Effect of Invasive Aquatic Plants (Azolla a., Myriophyllum a. and Cyperus a.) Biochar Amendment on Maize Growth: An Assessment

The management of invasive aquatic plants (IAPs), which is primarily accomplished through manual grubbing, incurs significant costs for populations, especially since the operations must be renewed on a regular basis. Converting IAPs into biochar for use as soil amendment will help offset the costs of this mechanical control strategy, while also improving carbon sequestration, soil fertility and crop yields. The objective of this study is to examine the effects of using IAPs biochar amendment on the quality of acidic soils and subsequently maize growth. Ten treatment groups including nine treatments and one control were established with four replicates each on freshly sown maize soils. Treatments options include applying IAP biochar (group 1), different combinations of IAP biochar and poultry manure (group 2), and mineral fertilizer (group 3). After 37 days, the average height of maize plants in the control group is 68.83±7.91cm, compared to 69.82 ± 7.34 cm (group1), 64.44 ± 7.82cm (group 2) and 69.08 ± 9.51cm (group 3). Multivariate analyses suggest that the IAPs biochar have significantly higher potential to improve plant growth parameters than either poultry manure or synthetic fertilizer. Based on the foregoing, the use of IAPs biochar amendment should be promoted among smallholder farmers because it is environmentally friendly, easy to produce, has a lower operational cost than other fertilizers, and has been shown to improve the acidic and impoverished dryland soils prevalent in Burkina Faso.


Introduction
Invasive alien species are one of the five top drivers that pose serious threats to biodiversity, ecosystem services, ecosystem health and livelihood security (Intergovernmental Platform on Biodiversity and Ecosystem Services, IPBES, 2018), These non-native taxa proliferate, disperse and persist in environments that are not originally their own, to the detriment of native species (Mack et al., 2000). In freshwater systems, biological invasion leads to altered hydrology, disruption of aquatic food web structure and changes in the biotic composition of invaded ecosystems (Strayer, 2010, Hussner et al., 2017. In Burkina Faso, several invasive aquatic plants in particular, Eichhornia crassipes (Mart.) Solms, Azolla africana (Desv.), Myriophyllum aquaticum (Vell.) Verdc., Cyperus articulatus L. (Cyperaceae) are threatening wetlands of the country (PNGIRE, 2016). These invasive aquatic plants degrade water quality and reduce its groundwater volume by raising evaporation rates by between 3 and 7% as compared to pristine water bodies (MAAH, 2016). They limit the accessibility and availability of water for human, livestock, and wildlife use and provide habitats for vectors of waterborne diseases (malaria, bilharzia, cholera, and onchocerciasis).
with and restrict the spread of invasive aquatic plants. Unfortunately, the methods that are often used are costly and have not been particularly effective. Past studies (Almoustapha and Millogo-Rasolodimby, 2006;Egnankou, 2016) have shown that converting aquatic invasive plants into compost has the potential to reduce their spread, while providing alternate fertilizers for local farmers.
The production and application of biochar material to agricultural fields, is a new technology increasingly promoted as crop residues and organic waste management, soil fertility improvement and climate change mitigation (Woolf et al., 2010;(Lompo et al, 2021a&b). Biochar is a substance with a high stable carbon content that can be obtained by the pyrolysis (that is, relatively low temperature in the absence of oxygen) of any form of biomass, including crop, tree residues and manure Joseph, 2009, Verheijen et al., 2010). Biochar has the ability to increase soil quality and crop production while sequestering carbon (Lee et al., 2015). In general, the use of biochar as soil amendment increases plant growth and crop yields by up to 200% in tropical areas (Yao et al., 2012;Mukherjee and Lal, 2013;Adekiya et al., 2020;Lompo et al, 2021b). Biochar is a promising material, which is generating a lot of interest around the world.
Hence, this study was conducted in order to assess the potential of biochar produced from combined IAPs (Azolla a., Myriophyllum a., and Cyperus a.) on soil fertility and morphological parameters of maize plants. This is with a view to contribute to improving quality of acidic soils in Burkina Faso, and by so doing, agricultural yields and the livelihoods of smallholder farmers.
We hypothesised that biochar obtained from invasive aquatic plants could enhance agricultural productivity (maize plant growth) and aid in soil fertility management.

