Hydroponic or greenhouse production systems allow daily fertilization of vegetable crops, depending on its life cycle, substrate and available water. Sawdust is currently being used successfully as substrate in crop production and for this reason we evaluate the effect of mixtures (v/v) of volcanic rock with fresh and recycled sawdust in production and nutrient extraction of tomato. A completely randomized design was used with five different treatments, T1: volcanic rock, T2: volcanic rock/recycled sawdust (20/80), T3: volcanic rock/recycled sawdust (30/70), T4: volcanic rock/fresh sawdust (20/80) and T5: volcanic rock/fresh sawdust (30/70). The maximum absorption rate occurred between 60 and 136 days after transplanting (DAT), with a similar pattern in the extraction dynamics, higher than 70 % in all treatments in a decreasing order K > N > Ca > P > Mg. The results indicate that mixtures of volcanic rock/recycled sawdust produce an equal fruit yield and efficiency of nutrient uptake than volcanic rock and mixtures of volcanic rock/fresh sawdust. This indicates that recycling the growing media is a viable alternative and may provide higher yields during several crops cycles if management is appropriate.

....