Agronomic Behavior of Peanut (Arachis hypogaea L.) Cultivars under Three Planting Densities in the Northeast of Peru

Abstract

Factors such as the selection of cultivars and the planted density affect the development and yield of peanuts (Arachis hypogaea L.). This study’s objective was to evaluate peanut cultivars’ agronomic behavior under three planting densities in the northeast of Peru. The design used was randomized complete blocks (DBCAs) with a bifactorial arrangement 4A × 3B (factor A, peanut cultivars; factor B, planting densities), forming 12 treatments with three replications per block. The results revealed that T3 (Huayabamba cultivar + density of 30 × 50 cm) stood out, presenting the most favorable means in the number of pods (16 pods), number of seeds per pod (five seeds), height at 90 days (22.7 cm), and yield (1850 kg/ha). Empty pods did not show significant differences between treatments. T8 (Chivita cultivar + density of 20 × 50 cm) indicated the highest number of branches (six branches); in the weight of 100 seeds, the Rojo Tarapoto cultivar was the most encouraging, adapting optimally to the three densities. In addition, T7 (chivita cultivar + density of 10 × 50 cm) showed the shortest days at flowering and harvest, with 64 and 134 days. The study showed that T3 was the most efficient in pod and seed production, making it crucial to optimizing peanut yield.

1. Introduction

The peanut (Arachis hypogaea L.) is an oilseed of great importance in the industrial and agricultural sectors worldwide [1]. It contains a high concentration of energy, with significant amounts of protein, vitamins, fiber, and minerals. They are consumed worldwide due to their accessibility and economic cost compared to other nuts [2]. Consumption of peanuts helps to reduce the risk of cardiovascular diseases, gallstones, and diabetes [2,3,4]. In addition, it prevents obesity by moderating postprandial appetite, suppressing hunger, and increasing satiety levels after ingestion [5,6]. In 2022, Asia accounted for 58.4% of the 54 million tons of world production; Mainland China accounts for more than 57% of Asia’s production, establishing itself as the main producing country with 18.2 million tons; South America, Argentina, Brazil, Bolivia, Paraguay, and Peru are positioned as the five countries with the highest production of shelled peanuts [7]. Peru obtained 5619 tons of production, while Ecuador, Colombia, and France were the main importers of shelled peanut kernels, generating 3407 thousand dollars of free on board value [8].

Groundnut yield is influenced by the genetic potential of the cultivar chosen and the agronomic management practices applied [9]. The proper selection of genotypes with adaptability, as well as pest and disease resistance, is an alternative to increase these yields [10]. However, groundnut production faces multiple challenges, which restrict the potential of its genotypes; water stress, nutrient insufficiency, temperature extremes, planting density, and biotic factors contribute to yield decline [11]. Planting density is a crucial agronomic element that plays a significant role in crop growth, development, and productivity [12]. When planting density is low, resources such as water, light, and nutrients are more accessible, resulting in less competition among plants; as planting density increases, competition for resources intensifies [13], and as a consequence, plant development, organic matter levels, percentage of organic carbon, available nitrogen (N), effective iron (Fe), and bulk density decrease [14].

Detailed analysis of the characteristics of pods produced by groundnut cultivars are essential to identify the potential of different genotypes; these data are crucial not only for germplasm development and evaluation, but also to determine the cultivars most adapted to the specific conditions of an area [15]. A better understanding of the differences between genotypes and how these are reflected in their yield potential is a valuable tool for selection processes, thus facilitating future yield improvement [16]. Proper cultivar selection, precise sowing timing, and length of the growing season are critical factors that significantly influence plant development, yield, and grain quality [17]. The amount of heat accumulated during the vegetative period has a relationship with the sowing density, turning it a factor that determines the growth phases of the plant and defines the total duration of the cycle [18]. On the other hand, prolonging the grain filling period can markedly increase crop yield by allowing the kernels to accumulate more nutrients and develop more efficiently; however, a longer growing cycle can reduce groundnut yield, because adverse environmental conditions increase pod loss [19,20].

Numerous studies have documented the effects of planting density on peanut growth and yield. Research in Poland and Ghana has shown that higher densities can improve plant height and pod and seed yield, while studies in Nigeria have indicated that high planting density can significantly increase yield by as much as 40% [21,22,23]. In addition, the selection of adaptable and resistant genotypes has been identified as a key strategy to maximize yield under different agronomic conditions [5,6]. However, most of this research has been conducted in different geographical and climatic contexts, using cultivars different from those found in northeastern Peru, a region with unique agroecological conditions that may influence the yield of peanut genotypes.

