Nejayote (or residual water from the nixtamalisation process) used in this work was collected from a nixtamal grinder in the municipality of Amozoc de Mota, Puebla, Mexico. Nejayote was stored in 20-L plastic containers and kept refrigerated at 4˚C throughout the experimental work. Raw nejayote and nejayote treated by coagulation-flocculation were characterised following these physicochemical parameters: pH, electric conductivity, Chemical Oxygen Demand (COD), total colour, turbidity, total solids (TS), OM, and content elements (nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc). The pH level and electric conductivity were determined with a Conductronic PC 16 potentiometer. Furthermore, COD, colour, and turbidity were determined with a Merck 118 photometer. TS and OM were determined with a Thermolyn® Benchtop muffle, and total nitrogen was determined with a Kjeldahl of block SEV® digester. Phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc were determined using an atomic absorption spectrophotometer (Perkin Elmer AANALYST 200).

Treated nejayote was obtained from raw nejayote subjected to a coagulation-flocculation process with the Südflock® P-63 coagulant (alkali-activated aluminosilicate) and the Sumex Biofloc® A-01 flocculent (polyacrylamide, anionic polymer). This process reduced the organic content, colour, and turbidity with respect to raw nejayote. The coagulation-flocculation process applied to raw nejayote was previously studied in terms of pH, coagulant (Südflock® P-63) and flocculent dose (Sumex Biofloc® A-01) in a jar tester SEV® AM-3 with multiple agitators. Both the coagulant and the flocculent were provided by Süd-Chemie de México S.A. de C.V. The statistical analysis of the experimental data on the coagulation-flocculation process obtained with respect to pH, coagulant (Südflock® P-63) and flocculent concentration (Sumex Biofloc® A-01) allowed selecting the conditions of the coagulation-flocculation treatment to reduce the turbidity, colour, and COD with respect to raw nejayote. These conditions were established with the following parameters: pH = 9; 0.20 × 10⁻³ g∙L⁻¹ flocculent (Sumex Biofloc® A-01), and 7.5 to 11.5 g∙L⁻¹ coagulant (Südflock® P-63).

Bio-fertilisers were labelled as follows: BT, for a traditional bio-fertiliser with drinking water as a control; BNCQ, for a bio-fertiliser from nejayote treated by a coagulation- flocculation process; and BNC, for a bio-fertiliser from raw nejayote. BT is constituted by 19.20 L of drinking water, 11.00 kg of manure, 0.28 kg of ash, 1.10 kg of molasses, 6.60 L of milk serum, 0.70 kg of alfalfa leaves (Medicago sativa), 0.70 kg of xicalote leaves (Argemone mexicana), 0.11 kg of yeast, and 0.28 L of male human urine. The preparation process was as follows: 19.20 L of drinking water (for BT) or raw nejayote (for BNC) or nejayote treated by coagulation (for BNCQ) was added into a container. Then, we incorporated into the water 11.00 kg of manure, 0.28 kg of ash, 1.10 kg of molasses, 6.60 L of milk serum, 0.70 kg of alfalfa leaves (Medicago sativa), 0.70 kg of xicalote leaves (Argemone mexicana), 0.11 kg of yeast, and 0.28 L of male human urine. All these ingredients were mixed until a homogeneous product was obtained. Then, bio-fertilisers were placed in 20-L biodigesters and were hermetically sealed. Each biodigester was connected to a bottle containing 0.30 L of drinking water, to dissolve the CO₂ produced by fermentation. The mixture was allowed to ferment for 60 days. During this fermentation process, 0.83 L of serum and 0.55 L of molasses were added to each biodigester on four occasions (every 72 h). The biodigesters were kept in a cool and dry place throughout the fermentation stage. The total number of bio-fertilisers prepared is shown in Table 1, which also includes the number of treatments, the type of fertiliser (foliar or edaphic), the name of the treatment, the percentage of dilution used, and the corresponding symbol.

The bio-fertilisers for edaphic application were prepared with raw nejayote (NC) at different percentages of dilution. The total number of bio-fertilisers prepared from raw nejayote is shown in Table 1.

The research was conducted in the municipality of Amozoc de Mota, Puebla, Mexico, located at 19˚03'20.0 north latitude and 98˚03'06.0 west longitude, with respect to the Greenwich meridian and at 2331 MASL. The climate in Amozoc de Mota is mild and subhumid, with summer rains (100%). The temperature and precipitation ranges were 12˚C - 18˚C and 900 - 1100 mm, respectively. The soil in the region is composed of Leptosol (39%), Luvisol (20%), Arenosol (20%), Phaeozem (1%), and Durisol (1%). Blue maize culture in this plot was conducted on a temporary basis.

Before the date of sowing, soil samples were taken in a zigzag fashion across the len- gthand breadth of the plot and at a depth of 0.30 m. A composite sample was formed for physicochemical analysis. Four samples were collected 139 days after sowing (soil with drinking water and soil with raw nejayote at 50%, 75%, and 100%) for physicochemical analysis. The indicators of soil quality were as follows: pH, electric conductivity, cation-exchange capacity, carbonates, bicarbonates, chlorides, sulphates, OM, total nitrogen, phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, copper, zinc, texture, real density, apparent density, field capacity, permanent wilting point, usable moisture, irrigation lamina, and porosity. Variables were assessed on the basis of the Official Mexican Standard (Norma Oficial Mexicana) NOM-021- SEMARNAT-2000.

