Effects of Nitrogen Fertilization and Irrigation on Soil Aggregation and Soil Organic Carbon in Winter Wheat Field

Abstract

【Objective】 Aggregation is an important soil health indicator modulating many soil functions including nutrient bioavailability and carbon sequestration. It is affected by a multitude of factors. The purpose of this paper is to study the effect of irrigation and nitrogen fertilization on soil aggregation and soil organic carbon. 【Method】 The experiment was conducted in a winter wheat field. It consisted of two nitrogen applications: 0 (N0) and 180 kg/hm2 (N180), two irrigation treatments: sufficient irrigation (F) and deficit irrigation using 65% of the water in F. In each treatments, we measured water-stable aggregates and soil organic carbon. 【Result】 ①Deficit irrigation coupled with nitrogen fertilization increased water-stable macroaggregates with diameter ≥0.25 mm. Nitrogen fertilization increased organic carbon in the top 0~30 cm soil layer by more than 3.59% when irrigation was the same, while deficit irrigation increased organic carbon in the same soil layer by more than 2.86% when nitrogen fertilization was the same. ②Soil moisture directly affected soil carbon, explaining 83.9% of the change in total organic carbon, while nitrogen indirectly affected soil carbon, explaining 46.89% of change in the total organic carbon. ③The direct impact of water-stable aggregates on soil carbon was negative, while its direct influence was positive. 【Conclusion】 The effect of nitrogen fertilization on soil aggregation was modulated by irrigation. Nitrogen fertilization combined with deficient irrigation boosted carbon accumulation in the topsoil.

Keywords

• soil aggregates
• irrigation
• nitrogen fertilizer
• soil organic carbon