Reduced Plant Population Research Articles

Biodiversity and Vegetation Succession in Vineyards, Moravia (Czech Republic)

Maintaining biodiversity in agricultural landscapes is a major challenge for environmental protection in Europe. Vineyards rely heavily on agrotechnical interventions such as herbicide use and tillage for weed control, which affect biodiversity and can lead to soil erosion and resistant weed populations. The fragmentation of agricultural landscapes affects biodiversity by altering community composition and often reducing plant population sizes and genetic diversity. However, it can also increase the abundance of certain species and enhance population resilience to environmental change. Vineyards can support high levels of biodiversity and provide ecosystem services due to their semi-natural habitat structure. This research evaluates vegetation biodiversity using phytosociological relevés in different vineyards. Our results show that species richness and biodiversity are significantly influenced by vineyard age and management type. This study highlights differences in the representation of plant functional groups, with perennial taxa in grassy inter-row contributing to anti-erosion functions and serving as food sources for pollinators. The root zone around vine trunks shows an increase in invasive species with vineyard age, posing a risk to the agroecosystem. Vineyards predominantly follow a ruderal ecological strategy, using nutrients and light efficiently, while tolerating management disturbances. Understanding these dynamics is critical for developing sustainable vineyard management practices that support biodiversity and ecological resilience, counteract the homogenization of agricultural landscapes, and promote the coexistence of viticulture and species-rich ecosystems.

Oxathiapiprolin Alone or Mixed with Metalaxyl Seed Treatment for Management of Soybean Seedling Diseases Caused by Species of Phytophthora, Phytopythium, and Pythium.

Species of Phytophthora, Phytopythium, and Pythium affect soybean seed and seedlings each year, primarily through reduced plant populations and yield. Oxathiapiprolin is effective at managing several foliar diseases caused by some oomycetes. The objectives of these studies were to evaluate oxathiapiprolin in a discriminatory dose assay invitro; evaluate oxathiapiprolin as a soybean seed treatment on a moderately susceptible cultivar in 10 environments; compare the impact of seed treatment on plant populations and yields in environments with low and high precipitation; and compare a seed treatment mixture on cultivars with different levels of resistance in four environments. There was no reduction in growth invitro among 13 species of Pythium at 0.1 µg ml-1. Soybean seed treated with the base fungicide plus oxathiapiprolin (12 and 24 µg a.i. seed-1) alone, oxathiapiprolin (12 µg a.i. seed-1) plus mefenoxam (6 µg a.i. seed-1), or oxathiapiprolin (24 µg a.i. seed-1) plus ethaboxam (12.1 µg a.i. seed-1) had greater yields in environments that received ≥50 mm of precipitation within 14 days after planting compared with those that received less. Early plant population and yield were significantly higher for seed treated with oxathiapiprolin (24 µg a.i. seed-1) + metalaxyl (13.2 µg a.i. seed-1) compared with nontreated for six of seven cultivars in at least one of four environments. Oxathiapiprolin combined with another Oomycota fungicide applied to seed has the potential to be used to protect soybean plant establishment and yield in regions prone to poor drainage after high levels of precipitation.

Yields of Promising Sugarcane Clones under Three Different Planting Arrangements

A field experiment was conducted at Kediri, East Java, to examine the influence of row spacing on the yield of five promising clones from August 2018-June 2020. The investigation was of a Split-Plot design with three replications. The main plot consisted of three planting arrangements: SR, single row spacing at 110 cm, DR1, double rows spacing 50+135 cm, and DR2, double rows spacing 50+170 cm. Sub-plots consisted of five promising clones and one check variety: MLG 5, MLG 9, MLG 14, MLG 52, MLG 55, and PS 881. The results suggest no overall significant effect of planting arrangement on sugar yield, though clones may vary. There are significant differences in yield between some clones. Wider rows, DR2, show the highest yield in tonnes of cane per hectare (TCH) in PC (153.94 t/ha) with a slight decrease (14%) in RC-1 due to reduced plant population. Sugar yield in tonnes of sugar per hectare (TSH) in various planting arrangements ranges from 12.26-13.99 t/ha in PC and 10.68-11.93 t/ha in RC-1. MLG 9 can be released as a new variety with high cane and sugar yields.

