Abstract

PINEDA-PINEDA, Joel et al. Pine sawdust as hydroponic substrate. I: Variation in physical properties during five crop cycles. Rev. Chapingo Ser.Hortic [online]. 2012, vol.18, n.1, pp.95-111. ISSN 2007-4034.

In agriculture under controlled environment, soil has been replace by substrates due to physical, chemical and biological limitations. The use of materials coming from agro industrial wastes or byproducts facilitate the use of low cost substrates and enable a positive ecological impact, which is the case of the forest industry that produce a large volume of pine sawdust with potential as a substrate. Physical properties of the substrates are the most important, because once the crop has been settled, it can hardly be modified and it must remain constant throughout crop cycle. The objective of this work was to evaluate the variation in physical properties of the substrate formed by a sawdust/volcanic rock mixture during several crop cycles to determine the feasibility of their use. For this purpose, 10 treatments were used, which consisted of the combination of three volcanic rock particle sizes (<3, 3-6 and 6-12 mm) and three sawdust/volcanic rock ratios (90/10, 80/20 and 70/30) plus a treatment 100 % pine sawdust. These treatments were tested during five continuous tomato crop cycles (thirty months). Total porosity, particle size, moisture retention capacity, air capacity and bulk density were measured at the end of each cycle and also from the original substrate. Little variation in bulk density was observed, but total porosity, moisture retention capacity and air capacity decreased gradually during the five tomato crop cycles. Air capacity was the physical characteristic that showed greater variation, showing values below the appropriate after 24 months of cultivation.

Keywords : Porosity; moisture; aeration; bulk density.

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