Relative Yield Total Research Articles

Sweet potato (Ipomoea batatas) and hyacinth bean (Lablab purpureus) in combination provide greater suppression of mile-a-minute (Mikania micrantha) than either crop alone.

In natural systems, diverse plant communities tend to prevent a single species from dominating. Similarly, management of invasive alien plants may be achieved through various combinations of competing species. We used a de Wit replacement series to compare different combinations of sweet potato (Ipomoea batatas (L.) Lam), hyacinth bean (Lablab purpureus (L.) Sweet) and mile-a-minute (Mikania micrantha Kunth) through measures of photosynthesis, plant growth, nutrient levels in plant tissue and soil, and competitive ability. Cultured alone sweet potato and hyacinth beans exhibited higher total biomass, leafstalk length, and leaf area than mile-a-minute. In mixed culture, either sweet potato or hyacinth bean or both together significantly suppressed the mile-a-minute parameters, i.e., plant height, branch, leaf, adventitious root, and biomass (P<0.05). Based on a significantly lower than 1.0 relative yield of the three plant species in mixed culture, we showed intraspecific competition to be less than interspecific competition. Calculated indices (relative yield, relative yield total, competitive balance index, and change in contribution) demonstrated a higher competitive ability and higher influence of either crop compared to mile-a-minute. The presence of sweet potato and hyacinth bean, especially with both species in combination, significantly reduced (P<0.05) mile-a-minute's net photosynthetic rate (Pn), antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, and malondialdehyde), chlorophyll content, and nutrient content (N, P, and K). In soil with mile-a-minute in monoculture soil organic matter, total and available N, total and available K, and available P were significantly greater (P<0.05) than in soil with sweet potato grown in monoculture, but less than in soil with hyacinth bean grown in monoculture soil. Nutrient soil content was comparatively reduced for plant mixtures. Plant height, leaf, biomass, Pn, antioxidant enzyme activities, and plant and soil nutrient contents of sweet potato and hyacinth bean tended to be much greater when grown with two crops compared to in mixture with just sweet potato or hyacinth bean. Our results suggest that the competitive abilities of both sweet potato and hyacinth bean were greater than that of mile-a-minute, and also that mile-a-minute suppression was significantly improved via a combination of the two crops compared to either sweet potato or hyacinth bean alone.

Sahelian smallholders’ varietal mixtures reconcile yield and agrobiodiversity conservation

In the current setting, marked by the major challenges of growing food demand and climate change impacts, the ability of sub-Saharan agriculture to meet population needs depends on the resilience and adaptation capacity of this system. Using agrobiodiversity to promote agricultural sustainability is a strategy that has garnered much attention lately. Research suggests that mixing species or varieties within crop fields could increase the yield and/or stability. This mixing is also geared towards the conservation of crop diversity while ensuring that the various associated products and services will be available at the farm level.Few recent research studies have highlighted the benefits of varietal mixtures for Africa. This lack of research is a concern, given that this continent is considered to be highly vulnerable to climate change. This study was carried out to test whether plots with varietal mixtures would outperform monovarietal plots in terms of yield and pathogen regulation under smallholder farming conditions in Senegal. Together with farmers, we conducted 30 experiments in which mixtures of early- and late-flowering pearl millet landraces were grown in these farmers’ fields, while monitoring their low input management. We noted a significant positive effect of varietal mixtures on grain yield (mean gain of 63 ± 31.5 kg ha−1 for mixture plots, p = 0.046) with a relative yield total (RYT) averaging 1.87 ± 0.94. Both early- and late-flowering landraces benefited from mixtures, with a greater impact on late-flowering landraces. Higher fertility in terms of the seed number, percentage of fertile tillers and number of panicles per tiller, was documented in mixture plots. We did not find a significant effect of mixture on fodder, striga or weed infestation.In water and nutrient resource limiting conditions, such as in Sahelian agroecosystems, growing mixtures of early- and late-flowering landraces appeared to be an efficient way to increase productivity while ensuring agrobiodiversity conservation. Perhaps even more importantly, mixtures allowed farmers to harvest multiple products with different uses in an agrosocioecosystem context with constantly increasing land pressure.

