Effects of soil and water conservation technologies on the establishment, growth and survival of three tree species

The agroforestry activity of central Chile is developed under Mediterranean climate, characterized by long periods of water deficit conditions, particularly on hillsides with degraded and compacted soils. The objective of this study was to assess the effect of two soil and water conservation techniques on soil water content (SWC) and in plant growth and survival of three tree species. The conservation techniques evaluated were subsoiling with contour ridges (SB) and infiltration trench (IT), and a control treatment without soil management (CO). Growth and survival of Cytisus proliferus L. f. var. proliferus, Quercus suber L. and Quillaja saponaria Molina were examined. The experimental area was sown with a mixture of annual legumes. Conservation systems allowed higher SWC especially in years of higher rainfall (2008 and 2009) at 20-40 and 40-60 cm depth. SWC was higher in SB followed by IT and CO, whereas at 60-80 and 80-100 cm depth differences were significant only in the driest years. After 4 yr, plant survival of C. problems and Q. suber was similar in the three establishment systems (97% and 87%, respectively), but survival of Q. saponaria was lower in CO. Plant height in C. proliferus was higher in IT > SB > CO, while Q. suber was higher in SB > IT > CO; Q. saponaria had similar growth in SB and IT conservation systems but it was significantly higher (P< 0.05) than in CO. It is concluded that subsoiling with ridges has a great potential for degraded and compact soils of the Mediterranean region, allowing higher SWC in the profile and better tree establishment and growth.