High Sowing Density Research Articles

Root growth and belowground interactions in spring wheat /faba bean intercrops

Abstract Background and aims Intercrops offer multiple advantages over sole crops. The aim of our study was to characterize root growth and interactions in spring wheat/faba bean intercrops to better understand belowground interactions that govern resource capture. Materials and methods A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities, defining three intercropping designs. Destructive root coring was conducted (0–100 cm) in the intercrops and sole crops at two development stages. FTIR spectroscopy was used to discriminate the species’ root masses. The plant-plant interaction index was calculated to represent the belowground interactions. Results A negative impact of intercropping on total root mass was observed in the treatment with high sowing density in both stages. For the fully and partial replacement design treatments, plant-plant facilitation was more pronounced than competition in all layers. Competition dominated root growth in the treatment with high sowing density in both stages. Lower sowing densities encouraged deep root growth of wheat (both cultivars) in intercropping. The early root growth in depth and in density of one spring wheat cultivar impacted negatively faba bean root growth. Intercropping resulted in a grain yield advantage in both fully and only one partial replacement design treatment. Conclusion In the intercrops, total root mass and plant-plant interactions were affected more by sowing density than by the spring wheat cultivar. Understanding the effect of sowing density on root growth in intercropping can help to support the design of sustainable intercropping systems.

The effects of native seed mix composition and sowing density on plant community reassembly in wetlands

AbstractSeed‐based restoration of wetlands is often necessary to improve important ecosystem functions (e.g., invasion resistance and habitat provisioning) and meet society's need for wetland ecosystem services such as supporting recreational activities and improving water quality. However, persistent questions remain about the composition and sowing density of seed mixes needed to restore robust native wetland plant communities. In Great Salt Lake wetlands (Utah, USA), the revegetation of native species is crucial to recovering critical habitat and preventing reinvasion of the invasive, non‐native grass Phragmites australis and other invasive species (e.g., Typha spp.). In greenhouse and field experiments, we investigated the effects of seed mix composition and sowing density on plant community reassembly. We predicted that seed mixes containing native forb species with resource‐preempting traits (e.g., rapid seedling emergence and high aboveground growth rate) and high sowing densities (>5500 pure live seed m−2), would increase native plant light acquisition and establishment, thereby limiting invasive species. To our surprise, the effect of seed mix composition on native plant performance (cover and biomass) varied among the experiments, with distinct differences between plant functional groups arising. Native forb species had the highest performance in the greenhouse, but native grasses performed better in the field. Although multiple seed mix compositions show promise for establishing high native cover and biomass, these mixes may not always suppress invasive species. Interestingly, seed mix composition most often affected plant performance independent of sowing density. However, in one greenhouse experiment, we found that only slow‐growing mixes required a high sowing density to maximize native cover, an indication that the ideal sowing density may depend on the seed mix composition. Our research also supports the idea that in addition to reducing propagules of invasive species via appropriate management strategies, the application of higher sowing densities (>5500 pure live seed m−2) may lead to more favorable outcomes when a high density of invasive plant seeds remains or stressful field conditions are present. This research contributes to knowledge of plant community reestablishment in wetlands and demonstrates how seed‐based restoration strategies can catalyze native species revegetation and, in some situations, reduce the cover of invasive species.

An Agronomic Efficiency Analysis of Winter Wheat at Different Sowing Strategies and Nitrogen Fertilizer Rates: A Case Study in Northeastern Poland

