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    Topic review

    Crop Diversification and Weed Control

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    Submitted by: Te Ming Paul Tseng

    Definition

    Weeds can be defined as any plant that is objectionable or interferes with the activities or welfare of humans. In a crop production system, weeds compete for the same resources as the crops, such as water, nutrients, sunlight, and space, limiting crop productivity. Aggressive weed competition reduces crop yield significantly and adds further cost to crop production owing to their management. Yield loss due to weeds depends on several factors such as density, time of emergence, type of weed, and crop type. 

    1. Introduction

    Globally, up to 40% yield loss has been reported due to weeds [1]. In the USA, yield loss because of weeds has been estimated to exceed eight dollar billion annually [2]. Among US crops, corn and soybean suffer the highest aggregate production loss because of weeds. On average, across 2007–2013, weed interference caused 52 and 50% yield loss in soybean and corn, respectively, in the USA and Canada [3][4]. In Australia and India, annual yield losses due to weeds in grain crops were estimated to be 2.52 and 11 billion USD, respectively [5][6]. China reported a grain loss of approximately 3 million metric tons each year because of weeds [7]. These data indicate that weeds continue to be a major threat in crop production, causing substantial economic and yield loss worldwide [8].
    In developing countries, subsistence farming is the primary form of agriculture, and weeds are generally managed through hand-weeding. However, due to increasing urbanization, increased labor costs, and decreasing workforce in agriculture, people are moving towards using chemicals for controlling weeds. In Southeast Asian countries such as Nepal, Bhutan, Bangladesh, and Thailand, there has been an increase in the haphazard use of herbicides for weed control in subsistence farming systems leading to health and environmental concerns [9][10]. In developed countries such as the USA, China, and Brazil, farmers are engaged in specialized agricultural production systems with the increased use of synthetic fertilizers and herbicides. The top ten consumers of pesticides globally are China, USA, Argentina, Thailand, Brazil, Italy, France, Canada, Japan, and India [11]. In 2014, approximately 2 million tons of chemical pesticides were used in the agricultural sector globally, of which 47.5% constituted herbicides [12]. Over-reliance on herbicides to control weeds and injudicious use of herbicides has led to several issues such as herbicide-resistant weeds, herbicide drift, environmental and health problems, and extinction or population reduction of segetal species [13][14][15]. Currently, there are approximately 500 unique cases of herbicide-resistant weeds globally [13]. Among the global herbicide-resistant weed cases, most were reported in the USA, followed by Australia, Canada, China, and Brazil [13]. In addition to this, some weeds have developed resistance to multiple modes of action while others have (developed decreased sensitivity to herbicides [16][17][18]. Both target-site and non-target-site mutations in the herbicide-resistant weeds have been reported [19][20]. These observations indicate over-reliance on herbicides as a non-sustainable measure for weed control. The development of herbicides with novel modes of action is imperative for herbicide resistance management; however, no new mode of action has been developed in the past three decades [21].
    Further, there have been increasing reports of crop damage because of herbicide drift in recent years. For instance, 2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most used herbicides to control broadleaf weeds in agriculture; however, they often damage the neighboring 2,4-D sensitive cotton field resulting in the loss of millions of dollars in the USA and Australia [22]. Likewise, severe crop injury has been reported due to the off-target movement of dicamba to the neighboring fields with non-dicamba tolerant crops [23][24]. Further, the increasing use of herbicides has led to the accumulation of agricultural contaminants such as arsenic, cadmium, lead, and mercury in soil and water resources [25]. In the USA, a survey of 51 major river basins by the US Geological Survey reported that pesticides were detected in 97% of the samples from streams near agricultural areas [26]. Short and long-term health effects from exposure to agricultural chemicals have also been documented [27][28]. These examples provide evidence that over-dependence on herbicides may result in the increased frequency of herbicide resistance in weeds, water and soil pollution, and herbicide drift. Thus, to mitigate and/or eradicate ecological, environmental, and social externalities associated with intensive use of herbicides, it is imperative to design and promote alternative weed management approaches.
    Studies have suggested that increasing crop diversity can subject weeds to a greater number of stresses and reduce reliance on external chemicals for weed/pest control [29][30]. Crop diversification can be defined as the conscious inclusion of functional biodiversity at the temporal and/or spatial levels to improve the productivity and stability of ecosystem services [31]. The concept of crop diversification is complex, and a diversified cropping system is more complicated with different crop combinations, unlike monoculture, where extensive farmlands are cultivated with one or two annual crops. Modern agricultural practices have simplified the agricultural systems to enhance the profitability of major crops or livestock. In contrast, a diversified cropping system focuses on creating sustainable, resilient, and socially just global food systems. Some of the examples of a diversified cropping system would be (i) multiple genotypes of the same crop or different crops grown in polyculture [31], (ii) inclusion of legumes in otherwise cereal dominated systems [31] and, (iii) temporal and spatial rotation of crops, including but not limited to cover crops, trap crops, hedgerows, fallow fields, etc. [31]
    There are a certain set of rules on which crops to choose in a diversified farming system (for, e.g., Liebman and Dyck talks about strategies for crop rotation and intercropping in the context of weed management [32]). The consequences of diversification include, but are not limited to, increased soil nutrient recycling, pest and disease suppression, enhanced water use efficiency, and pollination [33]. Many of the previous studies have advocated the importance of crop diversification in sustainable agricultural production [34][35]. However, knowledge of how different crop diversification techniques impact weed management and the constraints of adopting crop diversification in the modern agricultural context is lacking [36].