Biomass Allocation and Competitive Ability of a Semiarid Perennial Grass and a Legume in Mixtures under Periodical Soil Water Decreasing Conditions

Soil moisture is the key factor controlling plant growth in semiarid grasslands. Here, we sought to evaluate the effects of soil moisture decreasing at different growth stages on biomass accumulation, water use efficiency, and plant-plant interaction of a C3 leguminous subshrub Lespedeza davurica (L) and a C4 perennial grass Bothriochloa ischaemum (B) when sown singly and as a mix in five different ratios in a pot experiment. Results showed that soil water decrease significantly reduced total biomass production of the mixtures by 3.7–53.8% compared with well-watered conditions, and plants at the heading and flowering periods were more vulnerable to soil water decline than those at the late stage. The relative yield total (RYT) of the mixtures was mostly greater than those sown singly. Soil water decreasing increased root/shoot ratio and water use efficiency (WUE) of the mixtures, and such effects were mediated by mixture ratio and/or growth stage. In the mixtures, a strong intraspecific competition was observed in B. ischaemum, whereas interspecific competition in L. davurica. The highest overall biomass (86.47 g pot−1) and WUE (6.33 g kg−1) were observed when the mixture ratio was B:L = 10:2 regardless of soil moisture, and thus could be considered an optimal mixture ratio for establishing restored grassland using the two species. Our results suggest that sown seed mixtures of the two species with an appropriate ratio could sustain a relatively high total biomass production and improve WUE under soil water decreasing conditions in the semiarid Loess Plateau.

Kompetisi Gulma Teki Terhadap Pertumbuhan Dan Produksi Bawang Varietas Super Philip Dan Varietas Bauji

ABSTRACTShallot is a primary commodity with high economic value. However, the productivity of shallot is still low due to the competition with nutgrass. Nutgrass reduces the productivity of shallot down to 50 - 80%. This study aimed to analyze the impact of nutgrass population towards the growth and productivity of shallot, particularly the Super Phillip and Bauji varieties. This study also aimed to find the most adaptable shallot variety in regards to the combination of nutgrass in Wayamiya Village of East Bacan District in South Halmahera Regency from January to March 2020. The methods used in this study were Randomized Complete Block Design (RCBD) in a factorial pattern consisting of two factors and Replacement Series Methods. The latter was used to analyze the interaction of these two plant species and the combination of both. The variables observed include the height of the plant (cm), the number of seedlings, the weight of fresh bulb (g), the air-dried weight (g), the dry weight without stover (g), the average diameter of air-dried bulb (cm), the fresh weight of nutgrass (g), the dried weight of nutgrass (g), and the numbers of nutgrass bulbs per cluster and plot. Based on the variance analysis calculations, the population of nutgrass had a real impact on produced shallots, particularly in terms of height (cm), weight of fresh bulb per plot, weight of dried bulb per plot, weight of dried bulb without stover, and diameter of bulb per plot. The relative yield total (RYT) and Relative Crowding Coefficient were used to examine the occurrence of competition between the two plants. The result of this study revealed the production of dried super phillip bulb without the presence of nutgrass was 9,5 tons/hectare. Meanwhile, with the presence of 4 nutgrass (T1), 8 nutgrass (T2), and 12 nutgrass (T3), the average weight of dried super phillip bulb was 6 tons/hectare. This showed a decrease of 3 tons/hectare or around 30%/hectare. Moreover, in regards to dried bauji bulb without the presence of nutgrass, the production was 9.3 tons/hectare. With the presence of 4 nutgrass (T1), 8 nutgrass (T2), and 12 nutgrass (T3), the dried bauji bulb production decreased to 3.3 tons/hectare or around 60%/hectare. There was a negative interaction between bauji shallots with 10% of nutgrass treatment in the planting. In this case, the RYT value was &lt;1. The Relative Crowding Coefficient value of super phillip shallots with 10%, 20%, and 30% of nutgrass populations was more than one. This indicated the super phillip variety was adaptable with the presence of nutgrass. Meanwhile, the Relative Crowding Coefficient value of bauji shallots was below one.Keywords: : Nutgrass, Shallot, Competition

Evaluation of dry matter accumulation and competition indices of grass-legume mixtures in the semi-arid Kano Nigeria

An experiment was conducted from April to September 2018 at Bayero University Kano, to determine the nature of competition between Sorghum almum (Columbus grass) and three forage legumes namely Cajanus cajan (pigeon pea), Lablab purpureus (lablab) and Mucuna pruriens (velvet bean) on the basis of dry matter accumulation and competition indices. The treatments were (Sorghum almum sole, three legumes sole and mixtures of grass with legumes at 50:50 replicated in four blocks in randomized complete block design. Seeds of grass and legumes were sown in 3.5m *2m plots. The results showed that sole lablab produced higher (ρ &lt;0.05) cumulative total dry matter (42.07 t ha-1) than sole grass, monoculture of other legumes and mixtures. The cumulative total plant biomass and mean relative yield total of mixtures were not significantly different. Sorghum-Mucuna mixture with mean relative yield total value (1.11) appeared to be more advantageous in terms of efficient resource sharing than other mixtures. Sorghum-Mucuna mixture was recommended as the most compatible combination.

