Crop Row Spacing Research Articles

Effects of bed width and crop row spacing on barnyardgrass (Echinochloa crus-galli) emergence and seed production in furrow-irrigated rice

Abstract Furrow-irrigated rice (Oryza sativa L.) has become a popular option for rice production in Arkansas. Highly troublesome weeds like barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] are a major problem for producers in all rice production systems. Cultural tactics should become a priority to enhance crop growth and competitiveness. This research aimed to determine the effects of bed width (irrigation furrow spacing) and crop row spacing manipulation on E. crus-galli emergence and seed production in a furrow-irrigated rice system. Three bed widths (76, 97, and 152 cm) (whole-plot factor) were used, and plots were drill seeded in four crop row spacings (13, 19, 25, and 38 cm) (subplot factor). The widest width of 152 cm had a slight increase in E. crus-galli density in the early rice life cycle but, by the end of the season, did not differ from the narrower bed widths. Conversely, a decrease in E. crus-galli seed production was observed as the bed width increased. Similar rice canopy coverage and yields occurred among all three bed widths. As for crop row spacing, as the width increased, E. crus-galli density also increased. The 13-cm crop row spacing had the lowest preflood E. crus-galli density, preharvest panicle count, and seed production. No effect of crop row spacing was observed on rice canopy coverage; however, the 13-cm crop row spacing produced the greatest rice yield. The 13-cm crop row spacing paired with the 152-cm bed width may be the optimum combination of ecological strategies in furrow-irrigated rice to reduce E. crus-galli seed production while maintaining rice growth and yield.

Quadrat misuse: Confessions of a cover crop researcher's biomass sampling journey

AbstractRectangular quadrats (1 m2 or less) are commonly used in cover crop research to sample shoot biomass in fields where the cover crops are planted in narrow rows. However, in drilled cover crops, quadrats do not accurately estimate cover crop biomass unless the width dimension of the quadrat, that runs perpendicular to the rows, is a multiple of the cover crop row spacing. Illustrations are provided with correctly sized and placed quadrats for sampling drilled cover crops along with calculations to convert sampled biomass to field‐scale units. Examples with various quadrat sizes, row spacings, and quadrat placements are used to illustrate how researchers can inadvertently underestimate or overestimate biomass by up to 49% and 27%, respectively. A survey of 92 articles with cover crop biomass data published in the Agronomy Journal and Weed Technology from 2017 to 2021 found that many studies used an incorrect quadrat size, which suggests that they may have inaccurately estimated cover crop biomass. However, assumptions were made to reach this conclusion because only a few papers provided the dimensions, orientation, and shape of the quadrat used. These results (1) raise important questions about possible errors made in papers reporting cover crop biomass data and associated metrics (nitrogen uptake, weed biomass, etc.), and (2) highlight the need for describing sampling methods in greater detail to ensure that accurate data and analysis are published in the literature. Approaches to correct possible errors in published research are described along with biomass sampling suggestions for future cover crop research.

Performance of cotton genotype TCH 1819 to high density planting system under winter irrigated condition at the Western agroclimatic zone of Tamil Nadu

