Identification of Insecticide Residues in Inceptisols at The Central of Horticultural Production, Banuhampu Agam West Sumatra

The high persistence of insecticides in soil and their toxicity to farmers and agricultural land are serious problems with insecticide application. This study was to identify and characterize insecticide residues on Inceptisol in the center of horticultural production, Banuhampu Agam West Sumatra. The determination of soil samples was carried out by purposive random sampling with a quantitative survey method. Sample testing using randomized completely block design (RCBD) with four slope levels and three points of sampling : 0-8%; 8-15%; 15-25%, and 25-45% in fields at a depth of 0-20 cm and forests (25-45% slope) as control. Insecticide residues on Inceptisol in the central of horticultural production, Banuhampu Agam West Sumatra, identified as many as 5 types, namely: Cypermethrin [C22H19Cl2NO3]; Permethrin [C21H20Cl2O3]; Profenofos [C11H15BrClO3PS]; Phenthoate [C12H17O4PS2], and Diazinon [C12H21N2O3PS]. Cypermethrin was the most highly contaminated insecticide residue found in soil at 0.1 mg kg−1 and is a pyrethroid insecticide. The effect of slope level was not significant on the identification of the number of active ingredients and total insecticide residue concentration. However, the highest number of active ingredients on 0-8% and 25-45% slope each amounted to 3 units, while the highest total concentration of insecticide residues on 0-8% slope amounted to 0.499 mg kg−1.


Introduction
Pesticides are substances derived from chemicals or other compounds used to kill and control pests and diseases in plants [1].The use of pesticides that do not meet the criteria can have adverse effects, such as acute or chronic poisoning, environmental pollution, and the occurrence of pests resistant to pesticides [2].Pesticides become harmful to soil because the active ingredients are artificial chemicals so foreign to the soil system, where the active ingredients of these pesticides will affect the balance of the sorption complex in the soil.This may affect the nutrient balance or soil acidity.After applying pesticides to plants, it will take a relatively long time to remove the pesticide residues left behind [3].Pesticide residues left in the soil will affect soil quality [4].Insecticides are organic compounds designed to be toxic to certain groups of organisms such as insects.Insecticides have been widely circulated with various types.The types of insecticides can be grouped into inorganic, organochlorine, organophosphorus, carbamate, pyrethroid, neonicotinoid, phenylpyrrole, pyrrole, avermectin, microbial, organofluorine, insect growth regulator, fumigant, repellent, synergist or activator and vegetable [5].
The use of chemical insecticides has many problems and negative impacts [6].Natural insecticides can be used as an alternative in tackling plant pest organisms.Reducing the use of chemical insecticides requires finding alternative controls that are environmentally friendly, including the use of bioactive materials (botanical insecticides, attractants, and repellents), natural enemies (parasitoids and predators and pathogens), and the use of adhesive traps [7] [8].Plant-based insecticides are single or compound active ingredients derived from plants that can be used to control pest organisms.The properties of plantbased insecticides are generally not harmful to humans or the environment and are easily decomposed compared to synthetic insecticides.Synthetic plant-based insecticides are used to kill and control pests and plant diseases.The impact of insecticide use can pollute the environment due to residues left behind, especially in the central area of horticultural production, Banuhampu Agam.Banuhampu, Agam is an area engaged in the Horticultural agriculture sector in Agam Regency.Soil types in Banuhampu, Agam are generally dominated by Inceptisols.
Inceptisols are one of the sub-optimal soil types that are widely utilized in various agricultural sectors.In general, Inceptisol shows a texture class with a fairly high clay content (35-78%) but some include fine loam with lower clay content (18-35%), pH close to neutral or above, base saturation less than 50%, high soil organic matter (1.64%-7.78%).Potential P is low to high and potential K is very low to medium.Potential P content is generally higher than potential K, both in the top and bottom layers.Cation exchange capacity (CEC) is moderate to high in all layers.Base saturation is low to high [9].Thus, the natural fertility of Inceptisol varies from low to high.This is why Inceptisol is widely found and utilized by farmers in horticultural production centers.However, crop productivity that must be increased requires farmers to use pesticides in uncontrolled applications to control plant pest organisms.This is the basis for pesticide contamination and residues on Inceptisol.Profenofos pesticide residue levels have exceeded the Maximum Residue Limit (BMR) set by The Japan Food Chemical Research Foundation (0.05 ppm < 0.204; 0.080 and 0.061 ppm) in lettuce plants [10].Therefore, it is interesting to study quantitatively through the identification of insecticide residues on some lettuce in the horticultural production center, Banuhampu Agam.