Modification of soybean plant architecture through growth regulators and population variation

An important limitation to increased soybean [Glycine max (L.) Merr.] grain yield is excessive plant growth. The use of growth regulators and population adjustment is imperative for the management of soybean. This study aimed to evaluate whether lactofen, used as a growth regulator, and a reduction in plant population affected the architecture of soybean and increased its production efficiency. The study was carried out under field conditions during the 2017–2018 and 2018–2019 seasons. The experimental design was in completely randomised blocks with five treatments and five replications: T1 (control), T2 (application of 140 g a.i. ha−1 of lactofen at phenological stage V3), T3 (application of 140 g a.i. ha−1 of lactofen at phenological stage V6), T4 (plant population 20% lower than recommended) and T5 (plant population 40% lower than recommended). The plant height, the number of nodes, the number of branches, stem diameter, and the internode distance were affected by lactofen application at stage V3. Lactofen use at stage V3 also increased the coverage percentage and the number of droplets per square centimetre of phytosanitary products. The interception of solar radiation was higher with lactofen application at stage V3 and that treatment provided the highest yield. Therefore, the use of lactofen as a growth regulator improves soybean grain yield. A reduction in plant population had the greatest effect on grain number and weight. Plant density should be maintained as recommended to avoid a decrease in grain yield

Dragging a manure hose over corn at early growth stages does not reduce yield

AbstractSidedressing corn (Zea mays L.) with liquid manure slurry via a manure hose application system was recently shown to be a viable practice to apply manure to a growing crop. However, little is known about what growth stage different corn hybrids can be dragged with a manure hose before plant population and grain yield is affected. A small‐plot field study was conducted in 2019 and 2020 at both Saint Paul and Waseca in Minnesota to evaluate the effect of dragging a manure hose over corn on plant population, grain yield, and grain moisture of two hybrids with different mid‐season brittle stalk ratings (Pioneer P0339R and P0306AM). Plots were dragged in both directions along the row with a manure hose from the first through sixth leaf collar growth stages (vegetative [V] growth stage V1 through V6) and compared to a non‐dragged control. Plant population, grain yield, and grain moisture were generally not significantly affected by dragging corn between the V1 and V3 (third leaf collar) growth stages. Dragging at V4 reduced plant population and yield by 41% in 1 of 4 site‐years, while dragging after V5 significantly reduced yield by 21–79% and in most cases, increased grain moisture. Yield did not differ between hybrids in any site‐year except in Waseca 2019 when a July windstorm disproportionately affected hybrid P0306AM more than P0339R. These results suggest that when using a manure drag hose application system to sidedress corn, sidedressing should be completed before V4 to avoid damaging the crop, regardless of hybrid.

Liquid swine manure as a sidedressed nitrogen source for corn

AbstractSidedressing liquid swine (Sus scrofa) manure (LSM) on corn (Zea mays L.) may provide additional time to apply manure and help better match crop‐nutrient demand with nutrient supply. A 2‐yr, on‐farm study was conducted in Minnesota to assess three sidedress nutrient sources—injected LSM via dragline hose, anhydrous ammonia (AA), and urea ammonia nitrate (UAN)—against a non‐sidedressed control. At planting, all treatments (including the control) received 46 kg N ha−1 as starter fertilizer. At sidedressing, 157 kg N ha−1 of available N was targeted for application with the different N sources at the fourth leaf collar stage of corn (V4). Sidedressing did not affect plant population compared with the non‐sidedressed control in 2018, but sidedressed LSM reduced plant population by 6% relative to the control in 2019, likely due to wet soil conditions and manure injection settings that partially buried plants. In 2018, LSM produced comparable grain yield and net return to sidedressing costs as AA and UAN, despite lower soil ammonium and nitrate levels in the 0‐ to 15‐cm soil layer approximately 12 d after application. In 2019, LSM led to 18–25% lower grain yield than AA and UAN and lower net returns because of a combined plant population reduction and an application of 50 kg plant available N ha−1 less than expected. Sidedressing corn with LSM is a viable alternative to commercial fertilizers, although to realize consistent results, better fine‐tuning of application rate, depth, and speed under different soil moisture conditions may be needed.

