Sustainability of the Local Maize (Zea mays L.) Varieties and Populations Cultivation

Abstract

Within the project “Small-scale grants for biodiversity actors in South-East Europe 2023–2025”, whose main mission is the collection of local varieties and populations, a fundamental question arises: “Why are ‘ancestral’ maize varieties and populations still cultivated?” To answer this question, we conducted a comprehensive set of investigations on 14 maize (Zea mays L.) varieties and populations and on one hybrid, collected from the historical regions of Romania—Transylvania, Moldova, Oltenia and Muntenia. The studies combine quantitative, qualitative and computational methods and focused on energy consumption associated with maize cultivation; maize grain production and related agronomic characteristics; the content of energy macronutrients (protein, fat, starch) and energy elements (CHNS-O, ash, moisture); and nutritional and thermal energy values (upper and lower) of whole cornmeal. The sustainability of the cultivation of local maize varieties was also evaluated based on the energy balance and the energy efficiency ratio. The results demonstrated that the cultivation of “ancestral” maize varieties and populations is sustainable, because the amount of energy obtained, expressed in kJ ha⁻¹, as nutritional energy (24,740,195.04–90,287,743.07), higher heating energy (55,162,983.798–193,374,572.55) and lower heating energy (32,329,465.37–113,906,753.63), is greater than the amount of energy consumed for the establishment and maintenance of these crops (1,742,798.75–19,524,555.05).

1. Introduction

Maize (Zea mays L.) was introduced into culture and is still cultivated all over the world, almost exclusively for the nutritional value of its grains, the white whole grain cornmeal having an energy value within the range of 14,784–15,420 kJ/kg [1]. The cultivation of local (traditional) maize (Zea mays L.) varieties and populations represents a major challenge in the context of rural depopulation, economic globalization, and the pressure exerted by seed companies promoting modern varieties and hybrids to small-scale farming households. This situation is further exacerbated by the insufficient material and moral support needed for the maintenance and conservation of local maize genetic resources. The following initiatives are exceptions: the project “Small-scale grants for biodiversity actors in South-Eastern Europe 2023–2025” [2]; the IFOAM–Organics International and IFOAM–Organics Europe webinar of 23 April 2025 “Protecting Seeds, Preserving the Future” [3] and “Our Seeds, Our Future: Protecting Biodiversity and Farmers’ Rights” [4]; the International Seed Federation’s call to action “Seeds for a Resilient Future” [5]; the broader concept “Seeds and Plant Genetic Resources: A Basis for Life”, explored by FAO [6], etc. Additionally, gene banks, together with numerous international organizations and several Romanian NGOs, play a key role in the collection and conservation of local (traditional) varieties and populations of field crops, vegetables, aromatic and medicinal plants, as well as fruit tree species, etc. For the moment, research on local maize varieties focuses on investigating their essential traits for climate adaptation through the analysis of phenotypic characteristics and genetic background, with the aim of developing new directions in maize breeding and strengthening food security. Within the project “Small-scale grants for biodiversity actors in South-Eastern Europe 2023–2025,” a fundamental question was raised: “Why are the local ‘ancestral’ maize varieties and populations still cultivated?” or, in other words, “What is the level of sustainability of cultivating these varieties?” Modern agricultural systems are highly dependent on industrial energy inputs, as socio-economic development continues to promote the adoption of more energy-intensive production technologies [7]. Measuring energy flows in production systems is essential for assessing energy consumption and improving efficiency, thereby contributing to economically profitable outputs with reduced environmental impact. Energy use efficiency reflects the balance between energy inputs and outputs within an agroecosystem [8].

In this context, local maize varieties and populations, being better adapted to pedoclimatic conditions, generally require fewer inputs and are associated with lower energy consumption and higher sustainability [8].

Monocropping systems, which predominate in major grain-producing regions of China, contribute to resource reduction and environmental degradation, while intercropping represents an alternative with the potential to improve resource use efficiency [9]. Also, in their study, the same authors reported that maize monocropping systems can exhibit higher energy-based sustainability than maize–soybean intercropping, with the energy yield ratio and energy sustainability index being 13.7% and 21.1% higher, respectively, while the environmental loading ratio was 7.3% lower compared to intercropping systems. Romaneckas et al. [10] suggest that multicropping systems can contribute to addressing issues related to energy consumption. Vicia faba L. is widely used as an intercrop with maize (Zea mays L.) [11,12]. Previous studies have shown that maize–faba bean intercropping systems can enhance crop yield [13], improve land-use efficiency [14], increase soil fertility [15,16], and reduce weed and pest pressure [17].

Multicropping systems represent a sustainable practice used by smallholder farmers in Rwanda too, contributing to the development of resilient agroecosystems and providing socio-economic and ecological advantages over monocropping, particularly under drought conditions [18].

The sustainability of cultivating local maize (Zea mays L.) varieties and populations in Romania has not been sufficiently investigated to date, particularly due to the lack of integrated studies associated with energy consumption, and the energy value of production. In this context, considering the importance of sustainable agricultural practices and the need to optimize resource use, the aim of this study was to evaluate the sustainability of cultivating local maize varieties and populations by analyzing grain production and agronomic characteristics, technological energy consumption, and the complete energy value of whole cornmeal—from both nutritional and caloric perspectives. In addition, the energy balance and energy efficiency rate were determined. The caloric energy values are particularly relevant for the use of maize grains that are unsuitable for human or animal consumption, or as a fuel source in thermal power plants. Furthermore, the concept of sustainability is examined in relation to cropping systems and the dynamics of energy production and consumption throughout their entire life cycle (Ion Toncea, personal communication, 25 August 2024).

2. Materials and Methods

In this chapter, the materials and methods used in the study are briefly described as follows:

2.1. Biological Materials

The study involved 15 air-dried cob samples collected from 9 maize (Zea mays L.) genotypes cultivated in 2024, including 8 traditional varieties (populations) and one hybrid. The genotypes differed in the number of kernel rows per cob (8R, 12R, 14R, and 16R) and cultivation systems: intercropping and corn only (monocropping).

The experimental plots were located across four Romanian development regions which differ in environmental and pedoclimatic condition, like South-Muntenia, South-West Oltenia, North-East, and North-West). The plant material included local maize varieties and populations differing in kernel row number (8, 12, 14 and 16 rows per cob) and kernel/cob coloration (with orange cob and red seed or some of them with white or red cobs and yellow seed), as well as one commercial hybrid.

Cultivation technologies were mainly traditional, such as intercropping systems and, in some cases, professional organic (ecological) systems, corn only (Mălai sticlos de Bărăi 12R, Optaș de Bărăi 8R and Porumb Moldovenesc 12R) and a conventional one (Fundulea 423 16R).

2.2. Quantitative Methods

Systematic observations and measurements were performed on the maize cobs and their grains in order to characterize the phenotypic performance of the studied genotypes. Data regarding cultivation practices applied to the studied maize (Zea mays L.) genotypes were collected through interviews with farmers. For each genotype, a detailed technological sheet was developed, incorporating all production inputs. These included energy carriers (diesel fuel, gasoline, and electricity), organic and mineral fertilizers, herbicides, pesticides, and seeds. Based on these records, the energy equivalents of all technological inputs were calculated (

Table 1. Energy equivalents of human labour, animal traction and various materials [19].

Inputs Name	Physical Unit of Measurement	Energy Equivalent (kJ)	Inputs Name	Physical Unit of Measurement	Energy Equivalent (kJ)
Human labour	Man-day (8 h)	12,558	Chemical fertilizers: (N)	kg	92,519
Animal power	Animal-day (8 h)	125,580	Chemical fertilizers: (P2O5)	kg	20,340
Electric energy	kWh	3600	Organic fertilizers	kg	682
Diesel fuel	L	35,581	Pesticides, Herbicides	kg, L	418,600
Gasoline	L	32,965	Seeds	kg	19,080

), enabling a comprehensive assessment of energy consumption associated with each genotype.