This study was undertaken to examine the influence of the sowing date, sowing density, and split spring application of nitrogen (N) fertilizer on plant density, tillering, yield components, and grain yields of winter wheat (Triticum aestivum L.) grown in northeastern Poland between 2018 and 2021. The experiment had a split-plot design with three sowing dates (early (3–6 September), delayed by 14 days, and delayed by 28 days), three sowing densities (200, 300, and 400 live grains m−2), and three split spring N rates (40 + 100, 70 + 70, and 100 + 40 kg ha−1 applied in BBCH stages 22–25 and 30–31, respectively). The number of spikes m−2 increased by 11% on average when winter wheat was sown with a delay of 14 days (17–20 September) and 28 days (1–4 October). The number of spikes m−2 was highest when winter wheat was sown at 300 and 400 live grains m−2. The application of 100 + 40 kg N ha−1 (BBCH 22–25 and 30–31, respectively) increased the number of spikes m−2. An increase in sowing density from 200 to 300 to 400 live grains m−2 decreased the number of grains spike−1 by 5% and 7%, respectively. Thousand grain weight (TGW) increased by 1% and 2% when sowing was delayed by 14 (17–20 September) and 28 days (1–4 October), respectively. In northeastern Poland, grain yields peaked when winter wheat was sown between 17 September and 4 October (10.52–10.58 Mg ha−1). In late-sown winter wheat, grain yields increased due to a higher number of spikes m−2 and higher grain weight. The highest sowing density (400 live grains m−2) induced a greater increase in grain yields than the lowest sowing density (200 live grains m−2) (10.25 vs.10.02 Mg ha−1). In winter wheat sown at a density of 400 live grains m−2, the increase in grain yields resulted in a higher number of spikes m−2. Grain yields peaked in response to 100 kg N ha−1 applied in BBCH stages 22–25 and 40 kg N ha−1 applied in BBCH stages 30–31 (this split N rate increased the number of spikes m−2). In turn, the highest straw yield (6.23 Mg ha−1) was obtained when the second split of N fertilizer was applied in BBCH stages 30–31 (40 + 100 kg N ha−1). Straw yields decreased significantly (by 6%) when winter wheat was sown late (early October). Delayed sowing (mid-September and early October) increased the harvest index (HI) of winter wheat by 5–7%. Split spring N application influenced grain and straw yields, but it had no effect on the HI of winter wheat.

The effects of the different sowing methods and planting density on the yield components of soybean (Glycine max) under intercropping condition with rhodes grass (Chloris gayana Kunth.)

In Japan, grass-legume intercropping systems are being developed to increase quality and yield of grain and forage. Hence, this study evaluated the effects of sowing methods and planting density on yield traits of forage soybean under intercropping condition with rhodes grass. The field experiment was laid on in a completely randomized block design with four treatments and four replications. Rhodes grass seeds were sown at 2.8 kg/10a in a field containing mono- and intercropping-plots. For soybeans, two levels of sowing densities (about 15 or 30 seeds/m2: named “L” and “H”) and two sowing methods (row or spray: named “R” and “S”) were applied for a total of four different intercropping combinations. Rhodes grass DMY obtained the highest in low level of sowing density with rowing methods (LR) (338 kg/10a) while soybean DMY obtained the highest in high level of sowing density with rowing methods (HR) (251 kg/10a) and in high level of sowing density with spray methods (HS) (177 kg/10a). Intercropping at low density increased CP (12%) and CPY (40.4 kg DM/10a) in Rhodes grass, and CP (18.9%) in soybeans, whereas high sowing density increased soybean CPY in HR (41.5 kg DM/10a) and contributed to higher soybean CPY in DM percentage at 66% (HS) and 56% (HR). Overall, high density sowing increased the 1st total DMY while row sowing increased the 1st total CPY in both crops at the first cutting, while monocropping increased Rhodes grass yield and plant length at the second-cutting. Also, sowing soybean by a broadcast spreader could obtain sufficient crude protein yield as a forage soybean in southern Kyushu, Japan. Further studies are needed for soybean overseeding method and use of early-maturity soybean lines

The Effects of Different Sowing Density and Nitrogen Topdressing on Wheat Were Investigated under the Cultivation Mode of Hole Sowing

Hole sowing is a new and efficient cultivation method with few studies. This study investigated the effects of different sowing densities and nitrogen topdressing at the jointing stage on dry matter, quality, and yield under wheat hole sowing to provide a theoretical basis for integrating wheat fertilizer and density-supporting technology. In this study, a two-factor split-plot design was used. The sowing density was the main plot, and four levels were set: D1, D2, D3, and D4 (238, 327, 386, and 386 suitable seeds·m−2). The four sowing levels were sown according to 8 grains/hole, 11 grains/hole, 13 grains/hole, and 16 grains/hole, respectively, with a row spacing of 25 cm and a hole spacing of 13.5 cm; the amount of nitrogen fertilizer applied at the jointing stage was the sub-area, with four levels: N1, N2, N3, and N4 (0, 60, 120, and 180 kg·ha−1). After two years of experimental research, the following main conclusions are drawn: the use of high sowing density and nitrogen topdressing is helpful to improve the dry matter quality of wheat spikes at the maturing stage; the sowing density had significant or highly significant effects on protein content, starch content, and sedimentation value. The yield from 2018–2019 reached a maximum of 8448.67 kg·ha−1 under D4N4 treatment, and the yield from 2019–2020 reached a maximum of 10,136.40 kg·ha−1 under D4N3 treatment. Therefore, the combination of 225 kg·ha−1 sowing density and 120–180 kg·ha−1 nitrogen topdressing at the jointing stage can be used in field production, which can help improve wheat production potential. Similarly, understanding the interaction between wheat hole sowing and different sowing densities and nitrogen topdressing amounts provides a practical reference for high-yield wheat cultivation techniques.