Management of plant architecture, spacing and population on the yield of super early common bean

For efficiency in the use of production factors and maximization of the yield of cultivars, it is essential to determine the most appropriate spatial arrangement for each cultivar and environment. This study identifies the effects of artificial adjustment of plant architecture, spacing between rows, and plant population on the yield of the super early common bean cultivar BRS FC104. We conducted the experiment in randomized blocks with subdivided plots and three replicates. In the plots, we assessed the spacing between rows (22.5, 45.0, and 67.5 cm). In the subplots, we considered the levels of artificial adjustment of plant architecture (maintenance of one or three lateral branches and control without architecture adjustment). In the subsubplots, we assessed populations of 6, 11, 16, and 21 plants per meter. The number of pods per plant increased with the increase in spacing between rows and with the reduction in plant population. Grain weight, in turn, increased with the reduction in spacing between rows and with the increase in plant population up to 14.7 plants per meter. Regarding grain yield and seed economy, the most suitable spatial arrangement for the super early cultivar consists of a 22.5 cm spacing between rows with about 12 plants per meter. The change in plant architecture, with the removal of lateral branches, is not effective to maximize yield.

Response of Plant Spacing and Balanced Fertilization on Growth and Yield of Maize (Zea mays L.) in Red Laterite Zone of Purulia District of West Bengal

The experiment was conducted at Krishi Vigyan Kendra Kalyan, Purulia adopted village namely Jambad in Purulia District of West Bengal during kharif season of 2019. The experiment was laid out in nine strip plots with plot size of 48 sq m2. m including three different doses of Nutrients viz. N: P2O5:K2O - 120:60:60, 150:60:60 and 150:75:60 at densities comprising of 55,555 plants/ha (60 X 30 cm), 66,666 plants/ha (60 X 25 cm) and 83,333 plants/ ha (60 X 20 cm) by using of four row multi-crop planter with the objective of observing the effect of plant spacing on yield attributes and yield of maize hybrids. The yield attributing factor as cob length was determined and initially the yield was recorded for application of different doses of nutrients. In case of plant spacing with the optimum doses of nitrogen and phosphorus the only factor contributing to increase in grain yield per unit area was the number of plants grown in the area, so the maximum grain yield (7.5 t/ha) was obtained at (60 X 20 cm) spacing with application of nutrient doses of 150:75:60. Drastic reduction in grain yield occurred at wider plant spacing i.e. (60 X 30 cm). It was due to the reason that increase in cob length did not occur proportionately to the reduction in plant population.

Seed Distribution Mechanisms and Sowing Speed on Plantability and Agronomic Characteristics of Sunflower

Precision in sowing is an important strategy for increasing agricultural yield. The objective of this study was to evaluate the influence of seed distribution mechanisms and sowing speeds on characteristics of sunflower. The experiment was set in March 2015 in São José do Rio Claro, state of Mato Grosso (Brazil). The experimental design was a completely randomized block design, in a 2 × 5 factorial arrangement, with two seed distribution mechanisms (perforated and pneumatic disc) and five sowing speeds (4; 6; 8; 10 and 12 km h-1) with four repetitions. The vegetative and reproductive characteristics of the sunflower were evaluated and also the double, faulty and acceptable spacing were evaluated to observe the homogeneity of seed distribution through the sowers. Regardless of the seed distribution mechanism, the rise in the sowing speed caused a reduction in plant population by changing plant height, head height, head mass, achene mass per head, mass of one thousand achenes and head diameter. The perforated disk distribution mechanism showed the best performance in acceptable spacings and the pneumatic one provided a greater guarantee of the desired plant population. The different distribution mechanisms, as well as different sowing speeds, did not influence achenes yield. The farmer should be aware of the speed of sowing adopted in his sunflower crop, as increasing speeds may affect uniform seed distribution as well as plant development.

