Policies can help to apply successful strategies to control soil and water losses. The case of chipped pruned branches (CPB) in Mediterranean citrus plantations

Abstract

[EN] There is a need to devise management strategies that control soil and water losses in agriculture land to allow the design of proper policies to achieve sustainability. It is the responsibility of scientists to work with other actors to co-construct strategies that will lead to sustainable land-use policies. Using chipped pruned branches (CPB) as mulch can be a viable option because they represent local (in situ) organic material that can restore soil nutrient and organic matter. This research assesses: i) the perception of farmers towards different types of management strategies and CPB's costs; ii) the biomass yield of citrus branches and the impact of CPB on soil properties; iii) how CPB affects soil erosion and runoff generation in citrus plantations; and, iv) a discussion about how to favour the use of CPB thought successful policies. To achieve those goals we carried out: i) one-hundred it interviews to assess the perception of farmers and twelve interviews to assess the economic balance of twelve land owners; ii) soil was sampled at 0-2 and 4-6 cm depths; iii) pruned material was surveyed for 40 trees; and iv) forty rainfall simulation experiments (55 mm h(-1)) were carried out in two citrus plantations at paired sites (Control versus CPB), in La Costera District in Eastern Spain. Forty circular (0.25 m(2)) plots were installed in focus rows (4 x 5 = 20 plots) in control (CON) and CPB plots (20 + 20 = 40 plots) to perform the rainfall simulation over one hour. The cost of chipping ranged from 102 to 253 epsilon ha(-1), and was related to the size of the farm. soil quality, runoff and erosion assessment showed that CPB is a suitable strategy. CPB increased organic matter from 1.3% to 2.9% after 10 years in the 0-2 cm depth layer, while the 4-6 cm layer was largely not affected (OM moved from 1.1 to 1.3% after 10 years), and soil bulk density showed a similar trend: a decrease from 1.36 to 1.16 g cm(-3) in the surface layer with no change in the subsurface layer. The hydrological and erosional responses were different between CON and CPB. The CON plots initiated ponding (40 s) and runoff (107 s) earlier than the CPB plots (169 and 254 s, respectively); and runoff discharge was 60% in CON vs 43% in CPB plots Sediment concentration was four times larger in the CON plots than in the CPB (11.3 g l(-1) vs 3 g l(-1)), and soli erosion was 3.8 Mg ha(-1) h(-1) vs 0.7 Mg ha(-1) h(-1). CPB mulches were effective at controlling soil and water losses in Mediterranean citrus plantations as they showed the relationship between vegetation/litter cover and soli erosion rates. However, the farmer's perception survey showed that the use of CPB was not welcomed nor accepted by the farmers. Policies that aim to promote CPB as soil conservation mulch need to by promoted subsidies as the farmers requested, and by education to demonstrate the positive effects of CPB to of the farming community.