This study was carried out in the Kindia region (specifically in the prefectures of Kindia and Forécariah). ( Figure 1 ) It is located in the north between 10˚15' and 13˚00' west, with a surface area of 28,873 km² and a population of 1,561,336 [13] . It offers a mosaic of environments with diverse potential (ocean, estuaries, rivers, mangrove swamps, freshwater lakes, lowlands, foothills, mountains). It has a hot, humid tropical climate, influenced by the monsoon, with abundant rainfall in excess of 2500 mm per year, averaging 1429.8 mm over six (6) months (mid-May to mid-November). Average annual temperatures range from 25 to 27˚C and average relative humidity hovers around 70%. This essentially agricultural region, with a predominance of fruit and vegetables, is one of the eight (8) administrative regions of the Republic of Guinea. It is made up of five prefectures or urban communes: Coyah, Dubréka, Forécariah, Kindia and Telimélé. Two of these prefectures were chosen on the basis of the volume of pineapple produced and the length of time they have been producing pineapples. These were Kindia and Forécariah.

The laboratory of the national soil service (SENASOL) in Conakry and the chemistry laboratory of the Institut Supérieur de Technologie in Mamou were used for the study.

The soil samples ( Figure 2 ) used for this study were collected using a jar and shovel in the prefectures of Kindia (Friguiagbe) and Forécariah (Maferinya) in the Republic of Guinea between 9 am and 12 pm. The soil surface was cleaned to remove any organic or other residues, then the shovel was driven into a depth of 20 cm, and the samples were taken to the laboratories to be dried, conditioned and then analysed.

The survey was conducted between June and July 2022 in Friguiagbé and Maferinyah. The survey was supplemented by field observations. A total of 10 pineapple farmers were interviewed on their respective farms during routine field work (clearing and ploughing). These farmers were randomly distributed in each prefecture, i.e. 05 farmers in Kindia and 05 in Forécariah. The questions administered were open-ended and closed-ended in order to obtain primary information on the socio-economic characteristics of the farmers (gender, age, occupation) and technical itineraries (cropping system, production, cultivated area, fertilisation and pest management). The data collected was entered into an Excel spreadsheet before being analysed. Univariate and bivariate descriptive analyses were carried out to represent the static series in the tables in the form of frequency, mean and percentage. R and Excel were used to analyse the data.

1) Determination of pH by the McLead method (1982)

Procedure

Weigh 10 g of dry soil sieved to 2 mm and add 25 ml of distilled water to a 100 ml beaker. Stir mechanically for 2 hours. Shake the beaker by hand before measuring the pH. Place the electrode in the suspension and take the reading once the value is stable [14] .

2) Determination of the sum of exchangeable bases using the Kapen HICDVITZ method.

Procedure

Weigh 10 g of dry soil sieved to 2 mm and place in an Erlenmeyer flask; add 50 ml of chloridric acid (0.1 N HCl), shake for one hour; filter into an Erlenmeyer flask; take 25 ml of this filtrate into a 100 ml beaker, boil for 2 min on a hot plate and add 3 drops of 1% phenolphthalein. Titrate with a 0.1 N solution of sodium hydroxide (NaOH) until a pale pink colour is obtained which is maintained for 1 min [14] . Calculate using the following formula:

S = (Af1 − Bf2) × 10/P (10 g)

P = Weight of sample

S = Sum of exchangeable bases in meq/100g

A = Control (NaOH value used for control titration)

(f1 * f2) = Correction factors for normality of 0.1 N chloridric acid

10 = Transformation coefficient for results in meq/100g soil

B = Quantity of ml of sodium hydroxide used for titration.

3) Determination of Organic Matter by the Anne method

Procedure

Weigh out 0.25 to 1g of ground soil. Pour into a 100 to 150 ml flask with 10 ml of 8% aqueous potassium dichromate solution and 15 ml pure H₂SO₄. Bring to the boil slowly. The flask is connected to an ascending condenser. Count the time from the first condensed drop. Allow to boil for 5 min. Allow to cool. Transfer to a 100 mL flask. Make up with rinse water. Take 20 mL (V) and pour it into a 400 mL beaker. Dilute to 200 mL. Add 1.5 g NaF to make the colour change more visible. Add 3 to 4 drops of diphenylamine. Titrate with 0.2 N Mohr’s salt solution. The initial blackish-brown or violet liquor turns green. A very sensitive change [14] .

Calculation

The organic matter (OM) content in the soil is estimated from the organic carbon (C) content using the following equation:

C% = 0.24 (a − b) × (13/V)/g

a = volume poured for the blank

b = volume poured for the sample

V: volume poured for the Fe (II) solution control

g: sample weight

MO% = C% × 1.72

1.72: Average carbon coefficient in soil organic matter.