Does a high sowing density of common bean change the weed interference periods?

Does a high sowing density of common bean change the weed interference periods?

Does Belt Uniform Sowing Improve Winter Wheat Yield under High Sowing Density?

The belt uniform (BU) sowing pattern can improve the yield of winter wheat, but whether and how the BU sowing pattern can increase yield under different sowing densities is unknown. The field study was conducted in Guiyang (Guizhou province) during the growing season in 2017–2018, 2018–2019, and 2019–2020. Four winter wheat cultivars were used in field experiments to investigate the changes of the dry matter accumulation and partition, yield and yield components at maturity under five sowing densities (75, 150, 225, 300, and 375 plants per m2), and three sowing patterns: line and dense (LD) sowing with 33.3 cm row spacing (LDS); the belt uniform (BU) sowing with 15 cm (BUN), and 20 cm (BUW) row spacing. The BU sowing pattern significantly increases shoot dry matter and grain yield in all four winter wheat cultivars under all five sowing densities and in each growing season, particularly under the high sowing density of 300 and 375 plants m−2. Harvest index was unaffected by the different sowing densities and sowing patterns. While spike number increased, grain weight per spike decreased with the increase in sowing density. The 1000-grain weight and grain number per spike were unaffected by the sowing patterns. The variation in the shoot dry weight can explain 94% variation in grain yield and 66% variation in spike number. Allometric analysis showed that more dry matter was partitioned to the spike than to the stem and leaf. We conclude that the BU sowing pattern can increase grain yield under high sowing densities associated with a high shoot dry matter accumulation and its partition to the spike.

Uniconazole and Adaptability of Transplantations by Enhancing the Competition Tolerance in a High Sowing Density of Rapeseed Blanket Seedlings

Having nursery rapeseed (Brassica napus L.) seedlings at a high density in a tray is an indispensable step to realizing mechanized transplanting for rapeseed. The reduction in seedling quality caused by high sowing density is one of the key factors affecting transplanting quality and yield. Uniconazole has been considered as a potential plant growth regulator to improve plant growth under diverse unfavorable circumstances. In two sowing densities (400 and 800 seeds per tray), an experiment was carried out between 2021 and 2022 to investigate the effects of uniconazole seed-coating treatments on pre-transplant and post-transplant seedling characteristics. The results demonstrate that uniconazole treatment can effectively reduce the high-density-induced reduction in seedling dry matter and leaf area, stem thinness, and stem and petiole overgrowth. Further evidence that uniconazole can improve seedling quality, enhance yield, and lessen yield loss due to high-density sowing was provided by yield at maturity. However, because of the uncontrolled growth during the late stage in the tray, the relative growth rate of seedlings after transplant in the transplant shock stage revealed that lower doses of uniconazole treatment have a negative effect on the seedling recovery. The results of principal coordinate analysis and partial correlation analysis proved that the yield and net assimilation rate were related to the improvement of seedling high-density tolerance by uniconazole treatment. Consequently, 500–750 mg L−1 uniconazole coating per 100 g of seeds in 5 mL is recommended by this study, considering the potential risk of seedling emergence and growth caused by an overdose of uniconazole treatment.

