Liquid Smoke-Based Biostimulant (Foliar Fertilizer) for Application to Palm Oil Plantations Using Drones

In palm oil plantations, fertilizer is the highest cost component of their operations. Therefore, various efforts are made to optimize fertilization to ensure its maximum efficiency, including the use of slow-release fertilizers. For more details, read here. To maximize fertilization and maximize fresh fruit bunch (FFB) yields, the use of foliar fertilizers is also worth considering. Liquid smoke (pyroligneous acid) is one such foliar fertilizer, although a more accurate term is biostimulant (booster).

This is because liquid smoke does not provide nutrients such as nitrogen (N), phosphorus (P), and potassium (K). However, liquid smoke acts as a biostimulant, plant growth regulator (PGR), and natural protectant, promoting optimal leaf growth. Optimal leaf growth exponentially increases the growth of all plant organs, including stems, roots, flowers, fruit, and so on. Leaves are the primary "kitchen" of a plant, so leaf health determines the health of the entire plant system. Optimal leaf growth also increases the efficiency of fertilizer absorption (a "pump engine" effect) in the soil.

Furthermore, liquid smoke is not only used as "leaf fertilizer", it turns out that liquid smoke also functions as an organic pesticide (fungicide/insecticide). This repels pests (such as ticks and flies), and prevents leaf diseases. The phenol and acetic acid content is toxic to insects (aphids, thrips, caterpillars) and is effective in suppressing fungi that cause plant diseases. And the distinctive smell of smoke makes insects reluctant to approach and lay their eggs on the surface of the leaves. In addition, its binding properties make it difficult for pathogenic fungal spores to attach and develop on the surface of the leaves

Regarding this dual function, the use of liquid smoke for application to leaves (foliar) can be prioritized, whether it is more specifically used as a "foliar fertilizer" or as a biopesticide. This requires a number of adjustments such as dosage, additional formulations and application time. To maximize the function of liquid smoke as a leaf fertilizer, you must mix it with additional nutrients (such as liquid organic fertilizer / LOF) and apply it when the leaf stomata are fully open. Liquid smoke is able to reduce water molecules. When diluted or mixed with Liquid Organic Fertilizer (LOF), the nutritional content of the fertilizer becomes easier to enter and be absorbed through the stomata (leaf mouth). Meanwhile, to maximize its function as a biopesticide, liquid smoke needs to be combined with other vegetable pesticides. The frequency of spraying for prevention is once a week, while pest attacks are high, namely 2-3 times a week until the pest population is under control.

The use of drones for spraying pesticides and liquid fertilizer has been widely used on various agricultural crops such as rice, corn, sugar cane and palm oil. More specifically in palm oil plantations, drone applications are a modern solution for spraying fertilizers and pesticides. And in Indonesia more than 80% of drone applications are for the forestry and agricultural sectors. Efficiency factors (time, energy, operational costs, fertilizers, pesticides) and precision are the main driving forces for this drone application. This means that drone technology is expected to be an effective solution in controlling pests and diseases, fertilizing and cultivating palm oil plants. Drones are effective in increasing plantation efficiency, especially in areas that are difficult to reach. As a technology, various improvements have been made to improve its functions such as carrying capacity, spray speed, safety features and work efficiency. The use of drones supports precision agriculture and global food security with an environmentally friendly technological approach.

Spraying liquid fertilizer on the underside of leaves (underside spraying) using a drone requires special techniques. This is because drone propellers naturally produce strong downwash. This downwash effect is used to gently move and turn the leaves, so that the droplets can hit the bottom of the leaves. This is because on the bottom of the leaf, where the stomata are located the most are gathered around 80%. The spray texture is also made into mist mode (the finest dew) so that the liquid sticks evenly and doesn't drip onto the ground. Next, the drone's height, speed and nozzle angle need to be adjusted in such a way to achieve this goal. Environmental factors in the form of strong winds need to be avoided so it is necessary to adjust the right time and conditions.

As the use of biochar grows as a solution for health and soil fertility as well as a climate solution, this should also be the case with the application of liquid smoke. Liquid smoke as a by-product in the form of a liquid product from biochar production will increase along with increasing biochar production. Liquid smoke as a product produced from biomass raw materials through a pyrolysis process also encourages the use of natural materials based on renewable resources so that it is environmentally friendly and sustainable. 

Production of LOF and EFB Pellets at The Same Time

The leaching process for palm oil empty fruit bunches (EFB) so that it has potassium and chlorine content suitable for EFB pelletproduction on a commercial scale that can be used maximally on a pulverized combustion (PC) boiler at a power plant is not easy and inexpensive. That is because the leaching process requires a solvent to extract the potassium and chlorine content from the EFB material. Ideally the leaching process is carried out with acid solvents, agitation and heat and a long time so the extraction process can run optimally. In fact this is the bottle neck to carry out the leaching process, so that almost no one has done this process commercially today. It is different if the leaching process also has other objectives that also have commercial value, for example for the production of liquid organic fertilizer (LOF).

By simultaneously producing LOF, the costs for leaching can be compensated with the benefits of the LOF. In CPO business operations, especially in palm oil plantations the cost of fertilizer is one of the highest cost components, estimated at 35.75 billion rupiahs (around 2.5 million USD) per year for every 10,000 hectares. If the cost of the fertilizer can be saved from the use of self-produced LOF as well as pellet EFB production, then this is one of the optimization of biomass utilization in the palm oil industry. LOF will have the main content in the form of potassium because the potassium content is quite high at EFB about 30% of the ash produced is potassium. Potassium fertilizer is very beneficial for plants because it is an essential nutrient with benefits including transporting sugar, controlling stomata in leaves by maintaining electro-neutrality in plant cells, co-factor of more than 40 enzymes and reducing the occurrence of various diseases. Some plantations also need large amounts of potassium fertilizer, for example banana plantations. The process of making LOF by soaking EFB for several days is expected to significantly reduce the potassium and chlorine content in EFB and make it a material for pellets that are friendly to the PC boiler power plant.

The EFB pellets produced can then be sold for export as well as meeting domestic needs. With EFB pellet production as well as LOF, it is hoped that export bioenergy will not damage or reduce the fertility of the existing soil, something that is sometimes indeed dilemmatic. In addition, other materials in the plantation such as leaves and frond can still be composted if they are also intended as fertilizer. EFB pellet production also always requires energy in the form of electricity for its plant operations. And for that electricity can be produced from biogas by treating the palm oil mill effluent (POME), for more details, read here. The location of palm oil mills which are generally remote are required to be able to produce their own electricity, including if they are going to process EFB into LOF and EFB pellets, the electricity needs should also be fulfilled by themselves.

EFB pellets without leaching process actually can also be used for FBC (fluidized bed combustion) boiler technology and for a limited number percentage of PC boilers. With this leaching process EFB pellets can be used optimally on the PC boiler. Majority of power plants or coal power plants currently use PC boiler technology. So that if the EFB pellet produced can be friendly with a PC boiler the market is more open automatically. Production of EFB pellets which are agricultural waste pellets will usually be the second priority after the production of wood pellets is constrained mainly in terms of the availability and supply of raw materials.