Materials and methods
This research was conducted from February to November 2022 in the central area of horticultural production, Banuhampu, Agam West Sumatra.Insecticide residue analysis was conducted at the Food Laboratory, Plantation Office of Food Crops and Horticulture of West Sumatra.

Soil sampling
Soil sampling includes: (a) Observing the physical condition of the land, where observations are made in the form of physiographic observation around the research location, and (b) Soil sampling, where the research sample was in the form of soil samples.Determination of soil samples was carried out by purposive random sampling.Soil samples were taken are disturbed soil samples with composites and undisturbed soil samples with rings at a depth of 0-20 cm.Sample testing using randomized completely block design (RCBD) with five treatments and three replications: 25-45% in forests and 0-8%, 8-15%, 15-25%, and 25-45% in fields, so that 15 soil samples were obtained.Survey activities were guided by the Technical Guidelines for Field Observations by the Soil Research Centers [11].Data analysis was also conducted through a Geographic Information System (GIS) (Figure 1).

Insecticide residue analysis
Residue analysis of organophosphate (phentoate, diazinon, and profenofos) and pyrethroid (cypermethrin and permethrin) insecticides.First, residual standard solutions of each insecticide were prepared using acetonitrile solvent.The parent standard solution was 100 ppm, then diluted to a concentration that gave a readable peak under standard conditions.25 g soil sample was added to 100 ml of isoctane and N hexane solution, then shaken for 1 hour.Next, the sample was filtered and the filtrate solution was taken, then the above method up to 3 times.After that, it was extracted with a rotary evaporator, and 5 ml of toluene 17 and isoctane solution was added.The resulting solution was put into a 1.5 ml vial and injected with GC-MS (Gas Chromatography-Mass Spectrometry) and the data graph at retention times of 8.73 (Diazinon); 12.68 (Phentoat); 14.21 (Prefonofos); 21.69 (permethrin) and 23.13 (Sipermentrin) minutes (Formula 1) [12].

1)
Where Based on interviews with local farmers the fields in each slope were included in intensive agriculture.Land processing was done using a hoe, and processing was done based on the land area owned by each farmer.Horticultural crops planted by the community were very diverse ranging from eggplant, chili, leeks, beans, tomatoes, shallots, and cauliflower.There were two cropping patterns used, namely monoculture and polyculture (intercropping).A monoculture planting pattern is a planting pattern used to cultivate only one type of plant in an agricultural area, while a polyculture planting pattern is a planting pattern used to cultivate two or more types of plants in an agricultural area.In the forest, the vegetation that grows are weeds, shrubs, large trees, and litter.This causes the forest to still be in a beautiful state and has not done much tillage.The use of fertilizers and the application of pesticides is quite high in the research location.There are 2 types of fertilizers used, namely natural fertilizers and artificial fertilizers, for the intensity of use of natural fertilizers is done only once before the planting period while artificial fertilizers for the intensity of used 3 or 4 times until harvest.Pesticides used also many types and trademarks such as Curacron, Astertin, Gramoxone, and others.The intensity of pesticide spraying was carried out 2 to 3 times a week at the rate of 2-3 spoons (20 ml) of pesticide mixed with 16 liters of water.The condition of the land at the research site is sloping ranging from a flat slope of 0-8% to a rather steep 25-45%, with conditions like this will trigger the accumulation of residues.This is because fertilizers and pesticides applied by farmers on rather steep slopes will be carried to flat slopes by rainwater, farmers applying fertilizers and pesticides are not under the recommendations and guidelines on packaged products, which they use according to the level of pests that attack [14].The more pests that attack the plants, the higher the dose given, if there are few pests, the dose used is also low.Thus this can lead to the accumulation of insecticide residues in the soil and plant [15].5

