Supporting Crop and Different Row Spacing As Factors Influencing

agronomy

Article Supporting Crop and Diﬀerent Row Spacing as Factors Inﬂuencing Weed Infestation in Lentil Crop and Seed Yield under Organic Farming Conditions

Piotr Kraska 1 , Sylwia Andruszczak 1,*, Ewa Kwieci ´nska-Poppe 1, Mariola Staniak 2 , Krzysztof Ró˙zyło 1 and Hubert Rusecki 1

1 Department of Herbology and Plant Cultivation Techniques, University of Life Sciences, Akademicka 13, 20-950 Lublin, Poland; [email protected] (P.K.); [email protected] (E.K.-P.); [email protected] (K.R.); [email protected] (H.R.) 2 Department of Forage Crop Production, Institute of Soil Science and Plant Cultivation, State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland; [email protected] * Correspondence: [email protected]; Tel.: +48-81-445-66-89

Received: 20 November 2019; Accepted: 17 December 2019; Published: 19 December 2019

Abstract: A field study was conducted at the Certified Organic Farm in Poland over the period 2014–2016. This study evaluated weed infestation and seed yield of the lentil varieties ‘Tina’ and ‘Anita’, as well as of a mixture of these two varieties, sole cropped and row intercropped with naked oats as a supporting crop. Additionally, lentil was sown at a different row spacing of 20 and 25 cm. The lentil variety ‘Anita’ produced 25.3% higher yields than var. ‘Tina’. Weight of 1000 seed, number of pods per plant, and first pod height did not differ significantly in the treatments with the lentil varieties. The lentil seed yield obtained in the treatments with a supporting crop was lower by 9.4% compared with the sole cropped plots. In turn, the 1000 seed weight was 3.9% higher in the treatment where a supporting crop was used. The presence of oats as a supporting crop in lentil crop allowed crop competitiveness against weeds to be increased significantly, thus reducing their total number and dry weight by 5.3% and 30.5%, respectively. Sowing lentil at different row spacings did not have a significant effect on seed yield and weed infestation in crop. The greatest diversity of weed species was found in the treatments where the mixture of the lentil varieties was sown and in the treatment with the smaller row spacing. Intercropping of lentil with oats resulted in reduced occurrence of monocotyledonous weeds such as Echinochloa crus-galli and Elymus repens. The presence of oat as a supporting crop can effectively reduce the pressure from weeds without significantly reducing lentil cultivar yield in organic farming.

Keywords: Lens culinaris; weeds; row spacing; row intercropping; organic farming

1. Introduction The lentil (Lens culinaris Medic.) is one of the oldest cultivated legume crops. Due to its valuable chemical composition and health-promoting properties, it is a desirable element of an everyday diet. Lentil seeds contain from 24% to 32% of valuable protein and are also a rich source of phytoestrogens, folic acid, group B vitamins, and micronutrients [1–3]. Lentil can have a potential role in crop rotation, in particular in organic farms, allowing the biological equilibrium of agroecosystems and soil fertility to be maintained [4]. The special ability of leguminous plants to live in symbiosis with rhizobia that ﬁx free atmospheric nitrogen also needs to be stressed [5]. In spite of many beneﬁcial characteristics of lentil, the acreage of this crop in organic farms is quite low. The reason for this is likely due to its high susceptibility to lodging and low competitiveness against weeds [6,7].

Agronomy 2020, 10, 9; doi:10.3390/agronomy10010009 www.mdpi.com/journal/agronomy Agronomy 2020, 10, 9 2 of 13

One of the methods for protecting lentil against lodging can be its row intercropping with other crop species [8]. The presence of a low-growing inter-row crop that does not compete for light and occupies additional space can increase crop competitiveness and effectively reduce the pressure from fungal pathogens and weeds [8–12]. In mixed cropping systems, the increased proportion of companion crops (usually cereals) can suppress weeds without significantly reducing lentil yield [13,14]. The oat, which not only competes well with weeds but also has phytosanitary properties, is a species that is perfectly suitable for row intercropping with lentil [15]. Sowing mixtures of varieties can be an important element of organic cropping of lentil. Compared to sole cropping, this cultivation method can contribute to a better use of space in crop, reduce the spread of fungal pathogens, and increase yield stability when adverse conditions occur during the growing season [16]. In organic farming, in which herbicide application is prohibited, there is a constant need to seek new effective solutions for controlling the occurrence of weeds [17]. It seems that row intercropping, sowing different varieties that are adapted to soil and climatic conditions, and different crop densities can be an effective tool for reducing the occurrence of weeds, and thus for increasing yield effectiveness and seed quality of lentil and other legumes grown under organic farming conditions [5,18–20]. This study hypothesized that row intercropping of lentil with a supporting crop would effectively reduce crop lodging and, in consequence, improve the crop competitive ability against weeds. The supporting component would also provide benefits in the form of an additional oat grain yield. The aim of this study was to evaluate yield and weed infestation in lentil crop grown in pure stand and using a variety mixture (50% + 50%) as well as row intercropped with naked oats as a supporting crop at a row spacing of 20 and 25 cm, under an organic farming system.

