Long-term Additions of Organic Amendments in a Loire Valley Vineyard. I. Effects on Properties of a Calcareous Sandy Soil

Abstract

A long-term experiment (28 years) was conducted to study the effects of various organic amendments on physical, chemical, and biological properties of a sandy vineyard soil. Annual applications of either crushed pruned vine-wood (2 t/ha fresh wt), cattle manure (10 and 20 t/ha fresh wt), or spent mushroom compost (8 and 16 t/ha fresh wt) were compared to an unamended treatment. In plots unamended for 28 years, total organic C (TOC) showed a slow and limited decrease (19%). For the highest rates of exogenous organic amendments, the increase in TOC reached a saturation value after 20 years and carbon (C) sequestered after 28 years reached 30 Mg/ha. Final predicted TOC obtained by simulation with the AMG model was lower than measured TOC for all treatments. Soil microbial biomass C was very low in unamended plots 24 years after the beginning of the experiment. Fair (and comparable) levels of microbial biomass were observed for moderate amounts (2 t/ ha/yr) of crushed pruned vine-wood and for single rates of cattle manure and spent mushroom compost, while these levels were high for double doses of organic amendments. As a consequence of TOC increase in topsoil, soil water-holding capacity was improved and bulk density was reduced. Soil P and K concentrations were also increased by exogenous organic amendments. For high rates of organic inputs, mineralized N largely exceeded the vine requirements, with an important risk of N leaching. Preservation or improvement of soil organic matter content and soil properties is possible without harmful side effects through the use of an organic material low in nutrients such as crushed pruned vine-wood.