  maize grain yield under local conditions.  

It has generally been observed that maize yield in  Nigeria is low compared to some other countries in  Africa (Oloyede-Kamiyo and Olaniyan, 2020). While  the authors observed that the reason adduced to this  yield disparity has been low soil nitrogen, the problem  of pests and diseases as well as poor access to quality  seeds, they stressed that apart from these factors, one  other major cause of poor yield of maize in Nigeria is  suboptimal plant population. When adequate plant  population is not maintained, low yield results, are  observed Oloyede-Kamiyo and Olaniyan (2020). They  reported that the recommended plant population for  maize is 53,333 plants/haa at a spacing of 25cm within  a row and 75cm between rows at one plant per hill,  while a population density of 80,000 plants/ha was  found to be optimal for hybrids (Olaniyan, 2014;  Oloyede-Kamiyo and Olaniyan, 2020). 

Erenstein et al. (2022) observed that, since its  domestication some 9,000 years ago, maize (Zea mays  L.) has played an increasing and diverse role in global  agri-food systems. Stressing that global maize  production has surged in the past few decades,  propelled by rising demand and a combination of  technological advances, yield increases and area  expansion (Erenstein et al. 2022). The authors added  

production volume and is set to become the most  widely grown and traded crop in the coming decade.  In 2021, world maize production was 1,210 million  thousand tonnes; an increase from 308 million  thousand tonnes in 1972 with an average annual rate  of 3.18% (Erenstein et al. 2022). Maize (Zea mays L.)  plays a critical role in meeting the high food demand  and is globally one of the most widely cultivated crops  (FAO, 2017). Both the land area used for maize grain  production and the amount of maize produced per  unit area been increasing in recent years (FAO, 2017). It is one of the highest-yielding and most versatile  cereals, adding that the global demand for maize has  shown an increasing trend in the past decade (FAO  2009); with maize productivity increasing globally as a  result of improved genetics and agronomic practices.  

Oyewole et al. (2010) opined that the establishment  of adequate plant stands is a prerequisite for  successful crop production. In maize production, plant  population and row spacing are two key agronomic  factors known to have a strong influence on maize  grain yield (IPNI Canada (2018), stating that maize  yield is closely related to plant population, with more  plants meaning higher yield. However, there are  limitations to increasing plant population. The most  favorable planting densities for high yield in the  tropics are probably in the range of 65,000 to 75,000  plants/ha. Stressing that a population of less than  65,000 plants/ha is not advisable because a 10 percent  loss of plants is not uncommon under rainfed field  conditions (IPNI Canada, 2018). The report further  added that having more than 75,000 plants/ha will not  increase yield unless growing conditions are very  favorable with a yield potential of >13 t/ha. Adding  that for drought-prone environments, it is not  advisable to have more than 75,000 plants/ha (IPNI  Canada, 2018).  

The optimum plant population depends on several crucial factors, including soil fertility, soil water holding capacity, and hybrid maturity group, observed Sangoi et al. (2002). Modern hybrids possess the  ability to withstand greater stress attributable to high  population densities than older hybrids, which in turn  enables producers to establish higher plant  populations, leading to higher yields per unit area  (Russell, 1984; Duvick, 1997).  

The number of plants per unit area is influenced by the  distance between rows, the distance between plants  in a row, and the number of plants in a hill. Farmers  have been advised to, select an optimal plant spacing  that allows for ease of field operations, such as  fertilizer application or weeding, minimizes  competition among plants for light, water, and  nutrients, and creates a favorable micro-climate in the  canopy to reduce the risk for pests and diseases (IPNI  Canada, 2018). Narrow row widths of about 50 to 70  cm are recommended to ensure that sunlight falls on  the plants and not on bare soil.  

The agronomic practices implemented in a production  system should allow the selected germplasm to react  positively to the increased plant populations when  favorable environmental conditions occur (Haegele et  al. 2014) while also being tolerant to increased plant to-plant competition under suboptimal growing  conditions (Tokatlidis and Koutroubas, 2004). Changes  in agronomic practices such as fertilization, effective  weed control, and tillage practices can further alter  the relationship between population density and  maize grain yield. Thus, it is important to adjust the  plant population accordingly to achieve optimal grain  yields. Interactions between plant genotype and plant  population can also affect maize grain yield, with a  recent study conducted by DeBruin et al. (2017)  finding a positive relationship between maize grain  yields and plant population in modern hybrids, but a  contrasting response in older hybrids. Previous  reports observed that during the past six decades,  much work has been done to evaluate the effects of  plant population on maize grain yield in a wide variety  of environments and regions (Duncan, 1958; Pretorius  and Human, 1987; Ciampitti and Vyn, 2012; Hörbe et  al. 2013; Assefa et al. 2016; Qin et al. 2016); with the  observation that rainfall is a major determinant of  differences in agronomic practices used between  regions.  

The authors reported that in arid and semiarid  regions, rainfall is scarce and variable, and soil water  is often the most limiting factor for grain production.  Climatic conditions affect soil water content  throughout the growing season, influencing the number of plants per unit area the soil can maintain  throughout this period and, therefore, the optimal  plant population. Both plant population and row  spacing affect leaf canopy architecture (Sharratt and  McWilliams, 2005) and, in turn, affect crop uptake of water and nutrients, as well as light interception. They  pointed out that to justify the establishment of low  plant populations, rapid canopy closure is needed for  efficient resource use. Hammer et al. (2009) found  that at high plant populations, root architecture was  more important than canopy architecture and light  interception for increasing grain yield.  

As the human population is increasing with the total  land area remaining fixed, the problem of scarcity of  land for agricultural purposes is becoming pronounced. To feed this increasing population, the  productivity of available land must be increased. As  agricultural land becomes limiting, with the increasing  human population, planting more seeds/hole maybe a  justifiable means of addressing food scarcity. The  study was to determine the effect of increasing the  number of seeds/holes on plant growth,  development, yield components and yield of maize  under rainfed condition. 