The Study Area
The study was carried out in 2020. The experimental farm plots are located in Kadomba (11°32'28''N and 3°58'52''W), a rural community of Satiri department of Houet province in the Hauts-Bassin region. It is located 9 km northeast of Bala, and 50 km from Bobo Dioulasso the second largest city of Burkina Faso. Kadomba is characterised by a south Sudanian climate with an average annual rainfall of 1100 mm over a period of 4 to 5 months. The wet season lasts from May to October with 62.5% relative humidity and the dry season from November to April with relative humidity between 20.5 and 44.2%. December is usually the driest month with an average rainfall of 6.2 mm. Average temperatures are high: annual maximum temperature of 32.2°C is recorded in March and minimum of 25.4°C in December (Ouedraogo, 1994;Taita, 1998).
The soils of Kadomba are hydromorphic with pseudogley materials of various textures (ORSTOM, 1968). They appear in the form of strips and vast plains along the main drainage axes (Mouhoun and Sourou in particular).

Plant Material
Journal of Agricultural Studies ISSN 2166-0379 2021 The plant material used in this study was Zea mays L., Barka variety. This variety has a short cycle of 70 to 85 days between sowing and maturity. It has a potential yield of 5.5 t/ha. The seeds are white in colour and have a horny texture. It is pests and drought tolerant and can be cultivated either as rainfed or irrigated.

The Tested Soil Fertilizers
The amendments used in this study were: 1) biochar produced from the pyrolysis of three invasive aquatic plants-free floating Azolla a. (mosquito fern), Myriophyllum a. (parrot's feather with submergent and emergent feathery leaves, and Cyperus a. (jointed flatsedge); 2) poultry litters collected from a poultry farm, and 3) mineral fertilizers.

Harvesting of IAPs and Production of Biochar
The IAPs were harvested from a N/NW-S/SE elongated lake of about a length of 2.6 km and breadth of 700 m. Its surface area varies from 120 to 660 ha depending on the flooding of the Mouhoun River with which it is hydrologically connected. Its average depth is 2 m during low water period, and 0.5m is silted. This lake is located within the The Bala (Mare aux hippopotames) Biosphere Reserve, also located in the province of Houet (Haut-Bassin region), about 50 km northeast of Bobo Dioulasso, straddling the Departments of Satiri and Padé ma. It is surrounded by ten villages to which are attached several large farming hamlets with an estimated total population of 40,000 inhabitants. It is located in the west of Burkina Faso, between latitudes 11°30' and 11°45' N latitude and longitudes 4°05' and 4°12' W longitude. The Mare aux Hippopotames Biosphere Reserve (MHBR) has a surface area of 19,200 ha (Belem 2008). This lake is well-known for its hippopotamuses (Hippopotamus amphibius), which live permanently in the lake, and give rise to the reserve's name, "Réserve de biosphère de la Mare aux Hippopotames". The main activities carried out by the populations around the Bala Biosphere Reserve are agriculture, animal husbandry, fishing, and hunting. However, IAPs invasions have led to a decrease in fishery productivity. For example, fish production in Bala is on a downward trend from 600 kg in 1966 to 150 or 200 kg between 2000 and 2006 (Belem, 2008) and fish biodiversity has decreased from 42 species in 1956 to 34 species in 1994. In 2006 only 17 species were commonly encountered.
Biochar was produced by a slow carbonization (roasting) of the dried invasive weeds in the presence of little oxygen using a cone kiln oven at a temperature between 200 and 290°C, at an average of 22 minutes for Cyperus a., 50 minutes for Myriophyllum a. and 80 minutes for Azolla a.