2. Materials and Methods The field experiment was carried out in the years 2014–2016, at the Model Organic Farm in Chwałowice (Municipality of Ił˙za,Radom County, Masovian Voivodeship)belonging to the Agricultural Advisory Center in Brwinów, Radom Branch, Poland (51◦180N, 21◦300E). The experiment was set up on brown soil (CAMBISOLS according to the World Reference Base for Soil Resources 2014) [21], with an 1 organic carbon content of 14.11 g kg− and a pH of 6.15 in 1 M KCl. The soil was characterized by the 1 1 1 following nutrient content: P—73.9 mg kg− ; K—1430 mg kg− ; Mg—1765 mg kg− . The experiment was set up as a split-block design with three replicates. The area of a single plot was 8 m2. The scheme of the experiment included three factors: (i) lentil varieties ‘Tina’ and ‘Anita’, mixture of varieties: ‘Tina’ (50%) and ‘Anita’ (50%); (ii) row spacing: 20 cm, 25 cm; (iii) lentil cropping method: sole cropping (without a supporting crop), row intercropping with naked oats (Avena nuda L. var. ‘Polar’). The previous crop of lentil was a legume (Vicia sativa L.)/cereal mixture (Hordeum vulgare L.). Soil tillage, preparing the field for lentil, started with skimming and harrowing after harvesting the previous crop. Ploughing was done to an average depth before the winter. In the spring, harrowing 1 was performed, and before sowing, 15 t ha− of manure-based compost was applied and ploughed in. 1 1 Lentil seeds at a rate of 90 kg ha− and oat seeds at a rate of 50 kg ha− were sown in the second 10 days of April. Naked oats were sown separately in the interrows of the lentil crop (Figure1). Sowing was carried out using self-propelled plot drill Øyjord Wintersteiger (Austria). Evaluation of weed infestation in lentil crop was performed during the flowering period of lentil using the quantitative-gravimetric method. Analysis consisted in determining the number, species composition, and dry weight of weeds on sample areas determined in four randomly selected places in each plot delineated by a 1 0.25 m quadrat frame. × Before harvest, plants of lentil and oat were cut by hand from 2 m2 sampling areas in each plot to calculate the plant density. In addition, average lower pod setting height in lentil plants and number of pods from single lentil plant were determined. Collected samples were threshed using laboratory thresher Wintersteiger LD 180 and the seed yield obtained was calculated on a per-hectare basis. The Agronomy 2019, 9, x FOR PEER REVIEW 3 of 13

basis. The weight of 1000 seeds was determined on the basis of seed samples collected from each plot. AgronomyThe remaining2020, 10, 9plants were harvested using a Winterstiger combine. 3 of 13 The dates presented are the mean values from the years 2014–2016. The results were statistically analyzedAgronomy 2019 with, 9, thex FOR use PEER of theREVIEW analysis of variance using Statistica PL 13.3 (TIBCO Software Inc.,3 ofTulsa, 13 weightOK, USA). of 1000Tukey’s seeds multiple was determined comparison on test the was basis used of to seed compare samples differences collected between from each the plot.means The for remainingmainbasis. factorsThe weight plants (cultivars: wereof 1000 harvested C,seeds row was spacing: using determined a Winterstiger RS, lentilon the croppingbasis combine. of seed method: samples LCM), collected whereas from eachconfidence plot. intervalsThe Theremaining datesfor the presentedplants means were of are harveLSD the meansted(p = us0.05) valuesing awere Winterstiger from used the yearsto combine.compare 2014–2016. the Themeans results from were the statisticallysubclasses The dates presented are the mean values from the years 2014–2016. The results were statistically analyzed(interaction with C × the RS, use C × of LCM, the analysis RS × LCM). of variance using Statistica PL 13.3 (TIBCO Software Inc., Tulsa, OK,analyz USA).ed with Tukey’s the use multiple of the comparison analysis of test variance was used using to Statistica compare PL di ﬀ 13.erences3 (TIBCO between Software the meansInc., forTulsa, main OK, factors U (cultivars: C, row spacing: RS, lentil cropping method: LCM), whereas conﬁdence intervals for the means of LSD (p = 0.05) were used to compare the means from the subclasses (interaction C RS, C LCM, RS LCM). × × ×

Figure 1. Canopy of lentil cultivated with naked oat as a supporting crop.

Weather Conditions Throughout the experiment period, weather conditions varied substantially between the years. Figure 1. CanopyCanopy of of lentil lentil cultivated cultivated with with naked naked oat oat as as a asupporting supporting crop. crop. The highest amount of rainfall was recorded in 2014, in particular in May and July (Figure 2a). From WeatherAprilWeather to ConditionsConditionsAugust, the total rainfall was higher than the long-term average by 46%. The average air temperature in this vegetative season exceeded the long-term average by 1.6 °C (Figure 2b). ThroughoutThroughout the experiment period, period, weather weather condit conditionsions varied varied substantially substantially between between the the years. years. In 2015, the air temperature was at a similar level as in the first year of the study, but the amount TheThe highesthighest amountamount of rainfall was recorded recorded in in 2014, 2014, in in particular particular in in May May and and July July (Figure (Figure 2a).2a). From From of rainfall was on average lower by 40%. During June, July, and August the total rainfall was only AprilApril toto August,August, thethe totaltotal rainfall was higher th thanan the the long-term long-term average average by by 46%. 46%. The The average average air air 60%, 39%, and 19% of the long-term average, respectively. temperaturetemperature inin thisthis vegetativevegetative season exceeded exceeded the the long-term long-term average average by by 1.6 1.6 °CC (Figure (Figure 2b).2b). The year 2016, in turn, was the warmest and at the same time driest because◦ in this year the air InIn 2015,2015, thethe air temperature was was at at a a similar similar level level as as in in the the first ﬁrst year year of of the the study, study, but but the the amount amount temperature was higher by about 6 °C compared with 2014 and 2015, whereas the total rainfall was ofof rainfallrainfall was was on on average average lower lower by by 40%. 40%. During During June, June, July, July, and and August August the the total total rainfall rainfall was was only only 60%,

39%,60%, and39%, 19% and of 19% the of long-term the long-term average, average, respectively. respectively. The year 2016, in turn, was the warmest and at the same time driest because in this year the air temperature was higher by about 6 °C compared with 2014 and 2015, whereas the total rainfall was 2014 2015 2016 Mean for 1974-2010 lower by 67% and 45%,(a) respectively. In every month of this year, total rainfall was lower compared with long-term average from 27% (May) to 67% (July). 160 140 120 100 2014 2015 2016 Mean for 1974-2010 (a)80 16060 Rainfall (mm) 14040 12020 1000 80 IV V VI VII VIII 60 Figure 2. Cont. Rainfall (mm) 40 20 0 IV V VI VII VIII Agronomy 2020, 10, 9 4 of 13 Agronomy 2019, 9, x FOR PEER REVIEW 4 of 13