Plant population is an important attribute in crop management practice. Increasing the plant density by decreasing the crop row spacing was an alternative strategy to optimize crop profit. Hence, the field trial was conducted at Tamil Nadu Agricultural University, Coimbatore, during the winter season of 2017 – 18 to study the effect of row spacing on the growth and yield of cotton genotype TCH 1819. The experimental design was Randomized Block Design (RBD) with seven spacing treatments viz., T1: 60 x 15 cm (1,11,111 plants ha-1), T2: 60 x 20 cm (83,333 plants ha-1), T3: 75 x 15 cm (88,888 plants ha-1), T4: 75 x 20 cm (66,666 plants ha-1), T5: 75 x 30 cm (44,444 plants ha-1), T6: 90 x 15 cm (74074 plants ha-1), T7: 90 x 20cm (55,555 plants ha-1) and was replicated thrice. Plant densities showed a significant (p=0.05) difference for all the characters studied. The higher plant density of 1,11,111 plants (60 x 15 cm) observed significantly (p=0.05) maximum plant height (103.14 cm), Leaf Area Index (LAI) (4.35), Dry Matter Production (DMP) (8125 kg/ha), Crop Growth Rate (CGR) (6.58 g/m2/day), root length (41.46 cm), root dry weight (14.94 g/plant), and chlorophyll index (48.24). The number of sympodial branches per plant (17) and bolls per plant (22 bolls) was found significant in the wider spacing of 75 x 30 cm. The narrow spacing of 60 x 15 cm noted the highest seed cotton yield (2565 kg/ha), net return (R65706.62), and B: C (2.32) ratio, followed by the spacing of 75 x 15 cm due to more plant density per unit area (m2). So, maximum yield in cotton can be achieved by decreasing the row spacing and increasing the plant population per unit area.

Impact of Diverse Annual Forage Mixtures on Weed Control in a Semiarid Environment

Intercropping with different crop species and different spatial patterns is suggested to lead to increased competition with weeds and reduced weed abundance and biomass. In this study, our objective was to explore the ability of multi-species annual forage crop mixtures to control weeds while providing productive forage. We utilized field and greenhouse trials to evaluate the impact of different crop mixtures and row spacing on weed control in the semi-arid Brown soil region of southwestern Saskatchewan, Canada. Seven different mixtures of up to eight annual forage crops were grown with row spacing of 15 cm or 30 cm in a replicated field trial. Weed abundance and biomass was significantly affected by crop species mixtures. Crop mixtures that contained radish and barley generally had higher weed suppression. Row spacing did not significantly impact weed abundance or biomass across the treatments. Results were similar over both years in spite of drastically different precipitation conditions. Forage production was significantly different between cropping mixtures in July in both years. The barley-radish mixture had the highest crop biomass in July, and this early crop production was linked to weed suppression because crop biomass had a significant effect on weed abundance and biomass in July, but not August. A greenhouse experiment was used to further evaluate the crops (i.e., barley and radish) that demonstrated the highest weed suppressive activity in the field trial. Crop identity and row spacing were both significant factors affecting weed and crop biomass production. Radish exhibited stronger control of common lamb’s quarters (Chenopodium album) compared to barley, but the binary mixture of the two species produced the highest crop biomass and equivalent weed control compared to the radish monoculture. This research suggests that cropping with multiple species (particularly forage radish) may be an effective way to control weeds in semiarid environments.

The Response of Two Drip-Irrigated Sweet Corn Varieties to the Twin-Row Production System in the Dry Mediterranean Region

Introduction: Minimizing production costs for drip-irrigated crops by reducing the number of driplines per unit-area is an urgent need to address the sustainability of the present production system. Materials and Methods: A two-year field experiment (2017 and 2018) was carried out to assess the effects of twin-row crop production system on two sweet corn varieties (Zea mays L.: an introduced variety “Silver Queen” and a local variety “White Kokab”) grown in a clay loam soil in the dry Mediterranean region. Three-row crop/dripline spacing configurations for each variety with three replicates were tested as: (i) single-row system at 75-cm crop row spacing with 75-cm dripline spacing (a dripline for each crop row), (ii) single-row system at 75-cm crop row spacing with 150-cm dripline spacing (a dripline for two crop rows), and (iii) twin-row system, 37.5 cm apart, on 150-cm centers, with 150-cm dripline spacing (a dripline for each twin-rows). Results and Conclusion: The local variety was better than the introduced variety in husked cop yield (13.93 t ha-1) and irrigation water use efficiency (IWUE, 1.92 kg m-3). Results also showed that the twin-row system with 150-cm dripline spacing provided similar husked cop yield and IWUE as the conventional 75-cm dripline spacing due to the more favourable rootzone soil water status; and both were higher in the two attributes than the single-row 150-cm dripline spacing. With 50% less unit-area driplines, twin-rows with 150-cm dripline spacing was considered to be more productive, economical and environmentally friendly.

