Biomass decomposition and phosphorus release from residues of cover crops under no-tillage. Accepted in Agronomy Journal.

VARELA MF; BARRACO M; GILI, A; TABOADA, MA; RUBIO, G

AGRONOMY JOURNAL

AMER SOC AGRONOMY

Año: 2017 vol. 109 p. 317 - 326

0002-1962

Under no-tillage fieldconditions, cover crop (CC) residues remain on the soil surface and decomposeat a slow rate.   We used three CC species (oat, Avena sativa L.; rye, Secale cereale L. and ryegrass, Lolium multiflorum L.) to evaluate the residuebiomass decomposition and phosphorus (P) pools release -total P (Pt), inorganicP (Pi) and organic P (Po)- under no-tillage field conditions.  The dynamics of biomass and P in CC residueswas evaluated through the litterbag method during two annual periods in a longterm field experiment. Exponential decay models were fitted to eachvariable.  Biomass decomposition and Prelease followed asymptotic decay models for the less labile residues (oat andrye) and single exponential decay models for the more labile ryegrass residues.Biomass and Pt showed rather equivalent dynamics, but Pi release was faster (Pirates were 3 times higher and Pi plateaus were 2-4 times lower than biomassvalues). The release of Pt from CC residues reached agronomically significantquantities (5-16 kgha-1) during the cash crop growing season and most of this Pt wasreleased as Pi (53-100%). A positive tradeoff was observed between the releaseof Pi, potentially available for subsequent crop, and the residue biomassremaining over the soil in no-tillage field conditions. This means that Pi wasreleased from residues, but enough biomass remained on the soil surface forerosion control. These results can be incorporated into predictive models onthe contribution of CC residues to soil coverage and P nutrition of subsequentcrops.