2014 2015 (b) 2016 Mean for 1974-2010 35 30 25 C) o 20 15 10

Temperature ( 5 0 IV V VI VII VIII Figure 2. Rainfall (a) and temperature (b) in the vegetation seasons of the years 2014–2016 according to Figurethe Meteorological 2. Rainfall (a Station) and temperature at Model Organic (b) in the Farm vegetation in Chwałowice. seasons of the years 2014–2016 according to the Meteorological Station at Model Organic Farm in Chwałowice. The year 2016, in turn, was the warmest and at the same time driest because in this year the air 3.temperature Results and was Discussion higher by about 6 ◦C compared with 2014 and 2015, whereas the total rainfall was lower by 67% and 45%, respectively. In every month of this year, total rainfall was lower compared The results of the study showed no significant interaction between the experimental factors with with long-term average from 27% (May) to 67% (July). respect to number of monocotyledonous weeds, weight of 1000 seeds, average lower pod setting 2 height3. Results in lentil and plants, Discussion number of pods from single plant, and number of lentil plants per 1 m (Table 1), and therefore this paper presents the relationships of the traits studied with the main effects. The results of the study showed no significant interaction between the experimental factors with respectTable to number1. Effect of of monocotyledonous cultivar, row spacing, weeds, lentil weight cropping of 1000method, seeds, and average interaction lower of podexperimental setting height in lentilfactors plants, on examined number features. of pods from single plant, and number of lentil plants per 1 m2 (Table1), and therefore this paper presents the relationships of the traits studied with the main effects. Feature C RS LCM C × RS C × LCM RS × LCM TableNumber 1. Effect of of dicotyledonous cultivar, row spacing, weeds lentil cropping method,** ns and ns interaction ns of experimental ** factors ns onNumber examined of features.monocotyledonous weeds ** ns ** ns ns ns Total number of weeds ** ns ns ns ns ** Feature C RS LCM C RS C LCM RS LCM Air-dry weight of weeds ** ns ** × ns × ** × ns NumberWeight of dicotyledonousof 1000 seeds of weeds lentil **ns ns ns ns** nsns **ns nsns Number of monocotyledonous weeds ** ns ** ns ns ns Average lower pod setting height in lentil plants ns ns ns ns ns ns Total number of weeds ** ns ns ns ns ** NumberAir-dry of pods weight from of single weeds lentil plant ** ns ns ** ** ns ns ns ** ns ns ns NumberWeight of of 1000 lentil seeds plants of lentil per 1 m2 ns ns ns ** ** ** ns ns ns ns ns ns Average lower podLentil setting seed height yield in lentil plants ns ** ns ns ns ** ns ** ns ns ns ** Number of pods from single lentil plant ns ** ns ns ns ns C: cultivar; RS: row spacing; LCM: lentil cropping method; ns: no significant difference between Number of lentil plants per 1 m2 ns ** ** ns ns ns treatments atLentil p ≤ 0.05; seed ** yield significant difference between ** nstreatments ** at p ≤ 0.05. ** ns ** C: cultivar; RS: row spacing; LCM: lentil cropping method; ns: no significant difference between treatments at Thep 0.05; presence ** significant of weeds difference in lentil between crop treatments results at inp a0.05. substantial loss in seed yield [22,23]. Moreover, ≤ ≤ lentil is a species that poorly competes with weeds [24]. The weed species composition in lentil crop grownThe in presencepure stand of and weeds in inmixed lentil variety crop results stand inwa as substantialsimilar (Table loss 2). in Independent seed yield [22 on,23 row]. Moreover, spacing andlentil lentil is a speciescropping that method, poorly the competes highest withnumber weeds of species [24]. The (48) weed was speciesfound in composition the treatment in lentilwhere crop the mixturegrown in of pure the lentil stand varieties and in mixed was sown, variety whereas stand was their similar lowest (Table number2). Independent was found in on the row plots spacing with var.and ‘Tina’ lentil cropping(44). In all method, experimental the highest treatments, number the of dominant species (48) weed was species found were in the Echinochloa treatment wherecrus-galli, the Galinsogamixture of parviflora, the lentil Sonchus varieties arvensis was sown,, and Chenopodium whereas their album lowest. Furthermore, number was Elymus found repens in the was plots found with tovar. occur ‘Tina’ in (44).quite In large all experimentalnumbers in the treatments, var. ‘Tina’ the crop. dominant Nevertheless, weed species a large were majorityEchinochloa of taxa occurred crus-galli, sporadicallyGalinsoga parviflora, and their Sonchus impact arvensis on weed, and Chenopodiuminfestation was album small.. Furthermore, ComparedElymus to the repensresultswas obtained found in to thisoccur experiment, in quite large in a numbersstudy by inLejman the var. et al. ‘Tina’ [25], crop. a mixture Nevertheless, of barley awith large field majority pea was of taxacharacterized occurred bysporadically low variation and theirin weed impact species on weed composition infestation because was small. only Compared11 taxa were to theidentified results obtainedin the crop. in this In turn,experiment, Staniak inet aal. study [26] found by Lejman that weed et al. species [25], a mixturerichness ofwas barley independent with field of peathe mixture was characterized composition, by withlow variationthe number in weedof weed species species composition ranging between because 25 only and 11 32. taxa were identified in the crop. In turn, Different row spacing had a small effect on the weed species composition in lentil crop. Regardless of the cultivar and lentil cropping method, over the 3 year study period, 51 weed species

Agronomy 2020, 10, 9 5 of 13

Staniak et al. [26] found that weed species richness was independent of the mixture composition, with the number of weed species ranging between 25 and 32. Different row spacing had a small effect on the weed species composition in lentil crop. Regardless of the cultivar and lentil cropping method, over the 3 year study period, 51 weed species were found to occur in the plots with a row spacing of 20 cm, whereas 5 species fewer were recorded in the treatment with a row spacing of 25 cm (Table3). The wider row spacing contributed to significant reduction in the numbers of the dominant species, that is, G. parviflora (on average by 36% compared to a spacing of 20 cm), but the density of Thlaspi arvense significantly increased. Compared to the sole cropping of lentil, row intercropping of lentil with oats as a supporting crop caused a decrease in the number of dicotyledonous weed species (from 43 to 39), but the number of monocotyledonous taxa increased (from 6 to 9) (Table4). On both experimental treatments, independent of cultivar and row spacing, S. arvensis, G. parviflora, and Ch. album were weeds that occurred in greatest number, whereas among monocotyledonous weeds these were E. crus-galli and E. repens. Likewise, in the study by Lejman et al. [25] E. crus-galli was the most numerous from the group of monocotyledonous species in a mixture of barley with pea. Bojarszczuk et al. [27], and Staniak et al. [26] found that mostly dicotyledonous weeds, such as Ch. album, Stellaria media, Capsella bursa-pastoris, and G. parviflora, were dominant in cereal–legume mixtures. In this study, the presence of oats as a supporting crop in lentil cultivation resulted in a significant reduction in the numbers of T. arvense and E. repens (respectively by 65% and 39%), but at the same time the density of G. parviflora significantly increased by 56%.