Biochar and Manure Analysis
Biochar samples were air dried in the shade, crushed and sieved at 2 mm and 0.5 mm mesh size for chemical analysis. The pHwater was carried out by the electro-metric method with a soil/water ratio of 1:2.5. To do this, 20 g of soil was taken and placed in a flask, then 50 ml of Journal of Agricultural Studies ISSN 2166-0379 2021 distilled water was added and the mixture obtained was stirred for one hour in accordance with the FSA standard. After stirring, the pH of the water was read directly from the HANNA pH meter with glass electrode. The determination of the total carbon content was carried out by the Walkley and Black (1934) method. The organic matter content was then determined from the organic carbon content using the multiplication coefficient of 1.724. The total nitrogen determination initially consisted of mineralizing the biochar samples with a mixture of sulfuric acid-selenium-salicylic acid by gradually heating it to a temperature of 100°C to 340°C. Then the total nitrogen was determined using a auto-analyzer (SKALAR). About total phosphorus, the mineralization wasidentical to that of total nitrogen. The dosage was done by automatic colorimetry with SKALAR. Ammonium molybdate and potassium antimony tartrate reacted in an acid medium with ascorbic acid to form a blue complex in the presence of phosphorus (P) whose absorbance is measured at 880 nm. The intensity of the coloration was proportional to the amount of P in the medium. For the total potassium, the mineralization method was identical to that described above for nitrogen. Potassium was determined by a Jencons flame emission spectrophotometer, following the method proposed by Walinga et al. (1989).
The recommended rate in the field is 5t/ha for a period of three years, renewable. For treatments T1, T2, T3 and T4 plots, 6 kg of biochar were applied corresponding to the recommended rate of 5t/ha. This quantity was reduced either by half (3 kg), or by 1/3 or 1/ 6 (1 kg) for the other biochar treatments. Treatments were randomly assigned to the plots.

Crop Cultivation and Maintenance
The experimental site was ploughed with a tractor prior to the delimitation of plots. The amendments were combined with the top 10 cm of soil by ploughing. Sowing was carried out on 18 January 2020. On all plots, three seeds of maize were sown per hole at a row spacing of Journal of Agricultural Studies ISSN 2166-0379 2021 40 cm and line spacing of 80 cm.
Each elementary plot had 6 rows of seed with 8 pots per row. The four central rows formed the useful area where the measurements were made and the other two rows at the ends were used as border lines, with one row per side. At 15 days, following emergence, the number of young corn plant was reduced to two in each plot. Subsequently, four plants were randomly selected and identified in each elementary plot to measure the growth parameters. These plants were then selected from the four rows of the useful plot, including one plant per row.

Measurement of Plant Growth Parameters
Weekly measurements of average plant height were taken with a graduated ruler. These measurements were taken from the collar of the plant to the last emerging leaf. Measurements began the third week after sowing and continued until the 37 th day after sowing (DAS). The diameters of the collars were also measured beginning the third week after sowing and continuing every week. The number of leaves per plant were counted from the third weeks onwards and continued every two weeks until the 40 th DAS. Dried leaves were included in the count.

Data Processing
The data from the experimental plots were analysed by analysis of variance (ANOVA) and compared using the Tukey-Dunnett Test (Fisher's Least Significant Difference) when significant (P < 0.05). Correlation coefficients were determined by the simple regression method. This was carried out with the XLStat version 2016 software.
Principal Component Analysis (PCA) was performed on the treatments. This allowed us to quickly know which of these treatments is the most efficient and effective (the best treatment among the 9 treatments). This was followed by the Hierarchical Ascending Classification, which grouped the treatments into classes.

Chemical Properties of Biochars and the Poultry Manure
Biochars have alkaline pH values ranging from 8.92 to 9.89 and high than the pH value of poultry manure which is almost neutral. The biochars have higher concentrations of C, O.M, and K compared to poultry manure. Poultry manure, on the other hand, has a high level of P compared to Azolla a.and Cyperus a.biochar and high N compared to Cyperus a.biochar. Concerning the C/N biochars have small values as compared to the poultry manure except for the Cyperus a.derived biochar ( Table 1). ISSN 2166-0379 2021 Table1. Chemical composition of biochar and poultry litters  Table 2 shows the results of the analyses of the growth parameters, i.e. height and collar diameter of the young maize plants on the 18 th , 30 th , 37 th DAS, and the number of leaves at the 37 th DAS. For these two parameters, the analysis of variance revealed non-significant differences at 5% threshold between treatments. In terms of crown diameter, plots with biochar derived from Myriophyllum a. (T2) has the plants with the highest diameters (on average 1.16 ± 0.18 cm). The plants on plots treated with a combination of biochar obtained from Myriophyllum a. and poultry manure (T6) were relatively smaller in terms of height and stem diameter with average values of 46.17 ± 4.04 cm and 0.89 ± 0.12 cm, respectively. However, this analysis of variance at the 5% threshold shows significant differences between treatments for the number of leaves on day 37. ISSN 2166-0379 2021