Development of production management strategies for a long-duration rice variety: Rajendra Mahsuri—using crop growth model, DSSAT, for the state of Bihar, India

Increasing crop production is an inevitable demand of a current growing population all over the world. Implementation of best field crop practices potentially enables farmers to achieve that desired increase in crop production. The CERES-Rice model in Decision Support System for Agrotechnology Transfer was used in this study with 10 years (2006–2015) of field experimental data collected from the CIMMYT (International Maize and Wheat Improvement Center)–BISA (Borlaug Institute for South Asia), Pusa, Bihar, research farm to provide the water stress impact on crop production, and best management strategies to improve the rice yield, followed by the calibration (2006–2010) and validation (2011–2015) from the collected field experimental data. The genetic coefficients were developed for the rice variety, Rajendra Mahsuri. The normalized root-mean-square error (RMSEn) and d-index values were obtained to be 2.73% and 0.62, respectively, for prediction of yield with the model performance efficiency (ME) of 75% in the range of 5 years of validation studies. The model indicated that water stress during vegetative and maturity phase decreased rice yield by 24% and 33%, respectively. However, the water stress during reproductive stage showed the largest reduction in the yield by 43%, and hence, must be avoided. Several management strategies were investigated to determine their impact on rice yield. Optimum transplanting date was found to be during the month of June for the highest yield of Rajendra Mahsuri rice. Application of crop residue up to 2500 kg/ha would increase the yield by 21.94%, compared to the management practices where no residue is applied in the field. Crop row spacing of 15–25 cm increased rice yield by 16.47–18.49%, and for maximum yield, optimum planting depth was found to be 2–4 cm. Additionally, keeping a ponding depth of 4–6 cm before 10 days of harvesting would aid in maximizing the rice yield by 10.70–16.10%, compared to no ponding or more than 6 cm of ponding conditions in the field.

Effect of row spacings on soil nematode communities and ecosystem multifunctionality at an aggregate scale

Effect of crop row spacing on the belowground ecosystem, especially at an aggregate scale, remains unexplored. To explore how row spacing influenced nematode community and ecosystem function at the aggregate scale, four row spacings i.e. equidistant-row (ER, 50 cm-inter-row distance, 33 cm-intra-row between plants in each row) and non-equidistant-row including NR1 (100 cm + 50 cm row distance and 22 cm intra-row), NR2 (100 cm + 50 cm inter-row and 25 cm intra-row), and NR3 (60 cm + 40 cm inter-row and 33 cm intra-row) were compared, and four soil aggregate fractions i.e. >2 mm, 1–2 mm, 0.25–1 mm and <0.25 mm were separated. Row spacing did not impact C and N, but significantly influenced P. The regulation effect of acid phosphatase on soil available P was aggregate-scale dependent. Nematode faunal analysis indicated that NR3 within 0.25–1 mm was less disturbed or relatively undisturbed environments. Structural equation model showed row spacing pattern directly affected multifunctionality, while aggregate fractions indirectly contributed to multifunctionality mainly by regulating the richness of total nematodes and trophic groups. It was concluded that NR3 had potential to construct more stable food web, and therefore was possibly the suitable planting pattern.

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

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

Water-Use Efficiency: Advances and Challenges in a Changing Climate.