2 Table 2. Species composition and number of weeds (plants m− ) in the crops of lentil depending on lentil cultivars (mean for 2014–2016; independent on row spacing and lentil cropping method).

Cultivars Weeds Tina Anita Tina + Anita Dicotyledonous Galinsoga parviflora Cav. 21.4 ab 15.5 a 25.7 b Sonchus arvensis L. 17.7 a 17.9 a 15.5 a Chenopodium album L. 17.3 a 15.1 a 18.1 a Stellaria media (L.) Vill. 13.0 a 9.3 ab 4.9 b Matricaria maritima subsp. inodora (L.) Dostál 12.4 a 8.8 a 9.3 a Thlaspi arvense L. 10.2 a 6.4 a 8.5 a Plantago major L. 7.5 a 7.5 a 9.3 a Capsella bursa-pastoris (L.) Medik. 6.6 a 3.1 b 3.9 b Others 29.4 23.4 25.0 Number of species 37 40 41 Monocotyledonous 1 Echinochloa crus-galli (L.) Beauv. 49.1 a 31.6 b 34.8 b Elymus repens (L.) Gould. 17.7 a 9.4 b 13.8 ab Others 6.6 1.1 7.0 Number of species 7 7 7 1 With Equisetum arvense L. Different letters indicate significant difference at p 0.05. ≤

2 Table 3. Species composition and number of weeds (plants m− ) in the crops of lentil depending on row spacing (mean for 2014–2016; independent on cultivar and lentil cropping method).

Row Spacing Weeds 20 cm 25 cm Dicotyledonous Galinsoga parviﬂora Cav. 25.4 a 16.3 b Chenopodium album L. 16.8 a 16.9 a Sonchus arvensis L. 16.6 a 17.5 a Stellaria media (L.) Vill. 10.9 a 7.2 a Agronomy 2020, 10, 9 6 of 13

Table 3. Cont.

Row Spacing Weeds 20 cm 25 cm Matricaria maritima subsp. inodora (L.) Dostál 10.3 a 10.0 a Plantago major L. 5.6 a 10.5 a Thlaspi arvense L. 5.2 a 11.6 b Capsella bursa-pastoris (L.) Medik. 4.6 a 4.4 a Others 27.0 25.0 Number of species 43 39 Monocotyledonous 1 Echinochloa crus-galli (L.) Beauv. 35.6 a 41.4 a Elymus repens (L.) Gould. 15.9 a 11.4 a Others 5.3 4.4 Number of species 8 7 1 With Equisetum arvense L. Different letters indicate significant difference at p 0.05. ≤ In the var. ‘Anita’ crop, independent of row spacing and lentil cropping method, a significantly lower number of dicotyledonous, monocotyledonous, and total weeds was determined compared with the plots with var. ‘Tina’ (Figure3a–c). At the same time, the total number of weeds in the var. ‘Tina’ crop was significantly higher than in the treatment with the varietal mixture. An opposite relationship was found in the case of weed dry weight (Figure3d). The presence of oats as an intercropped crop in lentil crop, regardless of lentil cultivar and row spacing, did not have a significant impact on number of dicotyledonous weeds and total weeds. Compared to lentil grown in pure stand, on the other hand, a significant decrease was found in the number of monocotyledonous weeds (by 22.4%) and weed dry weight (by 30.5%).

2 Table 4. Species composition and number of weeds (plants m− ) in the crops of lentil depending on lentil cropping method (mean for 2014–2016; independent on cultivar and row spacing).

Lentil Cropping Method Weeds SC RI Dicotyledonous Sonchus arvensis L. 17.5 a 16.6 a Galinsoga parviflora Cav. 16.3 a 25.5 b Chenopodium album L. 15.9 a 17.7 a Thlaspi arvense L. 12.4 a 4.3 b Matricaria maritima subsp. inodora (L.) Dostál 10.2 a 10.1 a Stellaria media (L.) Vill. 8.2 a 9.9 a Plantago major L. 7.4 a 8.8 a Capsella bursa-pastoris (L.) Medik. 4.9 a 4.1 a Others 25.7 26.3 Number of species 43 39 Monocotyledonous 1 Echinochloa crus-galli (L.) Beauv. 43.5 a 33.4 a Elymus repens (L.) Gould. 17.0 a 10.3 b Others 3.7 6.1 Number of species 6 9 1 With Equisetum arvense L. SC: sole cropping of lentil without a supporting plant, RI: row intercropping of lentil with naked oat. Different letters indicate significant difference at p 0.05. ≤

Statistical analysis conﬁrmed the signiﬁcant interaction between cultivars and lentil cropping method. Var. ‘Anita’, both cropped with and without oats, was the most competitive against Agronomy 2020, 10, 9 7 of 13

AgronomyAgronomy 2019 2019, ,9 9, ,x x FOR FOR PEER PEER REVIEW REVIEW 77 of of 13 13 dicotyledonous weeds (Figure4). However, the lowest air dry mass of weeds was found in the var. ‘Tina’ intercroppedElymusElymus withrepens repens oats (L.) (L.) (Figure Gould. Gould.5). The presence of oats 17.0 17.0 as aa a supporting crop significantly 10.3 10.3 b b reduced the air dry mass ofOthers weedsOthers in the var. ‘Tina’ and mixture 3.7 3.7 of ‘Tina’ and ‘Anita’ crops. 6.1 6.1 This study demonstrated thatNumberNumber row intercroppingof of species species of lentil with naked oats 6 6 significantly decreased the 9 9 total number of weeds in the treatment with the row spacing of 25 cm but had no significant effect in the narrower 11 WithWith EquisetumEquisetum arvensearvense L.L. SC:SC: solesole croppingcropping ofof lentillentil withoutwithout aa supportingsupporting plant,plant, RI:RI: rowrow rowintercropping spacingintercropping (20 cm) of of lentil lentil (Figure with with6 ).naked naked oat. oat. Different Different letters letters indicate indicate significant significant difference difference at at p p ≤ ≤ 0.05. 0.05.