MATERIALS AND METHODS 

A 3 x 4 Factorial experiment with three replications  was conducted to evaluate four plant population (53,  333, 106, 666, 159,999, 213,332 plants/ha) on growth,  development, yield and yield components of three  maize varieties (Local variety, Oba Super and Samaz  52). Variety was a main treatment factor with  population as sub treatment factor. The experiment  was conducted in the rainy seasons of 2021 and 2022  in Kogi State University Anyigba Students’ Research  and Demonstration Farm (Latitude 70 301 and  Longitude 70 091 E). The land was ploughed,  harrowed and ridged. The crops were spaced 25 cm x  75 cm in subplots measuring 4m by 5m and seeds  sown in line with the expected plant population per  hectare. To achieve the experimental population,  seeds were sown at either 1, 2, 3 or 4 seeds / hole, to  give, respectively 53, 333, 106, 666, 159,999, 213,332  plants/ha. Nitrogen fertilizer (NPK 20:10:10) was  applied in 2 split doses, starter doze at 2 weeks (60kg  N/ha, 30kg P2O5/ha and 30 kg K2O/ha) after planting  while crops were top dressed with Urea (46 % N) just  before tasseling. Weed management was manually  done with hoe at 2 and 6 weeks after sowing.  However, after tasseling, emerging weeds were hand-pulled. For the control of insect pests such as  grasshoppers, stem borers and Fall Army Worms  (FAW), Emamectin Benzoate was sprayed at the rate  of 30ml/16litres of water using a knapsack sprayer. 

Data Collection 

Six stands of crops were tagged in each net plot (3.5m  by 4.5m) for data collection throughout the period of  the experiment. Growth and development data were  collected at 2, 4, 6, 8 and 10WAS, while data on yield  components and yield were determined at the  termination of the trial. Data were collected on plant  height, being a measure of plant height from ground  level to the pick of the longest leaf (before tassel) or  the tassel (after tassel); Number of leaves per plant,  numerical counting of all fully unfolded leaves. Other  parameters collected were leaf area, and stem girth in  accordance with Oyewole et al. (2015 a & b). While  data on yield and yield components, such as cob yield,  cob weight and grain yield were also obtained over a  Metler weighing scale to two decimal places. 

Growth Parameters 

• Plant height (cm): The heights of each of the tagged  plants were measured using a meter rule; from the soil  surface to the apex and recorded an average of the  total plants measured. 

• Number of leaves per plant: This parameter was  obtained by a simple count of the total functional  leaves produced by tagged plants and recorded as  average numbers of leaves/plant. 

• Leaf area per plant (cm2): This was determined by  measuring the lamina length and maximum width,  multiple by a constant of 0.75 as described by  Oyewole (2011). 

• Stem girth (cm): This was determined with the aid of  veneer calipers and recorded as an average of six  tagged stands. Measurements were taken just above  the ground level. 

Yield Parameters 

• Number of ears/plant: The number of ears from  tagged plants in each net plot was averaged over the  number of tagged plants to obtain a mean number of  ears for the plant. 

• Ear length (cm): Lengths of harvested ears were  measured with the aid of measuring tape and  averaged over the number of harvests. 

• Ear weight (g): Harvested ears were weighed and  averaged over total harvests per net plot. 

• Threshing percentage: The harvested cobs were  weighed, threshed and the grains were weighed. The  result was expressed as ratios of grain weight over  total cob or ear weight expressed in percentage. 

• Number of kernels/ear: Kernels on the harvested  ears were manually striped counted and averaged  over the total number of sampled cobs/plot. • 100-grain weight: Samples of three batches of  hundred kernels per plot were drawn and weighed  and recorded as mean of three batches. 

• Grain yield: Cobs in the net plots were separately  harvested, threshed, winnowed and weighed to give  grain yield per plot (tons/ha). 

Analysis of Data 

Data collected were subjected to Analysis of Variance  (ANOVA) as described for Factorial Experiment  (Statistical Analysis System (SAS), 1998) and means  found to be statistically significant at 5% probability  were separated using LSD. 

RESULTS AND DISCUSSION 

Effect of increasing maize population per stand on  height (cm) of three varieties of maize 

Plant height at maturity (cm) is an important  component which helps in the determination of the  growth attained during the growing period (Abuzar et  al. 2011), however height is dependent on many  variables, among which are variety used, nutrient  available, as well as plant population among other  factors. Generally, it has been observed that  agronomic practices implemented in a production  system should allow the selected varieties to react  positively to increased plant populations when  favorable environmental conditions occur (Haegele et  al. 2014) while also being tolerant to increased plant to-plant competition under suboptimal growing  conditions (Tokatlidis and Koutroubas, 2004). While  stressing that changes in agronomic practices such as  fertilization, effective weed control, and tillage  practices can further alter the relationship between  population density and maize grain yield. Thus, it is  important to adjust the plant population accordingly  to achieve optimal grain yields. Analysis of data in this  trial showed that variety investigated significantly  (p≤0.05) influenced crop heights at 4, 8 and 10WAS in  the 2021 cropping season (Table 1) and at 4, 6, 8 and  10WAS in the 2022 cropping season. At the end of the  trial, Sammaz 52 recorded the tallest crops in both seasons (385.71 cm and 340.83 cm, respectively in the  2021 and 2022 seasons), while the local variety  recorded the tallest crops (363.11 cm) in the 2021  trial, while coming behind the other two varieties in  2022 trials. It should be expected that taller plants will  lodge easily and are likely to break as a result of the  wind effect (Oyewole et al. 2015a & 2015b). This will  be more pronounced where an increase in plant  height is not complemented by thicker plant stems /  girths and where cobs are also borne high up the  stems, which put more weight towards the top of the  crop; such weight may make the plant tilt over under  the influence of wind. 