Despite advances in the understanding of factors influencing peanut yield, there is a significant gap in research related to local cultivars in northeastern Peru. This region presents particular environmental characteristics that could affect the interaction between planting density and local genotypes, which influence yield. To date, there has been no comprehensive analysis assessing how these variables interact in this specific context, underscoring the need for studies that address this issue. This study set out to fill this research gap, providing data that will not only optimize local cultivation practices, but also contribute up-to-date information on the behavior of yield parameters. The point of innovation of this research lies in its focus on local genotypes and the adaptation of planting densities to the specific conditions of the region, offering new perspectives on the adaptation and optimization of peanut cultivation in underexploited contexts. The objective of this research was to evaluate the agronomic yield of peanut (Arachis hypogaea L.) cultivars under three planting densities in northeastern Peru.

2. Materials and Methods

2.1. Area of Research

The present research work was carried out in the district of Longar, province of Rodríguez de Mendoza, department of Amazonas (Figure 1); the research area is located at an altitude of 1600 m.a.s.l. with the following coordinates: latitude south 6°23′8″ and longitude west 77°32′46″, with minimum and maximum temperatures of 9 and 26 °C.

2.2. Preparation of Genetic Material

Seeds were obtained from farmers in Longar district, which were collected in previous seasons in the same season. They were selected and dried to avoid the presence of fungi and other harmful organisms. These cultivars were selected for their resistance to Phytophthora infestans and for being relevant in the local market. In addition, they are short cycle (140–150 days to harvest) and are well adapted to altitudes of 1600 m.a.s.l., minimum and maximum temperatures ranging from 10 °C to 25 °C, average annual relative humidity of 79%, and average annual rainfall of 0.8 mm/day, which are the same characteristics of the area where the research was carried out. Each cultivar showed different percentages of gemination: Huayabamba (88.9%), Rojo Tarapoto (86.6%), Rojo Bola (79.2%), and Chivita (56.6%). The cultivars originate from Peru and have certain different morphological characteristics [24], as shown in

Table 1. Morphological characteristics of cultivars.

Cultivars	Name in the Catalog	Growth Characteristics	Pod Characteristics
Chivita	Criollo Blanco de Casma	Semirastrera	2–3 pale grains.
Rojo Tarapoto	Colorado Tarapoto	Semirastrera	Pods up to 4.30 cm, 3 grains, colored integument.
Huayabamba	Morado Huayabamba	Large Erecta	Pods large, up to 5 cm, 3 grains, dark purplish, almost black.
Rojo Bola	Rojo gigante	Erecta compact	Boxes rounded, without beak, 2 grains, colored tegument.

.

2.3. Soil Physicochemical Characteristics

An area of 154 m² (22 m × 7 m) with a total effective area of 47.52 m² was selected for the installation of the Arachis hypogaea L. crop; the physicochemical characteristics of the soil were determined 15 days before planting; soil subsamples were collected from 5 different points and extracted with a shovel at a depth of 30 cm following a zigzag path; the subsamples were homogenized until a 1 kg sample was obtained after using the quartering method [25]. It was then coded and analyzed according to the methodology of Bazan [26] at the Soil and Water Research Laboratory (LABISAG) accredited by the National Institute of Quality, Ministry of Production under NTP-ISO/IEC 17025: 2017 [27] of the National University Toribio Rodriguez de Mendoza of Amazonas.

The soil sample presented physicochemical characteristics, detailing both physical and chemical aspects. Physically, the textural class of the soil was sandy loam. As for the chemical components, the pH was 5.84 and the electrical conductivity was 0.2 dS/m. Organic matter constituted 4.33%, with a nitrogen content of 0.22% and carbon 2.51%. Phosphorus levels were 1.19 ppm and potassium 292.4 ppm. Cation exchange capacity indicated 25.6 meq/100g. In addition, potassium as a positive cation was 0.72 meq/100 g, bivalent calcium and magnesium were 19.99 meq/100 g and 2.15 meq/100 g, and sodium as a positive cation was 0.17 meq/100 g.

