Interaction of Some Cultural Practices and Reduced Herbicide Rates Used for Water Conservation Through Weed Control

1. Introduction

One of the biggest challenges in agriculture is the management of water, widely considered the greatest limiting resource for crops [1,2]. This limitation is especially important and evident in the arid and semi–arid environments [3,4]. Crops consume large quantities of water [5], and most of it is lost by transpiration to the atmosphere. On the other hand, weeds directly compete with crops for water, limiting its availability for crop growth [6]. Limited soil water availability influences crop–weed competition to a significant degree, and in general, weed growth is favoured due to the greater plasticity of weeds as compared to crops [7,8]. Because of that, weeds consume water intended for crops, cut water availability, and contribute to crop water stress [9,10]. Particularly, during years of water shortage when moisture is in short supply, weeds can reduce crop yields more than 50% through moisture competition alone [11]. In that context, growth of Chenopodium album, Kochia scoparia, and Salsola tragus is less affected by a shortage of moisture than is growth of many crops [12]. Generally, the weeds are known as great water wasters [13,14]. Certain common annual weeds associated with crops consume up to three times more water than crop plants to synthesize an equivalent amount of dry biomass. For example, Chenopodium album requires 658 pounds of water to produce one pound of dry matter, and Amaranthus retroflexus 912 pounds, compared with 349 pounds for corn and 557 pounds for wheat [12]. Other competitive annual weeds also show negative values. It has been estimated that one Sinapis arvensis uses as much moisture as four wheat plants [15], and one Salsola tragus uses as much moisture as three sorghum plants. Roots on some weeds, such as Salsola tragus, develop much faster than roots of the crop with which it is competing. This allows the faster-developing weeds to reach deeper soil moisture first [16].

Water conservation is defined as minimizing the loss or waste, care and protecting water resources and the efficient use of water [17,18]. There are many ways to conserve water. One of them is effective weed control. Mulching is the practice of covering the soil surface to make favourable conditions for plant growth and development. The main objective of mulching is water saving and weed control [19,20]. Mulches when spread over the soil surface, minimize the water runoff [21], increase infiltration [22], provide shade to the soil (suppress weeds) [23] and act as barrier to reduce water loss in form of vapours [19]. Green manures cover the soil surface [24], blocking light and altering the temperature and moisture at the soil surface [25] in ways that can impede weed germination or interfere with weed growth [26]. Some green manures are also allelopathic, containing or secreting compounds that can inhibit the germination of the weeds [27,28]. Weed control through cover crops management has several impacts on soil properties and effects soil and water conservation due changes on soil structure in the row and interrow crop [29,30]. Cover crops and cropping residues serve as a protection for the soil surface against weather aggressions and water erosion [31], to maintain soil moisture [32], to suppress weed growth [33] and to provide shelter and food for the soil biota [34]. According to Meschede [35], besides the allelopathic effects, a proper use of cover crop can provide control of weed plants by altering of several system features, such as thermal regimes, incidence of light and physical barriers to emergence, and also increasing rainwater retention, soil humidity, organic matter content, microbial activity, predation and overcoming of seed dormancy. Crop rotation is an essential practice in sustainable agricultural systems, because its effects on soil fertility [36], water conservation [37] and other benefits including reduction on weed competition [38,39]. Further, mixed cropping (polycropping, intercropping) systems offer a yield buffering capacity by diverse growing demands and different periods of root, leaf and seed development of the plant varieties. Mixed cropping systems are an efficient way to suppress weeds, particularly in competition for water and light can offer weed–suppressing capacities [40,41]. Finally, herbicides prevent some weed seeds from germinating [42] and, therefore, cutout water use by such weeds [43], thus good water management contributed to lesser weed growth resulting in lesser weed density and biomass irrespective of treatment [44].

Taking into account what has been mentioned previously, the present review has covered a great deal about the reduction of water losses caused by weeds and shows the potential of some cultural practices in interaction with reduced herbicide rates for water conservation through control of the weeds.

2. Material and Methods

This review is based on a qualitative literature review approach. Scientific literature was searched on Google Schoolar and included publications published between 1975 and 2025, with focus on articles published in English. The search was performed using keywords and phrases related to weed control and water conservation, including “water loss caused by weeds”, “weed control by mulching and herbicides”, “weed suppression by green manure”, “weed suppression by cover crops and herbicides”, “weed control by crop rotation and herbicides”, and “weed control by intercropping”.

