Effects of long-term no-tillage with different residue application rates on soil nitrogen cycling

Effects of different tillage management on rhizosphere soil nitrogen mineralization and its extracellular enzyme activity in a double‐cropping rice paddy field of southern China

“…Our results disagree with those of the Huang et al (2018), who found that bulk soil AN, AAN, HUN and TAHN contents at the 0-10-cm soil layer with no-tillage practice were significantly increased, and these acid hydrolysable N contents at 10-30-cm soil layer with mouldboard plough practice were obviously enhanced. However, the results of this study demonstrated that CT and RT treatments significantly increased the fractions of rhizosphere soil acid hydrolysable N contents, SOC, soil organic carbon; ASN, amino sugar nitrogen; AAN, amino acid nitrogen; AN, ammonium nitrogen; HUN, hydrolysable unidentified nitrogen; TAHN, total acid hydrolysable nitrogen compared with NT treatment (Figure 1) because continuous addition of crop residue into the paddy field (N input) with tillage practice more significantly affects the soil N content and soil ecological environment, rice root growth and root exudates compared to the addition of crop residue into paddy field with no-tillage practice, which were similar to previous results (Mulvaney et al, 2010;Wu et al, 2021).…”

“…The PCA of rhizosphere soil properties, enzyme activities, acid Soil organic nitrogen (N) plays an important role in maintaining or increasing soil quality and fertility of the paddy field, and is the main nutrient source for crop growth (Zhou et al, 2018). In the present study, the results showed that rhizosphere TAHN content with all crop residue removed treatment (RTO) was significantly decreased, compared to the application of tillage combined with crop residue incorporation treatments (CT, RT and NT) (Figure 1), because hydrolysable N was more susceptible to mineralization and was usually regarded as an active N pool in the paddy field, and it was the available N source main for crop growth compared with nonhydrolysable N (Wu et al, 2021). On-the-other-hand, the SOC was increased with the addition of crop residue into paddy the field with the tillage condition (Table 1), which was continuously converted into humus with the action of rhizosphere soil microorganism.…”

“…Soil β-glucosidase activity was closely related to energy and carbon (C) of agricultural soil and was usually reconsidered an important indicator for the source of energy and nutrient (Burns et al, 2013). Soil β-glucosaminidase and arylamidase activities had proved that they play an important role in promoting the process of soil N mineralization and thus are usually reconsidered a sensitive index for the extra-cellular enzymatic breakdown of complex organic N compound into amino acid, amide and amino sugar (Wu et al, 2021). Soil L-glutaminase activity was closely related to the production of ammonium (NH 4 + ) from amino acid by the ammonification process (Muruganandam et al, 2009).…”

“…Some results indicated that the hydrolysis of urea, hydroxyurea, dihydroxyurea and semicarbazide into ammonia (NH 3 ) and carbon dioxide (CO 2 ) was mainly controlled by soil urease activity (Fu et al, 2020). The results from previous studies demonstrated that there were interactive effects of tillage and crop residue incorporation management on soil N mineralization enzyme activities, and some results showed that N mineralization enzyme activities at the 0-10-cm soil layer were increased with the application of no-tillage practice combined with crop residue incorporation condition (Muruganandam et al, 2009;Wu et al, 2021), but other results indicated that N mineralization enzyme activities at the 10-30-cm soil layer were enhanced by combining the application of conventional tillage with crop residue incorporation condition (Pandey et al, 2014). Meanwhile, some results proved that there was a close relationship between soil N mineralization enzyme activities (e.g., βglucosidase, β-glucosaminidase, L-glutaminase, arylamidase, urease)…”

Intercropping of Stylosanthes green manure could improve the organic nitrogen fractions in a coconut plantation with acid soil

“…The application rate can affect the content and proportion of the soil No fractions. Wu et al [35] found that compared with CK (no corn residue application), the 33% corn residue application treatment showed a significantly higher concentration of soil hydrolyzable NH 4 + -N, HAAN, and HASN in both the 0-10-and 10-20-cm soil layers, whereas the 67% corn residue application treatment and the 100% corn residue application treatment significantly increased the concentration and proportion of soil HUN but decreased the HAN, HAAN, and HASN proportions in the 10-20 cm soil layer. Huang et al [24] reported that long-term application of Chinese milk vetch as GM with or without chemical fertilizer could increase all soil No fractions including the HAN, HAAN, HASN, HUN, NHN, and even TN.…”