2.4. Installation of the Crop

The preparation of the land began with the elimination of weeds; then, the soil was ploughed to a depth of approximately 25 cm, and a harrow pass was made and with a raffia, wherein the demonstrative plots were traced. Once the seeds of the peanut cultivars were obtained, they were separated into containers according to each cultivar, and a systemic fungicide (Emesto Prime, Bayer, México, México) was applied to each of them, with a dose of 0.06 L per 100 kg of seed—based on the product’s technical data sheet.

The sowing was carried out on 16 October 2020 after the adequate preparation of the land and the respective layouts of the demonstration plots; the seeds of the peanut cultivars were sown based on the densities described in the treatments (

Table 2. Classification of treatments in relation to the 4A × 3B factorial arrangement (factor A, peanut cultivars; factor B, planting densities).

Treatments	Peanut Cultivars (Arachis hypogaea L.)	Density
T1	Huayabamba	10 × 50 cm
T2	Huayabamba	20 × 50 cm
T3	Huayabamba	30 × 50 cm
T4	Rojo Tarapoto	10 × 50 cm
T5	Rojo Tarapoto	20 × 50 cm
T6	Rojo Tarapoto	30 × 50 cm
T7	Chivita	10 × 50 cm
T8	Chivita	20 × 50 cm
T9	Chivita	30 × 50 cm
T10	Rojo Bola	10 × 50 cm
T11	Rojo Bola	20 × 50 cm
T12	Rojo Bola	30 × 50 cm

) for which holes were made, and one seed was placed per stroke (per hole). Then, the holes were covered with soil from the same field in order to prevent the seeds from being extracted by birds or rodents.

2.5. Cultivation Work

Fertilization was via foliar [28] and was done only once throughout crop development to ensure that plants have only the basic nutrients to develop uniformly, controlling the fertilization variable to avoid interference from the effects on planting densities and cultivars; this ensures that any observed differences in crop yields can be attributed primarily to the interaction of planting density factors and cultivars. Fertilization was carried out 60 days after planting with a foliar fertilizer (Multi-Frut, FARMAGRO S.A., Lima, Perú.) composed mainly of phosphorus (P) and potassium (K). A dose of 100 cc in 20 L of water was applied with the help of a manual knapsack.

Irrigation was managed under a dryland system, i.e., it only received water from rainfall due to the constant rainfall and the type of soil favorable for the development of this crop.

For phytosanitary control, a contact fungicide (Dithane NT, Corteva Agriscience Argentina S. R. L., Buenos Aires, Argentina.) was applied at 30 g in 20 L of water using a manual knapsack to combat leaf spots (Phytophthora infestans). Weed control was also carried out continuously throughout the crop cycle.

2.6. Variables Evaluated

For the evaluation of each variable, 6 plants were taken at random from each experimental unit. Plant height was measured from the base of the plant to the apex, expressed in (cm) at 60 and 90 days after planting. The number of branches per plant was evaluated 90 days after planting. In addition, the number of pods, seeds per plant, and the number of empty pods were counted. For the phenological calendar, the days elapsed from sowing to 50% flowering were recorded, and for harvesting, plants were evaluated when they showed a brown color. Also, 100 seeds per treatment were weighed in grams to determine their weight. Finally, the yield per hectare was estimated from the total weight of pods per treatment.

2.7. Description of Treatments

The treatments were composed of the interaction of the combination of peanut cultivars and planting densities under field conditions, as shown in Table 2.

2.8. Experimental Design

The design used was a randomized complete block design (RCBD) with a 4A × 3B bifactorial arrangement (factor A, peanut cultivars; factor B, planting densities). It formed 12 plots with three replications per block, giving a total of 36 experimental units. Each experimental unit was 1.32 m² (1.10 m × 1.20 m), and the distances between units were 70 cm.

2.9. Data Analysis

The data obtained for the variables evaluated were subjected to a normality test (Shapiro–Wilks) and homogeneity of variances (Bartlett). Data that presented a normal distribution and homogeneity were subjected to a 2-way ANOVA and Duncan’s multiple comparison test (p ≤ 0.05). On the contrary, data that did not present a normal distribution were worked with the Kruskal–Wallis nonparametric test. The data were analyzed with the R statistical program version 4.3.2 for Windows.