Maize grains were milled using a SWANTECH sample mill (model SJ500) at a coarse grinding setting of 5.5, to ensure uniform particle size for subsequent analyses.

Monitoring and control of the grain moth (Sitotroga cerealella) were performed using sex pheromone-baited sticky traps, allowing for systematic detection and population surveillance under storage conditions.

2.3. Qualitative Methods

The following determinations were performed on whole cornmeal samples:

-

The macronutrient content (protein, fat, starch, ash, and moisture, expressed as percentages) was analyzed using an INSTALAB 660 instrument, a DICKEY-John NIR (Near-Infrared Reflectance) device.

-

The elemental composition of carbon, hydrogen, nitrogen, and sulphur (CHNS) was determined with a COSTECH 4010 analyzer. Additionally, proximate analyses were conducted to determine ash content (A) by oven incineration at 600 °C and moisture content (W) by drying at 105 °C.

2.4. Computational Methods

The energy consumption (human labour, animal traction, and various materials) for the cultivation of the studied maize (Zea mays L.) genotypes was calculated in kJ/plot (1), kJ ha⁻¹ (2), kJ/kg DM (3), based on the quantities of inputs used and their corresponding energy equivalents [19] (Table 1 and

Table 2. Productivity indicators of local maize (Zea mays L.) varieties and populations cultivated in 2024.

Name of the Maize (Zea mays L.) Local Varieties and Populations		Plots Location	Farming System	Plots Area (m2)	Cobs Prod. (kg/plot)	Grains Yield of Cobs (%)	Grains Yield (DM) (kg ha–1)	Thousand Grains Weight (TGW-Grams)
Mălai sticlos de Bărăi 12R (corn only), organic		Barai 4/ Caianu, Cluj county	Organic farming	5600	6001	73.03	6816	351.40
Optaș de Bărăi 8R (corn only), organic				1000	450	69.49	2730	400.86
Lăpușneac 8R, orange seeds, white cob (intercropping)		Corusu/ Baciu, Cluj county	Household farming	200	54.70	83.36	3503	521.09
Lăpușneac 8R, red seeds, white cob (intercropping)					31.39	79.76	2188	310.74
De Maramureș 12R (intercropping)		Ungureni 100/ Cupseni Maramures county	Mixed farming (traditional + conventional)	500	250.91	69.54	6065	344.79
De Maramureș 14R (intercropping)					249.92	79.54	7021	288.54
De Maramureș 12R (corn only)			Mixed farming (conventional + traditional)	3000	1073.36	81.88	5156	247.36
De Maramureș 14R (corn only)					1445.75	73.79	6280	297.85
Florian 12R (intercropping)		Preluca Noua 63/Copalnic Manastur, Maramures county	Traditional farming	450	148.49	34.60	1998	299.45
Florian 16R (intercropping)					257.49	27.93	2736	205.39
Mesteceni 12R and 14R (intercropping)		Preluca Noua 113/Copalnic Manastur, Maramures county	Traditional farming	2000	1500.12	49.70	3232	197.66
Porumb Moldovenesc 12R (intercropping), organic		Negritesti 27/ Podoleni, Neamt county	Organic farming	2100	699.88	81.19	2392	328.98
Bob tare 14R, white cob (intercropping)		Surpati/ Runcu, Valcea county	Traditional farming	1000	138.95	83.31	2015	333.10
Bob tare 14R, red cob (intercropping)					178.08	70.21	2198	330.33
Fundulea 423, 16R (corn only)		Fundulea/N. Titulescu 1, Calarași county	Conventional farming	246.4	58.84	85.35	2032	411.07
Mean				1609.64	1031.49	69.51	3757.46	324.57
SD				1680.40	2195.60	17.92	1926.46	81.18
CV (%)				104.40	212.86	25.79	51.27	25.01

).

$$\begin{array}{l}\mathrm{Energy}\mathrm{consumption}\left({\displaystyle \frac{\mathrm{k}\mathrm{J}}{\mathrm{p}\mathrm{l}\mathrm{o}\mathrm{t}}}\right)=\\ =\mathrm{Human}\mathrm{labour}\left(\mathrm{no}.\mathrm{of}\mathrm{hours}\right)\ast {\displaystyle \frac{\mathrm{12,558}}{8}}+\mathrm{Animal}\mathrm{power}\left(\mathrm{no}.\mathrm{of}\mathrm{hours}\right)\ast {\displaystyle \frac{\mathrm{12,558}}{8}}+\\ +\mathrm{E}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{c} \mathrm{e}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y}\left(\mathrm{k}\mathrm{W}\mathrm{h}\right)\ast 3600+\mathrm{D}\mathrm{i}\mathrm{e}\mathrm{s}\mathrm{e}\mathrm{l} \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}\left(\mathrm{l}\right)\ast \mathrm{35,581}+\mathrm{C}\mathrm{h}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{l} \mathrm{f}\mathrm{e}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{s}\left(\mathrm{k}\mathrm{g} \mathrm{N}\right)\ast 92.519\\ +\mathrm{C}\mathrm{h}\mathrm{e}\mathrm{m}\mathrm{i}\mathrm{c}\mathrm{a}\mathrm{l} \mathrm{f}\mathrm{e}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{s}\left(\mathrm{k}\mathrm{g} \mathrm{o}\mathrm{f} P_2{O}_5\right)\ast \mathrm{20,340}+\mathrm{O}\mathrm{r}\mathrm{g}\mathrm{a}\mathrm{n}\mathrm{i}\mathrm{c} \mathrm{f}\mathrm{e}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{s}\left(\mathrm{k}\mathrm{g}\right)\ast 682\\ +\mathrm{P}\mathrm{e}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{s} \mathrm{a}\mathrm{n}\mathrm{d} \mathrm{H}\mathrm{e}\mathrm{r}\mathrm{b}\mathrm{i}\mathrm{c}\mathrm{i}\mathrm{d}\mathrm{e}\mathrm{s}\left(\mathrm{k}\mathrm{g} \mathrm{o}\mathrm{r} \mathrm{l}\right)\ast \mathrm{418,600}+\mathrm{S}\mathrm{e}\mathrm{e}\mathrm{d}\mathrm{s}\left(\mathrm{k}\mathrm{g}\right)\ast \mathrm{19,080}\end{array}$$

(1)

$$\mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left({\mathrm{k}\mathrm{J}/\mathrm{h}\mathrm{a}}^{-1}\right)={\displaystyle \frac{\mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left(\mathrm{k}\mathrm{J}/\mathrm{p}\mathrm{l}\mathrm{o}\mathrm{t}\right)}{{\mathrm{P}\mathrm{l}\mathrm{o}\mathrm{t} \mathrm{a}\mathrm{r}\mathrm{e}\mathrm{a} (\mathrm{m}}^2)}}\ast \mathrm{10,000}$$

(2)

$$\mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left(\mathrm{k}\mathrm{J}/\mathrm{k}\mathrm{g} \mathrm{D}\mathrm{M}\right)={\displaystyle \frac{\mathrm{E}\mathrm{n}\mathrm{e}\mathrm{r}\mathrm{g}\mathrm{y} \mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{u}\mathrm{m}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n} (\mathrm{k}\mathrm{J}/\mathrm{h}\mathrm{a})}{\mathrm{G}\mathrm{r}\mathrm{a}\mathrm{i}\mathrm{n} \mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\left(\mathrm{k}\mathrm{g} \mathrm{D}\mathrm{M} {\mathrm{h}\mathrm{a}}^{-1}\right)}}$$

(3)

The oxygen (Oc) content (%) of whole cornmeal was calculated using the following Formula (4), according to the CHNS analysis results obtained with the COSTECH 4010 analyser and the proximate ash analysis [20]:

Oc = 100 − Carbon (%) − Hydrogen (%) − Nitrogen (%) − Sulphur (%) − Ash (%),

(4)

2.5. Calculation of Nutritional and Caloric Values

The nutritional and caloric values of whole-ground cornmeal were calculated using specific and widely cited empirical formulas. These equations employ empirically derived coefficients (with 4–6 or 2–4 significant digits) and the concentrations of chemical elements or macronutrients in the analyzed material, expressed as decimal fractions or percentages.

