Selection of New Field Pea Varieties for the Organic and Conventional Farming Systems in the Nemoral Climatic Zone

Abstract

Field pea (Pisum sativum L.) is one of the most important grain legumes in European agriculture, having many benefits for agro-ecosystems and also one of the lowest carbon footprints of any crop. However, this crop has many more drawbacks when grown organically as opposed to conventionally. Therefore, our study aims to investigate the performance of newly bred field pea varieties and to test their differences of adaptivity to organic and conventional farming systems. Our study evaluated productivity, as well as the biological and nutritional parameters of the following four new field pea varieties: Lina DS, Egle DS, Ieva DS and Jura DS, all cultivated in the Nemoral climatic zone, where field peas are widely produced. The performance was compared with the long-term standard field pea variety Ingrid. Our study showed that all investigated new varieties had higher productivity compared to the long-term standard Ingrid. The organic cropping system limited the grain yield of field pea, and different varieties tended to respond differently to this type of crop management. Therefore, different varieties should be selected and suggested for organic and conventional cropping systems. Furthermore, with various different responses to the precipitation level, different varieties could be suggested for farming in different regions. The nutritional value (content of proteins and amino acids) also responded significantly to the management system and the selection of field pea variety. Newly bred variety Egle DS demonstrated the highest grain yields, and the highest content of proteins and essential amino acids in the seeds of field pea grown in an organic farming system. Egle DS accumulated 30 percent higher content of arginine compared to the standard variety.

1. Introduction

Legumes are ecosystem service suppliers and create more diverse agricultural systems, while being a safer nutritional source of food and feed [1,2,3,4]. Researchers note that cropping systems which incorporate grain legumes continuously supply N within the agro-ecosystems, decrease N fertilizer rates without decreasing cereal grain yield or grain quality significantly, release high-quality organic matter into the soil, and facilitate nutrients’ circulation by promoting water retention [2,5]. Legume-modified rotations deliver nutrition at lower environmental costs [6]. Diversification of crop rotations with legumes is also beneficial as it can break pest and disease cycles [7], improve soil quality and drought resistance through deep root systems, and support pollinating insects [8]. Legumes could be used as measures for building cropping system productivity and soil fertility, however they are not sufficiently produced or used in cropping systems, nor as a local protein source [9].

The reduction in mineral fertilizers is potentially related also to leguminous plants, such as field pea (Pisum sativum L.). The production of field pea has one of the lowest carbon footprints of any crop [10]. Field pea occupies a relevant place among the choices for growing legumes in many European countries’ agro-ecosystems and in the Nordic/Baltic countries as well. However, this crop also has drawbacks such as logging, poor ground coverage, low competitive ability against weeds, high pest abundance and disease spread, and general low productivity on many soil types [7,9].

Environmental factors and climate change could also have a negative impact on field pea productivity [11,12,13]. One of the key strategies to alleviate the negative impacts of climate change on crop production is the development of new varieties better adapted to the conditions expected in the future. New varieties are expected to be more productive at local environmental and pedo-climatic conditions, and especially resistant or tolerant to biotic and abiotic stressors [14,15]. The breeding of field pea is also lacking investments, even though the research has been identifying possible ways to turn them into more economically attractive crops [9]. Additionally, plant breeding is pivotal in context for the agro-ecological transition of global agri-food systems [16].

Selection of varieties of grain legumes is very important to adapt to climate change in precise regions and climatic zones. The target region in this research—Nemoral climatic zone—is typically characterised by a cool temperate climate, a long-day photoperiod, a mean annual air temperature of 6.5 °C, a sum of active temperatures of 2100–2200 °C, and an average annual precipitation of 500–600 mm [17,18]. However, global climate change increases temperatures, alters the distribution of precipitation, and causes severe droughts [19]. Therefore, newly bred varieties selected under local conditions may be more adapted to the changing European climate, local phenological cycles, soil conditions, and biotic factors such as pests and diseases [20,21]. Varieties may not only have different productivity levels but may also show different yield stability under organic and conventional management systems. Variety selection affects many components of field pea productivity and quality: from seeds number to total grain yield [22,23,24,25], from amino acid content to proteins [26,27,28]. Current knowledge on the genetics of nutritional traits in field pea will greatly assist with crop improvement for specific end uses [27,28].

