Reduced Row Spacing Research Articles

Row spacing, seeding depth, seeding rate, and trinexapac‐ethyl effects on oat yield and lodging

AbstractLodging can reduce the yield and quality of oats (Avena sativa L.). Root lodging, as opposed to stem lodging, is the predominant form of lodging in oats. Therefore, identifying management practices that enhance root lodging resistance should be prioritized. The objective of this study was to investigate the effect of four management practices on oat grain yield, yield components, grain quality, observed lodging, and plant traits that contribute to root lodging resistance. Row spacing and seeding depth were tested in three oat cultivars across two environments in Ontario, Canada. Seeding rate and the application of the plant growth regulator trinexapac‐ethyl (TE) at different nitrogen (N) fertilizer rates were tested in two‐to‐three oat cultivars across four environments. Lodging occurred naturally in all environments, with root lodging always occurring, sometimes in combination with stem lodging. Under high lodging pressure, shallow seeding increased lodging. Similarly, lodging increased with greater seeding rates when lodging pressure was high. Reducing row spacing had no effect on lodging but was the only management practice to consistently increase grain yield. TE reduced lodging in some environments, especially as N rates increased. Root plate spread, root plate depth, and root safety factor were minimally affected by the management practices studied and had complex interactions with genotype and environment. Among the measured crop traits, plant height had the strongest and most consistent relationship to observed lodging.

Row spacing and phosphorus use efficiency in no-tillage maize

Reduced row spacing has shown to increase maize (Zea mays L.) nitrogen (N) use efficiency, but little is known about it effects on phosphorous (P) use efficiency (PUE). The objective of this study was to evaluate the PUE of maize under reduced row spacing and varying N regimes. No till maize was grown in Balcarce, Argentina, during two growing seasons using three rows spacing (35, 52, and 70 cm) and three N rates (0, 90, and 180 kg N ha−1). Shoot dry matter (DM), grain yield, and accumulated P content were determined. At V6 and R6 growth stages, the P use efficiency (PUE = g aboveground DM or grain yield per g P available) and it components P utilization efficiency (PUTE = g aboveground DM or grain yield per g P uptake), and P uptake efficiency (PUPE = g P uptake/g P available) were determined. N rate and narrower rows increased total DM, grain yield, and accumulated P content. Phosphorous concentration, PUTE, PUPE and PUE were not affected by row spacing or N rate. The present study showed that row spacing did not affect P use efficiency in no till maize when the soil P availability was adequate.

Water Availability and Row Spacing Effects on Nitrogen Use Efficiency in No-Till Maize

Reduced row spacing has shown to increase nitrogen use efficiency (NUE) in no-till irrigated maize; however available information in rainfed conditions is scarce. The objective was to analyze row spacing effects on NUE under different water and nitrogen (N) regimes. Maize crops were grown at Balcarce, Argentina, during two seasons. Treatments included two water regimes (rainfed and irrigated), two rows spacing (35 and 70 cm) and two N rates (0 and 180 kg N ha^-1).

Weed Community in Soybean Responses to Agricultural Management Systems

Weed infestation is a major cause of the poor yield of soybeans (Glycine max (L.) Merr.); therefore, proper weed management represents one of the most important and expensive steps in soybean production. Field experiments were established in northeastern parts of Croatia, in the Vukovar-Syrmia county from 2014 to 2016, arranged in a split-plot design with four replications. Two different studies were conducted: the first study was to determine the weed interference, weed biomass accumulation, yield, and yield components of soybeans growing in three different rows spacing (25, 50, and 70 cm), and the second study aimed to simulate a risk analysis by building models of probabilities for generating profit as a result of weed control. The weed community in soybean during the study period comprised 34 dicot and grass species of a varied perennation. Compositional differences in the weed community tended to be affected most by the year (humid–arid environment), followed by row spacing. There were no differences in the weed biomass accumulation with a reduction in row spacing from 70 to 50 and 25 cm. The dominant weed species Amaranthus retroflexus, Ambrosia artemisiifolia, Chenopodium album, Datura stramonium, Setaria viridis, and Sorghum halepense formed the main biomass and were spread over all row spacings. There was a significant influence of row spacing, the duration of weed interference, and year on soybean yield and yield components. Weed infestation until the second trifoliate (V2) stage had no detrimental effect on soybean yield, regardless of the row spacing. The number of pods per plant significantly decreased at the same V2 stage in 25 and 50-cm rows, but in 70-cm soybean rows, this process started later, at four unfolded trifoliate leaves (V4 stage). A 1000 kernel weight was less sensitive to weed infestation and was significantly decreased at full flowering (R2 stage) in 25 and 70 cm rows, while it already decreased at the V4 stage in 50 cm rows. The probability distribution of achieving a profit showed the best results for soybeans growing in 70 cm rows, with preemergence herbicide application and two inter-row cultivation.