Table 1: Effect of increasing maize population per stand on height (cm) of three varieties of maize (Zea mays)  in 2021 and 2022 cropping seasons 

Treatment	2021 Cropping Season				2022 Cropping Season
	Height (cm)
	4WAS	6WAS	8WAS	10WAS	4WAS	6WAS	8WAS	10WAS
Variety
V1: Sammaz  52	78.95a	139.99	304.91b	385.71a	77.79a	140.83a	303.00a	340.83a
V2: Oba  super-II	63.56b	138.78	290.02c	356.25c	65.95b	143.08a	301.06a	338.83a
V3: Local  Variety	64.53b	140.49	318.04a	363.11b	63.61b	121.42b	275.39b	297.92b
LSD (0.05)	3.671*	NS	12.754*	7.891*	6.885*	13.895*	17.987*	12.761*
Population
P1: 53,333  pop/ha	62.05d	125.54d	281.70b	337.48c	60.56b	112.67d	228.39d	253.67c
P2: 106,666  pop/ha	64.95cd	137.36c	293.41b	356.29b	65.67b	134.78c	303.21c	336.44b
P3: 160,000  pop/ha	67.33bc	141.94b	293.73b	367.50b	73.59a	140.22b	309.70b	344.44b
P4: 213,332  pop/ha	72.74a	155.18a	348.44a	412.15a	77.74a	152.77a	331.27a	368.89a
LSD (0.05)	2.781*	4.721*	15.932*	13.732*	6.223*	4.881	3.612	9.657*
Interaction
V1P1	67.59bc	125.22f	271.02f	351.99	72.40	118.00	288.40	318.00
V1P2	69.27b	141.21cd	297. 10de	377.21	72.80	144.33	304.23	344.33
V1P3	70.17b	141.55cd	300. 45cd	388.41	81.30	144.66	313.23	344.66
V1P4	81.76a	151.99b	351. 05b	425.22	84.66	156.33	306.13	356.33
V2P1	58.85e	128.17f	282. 31e	338.77	59.66	130.00	289.44	318.00
V2P2	61.58cde	134.64e	287. 01e	344.66	62.26	135.00	300.21	330.00
V2P3	65.95bc	142.87c	282. 54e	342.77	70.23	147.00	304.23	347.00
V2P4	67.93bc	149.44b	308. 23c	398.78	71.63	160.33	310.34	360.33
V3P1	59.70de	123.22f	291. 77de	321.67	49.63	90.00	107.34	125.00
V3P2	64.00bcde	136.23d	296. 12d	346.99	62.66	125.00	305.20	335.00
V3P3	65.87bcd	141.41cd	298. 22d	371.33	69.23	129.00	311.67	341.66
V3P4	68.53b	161.11a	386. 04a	412.45	72.93	141.66	377.34	390.00
LSD (0.05)	6.781*	5.329*	8.712*	4.672*	3.526*	8.782*	3.884*	9.563*
CV%	14.45	8.83	13.35	21.72	16.56	11.56	18.67	17.77

Means with the same letter(s) are not significantly different at 5% level of probability

Table 2: Effect of increasing maize population per stand on number of leaves of three varieties of maize (Zea  mays) in 2021 and 2022 cropping seasons 

Treatment	2021 Cropping Season				2022 Cropping Season
	Leaf Number
	4WAS	6WAS	8WAS	10WAS	4WAS	6WAS	8WAS	10WAS
Variety
V1: Sammaz 52	8	10	12	12	8	10	12	12
V2: Oba super-II	7	10	11	12	7	10	11	13
V3: Local Variety	7	10	11	13	7	10	11	13
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
Population
P1: 53,333  pop/ha	8	10	11	13	8	10	12	13
P2: 106,666  pop/ha	8	10	11	13	8	10	11	13
P3: 160,000  pop/ha	7	9	11	12	7	9	11	12
P4: 213,332  pop/ha	7	10	11	12	7	10	11	12
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
Interactions
V1P1	8	10	12	12	7	10	12	12
V1P2	8	11	11	13	8	11	13	13
V1P3	8	9	12	12	7	10	12	13
V1P4	8	9	11	12	8	9	11	12
V2P1	7	9	12	12	8	10	12	11
V2P2	7	10	11	12	6	10	10	12
V2P3	7	10	10	13	6	10	11	13
V2P4	7	10	11	13	8	9	9	12
V3P1	8	9	11	13	8	9	11	12
V3P2	7	10	11	13	5	9	11	12
V3P3	7	9	11	13	7	9	11	12
V3P4	7	10	11	13	8	9	10	12
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
CV%	11.37	7.99	8.04	5.17	17.24	4.73	7.29	15.02

Means with the same letter(s) are not significantly different at 5% level of probability Walker, 1989), and this competition leads to leaf  