Seed‐Drill Opener Type and Crop Residue Load Affect Canola Establishment, but Only Residue Load Affects Yield

Core Ideas Canola establishment can be affected by the residues of the previous crop.Different planting tools may handle crop residue differently.Tine and disc furrow openers at different residue loads were tested.Canola performed best when established with tine openers and when residue load is low. Handling crop residue during planting operations is a challenge to conservation agriculture (CA) farmers worldwide. It remains unclear which tools are most effective in which conditions. Canola (Brassica napus L.), an oilseed crop widely used in rotation with cereals, is particularly sensitive to seedbed conditions, and thus may be influenced by residue loads and the choice of seed‐drill openers. To identify optimal planting practices, this study compared the performance of disc and tine openers on canola establishment, growth, and yield under differing residue loads in a Mediterranean‐type climate region. First, soil disturbance caused by disc and tine openers was evaluated to assess their effect on seedbed conditions; and second, the interacting effects of the openers with different residue loads was investigated. Tine openers and low crop residue loads resulted in the best (P < 0.05) canola establishment. However, canola at reduced plant populations compensated in both biomass and grain yield, so that no yield differences resulted from different opener types, and only small yield differences occurred between residue loads (P > 0.05).

Componentes agronômicos do feijoeiro superprecoce BRS FC104 em diferentes arranjos espaciais e adubações fosfatadas

The adequate combination of row spacing with the number of plants per meter in front of different edaphoclimatic conditions is fundamental to obtain greater common bean yields. This work aimed to identify the best spatial arrangement and dose of monoammonium phosphate (MAP) to maximize the productive potential of very early BRS FC104 common bean cultivar. The experiments were conducted in Formosa, Cristalina, Santa Helena de Goias and Santo Antonio de Goias, Goias, in a randomized block design with split plots and four replications. In the plots, five doses of MAP, 100, 150, 200, 250, and 300 kg ha-1, and, in the subplots, five plant populations, 6, 8, 10, 12, and 14 plants per meter were evaluated. Two experiments were carried out in each locality, one at 0.38 m spacing and another at 0.50 m spacing. The number of pods per plant was the grain yield component most affected by the spatial arrangement of plants, increasing its value with the increase in row spacing and the reduction in plant population, in all locals. The response of common bean yield to row spacing was variable, depending on the local and the dose of MAP. The plasticity of the grain yield components kept the common bean yield stable in relation to changes in the plant population, in all locals, except in Santa Helena de Goias, where greater grain yield was obtained with about 14 plants per meter. Phosphate fertilization increased common bean yield in Santo Antonio de Goias.

Upland Cotton Growth and Yield Response to Enhanced Inputs Across the Mid-south and Southeast Cotton Belt

In addition to cost of seed and agrichemicals, cotton growers are often enticed to apply additional inputs in the quest for plant health. It is not known, however, whether these additional inputs are cost effective. The objectives of this study were to evaluate current extension recommendations compared to several additional inputs on yield and economic gain. In addition, differences in plant populations, plant heights and thrips damage were assessed. Additional inputs included enhanced soil fertility, in-furrow and foliar fungicides, in-furrow insecticide, and late foliar applied potassium. Each of the inputs was included as an individual treatment, a combined treatment with all five inputs, and a control treatment based on each state’s extension recommendations in the trial. Each treatment was included at both an early and late planting date from 2014 through 2016 in Missouri, Mississippi, North Carolina, and Virginia. No additional inputs increased fiber yield or economic gain significantly compared to the controls. Plant populations and plant heights at five weeks after planting (WAP) were not influenced by inputs except for a reduction in plant population of the 150% fertility treatment when compared to local extension recommendations in 2016. Thrips injury rating at three WAP was reduced by treatments including the in-furrow insecticide compared to the control in two of three years in both North Carolina and Virginia The data indicate that these additional inputs are for use under specific circumstances or thresholds and should not be used as a blanket agronomic treatment in the name of plant health.