Soil Water Availability Changes in Amount and Timing Favor the Growth and Competitiveness of Grass Than a Co-dominant Legume in Their Mixtures.

The grasslands on the semi-arid Loess Plateau of China are expected to be particularly responsive to the size and frequency changes of extreme precipitation events because their ecological processes are largely driven by distinct soil moisture pulses. However, the plant growth and competitiveness of co-dominant species in response to the changes in the amount and timing of soil water are still unclear. Thus, two co-dominant species, Bothriochloa ischaemum and Lespedeza davurica, were grown in seven mixture ratios under three watering regimes [80 ± 5% pot soil capacity (FC) (high watering), 60 ± 5% FC (moderate watering), and 40 ± 5% FC (low watering)] in a pot experiment. The soil water contents were rapidly improved from low to moderate water and from moderate to high water, respectively, at the heading, flowering, and maturity stages of B. ischaemum, and were maintained until the end of the growing season of each species. The biomass production of both species increased significantly with the increased soil water contents, particularly at the heading and flowering periods, with a more pronounced increase in B. ischaemum in the mixtures. The root/shoot ratio of both species was decreased when the soil water availability increased at the heading or flowering periods. The total biomass production, water use efficiency (WUE), and relative yield total (RYT) increased gradually with the increase of B. ischaemum in the mixtures. The relative competition intensity was below zero in B. ischaemum, and above zero in L. davurica. The competitive balance index calculated for B. ischaemum was increased with the increase of the soil water contents. Bothriochloa ischaemum responded more positively to the periodical increase in soil water availability than L. davurica, indicating that the abundance of B. ischaemum could increase in relatively wet seasons or plenty-rainfall periods. In addition, the mixture ratio of 10:2 (B. ischaemum to L. davurica) was the most compatible combination for the improved biomass production, WUE, and RYTs across all soil water treatments.

Soil Fungi Promote Biodiversity–Productivity Relationships in Experimental Communities of Young Trees

Soil fungi are a major factor maintaining plant diversity and productivity, but the underlying mechanisms are still poorly understood. Based on a biodiversity–ecosystem functioning experiment in southeast China, we evaluated the impacts of root-associated soil fungi on plant total, above- and belowground biomass production in monocultures and in different 2- and 4-tree species mixtures using two pools of four subtropical tree species each. All plots were inoculated with forest soil but half of the plots were additionally treated with fungicide to suppress fungi. Tree species richness promoted individual biomass only in control but not in fungicide-treated soils, leading to positive relative yield totals (RYTs, sum of the relative growth of each tree species in mixture to monoculture) of mixed species plots in control soils. Additive partitioning analysis showed that the net biodiversity effects were due to positive complementarity effects (CE) rather than selection effects. The relative yield of individual tree species was positively correlated with arbuscular mycorrhizal (AM) colonization for AM trees but not significantly correlated with ectomycorrhizal (EM) colonization for EM trees. The molecular analysis of the root-associated fungi showed that larger RYT and CE values were correlated with greater dissimilarity in pathogenic fungal communities between tree species, suggesting distinct pathogen compositions will result in overyielding and high complementarity in mixture.

Late-seeded cover crops in a semiarid environment: overyielding, dominance and subsequent crop yield

AbstractInterest in cover crops is increasing but information is limited on integrating them into crop rotations especially in the relatively short growing season on the northern Great Plains. A 3-yr research project, initiated in 2009 near Mandan, North Dakota, USA, evaluated (1) what impact cover crops may have on subsequent cash crops yields and (2) whether cover crop mixtures are more productive and provide additional benefits compared to cover crop monocultures. The study evaluated 18 different cover crop monocultures and mixtures that were seeded in August following dry pea (Pisum sativum L.). The following year, spring wheat (Triticum aestivum L.), corn (Zea mays L.), soybean (Glycine max L.) and field pea were seeded into the different cover crop treatments and a non-treated control. A lack of timely precipitation in 2009 resulted in a low cover crop yield of 17 g m2 compared to 100 and 77 g m2 in 2008 and 2010, respectively. Subsequent cash crop yield was not affected by late-seeded cover crops. Cool-season cover crop monocultures were more productive than warm-season monocultures and some mixtures in 2008 and 2010. Relative yield total did not differ from one in any cover crop mixture suggesting that overyielding did not occur. Species selection rather than species diversity was the most important contributor to cover crop yield. Cover crops can be grown following short-season cash crops in the northern Great Plains, but precipitation timing and species selection are critical.

