No-till (NT) adoption is an essential tool for development of sustainable agricultural systems, and how NT affects the soil organic C (SOC) dynamics is a key component of these systems. The effect of a plow tillage (PT) and NT age chronosequence on SOC concentration and interactions with soil fertility were assessed in a variable charge Oxisol, located in the South Center quadrant of Parana´ State, Brazil (50823’W and 24836’S). The chronosequence consisted of the following six sites: (i) native field (NF); (ii)
PT of the native field (PNF-1) involving conversion of natural vegetation to cropland; (iii) NT for 10 years (NT-10); (iv) NT for 20 years (NT-20); (v) NT for 22 years (NT-22); and (vi) conventional tillage for 22 years (CT-22) involving PT with one disking after summer harvest and one after winter harvest to 20 cm depth plus two harrow disking. Soil samples were collected from five depths (0–2.5; 2.5–5; 5–10; 10–20; and 20–40 cm) and SOC, pH (in H2O and KCl), DpH, potential acidity, exchangeable bases, and cation
exchangeable capacity (CEC) were measured. An increase in SOC concentration positively affected the pH, the negative charge and the CEC and negatively impacted potential acidity. Regression analyses indicated a close relationship between the SOC concentration and other parameters measured in this study. The regression fitted between SOC concentration and CEC showed a close relationship. There was an increase in negative charge and CEC with increase in SOC concentration: CEC increased by
0.37 cmolc kg1 for every g of C kg1 soil. The ratio of ECEC:SOC was 0.23 cmolc kg1 for NF and increased to 0.49 cmolc kg1 for NT-22. The rates of P and K for 0–10 cm depth increased by 9.66 kg ha1 yr1 and 17.93 kg ha1 yr1 , respectively, with NF as a base line. The data presented support the conclusion that long-term NT is a useful strategy for improving fertility of soils with variable charge.
Joa˜o Carlos de Moraes Sa´ Universidade Estadual de Ponta Grossa, Av. Carlos Cavalcanti 4748, Campus de Uvaranas, 84030-900 Ponta Grossa-PR, Brazil
Carlos Clemente Cerri Universidade de Sa˜o Paulo-Centro de Energia Nuclear na Agricultura, Av. Centena´rio 303, 13416-970 Piracicaba-SP, Brazil
Rattan Lal The Ohio State University, School of Environment and Natural Resources, 2021 Coffey Rd., Columbus, OH 43210, USA
“Warren A. Dick ” The Ohio State University, School of Environment and
Natural Resources, 2021 Coffey Rd., Columbus, OH 43210, USA
Marisa de Cassia Piccolo Universidade de Sa˜o Paulo-Centro de Energia Nuclear na Agricultura, Av. Centena´rio 303, 13416-970 Piracicaba-SP, Brazil
Brigitte Eduardo Feigl Universidade de Sa˜o Paulo-Centro de Energia Nuclear na Agricultura, Av. Centena´rio 303, 13416-970 Piracicaba-SP, Brazil
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