Water use efficiency (WUE) is defined as the amount of carbon assimilated as biomass or grain produced per unit of water used by the crop. One of the primary questions being asked is how plants will respond to a changing climate with changes in temperature, precipitation, and carbon dioxide (CO2) that affect their WUE At the leaf level, increasing CO2 increases WUE until the leaf is exposed to temperatures exceeded the optimum for growth (i.e., heat stress) and then WUE begins to decline. Leaves subjected to water deficits (i.e., drought stress) show varying responses in WUE. The response of WUE at the leaf level is directly related to the physiological processes controlling the gradients of CO2 and H2O, e.g., leaf:air vapor pressure deficits, between the leaf and air surrounding the leaf. There a variety of methods available to screen genetic material for enhanced WUE under scenarios of climate change. When we extend from the leaf to the canopy, then the dynamics of crop water use and biomass accumulation have to consider soil water evaporation rate, transpiration from the leaves, and the growth pattern of the crop. Enhancing WUE at the canopy level can be achieved by adopting practices that reduce the soil water evaporation component and divert more water into transpiration which can be through crop residue management, mulching, row spacing, and irrigation. Climate change will affect plant growth, but we have opportunities to enhance WUE through crop selection and cultural practices to offset the impact of a changing climate.

Effect of Strip-Till Timing, Fertilizer Placement, and Row Spacing on Soybean Seed Yield

Core Ideas A reduction in penetration resistance was observed in the rooting zone of fall and spring strip-till rows compared with no-till rows. Spring strip-till reduced penetration resistance at more depths than fall strip-till. There was no yield response of strip-till compared with no-till in the small-plot study. There was no difference in plant population or yield between strip-till or no-till in the on-farm study. The perceived yield deficit normally associated with 30-in row spacing was reduced with the use of strip-till. Alleviation of cold, wet, compacted soil is a major concern for Wisconsin soybean [Glycine max (L.) Merr.] growers because of the narrow harvest and planting windows in spring and fall. Strip-till, which combines benefits of intensive tillage in crop rows and no-till between crop rows, has emerged as a viable conservation tillage option to alleviate these issues while maintaining soil structure and health. Though strip-till's yield response in corn (Zea mays L.) is well documented, soybean's yield response has been studied less. This study aims to: (i) quantify the effect of no-till and strip-till timing, crop row spacing, and fertilizer placement on soybean plant population, canopy coverage, and seed yield; (ii) evaluate no-till and strip-till timing and/or crop row spacing on soil temperature and penetration resistance; and (iii) determine the best management recommendations for strip-till use in Wisconsin soybean production systems. A small-plot experiment was conducted in Arlington, WI, during the 2016, 2017, and 2018 growing seasons and an on-farm experiment was conducted in Sharon, WI, during the 2016 and 2017 growing seasons. In the small-plot trial, 15-inch spring strip-till (66.5 bu acre-1) yielded 6.7% more than 15-inch fall strip-till (62.0 bu acre-1). There was no difference in yield between the 15-inch and 30-inch row spacings across all tillage treatments. Plant population in the small-plot trial was 17,000 plants acre-1 (15.5%) greater at the 30-inch row spacing than at the 15-inch row spacing. In the on-farm trial, no differences were observed among treatment combinations. Overall, results suggested that there were no differences in yield when comparing strip-till and no-till for soybean production.

Productivity of soybean in management zones with application of different sowing densities

ABSTRACT: The present study aimed to assess the efficiency of sowing at variable rates for soybean cultivation in two management zones (MZs) which were defined based on stable attributes and correlated with productivity using the Fuzzy C-means clustering algorithm and the kriging interpolation.Seeding was carried out in the 2015/2016 and 2017/2018 crops with a variation of 20% of seeds and crop row spacing of 0.70m. In each MZ, 8 plots with higher and lower seed density were established. Productivity was measured using a harvest monitor connected to a harvester. Data were filtered and submitted to descriptive analysis. Productivity maps were generated using the inverse square distance interpolation for each seeding density. In the MZ with the highest productive potential (MZ 1), the productivity was 3.39 and 3.18t ha-1, and in the MZ with the lowest productive potential (MZ 2) the productivity was 3.30 and 3.11t ha-1 for the years 2016 and 2018, respectively. Interpolation estimated higher productivity with the application of 15 plants m-1. Based on the economic analysis, it is suggested in this study the application of 214,000 plants ha-1 in both MZs.

