Organic fertilizer for controlling soil salinization of coastal saline soil and killing underground insects and preparation method thereof

The invention discloses an organic fertilizer for controlling soil salinization of coastal saline soil and killing underground insects and a preparation method thereof. The organic fertilizer provided by the invention comprises, by weight, 300-500 parts of straw compost, 300-500 parts of humic acid and 100-200 parts of a saline-alkali modifier, wherein the straw compost is composed of tobacco straw, livestock and poultry night soil, high-efficiency composite microbial inoculants and urea; and the saline-alkali modifier is composed of gypsum and an attapulgite powder. The organic fertilizer can be used to raise the fertilizer conservation and water retention capability of soil, prolong fertilizer efficiency and supplement beneficial bacteria in soil. With the application of the organic fertilizer, the harm of underground insects in field can be obviously reduced, underground insects are effectively killed, chemical agent amount is reduced, work and cost are saved, and toxicity and side-effect residual quantity of chemical control is reduced. In addition, after the application of the organic fertilizer, the topsoil of coastal saline soil is loosened, unit weight is decreased and the organic carbon content is increased.