Cotton Growth and Yield Response to Short-Term Tillage Systems and Planting Date in North Carolina

Tillage practices, cover crops, and planting dates can influence soil moisture and temperature conditions at planting and cotton (Gossypium hirsutum L.) stand establishment and yield. A study was conducted in North Carolina at two locations from 2014 through 2016. Treatments included six tillage systems of fall and spring conventional raised beds and flat strip tillage planted in early and late May, with and without a wheat (Triticum aestivum L.) cover crop. Tillage treatments include conventional spring raised beds, fall strip till, stale seedbed, at-plant strip till, pre-plant strip till, and stale seedbed with at-plant strip till. Except for fall strip tillage, no tillage systems reduced plant populations compared to conventionally tilled cotton in any environment. Crop growth rates were similar in conventional and spring strip-till systems and were lower in four planting date environments with stale seedbeds. In 2016, in-row soil resistance was measured from 0- to 30-cm depth using a conical penetrometer both at planting and post-harvest. Plots without any spring tillage had the greatest soil resistance for all measurements and depths. All plots with spring tillage had similar soil resistance to at least the 15-cm depth from which point the conventional spring beds had the least soil resistance through the 30-cm profile. Late planted cotton in 2014 showed inconsistent yield differences among tillage systems between locations. When pooled over location and year for 2015 and 2016, however, tillage system did not influence cotton yield. These data indicate that cotton yields in reduced-till systems are comparable to cotton grown in conventional systems in North Carolina soils.

Determination of a plant population density threshold for optimizing cotton lint yield: A synthesis

Technology fees associated with modern cotton cultivars have increased seed costs considerably, giving producers the impetus to reduce plant population density, where possible. Most recent studies on cotton population density, conducted across diverse environments, report similar patterns of crop response: decreases in lint yield only at very low densities, with generally consistent yield across all higher densities. But no work had been done to bring the literature together, quantitively synthesizing the yield data collectively, to better pinpoint a population density threshold. And, notably, little had been reported on the effects of population density in lower-yielding dryland environments. Quantitatively synthesizing population density datasets from the literature, including our own dryland data, was the objective of this research. The dryland data showed that lint yield and biomass partitioning were not affected by population density, similar to higher-yielding environments over the same range in density. Following normalization of all lint yield data (literature and dryland datasets), a breakpoint in population density at 35,000 plants ha−1 was identified, which can be interpreted as the minimum plant density at which yield may be optimized. This rate is lower than the common density recommendation of 81,000 plants ha−1 and substantially lower than the risk-averse rates at which many producers plant (129,000 seeds ha−1 or greater). The analysis showed that yield will decline precipitously below 35,000 plants ha−1, exposing the enormous risk to cotton producers in approaching this low density, particularly if significant seed or plant loss is expected. However, the analysis suggests that excessive over-seeding may be occurring in many cases, resulting in economic losses to producers. The analysis also provides guidance on a threshold for producers facing replanting decisions.

Challenges and Prospects for Building Resilient Disease Management Strategies and Tactics for the New York Table Beet Industry

The New York table beet industry is expanding and has unique challenges to minimize crop loss in both conventional and organic production. Diseases may reduce plant population density and increase heterogeneity in a stand, reduce the duration of time foliage is healthy, and decrease the yield of marketable roots. Rhizoctonia solani Kuhn and Pythiumultimum Trow are dominant in the pathogen complex affecting crop stand and root health. Cercospora leaf spot (CLS) caused by the fungus, Cercospora beticola Sacc., is a highly destructive disease affecting foliar health. In conventional table beet production, fungicides are applied in-furrow and at emergence for early season and root disease control, and applied to foliage periodically thereafter for foliar disease control. Resistance within C. beticola populations to single-site mode-of-action fungicides poses the most significant threat to the resilience of conventional disease management. An integrated approach to reduce pesticide application when not economically warranted (i.e., a false positive) is urgently required. For foliar disease, improved scheduling of fungicides may reduce usage without loss of disease control. For soilborne diseases, pre-plant quantification of soilborne inoculum may support the selection of fields with lower inoculum densities to minimize risk of early season and root disease. For organic production, some approved products have moderate efficacy for foliar disease control, but strategies to reduce inoculum and select fields at lowest risk of disease will be paramount. Crop rotation has shown promise for disease management, but broad host range of several of the major soilborne pathogens limits the utility of this method in the production region. Enhanced knowledge of cultivar susceptibility to local populations of fungal pathogens responsible for foliar and root diseases is paramount, and adoption of commercially acceptable cultivars with improved resistance to CLS and Rhizoctonia crown and root rot has potential to transform disease management strategies for the New York table beet industry.