A Balanced Sowing Density Improves Quality of Rapeseed Blanket Seedling

Mechanized transplanting of rapeseed (Brassica napus L.) blanket seedling is an effective strategy to cope with the seasonal conflict and large labor cost in rapeseed production. The sowing density is a key factor to cultivate high-quality seedlings suitable for mechanized transplanting. An experiment was conducted to investigate the effects of different sowing density levels of 638, 696, 754, 812, 870 and 928 seeds per tray (referred as D1, D2, D3, D4, D5 and D6, respectively) on agronomic traits and survival rate after mechanized transplanting of two rapeseed cultivars (Zheyouza108 and Heza17) in 2020 and 2021. The results showed that high sowing density increased plant height but decreased leaf area, collar diameter, biomass accumulation, the ratio of root to shoot and seedling fullness. These negative effects jointly decreased the seedling rate and survival rate after mechanized transplanting. However, the seedlings under D1 and D2 posed a great plant survival rate of more than 95% after mechanized transplanting, suggesting that the seedlings under the two densities were perfect for mechanized transplanting. In addition, hierarchical analysis grouped D1 and D2 into the same class, indicating that their seedling qualities were not significantly different, though the blanket seedlings under D1 outperformed those under D2 in some traits. A sowing density of 696 seeds per tray (D2) is then recommended in this study, altogether considering its high-quality seedlings suitable for mechanized transplanting, and economically, fewer seedling trays required.

Can sowing density facilitate a higher level of forb abundance, biomass, and richness in urban, perennial “wildflower” meadows?

Forb species abundance and richness determine both ecological and social values in naturalistic meadows in urban landscapes. However, species loss and dominance through competition are naturally part of meadow ecological processes often leading on productive soils to large grass biomass in the absence of appropriate management. Sowing density is a design tool to manipulate the initial number of emergents of each component species however high sowing densities may not benefit community performance in terms of species richness and diversity in the longer term. This study investigated the effect of sowing density on forb species abundance, biomass and richness. Two sowing densities approximating to 500 and 1,000 emerged seedlings/m2 were employed with 29 forb and one grass species. The higher sowing density did not lead to a larger grass biomass that dominated the community, as the grass species used was ultimately less competitive than the forb dominants. Increasing sowing density increased the number of forb seedlings initially but this declined, as did species richness in the longer term. In terms of subordinate forb survival, ability to access light resources to survive intense competition from dominants was key. Tall, and native species were more likely to maintain higher seedling numbers in the longer term. The research suggest that lower sowing rates are likely to be most useful on soils which are either unproductive, do not contain a significant weed seed banks, where weed free sowing mulches are employed or in rural situations where there is less immediate political pressure for rapid development of forb rich meadows.

Simulation of winter wheat response to variable sowing dates and densities in a high-yielding environment.

Crop multi-model ensembles (MME) have proven to be effective in increasing the accuracy of simulations in modelling experiments. However, the ability of MME to capture crop responses to changes in sowing dates and densities has not yet been investigated. These management interventions are some of the main levers for adapting cropping systems to climate change. Here, we explore the performance of a MME of 29 wheat crop models to predict the effect of changing sowing dates and rates on yield and yield components, on two sites located in a high-yielding environment in New Zealand. The experiment was conducted for 6 years and provided 50 combinations of sowing date, sowing density and growing season. We show that the MME simulates seasonal growth of wheat well under standard sowing conditions, but fails under early sowing and high sowing rates. The comparison between observed and simulated in-season fraction of intercepted photosynthetically active radiation (FIPAR) for early sown wheat shows that the MME does not capture the decrease of crop above ground biomass during winter months due to senescence. Models need to better account for tiller competition for light, nutrients, and water during vegetative growth, and early tiller senescence and tiller mortality, which are exacerbated by early sowing, high sowing densities, and warmer winter temperatures.

Response of Indian Dwarf Wheat and Persian Wheat to Sowing Density and Hydrothermal Conditions of the Growing Seasons