4) Determination of the Cation Exchange Capacity (CEC)

Procedure

Weigh out 2.5 g of soil and mix well with 10 g of purified sand. Place a cotton swab at the bottom of a percolation tube and place a 1cm layer of sand (approximately 5 g) on top. Then introduce the mixture of soil and sand into the tube and cover with a 1 cm layer of sand (5 g). Leach the soil with 50 ml of 1 M ammonium acetate, collecting the percolate in 50 ml volumetric flasks. Percolate slowly at a rate of 30 drops per minute. Make up the volume with 1 M ammonium acetate and save for the determination of exchangeable bases. To remove excess ammonium acetate, wash with 50 ml of 96% ethanol. After washing, percolate 50 ml of acidified sodium chloride into a 50 ml volumetric flask, then make up the volume. For the blank test (purified sand only), proceed in the same way. Run the standard range, blanks and samples through the auto-analyser, total nitrogen manifold, sensitivity 0.60 for 50 mV.

Calculation

Draw the baseline and measure the peak heights of the standard range, blanks and samples relative to this line. Using the range, calculate the CEC values of the blanks and samples.

CEC (meq/100g) = (a − b) h (cm)

Where a = value in meq/100g for the sample.

b = value in meq/100g for the blank.

h = height of the peak

Accuracy: 0.1

5) Determination of assimilable phosphorus in HCl-NH4F extract (Bray II method)

Procedure

Weigh 1 g of air-dried soil in a test tube and add 7 ml of the extraction solution (ammonium fluoride and 0.2 M chloridric acid). Shake for 1 minute and filter immediately. Make a blank and collect the filtrate in a test tube. If the solution is not clear, filter through the same filter. Measure the phosphorus concentration of the range, samples and blanks on the autoanalyser, P-Bray manifold, sensitivity 1.00 for 50 mv. The concentration was calculated as follows: Draw the baseline and measure the peak heights of the standard range, blanks and samples in relation to this line. Using the range, calculate the phosphorus concentration of the blanks and samples.

P-Bray ppm = 7 × (a − b)

a = ppm P measurement for the sample

b = ppm P measurement for blank

Accurate to within 1 ppm

Note: the soil/solution extraction ratio and stirring time vary between laboratories.

6) Determination of Total Nitrogen

Procedure

Weigh 0.5 g of air-dried, finely ground (<0.5 mm) soil into a 50 ml volumetric flask. Add 0.75 g of catalyst, a few grains of carborundum and 1 or 2 drops of distilled water to moisten the soil. Then add 5 ml of concentrated sulphuric acid. The added water stimulates the decomposition of the soil particles and promotes good mixing with the sulphuric acid. Place the vials on a hot plate and heat to 200˚C for 1 hour. Then continue at 350˚C, until a clear or pale green mineralisate is obtained, then continue to boil gently for 30 minutes. Remove the flasks from the plate and leave to cool. Slowly add about 25 ml of distilled water in small portions. Leave to cool, make up the volume and mix well. Allow the mineralisate to settle to obtain a clear supernatant. Run the standard range and the digest through the auto-analyser, total nitrogen manifold, sensitivity 6.00 for 50 mV.

Calculation

Draw the baseline and measure the height of the peak of the standard range, blanks and samples in relation to this line. Then, using the range, calculate the nitrogen concentrations of the blanks and samples.

%N = 0.01 * (a − b)

Or a = ppm N for the sample

b = ppm for the blanks.

Accurate to within 0.01.

7) Determination of Potassium

Procedure

Weigh 2.5 g of air-dried soil and transfer it to a shaker bottle. Make a blank. Add 25 ml of the extraction solution and shake mechanically for one hour. Filter through a fine filter immediately afterwards. Measure the potassium concentration of the range, samples and blanks. Calculation method:

K in mg/100g soil = (a − b)

K₂O in mg/100g soil = 1.2 (a − b)

Or a = ppm K measured for the sample

b = ppm K measured for the blank

Accurate to within 0.01 ppm.

8) Determination of particle size composition

The particle size analysis was carried out using the Robinson pipette method [14] .

This method consists of destroying the organic matter, followed by dispersing the sample in distilled water in test tubes for 15 minutes. Shake the bouyouce cylinder by hand for a few minutes to homogenise the suspension. Place the cylinder on the bench and start the stopwatch. Gently dip the graduated density meter into the test tubes containing the suspension (water and soil) and take the density readings at 40 s and 4 min, i.e. the densities (D1 and D2). Shake the cylinder containing the suspension again for a few minutes, place the cylinder on the bench and wait 1 hour. A few minutes before the time has elapsed, note the temperature and gently dip the densimeter back into the suspension. Note the temperature and take the D3 density reading. Repeat after 2 hours: if it is identical to the previous reading; if it is different, continue the readings at 3 hours, until it is constant (then take this value as D3 ( Figure 3 ).