A randomised block design was established with the application of 10 treatments and five replications, using native blue maize (Zea mays L.) as an indicator plant of the conic group 1a [18] . Each of the 50 experimental units consisted of 7.0 m² with an inter-row distance of 0.70 m. To avoid interference between the blocks, they were separated by a row where no sowing was performed. Five seeds were sown per bush, with a distance between bushes of 0.50 m. When the plant reached 0.30 m of height, thinning was performed, and three plants were considered per bush. Each experimental unit was formed by 60 plants, with 18 plants per useful plot. During all the agricultural cycle, the maize cultivation was performed on a temporary basis, without irrigation of water, according to the prevalent technological circumstance of the region. Weed control was made by mechanical technique. The weeds were mowed each 15 days for remove the upper 0.12 - 0.15 m of taproot. The mowed weeds were taken away from the plot immediately. To avoid interferences with the proposed treatments (Table 1), any other fertilisers or input were not applied.

Fertiliser application from raw and treated nejayote included application on leaves (foliar) and soil (edaphic). In the case of foliar application, six treatments were applied with bio-fertilisers prepared at different dilutions, corresponding to treatments 1 - 6 of Table 1. In the case of edaphic application, four treatments were applied from dilutions of raw nejayote, corresponding to treatments 7 - 10 of Table 1, including the controls. A day before sowing, the seeds were moistened in the solutions of the respective treatments (Table 1). Then, the seeds were allowed to rest for 24 h before sowing. Cultivation was conducted from 1 May to 16 November 2015. Twenty-eight days after sowing, the first application of the foliar and edaphic treatments was performed. The following five applications were performed every 15 days. As the foliar area of the plant in the experimental units increased, so did the volume of foliar treatment, thus adding 45, 50, 55, 60, and 65 mL per bush at the first, second, third, fourth, and fifth applications, respectively. Soil applications of the treatments entailed flood irrigation. For this purpose, 3.00 L were utilised per bush. In each treatment, 30 plants were assessed to record plant height, stem diameter, and number of leaves, five times, every 21 days after 3 June. Maize cobs were harvested upon reaching physiological maturity. Two months thereafter, the grain moisture was measured with a moisture meter (TPM MD7822). Subsequently, the maize grain was weighed to calculate the yield.

For the field foliar and edaphic treatments applied on native blue maize crops, the response variables plant height, stem diameter, number of leaves, and grain yield were assessed, with five replications, using Statgraphics Centurion XVI 16.1.02. All the variables were measured and analysed by a one-way ANOVA with Bartlett’s test and a multifactor ANOVA with Tukey’s range test, with α = 0.05 for the response variables of the foliar and edaphic field treatments.

The physicochemical characteristics of raw nejayote and nejayote treated through a coagulation-flocculation process are presented in Table 2. Raw nejayote has a dark yellow colour; it is highly alkaline and turbid, with a high organic load (17,146 mgO₂∙L⁻¹) and electric conductivity. The content of nitrogen, phosphorus, potassium, calcium, magnesium, and iron is less than 1%. The content of calcium in nejayote is relatively high and mainly stems from the calcium hydroxide used in the nixtamalisation process. The concentration of calcium ions in nejayote is relatively high if compared to the effluents of the dairy or food industry [19] [20] . For agricultural purposes, Ca represents an alternative for controlling the degree of soil suppressiveness against microorganisms (e.g., Aphanomyces euteiches) [21] . The percentage of OM in nejayote is considerably high and is attributed to pericarp waste that comes off the maize grain, whose composition, according to Watson and Ramstad (1987) [22] , consists of ash (0.8%), starch (7.3%), sugars (0.3%), proteins (3.7%), ether extract (1%), and crude fibre (86.7%). The OM present in nejayote can contribute in a mineralised form to agricultural crops, by releasing nutrients of its chemical and moistened composition, thus improving the soil

Abbreviations are as follows: NTU: Nephelometric Turbidity Unit; ND: Not detected.

structure and facilitating the availability of chelated minerals in plants. Nejayote treated by chemical coagulation with 7.5 to 11.5 g∙L⁻¹ Südflock® P-63 coagulant and 0.2 × 10⁻³ g∙L⁻¹ flocculent (Sumex Biofloc® A-01) at pH 9.0 modifies the physicochemical properties of raw nejayote, significantly reducing the colour and turbidity and partially reducing the organic load and ion presence in the solution. The most significant physicochemical characteristics of raw and treated nejayote are presented in Table 2. The reduction in the physicochemical parameters of the nejayote treated by coagulation- flocculation generates a nejayote with a low concentration of organic and inorganic matter as a fertiliser in the agricultural processing of blue maize.