Nutritional energy value (NEVc) of whole-ground cornmeal (kJ/kg dry matter) calculated as Formula (5):

NEVc = 11,400∙P + 35,000∙F + 16,900∙St,

(5)

in which 11,400, 35,000, and 16,900 represent the Atwater metabolizable energy factors for protein (P), fat (F), and starch (St), respectively. The values of P, F, and St were determined using the INSTALAB 660 analyser and expressed as decimal fractions.

Higher Heating Value (HHVc), or Gross Heating Value, was estimated using the approximation Formula (6) by Wojciech et al. [21]:

HHVc = 34,910∙C + 117,830∙H + 10,050∙S + 10,340∙O − 1510∙N − 2110∙A,

(6)

in kJ/kg dry matter. The coefficients correspond to the empirical energy equivalents of the elements carbon (C), hydrogen (H), sulphur (S), oxygen (O), nitrogen (N), and ash (A). Elemental contents were determined using the COSTECH 4010 analyser and electric oven incineration (600 °C), expressed as decimal fractions [21,22].

Lower Heating Value (LHVc), also known as Net Heating Value, was calculated according to Mendeleev’s Formula (7) [23]:

LHVc = 339∙C + 1030∙H − 109∙(O − S) − 25.12∙W,

(7)

in kJ/kg, based on empirical coefficients and the percentage contents of carbon (C), hydrogen (H), sulphur (S), oxygen (O), and moisture (W).

2.6. The Sustainability Indicators

The sustainability indicators were calculated as follows:

• Energy balance (kJ kg⁻¹ and kJ ha⁻¹): calculated as the difference between the output (produced) energy and the input (consumed) energy.
• Energy efficiency ratio: determined as the ratio between output energy and input energy.

Statistical analysis: mean values, standard deviations (SDs), standard errors, and graphical representations with error bars were generated using Microsoft Excel software.

3. Results and Discussion

General information on the studied maize (Zea mays L.) varieties and populations is presented in Table 2, including plot location and area (m²), farming systems, and productivity indicators such as cob production (kg plot⁻¹), grain yield per cob (%), grain yield (kg ha⁻¹, expressed in dry matter—DM), and thousand grain weight (TGW, g).

Analysis of these data reveals that all presented parameters exhibited a high degree of variability, both qualitative and quantitative. This variability is partly explained by the fact that the analyzed genotypes cultivated under different environmental and management conditions exhibited different agronomic performances.

The variability of the productivity indicators, assessed through the coefficient of variation (CV, %), is characteristic of each parameter and exceeded the generally accepted upper threshold of 20% for all indicators. The high coefficients of variation observed for most productivity parameters indicate substantial heterogeneity among the studied systems, likely reflecting the combined effects of genotype, environmental conditions, and management practices [24].

Specifically, the coefficient of variation reached 25.01% for thousand grains weight (TGW), 25.79% for grains yield per cob, 51.27% for grains yield (DM), 104.40% for plot area, and 212.86% for cob production. Such variability is typical for traditional maize varieties cultivated under diverse environmental conditions and farming systems. The high variability observed in agronomic indicators can be explained by the interaction between genotype (G), environmental conditions (E), and management practices (M), commonly referred to in agronomy as the G × E × M interaction [25].

Another important detail, which significantly negatively influenced the production of maize grains, was the very low grain yield per cob (%) in some of varieties like Florian 12R (34.60%) and 16R (27.93%) and Mesteceni 12 and 14R (49.70%) varieties, due to the attack of the grain moth (Sitotogra cerealella) (Figure 1).

3.1. The Energy Consumption

The first set of results presented in this study concerns the energy consumption associated with the cultivation of local maize (Zea mays L.) varieties and populations under different cropping systems. The analysis is based on the quantification of energy inputs derived from both labour and material resources, expressed in energy units (kJ ha⁻¹), in order to compare the performance and sustainability of the studied varieties. Romaneckas et al. [10] reported that maize–legume intercropping systems can influence the main energy indicators of crop production, demonstrating that energy performance is strongly affected by biomass productivity and environmental conditions.

According to the data presented in

Table 3. Energy consumption (human labour, animal traction and various materials) for cultivating local maize (Zea mays L.) varieties and populations studied (kJ).

Name of Maize Studied/Energy Consumptions	Mălai Sticlos de Bărăi Corn Only	Optaș de Bărăi Corn Only	Lăpușneac Intercropping	De Maramureș Intercropping	De Maramureș Corn Only	Florian Intercropping	Mesteceni Intercropping	Porumb Moldovenesc Intercropping	Bob Tare Intercropping	Fundulea 423 Corn Only
Human labour	31,499.65	43,298.94	21,191.62	44,625.75	104,724.75	32,964.75	175,812	46,307.63	87,121.12	43,117.36
Animal power	0	0	0	4485	26,910	7848.7	298,252.5	15,697.5	15,697.5	0
Electric energy	0	0	7200	0	0	0	0	0	0	0
Diesel fuel	2,531,943.9	316,670.9	14,232.4	112,817.1	1,694,163.9	189,522.2	177,905	213,486	155,488.9	40,942.6
Gasoline	0	0	65,930	0	0	0	0	0	0	0
Chemical fertilizers	0	0	0	528,680	3172.1	0	0	0	0	200,997
Organic fertilizers	0	0	136,400	0	0	168,795	818,400	0	68,200	0
Pesticides	0	0	0	0	0	0	0	0	0	1485.26
Herbicides	0	0	0	0	0	0	0	0	0	38,678.64
Seed	277,732	49,595	6973.82	54,500	327,000	38,150	95,375	57,225	49,595	8460.14
Total energy/plot (kJ)	2,841,175.6	409,564.8	251,927.8	745,107.9	5,324,878.6	437,280.6	1,565,744	332,716.1	376,102.5	333,681.1
Other types of energy (10%)	284,117.5	40,956.4	25,192.7	74,510.7	532,487.8	43,728.1	156,574.4	33,271.6	37,610.2	33,368.1
Total kJ/plot	3,125,293.2	450,521.3	277,120.6	819,618.7	5,857,366.5	481,008.8	1,722,319.	365,987.7	413,712.9	367,049.2
Total kJha−1	5,580,880.7	4,505,213.2	13,856,032	16,392,374.6	19,524,555.1	10,689,083.7	8,611,594.8	1,742,798.8	4,137,128.6	14,896,476.5
kJ/kg DM	818.79	1650.26	4869.45	2505.33	3414.58	4515.88	2664.48	728.59	1963.98	7330.94

, the highest energy consumption values were associated with the cultivation of the De Maramureș variety, both under monocropping (19,524,555.1 kJ ha⁻¹) and under intercropping conditions (16,392,374.6 kJ ha⁻¹), followed by the Fundulea 423 hybrid in monocropping (14,896,476.5 kJ ha⁻¹) and the Lăpușneac population in intercropping conditions (13,856,032 kJ ha⁻¹). Intercropping systems generally showed lower energy consumption compared to monocropping, suggesting a more efficient use of resources. Similar results were reported by Romaneckas et al. [10], who showed that intercropping systems improve energy efficiency and reduce overall energy inputs compared to monocropping. In addition, Mandal et al. [26] demonstrated that maize-based intercropping systems can improve energy use efficiency and net energy production compared with monocropping systems. Relatively high energy consumption values were also recorded for the Florian (10,689,083.7 kJ ha⁻¹) and Mesteceni (8,611,594.8 kJ ha⁻¹) populations cultivated under intercropping conditions. Lower energy consumption values were observed for the Bob tare population (4,137,128.6 kJ ha⁻¹) under intercropping, and for two varieties cultivated in the monocropping system, Optaș de Bărai (4,505,213.2 kJ ha⁻¹) and Mălai sticlos de Bărai (5,580,880.7 kJ ha⁻¹). The lowest energy consumption value was recorded for the Porumb Moldovenesc variety (1,742,798.8 kJ ha⁻¹), cultivated under intercropping.