3. Results

3.1. Height of Plant and Phenological Calendar

The results showed that there were no significant differences at the level of planting densities (10 × 50 cm, 20 × 50 cm, 30 × 50 cm) in any of the parameters measured. However, there were notable differences at the cultivar level. The Huayabamba cultivar stood out with the highest values in all evaluations for plant height at 60 (15.94 cm) and 90 days (21.76 cm), with the longest days to until flowering (91 days) and harvest (182 days), while the lowest values were obtained for the Chivita cultivar, with plant height at 60 and 90 days of 13.31 and 14.07 cm, and days to until flowering and harvest of 65 and 133 days, being the earliest of all cultivars. At the treatment level, for plant height at 60 and 90 days after planting, differences were observed between treatments, where the least favorable height was observed in the interaction of the Chavita cultivar with the three planting densities (T7, T8, and T9). In the evaluation of the phenological calendar, the longest days to flowering and harvest were presented by the cultivar Huayabamba in the three planting densities (T1, T2, and T3); however, the shortest days were presented by the cultivar Chavita (T7, T8, and T9) (

Table 3. Effects of densities and cultivars on growth and development variables. (mean ± standard deviation).

Factors	Plant Height after 60 Days (cm) 1	Plant Height after 90 Days (cm) 1	Days to Flowering 1	Days to Harvest 2
Densities
10 × 50 cm	15.2 ± 1.5 ns	19.6 ± 3.5 ns	77.5 ± 11.4 ns	159.0 ± 18.5 ns
20 × 50 cm	15.4 ± 1.3 ns	19.1 ± 3.8 ns	78.1 ± 9.9 ns	159.8 ± 19.1 ns
30 × 50 cm	14.6 ± 2.2 ns	19.2 ± 4.5 ns	78.7 ± 10.3 ns	159.4 ± 19.1 ns
Cultivars
Huayabamba	15.9 ± 1.2 a	21.7 ± 2.5 a	91.2 ± 1.3 a	182.2 ± 1.0 a
Rojo Tarapoto	15.5 ± 0.8 a	19.7 ± 2.3 a	83.8 ± 2.2 b	168.7 ± 0.8 b
Chivita	13.3 ± 2.0 b	14.0 ± 2.5 b	65.4 ± 1.9 d	133.6 ± 1.1 d
Rojo Bola	15.6 ± 1.3 a	21.7 ± 1.9 a	72.1 ± 1.5 c	153.1 ± 1.1 c
Treatments
T1	15.9 ± 0.4 a	21.5 ± 1.7 a	92.3 ± 0.5 a	181.0 ± 0.0 b
T2	16.1 ± 0.6 a	21.1 ± 3.1 a	90.3 ± 0.5 a	183.0 ± 1.0 a
T3	15.8 ± 2.2 a	22.7 ± 3.3 a	91.0 ± 2.0 a	182.6 ± 0.5 ab
T4	15.6 ± 0.7 a	20.2 ± 0.5 a	83.0 ± 1.7 b	168.6 ± 1.1 c
T5	15.1 ± 0.4 a	20.1 ± 2.9 a	83.6 ± 3.0 b	169.0 ± 1.0 c
T6	15.9 ± 1.3 a	18.9 ± 3.2 ab	85.0 ± 2.0 b	168.6 ± 0.5 c
T7	13.8 ± 1.7 ab	14.4 ± 2.3 bc	64.0 ± 1.0 d	133.6 ± 0.5 e
T8	14.2 ± 2.2 ab	14.6 ± 3.8 bc	66.3 ± 2.8 d	133.6 ± 1.5 e
T9	11.9 ± 2.1 b	13.2 ± 1.9 c	66.0 ± 1.0 d	133.6 ± 1.5 e
T10	15.7 ± 2.1 a	22.3 ± 2.0 a	71.0 ± 1.0 c	153.0 ± 1.0 d
T11	16.3 ± 0.4 a	20.8 ± 2.5 a	72.3 ± 1.1 c	153.6 ± 1.5 d
T12	14.8 ± 0.4 a	22.1 ± 1.5 a	73.0 ± 2.0 c	152.6 ± 1.1 d

¹ Variables with a normal distribution and different letters in the vertical direction indicate significant differences at the 5% level according to the Duncan test. ² Nonparametric variables; letters in the vertical direction indicate significant differences at the 5% level according to the Kruskal–Wallis test. ns = not significant.

).

3.2. Yield Variables

As shown in

Table 4. Effect of sowing densities and cultivars on yield variables.