Effects of strip cropping with reducing row spacing and super absorbent polymer on yield and water productivity of oat (Avena sativa L.) under drip irrigation in Inner Mongolia, China

With the serious shortage of water resources and the development of water-saving agriculture, the application of drip irrigation has been paid more and more attention. But there was lack of oat planting methods suitable for drip irrigation, currently. In order to establish an efficient oat planting method for drip irrigation, a study was conducted at Agriculture and Forestry Sciences of Ulanqab, Inner Mongolia during the season (2019–2020) to evaluate the effect of strip cropping with reducing row spacing and super absorbent polymer on the yield and water use efficiency of oat. To conduct the field trials, a split plot system in three replications was established. Three planting patterns were in the main plots, including conventional cropping with 20 cm equal row spacing (PA), strip cropping with the 15 cm row spacing (PB) and strip cropping with the 10 cm row spacing (PC), and two super absorbent polymer levels were in the subplots, including 22.5 kg ha−2 (Y) and 0 (N). The results showed that, compared with PA, PB and PC both decreased the irrigation volumes by 4.5–18.4 mm, and the irrigation volumes of PB was lower than that of PC. When super absorbent polymers were applied, compared with PA, PB significantly increased grain yield and above-ground biomass, but PC had the opposite effects. The grain yield and above-ground biomass of PB significantly increased by 16.65% and 7.31% on average in two years, respectively. And the increasing of grain yield was attributed by the significant increasing of pike number and kernel number per spike. But when super absorbent polymers were not applied, PB had no significant effects on grain yield and above-ground biomass. PB also had the significant effects on regulating water use of oats weather or not super absorbent polymers were applied, it significantly increased the precipitation ratio by 2.64% (PBY) and 2.13% (PBN) and decreased irrigation ration by 3.32% (PBY) and 5.28% (PBN) on average in two years. Although PB and PC both decreased the total evapotranspiration, but PB increased WUE and PC deceased WUE. The WUE of PB increased by 19.70% (PBY) and 9.87% (PBN) on average in two years. Also PB had the highest economic benefits in all treatments. In conclusion, a drip irrigation oat planting pattern was proposed, which the row spacing is 15 cm, adjusted the equal row spacing planting to 8-row strip planting, with a belt spacing of 30 cm, combined with the application of 22.5 kg ha−2 applying super absorbent polymers. And this oat planting pattern is a viable strategy to improve oat productivity.

Response of Maize, Cotton, and Soybean to Increased Crop Density in Heterogeneous Planting Arrangements

The reduction of row spacing and increase of crop population density are important tools for maximizing crop yield. For this strategy to be effective, the crop population should not create intraspecific crop competition that penalizes yield. Thus, planting arrangements that increase light interception throughout the canopy without increasing row spacing might be needed to maintain yield. In this study, heterogeneous planting arrangements on evenly spaced rows were analyzed for maize (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean (Glycine max (L.) Merr.). Each crop had four planting arrangements: (1) normal density in all rows, considered the control, (2) doubled density in all rows, (3) a sequential arrangement of normal and tripled densities (each in every other row; NTNT), and (4) normal-tripled-tripled-normal (NTTN). Maize and cotton did not exhibit changes in growth and architecture when comparing uniform and variable planting arrangements. Soybeans were more adaptable and increased biomass production by 44% to 45% in variable arrangements. None of the crops showed differences in yield due to planting arrangement, so the use of rows with different densities might not be needed when using high densities to maximize yield.