a)(a)NumberNumber of of dicotyledonous dicotyledonous weeds weeds b)(b)NumberNumber of of monocotyledonous monocotyledonous weeds weeds aa a abab aa aa aa aa a 140140 bb 8080 aa 120 bb aa aa 120 bb 100100 6060 bb 8080 4040 6060 4040 2020 2020 00 00 TAT+A20TAT+A202525 SCSC RI RI TAT+A20TAT+A202525 SCSC RI RI cmcm cmcm cmcm cmcm

c)(c)TotalTotal number number of of weeds weeds d)(d)DryDry mass mass of of weeds weeds (g (g m m -2 )-2) b aa 250250 aa b a a 250250 aa abab a aa cc aa aa a aa b 200200 bb 200200 b 150150 150150 100100 100100 5050 5050 00 00 TAT+A20TAT+A202525 SCSC RI RI TAT+A20TAT+A202525 SCSC RI RI cmcm cmcm cmcm cmcm CultivarCultivar RowRow spacing spacing LentilLentil cropping cropping CultivarCultivar RowRow spacing spacing LentilLentil cropping cropping methodmethod methodmethod FigureFigure 3. 3.3. TheThe number number of of dicotyledonous dicotyledonousdicotyledonous weeds weeds ( (aaa))),, , monocotyledonousmonocotyledonousmonocotyledonous weeds weeds ( (bb),),), total totaltotal number numbernumber of ofof weedsweedsweeds ( ((ccc),),), and andand dry drydry mass massmass of ofof weeds weedsweeds ( ((ddd))) in inin lentil lentillentil crop cropcrop as asas influenced influencedinfluenced by byby cultivar, cultivar,cultivar, row rowrow spacing, spacing,spacing, and andand lentil lentillentil croppingcroppingcropping method methodmethod (mean (mean(mean for forfor 2014–2016). 2014–2016).2014–2016). Different DiDifferentfferent letters letters indicate indicate significant significantsignificant difference didifferencefference at atat p pp ≤ ≤ 0.05. 0.05. T: T: ≤ var.var.var. ‘Tina’,‘Tina’,‘Tina’, A: A:A: var. var.var. ‘Anita’, ‘Anita’,‘Anita’, SC: soleSC:SC: croppingsolesole croppingcropping of lentil ofof without lentillentil awithoutwithout supporting aa supportingsupporting plant, RI: row plant,plant, intercropping RI:RI: rowrow intercroppingofintercropping lentil with nakedof of lentil lentil oat. with with naked naked oat. oat.

SCSC - - sole sole cropping cropping of of lentil lentil without without a a supporting supporting crop crop RIRI - - row row intercropping intercropping o off lentil lentil with with naked naked oat oat bb abab a abab ab 150150 a aa ab 100100 5050 00 TinaTina Anita Anita Tina Tina + + Anita Anita

FigureFigure 4.4.4. The TheThe interaction interactioninteraction eff ect effecteffect of cultivar ofof cultivarcultivar and lentil andand cropping lelentilntil methodcroppingcropping on method themethod number onon of thethe dicotyledonous numbernumber ofof 2 −−22 dicotyledonousweedsdicotyledonous in lentil cropweeds weeds (plant in in lentil lentil m− )crop crop (mean (plant (plant for 2014–2016;m m )) (mean (mean independent for for 2014–2016; 2014–2016; on independent rowindependent spacing). on on Di row rowfferent spacing). spacing). letters DifferentindicateDifferent significant lettersletters indicateindicate difference significantsignificant at p 0.05. differencedifference SC: sole atat cropping pp ≤≤ 0.05.0.05.of SC:SC: lentil solesole without croppingcropping a supporting ofof lentillentil without plant,without RI aa – ≤ supportingrowsupporting intercropping plant, plant, RI RI of – – lentil row row intercropping withintercropping naked oat. of of lentil lentil with with naked naked oat. oat.

As far as weed infestation reduction is concerned, mixed crops, in comparison to monovarietal crops, have a better adaptive ability as well as making better use of space and habitat resources and, in eﬀect, reducing the pool of these resources for weeds [19]. In agricultural practice, legume–cereal

Agronomy 2020, 10, 9 8 of 13

mixtures or cereal mixtures are grown most frequently. Due to the morphological diﬀerentiation of individual components, higher weed control ability is attributed to mixtures that include legumes [28,29]. However, Boyd and Brennan [30] drew attention to high weed infestation of legume–cereal mixtures,

AgronomywhichAgronomy are 20192019 quite,, 99,, xx FOR frequentlyFOR PEERPEER REVIEWREVIEW grown in organic farms. 88 ofof 1313

SCSC -- solesole croppingcropping ofof lentillentil withoutwithout aa supportingsupporting cropcrop RIRI -- rowrow intercroppingintercropping ooff lentillentil withwith nakednaked oatoat

cc cc 300300 bcbc abab abab a 200200 a 100100 00 TinaTina Anita Anita Tina Tina ++ AnitaAnita

FigureFigure 5.5. TheTheThe interactioninteraction interaction effecteffect effect ofof cultivarcultivar andand lentillentil crcr croppingoppingopping methodmethod onon thethe airair drydry weightweight ofof weedsweeds −−22 inin lentil lentil crop crop (g (g mm−)) ) (mean(mean (mean forfor for 2014–2016;2014–2016; independentindependent onon row row sp spacing).spacing).acing). DifferentDifferent Different letters letters indicate indicate significantsignificantsignificant differencedifference difference at at pp ≤≤ 0.05.0.05. SC:SC: SC: solesole sole croppingcropping cropping ofof of lentillentil lentil withoutwithout without aa a supportingsupporting plant,plant, RI:RI: RI: rowrow ≤ intercroppingintercropping of of lentil lentil with with naked naked oat. oat.oat.