The analysis of energy inputs further revealed that diesel fuel and fertilizers are also important contributors to total energy consumption. This is consistent with previous studies showing that fertilizers alone can account for more than 50% of total energy input in maize production systems [27], while other studies have highlighted their dominant role in overall energy consumption [28]. Therefore, variations in fertilizer application rates and the level of mechanization largely explain the differences observed among the studied variants.

Significant differences in energy use efficiency (kJ/kg DM) were observed when comparing the Porumb Moldovenesc variety (intercropping) with the hybrid Fundulea 423, indicating that certain local varieties require substantially lower energy input per unit of yield. These findings are consistent with previous studies reporting that maize production systems based on hybrid varieties and intensive input use tend to be associated with higher energy consumption, whereas traditional systems relying on local varieties are often more energy-efficient [8,29]. Consequently, the use of locally adapted maize varieties may contribute to reducing energy inputs and improving the sustainability of agricultural systems.

3.2. The Content of the Energy Macronutrients

The moisture, protein, fat, starch and ash content of whole cornmeal obtained from the studied maize varieties and populations were determined using the INSTALAB 660 analyzer (

Table 4. The content of the energy macronutrients (moisture, protein, fats, starch, and ash) of cornmeal from local varieties and population studied.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Cornmeal Macronutrients Content (INSTALAB 660)
	Moisture (W)	Protein (P)	Fat (F)	Starch (S)	Ash (A)
	(%)
Mălai sticlos de Bărăi 12R (corn only), organic	12.9	10.93	6.27	52.34	8.26
Optaș de Bărăi 8R (corn only), organic	12.7	9.92	7.05	52.88	7.95
Lăpușneac 8R, orange seeds, white cob (intercropping)	12.3	11.05	4.59	57.95	5.61
Lăpușneac 8R, red seeds, white cob (intercropping)	12.6	11	3.23	61.41	5.36
De Maramureș 12R (intercropping)	13.1	7.04	6.24	58.49	7.91
De Maramureș 14R (intercropping)	11.7	11.18	7.34	53.35	10.31
De Maramureș 12R (corn only)	12	11.78	8.54	50.96	10.1
De Maramureș 14R (corn only)	11.7	13.02	6.67	52.51	9.11
Florian 12R (intercropping)	12.5	12.53	5.59	53.24	6.94
Florian 16R (intercropping)	14.4	10.97	4.95	54.97	7.91
Mesteceni 12R and 14R (intercropping)	13.3	12.38	7.21	47.96	10.97
Porumb Moldovenesc 12R (intercropping), organic	11.6	11.24	6.48	55.46	6.23
Bob tare 14R, white cob (intercropping)	12.4	10.71	5.92	55.57	7.26
Bob tare 14R, red cob (intercropping)	12.1	10.98	5.07	57.73	4.91
Fundulea 423, 16R (corn only)	10.3	8.14	7.35	57.39	5.76
Mean	12.373	10.86	6.17	54.81	7.64
SD	0.93	1.56	1.33	3.43	1.89
CV (%)	7.473	14.32	21.56	6.26	24.74

). The results revealed noticeable variation among genotypes for all analyzed macronutrients.

The moisture content ranged from 10.3% to 14.4%, indicating that the grains were relatively dry compared to the maize humidity standard levels of 15.5% at harvest and 14% during storage. In this context, the rapid dry-down of maize observed may be considered a favourable characteristic, not only in the Fundulea 423 hybrid but also in the other analyzed genotypes. Considerable variation in maize grain moisture content among different genotypes has been reported in the literature. For example, Hamisu and his team [30] recorded a moisture content of 8% in the improved variety Sammaz 14, compared with 7.5% and 6.5% in local and Golden Strawberry varieties, respectively. Other studies also reported substantial variation, with moisture contents of 13.0%, 11.0%, 8.0% and 12.5% in sweet corn, popcorn, white corn and yellow corn, respectively [31]. These differences highlight the influence of genetic factors on grain moisture content, as well as the potential impact of environmental and experimental conditions.

Protein content varied among the analyzed genotypes, with an overall mean value of 10.858%. Only two varieties showed values below this mean: De Maramureș 12R cultivated under intercropping (7.04%) and the hybrid Fundulea 423 (8.14%). Most genotypes showed protein levels close to or higher than the overall mean (10.86%), with values ranging from 7.04% to 13.02%. The highest protein content (12.28%) was obtained with the application of 120 kg ha⁻¹ nitrogen combined with green winter pea manure [32]. The coefficient of variation for protein content for all maize varieties studied was relatively high (CV = 14.32%), suggesting also that genetic factors play an important role in the observed variation. In addition, the variation in protein content observed in this study may be attributed to differences in nitrogen availability and fertilization practices, as nitrogen fertilization is known to significantly increase maize grain protein concentration [32,33]. Several local maize varieties showed higher protein levels than the hybrid Fundulea 423, highlighting the potential nutritional value of traditional germplasm. A relatively wide variation was observed for fat content, which ranged from 3.23% to 8.54%, with a mean value of 6.17%. These values are generally higher than those commonly reported in the literature (2–6%, with an average of approximately 4.5%) [34,35]. Similar values have been reported in maize grain composition studies, where mean fat contents of approximately 3.6–4.5% were observed under typical cultivation conditions [36]. The relatively high coefficient of variation (CV = 21.56%) indicates considerable variability among the studied genotypes. This variability may reflect the combined influence of genotype and cultivation practices, as previous research has shown that agronomic factors such as fertilization regimes, plant density and environmental conditions can significantly influence the oil content of maize grains [37]. In our study as well, the observed variability appears to be primarily associated with fertilization practices, while genetic background plays a secondary role.

Starch represented the major carbohydrate fraction of the analyzed samples, ranging from 47.96% to 61.41%, with a mean value of 54.81%, and showing the lowest coefficient of variation among the analyzed macronutrients (CV = 6.26%). Considerable variability in carbohydrate-related components among maize genotypes has also been reported by Hamisu et al. [30], who observed the highest carbohydrate content (94.67%) in the Golden Strawberry maize variety. In our study, a significant reduction in starch content was observed only in the Mesteceni variety cultivated under an intercropping system, which, according to the data in Table 3, is associated with higher organic fertilization levels. Illés et al. [33] indicate that starch accumulation in maize grains can be influenced by both genotype and fertilization practices, with significant differences observed among hybrids and nutrient treatments.

The ash content showed a trend similar to that of the previously analyzed macronutrients, differing mainly in numerical range: Values ranged from 4.91% to 10.97%, with a mean of 7.64%, and it presented the highest coefficient of variation among all measured components (CV = 24.74%). In their study, Hamisu and his team [30] reported that the local maize variety Hakorin Hajiya exhibited a higher ash content (4%), indicating a greater mineral composition compared with improved varieties. Based on the information presented in Table 3, the variability in ash content appears to be primarily associated, also in this situation, with technological factors, particularly chemical and organic fertilization.