Publications were selected according to their relevance to the topic of the review, specifically studies dealing with weed competition for water, weed suppression, soil moisture conservation, and the effects of different weed management practices on water availability for crops. The selected publications were reviewed and grouped according to the main weed management approaches discussed in the literature: water loss caused by weeds, mulching and herbicides, green manure, cover crops and herbicides, crop rotation and herbicides, and intercropping. In total, 190 publications were included in the qualitative synthesis. The number of publications identified for each thematic category is presented in Table 1.

3. Mulching and Weed Control

Weeds compete with crops for nutrients, air, and water [45], while urbanization and global climate change will likely continue to cause limitations in water availability in some areas [46,47,48]. Mulch can address both of these problems since application of mulch on a substrate surface can reduce, even eliminate weeds and reduce the frequency of irrigation [20,49]. Mulches control weeds by restricting the light penetration into the soil [50,51,52], inhibiting germination and thus suppressing weed growth [53,54]. A number of studies have documented that straw mulch is an effective means of decreasing weed emergence and growth [55], conserving soil moisture [56], reducing erosion [57] and increasing soil biological activity [58]. In the study by Jodaugienė et al. [59], straw was the mulch that limited weed germination the most at the beginning of summer, by 3.5–14.1 times. In a study by Mohtisham et al. [60], straw mulch reduced the number of germinating weeds by half, compared to the non–mulched control. Mulching decreased the number of weeds in a study by Sinkevičienė et al. [61], as well. According to the authors, among the few organic mulches applied for soil mulching, straw mulch was the best for weed control. In plots with straw mulch, weed density was 2.8–6.4 times lower compared to the weed density in plots without mulch. In the study by Din et al. [62], soil mulching with wheat straw in corn cultivation contributed to a decreased mass of weeds, by an average of 27.1%, compared to the plot without straw. Similarly, wheat straw and canola straw mulches deceased weed density by 84% and 79%, and weed biomass by 16 and 18%, respectively, compared to weed infested plots [63]. In studies by Fisk et al. [64], plant mulches reduced the number of annual weeds from 41% to 78%, and weed biomass from 26% to 80% compared with non-mulched soil. Barberi & Mazzoncini [65] showed that rye much reduced weed biomass from 54 to 99%, but weed–growth suppression was usually higher in the years when cover crop biomass was higher. Dhima et al. [66] reported a reduction in the germination of Echinochloa crus–galli by 69% when straw mulch of barley, triticale and rye was applied in sugar beet crops. In desert pepper production, the weed population in cowpea mulch was reduced by 80% and 90%, compared with the control, for both years. Weed dry weights in cowpea mulch were 67% and 90% less than those in control over the same period [67]. Shen & Zheng [68] investigated the efficacy of bio–based liquid mulch on weed suppression and water conservation. They concluded that weed count was reduced by at least 61% in all liquid mulched treatments compared to the control. The 1.25 and 2.0 kg/m² rates were more effective for weed control than the low application rate (0.5 kg/m²) and there were no differences between binder loading types (AMP753 with 3.5% binder loading or AMP153 with 7% binder loading). Further, the benefits of mulching and PRE–applied herbicides (i.e., under the plastic) is well documented, particularly in the control of some problematic weeds [69,70,71]. For example, Cyperus species are among the most troublesome weeds in vegetable production in many states [72], because they readily penetrate through the plastic mulch [73], herbicides integrated into the low–density polyethylene (LDPE) mulch–fumigant system must control these species. Halosulfuron [74]sulfentrazone [75], and metolachlor [76] all have activity on Cyperus species in pepper and tomato [77]. Johnson & Mullinix [78] reported that Cyperus esculentus was controlled by 88% with PRE applications of halosulfuron at 36 g ai/ha underneath plastic mulch. The concentration of halosulfuron required to reduce Cyperus esculentus dry weight by 90% (GR₉₀) for PRE–applied halosulfuron, according Adcock et al. [79] was 19.2 g ai/ha. Johnson & Mullinix [80] evaluated weed control in watermelon and cantaloupe grown on polyethylene–covered seedbeds in conjunction with various herbicide programs, including soil fumigation with metham sodium and PRE applications of either ethalfluralin alone (0.8 kg ai/ha) or ethalfluralin plus halosulfuron (0.8 kg ai/ha and 37 g ai/ha, respectively). Soil fumigation with metham–sodium followed by ethalfluralin plus halosulfuron applied PRE, controlled Cyperus esulentus by at least 89%. Santos et al. [81] reported that metolachlor applied PPI, followed by a shank–injected application of 1,3–dichlorpropene plus chloropicrin, and then followed by a POST application of trifloxysulfuron, provided >90% control of Cyperus spp. In line with the previous study, Gilreath & Santos [82] investigated Cyperus esulentus control in plastic–mulched tomatoes and reported that control was improved with a high rate of metolachlor compared with 1,3–dichloropropene (83%) or chloropicrin (17%).