Trinexapac-ethyl application time in the crop corn agronomic performance grown under different plant arrangements

Reduced row spacing promotes more uniform spatial distribution of plants in the field. However, the adoption of reduced row spacing only is possible with smaller plants, which may be obtained with the use of plant growth regulator. This study aimed to evaluate the agronomic performance of the first corn crop with Trinexapac-ethyl applied at the different plant development stages and grown under different row spacing, with the same plant population. The experiments were arranged in a split-plot randomized block design with four replications, with row spacing for the plots (0.45 and 0.90 m) and Trinexapac-ethyl (TE) application time to subplots (control without application, at the V3, V6, V9 and V12 phenological stages). The Trinexapacethyl application time interacted with row spacings changing the growth and yield performance of the corn crop. For 0.45 m spacing Trinexapac-ethyl application at V12 and for 0.90 m spacing application at V9 and V12 reduced plant height and ear height. Trinexapac-ethyl application at V9 for both row spacings changed the plant architecture without changing the ear length and grain yield.

Reduction of interrow spacing in cassava (Manihot esculenta Crantz) production

The interrow spacing commonly used in cassava cultivation in Brazil, especially in the Agreste region of Alagoas, ranges from 100 to 120cm. However, the reduction in row spacing can provide agronomic and environmental benefits in cassava cropping systems. Thus, this work aimed to evaluate the performance of two cassava varieties cultivated with reduced interrow spacing. Two experiments were conducted in the field, one in 2015/16 and another in 2017/18. A Split Plot design with four replications was used in both experiments. Four interrow spacing were evaluated in the main plot: 60, 80, 100 and 120cm, with plants spaced 60cm apart within rows, giving populations of 27,778, 20,833, 16,667 and 13,889 plants per hectare, respectively. In the subplots, two cassava varieties were evaluated: Caravela and Pretinha. An increase in interrow spacing promoted a linear reduction in the stem green mass of cassava. Plant height, leaf green mass, main stem diameter, root yield, tuberous root length, tuberous root diameter, flour percentage, flour yield, and starch content were not influenced by changes in interrow spacing. The Pretinha variety was superior to Caravela in the following evaluated traits: stem green mass, the diameter of tuberous roots, root yield, plant height, and flour yield. The results indicate the possibility of altering the interrow spacing in cassava to assist in the cultural management, without impacting crop yield.

Row spacing and growth habit in peanut crops: Effects on seed yield determination across environments

Narrowing row spacing was expected to improve peanut crop performance, but the responses varied depending upon the evaluated environment and the growth habit of the plant. To clarify apparent inconsistencies, two cultivars with contrasting growth habits were sown at 52 cm and 70 cm row spacings in field experiments carried out in four environments. Vegetative and reproductive traits were evaluated. The leaf area index was always higher in the 52 cm than in the 70 cm row spacing, independently of the growth habit. Similarly, the light attenuation coefficient ( k ) was higher under narrow than under wide rows, but the cultivar with procumbent growth habit had a larger k and increased slightly the intercepted radiation respect to the erect type. These responses of the procumbent cultivar were driven by its lateral arrangements towards neighboring rows and its longer cycle duration. Narrow rows contributed to intercept approximately 14% more radiation than wide rows. These responses determined an improved biomass production through increases in the crop growth rate during the pod set period, with subsequent increases of the radiation use efficiency of this phase. Narrow row spacing enhanced seed and pod yields independently of the growth habit, but the relative importance of each seed yield component varied between cultivars. Seed numbers were more relevant for the erect growth habit, concurrently with the marked increase in total flower numbers of this cultivar. Seed weight was more relevant for the procumbent growth habit. On one hand, the erect growth habit caused a larger relative variation in seed and pod yields across environments than the procumbent one, particularly at narrow row spacing. On the other hand, the erect growth habit showed the lowest yield under wide rows. The small differences in biomass production between growth habits but the large difference in harvest index (procumbent > erect) contributed to an enhanced and more stable seed yield of the procumbent type, particularly when grown under narrow rows and linked to the large seed size of the runner cultivar. Results suggest that farmers should consider reducing row spacing as a way to increase peanut yield in the region under analysis.

Breeding effects on canopy light attenuation in maize: a retrospective and prospective analysis.

