Bovine manure as a dispersing agent for weeds and invasive alien plants

Fertilization is the act of adding fertilizers to the soil in order to provide essential nutrients for the development of cultivated plants. However, the use of bovine manure can act as a source of weed propagules, including non-native species. Due to the importance and lack of research on the topic, the objective of the present study was to evaluate the seed bank present in bovine manure used by farmers in the municipality of Itabaiana, SE. For that, samples of bovine manure were collected in 10 rural properties in the municipality of Itabaiana, SE. The evaluation of the seed bank was carried out by accounting for emerged seedlings. Usual phytosociological indices were calculated for each species. Altogether 35 species were sampled, of which 28 native and seven non-native. The native species with the highest importance value was Euphorbia hirta, as it has the highest density (AD = 1122 ind.m2) and is present in 28 sample units. The non-native species with the highest importance value was Eleusine indica, because it has the third highest density (AD = 171.2 m2) and is present in 21 sample units. The obtained results reveal that bovine manure has a high number of weed, which is quite worrying, as they are species that generate important environmental and economic impacts.


Introduction
Fertilization is the act of adding fertilizers to the soil in order to provide essential nutrients for the development of cultivated plants (Brasil et al., 1999). They can be of two types: mineral or organic. The first type is in mineral form, that is, it is already ready to be used by plants. The second type, on the other hand, must first go through the mineralization process (Embrapa, 2021).
The use of organic fertilizers, such as manure, has advantages over minerals, because in addition to providing proteins, enzymes, vitamins, natural antibiotics, alkaloids and nutrients for plants (Finatto et al., 2013), they also favor the maintenance of edaphic fauna (Barros et al., 2002) and improve the soil structure by increasing its aeration and water retention capacity (Trigueiro and Guerrini, 2003). However, manure can act as a source of weed propagules (Pitelli, 1987), which can generate a substantial impact on crops.
Weeds are any plant that interferes in the interests of man and the environment (Pitelli, 2015). Because they need the same resources as cultivated plants, they compete with them for nutrients, water and light (Pitelli, 1987), many are host of pathogens (Sales-junior et al., 2012), causing food poisoning in animals (Brighenti et al., 2017), release allelochemicals into the environment (Cremonez, et al., 2013) and decrease the quality of pastures (Mascarenhas et al., 1999). Thus, weeds are responsible for significantly reducing the agricultural production (Silva et al., 2009).
Among the weeds are invasive exotic species, that is, non-native plants with the capacity to invade and impact natural and anthropogenic ecosystems. Although there is a vast literature on weeds, little is known about the contribution of invasive exotic species in this universe, as well as nothing is known about the influence of bovine manure on the dissemination of these species. In view of these issues and knowing that invasive exotic species are one of the main causes of global biodiversity loss (Williamson, 1996;Pagad et al., 2018), the objective of the present study was to evaluate the seed bank present in bovine manure used by farmers in the municipality of Itabaiana, SE.

Study Areas
The present study was carried out in the rural area of the municipality of Itabaiana, SE (Figure 1), which has the As' climate (tropical with dry and moderate summer and rainy winter) according to the Köppen-Geiger classification (Tenório et al., 2009). This region has a separation varying between 1,100 and 1,300 mm per year , with evapotranspiration of 800 mm (Vicente, 1999). The region is characterized as a transition region between Caatinga and Atlantic Forest . The predominant soil is the Planossolo Solódico Eutrófico type (Jacomine et at., 1975). Research, Society and Development, v. 10, n. 8, e9410816833, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i8.16833 Source: Authors.

Data Collection and Analysis
Three 200 ml samples of bovine manure were collected in 10 rural properties in the municipality of Itabaiana, SE. The samples were mixed in washed sand previously sterilized in an autoclave and later placed in aluminum trays. The trays were isolated in a greenhouse surrounded by fine mesh sombrite (30%) for 90 days, with daily irrigation. In order to know the origin of bovine manure, structured interviews were conducted with the owners of the rural units where the manure samples were collected.
These interviews sought to establish a relationship of place of origin of the manure with weeds observed in the experiment.
Evaluation of seed bank was performed by the accounting of emerged seedlings (Santos et al., 2010). The identification of the species was carried out by consulting the specialized literature and the control material deposited in herbariums. All species were collected, herborized and deposited at the Herbarium ASE of the Federal University of Sergipe, São Cristóvão, SE. The taxonomic classification was prepared according to the APG IV System (2016) and the spelling of the names of the authors of the species according to Flora do Brasil 2020 (2021).
Having the species list, they were classified according to their origin in native and non-native. The categorization was performed by consulting the specialized literature (Bionet-eafrinet, 2021;Cabi, 2021;I3N / Brasil, 2021;ISSG, 2021).
For each species were calculated absolute and relative values of density, frequency and importance value, the latter being obtained by summation of the densities and relative frequencies (Fabricante et al., 2016). The diversity of the seed bank was assessed using the Shannon-Weaver index (H ') (Shannon and Weaver, 1949) and evenness through the evenness index (Pitelou, 1977). The statistical analysis was performed using the software Past 2:17 © (Hammer et al., 2001) and formulas in Excel spreadsheet. Research, Society and Development, v. 10, n. 8, e9410816833, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org /10.33448/rsd-v10i8.16833