Many factors interact at the same time, and they all are very important in order to select a field pea variety for the Nemoral climatic zone, especially in the distribution of organic and conventional farming. One of the most important aspects of having more reliance on legumes in agro-ecosystems is better crop productivity and quality. Therefore, the aim of this study was to investigate the productivity and nutritional value of newly bred field pea varieties cultivated in conventional and organic cropping systems in the Nemoral climatic zone. Our objectives were as follows: (i) To ascertain how similar or different the varieties are while producing grain yield and proteins in each cropping system; (ii) To identify varieties that provide better nutritional value in the conventional or organic farming systems; (iii) Especially important is to identify the variety which is superior in the organic cropping system.

2. Material and Methods

2.1. Experimental Site and Conditions

Field experiments were conducted in the 2018, 2019, and 2020 cropping seasons at nine locations in Lithuania, representing arable soils in a Nemoral climatic zone (Figure 1). In this zone, the mean long-term annual air temperature is 6.5 °C, and the growing season lasts from 169 to 202 days.

The soil of the experimental fields in the middle and east of Lithuania was loam or sandy loam Cambisols, and in the northern part of Lithuania it was clay loam Cambisols. Humus varies from 2.3 to 3.0% and pH is close to neutral and varies between 6.4 and 7.5.

Weather data were collected at the stationary meteorological station located in Akademija, using the temperature and rainfall sensors (Figure 2). In 2018, the temperature of the growing season was higher than the 1991–2000 average, especially during the sowing and reproductive phases of field pea growth. The precipitation level during sowing was sufficient and high at the end of the vegetative phase. In 2019, the temperature was higher than perennial at the vegetative phase and harvesting. Meanwhile, rainfall was low during the season, except in May, and increased in the reproductive phase and harvesting. In 2020 the temperature was low in the sowing period but increased during the vegetative phase. The precipitation was high during the first vegetation part and lower during harvesting, which was favorable for many crops development and production.

2.2. Experimental Design and Analysis

The newest varieties of semi-leafless field pea have been developed by traditional selection at the Lithuanian Research Centre for Agriculture and Forestry. The newest varieties Lina DS and Egle DS (registered in 2021), Jura DS (registered in 2017) and Ieva DS (registered in 2015) were selected for the research, and the well-known European field pea variety Ingrid was used as a standard for comparison. The field pea varieties were selected based on productivity, resistance to lodging, diseases and pests, resistance of seed shedding from pods, the attachment height of the lower pods, the average number of pods per plant and plant height. The varieties were certified as the best by the State Plant Breeding Service. The field pea was cultivated in conventional and organic cropping systems. Insecticides, herbicides, and fertilization were only used in the conventional crop system, according to the local usual practices for each site and depending on the year and soil conditions. In organic farming, weed control was conducted by early harrowing, no pest and disease control were applied. Pre-crop in all the sites were cereals.

Field pea was sown in April with the selective seed drill “Wintersteiger Plotseed S” (Wintersteiger, Ried im Innkreis, Austria). Sowing rate was 1.2 million seeds ha⁻¹. The plots of 1.5 m width and 9 m length were harvested in August using Wintersteiger Classic combine (Wintersteiger, Ried im Innkreis, Austria). Complete randomized block design was used with 3 replication blocks. Shortly before harvesting, the samples of mature plants were collected for biometrical analysis. Productivity and grain yield components were determined for a 2 × 0.25 m² sample area in each plot. Data collected for samples were plant density, shoot height, shoot dry biomass, number of productive branches and pods per plant, seed number, and seed weight for each plant and pod. After harvesting, the seed yield in kg ha⁻¹ was calculated for standard 13 percent moisture. Seed quality was indicated by 1000 peas weight, protein content, moisture, and the content of essential amino acids. All samples were taken from each plot.

2.3. Statistical Analysis

Statistical analysis was performed using one-way and two-way ANOVA on the statistical program SAS Enterprise 7.1 computer software. The two main factors for statistical analysis were Factor A: variety, and Factor B: management practice. The combined analysis of the interactions of factors was performed. The averages of data were calculated, however no interaction between the years was found. Means for significant effects were separated using Duncan’s multiple range tests at the 5% probability level (p < 0.05). Homogeneity and normality were verified using Bartlett’s test.

