Management residues of chlorpyrifos insecticides on shallot cropping through remediations technology

Chlorpyrifos is a broad-spectrum insecticide and is widely used to Organism Pests Management (OPM). The remediation technology for polluted land is needed to reduce the risk of continuous impacts. The research aimed to reduce chlorpyrifos insecticide residues in shallot agriculture through remediation technology. The research was carried out in Naru Village, Sape Sub-District, Bima Regency (NTB) in June-August 2018. The experiment was designed in a randomized block design (RBD), three replications, and six treatments: (T1) farmers method, (T2) urea fertilizer-coated biochar, (T3) urea fertilizer-coated biochar enriched with consortia microbes, (T4) consortium microbes 2 L ha−1, (T5) urea fertilizer-coated nano biochar, and (T6) urea fertilizer-coated nano biochar enriched with consortia microbes. Remediation agents containing carbon, such as biochar and manure and some microbes can help accelerate the degradation of insecticides in the environment. Decreased chlorpyrifos residue from highest to low, respectively: urea fertilizer coated nano biochar>urea fertilizer coated nano biochar with enriched consortium microbes>urea fertilizer coated biochar>urea fertilizer coated biochar with enriched consortium microbes>consortium microbes 2 L ha−1. Treatment of urea fertilizer coated nano biochar and urea fertilizer coated nano biochar with enriched consortium microbes can be applied as a chlorpyrifos remediation technology in the shallot agriculture in silt texture soils.


Introduction
In modern agriculture, the intensive and excessive agrochemicals will increase their accumulation in soils, so land remediation should be mandatory as part of land management. The management of crop cultivation, especially vegetable crops, is almost impossible without using chemical insecticides. The use of insecticides caused unsanitary soil indicating to levelling off, symptoms of decreased yield, and increased attack by plant pests.
This condition needs to find a mitigation solution from the further impact of chemical insecticide residues through land remediation. Land remediation is an effective method because it can accelerate the degradation process of insecticide residues in the soils [1][2][3][4]. Meanwhile, the need for shallots as a kitchen spice and medicines continues to increase, causing the use of inorganic inputs to increase at the field level. Shallots are capital-intensive and solid tech, therefore the sligh test disturbance to the plants will be responded to by farmers protectively. This demand then forces farmers to use insecticides above the average needs of other crops. Attack of plant pests organisms at each stage of shallot planted growth has an important significance for the success harvesting. Silkworm (Agrotis ipsilon) and Armyworms (Spodoptera litura) are pests that are greatly feared for the successful harvest of shallots [5]. The caterpillar attack on shallot crops could be causing total crop failure. Chlorpyrifos is one of the famous insecticides in controlling the worm attack on shallot crops. Chlorpyrifos is one of the wide-spectrum of organophosphate insecticides group that is most widely used in the agricultural sector [6,7] and be used in 90 countries around the world [8,9]. In the environment chlorpyrifos has a half-life between 10 to 120 days [10], even in humid soil, the degradation can reach 251 days [11]. Chlorpyrifos (C9H11Cl3NO3PS) is used worldwide to control a variety of chewers and suckers pests [7]. Chlorpyrifos is widely used to control pests in shallot agriculture, and is one of the five active ingredients selected by farmers [5,12]. Chlorpyrifos has neurotoxic and immunotoxin properties and has proven to be harmful to animals, humans, and the environment. Overuse causing to reduced microbial populations (bacteria and fungi), and can inhibit nitrogen mineralization in the soil.
All applied chemical materials to soil agriculture will become pollutants in the soil and the environment. The chemical metabolite of chlorpyrifos could soluble by naturally water entry soil particles [13]. According to Akbar and Sultan [14], the detections of chlorpyrifos residue requires the seriousness of all parties.
To decrease the risk of further chlorpyrifos residues in the soils, mitigations efforts needed, i.e. through remediation technology. Remediation is a way to reduces chemical pollutions in soil agriculture, so that is created environmentally friendly agriculture. This study aims to obtain remediations technology to reduce chlorpyrifos insecticide residue in shallot agriculture.

Research implementation
As a basis for determining the needs for urea fertilizer, the doses of urea fertilization used by local farmers which is 400 kg ha -1 [15]. Urea fertilizer-coated biochar is made with a ratio of 80:20, while urea fertilizer-coated nano biochar is made with a ratio of 90:10 (m m -1 ) with adhesive of molasses dose 4 L every 100 kg of finished fertilizer-coated. The microbial consortia used include Bacillus aryabhattai, Bacillus thuringiensis, Bacillus subtilis, Bacillus cereus, Achromobacter sp., Catenococcus thiocycli, Stenotrophomonas maltophilia. The application times of fertilizer for the plants were 10, 20, 30, and 40 days after planting (DAP), as well as with SP36 and KCl fertilizers. During the experimental progress, pest control was remained to be done with chemical insecticides with active ingredients of nonchlorpyrifos.
Seedbeds the experimental are made with a width of 1.5 m and a length of 6 m. Between seedbeds are made galleries with a width of 0.2 m to reduce water runoff to other plots. In the middle of the seedbed, a small, 0.25 m created trench is made which services as a walkway for people to doing watering time. The shallot of Philippine variety is planted with a distance of 20 x 10 cm, one tuber/planting hole, and are located on the left and right of the seedbeds.
For analysis of chlorpyrifos residue, soil sample was taken diagonally randomly on each plot [16]. Soil samples were taken at a depth of 0 to 20 cm using soil auger. Chlorpyrifos residues analysis was carried out at the Integrated Laboratory of the Indonesian Agricultural Environment Research Institute, by using the QuEChERS method [17]. Meanwhile, to calculating the residual amount of chlorpyrifos using a formula [18] as follows:

Soils properties of the research location
The soil characteristics of the research location presented in table 1. The soil texture is dominated by silt, with pH of 5.6 (slightly acidic), low C-organic (1.45%), high cation exchange capacity (CEC) (37.84 cmol kg -1 ), very high P-available (209.54 mg 100 g -1 ), and low K-available (21.10 mg 100 g -1 ). The soil type in the research location was Inceptisols [19]. Endoaquepts is a developing soil that comes from clay sediment materials, has a slightly light color (yellowish), chroma 2, value 3, and usually has quite a lot of brown spots. Generally, have reactions a slightly acidic (pH 5.5 to 6.0), with medium-high organic matter content, medium alkaline saturations, medium cation exchange capacity, and lower aluminum saturations [21].

Chlorpyrifos residue in the soil
The residual content of chlorpyrifos insecticide in the soil before applying treatment ranged from 0.0173 to 0.2483 mg kg -1 . The residues of chlorpyrifos insecticides at 1 day after application of treatment ranges from 0.0121 to 0.1288 mg kg -1 , increasing at 7 Day After Treatment Application (DATA) to ranges from 0.0240 to 0.0383 mg kg -1 , and decline at harvesting times (ranges of 0, 0165 to 0.0828 mg kg -1 ). The residual values of chlorpyrifos in various treatments and various observation times are presented in figure 1. Degradations of chlorpyrifos insecticide residues depending on environmental conditions [2]. Degradations of chlorpyrifos in dry soil is more quickly about 1.6 days because chlorpyrifos degradation  [11]. Moist soil conditions due to watering the crops on this experiment are thought to slow down the process degradation of insecticide residues. From the regression above, it can be seen that the treatment of farmers method and urea, fertilizercoated biochar enriched with consortium microbes reached the maximum remediation after 1-week treatment application. Meanwhile, the treatment of urea fertilizer-coated biochar, consortium microbes 2 L ha -1 ), urea fertilizer coated nano biochar, and urea fertilizer coated nano biochar with enriched consortium microbes, the maximum remediation was achieved before 1 week after the treatment application. Carbonated matter [22][23][24][25] and several microbes [24][25][26][27] can help accelerate the degradation of insecticides in the environment.
Insecticides contain positively charged functional groups and increase soil adsorption capacity. In certain conditions, the functional groups of insecticides are adsorbed on the clay surface and soil organic matter [28]. Both of them have a role together or individually in adsorbancy insecticide groups. The lower soil organic matter content of 1.45% at the research locations, causes the pesticide groups to be strongly bound by clay minerals, and causes the residues to remain firmly bound until harvesting times. The accumulations of insecticides in the soil are influenced by the type and nature of the soils, clay type, and soil organic matter content [29]. The residual chlorpyrifos can be decreased due to the result of the degradation process be harmless materials [3,24,30] and become 3,5,6-trichloro-2-pyridinyl (TCP) through the hydrolysis process [31,32]. TCP is more dangerous to the environment than chlorpyrifos compound.  The reductions in chlorpyrifos residue at harvesting time is presented in Table 2. The farmer practices could decrease the chlorpyrifos residue by 21.5% compared to the initial concentration. All treatments can increase the degradations of chlorpyrifos insecticide residues in the soil after the end of the shallot growth period. The number of reductions in chlorpyrifos insecticide residues in each treatment was from the highest respectively is urea fertilizer coated biochar with enriched consortium microbes (74.9%), urea fertilizer coated nano biochar with enriched consortium microbes (67.1%), urea fertilizer coated biochar (57.2%), urea fertilizer coated nano biochar (29.4%), and microbes consortium 2 L ha -1 (26.5%).  The chlorpyrifos residue between harvesting time and the before treatment application showed a decrease. The treatment based on microbial consortia (both biochar and nano biochar) showed a higher percentage of reduction. Some insecticides trigger the growth of soil microorganisms and partly bad influence [33,34]. Organisms have a strategic and important role in degrading insecticide residues in the soil [35,36]. The activity of several organisms in soils contaminated with chlorpyrifos residue is an important indicator of the degradation process [37].
The nanobiochar material was effective in lower chlorpyrifos residue in this study. The nanomaterials are reported to be able to accelerate the degradation rate of pesticide residues in soil and water environments [38]. The small size of the nanomaterial increases the surface area thereby increasing the chemical activity and adsorption ability of the nanoparticles in adsorbing pollutants on each surface [39].

Conclusions
The decreasing of chlorpyrifos residue from each treatment is as follows: urea fertilizer coated nano biochar>urea fertilizer coated nano biochar with enriched consortium microbes>urea fertilizer coated biochar>urea fertilizer coated biochar with enriched consortium microbes>consortium microbes 2 L ha -1 . Treatment of urea fertilizer coated nano biochar and urea fertilizer coated nano biochar with enriched consortium microbes can be applied as a chlorpyrifos remediation technology in the shallot agriculture in silt texture soils.