Carbon Management (Jan 2021)

Decomposition of soil organic matter is modulated by soil amendments

  • Anjum,
  • Ahmad Khan

DOI
https://doi.org/10.1080/17583004.2020.1865038
Journal volume & issue
Vol. 12, no. 1
pp. 37 – 50

Abstract

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Increasing soil microbial respiration is thought to increase the soil organic matter (SOM) decomposition and hence the soil fertility. It was hypothesized that whether N or C rich drivers enhance the SOM decomposition if amended with farmyard manure (FYM). Thus, an experiment was designed using four key drivers i.e. 1) Control (No-amendment), 2) Min-N (urea @ 30 kg N ha−1 as N rich amendment), 3) HA (Humic acid @ of 2.5 kg ha−1 as C rich amendment) and 4) EM (effective microbes @ 200 L Mg−1 FYM as microbial solution). These four key drivers were mixed with different levels of FYM i.e. (0, 5, 10, 15 and 20 Mg ha−1) and were added to 100 g soil in vials. These vials were incubated for 90 days at 25 °C and destructive periodic sampling were made after 1, 3, 15, 30, 45 and 90 days. The mineral N availability was 3 times higher with 20 Mg FYM ha−1 than No-FYM treatment. The degrading order of soil organic carbon (EM > HA > Min-N > control) resulted in soil respiration of the same order. However, the degrading order of TN (EM > Min-N > HA > control) caused positive changes for mineral N availability with EM (31.3‰ day−1) and negative changes with Min-N (257‰ day−1). The mineral N availability last for 45 days with EM and 30 days for HA. According to principle component analysis, EM increased MBC, mineral N, soil respiration and has positive effects for PC-1 (63%) whereas Min-N increased the SOC and TN and has negative effects both for PC1 (63%) and PC-2 (22%). In conclusion, the SOM decomposition increased by Min-N (23%), EM (42%), HA (32%) with increasing FYM level from 0 Mg ha−1 to 5, 10, and 15 Mg ha−1, respectively. Thus, for C rich driver more FYM should be used than N rich driver for higher SOM decomposition.Highlights The effect of C and N rich amendment on SOM decomposition was studied. No direct addition of C and N drivers on SOM decomposition is yet documented. Increasing manure increased SOM decomposition and hence the soil respiration and mineral N. The increased decomposition of SOM needs more FYM with C rich than N rich driver.

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