The light attenuation process within a plant canopy defines energy capture and vertical distribution of light and nitrogen (N). The vertical light distribution can be quantitatively described with the extinction coefficient (k), which associates the fraction of intercepted photosynthetically active radiation (fPARi) with the leaf area index (LAI). Lower values of k correspond to upright leaves and homogeneous vertical light distribution, increasing radiation use efficiency (RUE). Yield gains in maize (Zea mays L.) were accompanied by increases in optimum plant density and leaf erectness. Thus, the yield-driven breeding programs and management changes, such as reduced row spacing, selected a more erect leaf habit under different maize production systems (e.g., China and the USA). In this study, data from Argentina revealed that k decreased at a rate of 1.1% year-1 since 1989, regardless of plant density and in agreement with Chinese reports (1.0% year-1 since 1981). A reliable assessment of changes in k over time is critical for predicting (i) modifications in resource use efficiency (e.g. radiation, water, and N), improving estimations derived from crop simulation models; (ii) differences in productivity caused by management practices; and (iii) limitations to further exploit this trait with breeding.

Response of leaf carbon metabolism and dry matter accumulation to density and row spacing in two rapeseed (Brassica napus L.) genotypes with differing plant architectures

Biological yield indicates the potential for increasing yield. Leaf carbon metabolism plays an important role in the biomass accumulation of rapeseed (Brassica napus L.). Field experiments with the hybrid HZ62 (with a conventional plant architecture) grown in 2016–2017, and HZ62 and accession 1301 (with a compact plant architecture) grown in 2017–2018 were conducted to characterize the physiological and proteomic responses of leaf photosynthetic carbon metabolism to density and row spacing configurations. The densities were set at 15×104 ha−1 (D1), 30×104 ha−1 (D2), and 45×104 ha−1 (D3) (main plot), with row spacings of 15 cm (R15), 25 cm (R25), and 35 cm (R35) (subplot). Individual and plant population biomass accumulation was greatest at R25, R15, and R15 for D1, D2, and D3, respectively, for both genotypes. In comparison with D1R25, the individual aboveground biomass of HZ62 decreased by 60.2%, whereas the population biomass increased by 31.9%, and the individual biomass of genotype 1301 decreased by 54.0% and the population biomass increased by 53.9% at D3R15. Leaf carbon metabolic enzymes varied between genotypes at flowering stage. In contrast to D1R25, at D3R15 the activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and sucrose phosphate synthase (SPS) and the contents of starch, sucrose and soluble sugars in leaves were significantly decreased in HZ62 and increased in genotype 1301. The activities of fructose-1,6-bisphosphatase (FBPase) decreased, in consistency with the abundance of fructose-bisphosphate aldolase in HZ62. In contrast, sucrose synthase (SuSy) activity appeared to decrease in both genotypes, but a significant increase in abundance of a protein with sucrose synthase was found in the 1301 genotype by proteomic analysis. With increased density and reduced row spacing, the expression of most key proteins involved in carbon metabolism was elevated, and enzyme activity and carbon assimilate content were increased in 1301, whereas HZ62 showed the opposite trend, indicating that the compact plant type can accumulate more population biomass with denser planting.

Features of growth of sorghum [Sorghum bicolor (L.) Moench] plants depending on the width of rows and seeding rate in the conditions of the Right-Bank Forest-Steppe of Ukraine

Purpose. To establish the optimal row spacing and so­wing rate of sorghum seeds of grain varieties ‘Dniprovskyi 39’ and ‘Vinets’, to substantiate their influence on the growing season and biometric parameters of plants in the Right-Bank Forest-Steppe of Ukraine. Methods. Field, laboratory, mathematical and statistical. Results. The most intensive growth and development of sorghum plants was observed when sowing seeds with a row spacing of 45 cm and a seeding rate of 200 thousand pieces/ha. In particular, the duration of the growing season under such conditions was the smallest: 108 days for the ‘Dniprovskyi 39’ variety and 106 days for the ‘Vinets’ variety. At the same time, the indicators of field seeds germination, plant height and stem diameter were maximum in the experiment: ‘Dniprovskyi 39’ – 88.7%, 137.3 cm and 1.7 cm, ‘Vinets’ – 86.9%, 121.8 cm and 1.6 cm, respectively. It was found that an increase in seeding rate reduced indicators of productive tillering, leaf area and weight per plant. The most intense tillering of sorghum plants was observed at a seeding rate of 150 and 200 thousand pieces/ha for all the studied variants of the row spacing: on average, up to two panicles well filled with grain per plant, depending on the varietal characte­ristics. At the rate of 250 thousand pieces/ha, tillering of plants in both varieties was somewhat weaker – 1.0–1.1 panicles per plant. The largest indicators of leaf surface area and weight of one plant were with a row spacing of 45 cm: 1528–2320 cm2 and 169.2–185.6 g in the variety ‘Dniprovskyi 39’ and 1476–2180 cm2 and 143.1–162.3 g in the variety ‘Vinets’ depending on planting density. Reduction of row spacing up to 15 cm and its increase up to 70 cm led to a decrease in the main parameters of plant growth and development. Conclusions. Sorghum plants developed better when sown with a row spacing of 45 cm and a seeding rate of 200 thousand pieces/ha, which were recommended for growing crops in the conditions of the Right-Bank Forest-Steppe of Ukraine.