Factors	Number of Branches 2	Number of Pods 1	Number of Seeds/Pod 1	Empty Pods 2	Weight 100 Seeds (g) 2
Densities
10 × 50 cm	4.7 ± 0.5 ns	5.1 ± 1.8 c	4.1 ± 1.1 ns	0.7 ± 0.2 ns	100.0 ± 22.9 ns
20 × 50 cm	5.0 ± 0.8 ns	8.6 ± 1.7 b	4.2 ± 1.2 ns	0.5 ± 0.3 ns	99.0 ± 21.3 ns
30 × 50 cm	4.7 ± 0.8 ns	12.6 ± 2.5 a	4.1 ± 1.1 ns	0.5 ± 0.3 ns	98.4 ± 22.3 ns
Cultivars
Huayabamba	5.1 ± 0.3 a	11.5 ± 3.8 a	5.3 ± 0.7 a	0.7 ± 0.3 ns	101.1 ± 1.4 c
Rojo Tarapoto	4.5 ± 0.4 b	9.3 ± 3.2 b	4.6 ± 0.3 b	0.7 ± 0.2 ns	119.2 ± 0.7 a
Chivita	5.4 ± 0.8 a	6.5 ± 2.9 d	2.7 ± 0.6 d	0.5 ± 0.2 ns	64.2 ± 1.7 d
Rojo Bola	4.1 ± 0.3 c	8.0 ± 3.2 c	3.9 ± 0.7 c	0.4 ± 0.3 ns	112.1 ± 3.2 b
Treatments
T1	5.1 ± 0.1 abc	7.4 ± 0.1 e	5.4 ± 0.1 a	0.7 ± 0.0 ns	102.6 ± 0.6 ef
T2	4.9 ± 0.2 abcd	11.0 ± 0.7 c	5.2 ± 0.8 ab	0.7 ± 0.4 ns	100.3 ± 1.4 f
T3	5.4 ± 0.3 ab	16.0 ± 0.4 a	5.2 ± 1.0 ab	0.6 ± 0.5 ns	100.3 ± 0.4 f
T4	4.5 ± 0.2 cde	5.8 ± 0.8 f	4.6 ± 0.1 abc	1.0 ± 0.0 ns	119.8 ± 0.3 a
T5	4.8 ± 0.5 bcd	8.8 ± 0.6 d	4.9 ± 0.3 abc	0.5 ± 0.2 ns	119.2 ± 0.5 ab
T6	4.3 ± 0.0 de	13.1 ± 0.4 b	4.3 ± 0.2 abc	0.6 ± 0.1 ns	118.6 ± 0.6 bc
T7	5.0 ± 0.6 abcd	2.9 ± 0.6 h	2.6 ± 0.2 e	0.6 ± 0.1 ns	63.7 ± 1.1 g
T8	6.1 ± 0.2 a	7.1 ± 0.4 e	2.8 ± 0.7 de	0.5 ± 0.2 ns	65.6 ± 2.1 g
T9	5.2 ± 1.0 abcd	9.6 ± 0.2 d	2.7 ± 0.8 de	0.5 ± 0.2 ns	63.2 ± 1.1 g
T10	4.3 ± 0.5 de	4.5 ± 0.2 g	3.7 ± 0.6 cde	0.5 ± 0.3 ns	113.9 ± 5.4 bcd
T11	4.1 ± 0.2 e	7.7 ± 0.8 e	3.9 ± 0.7 cd	0.4 ± 0.3 ns	110.7 ± 1.1 de
T12	4.0 ± 0.3 e	11.8 ± 0.4 c	4.1 ± 0.8 bc	0.5 ± 0.3 ns	111.6 ± 1.1 cd

¹ Variables with a normal distribution and different letters in the vertical direction indicate significant differences at the 5% leve, according to the Duncan test. ² Nonparametric variables: letters in the vertical direction indicate significant differences at the 5% level according to the Kruskal–Wallis test. ns = not significant.

, at the density level, there were no significant differences for the variables number of branches, number of seeds/pods, empty pods, and weight of 100 seeds; but in the number of pods, the planting density of 30 × 50 cm reached the highest values with 12.68 pods, being statistically different from the densities of 10 × 50 cm and 20 × 50 cm.

At the cultivar level, there were no significant differences in the variable of empty pods; but for the variables of number of branches, number of seeds/pods, weight of 100 seeds, and number of pods, the Huayabamba cultivar had a significant influence and obtained the best values in the evaluations.

