Organic farming is gaining worldwide acceptance, and has been expanding at an annual rate of 20% in the last decade, accounting for over 32.2 million hectares worldwide. The influence of organic and conventional management practices on exogenous amino and peptide utilization by soil microbial populations in horticultural production soils is scarcely.
Therefore, soils from an accredited organic farm (OS), transitional farm (TS), and neighboring conventionally managed farm (CS) were sampled from agricultural areas in Shanghai, China, and the amino acid and peptide behavior of top soils were evaluated by 14C labeled techniques. We found that organic management resulted in significant increases (P <0.05) in amino acid and peptide rate acquisition, possibly due to higher SOC and soil respiration in OS, compared to TS and CS (Fig. 1). The relative amino acid and peptide-C amounts partitioned into respiration (15–32% of total) versus biomass production (68–85% of total C) was also affected by management strategy, and generally followed the order CS > TS > OS; OS was significantly different from TS and CS, however a significant difference was not detected between TS and CS (Fig. 1). We hypothesize that amino acid and peptide mineralization acts as a purely biological process, as CHCl3 fumigation and autoclaving resulted in no observable mineralization. Amino acids and peptides were only weakly sorbed onto the soil solid phase, however our results suggested that this did not limit soil bioavailability.
The results of our study indicated that soil management regimes have a substantial effect on amino acid and peptide behavior (mineralization, microbial uptake, and sorption, among other attributes) in horticultural production systems. Therefore, we propose that SOC and total microbial activity are likely key determinants governing amino acid and peptide behavior in horticultural soils. Additional studies investigating the long-term functional significance of DON under different soil management regimes, particularly in organic practices are therefore warranted.
This research was financially supported by funds from the Chinese Academy of Sciences (KZCX2-YW-437, KZCX2-YW-T07), the National Natural Science Foundation of China (40971180, 40801098) and the UK Natural Environment Research Council.
The study entitled “Amino acid and peptide dynamics in horticultural soils under conventional and organic management strategies” has been published in Volume 12, Issue 3, pp 323-333, March 2012 of Journal of Soils and Sediments, details could be found at http://link.springer.com/article/10.1007/s11368-011-0457-x#