SCSC -- solesole croppingcropping ofof lentillentil withoutwithout aa supportingsupporting cropcrop RIRI -- rowrow intercroppingintercropping ooff lentillentil withwith nakednaked oatoat

300300 bcbc cc abab aa 200200 100100 00 2020 cmcm 25 25 cmcm

FigureFigure 6. 6. TheTheThe interactioninteraction interaction effecteffect effect ofof of rowrow spacingspacing andand lentlent lentililil croppingcropping methodmethod onon thethe totaltotal numbernumber ofof −−22 weedsweeds in in lentil lentil cropcrop (plant(plant mmm− )) (mean (mean for forfor 2014–2016; 2014–2016; independent independent on on cultivar).cultivar). DifferentDifferent Different letters letters indicateindicate significant significantsignificant didifferencedifferencefferenceat atatp pp ≤≤0.05. 0.05.0.05. SC: SC:SC: sole solesole cropping croppingcropping of ofof lentil lentlent withoutilil withoutwithout a supporting aa supportingsupporting plant, plant,plant, RI: row RI:RI: ≤ rowrowintercropping intercroppingintercropping of lentil ofof lentillentil with withwith naked nakednaked oat. oat.oat.

TheThe statisticalstatistical analysisanalysis diddid notnot confirmconfirm confirm thethe lentillentil varietiesvarieties toto havehave aa significantsignificant significant effecteffect effect onon traits traits suchsuch asas 10001000 seedseed weight,weight, firstfirst first popo poddd height, height, numbernumber number ofof of podspods pods perper per planplan plant,t,t, andand and plantplant plant densitydensity density (Table(Table (Table 5).55).). Lopez-BellidoLopez-Bellido etet et al.al. al. [9][9] [9 ] foundfound found thatthat that numbernumber number ofof of podspods pods perper per plantplant plant isis isinverselyinversely inversely correlatedcorrelated correlated withwith with numbernumber number ofof plantsplantsof plants perper per unitunit unit area.area. area. ThisThis This isis confirmed isconfirmed confirmed byby by thethe the presentpresent present study,study, study, whichwhich which showedshowed showed thatthat that plantsplants plants sownsown inin narrowernarrower rows rows producedproduced significantlysignificantlysignificantly more moremore pods, pods,pods, but butbut the thethe lentil lentillentil density densitydensity was waswas found foundfound to toto be bebe much muchmuch higher higherhigher in ininthe thethe treatment treatmenttreatment with withwith a row aa rowrow spacing spacingspacing of 25 ofof cm2525 cmcm (Table (Table(Table6). Many 6).6). ManyMany authors authorsauthors are ofareare the ofof opinion thethe opinionopinion that that thethat factor thethe factorfactor that thatthatdetermines determinesdetermines the yield thethe ofyieldyieldFabaceae ofof FabaceaeFabaceaecrops is cropscrops ensuring isis ensuringensuring optimal crop optimaloptimal architecture crcropop architecturearchitecture [31–33]. An [31–33].[31–33]. appropriate AnAn appropriateappropriatedensity of plants densitydensity per ofof unit plantsplants area perper determines unitunit areaarea their deterdeter properminesmines growth theirtheir properproper and development growthgrowth andand anddevelopmentdevelopment is a guarantee andand is inis aaobtaining guaranteeguarantee a highinin obtainingobtaining seed yield aa highhigh [34, 35 seedseed]. yieldyield [34,35].[34,35]. In this study, row intercropping of lentil with oats as a supporting crop beneficially affected thousandTableTable seed5.5. SomeSome weight morphologicalmorphological of lentil (Table featuresfeatures7). ofof Compared lentillentil plantsplants to dependingdepending sole cropping, onon lentillentil a significant cultivarcultivar (mean(mean decrease forfor 2014–2014– in plant density2016;2016; was independentindependent however foundonon rowrow (on spacingspacing average andand lentilbylentil 13.2%). croppingcropping As method). amethod). result, the seed yield of lentil grown with oats was significantly lower (on average by 9.4%) than in the treatment without a supporting crop (Figure7). CultivarCultivar Ciftci and Ülker [36] revealedFeatureFeature a similar relationship when in their research lentil was intercropped TinaTina Anita Anita Tina Tina ++ AnitaAnita with spring cereals. This could have resulted from the competitive effects of oats on lentil plants. WeightWeight ofof 10001000 seedsseeds ofof lentlentilil (g)(g) 30.1 30.1 aa 31.6 31.6 aa 31.6 31.6 aa AverageAverage lowerlower podpod settingsetting heightheight inin lentillentil plantsplants (cm)(cm) 29.4 29.4 aa 27.9 27.9 aa 28.7 28.7 aa NumberNumber ofof podspods fromfrom singlesingle lentlentilil plantplant 23.0 23.0 aa 22.7 22.7 aa 25.4 25.4 aa NumberNumber ofof lentillentil plantsplants perper 11 mm22 201.1 201.1 aa 230.4 230.4 aa 207.6 207.6 aa DifferentDifferent lettersletters indicateindicate significantsignificant differencedifference atat pp ≤≤ 0.05.0.05.

Agronomy 2019, 9, x FOR PEER REVIEW 9 of 13

Table 6. Some morphological features of lentil plants depending on row spacing (mean for 2014–2016; independent on cultivar and lentil cropping method).