    2. Crop Diversification Focused on Weed Management

    Liebman and Staver [29] noted two general principles for weed management through crop diversification, (a) weeds should be subjected to various stress and mortality factors by using crop sequences containing different species and management practices, and (b) diversification methods should be designed to maximize the capture of light, nutrients, and water by crop, thus reducing the loss by weeds. These principles should be the foundation for any crop diversification methods (e.g., crop rotation, cover cropping, and intercropping). However, the objective of the diversification strategies is not to eliminate all the weeds, instead to control them. Weeds offer various ecosystem services, which sometimes are beneficial to crops and humans [37][38][39][40][41][42].

    2.1. Crop Rotation

    Crop rotation is the practice of growing a series of crops sequentially over time on the same land, thus providing temporal variability [43]. Crop rotation is a sustainable agricultural practice aimed at achieving high economic output with minimum possible cost [44]. Zhao et al. [45] recently performed a meta-analysis on 45 studies and reported a 20% increment in crop yields due to crop rotation. Moreover, another meta-analysis on 54 studies showed that crop rotation leads to a 49% reduction in weed density [46]. Thus, crop rotation helps to reduce weed pressure and increase crop yield.

    2.2. Intercropping

    Intercropping is an integrated weed management practice in which two or more crop species or genotypes are cultivated together and coexisting for a time. It is commonly used in countries with low-input (high-labor) and resource-limited agricultural systems on a small piece of land [47][48]. Intercrops can broadly be divided into three types: (a) relay intercropping (planting a second crop before the first crop is mature), (b) mixed intercropping (simultaneously growing two or more crops), and (c) strip cropping (growing two or more crops simultaneously in strips) Figure 1 [49]. Each type has its benefits, but overall intercropping compared with monocrops provides a similar yield with reduced inputs, pest control (weeds, diseases, and insects), and stable aggregate food yields per unit area [50][51].

    3. Conclusions

    Despite high yields and low input cost, the modern monoculture system relies heavily on chemicals for weed control generating human health, environmental and ecological concerns. Herbicide-resistant weeds, increasing health issues associated with agricultural chemicals, water and soil pollution are among the major negative impacts of modern agriculture. New and innovative strategies for sustainable weed management are imperative for sustainable weed management before irreversible damage to humans and the environment. The best strategy for developing a resilient and sustainable production system is adopting diversified farming with ecological weed management options. However, farmers are reluctant to adopt a diversified cropping system because of the requirement of varying skill sets and higher initial investment. Efforts must be taken by both government agencies and the private sectors to promote diversified farming among the commercial and small-scale farmers for developing sustainable farming systems in the future.