The need for foods with high nutritional value has led to the rediscovery of ancient wheat species Triticum sphaerococcum and T. persicum as raw materials with valuable consumption properties, but their reintroduction requires assessment of their productivity under different agricultural practices. The field experiments were carried out for three years (2018–2020) to test the hypothesis that the sowing density of T. sphaerococcum and T. persicum (400, 500 and 600 no m−2) will affect their agronomic traits, yield and occurrence of diseases, but the response will depend on the hydrothermal conditions of the growing seasons. In this study, a significant correlation of the grain yield with the amount of precipitation in tillering, and from booting to the beginning of fruit development was demonstrated. The sowing density of T. sphaerococcum had an impact on the grain yield only under moderate drought stress during the growing season (2019), when the highest yield was obtained at a sowing density of 600 m−2. In 2019, the most favorable sowing density was also the highest for T. persicum. In the year with the lowest amount of rainfall during the growing season (2018), the yield of T. persicum was the highest in the lowest sowing density. At the shooting stage, a greater intensity of powdery mildew was observed on T. persicum, especially with higher sowing densities. Increasing the sowing density also increased the occurrence of root rot symptoms in both wheat species in the year that favored the occurrence of this disease (2018). It can be concluded that in the integrated low-input cultivation of T. sphaerococcum and T. persicum, it is justified to use a sowing density of 600 pcs. m−2, in an agroclimatic zone with moderate droughts during the growing season.

Yield performance of oat cultivars in response to sowing dates and densities

Adjustment of seeding density oriented by genotype and conditions of the growing environment may favor growth, development and yield performance of the oat crop. This study aimed to evaluate the growth, lodging, yield components, and grain yield of oat cultivars grown at different sowing dates and densities. Two independent experiments were conducted at two sowing dates (May 5 and June 24) in Londrina-PR under a randomized block design in a 4 × 2 factorial scheme, with four replications. Treatments consisted of four sowing densities (180, 240, 300, and 360 viable seeds m−2) and two cultivars (IPR Afrodite and IPR Artemis). Plant height, number of panicles.m−2, number of spikelets per panicle, number of grains per spikelet, number of grains per panicle, thousand-grain weight, plant lodging, and grain yield were evaluated. The data were submitted to the analysis of joint variance for sowing dates, separately for the cultivars. The averages of sowing dates were compared by the F test and densities submitted to polynomial regression analysis up to 2nd degree, at 5% probability. The first sowing date favors most yield components and grain yield of the cultivars IPR Afrodite and IPR Artemis. In contrast, the number of panicles m−2 was reduced during this growing season for both cultivars. The late sowing date for the IPR Artemis cultivar resulted in a high percentage of lodging at all evaluated densities. However, this phenomenon is more intense at higher sowing densities during the first sowing date. Yield components and grain yield varied according to sowing dates and densities and the cultivar. The highest grain yield of the cultivar IPR Afrodite at the first sowing date was achieved with a lower sowing density than in the later date. However, the highest grain yield of the IPR Artemis cultivar was achieved at density of 280 viable seeds m−2, regardless of the growing season.

Ancient Wheat Species (Triticum sphaerococcum Perc. and T. persicum Vav.) in Organic Farming: Influence of Sowing Density on Agronomic Traits, Pests and Diseases Occurrence, and Weed Infestation

Crop management should be determined to reintroduce ancient wheat. This study aimed to determine: i. the response of the yield of ancient wheat on sowing density; ii. the impact of sowing density on plant health, weed infestation and pest occurrence. Field experiments were carried out in Poland, on three organic farms. The factors were: (1) wheat species: Persian wheat (Triticum persicum Vav.) and Indian dwarf wheat (T. sphaerococcum Perc.), (2) sowing density (400, 500, and 600 grains m−2). Increasing the sowing density of T. sphaerococcum from 400 to 600 grains m−2 increases the grain yield and reduces the pest pressure (Oulema spp. and Aphididae). Sowing densities did not affect the severity of powdery mildew at stem elongation as well as root rot and eyespot at the development of fruit. At the highest sowing density, the leaf area with tan spot symptoms was the highest. The eyespot symptoms occurred more frequently and the damaged plant surface caused by Oulema spp. was larger on T. sphaerococcum. Persian wheat turned out to be more susceptible to weed infestation. Indian dwarf wheat and Persian wheat are useful for organic farming, and the sowing density should be 500 or 600 grains m−2 and 400 grains m−2, respectively.