Crop Row Detection on Tiny Plants With the Pattern Hough Transform

In sustainable farming, robotic solutions are in rising demand. Specifically robots for precision agriculture open up possibilities for new applications. Such applications typically require a high accuracy of the underlying navigation system. A cornerstone for reliable navigation is the robust detection of crop rows. However, detecting crops from vision or laser data is particularly challenging when the plants are either tiny or so large that individual plants cannot be distinguished easily. In this letter, we present a pipeline for reliable plant segmentation in any crop growth stage, as well as a novel algorithm for robust crop row detection that adapts the Hough transform for line detection to detect a pattern of parallel equidistant lines. Our algorithm is able to jointly estimate the angle, lateral offset and crop row spacing and is particularly suited for tiny plants. In extensive experiments using various real-world data sets from different kinds and sizes of crops we show that our algorithm provides reliable and accurate results.

К РАЗРАБОТКЕ ПОЧВООБРАБАТЫВАЮЩИХ РАБОЧИХ ОРГАНОВ НА ОСНОВЕ ТВЕРДОГРАММ ПОЛЕЙ

When solving engineering problems in soil cultivation, soil resistivity is applied. The use of solidograms is more preferable in the construction of soil-working tools and the operation of agricultural machinery. The developed technologies and instruments for continuous layerwise determination of the longitudinal hardness of the arable layer make it possible to obtain soil maps by hardness, to create a database. Factors affecting hardness variability include crop cultivation technology, row spacing, parameters, number and gauge of movers of mobile power tools and agricultural tools, the width of the technological track. The influence of the degrees of freedom of the working units on the intensity of loosening of the soil, the magnitude and nature of the change in the traction resistance, both as a separate working unit and the entire implement, is considered. A combined working unit consisting of a cutaway knife, a built-in drainer, a spring bender on a spring-loaded draft, which creates conditions for the realization of low-intensity types of deformation, the Baushinger effect is proposed. The advantage of the working unit is the continuous automatic adaptation of geometric parameters. For design and strength calculation of such working units, synthesis of elastic characteristics, it is recommended to use methods of the theory of random oscillations. The force and kinematic perturbation of the oscillations is caused by the variability of the hardness of the arable layer, the speed of movement of the working organ, the vibrorheological properties of the soil, and the parameters of the elastic characteristics of the system of springs. The rationale for the smoothing capability of the dynamical system being designed is substantiated by justifying rational design parameters, selecting the material, determining the system parameters by known characteristics at the input and output.

Integrated Role of Row Spacing and Adjuvant to Reduce Herbicide Dose in Maize Under Semi-Arid Conditions

ABSTRACT: Crop row spacing adjustment and adjuvants have a significant role in decreasing herbicide cost and environmental damage by reducing herbicide application rate. A field study was conducted to assess the impact of two row spacing values and reduced herbicide rates along with adjuvant on weeds in maize in 2014 and 2015. The experiment consisted of atrazine plus mesotrione plus halosulfuran methyl (pre-mixed herbicide) at label rate (719.2 g a.i. ha-1); reduced rates of 75% (539.4 g a.i. ha-1) and 50% (359.6 g a.i. ha-1) alone and in combination with alkyl ether sulphate at 396.8 mL ha-1 as an adjuvant along with weedy check in maize sown at 60 and 75 cm row spacing. Alkyl ether sulphate increased weed control efficacy (13-35%) of the pre-mixed herbicide. Herbicide along with adjuvant provided effective weed control at 60 cm as compared to 75 cm apart sown maize. The most effective control of weeds, and increase in maize grain yield (33-45% as compared to non-treated control) and net income were obtained by the pre-mixed herbicide at 539.4 g a.i. ha-1 (75% of recommended rate) with adjuvant and pre-mixed herbicide at 719.2 g a.i. ha-1 (recommended dose) without adjuvant. The results revealed that the rate of pre-mixed herbicide can be reduced by up to 25% of the recommended field rate by the addition of alkyl ether sulphate as an adjuvant at 60 cm row spacing of maize to increase maize yield and net income.