    The entry is from 10.3390/agriculture11050461

    References

    1. Oerke, E.-C. Crop Losses to Pests. J. Agric. Sci. 2006, 144, 31–43.
    2. Loux, M.M.; Doohan, D.; Dobbels, A.F.; Johnson, W.G.; Young, B.G.; Legleiter, T.R.; Hager, A. Weed Control Guide for Ohio; University of Illinois: Champaign, IL, USA, 2017; pp. 1–2.
    3. Soltani, N.; Dille, J.A.; Burke, I.C.; Everman, W.J.; VanGessel, M.J.; Davis, V.M.; Sikkema, P.H. Perspectives on Potential Soybean Yield Losses from Weeds in North America. Weed Technol. 2017, 31, 148–154.
    4. Soltani, N.; Dille, J.A.; Burke, I.C.; Everman, W.J.; VanGessel, M.J.; Davis, V.M.; Sikkema, P.H. Potential Corn Yield Losses from Weeds in North America. Weed Technol. 2016, 30, 979–984.
    5. Llewellyn, R.S.; Ronning, D.; Ouzman, J.; Walker, S.; Mayfield, A.; Clarke, M. Impact of Weeds on Australian Grain Production: The Cost of Weeds to Australian Grain Growers and the Adoption of Weed Management and Tillage Practices; Report for Grains Research & Development Corporation: Canberra, Australia, 2016.
    6. Gharde, Y.; Singh, P.K.; Dubey, R.P.; Gupta, P.K. Assessment of Yield and Economic Losses in Agriculture Due to Weeds in India. Crop Prot. 2018, 107, 12–18.
    7. Mesterházy, Á.; Oláh, J.; Popp, J. Losses in the Grain Supply Chain: Causes and Solutions. Sustainability 2020, 12, 2342.
    8. Ramesh, K.; Matloob, A.; Aslam, F.; Florentine, S.K.; Chauhan, B.S. Weeds in a Changing Climate: Vulnerabilities, Consequences, and Implications for Future Weed Management. Front. Plant Sci. 2017, 8, 95.
    9. Tirado, R.; Englande, A.J.; Promakasikorn, L.; Novotny, V. Use of Agrochemicals in Thailand and Its Consequences for the Environment. Available online: (accessed on 28 March 2021).
    10. Gianessi, L.P. The Increasing Importance of Herbicides in Worldwide Crop Production: The Increasing Importance of Herbicides. Pest Manag. Sci. 2013, 69, 1099–1105.
    11. Pariona, A. Top Pesticide Using Countries. Available online: (accessed on 28 March 2021).
    12. Oca, A.M.; Arreola, L.; Flores, A.; Sanchez, J.; Flores, G. Low-Cost Multispectral Imaging System for Crop Monitoring; IEEE: Dallas, TX, USA, 2018.
    13. Available online: (accessed on 28 March 2021).
    14. Egan, J.F.; Mortensen, D.A. Quantifying Vapor Drift of Dicamba Herbicides Applied to Soybean. Environ. Toxicol. Chem. 2012, 31, 1023–1031.
    15. Perrino, E.V.; Calabrese, G. Endangered Segetal Species in Southern Italy: Distribution, Conservation Status, Trends, Actions and Ethnobotanical Notes. Genet. Resour. Crop Evol. 2018, 65, 2107–2134.
    16. Shrestha, S.; Sharma, G.; Burgos, N.R.; Tseng, T.-M. Response of Weedy Rice (Oryza spp.) Germplasm from Arkansas to Glyphosate, Glufosinate, and Flumioxazin. Weed Sci. 2019, 67, 303–310.
    17. Yu, Q.; Cairns, A.; Powles, S. Glyphosate, Paraquat and ACCase Multiple Herbicide Resistance Evolved in a Lolium Rigidum Biotype. Planta 2007, 225, 499–513.
    18. Owen, M.J.; Walsh, M.J.; Llewellyn, R.S.; Powles, S.B. Widespread Occurrence of Multiple Herbicide Resistance in Western Australian Annual Ryegrass (Lolium Rigidum) Populations. Aust. J. Agric. Res. 2007, 58, 711.
    19. Tseng, T.-M.; Shrestha, S.; McCurdy, J.D.; Wilson, E.; Sharma, G. Target-Site Mutation and Fitness Cost of Acetolactate Synthase Inhibitor-Resistant Annual Bluegrass. HortScience 2019, 54, 701–705.
    20. Yuan, J.S.; Tranel, P.J.; Stewart, C.N., Jr. Non-Target-Site Herbicide Resistance: A Family Business. Trends Plant Sci. 2007, 12, 6–13.
    21. Duke, S.O. Why Have No New Herbicide Modes of Action Appeared in Recent Years? Pest Manag. Sci. 2012, 68, 505–512.
    22. Egan, J.F.; Barlow, K.M.; Mortensen, D.A. A Meta-Analysis on the Effects of 2,4-D and Dicamba Drift on Soybean and Cotton. Weed Sci. 2014, 62, 193–206.