There was a significant (p≤0.05) influence of  population investigated on crop heights at 4, 6, 8, and  10WAS in both seasons, with early signs of leaf  etiolation observed due to competition for solar  radiation (Hay and Walker, 1989) as seeding rates  increase (Oyewole, 2011). Seeding at four seeds per  hole consistently gave the tallest crops, followed by  seeding three seeds per hole, with one seed per hole  giving the shortest crops at 4, 6, 8 and 10WAS in both  seasons; definitely because this experienced the least  competition for solar radiation, compared with other  treatment. Understandably, as crops are clustered  together, they compete for solar radiation (Hay and  

elongation (Oyewole, 2011; Hay and Walker, 1989). It  is expected that the higher the population per unit  area, the stiffer the competition for solar radiation  (Oyewole, 2011; Hay and Walker, 1989), thus  producing taller crops as observed in this trial. The  observation is in line with the outcomes of trials  conducted by Oyewole et al. (2015a and 2015b). In a  similar experiment conducted by Abuzar et al. (2011)  data showed that plant height was significantly  affected by plant population densities, which they  observed was due to crowding effect of the plant and  higher intra-specific competition for resources.  Sangakkara et al. (2004) explained that as the number 

of plants increased in a given area the competition  among the plants for nutrients uptake and sunlight  interception also increased, with competition for  sunlight leading to increase in plant heights. It is,  however not uncommon to find stunted plants with  increasing plant population, particularly in an  environment where major crop nutrients are critically  limiting. Planting at one seed / hole gave the shortest average crop height at the end of the trial (337.48 cm  in 2021 and 253.67 cm in 2022 cropping seasons),  while the tallest average plant height at the end of the  trial were observed when four seeds were sown per  hole (412.15 cm 368.89 cm, respectively in 2021 and  2022 cropping seasons). 

Table 3: Effect of increasing maize population per stand on leaf area (cm²) of three varieties of maize (Zea  mays) in 2021 and 2022 cropping seasons 

Treatment	2021 Cropping Season				2022 Cropping Season
	Leaf Area (cm2)
	4WAS	6WAS	8WAS	10WAS	4WAS	6WAS	8WAS	10WAS
Variety
V1: Sammaz 52	149.94	405.07	414.79	340.34	149.94	405.17	415.59	341.34
V2: Oba super-II	126.50	388.09	414.17	355.67	128.25	388.09	414.43	355.67
V3: Local Variety	123.72	353.22	407.07	349.60	124.22	350.04	406.51	349.60
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
Population
P1: 53,333  pop/ha	150.77	420.18	464.67a	416.85a	150.77	420.32	465.74a	417.33a
P2: 106,666  pop/ha	138.06	397.31	426.74ab	359.06ab	138.06	398.02	427.09ab	359.39b
P3: 160,000  pop/ha	126.01	357.11	381.28b	317.92b	128.13	356.45	381.59b	318.10b
P4: 213,332  pop/ha	117.44	353.91	375.35b	300.31b	119.59	349.62	374.30b	300.65c
LSD (0.05)	NS	NS	57.960*	66.580*	NS	NS	58.160*	55.370*
Interactions
V1P1	146.79	413.19	435.51	383.23	171.65	517.34	497.96	436.45
V1P2	165.53	473.79	475.24	347.41	182.62	497.26	447.96	378.98
V1P3	151.39	377.64	379.16	333.08	180.92	438.80	413.33	376.57
V1P4	136.02	355.66	369.23	297.61	150.08	359.99	379.34	288.42
V2P1	123.70	399.41	375.17	350.34	150.09	435.27	363.66	396.40
V2P2	123.70	438.22	469.71	379.63	84.47	403.81	437.70	297.56
V2P3	109.96	361.34	399.89	326.71	154.33	443.69	459.23	361.20
V2P4	141.50	353.36	411.92	399.33	106.30	302.91	358.68	367.50
V3P1	145.20	380.65	449.05	467.99	88.12	302.68	324.95	425.95
V3P2	106.33	347.19	432.79	350.12	80.60	364.64	444.87	331.60
V3P3	107.54	332.35	364.78	303.67	120.48	398.63	420.09	293.70
V3P4	135.74	352.69	381.65	276.59	123.62	338.86	307.10	135.77
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
CV%	26.63	18.10	16.73	21.57	12.64	11.56	19.91	22.19

Means with the same letter(s) are not significantly different at 5% level of probability

Table 4: Effect of increasing maize population per stand on stem girth (cm) of three varieties of maize (Zea  mays) in 2021 and 2022 cropping seasons 

Treatment	2021 Cropping Season				2022 Cropping Season
	Stem girth (cm)
	4WAS	6WAS	8WAS	10WAS	4WAS	6WAS	8WAS	10WAS
Variety
V1: Sammaz  52	3.52	4.84	5.51	5.69	3.49	5.11	5.75	6.00
V2: Oba  super-II	3.23	5.37	5.49	5.80	3.23	5.55	5.69	5.77
V3: Local  Variety	3.24	5.17	5.54	5.70	3.24	4.81	5.42	5.81
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
Population
P1: 53,333  pop/ha	3.44	5.61a	5.87a	6.22a	3.58	5.84a	6.29a	6.43a
P2: 106,666  pop/ha	3.53	5.52a	5.67a	5.91ab	3.41	5.79ab	5.64a	5.93ab
P3: 160,000  pop/ha	3.09	4.84b	5.45ab	5.55bc	3.58	5.29b	5.69a	6.03bc
P4: 213,332  pop/ha	3.24	4.52b	4.93b	5.23c	3.11	4.55c	4.85b	5.05c
LSD (0.05)	NS	0.496*	0.521*	0.603*	NS	0.543*	0.642*	0.592*
Interactions
V1P1	3.53	5.02	5.35	5.76	4.26	5.83	6.70	6.70
V1P2	4.14	5. 21	5.92	6.07	4.20	5.23	5.96	6.43
V1P3	3.27	4.66	5.72	5.72	3.53	4.40	5.13	5.60
V1P4	3.14	4.45	4.97	5.19	3.40	4.96	5.20	5.26
V2P1	3.31	5.83	6.13	6.26	3.67	6.63	6.50	6.60
V2P2	3.35	5.76	5.76	6.30	2.80	5.20	5.53	5.60
V2P3	3.04	5.10	5.46	5.50	3.86	5.56	6.16	6.23
V2P4	3.20	4.77	4.82	5.13	2.86	4.80	4.56	4.63
V3P1	3.49	5.97	6.13	6.65	2.83	5.06	5.66	6.00
V3P2	3.11	5.58	5.32	5.35	3.23	5.43	5.43	5.76
V3P3	2.97	4.76	5.18	5.43	3.36	4.83	5.78	6.23
V3P4	3.39	4.35	4.99	5.37	3.06	3.90	4.80	5.26
LSD (0.05)	NS	NS	NS	NS	NS	NS	NS	NS
CV%	16.59	10.19	9.95	10.76	6.61	12.87	8.54	12.48