Soybean Yield Response to In‐furrow Fungicides, Fertilizers, and Their Combinations

Core Ideas Fungicide in‐furrow and starter fertilzer individually did not increase yield. Fungicide and starter fertilizer combined in‐furrow increased yield marginally. Fungicide and starter fertilizer in‐furrow may not be economical without disease. Planting into cool and wet conditions exposes soybean [Glycine max (L.) Merr.] seed and seedlings to pathogens that may reduce plant populations, resulting in lower yield. Recently, fungicides have been labeled for in‐furrow applications and marketed to provide additional broad‐spectrum protection from soilborne fungi and enhance seedling vigor. Additionally, liquid fertilizers have been promoted recently as a carrier for fungicides to improve yield in some soybean producing areas in the United States. The objective of this study was to evaluate the effect of a fungicide, starter fertilizer, and a combination of fungicide and starter fertilizer on soybean yield. Field experiments were laid out in Arkansas, Indiana, Iowa, and Mississippi in the United States and Ontario, Canada, with a total of 14 site‐years. A positive yield response was observed with the fungicide and starter fertilizer treatment combination in Arkansas in 2014; however, there was no effect of treatment on soybean yield at any other location or year. Overall, a yield benefit of 1.6 bu/acre (107.6 kg/ha) (P = 0.02) with the fungicide and starter fertilizer treatment was observed across all locations when combined using meta‐analysis. In conclusion, our study suggests that the prophylactic application of fungicide and starter fertilizer may not be profitable without the risk of soilborne diseases and nutrient deficiencies.

Impact of fluopyram fungicide and preemergence herbicides on soybean injury, population, sudden death syndrome, and yield

Field experiments were conducted in Indiana and Iowa in 2014 and 2015 to examine the effect of preemergence herbicides and fluopyram seed treatment on soybean (Glycine max (L.) Merr.) injury, plant population, sudden death syndrome (SDS; Fusarium virguliforme O'Donnell & T. Aoki), and yield. Sulfentrazone + cloransulam-methyl + S-metolachlor and flumioxazin + chlorimuron ethyl + S-metolachlor herbicides resulted in higher phytotoxicity at growth stage VC-V1 compared to a non-treated control. Phytotoxicity due to preemergence herbicide was rarely observed at V4. Seed treated with fluopyram resulted in higher phytotoxicity at VC-V1 than seed without fluopyram, regardless of preemergence herbicide treatment. The combination of preemergence herbicide and fluopyram did not increase the severity of soybean injury in any year or location compared to either applied alone. Preemergence herbicide treatment reduced plant population in Indiana in 2014 and Iowa in 2015 compared to the non-treated control, but did not affect yield. Fluopyram seed treatment reduced foliar symptoms of SDS by over 70% and increased yield up to 12% in Indiana, but had no effect on SDS or yield in Iowa. These results indicate that while injury can occur with both preemergence herbicides and fluopyram-treated seed, phytotoxicity is not more severe when both pesticides are used together, and yield is not reduced by their use. Farmers should continue to use preemergence herbicide programs if they treat their seed with fluopyram to manage SDS, and use production practices that minimize the risk of preemergence herbicide injury in soybean.