Typology of the different treatments
The second axis (F2) explains 14.49% of the information contained in the growth parameter measurements. The variable number of leaves on day 37 after sowing is positively correlated to this axis. Axis 2 mainly opposes plants with faster growth to those with relatively slower growth. It can be interpreted as the axis representing the result of the growth of the plants from the different treatments. The two axes alone explain 94.88% of the total information.   Figure 2 shows the distribution of treatments into different classes derived from the Hierarchical Ascending Classification (HAC) based on the variables used in the PCA. Three classes of treatments are distinguished. Each of these classes comprises between 30% (classes 1 and 2) and 40% (class 3) of the 10 treatments. Table 4 summarizes the characteristics of these different classes.

Class 1
This class accounts for 30% of treatments and is the second largest class in terms of staff numbers. It mainly includes treatments where the average height of the plants is 68.73 ± 0.40 cm. The collar diameters of the plants resulting from these treatments have an average value of 1.51± 0.03 cm. The average number of leaves of the plants resulting from these treatments is 10.27 ± 0.19. It includes treatments comprising either no input, mineral fertilizer (180 g) or a combination of biochar and poultry manure (1 kg biochar of Azolla a.+ 1 kg biochar of Myriophyllum a.+ 1 kg biochar of Cyperus a.+ 3 kg poultry manure). These treatments correspond respectively to T0, T8 and T9.

Class 2
This category also includes 30% of the treatments and similar to class 1, represents the second class in terms of number of plants and presents the plants with the best morphological parameters. In fact, it mainly includes treatments where the plants have an average height of 71.50 ± 1.49 cm. The average diameter at the collar of the plants resulting from these treatments is 1.63 ± 0.04 cm. The mean number of leaves of the plants resulting from these treatments is 10.66 ± 0.13. This class includes almost all the biochar treatments except for the treatment with Cyperus a.biochar (T3). This class is therefore made up of treatments with either Azolla a.biochar (6 kg), Myriophyllum a.biochar (6 kg), or a mixture of Azolla a.biochar (2 kg), Myriophyllum a.biochar (2 kg) and Cyperus a.biochar (2 kg). These treatments correspond respectively to T1, T2, and T4. So, biochar of Azolla a.and of Myriophyllum a.had a positive effect on plant growth parameter (included the combination of the two).

Class 3
This class accounts for 40% of treatments and is the largest class in terms of staff numbers. It mainly includes treatments where the average height of the plants is 63.55 ± 1.79 cm. The average collar diameter of the plants resulting from these treatments is 1.37 ± 0.03 cm. The average number of leaves of the plants resulting from these treatments is 9.62 ± 0.11. It includes treatments obtained either from the mixture of biochar (3 kg) and poultry manure (3 kg) or from biochar of Cyperus a. (6 kg). These treatments correspond respectively to T5, T6, T7 and T3 and had negative effect (no effect of biochar of Cyperus a., addition of poultry manure had no effect and more over seems to have negative effect). ISSN 2166-0379 2021

Discussion
The chemical composition of the three biochar-types are consistent with those of Unger et al., (2011) and Ding et al. (2016) who showed that the composition and availability of mineral elements in biochar differ depending on feedstock and pyrolysis conditions. According to Lange et al. (2018), the N concentration tend to be lower in biochar and are usually less than 6%. These results are supported by the findings in this study. Indeed, the N concentration was 1.997% for Azolla a.derived-biochar, 1.637% for the Myriophyllum a.-biochar and 0.797% for that of Cyperus a.-biochar.
Phosphorus plays a role in a range of plant metabolic functions and is one of the essential nutrients needed for plant growth and development. Phosphorus (P) is absorbed primarily Classe 1 Classe 2 Classe 3 ISSN 2166-0379 2021 during vegetative growth and, subsequently, most of the absorbed phosphorus is transferred to fruits and seeds during the reproductive stages (Zapata et al., 1994). According to Chan and Xu (2009), the contents of phosphorus in biochars vary according to the biomass type and pyrolysis conditions. The exceptional level of phosphorus contained in the biochar obtained from Myriophyllym a., (5 555.95 mg/kg) indicate that this biochar probably greatly increased the soil phosphorus content and will contribute to make it available to maize plants. Potassium (K) allows the flowering and development of the fruit and all reserve organs such as roots and tubers. Thanks to the potassium, the colouring of flowers and fruits is improved as well as the resistance to diseases. Considering the low potassium content of the soil before amendment (104.83 mg/kg), the high potassium contents of the different amendments (107 012.13 mg/kg for the biochar of Myriophyllum a., 46 163.45 mg/kg for the biochar of Azolla a., 40 565.35 mg/kg for Cyperus a.and finally 8 607.88 mg/kg for poultry droppings) probably contributed to the availability of potassium to the plants.