Identification and Characteristics of Insecticide Residues on Inceptisols in the central of horticultural production, Banuhampu Agam West Sumatra
Based on Figure 3, there were 2 types of insecticide residues found, namely organophosphates and pyrethroids, where the types of organophosphates found are prefonofos, diazinon, and phenthoat, while the pyrethroid groups found are cypermethrin and permethrin.At several points from 0-8%, 8-15%, 15-25%, and 25-45% slope where farmers do tillage there are indeed pesticide residues but on forest land, no pesticides were found.This is on agricultural land, tillage has been carried out for plant cultivation, where farmers usually provide organic matter, fertilizers, and even pesticides to support plant growth.Generally, farmers of horticultural crops, especially vegetables and fruits tend to use pesticides excessively to secure their products, although conceptually pesticides are the last alternative in controlling pests.Pesticide residues are mostly found in valleys, coastal plains, and highlands which are generally planted with vegetables.The forest the total residue level detected was insignificant and there was no trace of residues in the forest area, where among the 24 compounds identified from 66 locations, residues of 10 compounds were found [16].

Figure 3. Type of Insecticide Residues on Inceptisol in the central of horticultural production, Banuhampu Agam West Sumatra
Interviews with local farmers explained that each slope used various pesticides.The effect of seasonality showed no significant effect on insecticide residues found in the central horticultural production, Banuhampu Agam West Sumatra.However, the highest insecticide residue result was found in the 0-8% slope of 0.499 mg kg -1 with the number of active ingredients found in as many as 3 types (Table 1).There were several types of pesticides, namely insecticides, herbicides, and fungicides.Insecticides in the research location were made from the active ingredients abamectin benzoate, abamectin, profenofos, cypermethrin, imidacloprid, dimethoate, and methomyl.The dosage given by Types of active ingredients farmers as a whole in each field is 2-3 tablespoons (20 ml) for 16 liters of water in one spray tank, where spraying is done 2 or 3 times a week.This depends on the resistance of the pests attacking the plants.The higher the pest attack, the higher the dose of pesticide given and the more frequent the spraying.Based on the results of pesticide residue analysis conducted at the Food Laboratory in each slope, it was found that there were pesticide residues in the Insecticide group.On the slope of 0-8% to 25-45% each location has different types of residues including cypermethrin, phentoat, profenofos, diazinon, and permethrin.The highest type of Insecticide residue was found on a 0-8% slope compared to other slopes, but when compared to the forest that location is already contaminated by cypermethrin, phentoat, and permethrin Insecticides.The residue difference value of cypermethrin between points 1 and 2 was 0.08 mg kg -1 , while the residue difference value of phentoat between points 1 and 2 was 0.003 mg kg -1 , and the residue difference value of permethrin between points 1 and 2 was 0.01 mg kg -1 .In each slope, it can be seen that each location has different active ingredient results and some are not even detected, where the flat slope of 0-8% has a higher residue content than the rather steep slope of 25-45%.This is influenced by crop factors, spraying intensity, pesticide application on the land, and surface flow (runoff).Plant factors greatly affect residue content, where different types of plants will have different residue content on each land [17][18].The difference can be seen in terms of maintenance, fertilizer, and pesticide application by farmers.The intensity of spraying and applying pesticides also affects residue content, especially from the wrong way of spraying and excessive dosing by farmers.The more doses given, the more residue left behind [19][20].The analysis of Insecticide residues in forests on slopes of 25-45% shows that forests on slopes of 25-45% do not find insecticide residues in each location.This is because the forest is not applied to pesticides by farmers.Forest conditions at 25-45% slope are rather steep at each point (Fig. 4A).The vegetation that grows is wild grass, shrubs, and large trees, this causes the forest to be beautiful and natural so that it has quite a lot of organic matter content.Analysis of the active ingredients found were 3 types, namely cypermethrin, phentoat, and permethrin with different residue content values at each location.The highest value of sipermetrin was found in location 1 at 0.581 mg kg -1 , while in location 3 the residual sipermetrin content was not detected.This is because the residual value of cypermethrin at location 3 is too low so it is not read on the tool, where the lower limit value on the tool is 0.005 mg kg -1 .The highest phentoat value was found at location 1 at 0.031 mg kg -1 , and the highest