Reduced row spacing improved yield by optimizing root distribution in maize

Roots play major roles in plant anchorage, water and nutrient uptake, crop growth and yield. Knowledge regarding yield responses to root spatial distribution is still limited in maize. Here we designed three plant densities in the tube and in the field, respectively. The tube study included plant densities of 1, 2, and 3 plants tube–1 and field study included 50025 (D50025), 67500 (D67500), and 100050 (D100050) plants ha–1, with two row spacings in D50025 (60 and 80 cm), three row spacings in D67500 (40, 60, and 80 cm), and two row spacings in D100050 (40 and 60 cm). With increased plant density and decreased row spacing grain yield improved, but root size and root biomass per plant decreased. Root dry weight per plant increased by 25–32 % at D50025 and decreased by 29–38 % at D100050 compared to D67500. Horizontally, reducing row spacing increased inner roots and reduced outer roots. There were significant correlations of yield with inner (R2 = 0.603** for D67500) and outer (R2 = −0.544* for D67500) root dry matter. Vertically, reducing row spacing increased root dry weight and most of the roots were distributed in the top 0–10 cm soil layer. Overall, high plant density inhibited root growth, but narrow row spacing compensated this inhibition to some extent by optimizing root distribution, thus increasing grain yield. Horizontal root distribution had a greater effect on grain yield than vertical distribution under high density condition, which alleviated inter-plant root competition and increased yield.

Agronomic Performance of Sugarcane in Reduced Row Spacing Grown from Different Billet Sizes Under No-tillage and Conventional Tillage System

For the need for expansion in the production of sugarcane, especially in regions that do not yet produce it significantly, there is a necessity for new studies in such areas, such as the cerrado-pantanal transition region. Therefore, the present study aimed to evaluate the agronomic performance of the crop through different soil management and billets sizes in the region. The experiment was conducted at the State University of Mato Grosso do Sul, in Aquidauana, Mato Grosso do Sul, in the 2012/2013 harvest. The design was in blocks with randomized treatments, in 2 × 3 subdivided plots, with treatments consisting of the combination of two soil management (no-tillage and conventional tillage systems) and three billet sizes (10, 20 and 40 cm), with four replications. The variety used was RB867515, and the variables analyzed were number of tillers, plant height, percentage of gaps, stem diameter, stem mass, productivity and total recoverable sugar. It was concluded that the use of billets of 20 cm in length positively influenced the vegetative development of sugarcane, but it did not translate directly into productivity. The planting system also did not directly influence the agronomic performance of the crop.

Effect of seeding rate and row spacing on the height of Medicago sativa plants

The purpose of the research was to identify the influence of cultivation technology elements on the parameters of Medicago sativa plant height of different geographical origin. Methods. Field, measurement, statistical methods. Research results. Observations showed that in the year of sowing during the vegetation of Medicago sativa its stalks were stunted and ranged within 28.0—33.3 cm irrespective of the seeding rate, varietal features and row spacing. In the second year of life in the budding phase, the plant growth rates of the varieties maintained throughout the growing season, whereas in the early flowering phase, they varied according to mowing and had a sinusoidal nature. The intensity of growth processes in the third year of life changed and in the budding phase of Medicago sativa it remained stable only in the first-second mowing ranging within 61.3—69.3 cm, whereas in the third-fourth mowing the indicators decreased from 59.1 up to 44.5 cm, or 10.2—16.8 cm. In the flowering phase, plant height was the highest in the first mowing and reached 99.7—101.4 cm, which decreased to 55.2 in the second and third mowing to 59.6 cm, or by 39.5—41.8 cm, regardless of the factors studied. Conclusions. The tendency towards the decrease in plant height with reduction of row spacing to 12.5 cm and increase of seeding rate and its growth at row spacing of 25 cm was revealed. The sinusoidal nature of Medicago sativa formation according to mowing both between the varieties and row spacing was established.