3.3. The Content of the Major Elemental Components

Results of the analyses of the major elemental components (C, H, N, S–O), as well as the ash (A) and moisture (W) contents in the whole cornmeal obtained from the studied maize (Zea mays L.) varieties and populations, are summarized in

Table 5. Results of elemental (CHNS-O) and proximate analysis of ash (A) and moisture (W) in the whole cornmeal from the studied maize (Zea mays L.) varieties and populations.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	CHNS Elements Content (COSTECH 4010)				Oxygen * (Oc)	Oven Determinations
	Carbon (C)	Hydrogen (H)	Sulphur (S)	Nitrogen (N)		Ash (A)	Moisture (W)
	(%)
Mălai sticlos de Bărăi 12R (corn only), organic	44.26	6.81	0	1.88	45.88	1.17	10.82
Optaș de Bărăi 8R (corn only), organic	44.12	6.64	0	1.86	45.9	1.48	10.69
Lăpușneac 8R, orange seeds, white cob (intercropping)	43.15	6.63	0	1.49	47.34	1.39	10.44
Lăpușneac 8R, red seeds, white cob (intercropping)	45.49	6.88	0	2.27	44.23	1.13	10.99
De Maramureș 12R (intercropping)	43.51	6.7	0	1.48	46.96	1.35	10.76
De Maramureș 14R (intercropping)	42.98	6.49	0	1.40	47.78	1.35	11.19
De Maramureș 12R (corn only)	44.56	6.54	0	1.9	45.38	1.62	11.13
De Maramureș 14R (corn only)	43.35	6.5	0	1.57	47.14	1.44	10.95
Florian 12R (intercropping)	43.77	6.48	0	2.1	46.03	1.62	11.22
Florian 16R (intercropping)	44.22	6.52	0	1.88	46.02	1.36	11.05
Mesteceni 12R and 14R (intercropping)	44.59	7.26	0	6.69	39.95	1.51	11.12
Porumb Moldovenesc 12R (intercropping), organic	45.9	6.46	0	1.89	44.18	1.57	9.91
Bob tare 14R, white cob (intercropping)	43.87	6.80	0	1.79	46.07	1.47	10.98
Bob tare 14R, red cob (intercropping)	44.13	6.63	0	2.34	45.66	1.24	10.07
Fundulea 423, 16R (corn only)	45.12	6.64	0	1.43	45.52	1.29	9.48
Mean	44.20	6.67	0	2.13	45.60	1.40	10.72
SD	0.84	0.21	0	1.29	1.87	0.12	0.52
CV (%)	1.90	3.15	0	60.72	4.09	10.82	4.87

* Oc (Oxygen calculated) = 100 − C − H − S − N − A.

.

These parameters—carbon (C), hydrogen (H), nitrogen (N), sulphur (S), oxygen (Oc), ash (A), and moisture (W)—were quantified in order to enable the estimation of the calorific values (HHVc and LHVc) of the whole cornmeal, as they represent key constituents of the energy-related macronutrients previously described. The same elemental composition of biomass (C, H, N, O and S) has been used by Brandić et al. [38], in estimating the HHV (Higher Heating Value) of corn biomass and to evaluate the calorific potential and combustion behaviour.

The elemental composition of the analyzed cornmeal samples showed relatively stable values for the main structural components of biomass. The carbon (C) content ranged from 42.98% to 45.90%, with a mean of 44.20%, exhibiting the lowest coefficient of variation (CV = 1.90%). Similarly, hydrogen (H) content varied between 6.46% and 7.26%, with a mean value of 6.67% and a low coefficient of variation (CV = 3.15%). These two elements play a key role in the energetic potential of biomass, as higher carbon and hydrogen contents generally contribute to increased calorific values due to their direct participation in combustion reactions.

Sulphur (S) was below the detection limit (reported as 0) in all samples [39]. In contrast, nitrogen (N) showed the highest variability among the elemental components, ranging from 1.40% to 6.69%, with a mean of 2.13% (CV = 60.72%). This variability was largely influenced by the Mesteceni variety, which showed the highest nitrogen concentration (6.69%). Overall, the elemental composition obtained in this study is consistent with the typical composition of plant biomass, where carbon usually ranges between 42 and 50% and hydrogen between 5 and 6%, while nitrogen and sulphur occur in relatively small amounts [40].

A relatively stable pattern was observed for oxygen (Oc) in the analyzed cornmeal varieties. The oxygen content varied between 39.95% and 47.78%, with a mean of 45.60% and a relatively low coefficient of variation (CV = 4.09%). Comparable elemental compositions were reported by Sulaiman et al. [41], who found values of approximately 48.57% carbon, 0.38% sulphur, 6.22% hydrogen and 55.81% oxygen in maize cob and stalk-based pellets used for energy production. These results confirm that the elemental composition of maize biomass remains within relatively narrow limits despite differences among genotypes and cultivation conditions.

The ash (A) and moisture (W) contents showed different patterns: Ash ranged from 1.13% to 1.62%, with a mean of 1.40% (CV = 10.82%), while moisture varied between 9.48% and 11.22%, with a mean value of 10.72% and a lower coefficient of variation (CV = 4.87%). In comparison, Sulaiman and his team [41], reported ash and moisture contents of 2.20% and 3.25%, respectively. These parameters are particularly important for evaluating the energy potential of biomass, as elemental composition and moisture content directly influence calorific value and combustion efficiency.

3.4. Estimation of the Nutritional Energy Value (NEV)

The nutritional energy values (NEVs) presented in Table 6 reflect the content of metabolizable macronutrients (protein, fat, and starch), expressed as decimal fractions, as well as the application of Atwater energy conversion factors (kJ/kg) specific to each macronutrient. Surprisingly (though perhaps expected) there is a perfect similarity between the coefficients of variation (CV, %) of the macronutrient NEVs and the CVs (%) of their contents, indicating a direct and proportional relationship between chemical composition and the resulting nutritional energy. Furthermore, compared with the NEVs of each individual macronutrient, the variability of the total nutritional energy content of whole cornmeal (kJ/kg) is very low (CV = 2.42%), with a variation range of 12,040.06 to 13,199.37 kJ/kg around a mean value of 12,659.71 kJ/kg. A similarly low variability was observed for the nutritional energy derived from starch (CV = 6.26%), which ranged from 8105.24 to 10,378.29 kJ/kg, around a mean value of 9263.57 kJ/kg.

The lowest NEVs for whole cornmeal (12,040.06–12,285.88 kJ/kg) were recorded for the genotypes Mesteceni 12R and 14R (intercropping), Florian 16R (intercropping), and Mălai sticlos de Bărăi 12R (corn only). In contrast, higher nutritional energy values (12,859.67–13,199.37 kJ/kg) were observed for the genotypes Fundulea 423 (corn only), De Maramureș 12R and 14R (intercropping), De Maramureș 14R (corn only), and Porumb Moldovenesc 12R (intercropping). The highest coefficient of variation (CV = 51.50%) was recorded for the nutritional energy (NEV) produced per 1 ha cultivated with the local maize varieties and populations (24,740,195.04–90,287,743.07 kJ ha⁻¹), as a result, mainly, of maize grains production (kg ha⁻¹DM) variability, which has a CV = 51.50%.

The nutritional energy values (NEVs) of the whole cornmeal of the maize varieties and populations studied are, normally, lower than the energy value of cornmeal.

3.5. Estimation of the Higher Heating Values (HHVs)

The Higher Heating Value (HHV) represents the amount of heat released by the combustion of 1 kg of solid or liquid fuel under conditions in which the water vapours are condensed and the combustion products are cooled to 0 °C [42]. In this context, the results of the HHVs estimations obtained using the approximation formula [23] are presented in Table 7. The elemental Higher Heating Values (HHVs), expressed in kJ/kg, depend on the carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and ash (A) contents of the whole cornmeal, expressed as decimal fractions, as well as on the empirical energy coefficients of the formula. Thus, the HHVs of carbon (C) show a very low coefficient of variation (CV = 1.90%), with a variation range of 15,004.32–16,023.69 kJ/kg and a mean of 15,430.69 kJ/kg. For hydrogen (H), the variability is similarly low (CV = 3.145%), with values ranging from 7611.82 to 8554.46 kJ/kg and a mean of 7853.76 kJ/kg. In the case of oxygen (O), the CV is also low (4.09%), with values between 4130.83 and 4940.45 kJ/kg, and a mean of 4715.32 kJ/kg. The HHVs for nitrogen (N) differ considerably from those of the other elements, showing a very high coefficient of variation (CV = 60.173%), a wide variation range of 21.14–101.20 kJ/kg, and a mean of 32.18 kJ/kg. For ash (A), the CV = 10.819%, with values ranging from 23.84 to 34.18 kJ/kg and a mean of 29.53 kJ/kg, while sulphur (S) values were zero, corresponding to each biomass type.

