Long-term fertilization and PFM changed the accumulation of stalk-derived POM in soil aggregates under field conditions

<p>Plastic film mulching (PFM) is critical for agricultural planting and production in semi-arid and arid areas. Particulate organic matter (POM) is assumed to be a sensitive indicator of evaluating the effects of different agricultural practices on soil fertility and soil organic carbon (SOC) pool. Soil aggregates are the main storage sites for POM. However, there is limited information regarding how PFM and fertilization influences the dynamic changes of newly added stalk-derived POM in Brown earth. Consequently, a depth-study of the fate of carbon (C) and nitrogen (N) derived from maize stalk residues as the POC and PON fractions in soil aggregates will help in predicting the active organic matter component sequestration in the soil. The dynamics and contribution of the newly added maize stalk C and N as POC and PON in different soil aggregates (using dry sieving method divided to > 2, 1-2, 0.25-1and < 0.25 mm) was analyzed by an <em>in-situ</em> ¹³C¹⁵N-tracing technique under 27-year long term PFM and different fertilization treatments. Over the 360 d cultivation, the POC and PON contents were significantly (P < 0.05) higher in the nitrogen (N) and organic manure (M) treatments than other fertilizer addition treatments. Compared with no PFM, PFM accelerated the decomposition of maize stalk C in the N fertilizer treatment, exhibiting an increase of 64% in stalk-derived POC in the initial cultivation time. In addition, stalk-derived POC tended to accumulate in 1-2 mm aggregates in the summer and fall as a result of long-term PFM coupled with fertilization. However, the stalk-derived PON was decreased with the cultivation time in different four aggregates. Stalk-derived POM was tended to accumulate in the macroaggregate size fraction (> 0.25 mm) over 360 days of cultivation in the field conditions. Accordingly, PFM application and fertilization practices had important effects on accumulation of newly added stalk-derived POM in soil aggregates.</p>