Potential use of Helianthus tuberosus to suppress the invasive alien plant Ageratina adenophora under different shade levels

BackgroundAn ecological approach for managing biological invasions in agroecosystems is the selection of alternative crop species to manage the infestation of invasive alien plants through competition. In the current study, plant growth, photosynthesis, and competitive ability of the crop Helianthus tuberosus L. (Jerusalem artichoke) and the invasive alien plant Ageratina adenophora (Spreng.) R. M. King and H. Rob were compared under varying shade levels by utilizing a de Wit replacement series method. We hypothesized that H. tuberosus had higher competitive ability than A. adenophora even under shaded conditions.ResultsThe results showed the main stem, leafstalk length, leaf area, underground biomass, and aboveground biomass of A. adenophora were significantly lower compared to H. tuberosus in monoculture although A. adenophora had a greater number of branches that were longer on average. Under full sunlight, the total shoot length (stem + branch length), main stem length and branch length of A. adenophora were significantly suppressed (P < 0.05) by increasing proportions of H. tuberosus, and the same morphological variables of H. tuberosus were significantly higher with decreasing proportions of H. tuberosus. With increasing shade rates and plant ratios, the plant height, branch, leaf, and biomass of both plants were significantly suppressed, but to a greater degree in the case of A. adenophora. The net photosynthetic rate (Pn) of H. tuberosus and A. adenophora increased gradually from July to September, then decreased in October. The Pn of H. tuberosus was consistently higher than that of A. adenophora. Although the Pn for both species was significantly reduced with increasing shade rates and plant ratios, A. adenophora experienced greater inhibition than H. tuberosus. The relative yield (RY) of A. adenophora was significantly less than 1.0 (P < 0.05) in mixed culture under all shade levels, indicating that the intraspecific competition was less than interspecific competition. The RY of H. tuberosus was significantly less than 1.0 under 40–60% shade and greater than 1.0 (P < 0.05) under 0–20% shade in mixed culture, respectively, showing that intraspecific competition was higher than interspecific competition under low shade, but the converse was true under high shade. The relative yield total (RYT) of A. adenophora and H. tuberosus was less than 1.0 in mixed culture, indicating that there was competition between the two plants. The fact that the competitive balance (CB) index of H. tuberosus was greater than zero demonstrated a higher competitive ability than A. adenophora even at the highest shade level (60%).ConclusionsOur results suggest that H. tuberosus is a promising replacement control candidate for managing infestations of A. adenophora, and could be widely used in various habitats where A. adenophora invades.

Above and Belowground Relative Yield Total of Clover–Ryegrass Mixtures Exceed One in Wet and Dry Years

Grassland mixtures hold the potential for increasing biomass and productivity. In a field experiment, monocultures and mixtures of eight white clover (Trifolium repens L.) genotypes and perennial ryegrass (Lolium perenne L.) were analyzed over three years (2015, 2016, and 2018) for their species-specific aboveground and belowground biomass. Roots were analyzed by Fourier transform infrared (FTIR) spectroscopy to identify species-specific root mass, vertical distribution, and belowground relative yield total (RYT). Aboveground biomass decreased strongly from 2015 to 2018. Aboveground and belowground RYT were always significantly higher than one. Aboveground biomass overyielded in 2016 and 2018 compared to monocultures. Monocultures of perennial ryegrass displayed a significantly higher proportion of roots in shallow soil layers than white clover in two of the three examined years. In mixtures, these differences in vertical root distribution between both species were not present and perennial ryegrass, and white clover occupied similar vertical niches in 2015 and 2016. Interestingly, in the dry year 2018, white clover had a higher proportion of roots in shallow soil layers than perennial ryegrass in mixtures.