Economics of row spacing and integrated weed management in soybean (Glycine max L.)

The high cost of cultivation and weed management are major limiting factors to increasing soybean productivity and net returns. Field experiments were conducted in 2016 and 2017 at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta to evaluate the economic performance of different row spacings and integrated weed management system in soybean. Three row spacings (50, 75 and 100 cm) as the main plots and six weed control methods and a weedy check as sub-plot treatments were accommodated in a split-plot arrangement of a randomized complete block design with three replications. There was a significant reduction in weed biomass with a reduction in row spacing from 100 cm to 75 cm and 50 cm. Furthermore, the cost of production, grain yield and gross profit increased with a reduction in row spacing from 100 to 75 and 50. When soybean was sown at 50-cm row spacing, the application of Probaben 400EC (metolachlor 20% w/v + prometryn 20% w/v) or Butachlor 60EC (butachlor) at 2.0 kg a.i/ha each followed by supplementary hoe-weeding at 6 weeks after sowing (WAS) resulted in the highest yield of 2301-2484 kg/ha and total revenue of 2129-1972 $/ha. Conversely, three hoe-weedings resulted in the highest yield of 2155-2081 kg/ha and total revenue of 1848-1783 $/ha for crops grown at 75- and 100-cm row spacings. Despite the higher yield and revenue obtained with three hoe-weedings for crops grown at 75- and 100-cm row spacings, the gross profit and benefit-cost ratios obtained were lower than those obtained with herbicide treatments applied alone or followed by supplementary hoe-weeding. In terms of profitability, soybean planted at 50-cm row spacing and treated with Probaben 400EC at 2.0 kg a.i/ha followed by supplementary hoe-weeding gave the highest gross profit of 1479 $/ha. Two or three hoe-weedings in soybean planted at narrow-row (50 cm) spacing did not guarantee the highest yield, but rather increased the cost of weed control. This study suggests that narrow-row spacing (50 cm) and pre-emergence herbicides will help to reduce the number of hoe-weedings and consequently the high cost of production required for optimum yield and increase profitability in soybean production.

Intercropping Seedless Watermelon and Cotton

Intercropping of seedless watermelon [Citrullus lanatus (Thumb.) Matsum. & Nak.] and cotton [Gossypium hirsutum (L.)] in the eastern geographical area of South Carolina requires changes in normal crop-management programs but has the potential to improve grower profits compared with typical production of each crop separately. The alteration and timing of several normal crop-production practices for both crops can present challenges and must be well-defined for successful intercropping of watermelon and cotton in the region. Notable adjustments in production for watermelon are delayed planting date, reduced row spacing and bed width, and modification of herbicide applications. Significant changes in normal cotton production also include modification of herbicide applications, but additional considerations, such as temporal limits on side-dressed fertilizer and insecticide applications, are needed because of the raised beds and plasticulture used for watermelons and also because of labeling restrictions for pesticides across crops. Research was conducted to 1) identify modifications in standard crop-management procedures for watermelon and cotton intercropping; and 2) determine the feasibility and profitability of intercropping the crops. Although there was a slight numerical reduction in intercropped watermelon yield each year, there were no significant differences in total watermelon yield between intercropping and watermelon monoculture in any of the years. There were also no significant differences in watermelon fruit quality parameters (size, brix, hard seed, hollow heart) in any of the years. Intercropped cotton yield was significantly less than monoculture cotton yields in each of the three years. The net income from intercropping in each year was slightly less than the net income from watermelon monoculture.

Candidate Tools for Integrated Weed Management in Soybean at the Northern Frontier of Production