3. Results

3.1. Productivity of New Field Pea Varieties in Different Cropping Systems

Among the five varieties selected for this study, the significantly shorter vegetation length was observed in the organic farming system with no significant differences between the varieties (

Table 1. Yield components and biometric analyses of field pea varieties in organic and conventional cropping systems, averages of 2018–2020.

Cropping System	Varieties	Seeds in Pod (n° pod−1)	Seeds, (n° plant−1)	Seed Grain Yield on Plant (g plant−1)	Productive Nods (n° plant−1)	Vegetation Length (Days)	Plant Height (cm)
Conventional	Jura	5.0 abc	19.2 ab	6.0 abc	2.60 bc	83 ab	70 c
	Lina	5.8 a	24.2 a	6.2 ab	2.96 bc	83 ab	80 b
	Egle	4.9 abc	23.1 a	7.0 a	2.67 bc	90 a	92 a
	Ieva	5.4 ab	22.7 a	6.0 abc	4.04 a	83 ab	69 cd
	Ingrid	4.3 bc	15.3 bc	4.4 cd	2.59 bc	84 ab	73 bc
Organic	Jura	4.3 bc	14.1 bc	4.1 de	2.50 bc	79 bc	56 e
	Lina	3.9 cd	13.4 bc	3.4 de	2.40 c	72 c	58 e
	Egle	3.9 cd	15.7 b	4.8 bcd	2.40 c	76 bc	75 bc
	Ieva	4.1 c	13.7 bc	4.2 cde	3.27 b	78 bc	62 de
	Ingrid	2.9 d	9.8 c	2.5 e	1.47 d	73 c	55 e
Probability		0.053	0.014	0.024	<0.001	0.014	<0.001
Average
Conventional		5.1 a	21.4 a	6.1 a	3.02 a	85 a	78.4 a
Organic		3.9 b	13.6 b	4.0 b	2.59 b	77 b	62.1 b
Total		4.5	17.5	5.1	2.81	81	70.3

Means followed by the same letters in the same column and section do not differ from one another (p ≤ 0.05).

). The variety Lina DS was characterized by the shortest duration of vegetation. When growing varieties under a conventional farming system, reliable differences between varieties were also not obtained regarding vegetation length. However, it was noticed that the new variety Egle DS had the longest vegetation (up to 90 days), while under the organic farming system the yield formed over a significantly shorter timespan (up to 76 days).

The management practices had a significant impact on all components of field pea yield (Table 1) and they were significantly higher under conventional cropping systems. The seed yield (g/plant) varied across cropping systems and varieties. In terms of seed yield between the varieties, Egle DS performed the best (9.3 g/plant in conventional and 4.8 g/plant in organic) in both cropping systems, but differences were not significant compared with other new varieties, except for standard variety Ingrid. Similar trends were obtained with other grain yield components. Non-significant variation between the new varieties was found in conventional and organic farming systems, but all throughout, the results were better than standard. Egle DS was also the highest variety, and Jura DS with Lina DS the smallest among the new varieties. It is also observed that Ieva DS, Lina DS had the highest number of seeds and Ieva DS the highest number of pods, but because of the lower weight of seeds (

Table 2. Effect of field pea varieties and cropping systems on grain yield, protein content and 1000 grain weight.

Cropping Systems	Varieties	Field Pea Grain Yield, kg ha−1			Protein Content, %	1000 Grain Weight
		2018	2019	(g)		g
Conventional	Jura DS	3963 a	4892 ab	5971 ab	24.4 ab	304 a
	Lina DS	3726 ab	4234 bc	6570 a	23.8 bc	284 bc
	Egle DS	4241 a	4479 ab	6541 a	24.9 a	300 ab
	Ieva DS	3218 b	5729 a	5227 b	23.7 bc	274 c
	Ingrid	3060 b	4108 bc	5998 ab	23.7 bc	313 a
Organic	Jura DS	1254 cd	2872 cde	3010 c	22.1 d	284 bc
	Lina DS	1358 cd	2422 de	3339 c	23.2 cd	268 cd
	Egle DS	1722 c	3422 bcd	3150 c	22.4 d	272 c
	Ieva DS	723 d	3711 bcd	2936 cd	20.4 e	253 d
	Ingrid	900 d	1716 e	1973 d	20.5 e	270 cd
Average
Conventional		3767 a	4653 a	6160 a	24.3 a	78.4 a
Organic		1287 b	2988 b	3036 b	21.7 b	62.1 b
Total		2527	3890	4598	23.0	70.3

Means followed by the same letters in the same column and section do not differ from one another (p ≤ 0.05).