4. Green Manures and Weed Control

Green manure has been used in different agricultural systems to assist in the elimination of weeds, through allelopathic effects, restricting growth space and competition for water, light, oxygen and nutrients and suppressing reinfestations [83,84,85]. Green manure tends to be slow growing. However, once established, certain green manures serve the dual purpose of smother crops, effectively outcompeting weeds and depriving them of essential resources such as sunlight, water, and nutrients [86,87]. Severino & Christoffoleti [88] evaluated the effects of the amount of green manure biomass on weed suppression and observed interactions between the amount of green manure used and the reduction in weed density and dry matter production; as the amount of green manure biomass increased, there was, in general, reduction in weed infestation. Faba bean as green manure in concentrations of 1% and 2% of soil dry weight reduced the germination, root and shoot elongation and aerial biomass of Echinochloa crus–galli and Amaranthus retroflexus by ca. 70% when the seeds were sown at the time of faba bean incorporation. In two field experiments conducted on land with a history of maize cultivation, in which faba bean biomass of 6700 and 12 100 kg/ha was incorporated into the soil, residue-mediated reductions of the density and biomass of naturally occurring dominant dicotyledonous weeds (Amaranthus retroflexus, Chenopodium album, and Solanum nigrum) and monocotyledonous weeds (Digitaria sanguinalis and Cyperus rotundus) were observed. At emergence, mean differences with respect to control plots ranged from −14.8% to −69.8% for density and from −46.9 to −78.5% for biomass [89]. Biennial or perennial green manures have a competitive advantage over spring–germinating weeds, and can also effectively suppress some perennial weeds. For example, including perennial alfalfa has been demonstrated to reduce Cirsium arvense populations, especially when the alfalfa stand is cut for forage [90]. In previous work [91,92], reduced Brassica kaber growth and interference were observed in sweet corn grown in soil amended with a Trifolium pratense green manure and composted dairy manure compared with sweet corn grown without organic amendments but fertilized with synthetic N. Bioassays showed less weed suppression with increasing time after amendment incorporation [91], indicating that tillage timing may modify the effects of soil amendment on weeds. Melilotus officinalis residues remaining after termination of growth continued to provide excellent weed suppression. Weed densities in April before planting the succeeding wheat crop were 75 to 97% lower in Melilotus officinalis than in untreated fallow treatments. Melilotus officinalis controlled the perennial weeds Taraxacum officinale, and Sonchus arvensis, as well as the Kochia scoparia, Descurainia sophia, Salsola tragus, and Bromus tectorum [93]. Because no difference in weed suppression was observed when Melilotus officinalis residues remained in the field or were removed, the authors speculated that isoflavanoid and phenolics released during growth and/or root decomposition may have explained some of the suppression. Dyck et al. [94] found Trifolium incarnatum residue reduced Chenopodium album biomass more than that of corn at 2 weeks after emergence (72% and 31% reductions, respectively). By final harvest, corn biomass following Trifolium incarnatum had recovered to levels achieved with chemical fertilizer, while Chenopodium album remained 39% lower relative to conventionally fertilized treatments. In greenhouse experiments, Brassica alba used as green manure crop and added to the soil at 20 g per 400 g of air-dry soil reduced the emergence of Capsella bursa–pastoris, Kochia scoparia, and Setaria viridis by 97%, 54%, and 49%, respectively. Rapeseed suppressed the emergence of Capsella bursa–pastoris, Kochia scoparia, and Setaria viridis by 76%, 25%, and 25%, respectively [95]. The emergence of Echinochloa crusgalli, Portulaca oleracea, Tribulus terrestris or Chenopodium album was reduced by 11–50%, 12–59%, 26–79% or 58–83%, respectively, in plots with aromatic plants used as incorporated green manure compared with green manure–free plots [96].

