Scientific topdressing methods for three major crops

corn

The fertilizer requirement of corn is 2% of the total fertilizer requirement during the whole growth period , 85% of the earing stage , and 13% of the grain stage . According to the survey, per 100 kilograms of corn grains, for an N 2. 5 kg, phosphorus 0 . 9 kg, potassium 2 . 2 kg, the peak period of corn fertilizer is from jointing to large trumpet period, generally secondary topdressing, the first time at the beginning of jointing, mu chasing urea 10 kg, or ammonium nitrate 15 kg, chasing 7 to 10 days before the tassel The second pass fertilizer, 12 kg of urea per acre or 17 kg of ammonium nitrate , if the soil organic matter content is high, the base fertilizer, the seed fertilizer foot, the corn grows well, the chase can also be used once, the topdressing method combined with the second shovel can also be used The top dressing device, or chasing the pit (埯), but the depth of the top dressing must be more than 10 cm, in order to improve the utilization of fertilizer.

　 Rice

Rice is a fertilizer that requires more nitrogen. Generally, for every 100 kilograms of rice, it needs about 2 kilograms of nitrogen. The absorption of nitrogen is gradually increased from the time of greening, and reaches the peak of fertilizer demand at the peak of the tillering. Quickly increase the effective tillering power, and apply heavy weight fertilizer early to promote tillering. The principle of rice topdressing is to eat less meals, that is, to apply the tiller fertilizer and the ear grain fertilizer. The time for applying the tiller fertilizer is 7 to 10 days after transplanting, and about 230 kilograms of ammonium sulfate per hectare , and 8 10 leaves before heading. At the beginning, the young panicles began to differentiate and began to apply panicle fertilizer. The panicle fertilizer could be applied twice. The first time when the inverted 3 leaves were just exposed, about 60% of the total amount of panicle fertilizer was applied to promote the ear, the branch, and once. The number of spikelets is differentiated, the number of branches is increased, and the number of branches is increased . The second spike is applied at the tip of the flag leaf; the potassium dihydrogen phosphate can be sprayed at the later stage to increase the maturity and 1000-grain weight.

　 Soy

The fertilizer requirement of soybean is 20% of the total amount of fertilizer required for emergence and flowering . 4 %, flowering to the granules accounted for 54 . 6 %, granules to maturity accounted for 25 %. Per 100 kilograms of soybean seeds as required nitrogen 5 kg left and right, phosphorus 1. About 6 kg, potassium 3 . About 7 kg, soybean needs more nitrogen, and its rhizobium can only meet the nitrogen requirement of soybean 1 / 2 ~ 1 / 3 , the key period of soybean nitrogen demand is seedling stage and flowering stage, and the initial flowering stage is followed by nitrogen fertilizer. Reducing the drop of flowers and leaves, the absorption of phosphate fertilizer by soybeans, such as flowering and phosphorus uptake accounted for 15% of the total amount of phosphorus, 60% of the initial flowering to the pods , and 25% of the pods to the drums ; potassium inferior than nitrogen and phosphate, potassium flower emergence to the suction accounted for 32. 2 %, flowering to drums accounted for 61 . 9 %, granules to maturity accounted for 5 . 9 %. Soybean top dressing: First, the rhizosphere top dressing, when the soybean grows weakly, combine the two times to shovel , apply nitrogen fertilizer, apply 45 to 75 kg of urea per hectare , immediately cultivate the soil after topdressing, prevent evaporation, improve utilization, and exert fertilizer efficiency. The second is the top dressing. When the soybean grows weakly in the early stage, 10 kg of urea per hectare is added to the potassium dihydrogen phosphate 1 per hectare . 5 kg, dissolved in 500 kg of water, can also add trace element fertilizer for foliar application.

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