Means with the same letter(s) are not significantly different at 5% level of probability  

There were statistically significant interactions  between variety and plant population on plant height  at 4, 6, 8 and 10WAS in both seasons; an indication  that the variety investigated were significantly  influenced by variation in population per unit area. The observed interaction is not unexpected, as it has been observed that agronomic practices implemented in a production system should allow selected varieties to react to plant population manipulations when favorable environmental conditions occur (Haegele et  al. 2014). 

Effect of increasing maize population per stand on  number of leaves, leaf area and stem girth of three  varieties of maize 

Plant leaves play crucial role in crop photosynthesis,  any effect of imposed treatment on either leaf number or leaf area which may impact on photosynthesis should probably be expected to affect crop yield. Worthy of note, however is the fact that  the process of yield formation involves complex  interplays of various yield determining factors  (Jamileh and Moghadam, 2015), besides leaf number  and leaf area (Hay and Walker, 1989) with usually  unpredictable outcomes. Such varying factors which  may affact sink-source relation may moderate  expectations away from basic principles. However, in  this trial analysis of data indicated that variety as well  as population investigated did not significantly (p ≥  0.05) influence number of leaves at 4, 6, 8 and 10WAS  in 2021 and 2022 cropping seasons (Table 2). There  were also no observed interaction effects between  variety and population on leaf number in both seasons  (Table 2). Oyewole et al. (2015b) observed that where  leaf formation is gene dependent, leaf number may  not respond to agronomic practices; such as  population manipulation; this may be particularly so  in determinate crops such as maize. While it could be  deduced that the non-significant effect of the  treatment imposed on leaf numbers, could be an  indication of a possible non-significant effect on yield  outcomes, seeing that leaves are vital in crop  photosynthesis; with Valadabadi and Farahani (2010)  reporting that photosynthesis increases by  development of leaf area. However, reports have  shown that soil water is often the most limiting factor  for grain production in arid and semiarid regions  (Sharratt and McWilliams, 2005), while Hammer et al.  (2009) found that at high plant populations, root  architecture was more important than canopy  architecture and light interception for increasing grain  yield. 

Leaf area is an important parameter of maize. Data  analysis indicated that variety did not significantly (p≥  0.05) influence leaf area at 4, 6, 8 and 10WAS in 2021  and 2022 cropping seasons (Table 3). Generally, leaf  area increased among the variety though not  significantly at 4WAS to 8WAS then dropped at 10  WAS. Plant population significantly (p≤0.05)  influenced leaf area at 8 and 10WAP in both seasons,  but not at 4 and 6WAS in 2021 and 2022 cropping  seasons. Leaf area was observed to diminish as plant  population per stand was increased from one to four  plants / stand. Thus, the highest leaf areas were  observed in one plant / stand. Just as observed in  outcome of variety above, leaf area increased among  studied population through 4WAS to 8WAS then  dropped at 10WAS. The drop in leaf areas could be  attributed to leaf senescence. There were no  observed interaction effects between variety and  population on leaf area in both seasons throughout the period of data collection (Table 3). The significant  effect of population on leaf area conformed to the  report of Valadabadi and Farahani (2010) who  reported that leaf area, among other things, is  influenced by plant population. Observing that the  highest physiological growth indices are achieved  under high plant density, because photosynthesis  increases by development of leaf area. Previous  research findings also indicated that in high maize  density, leaf area index and crop growth rate  increased than low maize density throughout crop  growth season (Saberali, 2007). 

Data analysis showed that variety investigated did not  significantly (p≥ 0.05) influence stem girth at 4, 6, 8  and 10WAS in 2021 and 2022 cropping seasons (Table  4), while population had significant effect on stem  girth at 6, 8 and 10WAS. At the termination of the trial,  the widest stem girth was recorded in the single maize  stand in 2021 and 2022 cropping seasons (6.22 and  6.43 cm, respectively), while the least stem girth was  among four plants / stand (5.23 and 5.05 cm). Stem  girth was found to reduce with increasing plant  population per stand; a phenomenon that may  encourage easy lodging or stem breakage. 

Effect of increasing maize population per stand on  yield component and yield of three varieties of maize 

Analysis of data showed that variety investigated  significantly (p≤0.05) influenced days to first tassel,  days to 50% tassel, as well as grain yield per plant  (Table 5), but no significant effect (p≥0.05) of variety  was not observed on ear weight, ear length, kernels  per ear as well as 100-kernel weight. Significant  (p≤0.05) influence of population was observed on  days to 50% tassel, ear weight, ear length, kernel/ear,  100-kernal weight and grain yield per plant (Table 5).  Generally increasing plant population led to  processive delay in days to 50% heading, reduction in  ear weight, ear length, kernel/ear, 100-kernal weight  as well as grain yield per plant. There were significant  interactions between variety and population on days  to 50% tassel, ear weight, ear length, kernel / ear, 100- kernal weight and grain yield per plant (Table 5).  

Previous researchers have observed that interactions  between plant genotype and plant population can  affect maize parameters, especially grain yield, with  DeBruin et al. (2017) finding a positive relationship  between maize grain yields and plant population in  modern hybrids. 

Though explaining that modern hybrids possess the  ability to withstand greater stress attributable to high  population densities than older hybrids, which in turn  enables producers to establish higher plant  populations, leading to higher yields per unit area  (Russell, 1984; Duvick, 1997). 