AbstractThe development of early-maturing soybean [Glycine max(L.) Merr.] varieties has led to an increase in soybean production in canola (Brassica napusL.)-dominant crop rotations in western Canada. Herbicide-resistant (HR) volunteerB. napuscan be difficult to manage in HR soybean using herbicides alone. In 2013 and 2014, four field experiments were conducted in Manitoba, Canada, to evaluate soybean row spacing, seeding density, nitrogen supply, and interrow tillage as candidate nonchemical weed management tools for an integrated program to manage volunteerB. napusin soybean. Among treatments and sites, volunteerB. napusproduced about 830 seeds plant−1and resulted in large seedbank inputs (averaging about 20,300 seeds m−2). VolunteerB. napusseedling recruitment differed among sites, and resulted in two distinct classes of sites based on average seedling densities of 39 and 89 plants m−2. Weed management tools were more effective at the sites with higher volunteerB. napusdensities. At these sites, soybean yield was greater when using an increased soybean-seeding density (44% greater yield using a seeding density of 682,500 vs. 455,000 seeds ha−1) or interrow tillage (36% greater yield with vs. without using interrow tillage). Soybean row spacing (19 vs. 38 vs. 76 cm) did not affect soybean yield, unless the reduction in row spacing was combined with an increased seeding density (65% greater yield with narrow-row soybean seeded at 682,500 vs. wide-row soybean seeded at 455,000 seeds ha−1). At the sites with higher volunteerB. napusdensities, seed production of canola volunteerB. napuswas greater when nitrogen fertilizer was applied to simulate an environment with greater nitrogen supply (77% greater number of volunteerB. napusseeds produced with vs. without broadcast application of 23 kg N ha−1urea). In northern climates, seeding soybean at increased densities using narrow-row spacing in fields with limited soil inorganic nitrogen and using interrow tillage in wide-row production systems are effective strategies that could augment chemical weed management in an integrated program for management of volunteerB. napus, and perhaps also other competitive early-season weeds.

<b>Effect of foliar fungicide and plant spacing on the expression of lipoxygenase enzyme and grain rot in maize hybrids

This study was carried out with the objective of evaluating the effect of fungicide application on grain rot in commercial maize hybrids and the relation between grain rot and the expression of lipoxygenase enzyme in grain in conventional row spacing of 0.70 m and reduced row spacing of 0.45 m. Treatments were made in a 3 x 8 factorial scheme, using three forms of management with fungicide (Trifloxystrobin + Prothioconazole) and eight maize hybrids divided into two groups (tolerant and susceptible) with three repetitions, totaling 72 plots in each environment (conventional and reduced spacing) in the 2013/2014 crop. The following characteristics were evaluated: grain rot percentage and lipoxygenase enzyme expression (LOX) in the grain. The hybrid and the fungicide utilized influenced the grain rot percentage. Grain rot percentage was reduced by the use of the fungicide, and the highest reduction was in susceptible hybrids with two applications, V8 and V8+VT. There was higher expression of LOX enzyme in maize hybrids that belong to the group tolerant of fungi that cause grain rot .The use of the fungicide in two applications, V8 (eight leaves) and VT (tasseling), increased the intensity of the LOX enzyme, which was more evident for the reduced spacing.

Genetic improvement of peanut in Argentina between 1948 and 2004: Light interception, biomass production and radiation use efficiency

An important milestone in Argentina peanut (Arachis hypogaea L.) breeding was the shift in the 1970s from cultivars with erect growth habit (CEGH) to cultivars with procumbent growth habit (CPGH). CPGH improved seed yield but also lengthened growth cycle. However, there is no information if the change in growth habit (GH) may have involved a phenotype with a canopy architecture that makes a differential capture and use of resources. Field experiments were performed to compute leaf are index (LAI), the fraction of incident photosynthetically active radiation intercepted by the crop (fIPAR), biomass production, radiation use efficiency (RUE) and harvest index (HI). Four cultivars of each GH, released between 1948 and 2004, were evaluated. The LAI was always larger among CPGH than among CEGH. Only the former reached the critical LAI. Likewise, fIPAR of CPGH was higher than that of CEGH throughout the crop cycle. Maximum fIPAR differed between GHs (P<0.001), with interannual mean values of 0.95 for CPGH and 0.77 for CEGH. Final total biomass of CPGH was 37% larger than that of CEGH. RUE values ranged between 1.88 and 2.46gMJ−1, and differed significantly (P≤0.008) between GHs (CEGH>CPGH), Years (Year 1>Year 2) and GH×Year (CPGH Year 1>CPGH Year 2=CEGH Year 2=CEGH Year 1). CPGH improved pod yield (+64%), seed yield (+101%), HI of pods (+29) and HI of seeds (+56%) respect to CEGH. Considering the effects of GH on the capacity of cultivars for achieving the critical LAI with current crop management, future research should focus on alternative sowing patterns (e.g., reduced row spacing among CEGH).