Row Spacing Feature 20 cm 25 cm Weight of 1000 seeds of lentil (g) 31.1 a 31.0 a Average lower pod setting height in lentil plants (cm) 28.9 a 28.4 a Agronomy 2020, 10, 9 Number of pods from single lentil plant 25.1 a 22.3 b 9 of 13 Number of lentil plants per 1 m2 196.5 a 229.6 b Table 5. Some morphologicalDifferent features letters ofindicate lentil plants significant depending difference on lentil at p cultivar≤ 0.05. (mean for 2014–2016; independent on row spacing and lentil cropping method). In this study, row intercropping of lentil with oats as a supporting crop beneficially affected Cultivar thousand seed weight of lentilFeature (Table 7). Compared to sole cropping, a significant decrease in plant density was however found (on average by 13.2%). As a result,Tina the Anitaseed yield Tinaof lentil+ Anita grown with oats was significantlyWeight lower of 1000 (on seeds average of lentil by (g) 9.4%) than in 30.1the atreatment 31.6 awithout a 31.6 supporting a crop (Figure Average7). Ciftci lower and pod Ülker setting [36] height revealed in lentil a plantssimilar (cm) relationship29.4 a when 27.9 in a their research 28.7 a lentil was intercroppedNumber with spring of pods cereals. from single This lentilcould plant have resulted 23.0 from a the 22.7 competitive a 25.4effects a of oats on 2 201.1 a 230.4 a 207.6 a lentil plants. Number of lentil plants per 1 m Different letters indicate significant difference at p 0.05. Significant differences in seed yield of lentil cultivars were demon≤ strated (Figure 7). The variety ‘Anita’ produced the highest yields (11.63 dt ha−1), whereas var. ‘Tina’ and the variety mixture Table 6. Some morphological features of lentil plants depending on row spacing (mean for 2014–2016; produced significantly lower seed yields, by 20.2% and 13.1%, respectively. In the opinion of independent on cultivar and lentil cropping method). Vlachostergios and Roupakias [5] there are large possibilities to increase seed yield of lentil grown under organic farming conditions through appropriate variety selection.Row Spacing Feature In the present study, the lentil seed yield in the treatments with20 cmdifferent 25 row cm spacings did not differ significantly, though in the case of a row spacing of 25 cm it was slightly higher (by 6.1%) than Weight of 1000 seeds of lentil (g) 31.1 a 31.0 a in the plots whereAverage lentillower was sown pod setting at a spacing height in of lentil 20 plantscm. In (cm) a study28.9 by aOuji et 28.4 al. [35], a lentil sown at a row spacing of 34 cmNumber produced of pods a from38% singlehigher lentil yield plant compared to 25.1 a aspacing 22.3 of b 17 cm. Bicer [31] believes that increased lentilNumber crop of density lentil plants results per in 1 mgreater2 competition196.5 abetween 229.6 plants b and leads to a weakening of individual plants.Different letters indicate significant difference at p 0.05. ≤

Table 7.7. Some morphological features of lentil plants depending on lentil cropping method (mean for 2014–2016; independent on cultivarcultivar andand rowrow spacing).spacing).

Lentil CroppingLentil Cropping Method Method FeatureFeature SCSC RI RI Weight of 1000 seeds of lentil (g) 30.5 a 31.7 b Weight of 1000 seeds of lentil (g) 30.5 a 31.7 b AverageAverage lower lowerpod setting pod setting height height in lentil in lentil plants plants (cm) (cm) 28.1 a 28.1 a 29.3 a 29.3 a NumberNumber of pods of podsfrom fromsingle single lentil lentil plant plant 23.9 a 23.9 a 23.5 a 23.5 a NumberNumber of lentil of lentil plants plants per per1 m 12 m 2 228.1 a 228.1 a 198.0 b 198.0 b DiDifferentfferent letters letters indicate indicate significant significant difference difference at p 0.05. at SC: p sole≤ 0.05. cropping SC: sole of lentil cropping without aof supporting lentil without plant,RI: a ≤ rowsupporting intercropping plant, of RI: lentil row with intercropping naked oat. of lentil with naked oat.

15 b a a ac c a b 10

0 TAT+A2025 SC RI cm cm Lentil cropping Cultivar Row spacing method

Figure 7. The seed yield of lentil as influenced by cultivar, row spacing, and lentil cropping method (mean for 2014–2016). Different letters indicate significant difference at p 0.05. T: var. ‘Tina’, A: var. ≤ ‘Anita’, SC: sole cropping of lentil without a supporting plant, RI: row intercropping of lentil with naked oat.

Significant differences in seed yield of lentil cultivars were demonstrated (Figure7). The variety 1 ‘Anita’ produced the highest yields (11.63 dt ha− ), whereas var. ‘Tina’ and the variety mixture produced significantly lower seed yields, by 20.2% and 13.1%, respectively. In the opinion of Vlachostergios and Agronomy 2020, 10, 9 10 of 13

Roupakias [5] there are large possibilities to increase seed yield of lentil grown under organic farming conditionsAgronomy 2019 through, 9, x FORappropriate PEER REVIEW variety selection. 10 of 13 AgronomyIn the2019 present, 9, x FOR study,PEER REVIEW the lentil seed yield in the treatments with different row spacings did10 of not 13 differFigure significantly, 7. The seed though yield in of the lentil case as ofinfluenced a row spacing by cultivar, of 25 row cm itspacing, was slightly and lentil higher cropping (by 6.1%) method than in Figure 7. The seed yield of lentil as influenced by cultivar, row spacing, and lentil cropping method the plots(mean where for 2014–2016). lentil was Different sown at aletters spacing indicate of 20 significant cm. In a studydifference by Ouji at p ≤ et 0.05. al.[ T:35 var.], lentil ‘Tina’, sown A: var. at a row (mean for 2014–2016). Different letters indicate significant difference at p ≤ 0.05. T: var. ‘Tina’, A: var. spacing‘Anita’, of 34 SC: cm sole produced cropping a 38%of lentil higher without yield a comparedsupporting to plant, a spacing RI: row of intercropping 17 cm. Bicer [of31 lentil] believes with that ‘Anita’, SC: sole cropping of lentil without a supporting plant, RI: row intercropping of lentil with increasednaked lentil oat. crop density results in greater competition between plants and leads to a weakening of naked oat. individual plants. The effect of row spacing on lentil yield was dependent on the variety. A significant increase in The effect of row spacing on lentil yield was dependent on the variety. A significant increase in seedThe yield effect as affected of row spacingby the wider on lentil row yield spacing was wadepes onlyndent found on the in variety.the treatment A significant where increasethe variety in seed yield as affected by the wider row spacing was only found in the treatment where the variety seedmixture yield was as sownaffected (on by average the wider by 25.7%), row spacing whereas wa sthe only individual found in varieties the treatment gave similar where yieldsthe variety as in mixture was sown (on average by 25.7%), whereas the individual varieties gave similar yields as in the mixturethe treatment was sown with (ona spacing average of by20 25.7%),cm (Figure whereas 8). the individual varieties gave similar yields as in thetreatment treatment with with a spacing a spacing of 20 of cm 20 (Figurecm (Figure8). 8).

