Food security should be addressed in relation to soil sustainability and sustainable land care, and examined within the science framework of Earth's critical zone as an integrated system that includes Earth surface interactions, connected to soil functions, and ecosystem services. There is a great need to develop critical zone mathematical models that will simulate and quantify soil functions and that can be used as management tools to address soil sustainability and land care practices. The integrated critical zone model, 1D-ICZ, couples computational modules for soil organic matter dynamics, soil aggregation and structure dynamics, bioturbation, plant productivity and nutrient uptake, water flow, solute speciation and transport, and mineral weathering kinetics. The 1D-ICZ model, coupled with new pedotransfer functions to predict bulk soil properties, introduces for the first time a model that dynamically links soil structure characteristics and hydraulic soil properties by simulating their changes under varying meteorological conditions and plant growth. Field data from a Mediterranean olive grove at the Koiliaris Critical Zone Observatory (CZO) were used to simulate carbon addition to soil and agricultural management scenarios, in order to illustrate the model's ability to quantify soil management impact on soil functions and biogeochemical transformations and fluxes. The 1D-ICZ model can be used to assess, understand, and quantify the complex interactions between the different processes in the soil-plant-water system and can be applied as a tool to design sustainable agricultural management practices, taking into consideration synergy and trade-offs among soil functions.

The environmental impact of irrigating a maize field with weathered olive mill wastewater (OMW) for 5 years was assessed. The use of the weathered OMW added the following concentrations of nutrients to the field: 11.8t/ha/yr carbon, 1033kg/ha/yr total nitrogen, 23.8kg/ha/yr phosphorous and 4161kg/ha/yr potassium. The maize field received 6 times more nitrogen, 50 times more potassium and 2 times less phosphorous than the recommended fertilization rates. The presence of carbon increased microbial activity for organic nitrogen breakdown and the decomposition rate of organic nitrogen. No significant increase was observed of heavy metal accumulation in the soil. Electrical conductivity in the soil remained below the salinization threshold. No direct exposure values were exceeded. No impact on groundwater quality was observed. Irrigation of crops like maize with weathered OMW could be part of a viable decentralized solution for olive mill wastewater use in areas with low organic matter and high irrigation demand.