Table 6. Estimation of the nutritional energy values (NEVs) of whole cornmeal of the studied local varieties and populations, based on Atwater conversion factors [43] *.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Nutritional Energy of the Metabolizable Macronutrients * (kJ/kg)				Total Energy of Whole Cornmeal (kJ ha−1)
	Protein	Fats	Starch	Total
Mălai sticlos de Bărăi 12R (corn only), organic	1246.02	2194.5	8845.46	12,285.98	83,741,239.68
Optaș de Bărăi 8R (corn only), organic	1130.88	2467.5	8936.72	12,535.1	34,220,823
Lăpușneac 8R, orange seeds, white cob (intercropping)	1259.7	1606.5	9793.55	12,659.75	44,347,104.25
Lăpușneac 8R, red seeds, white cob (intercropping)	1254	1130.5	10,378.29	12,762.79	27,924,984.52
De Maramureș 12R (intercropping)	802.56	2184	9884.81	12,871.37	78,064,859.05
De Maramureș 14R (intercropping)	1274.52	2569	9016.15	12,859.67	90,287,743.07
De Maramureș 12R (corn only)	1342.92	2989	8612.24	12,944.16	66,740,088.96
De Maramureș 14R (corn only)	1484.28	2334.5	8874.19	12,692.97	79,711,851.60
Florian 12R (intercropping)	1428.42	1956.5	8997.56	12,382.48	24,740,195.04
Florian 16R (intercropping)	1250.58	1732.5	9289.93	12,273.01	33,578,955.36
Mesteceni 12R and 14R (intercropping)	1411.32	2523.5	8105.24	12,040.06	38,913,473.92
Porumb Moldovenesc 12R (intercropping), organic	1281.36	2268	9372.74	12,922.1	30,909,663.2
Bob tare 14R, white cob (intercropping)	1220.94	2072	9391.33	12,684.27	25,558,804.05
Bob tare 14R, red cob (intercropping)	1251.72	1774.5	9756.37	12,782.59	28,096,132.82
Fundulea 423, 16R (corn only)	927.96	2572.5	9698.91	13,199.37	26,821,119.84
Mean	1237.812	2158.333	9263.57	12,659.71	47,577,135.891
SD	177.243	466.136	579.527	306.917	24,497,662.918
CV%	14.32	21.60	6.26	2.42	51.50

* Atwater conversion factors for cornmeal, whole ground: protein = 11,400 kJ/kg; fat: 35,000 kJ/kg; starch: 16,900 kJ/kg.

Table 6. Estimation of the nutritional energy values (NEVs) of whole cornmeal of the studied local varieties and populations, based on Atwater conversion factors [43] *.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Nutritional Energy of the Metabolizable Macronutrients * (kJ/kg)				Total Energy of Whole Cornmeal (kJ ha−1)
	Protein	Fats	Starch	Total
Mălai sticlos de Bărăi 12R (corn only), organic	1246.02	2194.5	8845.46	12,285.98	83,741,239.68
Optaș de Bărăi 8R (corn only), organic	1130.88	2467.5	8936.72	12,535.1	34,220,823
Lăpușneac 8R, orange seeds, white cob (intercropping)	1259.7	1606.5	9793.55	12,659.75	44,347,104.25
Lăpușneac 8R, red seeds, white cob (intercropping)	1254	1130.5	10,378.29	12,762.79	27,924,984.52
De Maramureș 12R (intercropping)	802.56	2184	9884.81	12,871.37	78,064,859.05
De Maramureș 14R (intercropping)	1274.52	2569	9016.15	12,859.67	90,287,743.07
De Maramureș 12R (corn only)	1342.92	2989	8612.24	12,944.16	66,740,088.96
De Maramureș 14R (corn only)	1484.28	2334.5	8874.19	12,692.97	79,711,851.60
Florian 12R (intercropping)	1428.42	1956.5	8997.56	12,382.48	24,740,195.04
Florian 16R (intercropping)	1250.58	1732.5	9289.93	12,273.01	33,578,955.36
Mesteceni 12R and 14R (intercropping)	1411.32	2523.5	8105.24	12,040.06	38,913,473.92
Porumb Moldovenesc 12R (intercropping), organic	1281.36	2268	9372.74	12,922.1	30,909,663.2
Bob tare 14R, white cob (intercropping)	1220.94	2072	9391.33	12,684.27	25,558,804.05
Bob tare 14R, red cob (intercropping)	1251.72	1774.5	9756.37	12,782.59	28,096,132.82
Fundulea 423, 16R (corn only)	927.96	2572.5	9698.91	13,199.37	26,821,119.84
Mean	1237.812	2158.333	9263.57	12,659.71	47,577,135.891
SD	177.243	466.136	579.527	306.917	24,497,662.918
CV%	14.32	21.60	6.26	2.42	51.50

* Atwater conversion factors for cornmeal, whole ground: protein = 11,400 kJ/kg; fat: 35,000 kJ/kg; starch: 16,900 kJ/kg.

Table 7. Estimation of the Higher Heating Values (HHVs) of the whole cornmeal of the studied local varieties and populations.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Higher Heating Values (HHVs) * of the Whole Cornmeal Elements (C, H, N, S, O) and Ash (A)						Higher Heating Values (HHVs) of the Whole Cornmeal
	Carbon (C)	Hydrogen (H)	Sulfur (S)	Oxygen (O)	Nitrogen (N)	Ash (A)
	kJ/kg						kJ/kg	kJ ha−1
Mălai sticlos de Bărăi 12R (corn only), organic	15,451.17	8024.22	0	4743.99	28.39	24.69	28,166.31	191,981,541.696
Optaș de Bărăi 8R (corn only), organic	15,402.29	7823.91	0	4746.06	28.090	31.23	27,912.95	76,202,353.500
Lăpușneac 8R, orange seeds, white cob (intercropping)	15,063.67	7812.13	0	4894.96	22.50	29.33	27,718.92	97,099,383.766
Lăpușneac 8R, red seeds, white cob (intercropping)	15,880.56	8106.70	0	4573.38	34.28	23.84	28,502.53	62,363,524.700
De Maramureș 12R (intercropping)	15,189.34	7894.61	0	4855.66	22.35	28.49	27,888.78	169,145,462.830
De Maramureș 14R (intercropping)	15,004.32	7647.17	0	4940.45	21.14	28.49	27,542.31	193,374,572.55
De Maramureș 12R (corn only)	15,555.90	7706.08	0	4692.29	28.70	34.18	27,891.39	143,808,048.088
De Maramureș 14R (corn only)	15,133.49	7658.95	0	4874.28	23.70	30.38	27,612.62	173,407,253.600
Florian 12R (intercropping)	15,280.11	7635.38	0	4759.50	31.71	34.18	27,609.10	55,162,983.80
Florian 16R (intercropping)	15,437.207	7682.52	0	4758.47	28.39	28.70	27,821.10	76,118,535.072
Mesteceni 12R and 14R (intercropping)	15,566.37	8554.46	0	4130.83	101.20	31.86	28,118.78	90,879,887.264
Porumb Moldovenesc 12R (intercropping), organic	16,023.69	7611.82	0	4568.22	28.54	33.13	28,142.05	67,315,793.168
Bob tare 14R, white cob (intercropping)	15,315.02	8012.44	0	4763.64	27.03	31.02	28,033.05	56,486,593.735
Bob tare 14R, red cob (intercropping)	15,405.78	7812.13	0	4721.24	35.33	26.16	27,877.66	61,275,092.284
Fundulea 423, 16R (corn only)	15,751.39	7823.91	0	4706.77	21.60	27.22	28,233.26	57,369,984.320
Mean	15,430.69	7853.76	0	4715.32	32.18	29.53	27,938.05	104,799,400.7
SD	291.80	246.99	0	192.70	19.54	3.20	264.91	53,356,269.8
CV%	1.90	3.15	0	4.09	60.73	10.82	0.95	50.9134

* acc. to Channiwala and Parikh (2002), cited by Wojciech et al. [21], formula: HHVs = 34,910∙C + 117,830∙H + 10,050∙S + 10,340∙O − 1510∙N − 2110∙A (kJ/kg and kJ ha⁻¹).

