The invention relates to the technical field of agricultural planting, in particular to a fertilizing device for tomato planting and a using method thereof.The fertilizing device comprises a
cart and a mounting flat plate horizontally mounted on the front portion of the
cart, a
fertilizer box and a limiting track are fixedly mounted on the mounting flat plate, and a U-shaped
pipe is arranged at the bottom of the
fertilizer box; an opening in one end, far away from the feeding hole, of the U-shaped
pipe is upwards mounted at the first liquid outlet hole in the limiting rail; the injection
system comprises a material receiving box installed below the second liquid outlet hole, the bottom end of the material receiving box is connected with a material receiving
barrel through an inclined connecting
pipe, a sleeve vertically extending downwards is arranged at the bottom of the material receiving
barrel, an inserting pipe is coaxially installed on the sleeve, a downward pressing
assembly is arranged on the
cart, and the pushing
assembly is provided with a pushing rod. According to the technical scheme, the single-time fertilization amount is accurately controlled through the measuring cylinder, the uniformity of each-time fertilization amount is ensured, and the downward pressing
assembly drives the
insertion pipe to move downwards in the sleeve, so that liquid
fertilizer can be directly applied to the roots of tomato seedlings.