Evaluation of Biomass Yield, Seed Yield and Chemical Composition of Different Varieties of Vetch and Oats Grown in Pure Stand and Mixture in Mareka District, Southern Ethiopia

The study was conducted to evaluate the effect of variety on biomass yield, seed yield, forage quality, and biological compatibility of oats and vetch grown in the pure stand and mixtures. The experiment was conducted during the main cropping season on 16th May 2020 at Gozo Bamush farmers training center in Mareka district, Dawuro zone, Southern Ethiopia. Eight treatments were formulated using two recently released vetch and oat varieties in sole and mixed stands. The experiment was employed in Randomized Complete Block Design with three replications. Data on agronomic parameters, biomass and seed yield as well as chemical compositions were recorded and analyzed by SAS version 9.3 (32). Significant treatment effects were separated by the least significant difference test at p 0.05). Among vetch species, Vicia vilosa 6792 gave higher crude protein content (20.14%) and lower grain yield (1.19t/ha) and acid detergent fiber (40.35) compared to Vicia sativa which had a crude protein content (19.4%), grain yield (1.92t/ha) and neutral detergent fiber content (49.35%). In nutrient, indices showed that the highest TCPY (1.51t/ha) and TNDFY (4.04 t/ha) were obtained from the mixture of Vicia vilosa 6792 + Avena sativa 15153A. Relative yield total of oats and vetch varieties were greater than one in all mixed treatments indicating that the yield obtained in mixed stands was more productive than the same species grown as sole crops. Thus, the relative yield total was higher by 70% in Vicia vilosa 6792 + Avena sativa 15153A mixture. The greatest acceptability in terms of the test was high for grains from pure stands of Avena sativa 5431A Oat and Vicia sativa. For dry matter yield, the best acceptable tasted varieties were Vicia vilosa 6792 and Avena sativa 15153A in both pure stand and mixture. This study highlights the positive potential of Vicia vilosa 6792 + Avena sativa 15153A in forage yield, quality and also could enhance soil fertility to complement forage production at the experiment site. However, the experiment was conducted in only one location over a single season, therefore, repeating the trial at a different location and over seasons would be important to draw a more concrete recommendation.

Impact of New Agricultural Systems on Some Garlic Cultivars

Garlic (Allium sativum) is one the natures versatile medicine plant, it is an important vegetable in Egypt. agriculture system was used to increase yield in various crops. Three garlic cultivars were used ; Balady,Sids40 and Eggaseed1. The garlic cultivars and their mixtures were grown for two seasons, the fresh and cured yield were recorded and relative yield total (RYT) and mixture effect were calculated. Significant differences were found between monoculture and mixture system. Mixtures had a positive effect on yield. RYThigher value was found with the Mixture 80% of either colored (Sids 40 or Eggaseed1) recording 0.896 and 0.929 respectively; and the same mixture gave a higher value of fresh yield. For the mixture effect% the higher value was founded with the mixture 80% Balady+20% Eggaseed1or Sids 40. cultivar system reduce disease severity of garlic purple blotch disease, and the data showed there was a significant differences between mixtures and monoculture for the sensitivity of garlic cultivars to this disease. Garlic (Allium sativum) is one the natures versatile medicine plant, it is an important vegetable in Egypt. agriculture system was used to increase yield in various crops. Three garlic cultivars were used ; Balady,Sids40 and Eggaseed1. The garlic cultivars and their mixtures were grown for two seasons, the fresh and cured yield were recorded and relative yield total (RYT) and mixture effect were calculated. Significant differences were found between monoculture and mixture system. Mixtures had a positive effect on yield. RYT higher value was found with the Mixture 80% of either colored (Sids 40 or Eggaseed1) recording 0.896 and 0.929 respectively; and the same mixture gave a higher value of fresh yield. For the mixture effect% the higher value was founded with the mixture 80% Balady+20% Eggaseed1or Sids 40. cultivar system reduce disease severity of garlic purple blotch disease, and the data showed there was a significant differences between mixtures and monoculture for the sensitivity of garlic cultivars to this disease.

Bean cultivar mixture allows reduced herbicide dose while maintaining high yield: A step towards more eco-friendly weed management