Journal of Agricultural Studies
The proportion of minerals from the various combinations could justify why there was no added influence of the combination of biochar (the same outcome with one or with the inclusion of three).
Several studies have shown that poultry manure raises levels of organic matter, cation exchange capacity, the number of microorganisms and their activities in soils (Guidi et al., 1988;MacLaren and Cameron, 1996). The addition of poultry droppings with other fertilizers would significantly influence all maize yield parameters. According to Gomgnimbou et al. (2016), poultry droppings are an excellent organic fertilizer for crops and could have the same impact as the mineral NPK fertilizer. Indeed, the nitrogen contained in poultry droppings is rapidly available to the plant. It is the same for the other fertilizing elements they contain. They are to be used as a fertilizer rich in nitrogen, phosphorus, potassium and calcium with a basic amending effect on the soil (Gazeau et al., 2012). The addition of poultry manure to biochars had no effect and seems to have negative effect on the growth of plants. The combination of the biochar of invasive aquatic plants that is rich with the already rich poultry droppings has resulted in the "burning" of plant roots.
The results of the analysis of the pH of biochar obtained from the studied invasive aquatic plants (8.92 for Azolla a.biochar, 9.58 for Cyperus a.biochar and 9.89 for Myriophyllum a.) show that they are likely to raise the pH of acidic soils. These results corroborate those of Chintala et al., 2014 andKombatanga (2015) who found that biochar increase soil pH. The results of the trials show that only biochars produced from Azolla a.and of Myriophyllum a.had a positive effect on plant growth (including the combination of both) and no effect of biochar of Cyperus a.. This is due to the fact that these two species (Azolla a.and of Myriophyllum a.) incorporate nitrogen and phosphorus. Indeed, Azolla a.has a symbiotic association with cyanobacteria. Symbiosis allows the fern to develop better by taking advantage of the ability of cyanobacteria to absorb atmospheric nitrogen. In addition, one of the growing conditions of Azolla a.is the supply of phosphorus and, to a lesser extent, calcium, magnesium and trace elements. Azolla a.is used as a biofertilizer in rice fields because of its ability to fix nitrogen in the soil and block light to prevent competition from other plants, and is rich in protein, essential amino acids, vitamins and minerals (Gillard 2017).
Myriophyllum a.is a perennial aquatic plant capable of growing both below and above the water surface and thrives in stagnant or low-flow nitrogen-enriched waters. Like Azolla a., the growth of Myriophyllum a.is promoted by nutrient inputs (nitrogen, phosphates, potassium) from fertilizer discharges and urban or industrial wastewater (Hussner and Champion, 2011). Unlike Azolla a.and Myriophyllum a., Cyperus a.is an aphyl plant, without leaves. It is a semi-aquatic species that colonizes the average depths of bodies of water and streams, on clay soils. Its capacity to incorporate nutrients (nitrogen, phosphates, potassium) is low compared to Azolla a.and Myriophyllum a.

Conclusion
The results of the trials show that the biochars obtained from Azolla a.and Myriophyllum a.had a positive effect on maize plant growth. This can be explained by the compositions and the properties of the species.
During this study, we found that poultry droppings, which are high-nitrogen fertilizers, in combination with biochar obtained from invasive aquatic plants, has a potential of influencing plant growth. However, the appropriate amount to apply need to be determined to avoid negative effects.
Our findings suggest that the biochar from IAP such us Azolla a.and Myriophyllum a., have higher potentials to improve plant growth parameters than either the poultry manure or mineral fertilizer.
Based on our findings, we suggest that the use of IAP biochar be encouraged among smallholder farmers (particularly those with farmlands close to wetlands), as it is environmentally sustainable, easy to produce, has a lower operating cost than other fertilizers, and with proven ability to improve the acidic and impoverished soils prevalent in Burkina Faso, a Sahelian country.