20 cm 25 cm 20 cm 25 cm

15 c c bc 15 abc c c bc abc ab a 10 ab a 10 5 5 0 0 Tina Anita Tina + Anita Tina Anita Tina + Anita

Figure 8. The interaction effect of cultivar and raw spacing on seed yield of lentil crop (dt ha−1) (mean Figure 8. The interaction effect of cultivar and raw spacing on seed yield of lentil crop (dt ha−1) (mean Figurefor 2014–2016; 8. Theinteraction independent eff ecton lentil of cultivar cropping and method). raw spacing Different on seed letters yield indicate of lentil significant crop (dt ha difference− ) (mean forforat p 2014–2016; 2014–2016; ≤ 0.05. independent independent on on lentil lentil cropping cropping method). method). Different Different letters letters indicate indicate significant significant difference difference atat pp ≤ 0.05.0.05. ≤ Statistical analysis showed that in the case of wider rows (25 cm) the presence of oats as a supportingStatisticalStatistical crop analysisanalysis caused showed showed significant that that in decrease thein the case case of in wider ofseed wider rows yield (25rows of cm) lentil(25 the cm) presence(by the 28.5% presence of oatscompared as aof supporting oats to assole a supportingcropcropping) caused (Figure crop significant caused 9). In decrease the significant treatment in seed decrease with yield narrower of in lentil seed row (by yield 28.5%spacing of compared lentil (20 cm), (by torow 28.5% sole intercropping cropping) compared (Figure ofto lentilsole9). cropping)Inwith the oats treatment (Figurepositively with 9). In narrowerinfluenced the treatment row the spacing withlentil narrower seed (20 cm), yield, row row spacingbut intercropping the (20determined cm), of row lentil intercroppingdifferences with oats positivelywere of lentil not withinfluencedconfirmed oats positivelystatistically. the lentil seedinfluenced yield, but the the lentil determined seed yield, differences but the were determined not confirmed differences statistically. were not confirmed statistically.

SC - sole cropping of lentil without a supporting crop SC - sole cropping of lentil without a supporting crop RI - row intercropping of lentil with naked oat RI - row intercropping of lentil with naked oat c bc c 15 ab bc a 15 a 10 ab 10 5 5 0 0 20 cm 25 cm 20 cm 25 cm

Figure 9. The interaction effect effect of row spacing and lentil cropping method on seed yield of lentil crop Figure− 19. The interaction effect of row spacing and lentil cropping method on seed yield of lentil crop (dt(dt ha 1)) (mean (mean for for 2014–2016; 2014–2016; independent independent on on cultivar). cultivar). Diffe Differentrent letters letters indicate indicate significant significant difference difference (dt ha−1) (mean for 2014–2016; independent on cultivar). Different letters indicate significant difference at p ≤ 0.05.0.05. at p ≤≤ 0.05. 4. Conclusions 4. Conclusions Selection of lentil varieties to be grown under organic farming conditions has a significant significant effect effect on seedSelection yield. ofIt lentilis largely varieties determined to be grown by their under competitivecompetitive organic farming ability towardsconditions weeds.weeds. has a Thesignificant lentil variety effect on‘Anita’ seed producedyield. It is higherlargely yieldsdetermined compared by their to ‘Tina’ competitive, but at abilitythe same towards time theweeds. variety The mixturelentil variety gave ‘Anita’higher yieldsproduced than higher var. ‘Tina’ yields over compared the 3 year to study‘Tina’ period., but at the same time the variety mixture gave higherThe yields presence than var.of naked ‘Tina’ oatsover asthe a 3supporting year study cropperiod. in lentil crop allowed crop competitiveness againstThe weed presence species of naked to be oatsincreased, as a supporting significantly crop reducing in lentil the crop dry allowed weed weight.crop competitiveness Nevertheless, againstintercropping weed speciesof lentil towith be oats increased, caused significantlya significant decreasereducing in the lentil dry seed weed yield, weight. on average Nevertheless, by 9.4%, intercropping of lentil with oats caused a significant decrease in lentil seed yield, on average by 9.4%,

Agronomy 2020, 10, 9 11 of 13

‘Anita’ produced higher yields compared to ‘Tina’, but at the same time the variety mixture gave higher yields than var. ‘Tina’ over the 3 year study period. The presence of naked oats as a supporting crop in lentil crop allowed crop competitiveness against weed species to be increased, significantly reducing the dry weed weight. Nevertheless, intercropping of lentil with oats caused a significant decrease in lentil seed yield, on average by 9.4%, compared to sole cropping. This was probably associated with the competitive interactions of plants, as also evidenced by the lower density of lentil grown in the presence of oats. Sowing lentil at different row spacings did not have a significant impact on the number and weight of weeds in lentil crop, as well as on seed yield. Nonetheless, the plant density was found to be higher in the treatments where lentil was sown in wider rows, with a simultaneous decrease in the number of pods per plant. However, for practical reasons, it is better to sow lentil, together with the supporting crop, in wider rows. In lentil crop grown under organic farming conditions, Sonchus arvensis, Stellaria media, Chenopodium album, Thlaspi arvense, Matricaria maritima subsp. inodora, Galinsoga parviflora, Plantago major, Echinochloa crus-galli, and Elymus repens were species that occurred in greatest numbers. The greatest diversity of weed species was determined in the treatments where the mixture of the lentil varieties was sown and in the treatment with the smaller row spacing. Intercropping of lentil with oats resulted in reduced occurrence of Echinochloa crus-galli and Elymus repens.

Author Contributions: P.K. conceptualized the research; P.K. and S.A. designed the research; P.K., S.A., E.K.-P., and K.R. performed the experiments; P.K., S.A., M.S., and H.R. analyzed the data; P.K. and S.A. wrote the paper. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Ministry of Agriculture and Rural Development, Ministry of Science and Higher Education, Poland. Acknowledgments: This research was supported by the Ministry of Agriculture and Rural Development in Poland. Conﬂicts of Interest: The authors declare no conﬂict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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