permethrin value was also found at location 1 at 0.119 mg kg -1 , while diazinon and profenofos were not found (Fig. 4B).Factors that cause the loss of insecticide residues in the soil so that the residue content is not detected and not found, one of which is the influence of the adsorption ability of pesticides by organic matter and soil clay, where the percentage of soil organic matter on slopes 0-8% is 2.494% while soil clay is 7.24%.Farmers usually tend to fertilize and apply pesticides to the top soil layer, this is because the top soil layer contains a lot of organic matter.The high and low content of soil organic matter affects the dynamics of pesticide persistence in the environment [21].Therefore, the higher the content of soil organic matter, the mobility of pesticides decreases.The 8-15% slope, has the same result as the 0-8% slope.There are 3 types of active ingredients, namely cypermethrin, phentoat, and permethrin, but the content value of each location is different and some are not even detected.The value of cypermethrin in each location was not detected.For phentoat values were detected only in location 6 at 0.023 mg kg -1 , while locations 4 and 5 were not detected.For permethrin values, all were detected at each location with the highest value at location 4 of 0.199 mg kg - 1 and diazinon and prefonofos were not found (Fig. 4C).This is caused by evaporation, where most of the pesticides applied by farmers will decrease in number because they evaporate from the surface of the plant due to high temperatures so that pesticides that have evaporated will be in the air in the form of dust and the residual content can be lost, where the nature of the pesticide itself is volatile [22].There were 3 active ingredients found, namely cypermethrin, diazinon, and permethrin, but the content value of each location is different and some are not even detected.The value of cypermethrin at each location was not detected, it was because the value of cypermethrin was too low and did not reach the lower limit of 0.005 mg kg -1 so it was not read on the tool.For diazinon values, all were detected in each location with the highest value found in location 9 at 0.157 mg kg -1 , while for permethrin the highest value was in location 7 at 0.138 mg kg -1 , while phentoat and prefonofos were not found (Fig. 4D).This is because the research location farmers did not apply pesticides with the active ingredients phentoat and prefonofos so they were not found.One of the factors that caused cypermethrin not to be detected was spraying on rainy days.The pesticide that had been sprayed would later be carried away by rainwater so that the residue content was lost in the soil.Pesticides given on high slopes would be carried away by rainwater to gentle slopes so that residue buildup occurred.High rainfall will cause the life of pesticides to be short, the speed of metabolism is higher and leaching becomes faster.Surface residues left on crops and soil when sprayed can be lost due to leaching [23][24].
In Figure 4E, it can be seen that there are 3 types of active ingredients found, namely permethrin, phentoat, and prefonofos with different residue content values at each location.The highest permethrin value was found in location 10 at 0.131 mg kg -1 , while the phentoat value in each location was the same at 0.057 mg kg -1 .The highest prefonofos value was found at location 12 at 0.162 mg kg -1 , while at location 10 the prefonofos residue value was not detected.The factor that causes prefenofos not detected at location 10 is that the pesticide applied at location 10 has been washed by rainwater so that the residue content is lost and carried to a flat slope.In addition, soil samples were taken 6 days after farmers sprayed pesticides, a few days before taking soil samples, the weather conditions at the research site were often rainy, causing pesticides to be lost due to leaching by rainwater.Insecticides diazinon and cypermethrin were not found because farmers did not apply these types of pesticides in the area.

Conclusion
Insecticide residues on Inceptisol in the central of horticultural production, Banuhampu Agam West Sumatra, identified as many as 5  Cypermethrin was the most highly contaminated insecticide residue found in soil at 0.1 mg kg -1 and is a pyrethroid insecticide.The effect of slope level was not significant on the identification of the number of active ingredients and total insecticide residue concentration.However, the highest number of active ingredients on 0-8% and 25-45% slope each amounted to 3 units, while the highest total concentration of insecticide residues on 0-8% slope amounted to 0.499 mg kg -1 .

Figure 1 .
Map of administration (A), soil type (B), land use, and (C) and slope (D) in the center of horticultural production, Banuhampu Agam West Sumatra.

Figure 2 .
Map of ground surface temperature (A) and rainfall (B) of Inceptisol in The Central of Horticultural Production, Banuhampu Agam West Sumatra.
Remaks : R = Replication; ni = not identified and nm = not measurable