Evaluasi Ketahanan Sumber Daya Genetik Kedelai terhadap Cekaman Salinitas

Soybean (Glycine max (L.) Merr.) is sensitive to salinity stress. The availability of soybean cultivar tolerant to salinity stress is the main key of succeeding of soybean cultural practice on saline affected land. Objective of the research was to evaluate the resistance of soybean germplasms to salinity stress. The research was conducted on saline affected soil in Lamongan District during the dry season (May-August) 2016. Nineteen soybean genotypes that were selected from previous salinity test in the green house were reevaluated in the field using a randomized block design with three replications. Wilis cultivar (sensitive to salinity) used as check. Variable observations consisted of soil properties before planting, number of plant grow at 13 and 41 days after sowing (DAS), plant height at 41, 56 and 71 DAS, chlorophyll content index at 27, 41 and 56 DAS, soil EC at 71 DAS, number of harvested plants, yield and yield components. The results showed that among 19 genotypes tested, only five genotypes that survived up to harvest with plant population 30-50% at high salinity level. Salinity reduced plant population more than 50%, and plant height only 50% from its normal height. Based on soil EC, plant population at harvest, and yield, genotype Karat 13, Grayak 3 and Grayak 5 were identified adaptive to high salinity level with soil EC 11,7-14,4 dS/m, while MLGG 0160 were identified adaptive to moderate salinity level with soil EC up to 9,1 dS/m.

Persisting in defaunated landscapes: Reduced plant population connectivity after seed dispersal collapse

Abstract Defaunation of large‐bodied frugivores could be causing severe losses of crucial ecosystem functions such as seed dispersal. The immediate ecological consequences may include alteration or even collapse of seed‐mediated gene flow affecting plant population connectivity, with impacts on the regional scale distribution of genetic variation. Yet, these far‐reaching consequences of defaunation remain understudied. Here, we tested whether human‐induced defaunation of the Canarian frugivorous lizards (Gallotia, Lacertidae) altered within‐island population connectivity and the amount and large‐scale distribution of genetic variation of Neochamaelea pulverulenta (Rutaceae), which relies exclusively on these lizards for seed dispersal. Our study system defines a lizard downsizing gradient with three contrasted ecological scenarios (islands) with relatively optimal (Gran Canaria; large‐sized lizards), suboptimal (Tenerife; medium) and collapsed seed dispersal processes (La Gomera; small). We extensively sampled individual plant genotypes from 80 populations spanning the full geographical range of the plant to examine their genetic diversity, population‐genetic network topologies, and the patterns of isolation both by distance (IBD) and resistance (IBR) across these three ecological scenarios. Plant genetic diversity appeared unaffected by defaunation‐mediated downsizing of frugivorous lizards. However, we found a reduced overall plant population connectivity together with an increased isolation by distance within the most defaunated islands (La Gomera and, to a lesser extent, Tenerife) when compared with the scenario preserving the functionality of lizard‐mediated seed dispersal (Gran Canaria). The results, with a significant effect of lizard downsizing, were robust when controlling for biotic/abiotic differences among the three islands by means of isolation by resistance models (IBR). Synthesis. Our results provide valuable insights into the far‐reaching consequences of the deterioration of mutualisms on plant population dynamics over very large spatial scales. Conservation of large‐bodied frugivores is, thus, essential because their irreplaceable mutualistic dispersal services maintain an extensive movement of seeds across the landscape, crucial for maintaining the genetic cohesiveness of metapopulations and the adaptive potential of plant species across their entire geographical range.

Time Interval Between Cover Crop Termination and Planting Influences Corn Seedling Disease, Plant Growth, and Yield.

Experiments were established in a controlled-growth chamber and in the field to evaluate the effect of the length of time intervals between winter rye cover crop termination and corn planting on corn seedling disease, corn growth, and grain yield in 2014 and 2015. Rye termination dates ranged from 25 days before planting (DBP) to 2 days after planting (DAP) corn in the field and from 21 DBP to 1 DAP in controlled studies. Results were similar in both environments. In general, shorter intervals increased seedling disease and reduced corn emergence, shoot growth, and grain yield of corn following winter rye compared with corn planted 10 or more days after rye termination or without rye. Incidence of Pythium spp. increased with shorter intervals (less than 8 DBP); incidence of Fusarium spp. was not consistent between runs and experiments. In 2014, in the 1-DAP treatment, number of ears and grain yield were reduced (P = 0.05 and 0.02, respectively). In 2015, all termination intervals reduced plant population, number of ears, and yield (P = 0.01), with the 2-DBP treatment causing the biggest decrease. A 10- to 14-day interval between rye termination and corn planting should be followed to improve corn yield following a rye cover crop.