The observation in this trial quite agreed with those  previous reports of positive response of yield  components and yield to varietal and population  influence (Russell, 1984; Duvick, 1997; DeBruin et al.  2017). Similarly, in line with the experimental  outcome, Abuzar et al (2011) reported that biomass  yield was significantly affected by different plant  population densities in a maize plot. They reported  that treatments having a population of 60000 and  80000 plants/ ha produced the maximum biomass  yield of 16890 kg/ha each, while the lowest biomass  yield (13330 kg/ha) was recorded with a population of  140,000 plants/ha. Several studies show that biomass  yield decreases progressively as the number of plants  increases in a given area because the production of  the individual plant is reduced (Hamidia et al. 2010). 

Similarly, they also observed that grain yield was  significantly affected by plant population densities.  Emam (2001) verified that kernels/ear and kernels/ear  row are the most important yield adjustment  components in response to plant population density  in maize; an observation which was quite in line with  this experimental outcome. The better response of  hybrids to population stress was evident in this trial  where the highest grain yield per plant was recorded  in Oba Super II (779.13g and 890.01g, respectively in  2021 and 2022 cropping seasons) while the least grain  yield per plant was in the local variety (530.80g and  475.00g, respectively in 2021 and 2022 cropping  seasons). Sowing seeds at one seed/hole gave the  highest grain yield/plant, 790.27g and 970.00g,  respectively in 2021 and 2022 cropping seasons. The  least grain yield/plant, 513.27g and 322.50g,  respectively in 2021 and 2022 cropping seasons were  observed when four seeds were sown/hole. 

The highest amount of grain yield/ha was obtained in  Oba super II (103,883.74kg and 118,667.70kg),  respectively in 2021 and 2022 cropping seasons, with  the local variety giving the lowest grain yield in both  seasons. While the lowest grain yield/plant was recorded in P4 (213,332 pop/ha), in the first year, the plot compensated for the yield reduction/plant with an increase in plant population cumulating in significantly greater harvest/ha (109,496.94 kg/ha), with  P1(53,333 plant/ha) recording significantly the lowest  grain yield/ha in both seasons. However, P4(213,332  pop/ha) did not repeat the same feat attained in the  first trial as it trailed behind P3 (160,000 pop/ha) and  P2 (106,666 pop/ha) in yield/ha (Table 6); an  indication that the population may not be able to  maintain stable yield. The most consist population  relative to yield/ha was P3 (160,000 pop/ha), thus  recommended for the experimental area, thus  maintaining a mean population of 133, 333 plants/ha  is predicted to give better performance for the  varieties. While Oba super II is recommended for the  experimental area. 

CONCLUSION 

It has been observed that stand density affects plant  architecture, alters growth and developmental  patterns and influences carbohydrate production.  High population increases interplant competition for  light, water and nutrients, which may be detrimental  to final yield because it stimulates apical dominance,  induces barrenness, and ultimately decreases the  number of ears produced per plant and kernels set per  ear, observed Sangoi (2000). Keeping this in view, the  present study was formulated to optimize the planting  density of maize under the Southern Guinea savannah  agro-ecological zone in Nigeria. 

The better response of hybrids to population stress  was evident in this trial where the highest grain yield  per plant was recorded in Oba Super II (779.13g and  890.01g, respectively in 2021 and 2022 cropping  seasons) while the least grain yield per plant was in  the local variety (530.80g and 475.00g, respectively in  2021 and 2022 cropping seasons). Sowing seeds at  one seed/hole gave the highest grain yield/plant,  790.27g and 970.00g, respectively in the 2021 and  2022 cropping seasons. The least grain yield/plant,  513.27g and 322.50g, respectively in 2021 and 2022  cropping seasons were observed when four seeds  were sown/hole. The highest amount of grain yield/ha  was obtained in Oba super II (103,883.74kg and  118,667.70kg), respectively in the 2021 and 2022  cropping seasons, with the local variety giving the  lowest grain yield in both seasons. While the lowest  grain yield/plant was recorded in P4 (213,332  pop/ha), in the first year, the plot compensated for  the yield reduction/plant with an increase in plant  population cumulating in significantly greater  harvest/ha (109,496.94 kg/ha), with P1 (53,333  plant/ha) recording significantly the lowest grain  yield/ha in both seasons. 

Table 5: Effect of increasing maize population per stand on yield component and yield of three varieties of maize (Zea mays) in 2021 and 2022 cropping seasons 