Table 7. Estimation of the Higher Heating Values (HHVs) of the whole cornmeal of the studied local varieties and populations.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Higher Heating Values (HHVs) * of the Whole Cornmeal Elements (C, H, N, S, O) and Ash (A)						Higher Heating Values (HHVs) of the Whole Cornmeal
	Carbon (C)	Hydrogen (H)	Sulfur (S)	Oxygen (O)	Nitrogen (N)	Ash (A)
	kJ/kg						kJ/kg	kJ ha−1
Mălai sticlos de Bărăi 12R (corn only), organic	15,451.17	8024.22	0	4743.99	28.39	24.69	28,166.31	191,981,541.696
Optaș de Bărăi 8R (corn only), organic	15,402.29	7823.91	0	4746.06	28.090	31.23	27,912.95	76,202,353.500
Lăpușneac 8R, orange seeds, white cob (intercropping)	15,063.67	7812.13	0	4894.96	22.50	29.33	27,718.92	97,099,383.766
Lăpușneac 8R, red seeds, white cob (intercropping)	15,880.56	8106.70	0	4573.38	34.28	23.84	28,502.53	62,363,524.700
De Maramureș 12R (intercropping)	15,189.34	7894.61	0	4855.66	22.35	28.49	27,888.78	169,145,462.830
De Maramureș 14R (intercropping)	15,004.32	7647.17	0	4940.45	21.14	28.49	27,542.31	193,374,572.55
De Maramureș 12R (corn only)	15,555.90	7706.08	0	4692.29	28.70	34.18	27,891.39	143,808,048.088
De Maramureș 14R (corn only)	15,133.49	7658.95	0	4874.28	23.70	30.38	27,612.62	173,407,253.600
Florian 12R (intercropping)	15,280.11	7635.38	0	4759.50	31.71	34.18	27,609.10	55,162,983.80
Florian 16R (intercropping)	15,437.207	7682.52	0	4758.47	28.39	28.70	27,821.10	76,118,535.072
Mesteceni 12R and 14R (intercropping)	15,566.37	8554.46	0	4130.83	101.20	31.86	28,118.78	90,879,887.264
Porumb Moldovenesc 12R (intercropping), organic	16,023.69	7611.82	0	4568.22	28.54	33.13	28,142.05	67,315,793.168
Bob tare 14R, white cob (intercropping)	15,315.02	8012.44	0	4763.64	27.03	31.02	28,033.05	56,486,593.735
Bob tare 14R, red cob (intercropping)	15,405.78	7812.13	0	4721.24	35.33	26.16	27,877.66	61,275,092.284
Fundulea 423, 16R (corn only)	15,751.39	7823.91	0	4706.77	21.60	27.22	28,233.26	57,369,984.320
Mean	15,430.69	7853.76	0	4715.32	32.18	29.53	27,938.05	104,799,400.7
SD	291.80	246.99	0	192.70	19.54	3.20	264.91	53,356,269.8
CV%	1.90	3.15	0	4.09	60.73	10.82	0.95	50.9134

* acc. to Channiwala and Parikh (2002), cited by Wojciech et al. [21], formula: HHVs = 34,910∙C + 117,830∙H + 10,050∙S + 10,340∙O − 1510∙N − 2110∙A (kJ/kg and kJ ha⁻¹).

The HHVs (kJ) per 1 kg of whole cornmeal from the studied genotypes were relatively stable (CV = 0.95%), with a narrow variation range of 27,542.31 to 28,502.53 kJ/kg and a mean of 27,938.05 kJ/kg, but quite large compared to the HHV of birch, beech, pine and spruce wood and close to those of coal [21].

In contrast, the HHVs expressed per hectare (kJ ha⁻¹) for the analyzed maize genotypes exhibited very high variability (CV = 50.913%), closely reflecting the variability of grain yield (CV = 51.27%). The values ranged from 55,162,983.80 to 193,374,572.55 kJ ha⁻¹, with a mean of 104,799,400.7 kJ ha⁻¹.

Among the studied varieties and local populations, the following genotypes were distinguished by their lower or higher HHVc values (kJ ha⁻¹): Florian 12R (intercropping), Bob tare 14R, white cob (intercropping), Fundulea 423, 16R (corn only), De Maramureș 12R and 14R (intercropping), Mălai sticlos de Bărăi 12R (corn only), and De Maramureș 14R (corn only).

3.6. Estimation of the Lower Heating Values (LHVs)

The Lower Heating Value (LHV) differs from the Higher Heating Value (HHV) by the heat of vaporization of the moisture present in the fuel, as well as the moisture generated during the combustion of hydrogen [42]. The LHV results, calculated using the Mendeleev approximation formula [23] and presented in

Table 8. Estimation of Lower Heating Values (LHVs) of the whole cornmeal of the studied local varieties and populations.

Name of the Local Maize (Zea mays L.) Varieties and Populations Studied	Lower Heating Values (LHVs) ∗ of the Cornmeal Elements (CHS-O) and Moisture (W)					Lower Heating Values (LHVs) of the Whole Cornmeal
	Carbon (C)	Hydrogen (H)	Sulfur (S)	Oxygen (O)	Moisture (W)
	(kJ/kg)					kJ/kg	kJ ha−1
Mălai sticlos de Bărăi 12R (corn only), organic	15,004.140	6980.250	0	5000.920	271.798	16,711.672	113,906,753.63
Optaș de Bărăi 8R (corn only), organic	14,956.680	6806.000	0	5003.100	268.533	16,491.047	45,020,558.86
Lăpușneac 8R, orange seeds, white cob (intercropping)	14,627.850	6795.750	0	5160.060	262.253	16,001.287	56,052,509.06
Lăpușneac 8R, red seeds, white cob (intercropping)	15,421.110	7052.000	0	4821.070	276.069	17,375.971	38,018,624.99
De Maramureș 12R (intercropping)	14,749.890	6867.500	0	5118.640	270.291	16,228.459	98,425,602.62
De Maramureș 14R (intercropping)	14,570.220	6652.250	0	5208.020	281.093	15,733.357	110,463,900.90
De Maramureș 12R (intercropping)	15,105.840	6703.500	0	4946.420	279.586	16,583.334	85,503,672.17
De Maramureș 14R (corn only)	14,695.650	6662.500	0	5138.260	275.064	15,944.826	100,133,507.28
Florian 12R (intercropping)	14,838.030	6642.000	0	5017.270	281.846	16,180.914	32,329,465.37
Florian 16R (intercropping)	14,990.580	6683.000	0	5016.180	277.576	16,379.824	44,815,198.46
Mesteceni 12R and 14R (intercropping)	15,116.010	7441.500	0	4354.550	279.334	17,923.626	57,929,157.94
Porumb Moldovenesc 12R (intercropping), organic	15,560.100	6621.500	0	4815.620	248.939	17,117.041	40,943,961.59
Bob tare 14R, white cob (intercropping)	14,871.930	6970.000	0	5021.630	275.818	16,544.482	33,337,132.04
Bob tare 14R, red cob (intercropping)	14,960.070	6795.750	0	4976.940	252.958	16,525.922	36,323,975.68
Fundulea 423, 16R (corn only)	15,295.680	6806.000	0	4961.680	238.138	16,901.862	34,344,584.40
Mean	14,984.252	6831.967	0	4970.691	269.286	16,576.242	61,836,573.665
SD	283.349	214.861	0	203.140	13.102	575.588	30,654,851.447
CV%	1.891	3.145	0	4.087	4.865	3.472	49.574

* Mendeleev approximation formula [23]: LHVc = 339∙C + 1030∙H − 109∙(O − S) − 25.12∙W.

