The time required for the seed soaking technique using biogas and biogas slurry

In addition to the three essential nutrients for fertilizers—nitrogen, phosphorus, and potassium—slurry also contains various nutrients and trace elements required for seed germination and growth. At the same time, various active substances secreted by microorganisms while decomposing and fermenting the raw materials have the effect of promoting germination and stimulating growth. Soaking seeds in biogas slurry can increase the seed germination rate, promote seed physiological metabolism, strengthen the seedlings from an early stage, and enhance their resistance to diseases, pests, and adverse conditions, thereby laying the foundation for high yields. This simple and practical technique is gaining increasing popularity among rural biogas users. Now that it is time to prepare seeds for spring planting, I would like to share my humble opinions on using biogas slurry for seed soaking: (1) Seed soaking technique: Before soaking the seeds, they should be exposed to sunlight first; this is done to improve their water absorption capacity. The seeds are turned over and left in the sun for 1–2 days to remove any impurities, thereby ensuring their purity and quality ； Choose woven bags or cloth bags with good water permeability, fill them with seeds, and leave enough space to prevent the seeds from expanding and breaking the bags once they absorb water ； Next, remove as much scum as possible from the discharge area, so that the biogas slurry can be used to soak the seeds. Tie one end of the rope to the mouth of the bag and secure the other end at the edge of the pond, so that the seeds are located in the middle of the biogas slurry. For some seeds with a short soaking time (within 12 hours), it is possible to choose to soak them in a container ； After soaking the seeds in biogas slurry, they should be rinsed clean in plain water, then sown and germinated. Sometimes soaking seeds in biogas slurry can change the color of the seed coat, but it does not affect germination. (II) Precautions 1. Soaking time: The soaking time varies depending on the region, variety, and temperature; however, it should not be too long, as it is best for the seeds to absorb sufficient moisture. It can be determined after conducting some simple comparative tests first. Rice seed soaking: Before soaking, the rice seeds should be exposed to sunlight for 1–2 days. Then, they are placed in nylon woven bags, with 15–20 kilograms of seeds per bag, and submerged in biogas slurry. Conventional rice seeds are mainly soaked once, with a soaking time of about 24 hours ； For hybrid rice, intermittent seed soaking is used; that is, the seeds are soaked in biogas slurry for 8–10 hours, then taken out to air-dry for 6 hours. This process of soaking and drying is repeated three times until the seeds have absorbed enough water. After soaking the seeds, rinse them with clean water 2–3 times, let them dry, and then proceed with germination promotion. Soaking wheat seeds: Soaking wheat seeds in whey slurry is suitable to be used when the soil moisture level is good. The process is carried out the day before sowing; the seeds are soaked for about 12 hours, then washed with clean water and dried before being sown. If sowing is done under drought conditions, there is no need to soak the seeds in biogas slurry. Soaking corn seeds: Soak them for 12–16 hours, rinse with clean water, let them dry, and then they can be sown. Soaking cotton seeds: Coated seeds do not need to be soaked in biogas slurry; uncoated seeds should be soaked for 14–18 hours at a time. When soaking, place a stone inside the seed bag to prevent it from floating. Soaking sweet potato seeds: Place the selected seeds in peat mud, ensuring that the liquid level is about 6 centimeters above the surface of the seeds. After 2 hours, remove the seeds, wash them with clean water, and let them dry. Soaking peanuts: Soak them for 4–6 hours at a time, then wash them with clean water, dry them, and they are ready for sowing. For melons and beans, soak the seeds for 2–4 hours at a time, rinse them with clean water, dry them, and then sow them or start germination. 2. Biogas digesters used for seed soaking with biogas slurry must be those in normal operation for gas production; the biogas slurry from abandoned or faulty digesters cannot be used for seed soaking. 3. Seeds that have been soaked in swamp water should be rinsed thoroughly with clean water before being sown or used for germination and seedling cultivation. 4. Once the seeds have been soaked, the pool cover should be replaced promptly to prevent people and animals from falling into the pool.

Precautions for soaking seeds in biogas slurry: 1. The biogas digester used for soaking seeds in biogas slurry must have been in normal use for at least 1 month. The \"biogas slurry\" in biogas digesters that have not been in use for a long time should not be used for seed soaking to avoid damaging the seeds. 2. The seeds should not be soaked for too long, as this will affect germination. 3. If the concentration of biogas slurry is too high, add 1-3 times the amount of clean water before soaking the seeds. 4. When soaking the seeds, consider the weather conditions; if it is rainy, spread the seeds on a surface to allow them to germinate naturally, which is better for sowing.