5. Cover Crops and Weed Control

Cover crops (living mulches) are planted between the rows of a main crop such as corn, soybean, etc., and are maintained as a living ground cover during the growing season of the main crop [97]. Cover crops have the potential to form an important component in agroecosystems and can be a useful tool for weed suppression in sustainable agricultural systems [98,99,100]. They control weeds through competition [101], allelopathy [102], weed seed decay in the seed bank [103], and the proliferation of residues [91]. Water competition is another mechanism by which cover crops suppress weeds [104]. Weed control when using a cover crop is dependent upon the amount of biomass on the soil surface and incorporated into the soil [105,106]. Suppression of Amaranthus spp., Setaria spp., Ipomoea spp. and Cyperus esculentus has been successfully achieved using cover crops [107,108]. Barnes & Putnam [109] and Weston [110] reported that cover crops such as rye, barley, and wheat reduced the early season biomass of various weeds by 48 to 98%, compared to no cover crop controls. Rye and Trifolium incarnatum cover–crop residues reduced density of Echinochloa crus–galli, Brachiaria platyphylla, Brachiaria ramosa, Ipomoea hederacea, var. integriuscula, and Euphorbia hyssopifolia, but did not affect Cyperus esculentus at 7 weeks after soybean planting in the absence of herbicides [111]. Mehring et al., [112] reported that weed control in irrigated potatoes was at least 90% for all cover crop treatments (rye/canola and triticale, hairy vetch and hairy vetch/rye) and termination treatments at all three evaluation timings (14, 29, and 51 days after planting). The use of Vicia villosa as a cover crop in temperate regions reduced weed density and weed biomass by 70–78% and 52–70%, respectively, compared with fallow treatments [113]. In addition, Teasdale and Mohler [114] showed that >75% inhibition of weed emergence is consistently achieved only when the mulch biomass and mulch thickness of Vicia villosa exceeds 8000 kg/ha. According to Mohammadi [115] weed dry weight was reduced by 34 and 50.9% when Vicia villosa was interseeded in corn at 25 and 50 kg/ha, respectively. Oliver et al. [116] also reported that Vicia villosa ssp. villosa living mulch established in soybean reduced Ipomoea lacunosa and Euphorbia maculata biomass by about 90% and Digitaria ischaemum biomass by about 70% compared to weedy controls. In another study, Fujii [117] reported that complete weed control can be achieved by direct application of Vicia villosa to the rice paddy fields, while Johnson et al. [118] observed that Vicia villosa mulch completely inhibited weeds under a no–tillage system. Kunz et al. [119] found that Sinapis alba, Raphanus sativus var. niger and Vicia sativa used as cover crops suppressed Chenopodium album, Matricaria chamomilla, Stellaria media by 60%. In the conventional system, the use of a rye cover crop resulted in a lower seedbank density compared with the crop residue treatment (–25%), whereas in the low–input system, the Trifolium subterraneum cover crop decreased weed seedbank density compared with the other cover crops (Trifolium incarnatum and rye) and the crop residue treatment (–22% on average) [120]. Of the five cover crop systems evaluated (1 year duration), the summer fallow and the yellow mustard ⁄ buckwheat ⁄ winter rape mixture consistently reduced the weed seedbank. The magnitude of decline in these high disturbance systems reached complete depletion of the Setaria spp. germinable seedbank and an 85% and 80% reduction for Chenopodium album and Abutilon theophrasti, respectively [121]. The combination of tillage and cover crops resulted in very high seedbank depletion rates, considerably higher than those under more conventional management. Teasdale et al. [122] reported >50% reductions in the germinable Amaranthus hybridus seedbank in years of good weed management in a soyabean cash crop. In another study that included eight locations across the US Corn Belt, Chenopodium album, Setaria faberi and Abutilon theophrasti seedbanks declined 40–47%, 78% and 42%, respectively over a 1-year period [123]. The allelopathic properties of cover crops can also be used to control weeds. For example, the allelopathic properties of Secale cereale, Lolium spp., and Trifolium subterraneum can be used to control weeds in sweet corn and snap beans [124]. Special weed control properties of winter turnip rape and other Brassica plants have been highlighted by Al–Khatib et al. [95], Petersen et al. [125] and O’Reilly et al. [126]. They are associated with the fact that these plants secrete isothiocyanates which are toxic to some weed species. It has been demonstrated that winter tur nip rape secretes substances which hinder seed sprouting of Sonchus asper, Matricaria inodora, Amaranthus hybridus, Echinochloa crus–galli and Alopecurus myosuroi des. [125]. In most cases the utilisation of allelopathic cover crops involves the use of their residues as surface mulch or the application of their extracts as post-emergence sprays in combination with reduced herbicide dosages [127,128]. The use of a rye cover crop with half the recommended rate of atrazine plus metolachlor in sweet corn resulted in excellent control of Amaranthus retroflexus and Cyperus esculentus in field experiments in Arkansas [129]. Wallace & Bellinder [130] reported that a no–till rye cover crop in conjunction with reduced rates of linuron, metolachlor, and metribuzin provided >90% Amaranthus retroflexus control and >93% control of Chenopodium album in sweet corn, snap beans, potato, and tomato. Wild radish or rye cover crops in conjunction with a half or full rate of atrazine and S–metolachlor controlled >95% Richardia scabra, Ipomoea hederacea, and Digitaria sanguinalis in sweet corn [131]. A multiplicative model that included a quadratic response to Vicia villosa residue and a log–logistic response to metolachlor, effectively showed that emergence of Amaranthus hybridus, Chenopodium album, Setaria faberi, and Abutilon theophrasti and early growth of Amaranthus hybridus and Chenopodium album were reduced synergistically. For example, Amaranthus hybridus emergence was reduced 13% by 500 g/m of Vicia villosa residue alone and by 16% by 10 g/ha of metolachlor alone, but together, they reduced Amaranthus hybridus emergence by 86% [132].