    23. Suarez Cadavid, L.A. Proximal and Remote Sensing for Early Detection and Assessment of Herbicide Drift Damage on Cotton Crops; University of Southern Queensland: Toowoomba, Australia, 2018.
    24. Zhang, J.; Huang, Y.; Reddy, K.N.; Wang, B. Assessing Crop Damage from Dicamba on Non-dicamba-tolerant Soybean by Hyperspectral Imaging through Machine Learning. Pest Manag. Sci. 2019, 75, 3260–3272.
    25. Udeigwe, T.K.; Teboh, J.M.; Eze, P.N.; Stietiya, M.H.; Kumar, V.; Hendrix, J.; Mascagni, H.J., Jr.; Ying, T.; Kandakji, T. Implications of Leading Crop Production Practices on Environmental Quality and Human Health. J. Environ. Manag. 2015, 151, 267–279.
    26. Gilliom, R.J. Pesticides in U.S. Streams and Groundwater. Environ. Sci. Technol. 2007, 41, 3408–3414.
    27. Van Bruggen, A.H.C.; He, M.M.; Shin, K.; Mai, V.; Jeong, K.C.; Finckh, M.R.; Morris, J.G., Jr. Environmental and Health Effects of the Herbicide Glyphosate. Sci. Total Environ. 2018, 616–617, 255–268.
    28. Sterling, T.D.; Arundel, A.V. Health Effects of Phenoxy Herbicides: A Review. Scand. J. Work Environ. Health 1986, 12, 161–173.
    29. Liebman, M.; Staver, C.P. Crop Diversification for Weed Management. In Ecological Management of Agricultural Weeds; Cambridge University Press: Cambridge, UK, 2001; pp. 322–374.
    30. Smith, R.G.; Gross, K.L. Assembly of Weed Communities along a Crop Diversity Gradient. J. Appl. Ecol. 2007, 44, 1046–1056.
    31. Kremen, C.; Miles, A. Ecosystem Services in Biologically Diversified versus Conventional Farming Systems: Benefits, Externalities, and Trade-Offs. Ecol. Soc. 2012, 1.
    32. Liebman, M.; Dyck, E. Crop Rotation and Intercropping Strategies for Weed Management. Ecol. Appl. 1993, 3, 92–122.
    33. Hufnagel, J.; Reckling, M.; Ewert, F. Diverse Approaches to Crop Diversification in Agricultural Research. A Review. Agron. Sustain. Dev. 2020, 40.
    34. Bommarco, R.; Kleijn, D.; Potts, S.G. Ecological Intensification: Harnessing Ecosystem Services for Food Security. Trends Ecol. Evol. 2013, 28, 230–238.
    35. Lin, B.B. Resilience in Agriculture through Crop Diversification: Adaptive Management for Environmental Change. Bioscience 2011, 61, 183–193.
    36. Meynard, J.M.; Messéan, A.; Charlier, A.; Charrier, F.; Farès, M.; Le Bail, M.; Savini, I. Crop Diversification: Obstacles and Levers; INRA: Paris, France, 2013.
    37. Blaix, C.; Moonen, A.C.; Dostatny, D.F.; Izquierdo, J.; Le Corff, J.; Morrison, J.; Von Redwitz, C.; Schumacher, M.; Westerman, P.R. Quantification of Regulating Ecosystem Services Provided by Weeds in Annual Cropping Systems Using a Systematic Map Approach. Weed Res. 2018, 58, 151–164.
    38. Capinera, J.L. Relationships between Insect Pests and Weeds: An Evolutionary Perspective. Weed Sci. 2005, 53, 892–901.
    39. Bretagnolle, V.; Gaba, S. Weeds for Bees? A Review. Agron. Sustain. Dev. 2015, 35, 891–909.
    40. Smith, B.M.; Aebischer, N.J.; Ewald, J.; Moreby, S.; Potter, C.; Holland, J.M. The Potential of Arable Weeds to Reverse Invertebrate Declines and Associated Ecosystem Services in Cereal Crops. Front. Sustain. Food Syst. 2020, 3.
    41. Mouritsen, O.G. Those Tasty Weeds. J. Appl. Phycol. 2017, 29, 2159–2164.
    42. Amato-Lourenco, L.F.; Ranieri, G.R.; de Oliveira Souza, V.C.; Junior, F.B.; Saldiva, P.H.N.; Mauad, T. Edible Weeds: Are Urban Environments Fit for Foraging? Sci. Total Environ. 2020, 698, 133967.
    43. Varvel, G.E. Crop Rotation and Nitrogen Effects on Normalized Grain Yields in a Long-term Study. Agron. J. 2000, 92, 938–941.
