Long-Term Effects Of Tillage, Nutrient Application And Crop Rotation On Soil Organic Matter Quality Assessed By Nmr Spectroscopy

Abstract

Crop and land management practices affect both the quality and quantity of soil organic matter (SOM) and hence are driving forces for soil organic carbon (SOC) sequestration. The objective of this study was to assess the long￢ﾀﾐterm effects of tillage, fertilizer application and crop rotation onSOCin an agricultural area of southern Norway, where a soil fertility and crop rotation experiment was initiated in 1953 and a second experiment on tillage practices was initiated in 1983. The first experiment comprised 6￢ﾀﾐyr crop rotations with cereals only and 2￢ﾀﾐyr cereal and 4￢ﾀﾐyr grass rotations with recommended (base) and more than the recommended (above base) fertilizer application rates; the second experiment dealt with autumn￢ﾀﾐploughed (conventional￢ﾀﾐtill) plots and direct￢ﾀﾐdrilled plots (no￢ﾀﾐtill). Soil samples at 0￢ﾀﾓ10 and 10￢ﾀﾓ30ￂﾠcm depths were collected in autumn 2009 and analysed for their C and N contents. The quality ofSOMin the top layer was determined by13C solid￢ﾀﾐstateNMRspectroscopy. TheSOCstock did not differ significantly because of rotation or fertilizer application types, even after 56ￂﾠyr. However, the no￢ﾀﾐtill system showed a significantly higherSOCstock than the conventional￢ﾀﾐtill system at the 0￢ﾀﾓ10ￂﾠcm depth after the 26ￂﾠyr of experiment, but it was not significantly different at the 10￢ﾀﾓ30ￂﾠcm depth. In terms of quality,SOMwas found to differ by tillage type, rate of fertilizer application and crop rotation. The no￢ﾀﾐtill system showed an abundance of O￢ﾀﾐalkyl C, while conventional￢ﾀﾐtill system indicated an apparently indirect enrichment in alkyl C, suggesting a more advanced stage ofSOMdecomposition. The long￢ﾀﾐterm quantitative and qualitative effects onSOMsuggest that adopting a no￢ﾀﾐtillage system and including grass in crop rotation and farmyard manure in fertilizer application may contribute to preserve soil fertility and mitigate climate change.