6. Crop Rotation and Weed Control

Crop rotation may be an effective practice for controlling serious weeds because it introduces conditions that affect weed growth and reproduction, which may greatly reduce weed density [133,134,135]. Dissimilar crop species with disparate management practices impose a wide range of stresses and mortality factors, creating an unpredictable environment to which the weed community is continually adjusting [136]. In addition, weed diversity has been shown to increase under crop rotation compared with monoculture [137,138]. It has also been suggested that weed densities are lower in crop rotation systems than in monocultures [139]. For example, the weed population in continuous winter wheat plots comprised 90% grass and sedge weeds, while in sugar beet–wheat rotation, it was only 43% of total weed density. Broadleaf weeds accounted 55.2% of the total weed density in continuous winter wheat, but only 9.4% in sugar beet–winter wheat [140]. Furthermore, crop rotations have been shown to maintain or decrease the number of weed seeds in the soi1 [141,142]. Forcella & Lindstrom [143] reported that after seven to eight years of weed management the number of weed seeds was about six times greater in continuous corn production than in a rotated corn–soybean system. Soybean–corn crop rotation reduced in–field and seedbank Conyza canadensis densities compared with continuous soybean in the third and fourth growing years [144]. Similarly, Covarelli & Tei [145] found three times as many seeds in the seedbank of continuous corn plots compared with wheat–corn rotational plots. The integration of Trifolium pratense in the sweet corn–peas–wheat rotation led to a 96% reduction in seedbank density of winter annuals [146]. Recommendations for control of Aegilops cylindrica in winter wheat in the Pacific Northwest include growing a spring wheat crop in the rotation to reduce the soil seedbank [147]. In the past, crop rotations involving spring or summer crops presented the best solution for controlling Bromus tectorum in winter wheat in Nebraska [148]. Additional research in Nebraska demonstrated that a 3–year winter wheat–fallow rotation that included a summer crop, reduced Bromus tectorum, Aegilops cylindrica, and feral rye [149]. By succeeding wheat with a clean winter fallow before sowing a summer crop, almost complete control of Avena fatua seedlings can be achieved, thereby eliminating seed production. Thus, as found by Philpotts [150] Avena fatua and A. sterilis ssp. ludoviciana populations could be dramatically reduced by winter–fallowing in association with the rotation of wheat and sorghum crops. One winter fallow reduced the population by 96.6% and two winter fallows reduced it by 99.8%. Similarly, Martin and Felton [151], showed that the rotation of wheat with sorghum, which allowed two winters for the control of Avena fatua either by cultivation or with herbicide, resulted in an exponential decline to low numbers of Avena fatua seed in the soil. The Bromus secalinus management programs in the Southern Great Plains, according Stone et al. [152] initiated following harvest of winter wheat, included conventionally tilled, double–crop grain sorghum (Sorghum bicolor) followed by soybean (Glycine max). Results showed that Bromus secalinus panicles as well as dockage due to Bromus secalinus in the succeeding wheat, were reduced by up to 87%, while Bromus secalinus panicles and dockage were reduced by up to 78% and 87%, respectively, by rotation out of winter wheat for one growing season. Similarly, Anderson et al. [153] investigated alternative crop rotations, with the goal of replacing winter wheat–fallow in the semiarid Great Plains. According to the results, the rotations with the lowest number of weed seedlings were winter wheat – fallow and spring wheat – winter wheat – corn – sunflower; in comparison, weed density was six–fold higher in winter wheat – proso millet. The density of Bromus tectorum and Kochia scoparia was highest in winter wheat – proso millet compared with the other rotations, whereas Eragrostis cilinensis and Setaria viridis were prominent in proso millet of the winter wheat – proso millet and winter wheat – corn – proso millet rotations. Replacing wheat with crops such as Trifolium alexandrinum, potato and oilseed rape for 2–3-year period in a rice–wheat cropping system significantly reduced the population of Phalaris minor [154]. In another study, the inclusion of alfalfa in the crop rotation sequence significantly decreased the interference of weeds in the subsequent crops [155]. Ominski et al. [156] conducted a survey in 117 fields in Manitoba, Canada, and found that rotation with alfalfa can effectively reduce the interference of Avena fatua, Cirsium arvense, Brassica kaber and Galium aparine in the subsequent cereal crops. Crop rotation had a significant effect on the growth of Echinochloa crus–galli, Sagittaria sagittifolia, and Alisma plantago–aquatica weeds. According to Filizadeh et al. [157] continuous rice planting produced the highest density of these weeds, compared with a rice–soybean–rice rotation. There were 62.5% and 80% reductions in weed density and weed biomass respectively, in the rice–soybean–rice rotation compared with continuous rice planting.

