Hedgerow Olive Orchards versus Traditional Olive Orchards: Impact on Selected Soil Chemical Properties

Olive orchards cover over 10 million hectares worldwide, with production techniques undergoing significant changes in the past three decades. The traditional rainfed approach, involving minimal inputs, has given way to irrigated super-intensive systems with higher planting density, increased productivity, a greater use of fertilizers and phytopharmaceuticals, and total mechanization. Its impact on soil chemical properties remains a topic of great debate, and no definitive consensus has been reached. Our main objective was to examine the different effects of traditional olive orchards and super-intensive orchards on soil chemistry over a decade. We collected and analyzed 1500 soil samples from an irrigation perimeter in southern Portugal in 2003 and 2013. Our findings indicate that, compared to traditional olive orchards, super-intensive ones show, in a decade, a significant decrease in soil organic matter (less 22.8%— p < 0.001), namely due to the increase in mineralization caused by an increase in soil moisture content as a result of irrigation practice, and an increase in sodization (more 33.8% of Ext Na— p < 0.001) highlighting the importance of monitoring this factor for soil fertility. In comparison to other irrigated crops in the region, super-intensive olive orchards promote a significant soil acidification (from 7.12 to 6.58), whereas the pH values of the other crops increase significantly (3.3%, 13.5%, and 3.0% more in corn, tomato, and cereals, respectively). Mainly because of the decrease in organic matter levels with soil acidification and soil sodization, we can underline that hedgerow olive orchards can affect soil characteristics negatively when compared with traditional ones, and it is necessary to adopt urgent measures to counter this fact, namely sustainable agriculture practices.