    44. Bowles, T.M.; Mooshammer, M.; Socolar, Y.; Calderón, F.; Cavigelli, M.A.; Culman, S.W.; Deen, W.; Drury, C.F.; Garcia y Garcia, A.; Gaudin, A.C.M.; et al. Long-Term Evidence Shows That Crop-Rotation Diversification Increases Agricultural Resilience to Adverse Growing Conditions in North America. One Earth 2020, 2, 284–293.
    45. Zhao, J.; Yang, Y.; Zhang, K.; Jeong, J.; Zeng, Z.; Zang, H. Does Crop Rotation Yield More in China? A Meta-Analysis. Field Crops Res. 2020, 24, 107659.
    46. Weisberger, D.; Nichols, V.; Liebman, M. Does Diversifying Crop Rotations Suppress Weeds? A Meta-Analysis. PLoS ONE 2019, 14, e0219847.
    47. Simmonds, N.W.; Vandermeer, J. The Ecology of Intercropping. J. Appl. Ecol. 1989, 26, 1107.
    48. Ngwira, A.R.; Aune, J.B.; Mkwinda, S. On-Farm Evaluation of Yield and Economic Benefit of Short-Term Maize Legume Intercropping Systems under Conservation Agriculture in Malawi. Field Crops Res. 2012, 132, 149–157.
    49. Brooker, R.W.; Bennett, A.E.; Cong, W.-F.; Daniell, T.J.; George, T.S.; Hallett, P.D.; Hawes, C.; Iannetta, P.P.M.; Jones, H.G.; Karley, A.J.; et al. Improving Intercropping: A Synthesis of Research in Agronomy, Plant Physiology and Ecology. New Phytol. 2015, 206, 107–117.
    50. Lithourgidis, A.S.; Dordas, C.A.; Damalas, C.A.; Vlachostergios, D. Annual Intercrops: An Alternative Pathway for Sustainable Agriculture. Aust. J. Crop Sci. 2011, 5, 396.
    51. Smith, J.; Pearce, B.D.; Wolfe, M.S. Reconciling Productivity with Protection of the Environment: Is Temperate Agroforestry the Answer? Renew. Agric. Food Syst. 2013, 28, 80–92.
    52. Blanco-Canqui, H.; Shaver, T.M.; Lindquist, J.L.; Shapiro, C.A.; Elmore, R.W.; Francis, C.A.; Hergert, G.W. Cover Crops and Ecosystem Services: Insights from Studies in Temperate Soils. Agron. J. 2015, 107, 2449–2474.
    53. Baraibar, B.; Hunter, M.C.; Schipanski, M.E.; Hamilton, A.; Mortensen, D.A. Weed Suppression in Cover Crop Monocultures and Mixtures. Weed Sci. 2018, 66, 121–133.
    54. Thorup-Kristensen, K.; Magid, J.; Jensen, L.S. Catch Crops and Green Manures as Biological Tools in Nitrogen Management in Temperate Zones. In Adv. Agron; Elsevier: Amsterdam, The Netherlands, 2003; pp. 227–302.
    55. Teasdale, J.R.; Abdul-Baki, A.A.; Bong Park, Y. Sweet Corn Production and Efficiency of Nitrogen Use in High Cover Crop Residue. Agron. Sustain. Dev. 2008, 28, 559–565.
    56. Peachey, R.E.; William, R.D.; Mallory-Smith, C. Effect of No-till or Conventional Planting and Cover Crops Residues on Weed Emergence in Vegetable Row Crop. Weed Technol. 2004, 18, 1023–1030.
    57. Wallace, J.; Williams, A.; Liebert, J.; Ackroyd, V.; Vann, R.; Curran, W.; Keene, C.; VanGessel, M.; Ryan, M.; Mirsky, S. Cover Crop-Based, Organic Rotational No-till Corn and Soybean Production Systems in the Mid-Atlantic United States. Agriculture 2017, 7, 34.
    58. Singh, H.P.; Batish, D.R.; Kohli, R.K. Allelopathic Interactions and Allelochemicals: New Possibilities for Sustainable Weed Management. CRC Crit. Rev. Plant Sci. 2003, 22, 239–311.
    59. Nichols, V.; Martinez-Feria, R.; Weisberger, D.; Carlson, S.; Basso, B.; Basche, A. Cover Crops and Weed Suppression in the US Midwest: A Meta-analysis and Modeling Study. Agric. Environ. Lett. 2020, 5, 20022.
    60. Brust, J.; Claupein, W.; Gerhards, R. Growth and Weed Suppression Ability of Common and New Cover Crops in Germany. Crop Prot. 2014, 63, 1–8.
    61. Myers, R.; Watts, C. Progress and Perspectives with Cover Crops: Interpreting Three Years of Farmer Surveys on Cover Crops. J. Soil Water Conserv. 2015, 70, 125A–129A.
    62. Osipitan, O.A.; Dille, J.A.; Assefa, Y.; Radicetti, E.; Ayeni, A.; Knezevic, S.Z. Impact of Cover Crop Management on Level of Weed Suppression: A Meta-Analysis. Crop Sci. 2019, 59, 833–842.
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