Abstract:

Dairy farming waste as an organic fertilizer has become a popular trend of dairy farming waste returning to field in China, but it may cause environmental pollution of farmland soil and surrounding groundwater due to its characteristics of a large amount of nitrogen nutrients. In this paper, the field management of 11 types of base fertilizer + topdressing models of large-scale dairy farming waste returning to field was used to study the law of nitrogen transport in farmland soil and soil aqueous solution. The results showed that the average content of total nitrogen in the soil of different depths under field management showed a gradually decreasing trend as the depth increased; the amount of nitrogen applied was significantly and positively correlated with the average content of nitrate nitrogen in the soil of different depths; nitrate nitrogen was the main form of nitrogen in the soil aqueous solution. Fertilization was the main source of farmland nitrogen input, and leaching was the main item of farmland nitrogen output; only relying on biological nitrogen fixation and atmospheric deposition as the source of nitrogen input would cause soil nitrogen depletion. Base fertilizer of 100% liquid fertilizer + topdressing of 100% liquid fertilizer (Q100100) field management was most likely to cause excess nitrogen in the soil; solid fertilizer and 50% liquid fertilizer as base fertilizer+ topdressing of 75% liquid fertilizer (SQ5075) was most prone to nitrogen leaching. Solid fertilizer and 75% liquid fertilizer as base fertilizer + topdressing of 75% liquid fertilizer (SQ7575) had the least loss of nitrogen from leaching, and was more conducive to plant growth and the accumulation of nitrogen in soil.

Key words: dairy farming waste returning to field, field management, fertilization, total nitrogen, nitrate nitrogen, ammonium nitrogen