Another benefit of crop rotation may be associated with a lower chance of selecting troublesome weeds, because crop rotation sequence also determines herbicide use, and crop rotation and herbicide use can interact to affect weed species [158]. Therefore, the practice of rotating crops and herbicides has proved to be successful in influencing weed populations and improving crop production [159], and, given the increased attention paid to agroecosystem biodiversity, adopting weed management strategies that promote weed species diversity could be encouraged [160]. In an experiment with corn, soybean, and wheat, Doucet et al. [161] reported that combined use of crop rotations and herbicide management resulted in more effective weed control than either rotation or herbicide treatment alone. The results of the study of Heggenstaller & Liebman [162] indicated that rotations including triticale and lucerne with reduced rate of herbicides can facilitate the suppression of Abutilon theoprasti. Rotations that include lucerne can contribute to restraining Setaria faberi population growth, given adequate levels of seedling mortality in this crop. Mean weed biomass in corn and soybean was <25 kg/ha in all rotation×herbicide combinations except the low–herbicide 3–year rotation (corn–soybean–oat/red clover sequence), which contained∼110 kg/ha of weed biomass [163].

7. Intercropping and Weed Control

Intercropping has certain benefits in terms of production [164], soil health [165], water conservation [166] and system productivity [167]. In addition, intercrops offer significant assistance in weed control due to enhanced competition, physical dominance, space occupation, and allelopathic influence [41,168,169,170]. The addition of another crop species between rows can lead to smothering of and greater competition with weed species, minimizing their impact on the main crop being cultivated [171]. Intercrop treatments such as wheat–canola and wheat–canola–pea tended to provide greater weed suppression compared with each component crop grown alone, indicating some kind of synergism among crops within intercrops with regard to weed suppression [40]. Naeem et al., [172] found that mixed cropping of wheat + canola suppressed the dry weight of Phalaris minor, Chenopodium album, Rumex dentatus, and Coronopus didymus by 94%, 77.2%, 77.4%, and 92%, respectively, compared with sole wheat cropping. The other intercropping treatments, such as one row of wheat + one row of canola, two rows of wheat + two rows of canola, and four rows of wheat + four rows of canola generally suppressed total dry weight of weeds by 81%, 74%, and 76%, respectively. A significant reduction in weed density and biomass in wheat/chickpea intercrops compared with both sole wheat and sole chickpea crops was found by Banik et al. [173]. Strip intercropping of maize, common bean, and spring wheat markedly reduced the number of Galinsoga parviflora, Echinochloa crus–galli, Chenopodium album and Amaranthus retroflexus per unit area (by 50%), as well as the dry weight of their aerial parts [174]. Mixed cropping of peas with false flax in additive arrangements had a strong suppressive effect on weed coverage, i.e. 63% in the first and 52% in the second year, compared with sole pea cropping [175]. Taking linseed as the target crop for weed reduction, intolerable weed–cover of 34% and 54% in pure stands was significantly reduced in a mixture with wheat to an acceptable level of 10% by increasing the crop cover [176]. Field trials in Pakistan indicated that intercropping single and double rows of sorghum, soybean and sesame in a cotton crop reduced Cyperus rotundus density by 70–96% and its dry matter production by 71–97% [177]. Cotton + sunflower intercropping reduced total weed growth by 85% [117] and produced