, depend on the carbon (C), hydrogen (H), sulphur (S), oxygen (O), and moisture (W) contents of the whole cornmeal, expressed in percentages, and on the empirical energy coefficients of the Mendeleev formula. Therefore, the coefficients of variation (CV%) of the LHVs for carbon (1.891%), hydrogen (3.145%), oxygen (4.087%), and moisture (4.865%) are equal to those of these elements from Table 5 and Table 7, and almost as small or large as the coefficients of variation (CV%) of the HHVs for 1 kg (CV = 3.472%) and for the production on 1 ha of whole cornmeal (CV = 49.574%). Other LHV parameters are specific to each variety or population studied.

Thus, the elemental LHV dispersion (kJ/kg) for whole cornmeal ranged from 14,570.22 to 15,560.10 for carbon (C), from 6621.5 to 7441.5 for hydrogen (H), from 4354.55 to 5208.02 for oxygen (O), between 238.14 and 281.85 for moisture (W), and between 15,733.36 to 17,923.63 for total LHV (kJ/kg), as with the previously mentioned wood species [21], while the LHV per hectare ranged from 32,329,465.37 to 113,906,753.63 kJ ha⁻¹.

The mean elemental LHVs (kJ/kg) of the whole cornmeal were: 14,984.252 for carbon (C), 6831.967 for hydrogen (H), 4970.691 for oxygen (O), 269.286 for moisture (W), 16,576.242 for total LHV/kg, and 61,836,573.67 kJ ha⁻¹ for LHV/ha.

Among the local maize varieties and populations for which LHVs were determined, the following genotypes were distinguished: Mălai sticlos de Bărăi 12R (corn only), De Maramureș 14R (intercropping), De Maramureș 14R (corn only), Florian 12R (intercropping), Mesteceni 12 and 14R (intercropping), Porumb Moldovenesc 12R (intercropping), and Fundulea 423–16R (corn only).

The higher (HHV) and lower (LHV) calorific values of whole cornmeal were greater than or similar to those of different forest species of wood, suggesting a new use of corn kernels, that of fuel.

3.7. The Energy Balance of Cultivation Local Maize Varieties and Populations

The results of the energy balance for the local maize varieties and populations studied are similar to the previous ones and additionally confirm the relevance of this indicator as a measure of sustainability. First, the energy balance is positive for all types of energy indicators (NEV, HHV, and LHV) and for all maize genotypes studied. Then, there are only 6 cases out of 45 in which the order of magnitude of the energy values (NEVs, HHVs, LHVs) of the whole cornmeal is not maintained among the genotypes analyzed.

Although the energy balance is positive in all cases (Figure 2), we identified three classification groups of genotypes based on the overall mean and standard deviation (SD) of the NEVs, HHVs, and LHVs of their nutritional and caloric energy balance (kJ ha⁻¹). Values ≥ mean were considered highly sustainable, values between the mean and SD were considered moderately sustainable, and values below SD were considered low-performing. The groups are presented below:

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High positive sustainable energy balances (≥mean): Mălai sticlos de Bărai (corn only), De Maramureș 14R and 12R (intercropping), De Maramureș 12R and 14R (corn only);

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Moderate positive sustainable energy balances (≥SD and <mean): Lăpușneac 8R, orange seeds (intercropping), Mesteceni 12 and 14R (intercropping), Optaș de Bărăi (corn only), Porumb Moldovenesc 12R (intercropping), Florian 16R (intercropping), Bob tare 14R, red and white cob;

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Low energy balances (<SD): Lăpușneac 8R, red seeds (intercropping), Florian 12R (intercropping), and Fundulea 423 16R (corn only).

This surprisingly similar grouping of the studied maize varieties and populations is mainly driven by input levels and reflects the inherent sustainability specificity of each maize genotype.

3.8. The Energy Efficiency Rate of the Cultivation of Local Maize Varieties and Populations

The energy efficiency rate or energy rate, calculated as the ratio between the energy produced and the energy consumed (expressed in kJ ha⁻¹), is, according to Figure 3, specific to the cultivation technology and grain yield of each maize genotype studied. Moreover, compared with the energy balance, in this case, the ranking of maize genotypes based on their energy efficiency rate differs across all types of energy assessed (NEVs, HHVs, and LHVs):

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high sustainable energy efficiency rates (≥mean): Porumb Moldovenesc 12R (intercropping), Mălai sticlos de Bărăi (corn only), Optaș de Bărăi 8R (corn only), Bob tare 14R, white and red cob (intercropping);

-

Moderate sustainable energy efficiency rates (≥SD and <mean): De Maramureș 14R (intercropping) and Mesteceni 12 and 14R (intercropping);

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Low energy efficiency rates (<SD): the remaining (eight in the case of NEVs and seven in the case of HHVs and LHVs) maize genotypes.

The energy efficiency rate highlights the cultivation systems of the local maize varieties and populations. In the present study, organic farming systems showed higher energy efficiency, while traditional intercropping systems—relying largely on internal system resources—also proved particularly favourable. These observations are consistent with findings reported in the literature, like Rahman et al. [29], who demonstrated that maize production systems can achieve high energy productivity and technical efficiency, although the final energy performance is strongly influenced by the level of energy inputs and environmental conditions. In addition, Konieczna and his team [44] emphasized that energy efficiency in maize silage production largely depends on the cultivation technology and the energy inputs associated with mechanical operations, fuel consumption, fertilizers, and labour.

4. Conclusions

The sustainability of cultivating local maize (Zea mays L.) varieties and populations is closely related to the performance of cropping systems in terms of energy consumption and production throughout their entire life cycle. The persistence in cultivation of ancestral maize varieties and populations is explained by their high macronutrient content, their potential for technological improvement of nutritional value, and, undeniably, their nutritional and caloric energy values.

The energy balance and energy efficiency rate give originality to the sustainability measurement and importance to the agricultural systems of cultivating local varieties and populations. Thus, the most sustainable, regardless of energy type produced (nutritive or caloric) are the following local studied corn varieties and populations, in descending order: as the energy balance ≥ SD: Mălai sticlos de Bărăi 12R (corn only), organic, De Maramureș 14R and 12R (intercropping), De Maramureș 14R and 12R (corn only), Mesteceni 12&14R (intercropping), followed by the Optaș de Bărăi 8R (corn only), organic, Porumb Moldovenesc (intercropping), organic, Lăpușneac 8R, orange seeds (intercropping), and Bob tare 14R, red cobs (intercropping), as well as Florian 16R (intercropping) and Bob tare 14R, white cobs (intercropping), in two cases each; as the energy efficiency rate ≥ SD: Porumb Moldovenesc 12R (intercropping), organic, Mălai sticlos de Bărăi 12R (corn only), organic, Optaș de Bărăi 8R (corn only), organic, Bob tare 14R, red cob (intercropping), and Bob tare 14 R, white cob (intercropping), followed by the Maramureș 12R and 14R (intercropping) and Mesteceni 12 and 14R (intercropping), in two cases.

The cultivation of local maize varieties and populations can be considered sustainable, as the energy produced by each maize genotype exceeds the energy required for its establishment and maintenance. Moreover, the higher (HHV) and lower (LHV) calorific values of whole cornmeal, which are comparable to or even higher than those of certain forest wood species, highlight the potential of maize kernels as an alternative biomass fuel.