At the treatment level, the Huayabamba cultivar with the three planting densities (T1, T2, and T3) showed the highest number of branches, but it did not differ statistically from the treatments of the Chivita cultivar with the densities 20 × 50 cm and 30 × 50 cm (T8 and T9) upon comparing the best averages: T8 was superior to T3 by 11.48% in the number of branches. On the contrary, T3 (cultivar Huayabamba + 30 × 50 cm density) presented a favorable average regarding the number of pods (16 pods) compared to the other treatments. The highest average in terms of the number of seeds per pod (five pods) was revealed in the Huayabamba cultivar in the three planting densities (T1, T2, and T3); all these treatments, however, were not statistically different from the Rojo Tarapoto cultivar in the three planting densities (T4, T5, and T6). In addition, there were no significant differences in the number of empty pods. The most promising 100-seed weight was shown by the cultivar Rojo Tarapoto subjected to three levels of densities represented by T4, T5, and T6, with 119.8, 119.2, and 118.6 g.

Table 5. Effect of planting density and cultivar on peanut yield.

Factors	Yield (Kg/ha) 2
Densities
10 × 50 cm	752.8 ± 184.6 c
20 × 50 cm	1150.7 ± 123.1 b
30 × 50 cm	1583.3 ± 231.7 a
Cultivars
Huayabamba	1408.0 ± 350.2 ns
Rojo Tarapoto	1192.1 ± 455.0 ns
Chivita	961.5 ± 284.1 ns
Rojo Bola	1087.5 ± 358.0 ns
Treatments
T1	1057.0 ± 6.0 gh
T2	1317.0 ± 8.0 cd
T3	1850.0 ± 12.4 a
T4	671.3 ± 3.2 ij
T5	1183.0 ± 7.0 ef
T6	1722.0 ± 6.2 ab
T7	620.0 ± 5.2 k
T8	992.0 ± 5.2 hi
T9	1272.6 ± 35.2 de
T10	663.0 ± 7.0 jk
T11	1111.0 ± 2.6 fg
T12	1488.6 ± 8.1 bc

² Nonparametric variables: letters in the vertical direction indicate significant differences at the 5% level according to the Kruskal–Wallis test. ns = not significant.

shows that density levels had a significant effect, where the planting density of 30 × 50 was the most favorable in relation to the yield variable. Th cultivars levels did not have a significant influence on peanut yields.

In relation to the treatments, the yield variable’s most favorable mean was acquired of T3 (Huayabamba cultivar + density of 30 × 50 cm) with 1850 kg/ha. The lowest yield values were reached with T7 (Chivita cultivar + density of 10 × 50 cm) with 620 kg/ha.

4. Discussion

Our research revealed significant variations in the evaluated variables over time, providing valuable insights into yield responses in relation to planting density and cultivars under specific regional conditions. These findings will lay a solid foundation for future research. The Huayabamba cultivar, planted at low density (30 × 50 cm), showed superior performance in most of the analyzed variables, suggesting that the optimal response of some cultivars could be influenced by their drought resistance, as each responds uniquely to water stress by activating specific adaptation mechanisms [29].

Although this study did not focus on water stress, as a rainfed irrigation system was used, our findings may guide future research. A cultivar with outstanding genetic characteristics notably impacts its growth and development, which are reflected in greater plant height, which facilitates agricultural tasks such as harvesting and increases productive capacity [30,31]. For example, Iddrisu et al. [32] obtained favorable results with a 30 × 15 cm density, reaching maximum heights of 21.1 cm at 56 days with the Yenyawoso cultivar. Similarly, Nwokwu et al. [33] reported that higher planting density increases the height of peanut plants, regardless of the variety. In contrast, our results indicate that planting density did not significantly affect plant height, although the Chivita cultivar showed the shortest height at 90 days under different planting densities (T7, T8, and T9).

A reduction in days to flowering and harvest was observed with high planting density (10 × 50 cm) in combination with the Chivita cultivar. Previous studies have shown that optimal planting density can shorten the phenological cycle, although this depends on the cultivar and its genetic characteristics [34]. Days to flowering can vary among genotypes, which are affected by factors such as water availability and temperature, with the most adaptable genotypes responding better under adverse conditions [35]. Early-maturing cultivars under short photoperiods tend to flower more quickly [36,37,38,39]. Days to harvest also vary depending on the planting date, with possible delays of up to 21 days, which are influenced by the genetic characteristics of the cultivar and its productive potential [40]. These findings are relevant for optimizing agricultural practices in regions with similar conditions, suggesting that the combination of high planting density with specific genotypes such as Chivita may be recommended to accelerate the crop cycle.

