Spontaneous Vegetation as an Alternative to Cover Crops in Olive Orchards Reduces Water Erosion and Improves Soil Physical Properties Under Tropical Conditions

This research aimed to study the effects of different cover crops on chemical and physical properties in olive orchards, under tropical conditions, to investigate erosive processes by measuring soil and water losses, and to determine the best management cover crop in olive orchards. We assessed soil and water losses under different cover management practices: olive planted on bare soil (OBS); intercropped olive with spontaneous vegetation (OSV); intercropped olive with jack beans (OJB); intercropped olive with millet (OMI); intercropped olive with sunn hemp (OSH), and bare soil (BS). The experiment was carried out for two hydrological years (2015/2016 and 2016/2017) in the Southern region of Minas Gerais, Brazil. Experimental setup consisted of fifteen standard plots (12 m x 4 m), in a Cambisol, with slope of 0.23 m m-1. In both rainy seasons, treatments with cover crops showed significant efficiency to reduce soil loss. OSV treatment showed good performance in the reduction of water erosion, revealing lower values of total soil loss of 25 Mg ha-1 period-1 and 0.55 Mg ha-1 period-1 in first and second season, respectively. Based on the results, it is recommended to use spontaneous vegetation as a cover crop in olive plantations at least during the first season. This proved to be able to reduce soil and water losses. For subsequent years, a combination or a transition of other cover crops is possible, since soil losses for treatments OJB (0.41 Mg ha-1 period-1), and OSV (0.55 Mg ha-1 period-1) were statistically grouped using a non-metric multidimensional scaling with a good performance (final stress = 0.069). This decision between spontaneous vegetation or a profitable cover crop should be adopted by farmers considering technical and financial aspects.