higher cotton equivalent yields and net income [178]. Intercropping sorghum with maize significantly reduced density and biomass of Cyperus rotundus, Convolvulus arvensis and Trianthema portulacastrum [179]. Intercropping of sorghum and sunflower with cotton suppressed weeds significantly by 62.4% and 59.6%, respectively and significantly enhanced growth and yield traits of cotton, particularly seed cotton yield in comparison with no weeding [180]. Bilalis et al. [181] reported that intercropping maize with legumes considerably reduced weed density in the intercrop compared with a maize sole stand due to decreased light availability for weeds in the maize–legume intercrops, which led to a reduction in weed density and weed dry matter compared with sole crops. Recently, it was demonstrated soybean–maize intercropping significantly diminished the biomass of Amaranthus retroflexus and Datura stramonium [182]. Intercropping systems with leguminous species are particularly beneficial for farmers struggling with Striga asiatica or Striga hermonthica infestations: one 7–year study in Kenya determined that several edible legume species, including crotalaria and ground–nut, reduced Striga hermonthica emergence by up to 35% [183]. A more recent study by Midega et al. (2017) indicated that drought–tolerant Desmodium uncinatum and Desmodium intortum significantly reduced Striga incidence in sorghum–Desmodium intercropping systems. Intercropping cassava with compatible crops is one of the effective approaches of weed management in this crop [184,185]. Osundare [186] recorded weed densities of 94, 96, 97, and 96 plants/m² for cassava–cowpea, cassava–peanut, cassava–pigeon pea, and cassava–soybean combinations, respectively, compared with 132 plants m/² for sole cassava. Zuofa et al. [187] reported 13% reduction in weeds in cassava–maize intercropping, and a higher reduction of 16–40% when slow-growing smother crops such as peanut, cowpea, or melon were intercropped with cassava. Moreover, compared to a cassava sole crop, an okra–cassava intercrop decreased weed competition by around 40–45% [188] while a cassava–pumpkin intercrop decreased weed growth by 70–100% [189]. In principle, weed suppression has often been found to be greater in intercrops compared with sole crops. For example, Liebman & Dyck [190], in an extensive literature review, reported that weed biomass in intercrops was lower than that in component crops in 50% of the studies, intermediate to component crops in 42% of the studies, and greater than that in all component crops in 8% of the studies.

8. Conclusions

Efficient weed control is essential for sustainable agriculture, offering numerous benefits, including water conservation. Mulching, green manures, cover crops, intercropping and crop rotation in interaction with reduced herbicide rates are essential multifunctional agricultural practices that can successfully address weed problems while minimizing water loss as one of the key components of agroecosystem vitality and stability. In order to effectively evaluate the contributions of these measures, a holistic approach is essential. This approach must address not only the concrete agronomic benefits, but also the broader agroecosystem services they provide, concentrating on long-term sustainability. This research topic acts as a significant resource for enhancing our understanding of mulching, green manures, cover crops, intercropping and crop rotation, facilitating more informed decisions about their implementation and optimizing their advantages, particularly in integrated weed management. As we continue to explore the potential of these practices, it is imperative to evaluate them with a comprehensive perspective, ensuring that we consider economic, social, and environmental dimensions.