Farmer Rafael Alonso Aguilera in his organic olive grove, with drip irrigation and cover crop SICS. Photo credit: Jasmine Black


In our second newsletter (November 2017), we introduced you to the two Spanish study sites, located in the South-East of Spain near Almeria – Area A in the Sorbas-Tabernas Basin and Area B in the Cabo de Gata Natural Park. Recently the SoilCare research team met in Almeria to discuss project progress and visit the two study sites 


Getting stuck in - discussing the soil at the nectarine plantation.  Photo credit: Jane MillsArea A - Sorbas-Tabernas Basin 

Study Site leader Julián Cuevas introduced us to his research team and the farmer heading this trial. We were given a great overview into the uniqueness of Tabernas desert, the influence of the surrounding mountains for water and the calcareous, weak structured soil prone to erosion. We also learned about the evolving history of agriculture here – from livestock grazing to orange, almond and olive plantations – the result of a changing and expanding global market. Orange and lemon plantations still very much exist here, however, they are in decline due to strong competition from cheaper oranges from developing countries with lower production costs that has caused a price crisis in the last few years. The area of almonds grown in this region is expanding due to heavy demand from China and other countries. The variety grown here are more suited to this climate, are rain-fed and are lower yielding but higher quality than those grown in California. 

Farmer Rafael Alonso Aguilera from the family-run Oro del Desierto organic olive farm and processing unit talked with us about his passion behind the business and practice, as well as the progress to date with his trial. As a family farm that has won several awards for their cold-pressed extra virgin olive oil and who work hard to be a part of both the local and global market, it was great to see them actively leading soil health research in the desert.  


 Farm background 

High quality organic olive oil has been produced on the farm since 1995. The olive variety grown is the ‘Picual’, maintained and harvested with machinery. The plantation is low density (7 x 7 m spacing of trees) due to the scarce availability of water. The flowering and fruit set in mid-May, therefore controlling irrigation and the status of the plants' water at this time of year is crucial. The focus of the business is to produce high quality rather than volume. The family sell oil to over 30 countries, bottling 90% of their production. There are very few pests and diseases due to the hot summers, cold winters and low humidity. 

Here, organic is a practical choice since the market provides a more stable income than conventional due to the certification process and consistency in quality. Alternate bearing of olives causes high fluctuations in yields and consequently in price. This uncertainty in price can be difficult for farmers to manage. High olive oil quality has low acidity and is the farmers production target. This may depend on management, weather variation and resulting chemical use to control pest and disease. Overall organic is currently less than 5% of Spanish produce, although Integrated Pest Management (IPM) and reducing pesticides is gaining popularity. 


 Woodchip, olive and food waste compost overlying drip irrigation channels and cover crops.  Photo credit: Jasmine BlackSoil-improving Cropping System (SICS) 

The SICS experiment is on land rented by the family on a 10-year tenure, of which they are just 3 years in to. The owners converted the olives to organic 8 years ago, but they have been growing on the site for 30 years. Prior to this, it was used to graze livestock, which eventually became an unprofitable business. It is cheap to rent and as the family already have a near-by processing plant and established customer base it was an easy win to expand onto this grove. Their decision to test the SICS on this site was because they thought that they may see a bigger difference compared to the groves that they had been managing for a longer period.  

The SICS that the family are testing are the additions of woodchip to the alleys with the new drip-feed irrigation pipes (8 l /hour) in the olive groves. This SICS has replaced the traditional method of burning or removal of the pruned material and flooding irrigation. Compost is also added and is home-made from waste olive paste after processing for oil, chicken and sheep manure, straw and iron. This is used after 1-2 years of maturing. The removal of woodchip is also expensive, so this has provided cost savings as well as organic matter to the soil.  

The cover crops grown have so far been spontaneous – too many would cause water competition to the trees. They are either mown or grazed during the spring and summer. The family have now agreed to trial incorporating a mix of legumes and grasses in order to increase nitrogen in the soil and improve rain infiltration. Existing stones are left on the soil surface which helps protect against erosion, whilst in conventional systems these are removed.They are hoping that the cover crops will also help to reduce soil erosion.


Initial observations 

The family and researchers have already seen a big difference in the soil organic matter and structure after just a few years of woodchip and compost applications. The drip-irrigation has also reduced evaporation and saves 30% of the previous water use, whilst allowing the minerals to be taken up by the trees more slowly.  


Area B - Cabo de Gata Natural Park 

Next, we headed to our Spanish partner’s second study site, nearer to the coast with a greater wind speed which can erode the similarly weak-structured calcareous regosols. An average of 4 t / ha of soil can be lost every year to both wind and rain erosion, so the challenge here is similar – trying to increase organic matter in the soil. 

This plantation of stone fruit – La Joya – is owned by the company Grupo el Ciruelo. 


Company background 

Grupo el Ciruelo owns several plantations around the south east of Spain and grows a range of fruit including grapes, nectarines, plum, apricots, oranges and lemons amongst some others. La Joya is an estate of 180 ha, although they also run sites up to around 400 ha. The company employs some permanent technical staff and, in the picking and pruning season, around 300 migrant workers who work between the different crops. They work to use Integrated Farm Management and are certified under Standard IFS, Standard BRC, GlobalGap, Tesco Nurture, M&S Field to Fork, LEAF Marque, Integrated Production and Sedex. These work to ensure good social and environmental standards are met. 


Part of the nectarine plantation and SICS trials on reduced irrigation. Photo credit: Jane Mills

Soil-improving Cropping System (SICS) 

The SICS being carried out on this study site include trialling deficit irrigation against regular irrigation methods and growing cover crops. The company and researchers hope to reduce the water quantity and cost as well as increasing soil moisture, soil organic matter and biodiversity from these changes. 


Initial observations 

The cover crops were unfortunately eaten by a local population of rabbits leaving little behind. Despite this, they are keen to try harder in the following year and will monitor progress and are considering ways to biologically control the rabbit population.  

The group began monitoring soil moisture and CO2 emission levels from the soil between standard and deficit irrigation in February 2019. Initial early data from just one month of measurements are hinting that soil moisture may be higher in the deficit irrigation sites, whilst CO2 emissions may be higher in the regular irrigation. There are many more months of monitoring to be undertaken before this can be verified.