Disentangling the Effects of Conservation Agriculture Practices on Soil Organic Carbon Dynamics during a 3-Years Transition Period.

Disentangling the effects of conservation agriculture practices on soil organic carbon dynamics during a 3-years transition period

 

I. Piccoli^a, P. Carletti^a, F. Chiarini^b, L. Furlan^b, S.Nardi^a, B. Lazzaro^c, L.Sartori^d, A. Berti^a, F. Morari^a

 

^aDAFNAE Dept., University of Padova, Viale Dell’Università 16, 35020 Legnaro (PD), Italy

^bVeneto Agricoltura, Viale dell’Università 14, 35020 Legnaro (PD), Italy

^cRegione del Veneto, Sezione Agroambiente, Settore Politiche Agroambientali, Via Torino 110, Mestre (VE), Italy

^dTESAF Dept., University of Padova, Viale Dell’Università 16, 35020 Legnaro (PD), Italy 

This study evaluates the effect of conservation agriculture practices on soil organic carbon stock and carbon quality (i.e. humic carbon).

Experimental design was established in 2010 in 3 farms in North-Eastern Italy to compare conventional agriculture “CONV” (plowing) versus conservation agriculture “CT” (no-tillage + use of cover crops), after a three-year transition period. In both treatments a four-year crop rotation was adopted (wheat, rapeseed, maize and soybean). 288 soil cores were collected through a hydraulic sampler up to 50 cm depth in 2011 and 2014. Soil Organic Carbon (SOC) was determined at 0-5 cm (L1), 5-30 cm (L2) and 30-50 cm (L3) with elemental analysis (in total 864 samples). The equivalent soil mass (ESM) approach was used for SOC stock determination. Humic carbon and its apparent molecular weight distribution ->100 kDa (high), 100-10 kDa (medium) and <10 kDa (low)- were isolated through gel filtration in 48 samples.

SOC variation from 2011 to 2014 was affected by the treatments only up to 30 cm. In L1, CT increased the SOC of 0.85 t/ha while a decline of 0.23 t/ha was observed in CONV. This was also confirmed in L1+L2 with an increase in CT (0.57 t/ha) and a slightly decrease in CONV (-0.08 t/ha). Considering the entire soil profile (L1+L2+L3) no differences between the two treatments were observed (+0.47 t/ha in average). The quality of SOC was influenced by tillage, CT had higher (62%) fraction of medium molecular weight than CONV (58%), while CONV (32%) had higher fraction of low molecular weight than CT (29%).

Considering the entire 0-50 cm profile, conservation tillage did not increase SOC stock with respect to conventional tillage but caused a different SOC stratification. Conversely, conservation tillage affected the SOC quality causing a shift from labile humic fractions to more stable humic fractions.

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See more from this Division: SSSA Division: Soil and Water Management and Conservation
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