Treatment	Days to first  tassel		Days to 50%  tassel		Ear weight (g)		Ear length (cm)		Kernel / ear		100-kernel  weight (g)		GY / Plant (g)
	2021	2022	2021	2022	2021	2022	2021	2022	2021	2022	2021	2022	2021	2022
Variety
V1: Sammaz 52	56b	55c	62b	61b	99.23	124.00	12.52	13.52	249.93	301.58	26.17	27.98	621.03ab	782.50b
V2: Oba super-II	57a	58b	64a	64a	124.45	137.50	14.12	14.43	310.43	345.38	25.83	26.38	779.13a	890.01a
V3: Local Variety	57a	60a	65a	65a	103.34	83.03	13.50	12.93	287.78	244.40	23.67	22.97	530.80b	475.00c
LSD (0.05)	0.3	0.2	1.1	1.4	NS	NS	NS	NS	NS	NS	NS	NS	197.65	85.98
Population
P1: 53,333 pop/ha	57	57	64a	63b	145.30a	146.22a	14.87a	15.14a	337.66a	336.13a	28.67a	30.59a	790.27a	970.00a
P2: 106,666  pop/ha	56	58	62b	63b	120.20a	155.33a	14.19a	14.72a	313.92a	342.47a	25.56ab	24.63b	753.30b	840.00b
P3: 160,000  pop/ha	57	57	65a	63b	87.83b	106.33b	12.57b	13.09b	253.26b	298.21b	24.22b	25.88b	517.77c	623.34c
P4: 213,332  pop/ha	56	58	65a	65a	82.73b	72.33c	11.88b	11.44c	226.01b	211.67c	22.44b	22.00c	513.27c	322.50d
LSD (0.05)	NS	NS	1.4	1.7	30.310*	29.810*	1.480*	0.861*	41.810*	38.270*	3.300*	2.170*	27.250*	56.860*
Interactions
V1P1	57	54	62	60	123.30	185.00	13.61	15.84	295.50	373.60	28.00	34.00	777.60	1190.00
V1P2	55	55	59	60	122.30	130.00	14.04	14.39	283.20	337.80	27.30	24.00	766.60	850.00
V1P3	54	54	62	59	86.30	100.00	11.83	12.56	242.80	273.60	26.00	30.00	533.30	620.00
V1P4	56	56	63	63	65.00	81.00	10.59	11.31	178.30	221.30	23.30	23.90	406.60	470.01
V2P1	57	57	65	63	166.30	201.00	15.90	17.26	356.30	394.60	28.60	28.00	1046.60	1260.00
V2P2	54	60	60	63	137.30	144.00	14.83	14.77	331.30	353.90	26.60	27.90	863.30	930.00
V2P3	60	57	66	63	97.60	124.00	12.58	13.22	269.50	343.40	24.60	27.65	600.00	790.02
V2P4	56	59	64	66	96.60	91.00	13.14	12.46	284.50	289.60	23.30	22.00	606.60	580.00
V3P1	57	60	64	66	146.30	80.00	15.10	12.31	361.06	240.20	29.30	29.78	546.60	460.01
V3P2	59	60	66	66	101.00	112.10	13.68	15.36	327.40	335.70	22.60	22.00	630.00	740.00
V3P3	58	59	66	66	79.60	95.00	12.47	13.48	232.41	277.63	20.60	20.00	420.00	460.00
V3P4	55	59	62	66	86.60	45.00	12.73	10.56	230.16	124.10	22.00	20.10	526.60	240.00
LSD (0.05)	NS	NS	NS	NS	29.581*	19.610*	3.348*	2.091*	24.891*	33.457*	2.127*	4.671*	245.341*	123.119*
CV%	2.87	2.97	2.33	2.97	5.68	22.31	11.39	11.27	21.66	21.53	13.97	14.20	12.47	12.22

Means with the same letter(s) are not significantly different at 5% level of probability

Table 6: Effect of increasing maize population per stand on yield of three varieties of maize 

Treatment	2021 cropping season		2022 cropping season
	Grain yield/ Plant (g)	Grain yield /ha Kg/ha	Grain yield/ Plant  (g)	Grain yield /ha Kg/ha
Variety
V1: Sammaz 52	621.03	82,803.64	782.50	104,333.07
V2: Oba super-II	779.13	103,883.74	890.01	118,667.70
V3: Local Variety	530.80	70,773.16	475.00	63,333.18
Population
P1: 53,333 pop/ha	790.27	42,147.47	970.00	51,733.01
P2: 106,666  pop/ha	753.30	80,351.50	840.00	89,599.44
P3: 160,000  pop/ha	517.77	82,843.20	623.34	99,734.40
P4: 213,332  pop/ha	513.27	109,496.92	322.50	68,799.57

However, P4 (213,332 pop/ha) did not repeat the  same feat attained in the first trial as it trailed behind  P3 (160,000 pop/ha) and P2 (106,666 pop/ha) in  yield/ha; an indication that the population may not be  able to maintain stable yield. The most consist  population relative to yield/ha was P3 (160,000  pop/ha), thus recommended for the experimental  area. Maintaining mean population of 133, 333  plants/ha is predicted to give better performance for  the varieties. While Oba super II is recommended for  the experimental area; as it performed better than the  other varieties investigated. 

ACKNOWLEDGEMENTS 

We acknowledge the Department of Crop Production,  Kogi State University Anyigba, the Faculty of  Agriculture of the same institution, as well as the  University for providing the enabling environment to  conduct this research. 

REFERENCES 

Abuzar, M.R.; Sadozai, G.U.; Baloch, M.S.; Baloch, A.  A.; Shah, I.H.; Javaid T.; Hussain, N. Effect of  plant population densities on yield of maize. The  Journal of Animal and Plant Science, 2011, 21(4),  692-695. 

Assefa, Y.; Vara, P.V.; Prasad, P.; Carter, M.; Hinds, G.;  Bhalla, R.; Schon R, Jeschke, M.; Paszkiewicz, S.; Ciampitti, I.A. Yield response to planting density  for US modern corn hybrids: A synthesis analysis. Crop Science, 2016, 56, 2802– 2817. 

Ciampitti, A.; Vyn, T.J. Physiological perspectives of  changes over time in maize yield dependency on  nitrogen uptake and associated nitrogen  efficiencies: A review. Field Crops Research,  2012, 133: 48– 67.  

De Bruin, J.L.; Schussler, J.F.; Mo, H.; Cooper, M. Grain  yield and nitrogen accumulation in maize  hybrids released during 1934 to 2013 in the US  Midwest. Crop Sci., 2017, 57: 1431– 1446.  

Duncan, W.G. The relationship between corn density  and grain yield. Agronomy Journal,1958, 50, 82– 84.  

Duvick, D.N. What is Yield? In Developing drought and  low N-tolerant maize. Proceedings of  Symposium (Eds. G.O. Edmeades, B. Banzinger,  H.R. Mickelson and C.B. Pena-Valdivia). March  25-29, 1996, CIMMYT, El Batan, Mexico,  City,1997, 332– 335 pp. 