), their yield weight was not the highest.

Field pea grain yields in the experimental period varied from the lowest grain yield of 723 kg ha⁻¹ in 2018 to the highest of 6570 kg ha⁻¹ in 2020 (Table 2). Management practice affected the grain yield of field pea each year. The best grain yields were observed for conventional management. All varieties were more productive in the conventional system and produced on average 50 percent higher grain yields than in the organic system. Significant grain yield differences between the varieties and management cropping systems were observed in individual years. All varieties were more productive in 2020 in both cropping (management) systems, when environmental conditions were more favorable for field pea growing. Variety Egle DS had the highest grain yields in both cropping systems, though significantly higher grain yields were obtained only in the 2018 (dry) year in comparison with varieties Ieva DS and Ingrid DS in both cropping systems. The grain yield varies between varieties in different years, and the most productive in 2019 was Ieva DS, however, the difference was not significant in comparison with the variety Egle DS.

3.2. Protein and Amino Acid Content of Different Varieties

The protein content varied across cropping systems and varieties from 23.7 to 24.9 percent in conventional cropping and from 20.4 to 23.2 percent in the organic cropping systems (Table 2). Evaluating the protein content in dry seeds, there were significant differences between cropping systems. The accumulation of proteins in all varieties was significantly higher in conventional farming. The highest content of protein was seen in Egle DS, and it was significantly superior to the other varieties, except Jura DS. In the organic farming system, Lina DS had the greatest protein content among the varieties. It was significantly higher compared to Ieva DS and Ingrid in organic cropping system but no significant differences were found between the same varieties in conventional cropping.

While analyzing several amino acids (

Table 3. Essential amino acids (mg kg⁻¹) in different varieties of field pea cultivated in organic farming system.

Varieties	Histidine	Valine	Tyrosine	Leucine	Arginine	Glycine	Glutamine
Egle DS	1.01 a	0.97 a	0.85 a	1.67 a	2.50 a	1.09 a	4.69 a
Lina DS	0.83 b	0.93 ab	0.84 a	1.62 ab	2.13 cd	1.04 abc	4.44 ab
Ieva DS	1.01 a	0.91 ab	0.84 a	1.66 ab	2.03 cd	1.02 bc	4.41 ab
Jura DS	1.01 a	0.97 a	0.85 a	1.65 ab	2.18 b	1.07 ab	4.60 a
Ingrid	0.77 b	0.87 b	0.79 b	1.56 b	1.92 d	0.99 c	4.27 b
Average	0.92	0.93	0.83	1.63	2.15	1.04	4.48
Variation	7.64	4.56	3.32	3.71	4.22	4.08	4.02
Probability	0.0003	0.0265	0.0441	0.1376	<0.0001	0.0293	0.0377

Means followed by the same letters in the same column and section do not differ from one another (p ≤ 0.05).

), we find out that the differences between varieties exist, but these are not significant in all cases. Among all investigated amino acids, the highest amounts were captured by the variety Egle DS. The amino acid which had the greatest variation between the varieties was arginine. Egle DS accumulated a significantly higher amount of arginine compared to other varieties. It was even 30 percent higher in the seeds of Egle DS than in Ingrid.

4. Discussion

4.1. Field Pea Yield Responses to Cropping System and Variety Selection

Climate change encourages us to verify and make greater use of new varieties with the potential to reduce vulnerability and exploit the opportunities of different cropping systems [10,12,15]. While assessing the components of the grain yield, it was indicated that the seed grain yield per plant was not very high in all varieties in organic farming (2.5 to 4.8 g/plant) and much higher in conventional farming (it varied from 4.4 to 7.0 g/plant). It was also shown that in more northern conditions of the same variety Ingrid, much better results can be obtained in conventional farming [25]. Some authors showed that the number of seeds is more important for grain yield of field pea than the thousand seed weight (TSW) [24,25,29] and the farming system have no significant impact on the pod and seed production [30]. On the contrary, our research shows adverse results, when TSW can become the most important indication, providing benefits while competing in the yield among the newest varieties of field pea.