Has Breeding Improved Soybean Competitiveness with Weeds?

Soybean yield gain over the last century has been attributed to both genetic and agronomic improvements. Recent research has characterized how breeding efforts to improve yield gain have also secondarily impacted agronomic practices such as seeding rate, planting date, and fungicide use. To our knowledge, no research has characterized the relationship between weed–soybean interference and genetic yield gain. Therefore, the objectives of this research were to determine whether newer cultivars would consistently yield higher than older cultivars under increasingly competitive environments, and whether soybean breeding efforts over time have indirectly increased soybean competitiveness. Field research was conducted in 2014, 2015, and 2016 in which 40 maturity group (MG) II soybean cultivars released between 1928 and 2013 were grown season-long with three different densities of volunteer corn (0, 2.8, and 11.2 plants m−2). Soybean seed yield of newer cultivars was higher than older cultivars at each volunteer corn density (P&lt;0.0001). Soybean seed yield was also higher in the weed-free treatment than at low or high volunteer corn seeding rates. However, soybean cultivar release year did not affect late-season volunteer corn shoot dry biomass at either seeding rate of 2.8 or 11.2 seeds m−2. The results indicate that while soybean breeding efforts have increased yield potential over time, they have not increased soybean competitiveness with volunteer corn. These results highlight the importance of other cultural practices such as planting date and crop row spacing for weed suppression in modern soybean production systems.

Technology for Automation of Weed Control in Specialty Crops

Specialty crops, like flowers, herbs, and vegetables, generally do not have an adequate spectrum of herbicide chemistries to control weeds and have been dependent on hand weeding to achieve commercially acceptable weed control. However, labor shortages have led to higher costs for hand weeding. There is a need to develop labor-saving technologies for weed control in specialty crops if production costs are to be contained. Machine vision technology, together with data processors, have been developed to enable commercial machines to recognize crop row patterns and control automated devices that perform tasks such as removal of intrarow weeds, as well as to thin crops to desired stands. The commercial machine vision systems depend upon a size difference between the crops and weeds and/or the regular crop row pattern to enable the system to recognize crop plants and control surrounding weeds. However, where weeds are large or the weed population is very dense, then current machine vision systems cannot effectively differentiate weeds from crops. Commercially available automated weeders and thinners today depend upon cultivators or directed sprayers to control weeds. Weed control actuators on future models may use abrasion with sand blown in an air stream or heating with flaming devices to kill weeds. Future weed control strategies will likely require adaptation of the crops to automated weed removal equipment. One example would be changes in crop row patterns and spacing to facilitate cultivation in two directions. Chemical company consolidation continues to reduce the number of companies searching for new herbicides; increasing costs to develop new herbicides and price competition from existing products suggest that the downward trend in new herbicide development will continue. In contrast, automated weed removal equipment continues to improve and become more effective.

Implications of narrow crop row spacing in managing weeds in mungbean (Vigna radiata)

The mungbean production area is increasing in Australia due to increasing demand for the grain in Asian countries. However, the mungbean crop is generally grown with wide row spacing, and therefore, it is prone to heavy weed infestation which has a significant impact on the mungbean grain yield. Experiments were conducted in 2015 and 2016 to determine the row-spacing impact on crop yield and weed growth for mungbean grown in 25, 50, and 75 cm space rows. Row spacing did not affect weed biomass and mungbean grain yield when weeds were allowed to grow from crop sowing to maturity. However, narrower row spacing (25 and 50 cm) had lower weed biomass and higher grain yield when weeds were allowed to grow beyond 3 and 6 weeks after planting (WAP). Mungbean grown at 25 and 50 cm rows had 60–70% and 70–92% less weed biomass than the mungbean grown at 75 cm rows for the weeds grown beyond 3 and 6 WAP, respectively. In weed-free conditions, too, mungbean grain yields were greater in narrow rows than in wider rows. Weeds grown beyond 6 WAP did not affect grain yield of 25 and 50 cm rows but reduced mungbean yield with 75 cm rows. The practical implication of this study is that narrowing row spacing in mungbean could lead to reduced weed growth and seed production and increased crop yield.

