Compost amendment effects on grapevine root density and distribution

In this study we investigated the effects of different types and application methods of compost on grapevine root density and distribution in a commercial vineyard located in the AOC Piave area, northeastern Italy. Effects on vine vegetative growth and crop production were also evaluated. The study was conducted from 2009 to 2013 in a 6-year-old vineyard planted with 'Cabernet Sauvignon' and grafted onto 3309 C rootstock. Four treatments were compared: inter-row application of compost from cattle manure; inter-row application of compost from crushed pruned vinewood; under vine-row application of compost from crushed pruned vine-wood; control with no amendments. Pruning weight and grape yield were determined over the 5 years of the investigation, as indicators of the aboveground vine growth. The root system was studied at the end of the experiment (March 2014) by using the trench method. Three trenches of 1 m deep each were dug for each treatment at two different distances from the vine row, in order to assess both vertical and horizontal distribution of the root system. Results showed that compost type and application method had a strong influence on root density and distribution. Amendment with compost from crushed pruned vine-wood had a higher stimulative effect on root growth compared to that of compost from cattle manure. Root horizontal and vertical development was greater when compost was applied under the vine-row, and smaller with inter-row application. On the 5-year average, vegetative growth and yield were higher in all the amended treatments than in the control. Results obtained from this study demonstrated that both types of compost could efficiently replace chemical fertilizers in low-impact agricultural systems.