Guan'gai paishui xuebao (May 2022)
The Effects of Straw Incorporation Depth on Nitrogen Dynamics and Enzymatic Activities in Soil
Abstract
【Objective】 It has been a consensus that adding organic matter such as crop straws to soil not only improves soil fertility and soil structure but also boosts enzymatic activity and nutrient cycling. However, what is the optimal way of amending soil with straws is poorly understood. The purpose of this paper is to fill this knowledge gap by systematically studying the effects of incorporating straws into different soil depths on nitrogen mineralization and enzymatic activity at different growth stages of tomato. 【Method】 The plot experiment was conducted in a tomato field, with the straw incorporated over the soil surface, at the depth 20 cm and 30 cm, respectively. For each straw incorporation, there were three irrigation treatments - irrigating 80%, 100% and 120% of water measured from an evaporation pan, and three nitrogen fertilizations: 180 kg/hm2, 225 kg/hm2, 270 kg/hm2. During the experiment, we measured the content of NH4+-N and NO3--N, as well as the activities of urease, sucrase and catalase in the soil at different growing stages. 【Result】 The contents of NH4+-N and NO3--N in the upper soil decreased with time (P0.05). Nitrogen fertilization and straw incorporation depth combined to affect the contents of ammonium and nitrate in the upper soil (P<0.05), with high nitrogen application combined with straw burial depth of 20 cm increased the contents of ammonium and nitrate nitrogen in the upper soil most (P<0.05). Irrigation amount affected the contents of NH4+-N and NO3--N in the lower soil (P<0.05), and increasing irrigation amount benefited the downward movement of NH4+-N and NO3--N. The buried depth of straw had significant effects on the activity of urease, sucrase and catalase in both upper and lower soil (P<0.05), and the burial depth of 20 cm improved the activities of urease, sucrase and catalase significantly, compared to other treatments. 【Conclusion】 Straw burial depth, irrigation and nitrogen fertilization combined to affect the dynamics of soil water and nutrient, as well as enzymatic activity. Considering mineral nitrogen, enzymatic activity, crop growth and water saving, burying the straw at the depth of 20 cm, combined with irrigating 80% of water measured from a pan and nitrogen application of 270 kg/hm2 was the optimal agronomic practice for tomato production in the studied area.
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