Corn straw return effectively improves the stability and increases the carbon and nitrogen contents of waterstable aggregates in northeastern China black soil

Abstract

In view of the current situation of black soil degradation, straw return as an important conservation tillage measure has been extensively promoted. Based on 15 N tracing technology, this paper carried out experiments of different straw returning modes, including CK (conventional fertilizing tillage with straw-free returning), straw mulching (i.e., M), straw mixed with topsoil (i.e., T), and straw deep incorporation (i.e., D), to explore the influence of straw returning on the distribution and stability, and the carbon and nitrogen content of water-stable aggregates in black soil, and to analyze the distribution and stability of aggregates on the carbon and nitrogen content of aggregates. The results showed that the macroaggregate content, mean weight diameter (MWD) and geometric mean diameter (GMD) of the returned soil layers were 16.53-84.65%, 16.73-128.73% and 23.47-97.14% higher than those in CK, respectively. The contents of organic carbon, total nitrogen and 15 N accumulation of aggregates in the straw-returning soil layer were 6. 38-23.55%, 8.65-31.19% and 13.52-150.19% higher than those in CK, respectively. Pearson correlation analysis and redundancy analysis showed that the content of macroaggregates and stability of aggregates were positively correlated with the carbon and nitrogen contents. In conclusion, straw return significantly improved soil structure characteristics and carbon and nitrogen content. The results of this study provided a theoretical basis and technical guidance for farmland soil improvement in black soil areas, and selected an appropriate straw returning mode according to local soil conditions to maximize the effect of straw returning.

Long-term in situ straw returning increased soil aggregation and aggregate associated organic carbon fractions in a paddy soil

“…Our findings revealed that macro-aggregates (> 2 mm) were dominant in all soil layers. In accordance, a significant increase of approximately ∼11 % appeared in the contents of soil macro-aggregates via straw returning coupled with the conventional (SF) and or 80 % conventional fertilization (SDF) compared with the F treatment [ 29 ]. This is consistent with the results of Zhao et al [ 21 ], suggesting a higher structural/aggregate stability in the study straw amended soils [ 13 ].…”

“…It is also worth noting that in situ straw returning provides fresh organic substrate for soil microorganisms [ 34 ]. This can improve the microbial decomposition of soil organic matter, that in turn accompanies by large productions of polysaccharide metabolites and humic substances [ 14 , 29 ]. The latter contribute to the formation of larger and more stable aggregates [ 35 ].…”

“…This might attribute to the shallow straw incorporation (5–10 cm) and less plant root residues/development in the deeper soil layers, particularly within 30–50 cm. In addition, higher contents of organic C in top soil layers might attribute to the higher activity of soil microorganisms, that in turn contribute to the straw decomposition and C cycle [ 29 , 34 ]. Higher accumulation of organic C fractions in the upper SF and SDF soil layers might also attribute to their higher crop yield, with larger production of root exudates [ 39 , 40 ].…”