The grain yield is what the farmer focuses on the most. He puts a lot of effort into getting the grain yield as high as possible; therefore, appropriate tools to help him achieve an adequate grain yield are essential. Results from this study highlight that cropping systems and varieties affected the grain yield of field pea. All varieties were more productive in the conventional farming system. However, when assessing the potential of individual varieties, we can see that the differences between varieties are also larger within the conventional cropping system. Meanwhile, the organic cropping system did not show more significant differences between the same varieties. We can assume that their potential differs only when the growing conditions are better due to more fertile soil. The average field pea grain yield (1530–2924 kg ha⁻¹) over three years in the organic cropping system from this study is in accordance with other studies on field pea [30,31]. Lower grain yields in organic farming have been explained by lower use of fertilizers, higher pest damage, and weed pressure in comparison to conventional farming [31,32]. Varieties with a slightly different vegetation period could react more sensitively or adapt better to the same biotic and abiotic factors. Through trait-based approaches, such as development capacities and resource use efficiency, the trade-offs of individual varieties could be addressed [33]. Delayed phenology can act as an important factor that results in lower grain yield in organic farming compared to conventional farming. Field pea is sensitive to many growing circumstances and growth, development, and productivity of crops are essentially dependent on pedo-climatic conditions. Meanwhile, impact or improvement can be achieved through management practices. In an organic farming cropping system, it is especially important whether the cultivar is superior. We have been studying the varieties for three years, and it should be mentioned that the weather conditions were different, so it is very difficult to say if the grain yield trends of the investigated varieties would persist for a longer period in these stress conditions. Seasonal challenges obligate more focus on stress-resistant cultivars in the North region as well [21,22]. A similar opinion is expressed by other researchers [23,30,31,34].

4.2. Field Pea Nutritional Value Responses to Cropping System and Variety Selection

Field pea seeds have high nutritional value concerning protein, starch, dietary fiber and micronutrients. Due to their high protein content and ability to fix nitrogen, legume crops have the potential to sustainably increase protein production, but given the diversity of environmental and soil conditions, it is necessary to grow legume species and varieties that are better adapted to local conditions. Grain yield could be compensated by good quality grains, and proteins are among the most important qualitative components.

Average protein concentrations in organic cropping systems from this study are similar to results of other researchers in other countries [30,31]. The protein content of the varieties in conventional cropping systems are also as stated by other researchers. Protein makes up around 15–30% of dry field pea seeds, more typically 20–28% within different varieties. Field pea seed protein composition is complex and is predominantly determined genetically [27]. In our study, the amount of protein accumulated by the field pea was reliably affected by cropping system. The amount of protein varied significantly between the varieties. It is common for varieties to differ in physiological characteristics, which are affected not only by genetic differences but also by other factors during plant growth. Protein content was affected by cultivation conditions. Heat and drought stress can interrupt seed maturation and may result in lower accumulation of those seed proteins that typically accumulate later in development [11,35]. However, the influence of management practices such as conventional and organic cropping systems can only be slightly related to protein content [35].

Field pea can serve as a suitable crude protein and amino acids source for different users. The variety can affect not only the total amount of protein but also the content of amino acids. In our study, some differences in the amounts of several selected amino acids suggest that variety is important. Researchers have reported differences in amino acid content between field pea varieties, which are influenced by specific cultivation locations and technologies [28].

5. Conclusions

This study revealed the good productivity potential of newly bred field pea varieties Lina DS, Egle DS, Jura DS, Ieva DS and their significantly different performance in conventional and organic cropping systems. It also highlighted differences in yield components and protein accumulation among these varieties, despite their good production. Organic cropping systems limited the grain yield of new field pea varieties compared with conventional; however, different varieties tended to respond differently to organic crop management. Newly bred variety Egle DS demonstrated the highest grain yields, and the highest contents of proteins and essential amino acids in the organic farming system.

The results indicate that the newest varieties have the potential to enhance the productivity and seed quality of field peas under the Nemoral climate zone, but unpredictable climatic conditions do not allow the expectation of yield stability yet, especially in the organic farming system. Consequently, it is relevant to develop breeding programs focusing on varieties intended for better yield stability in the organic farming system.