Discussion
From the reviewed studies, some had lower number of species compared to this study: In Balsas, MA, seven species were sampled (Diniz et al, 2017.); in Morrinhos, GO, 26 species (Ferreira, 2017); in Viana, MA, 12 (Corrêa et al., 2018) and in São Luís, MA, 13 . However, other studies showed a higher number: in Vargem Bonita, DF, there were 39 species (Carmona, 1995); in Ponta Grossa, PR, 49 species (Deiss et al., 2018) and; in São Luís Gonzaga, MA, 55 (Mesquita et al., 2016). Differences in the sampling effort, between the biome / ecosystem studied and in the methods of collecting soils and data, should explain the divergences between the results of the compared studies.
The families Poaceae, Asteraceae and Amaranthaceae were also quite representative in other studies, such as those developed by Ferreira (2017), Deiss et al. (2018) and Diniz et al. (2017). Many species of these families exhibit characteristics which favor these results, such as the production of large quantities of seeds and the dispersion in different environments (Lorenzi, 2006;Holm et al, 1977;And Pedrotti Guarim-Neto, 1998).
Some of the non-native species found in the present study (Eleusine indica and Melinis repens) are species intentionally introduced for pasture formation (Pastore et al., 2012;Fabricante, 2013;Fabricante, 2014). Others, however, were introduced accidentally (Amaranthus viridis, Amaranthus blitum, Dactyloctenium aegyptium and Eragrostis tenella) or were brought here for other reasons (feeding: Cucurbita sp.) and started to invade agricultural areas and pastures.
The presence of several non-native plants occurring together in bovine manure can corroborate to the hypotheses of facilitation (Bruno et al., 2003) and invasive meltdown (Simberloff and Von Holle, 1999;Simberloff, 2006), where the nonnative species may be facilitating the arrival and establishment of new non-native species through changes in the natural conditions of the environment. More studies are needed to better understand this situation.
All the divergences pointed out throughout the text must be the result of the selection of species that the animals make when feeding and the ability of the seeds to pass unharmed through their digestive tract. According to Deminicis et al. (2009), the passage of seeds through the digestive tract of cattle influences the composition and abundance of seeds.
Originally from Africa, Dactyloctenium aegyptium is popularly known as chicken-foot grass, parrot-grass and frog-hand grass. It competes with agricultural crops, decreases the quality of pastures, it is a host of crop diseases and has allelopathic potential (Fabricante, 2014 Brasil 2020Brasil , 2021.
The species Eragrostis tenella, also has the African continent as its origin. This species has the same impacts as the previous one (Fabricante, 2013)  The caruru or bredo, as it is popularly called Amaranthus viridis species, is originally from Central America. It is an allelopathic species that affects the resilience of invaded sites, is toxic to animals and impacts agriculture (Fabricante, 2013 The species Eleusine indica, vernaculously known as chicken-grass is an Asian plant with the capacity to affect agricultural crops (Corrêa, et al., 2016) and is host of agricultural pests (Belle et al., 2017). There is a confirmed occurrence in the On the other hand, Amaranthus blitum species is commonly known as pigweed-sheet-of-gourd and is originally from Europe (Schneider, 2007). Like other species, it affects agricultural crops (Macedo, et al., 2003). It has distribution in the Northeast (Pernambuco and Sergipe) and South (Paraná, Rio Grande do Sul, Santa Catarina) (Flora do Brasil 2020Brasil , 2021.
Through interviews carried out with farmers, it was found that the manure used in this study is originated in the municipalities of Monte Alegre, Nossa Senhora Aparecida, Nossa Senhora da Glória, Poço Redondo and Poço Verde in Sergipe.
All of them are in the Caatinga domains, which justifies the presence of some typical species of this vegetation, such as Axonopus compressus and Murdannia nudiflora.

Conclusion
The results obtained demonstrate that bovine manure has a high wealth of weeds, which is quite worrying, as they are species that cause damage to Brazilian agriculture. In addition, there are several non-native species that have substantial impacts on natural ecosystems.