At the treatment level, our results underscore the importance of the interaction between planting density and cultivar to optimize yield and other agronomic variables. In particular, the Huayabamba cultivar showed superior yield at low density (30 × 50 cm, T3), suggesting efficient capture and use of sunlight and contributing to higher yields [41]. Studies indicate that the number of branches is linked to planting density, where high density can reduce the number and diameter of branches and the number of nodes through results obtained under gravity irrigation [42,43]. In our study, using rainfed irrigation, we observed that low planting density produced more branches, especially in T3, while T10 (red ball + 10 × 50 cm) with high density showed fewer branches and lower yield. Dapaah et al. [44] noted that greater branch development can favor production by increasing the plant’s photosynthetic capacity, although this also depends on the cultivar and environmental conditions [45,46]. Other studies have shown that low planting density increases the number of branches, reaching approximately 10.25 per plant [33,47]. In our case, planting density did not significantly influence the number of branches, but it did affect the number of pods, with 30 × 50 cm density standing out and the Huayabamba cultivar showing the best results in these variables.

The number of pods and seeds per pod in treatment T3 was notably higher. Yousif and Hussain [48] found that variations in the number of pods per plant in different peanut cultivars were mainly due to their genetic inheritance. In contrast, Chen et al. [49] determined that low density positively influences the number of pods, although the number of seeds and yield showed an inversely proportional relationship. However, in our study, the number of seeds per pod and yield showed a directly proportional relationship.

In studies by Al-Shammari and Jaburi [50], evaluating fava bean (Vicia faba L.) cultivars under foliar fertilization with Zinc at low planting density, a greater number of pods and seeds per pod was observed, while plants grown at high density were superior in height and total yield. These findings align with ours, where the interaction between the Huayabamba cultivar and low planting density (T3) showed a direct relationship with the number of pods and seeds per pod without decreases in these variables. Similar research in semi-arid tropical areas with dry seasons, using a 30 × 10 cm density, also reported good results in the number of pods and yield [51,52]. In subtropical Australia, two peanut cultivars planted at different planting densities under irrigation from stored soil water showed an increase in the number of pods per m² with low density (40,000 plants/ha) [53]. In our study, planting density (30 × 50 cm) and the Huayabamba cultivar influenced the number of pods, while yield was more related to planting density. An advantage of low density is the reduction of abiotic stress, thus improving yield, so combining low planting density with an appropriate planting date is recommended to optimize results [54].

While high planting density can increase yields, this may decrease the number of pods, weight of 100 pods, and weight of 100 seeds [55]. In research conducted in Syria, it was observed that low planting density increased the weight of 100 seeds and the number of seeds per plant in two Arachis hypogaea cultivars [56]. In the Cañete Valley, Peru, the Tarapoto cultivar showed the best yields with 2,516 kg/ha at a density of 30 × 85 cm, while the cultivars Colec I-95/50 (98.72 g) and Boliviano (86.55 g) stood out in the weight of 100 seeds [57]. According to our results, the weight of 100 seeds was not significantly influenced by densities, but the 30 × 50 cm density affected yield. The Huayabamba cultivar notably influenced the weight of 100 seeds and the number of pods. In terms of yield, the Huayabamba cultivar, planted at low density (30 × 50 cm), obtained the best results despite not achieving the highest weight of 100 seeds; other yield variables were not affected by this planting density. Additionally, the agronomic behavior of the plant can be modified with adequate temperatures; high planting density may decrease yields due to increased abiotic stress caused by the absorption of photosynthetically active radiation (PAR) [36,39].

5. Conclusions

The results revealed that planting densities and peanut cultivars had a significant impact; a low density (30 × 50 cm) with the Huayabamba cultivar presented higher averages in most of the variables evaluated compared to the other treatments. The cultivar Chivita with a medium density (20 × 50 cm) registered the highest number of branches; in the weight of 100 seeds, the cultivar Rojo Tarapoto was the most promising, adapting optimally to the three density levels, where its high density (10 × 50 cm) sowing showed shorter days to flowering and harvest. Each cultivar’s genetic potential influenced these results regarding resistance to different stresses.

These findings suggest that cultivar selection and planting density are key strategies for optimizing groundnut crop yield. However, more comprehensive studies in different seasons and locations are needed to validate and extend these initial results. The implementation of these practices could improve the efficiency and economic sustainability of peanut cultivation, increasing competitiveness in various markets and benefiting producers.