Table 3 presents the physicochemical parameters of the bio-fertilisers from raw and treated nejayote (BT, BCNQ, and BNC). Bio-fertilisers show pH values between 3.5 and 4.5 and an increased quantity of TS, turbidity, colour, OM content, and electric conductivity. The changes in the physicochemical characteristics of raw and treated nejayote are derived from the additional matter used in the preparation of bio-fertilisers (see Section 2.3). The increase in the electric conductivity of the bio-fertilisers observed indicates an increase in the content of salts or ions, as observed when comparing the data reported in Table 2 and Table 3. In the case of BNCQ, the electric conductivity has an additional ion contribution due to the bentonite used in the chemical coagulation treatment [23] . The total nitrogen and phosphorus content in bio-fertilisers is practically constant and in the same order of magnitude as the content from raw

Abbreviation is as follows: NTU: Nephelometric Turbidity Unit.

nejayote. The calcium content in bio-fertilisers mainly comes from nejayote obtained from alkaline cooking (calcium hydroxide) during the nixtamalisation process. Both hydroxide and calcium carbonate function as alkalis and neutralise the acid products resulting from fermentation. In addition, calcium increases the OM mineralisation speed that contributes to the mobilisation of nutrients for the plants, especially of cellulose material, thus stimulating the bacterial activity of decomposition [24] [25] [26] . Together with this mobilisation of nutrients, the fulvic acids produced by fermentation form chelates with the metal ions Mg²⁺, Ca²⁺, Fe²⁺, and Fe³⁺, which facilitate the transport and regulate the bioavailability of these nutrients at the foliar level [27] [28] . Furthermore, it has been reported that in sites where acid rain is registered, the foliar application of calcium can reduce the adverse effects on crop cells caused by free radicals [29] , thus promoting root growth and fruiting [30] .

We assessed the effect of foliar and edaphic application of raw and treated nejayote- based fertilisers during maize plant development by a statistical analysis of the experimental data obtained by Tukey’s range test (α = 0.05) of diverse response variables at different stages of crop development: plant height (cm), stem diameter (mm), number of leaves, and grain yield (t∙ha⁻¹). The different stages of crop development were classified as follows: 1) V5 (visible collar of the fifth leaf); 2) V8 (visible collar of the eighth leaf); 3) V9-VT (visible collar of the ninth leaf; last branch of the panicle visible); 4) VT-R0 (last branch of the panicle visible; male flowering) and 5) R1-R2 (visible stigmas in 50% of the plants; blister stage), as defined by Lafitte (1994) [31] .

Table 8 shows the physicochemical composition of soil before and after the application of the AP, NC50, NC75, and NC100 treatments. The soil texture was found to be loamy-sandy. This type of soil is easily eroded by wind [48] , lacks cohesion [49] , contains few exchangeable cations (Mg, K, and Ca), has low nutrient retention [50] , and presents high permeability, low water retention capacity, and low specific heat [51] . However, such soils are easy to culture [52] . Raw nejayote (characterised in Table 2) contains a high percentage of OM (61.48%) and calcium (0.94%). Therefore, the edaphic fertilisation with the NC50, NC75, and NC100 treatments doubled the percentage of calcium

ND: Not detected.

ions and OM in the soil. The highest percentage of OM and calcium was registered in the NC100 treatment (raw nejayote at 100%). When the calcium content increases in soil, generally, microbial growth is stimulated, thus positively affecting both nutrient availability and nitrogen fixation [26] . According to previous studies [10] [53] , the addition of OM to soil increases the total pore volume, promotes aggregation, diminishes bulk density, and increases water retention capacity. Marsden (1989) [54] indicates that the calcium content increases the rate of decomposition of organic sediment matter, especially of cellulose material, as in the case of nejayote, while reducing the risk of disease propagation and neutralising the acids produced in the anaerobic decomposition of the OM. This effect favours the release of nutrients, increasing their availability for the crop. After the application of the edaphic treatments NC50, NC75, and NC100, the electric conductivity showed a considerable decrease, with values below the threshold indicated by Cramer (1994) [55] . According to Wang et al. (2014) [56] , both calcium and the OM are effective for reducing soil salinity, which may explain the results obtained in terms of electric conductivity. Notably, an increase of the edaphic electric conductivity above 1.7 dS∙m⁻¹ negatively affects total soil porosity, bulk density, and structural stability [57] , thus preventing growth of maize plants [55] . Table 8 shows that the presence of elements such as nitrogen (N), phosphorus (P), and potassium (K) was considerably low before the treatments. After the application of AP and NC50 treatments, the percentage of nitrogen diminished, while after the NC75 and NC100 treatments, the percentage of nitrogen increased significantly, especially in the NC100 treatment. This result can be attributed to nejayote. After the application of the treatments, P and K were not detected. Therefore, these elements are most likely to have been completely consumed by the crop. Prior to the application of the treatments, the soil had a slightly alkaline character (pH = 7.45). However, after the treatments, the soil acquired a slightly acid character (pH: 5.85 - 6.26), which may have been caused by the acid character of the bio-fertiliser. Similar to K and P, sulfates ions were not detected after the application of the treatments, whereas Mg²⁺, Na⁺, and were not detected either before or after the applications. Most likely, their presence in nejayote was minimal, or they may have been completely consumed by the crop.