Analysis of Common Misconceptions in Fertilizer Application for Greenhouse Vegetables
When applying inorganic fertilizers to greenhouse vegetables, the following misconceptions often exist, which not only reduce fertilizer efficiency but also bring some negative effects, and deserve attention.
1. Applying ammonium bicarbonate and ammonium sulfate inside the greenhouse in winter. After application, ammonium bicarbonate volatilizes a large amount of ammonia gas, which is harmful to vegetable growth; ammonium sulfate is a physiologically acidic fertilizer, and its application increases soil acidity. When applying ammonium bicarbonate, deep application should be noted. Generally, a 10 cm deep trench is opened 8-10 cm away from the vegetable roots and stems, and after broadcasting, it should be covered tightly with soil, which can increase the utilization rate by 10%-30%.
2. Applying too much diammonium phosphate in winter. Vegetables need large amounts of nitrogen and potassium, and relatively little phosphorus. For example, the ratio of nitrogen, phosphorus, and potassium required by eggplant is 3:1:4, cucumber is 3:1:10, tomato is 6:1:12, etc. Diammonium phosphate contains 18% nitrogen and 46% phosphorus, and no potassium, so it is not suitable to apply too much diammonium phosphate to greenhouse vegetables. In addition, note that diammonium phosphate must not be mixed with alkaline fertilizers such as plant ash, to avoid causing ammonia volatilization and ammonia damage.
3. Topdressing potassium fertilizer at the late growth stage. Vegetables generally need more potassium before and after flowering, and then gradually less. Applying potassium fertilizer at the late stage will significantly reduce the utilization rate of potassium and waste fertilizer.
4. Fertilizing under drought conditions. Vegetables like water. Fertilizing when the soil is dry not only prevents fertilizer efficiency from being fully exerted, but also causes the soil solution concentration to rise sharply, which easily burns vegetable roots. Therefore, fertilization in greenhouses should be combined with irrigation. Trenches should be opened for fertilization, the fertilizer should be buried firmly, and then irrigation should be carried out, or the fertilizer can be washed on with the water.
5. Applying iron-containing fertilizer into the soil. Iron is easily fixed by the soil and converted into insoluble compounds, which cannot be absorbed and utilized by vegetables. Therefore, when applying iron fertilizer in greenhouses, foliar spraying is best. A 0.1%-0.3% ferrous sulfate solution can be evenly sprayed on the vegetable leaves.
Xinji Agricultural Technology Center, Zhang Yun