Integrated weed control methods are increasingly demanded to maintain high yield while alleviating negative environmental side effects of control measures. Five field experiments were conducted during 2015–2017 at three locations in Iran to determine the advantage of exploiting enhanced competitive ability of bean (Phaseolus vulgaris L.) via cultivar mixture to reduce herbicide dose. For all experiments, the experimental design was split-plot in randomized complete block with four replications. Main plots were assigned to the factor "herbicide dose" with 5 levels between 0 and 100 % of recommended dose and subplots comprised monoculture of a stand growth type cultivar (STAND), monoculture of a climbing growth type cultivar (CLIMB) and the substitutive (50 % STAND/50 % CLIMB) cultivar mixture (MIXCR). Without herbicide application, the yield of STAND, CLIMB and MIXCR was estimated at 588, 1026, and 1637 kg ha−1, and the corresponding weed biomass (W0) at 388, 215, and 239 g m-2, respectively. The herbicide dose to decrease W0 by 50 % (ed50) was estimated as 69 % of the recommended dose for STAND, while it was 53 and 45 % for CLIMB and MIXCR, respectively. Herbicide application at full rate increased the average yield of STAND by 2610 kg ha−1, but 1115 and 1532 kg ha-1 for CLIMB and MIXCR, respectively. Potential yield of CLIMB at full herbicide rate application was 2141 kg ha−1, while STAND and MIXCR showed statistically the same potential of producing 3198 and 3169 kg h−1 bean yield. However, MIXCR could achieve its potential yield at half of the recommended dose. Relative yield total (RYT) was lower than or equal to one at 75 % and 100 % of the recommended dose, but with decreasing herbicide dose to 50 or 25 % RYT raised to 1.2. Careful selection of cultivars for growing in mixture that combines strong competitor with high yield cultivars is crucial to achieve potential yield with less dependence on herbicides. As we could show for bean, this will help to overcome conflicting management objectives to reach both environmental and economic goals in weed control and crop production.

Arbuscular mycorrhizal symbiosis increases phosphorus uptake and productivity of mixtures of maize varieties compared to monocultures

Abstract Ecological intensification seeks to achieve crop yield increases by intensifying complementary or facilitative interactions between plant species or varieties. Different species of arbuscular mycorrhizal fungi (AMF) exhibit niche differentiation and show selectivity towards certain plants, which can further enhance complementarity. It is not clear whether in the presence of one AMF species, where mycelial networks connect crop species, opportunities for complementarity effects may be reduced. We grew monocultures and mixtures of maize varieties in a greenhouse with one species of AMF, Funneliformis mosseae, during two consecutive years to investigate whether under such conditions the mycorrhizal symbiosis would affect complementarity and overyielding compared to non‐mycorrhizal plants. Variety mixtures showed increased phosphatase activity and mycorrhizal colonization, enhanced phosphorus uptake and overyielding when plants were mycorrhizal. There was no overyielding when plants were non‐mycorrhizal. The increase in relative yield total was due to complementarity effects. Synthesis and applications. Our study implies that appropriate agricultural management that enhances mycorrhizal fungal contribution to ecosystem services may result in overyielding in terms of yield or phosphorus uptake through mixing varieties within one crop species.

Maize plant density affects yield, growth and source-sink relationship of crops in maize/peanut intercropping

Abstract Maize (Zea mays L.)/peanut (Arachishypogaea L.) intercropping has been widely practiced in semi-arid regions to reduce wind erosion and improve resource (e.g. water and light) use efficiencies. Knowledge on optimal maize plant density is lacking from perspective of dry matter accumulation among organs in this intercropping system. We quantified the effect of maize plant density on relative yield total (RYT), maize and peanut yields, and maize dry matter of organs (ears, leaves, and stems) in maize/peanut intercropping. Field experiments were conducted in a semi-arid area of China in 2015 and 2016. Three maize plant densities (6, 9 and 12 plants m−2) were tested in maize/peanut intercropping (per unit growing area designed for maize) and sole systems, whereas the plant density of intercropped peanut and sole peanut was fixed as 24 plants m-2. The beta and logistic growth functions were used to quantitatively characterize the dynamics of dry matter allocation among organs in maize. Increasing maize plant density significantly increased maize yield gain, but not increased peanut yield loss, in maize/peanut intercropping. The greatest yield advantage (RYTs of 1.21 in 2015 and 1.13 in 2016) occured in maize/peanut intercropping with maize planted at 9 plants m−2. Increasing plant density increased leaf growth rate, but reduced leaf longevity and dry matter allocation to ears for maize grown in both intercropping and sole systems. But, greater increases in leaf growth rate and leaf longevity for intercropped maize compared with sole maize resulted in a greater increase in dry matter accumulation for maize grown at 9 and 12 plants m−2. Greater increases in ear dry matter accumulation and yield were found for maize grown at 9 plants m−2 due to greater dry matter allocation to ears. We conclude that the different responses to plant density of the source capacity (leaves) and sink strength (ears) for maize in intercropping and sole systems could help optimize maize plant density (9 plants m-2) for greater maize yield gain and yield advantage in maize/peanut intercropping.