Physicochemical and Enzymatic Soil Properties Influenced by Cropping of Primary Wheat under Organic and Conventional Farming Systems

The aim of the study was to assess the content of total organic carbon (TOC), macronutrients (P, K, and Mg), and glomalin (easily extractable glomalin-related soil protein (EEGRSP)) in soil, micronutrients (Zn and Cu) in soil and wheat, and the number of insects on plots in an organic (OF) and a conventional farming (CF) system, all against the background of alkaline phosphatase (AlP) and acid phosphatase (AcP) activity. The experimental design included two spring wheat species, Triticum sphaerococcum Percival and Triticum persicum Vavilov, and three sowing densities (grains m−2): 400, 500, 600. Statistical analysis (ANOVA, η2 effect size) showed significant variation in parameters under the influence of experimental factors. In the duration of the field experiment, TOC content in soil had decreased by 61% compared to the content before starting the experiment. The contents of P, K, and Mg and activity of AlP and AcP were higher in soil under T. sphaerococcum. With a sowing density of 600 grains m−2 under OF and CF, the significantly lowest macronutrient content and the highest AlP and AcP activity were found. The parameters tested (TOC, EEGRSP, P, K, Mg, TZn, TCu, AZn, CU in plant, AlP, AcP) were higher under the CF than under the OF system. The experimental factors (spring wheat species and number of germinating grains) were demonstrated to influence the content of the forms of both microelements in soil and plants. In CF, more content in the amount of Zn and Cu was found than in OF. But the content they had did not exceed the standards set for arable soils. Both wheat species had a significant impact on the concentration of glomalin in the soil from the fields cultivated in the OF system. In CF, a significant difference was caused by sowing density and by interaction between wheat species and sowing density. Insects preferred plants grown in the OF system compared to CF. Regardless of cultivation system, the number of insects was greater on the plots of T. sphaerococcum than on plots of T. persicum. There were more insects at higher sowing densities in plants grown in the OF system only.

Root morphological traits and distribution indirect-seededrice underdenseplanting with reducednitrogen.

Water and nutrient absorption from soil by crops mainly depend on the morphological traits and distribution of the crop roots. Dense planting with reduced nitrogen is a sustainable strategy for improving grain yield and nitrogen use efficiency. However, there is little information on the effects of dense planting with reduced nitrogen on direct-seeded inbred rice. Two-year field experiments were conducted with minirhizotron techniques to characterize the root morphological traits and distributions under different nitrogen application rates and sowing densities in two representative inbred rice varieties, Huanghuazhan (HHZ) and Yuenongsimiao (YNSM), grown under three nitrogen application rates (N0: 0 kg ha–1, LN: 135 kg ha-1, HN: 180 kg ha–1) and two sowing densities (LD: 18.75 kg ha−1, HD: 22.5 kg ha−1). Our study showed that dense planting with low nitrogen improved grain yield partly due to the increased panicle number. The higher sowing density with low nitrogen significantly affected the total root number (TRN), total root length (TRL), total root surface area (TRSA), and total root volume (TRV). There was a significant positive correlation between grain yield and TRL in the 10–20-cm soil layer (P < 0.05). The root morphological indexes were positively correlated with dry matter accumulation (P < 0.05) and negatively correlated with nitrogen content (P < 0.05) at the maturity stage. This study showed that a high sowing density with low nitrogen application can improve root morphology and distribution and increase grain yield and nitrogen use efficiency in direct-seeded inbred rice.

A model for the yield losses estimation in an early soybean (Glycine max (L.) Merr.) cultivar depending on the cutting height at harvest

Growing interest in soybean (Glycine max (L.) Merr.) cultivation, especially in the temperate climate zone, necessitates the search for high-yielding varieties with an optimal growing period. In Europe, it is recommended to cultivate early (00) and very early (000) varieties, which due to their biology form the first pair of pods very low, just above the ground. This unfortunately generates losses during harvest. The literature lacks information on the sowing density at which pod-setting in early varieties soybean is highest and what losses this entails during cutting. The objective of this work was to create a mathematical model for estimating seed yield losses depending on varying cutting height applied during harvest and the sowing density. To achieve the goal the position of fruiting nodes and productivity of pods depending on sowing density for the early soybean variety was determined. Availability of water during vegetation period was an important factor having impact on the pods position on stem and therefore strongly influenced seed weight losses caused by the cutting process. According to the model estimations the lowest losses were obtained for the years with the sufficient precipitation during vegetation period and in essence they never exceeded the value of 15 g m−2 even for the highest level of cutting (15 cm) applied during harvest. For all sowing densities (20–140 seeds m−2), the increase of cutting height from 5 up to 10 cm caused increase of seed yield losses typically about two- and threefold. However at the cutting height of 15 cm the losses increased even seven- and eight-fold, especially for the very high sowing densities. The highest percentage seed yield losses (11%) were demonstrated at the lowest sowing density (20 seeds m−2). In the case of favourable distribution of rainfall, high sowing density (80–140 seeds m-2) is recommended because it ensures high yield of soybean. Sowing density of 80 seeds m−2 can be recommended as optimal density from an economic point of view because it provides a relatively high seed yield with the lowest percentage losses and smaller seed costs compared to higher densities giving similar yield.

