The olive tree is one of the most important crops in Spain, and the main one in the region of Andalusia. Most orchards are rain-fed, with high slopes where conventional tillage (CT) is the primary soil management system used. These conditions lead to high erosion and a significant transport of organic carbon (OC). Moreover, soil tillage accelerates the oxidation of the OC. Cover crops (CC) are the conservation agriculture (CA) approach for woody crops. They are grown in-between tree rows to protect the soil against water erosion and their organic residues also help to increase the soil carbon (C) sink. Soil and OC losses associated to the sediment were measured over four seasons (2003-07) using micro-plots for the collection of runoff and sediment in five experimental fields located in rain-fed olive orchards in Andalusia. Two soil management systems were followed, CC and CT. Furthermore, the changes in soil C in both systems were analyzed at a depth of 0-25 cm. CC reduced erosion by 80.5%, and also OC transport by 67.7%. In addition, Cover crops increased soil C sink by 12.3 Mg ha-1 year-1 of carbon dioxide (CO2) equivalent, with respect to CT. CC in rainfed olive orchards in a Mediterranean climate could be an environmental friendly and profitable system for reducing erosion and increasing the soil C sink. However, C fixing rate is not regular, being very high for the initial years after shifting from CT to CC and gradually decreasing over time.

This study provides a bibliometric analysis of global scientific production on Conservation Agriculture (CA) and its relationship with climate change mitigation. Using data from the Scopus and Web of Science databases, the research encompassed 650 articles published between 1995 and 2022. The analysis revealed significant growth in the number of publications over the past three decades, driven by increasing global interest in sustainable agricultural practices. The findings highlight key themes, including no-tillage, soil organic carbon, and greenhouse gas emissions. Collaboration networks were mapped, identifying major contributors, such as the USA, Brazil, and China, alongside thematic clusters emphasizing carbon sequestration and soil management. Results indicate that CA research is increasingly focused on its potential to mitigate climate change, particularly through practices like no-tillage, vegetative cover, and crop rotation. While carbon sequestration has been central to CA research, recent studies have expanded to include nitrous oxide and methane emissions, indicating a broadening conceptual framework. This analysis underscores the importance of CA in addressing climate challenges and offers insights into emerging research areas, such as regional adaptations and the long-term effects of no-till systems. The findings aim to guide future research and policy development in sustainable agriculture and climate mitigation.

Residue chopping from orchard pruning is becoming a common practice in conservation agriculture after the establishment of eco-conditionality policies in the European Union. This type of residue is used to protect the soil from erosion and improve the water balance and fertility of soils by improving the organic matter content. However, no studies have evaluated the influence of pruning residues and size on soil coverage. This study examines the effect of different treatments on pruning residue soil coverage in an olive orchard (cv. Picual). Treatments consisted of two quantities of pruning residues, specifically, high (2.04 kg m-2) and low (1.02 kg m-2), and two chopping speeds, low (2.4 km h-1) and high (3.2 km h-1). The different treatments were evaluated by image analysis and pixel counting to determine the soil cover percentage, size, number and distribution of the pruning residues after chopping. After chopping, the soil cover percentage was 39% higher in the high quantity pruning residue treatments but was not significantly influenced by the chopping speed. The size and number of lignified residues was quantified via pixel counting. In the high quantity pruning residue treatments, the number of large lignified residues (> 6 cm2) was higher, and the number of pruning residues smaller than 2 cm2 was lower, when compared with low quantity pruning residue treatments. The high chopping speed treatments produced more smaller-sized pruning residues.

Optimizing resources to produce higher quality food is key to promoting more resilient agroecosystems. Although the use of biostimulants in agriculture has been gaining importance in recent years, their success depends on edaphoclimatic conditions and on the specific plant species. For this reason, the main aim of this study was to evaluate the effect of biostimulants (amino acids obtained from the enzymatic hydrolysis of plant extracts) on durum wheat yield variables and grain quality (protein content). Five treatments (control treatment—T1, biostimulants—T2, slow-release urea—T3, biostimulants plus slow-release urea—T4, Mg and micronutrients—T5) were tested in a field experiment conducted over 3 seasons in the south of Spain; all were dosed at 120 kg N ha⁻¹. The number of spikes increased significantly with biostimulant treatments in the first season (up to 33%, T2 and T4), while the highest significant grain yields were obtained with biostimulants applied individually in the first season (29.5%-T2) and biostimulants in combination with slow-release urea the second season (27.3%-T4), related to T1. Grain protein concentration was influenced by the treatment only in the second season, the driest during the study, when it was increased with biostimulants up to 4.2% with T2 in comparison with T1. Total protein production increased (28.1%T2) in the first season, (8.1–21.9% for T2–T4) in the second season and (6.5% T4) in the third season, when biostimulants were applied alone or in combination with slow-release urea, respectively. In general, plants treated with Mg and micronutrients produced a lower number of spikes, less yield, and reduced total protein compared to those doses with biostimulants. The application of amino acids as biostimulants was demonstrated to enhance durum wheat yield and total protein production and could be a potential tool for promoting nitrogen use efficiency in semi-arid areas.