Border-row proportion determines strength of interspecific interactions and crop yields in maize/peanut strip intercropping

Strip intercropping enables increases in yields and ecological services in agriculture. Crop yields of species grown in strip intercropping are often related to the yield responses (increases or decreases) in the outer rows of the strips: the border rows. This suggests that the yield response can be modulated by changing the proportion of border rows in the field. Here we studied the relationship between component species yields and proportion of border rows in strip intercrops of maize (Zea mays L.) and peanut (Arachis hypogaea Linn.). We tested four different intercrops with equal proportions of maize and peanut but a different number of rows per strip: M2P2 (2 rows maize intercropped with 2 rows peanut), M4P4, M6P6, M8P8, and sole maize (SM) and sole peanut (SP). The border-row proportions were 1, 0.5, 0.33 and 0.25 for the intercropping M2P2 to M8P8, respectively, and 0 for the pure stands. Yield responded positively to the proportion of border rows for maize, but negatively for peanut, confirming the dominance of maize in this system. Kernel number per ear of maize and pod number per plant of peanut were the main yield components that responded to the border-row proportion. Across three years, relative maize yield (yield in intercropping divided by yield in monoculture), varied from 0.76 in M2P2 to 0.56 in M8P8, while relative peanut yield varied from 0.19 in M2P2 to 0.39 in M8P8. Relative yield total was not significantly different from one in any of the mixtures. Yield of intercropped maize in border rows was 48% higher than in inner rows and the sole crop, in part due to a significantly higher kernel number per ear (13%). Yield of intercropped peanut in border rows was on average 29% lower than in inner rows and 48% lower than in sole peanut. Yield responses in border rows were independent from the border-row proportion. The results show that relative crop yields responded strongly to variation in border-row proportion resulting from variation in strip width from 1 to 4 m. Strip width thus provides a mechanism to control the strength of interspecific plant interactions and relative yields in strip intercropping.

Interacción de plantas y concentración de ergovalina en la mezcla de Lotus tenuis y Schedonorus arundinaceus infectada con el hongo Epichloë coenophiala

Schedonorus arundinaceus (tall fescue) population can be infected by the endophyte fungus Epichloe coenophiala, responsible of livestock intoxication due to fungal alkaloids (i.e., ergovaline). The effects of ergovaline in pastures can be attenuated through dilution; this is, to interseed infected tall fescue (E+) with legumes, endophyte-free grass, or with both. Plant interaction and ergovaline concentration in mixture of tall fescue (E+) and Lotus tenuis, a forage legume, were investigated in replacement series experiments under defoliation conditions. The interaction between species was analysed through relative yield total (RYT) of the forage biomass, aggressivity index (AI), plant cover and ergovaline concentration. The work was performed in field conditions. Six cuttings were applied during the experimental period. Plant monocultures of each species were at a constant density of 80 pl/m2, while mixtures ratios were 20:60, 40:40 and 60:20 pl/m² of L. tenuis and tall fescue, respectively. Mortality of L. tenuis and tall fescue plants was not observed. Tall fescues yield and plant cover, in monoculture and in mixture, were higher than in L. tenuis. RYT was higher than 1 for all mixtures. According to AI, in mixture, tall fescue was the dominant species and overcompensated the lower yield of L. tenuis. At the early Autumn, ergovaline concentration in monoculture was 1.637±0.594 ng/g, and in the 40:40 mixture was 0.407±0.109 ng/g. Forage production was higher in mixtures than in monocultures, and L. tenuis contributed to reduce ergovaline concentration. According to the results, 40:40 pl/m2 of tall fescue and L. tenuis was the best species combination. A positive effect of L. tenuis on growth of tall fescue mediated by nitrogen availability could have allowed the plant coexistence. Future experiments should analyse the variation of alkaloid concentration and forage production in tall fescue pastures, according to L. tenuis proportion, defoliation frequency and intensity under different seasons.https://doi.org/10.25260/EA.20.30.1.0.944

Competition among native and invasive Phragmites australis populations: An experimental test of the effects of invasion status, genome size, and ploidy level.