Reduced crop sowing density improves performance of rare arable weed species more effectively than reduced fertilisation

AbstractCharacteristic arable weed species of dryland cereal fields have undergone significant declines, due to agricultural intensification, to the point that some of them are considered rare. Crop edges host higher abundances of arable weed species, therefore they may act as a refuge for the conservation of these rare arable species. Using mesocosms, we experimentally tested how conditions at field edges (i.e. lower sowing densities and less intensive fertiliser applications) operate on the growth (biomass and height) and reproduction (reproductive biomass and flower onset) of six rare arable species. We found the rare arable species achieved lower biomass when growing with wheat compared with growing alone, and biomass of most of species was lower under high wheat sowing density than under low sowing density. In contrast, fertiliser application affected only two of the six arable species tested, especially when they were growing alone. Although the time to flowering was not affected by the conditions tested, reproductive biomass showed the same trends as overall biomass. These results indicate that conservation of rare arable species must primarily consider reductions in crop competition to increase their biomass and reproductive ability.

High Sowing Densities in Rainfed Common Beans (Phaseolus vulgaris L.) in Mexican Semi-Arid Highlands under Future Climate Change

Mexico holds the largest single bean production area in the world that is vulnerable to drought. Using field data and two future climate scenarios (RCP4.5 and RCP8.5) for the period 2020–2039, this study evaluated three common bean (Phaseolus vulgaris L.) cultivars planted under rainfed conditions at different densities in two locations in the north-central Mexican semi-arid temperate highlands. The sowing densities were 90,000, 145,000, and 260,000 plants ha−1 established in single rows (SR), three rows (3R), and six rows (6R), respectively. The climate change scenarios were derived from an assembly model integrating 11 general circulation models (GCM) selected for Mexico with a 30” arc resolution. The baseline climate was for the period 1961–2010. The ALMANACMEX model (USDA-ARS-INIFAP, Temple, USA) was parameterized and evaluated and then re-run using the climate scenarios. Beans planted at 6R showed the highest increase in seed yield in both climate scenarios, although the response varied by cultivar and time periods. For the growth habit III cultivars, Flor de Mayo Bajio showed no difference in yield, while Pinto Saltillo, a drought-resistant cultivar, showed increases of 13% to 16% at 6R only until 2033. Growth habit I cultivar Azufrado 2 showed more than 60% increases at 6R in both climate scenarios for the full period 2020–2039. These results suggest that considering the projected climate conditions, high sowing densities may be a viable agronomic option for common bean production under rainfed conditions in semi-arid temperate regions, such as the highlands of Mexico, in the near future; however, the selection of the cultivar is a key element to consider in this regard.

Population-level performance of Arabidopsis thaliana (L.) Heynh in dense monocultures

Abstract Aims Very little is known about the performance of non-agricultural plant species in monocultures, even though nearly all agricultural species have experienced the transition from multi-species environments to dense monospecific stands during the breeding process. In the light of recent work that highlighted the possibility that the weedy species Arabidopsis thaliana can offer novel insight into crop breeding, we aimed to test the effect of sowing density on group and individual performance in different photoperiod environments in A. thaliana. Methods We studied the performance of A. thaliana Cvi-0 ecotype. The choice of Cvi-0 was based on a preliminary experiment in which plants of Cvi-0 ecotype exhibited high competitive performance. Sowing densities used were 17.6, 8.8, 4.4, 2.2 and 1.1 cm2 per plant and photoperiod environments 12 or 16 h of day light. Important Findings In this experiment, populations attained constant total seed yield for all densities. Some interaction effect occurred, as at high sowing density and at longer day length plants produced heavier seeds, whereas at shorter day length seed weight was negatively related to plant density. These results shed light on different strategies that annual plants can adopt when they face intense intraspecific competition, and could help to offer new perspectives for breeding crops with enhanced group performance.