Weed growth and crop yield loss in wheat as influenced by row spacing and weed emergence times

Reducing crop row spacing and delaying time of weed emergence may provide crops a competitive edge over weeds. Field experiments were conducted to evaluate the effects of crop row spacing (11, 15, and 23-cm) and weed emergence time (0, 20, 35, 45, 55, and 60 days after wheat emergence; DAWE) on Galium aparine and Lepidium sativum growth and wheat yield losses. Season-long weed-free and crop-free treatments were also established to compare wheat yield and weed growth, respectively. Row spacing and weed emergence time significantly affected the growth of both weed species and wheat grain yields. For both weed species, the maximum plant height, shoot biomass, and seed production were observed in the crop-free plots, and delayed emergence decreased these variables. In weed–crop competition plots, maximum weed growth was observed when weeds emerged simultaneously with the crop in rows spaced 23-cm apart. Less growth of both weed species was observed in narrow row spacing (11-cm) of wheat as compared with wider rows (15 and 23-cm). These weed species produced less than 5 seeds plant−1 in 11-cm wheat rows when they emerged at 60 DAWE. Presence of weeds in the crop especially at early stages was devastating for wheat yields. Therefore, maximum grain yield (4.91 t ha−1) was recorded in the weed-free treatment at 11-cm row spacing. Delay in time of weed emergence and narrow row spacing reduced weed growth and seed production and enhanced wheat grain yield, suggesting that these strategies could contribute to weed management in wheat.

Organic weed management in chickpea: a simulation approach

The effect of chickpea (Cicer arietinum L.) canopy on a weed (annual sowthistle) growth and development has been simulated using a virtual model of architectural development. The model simulates the effect of crop canopy architecture, seeding rate, and row spacing on sowthistle. Such a simulation study on crop-weed competition may help to develop appropriate cultural weed management strategies in chickpea. According to the simulations, rapid early leaf production is an important trait to improve the competitive ability of chickpea. Results also revealed that the emergence time of sowthistle in relation to chickpea plays a more crucial role in sowthistle performance and survival in chickpea than the density of crop.

Consequences of narrow crop row spacing and delayed Echinochloa colona and Trianthema portulacastrum emergence for weed growth and crop yield loss in maize

SummaryEchinochloa colona and Trianthema portulacastrum are weeds of maize that cause significant yield losses in the Indo‐Gangetic Plains. Field experiments were conducted in 2009 and 2010 to determine the influence of row spacing (15, 25 and 35 cm) and emergence time of E. colona and T. portulacastrum (0, 15, 25, 35, 45 and 55 days after maize emergence; DAME) on weed growth and productivity of maize. A season‐long weed‐free treatment and a weedy control were also used to estimate maize yield and weed seed production. Crop row spacing as well as weed emergence time had a significant influence on plant height, shoot biomass and seed production of both weed species and grain yield of maize in both years. Delay in emergence of weeds resulted in less plant height, shoot biomass and seed production. However, increase in productivity of maize was observed by delay in weed emergence. Likewise, growth of both weed species was less in narrow row spacing (15 cm) of maize, as compared with wider rows (25 and 35 cm). Maximum seed production of both weeds was observed in weedy control plots, where there was no competition with maize crop and weeds were in rows 35 cm apart. Nevertheless, maximum plant height, shoot biomass and seed production of both weed species were observed in 35 cm rows, when weeds emerged simultaneously with maize. Both weed species produced only 3–5 seeds per plant, when they were emerged at 55 DAME in crop rows spaced at 15 cm. Infestation of both weeds at every stage of crop led to significant crop yield loss in maize. Our results suggested that narrow row spacing and delay in weed emergence led to reduced weed growth and seed production and enhanced maize grain yield and therefore could be significant constituents of integrated weed management strategies in maize.