Among the traits whose relevance for plant invasions has recently been suggested are genome size (the amount of nuclear DNA) and ploidy level. So far, research on the role of genome size in invasiveness has been mostly based on indirect evidence by comparing species with different genome sizes, but how karyological traits influence competition at the intraspecific level remains unknown. We addressed these questions in a common‐garden experiment evaluating the outcome of direct intraspecific competition among 20 populations of Phragmites australis, represented by clones collected in North America and Europe, and differing in their status (native and invasive), genome size (small and large), and ploidy levels (tetraploid, hexaploid, or octoploid). Each clone was planted in competition with one of the others in all possible combinations with three replicates in 45‐L pots. Upon harvest, the identity of 21 shoots sampled per pot was revealed by flow cytometry and DNA analysis. Differences in performance were examined using relative proportions of shoots of each clone, ratios of their aboveground biomass, and relative yield total (RYT). The performance of the clones in competition primarily depended on the clone status (native vs. invasive). Measured in terms of shoot number or aboveground biomass, the strongest signal observed was that North American native clones always lost in competition to the other two groups. In addition, North American native clones were suppressed by European natives to a similar degree as by North American invasives. North American invasive clones had the largest average shoot biomass, but only by a limited, nonsignificant difference due to genome size. There was no effect of ploidy on competition. Since the North American invaders of European origin are able to outcompete the native North American clones, we suggest that their high competitiveness acts as an important driver in the early stages of their invasion.

Can we make quantitative predictions for relative yield with incomplete knowledge of model parameters?

A main limitation in community ecology for making quantitative predictions on species abundances is often an incomplete knowledge of the parameters of the population dynamics models. The simplest linear Lotka-Volterra competition equations (LLVCE) for S species require S2 parameters to solve for equilibrium abundances. The same order of experiments are required to estimate these parameters, namely the carrying capacities (from monoculture experiments) and the competition coefficients (from biculture or pairwise experiments in addition to monoculture ones). For communities with large species richness S it is practically impossible to perform all these experiments. Therefore, with an incomplete knowledge of model parameters it seems more reasonable to attempt to predict aggregated or mean quantities, defined for the whole community of competing species, rather than making more detailed predictions, like the abundance of each species. Here we test a recently derived analytical approximation for predicting the Relative Yield Total (RYT) and the Mean Relative Yield (MRY) as functions of the mean value of the interspecific competition matrix a and the species richness S. These formulae with only a fraction of the model parameters, are able to predict accurately empirical measurements covering a wide variety of taxa such as algae, vascular plants, protozoa. We discuss the dependence of these global community quantities on the species richness and the intensity of competition and possible applications are pointed out.

Intercropping fenugreek (Trigonella foenum‐graecum L.) and barley (Hordeum vulgare L.) with and without biochar: Tests along a competition gradient

AbstractIntegrating soil amendment biochar to legume‐based intercropping systems may amplify the intercropping benefits and lead to more sustainable production due to its positive effects on the soil physicochemical and biological environment. Fenugreek (Trigonella foenum‐graecum) is a legume used in an intercropping system in several countries in Southern Europe, the Middle East, and Asia. A barley cultivar and an Iranian fenugreek ecotype were studied in two replacement series experiments to find the best combination of the two species as well as the effect of adding biochar to the soil. Fenugreek and barley were grown in 4‐L pots in five density combinations (20:0, 15:5, 10:10, 5:15, 0:20) with and without application of biochar in sandy loam soil. The biomass, nitrogen (N) and carbon (C) amount of the two crops were measured fifty days after sowing, and the Relative Yield Total (RYT) was estimated. Our results showed that biochar application resulted in a higher total biomass, N and C amount in all combinations of fenugreek and barley. Total biomass was increased by biochar 19.2% when fenugreek was grown alone and 8.1 and 12.9% in series with 25 and 50% barley when biochar was added, respectively. Biochar increased dry matter, N and C accumulation in both crop species in the mixtures. An exception was the C amount of barley which was not influenced by biochar in intercropping. RYT values were largest for biomass, C and N amount in mixtures with 15 fenugreek plants per pot and 5 barley plants per pot corresponding to approximately 400 fenugreek plants per m mixed with 130 barley plants per m2. Biochar application increased RYT of the total dry weight by 2.7 and 5.5% in mixtures of 25 and 50% barley plants, RYT of the total nitrogen by 0.8% in mixtures with 25% barley plants, and RYT of the total carbon by 2.7 and 6.6% in mixtures with 25 and 50% barley plants. The RYT values declined with increasing number of barley plants as a result of a less competitive ability of fenugreek when growing in high barley densities. The yield was highest with intercropping but monoculture of barley also resulted in high yields. The total highest yield was found when approximately 130 fenugreek plants per m2 were mixed with 400 barley plants per m2. Mixtures with 75% fenugreek and 25% barley obtained RYT values larger than 1 for biomass, carbon and nitrogen percentages.