Erenstein, O.; Jaleta, M.; Sonder, K; Mottaleb, K;  Prasanna, B.M. Global maize production,  consumption and trade: trends and R&D  implications. Food Security, 2022, 14,1295– 1319  

FAO (Food and Agriculture Organization of the United  Nations). FAO Fertilizer and plant Nutrition  Bulletin: Guide to Laboratory Establishment for  Plant Nutrient Analysis. FAO, Rome, Italy., 2009,  203 pp. 

FAO (Food and Agriculture Organization of the United  Nations). FAOSTAT database. FAO, Rome., http://faostat3.fao.org, 2017. 

Haegele, J.W.; Becker, R.J.; Henninger, A.S.; Below,  F.E. Row arrangement, phosphorus fertility, and  hybrid contributions to managing increased plant population of maize. Agronomy Journal,  2014, 106, 1838– 1846.  

Hammer, G.L.; Dong, Z.; McLean, G.; Doherty, A.;  Messina, C.; Schussler, J.; Zinselmeier, C.;  Paskiewicz, S.; Cooper, M. Can changes in  canopy and/or root system architecture explain  historical maize yield trends in the US corn belt?  Crop Science, 2009, 49, 299-312 

Hay, R.K.M.; Walker, J.A. An Introduction to the  Physiology of Crop Yield. UK: Longman., 1989,  292 pp 

Hörbe, T.A.N.; Amado, T.J.C.; Ferreira, A.O.; Alba, P.J.  Optimization of corn plant population according  to management zones in southern Brazil. Precis.  Agric., 2013, 14, 450– 465.  

IPNI (International Plant Nutrient Institute) Canada.  Global Maize Project., 2018. http://anz.ipni.net/  Jamileh, S.; Moghadam, J.S. Response of some maize  hybrids to water Stress at pollination phase .  Biological Forum–An International Journal,  2015, 7(1), 1529-1536. 

Olaniyan, A.B. Maize: Panacea for hunger in Nigeria.  African Journal of Plant Science, 2014, 9(3), 156. Oloyede-Kamiyo, Q.O.; Olaniyan, A.B. Varietal  Response to Double Plant Population Density in  Maize: Implications for Breeding. The Journal of  Agricultural Sciences – Sri Lanka., 2020, 15(3),  387-394.  

Oyewole, C.I. Yield and economic implication of  intercropping millet and groundnut: Effects of  cropping pattern, P and K on growth and yield of  millet and groundnut in mixture in Sudan  savanna. LAP Lambert Academic Publishing,  Dudweiler Landstr. 99, 66123 Saarbrucken,  Deutschland, 2011, 108pp. 

Oyewole, C.I.; Maha, J.O,; Olushepe, O.A.; Tanko,  M.U.; Spacing effect on leaf area formation in  maize: 1. Correlation studies in growth,  development, yield components and yield  Journal of Global Agric. and Ecology, 2015a,  3(3), 137-143. 

Oyewole, C.I.; Olushepe, O.A.; Tanko, M.U.  Correlation studies in growth, yield components  and yield in maize (Zea mays) in Anyigba, Kogi  state, Nigeria. Journal of Global Agric. and  Ecology, 2015b, 2(2),47-51. 

Oyewole, C.I; Ajayi, O; Ojuekaiye, R.O. Evaluation of  seven upland rice (Oryzae sativa) cultivars by  three sowing methods in Anyigba, Kogi State,  Nigeria. African Journal of Agricultural Research,  2010, 5 (16), 2089-2096. 

Pretorius, J.P.; Human, J.J. The influence of time of  planting and planting density on the duration  

and rate of grain filling of maize (Zea mays L.).  (In Afrikaans, with English abstract). South Afr. J.  Plant Soil, 1987, 4, 61– 64. 

Qin X.; Feng, F.; Li, Y.; Xu, S.; Siddique, K.H.M.; Liao, Y.  Maize yield improvements in China: Past trends  and future directions. Plant Breed, 2016, 135,  166– 176.  

Russell, W.A. Agronomic performance of maize  cultivars representing different eras of  breeding. Maydica, 1984, 29, 375– 390. 

Saberali S.F. Influence of plant density and planting  pattern of corn on its growth and yield under  competition with common Lambesquarters  (Chenopodium album L.). Pajouhesh and  Sazandegi, 2007, 74, 143-152. 

Sangakkara, U.R.; Bandaranayake, P.S.R.D.; Gajanayake, J.N.; Stamp, P. Plant populations  and yield of rainfed maize grown in wet and dry  seasons of the tropics. Maydica., 2004, 49, 83- 88. 

Sangoi, L. Understanding plant population density  effects on maize growth and development: an  important issue to maximize grain yield. Ciência  Rural, Santa Maria, 2001, 31(1), 159-168. 

Sangoi, L.; Gracietti, M.A.; Rampazzo, C.; Bianchetti, P.  Response of Brazilian maize hybrids from  different eras to changes in plant population.  Field Crops Research, 2002, 79, 39– 51.  

Sharratt, B.S.; McWilliams, D.A. Microclimatic and  rooting characteristics of narrow-row versus  conventional-row corn. Agronomy Journal,  2005, 97, 1129– 1135. 

Statistical Analysis System (SAS). SAS Users Guide  Com. N.C. Statistical Analysis Institute, 1998,  256 pp. 

Tokatlidis, I.S.; Koutroubas, S.D. A review study of the  maize hybrids’ dependence on high plant  populations and its implications on crop yield  stability. Fields Crops Research, 2004, 88: 103– 114. 

Valadabadi, S.A.; Farahani, H.A. Effects of planting  density and pattern on physiological growth  indices in maize (Zea mays L.) under  nitrogenous fertilizer application. J. Agric. Ext.  and Rural Dev., 2010, 2(3), 40-47.