The feasibility of lightweight construction materials by incorporating a waste that is difficult to recycle, based on waste from intensive agriculture: vegetable fibers and propylene, is presented. This innovative material consists of a mixture of Alhambra Formation soil (Granada, SE of Spain) reinforced with vegetable fibres from tomato, pepper, zucchini, cucumber, aubergine and polypropylene fibres. The fibres were used in the mixture at a ratio of 2.5%, 5.0%, 7.5% and 10.0%. These values were then compared with control test samples that did not contain any residues. The compatibility of the fibres with the soil of the Alhambra Formation was then evaluated in terms of its physical-mechanical properties, specifically in relation to uniaxial compression and longitudinal deformation. Due to the highly hygroscopic nature of plant fibres, their absorption was measured and the techniques of presoaking and non-soaking the fibres before mixing them with the soil of the Alhambra Formation were investigated. The results of the unconfined compression tests show that the increase in fibre volume leads to a significant decrease in compressive strength. The highest compressive strength from a residue ratio >= 7.5 % was achieved with the cucumber residue and the non-pre-soaking technique. This residue ratio reached an average value of 1.82 MPa, which is 4% lower than the reference specimen without additives. Notwithstanding the decline in mechanical strength with elevated residue quantities, the resulting Alhambra Formation soil composite blended with a 7.5 % cucumber ratio may be regarded as a prospective candidate for implementation using the Projected Earth System technique.