Effect of Continuous Agriculture of Grassland Soils of the Argentine Rolling Pampa on Soil Organic Carbon and Nitrogen

Luis A Milesi Delaye,Adrián E Andriulo,Bruno Mary,Alicia B Irizar

doi:10.1155/2013/487865

Abstract

Long-term soil organic carbon (SOC) and soil organic nitrogen (SON) following cultivation of grassland soils (100/120-year tillage (T) + 20/30-year no tillage (NT)) of the Rolling Pampa were studied calibrating the simple AMG model coupled with the natural13C abundance measurements issued from long-term experiments and validating it on a data set obtained by a farmer survey and by long-term NT experiments. The multisite survey and NT trials permitted coverage of the history of the 140 years with agriculture. The decrease in SOC and SON storage that occurred during the first twenty years by a loss through biological activity was 27% for SOC and 32% for SON. The calibrated model described the SOC storage evolution very well and permitted an accurate simultaneous estimation of their three parameters. The validated model simulated well SOC and SON evolution. Overall, the results analyzed separately for the T and NT period indicated that the active pool has a rapid turnover (MRT ~9 and 13 years, resp.) which represents 50% of SOC in the native prairie soil and 20% of SOC at equilibrium after NT period. NT implementation on soils with the highest soil organic matter reserves will continue to decrease (17%) for three decades later under current annual addition.

Highlights

It is well established that grassland soils, Mollisols, originally rich in soil organic matter (SOM), rapidly lose important quantities of carbon (C) and nitrogen (N) after cultivation [1,2,3,4,5,6,7,8,9,10]
Long-term soil organic carbon (SOC) and soil organic nitrogen (SON) following cultivation of grassland soils (100/120-year tillage (T) + 20/30-year no tillage (NT)) of the Rolling Pampa were studied calibrating the simple AMG model coupled with the natural 13C abundance measurements issued from long-term experiments and validating it on a data set obtained by a farmer survey and by long-term NT experiments
The results indicate that the NT implementation in the rich SOM soils of the Rolling Pampa after a century of continuous agriculture contributed to a decrease in the SOM mineralization rate, the system implies a low humification from harvest crop residues addition

Summary

Introduction

It is well established that grassland soils, Mollisols, originally rich in soil organic matter (SOM), rapidly lose important quantities of carbon (C) and nitrogen (N) after cultivation [1,2,3,4,5,6,7,8,9,10]. Since the 1970s, largely due to economic reasons, there has been an important increase in the area under arable crops, with the cropped area increasing relative to the pasture area at an annual rate of 4% [14]. This resulted in an increase in tillage intensities

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Conclusion