Submitted to: Journal of Residuals Science & Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2009
Publication Date: 1/15/2010
Citation: Khoshgoftarmanesh, A.H., Eshghizadeh, H.R., Chaney, R.L. 2010. Using acid-washed waste tire rubber in soilless media for tomato production. Journal of Plant Nutrition. 7:69-72. Interpretive Summary: Waste tires comprise a disposal problem in many nations. Other researchers tested use of shredded tire rubber in potting media but observed zinc phytotoxicity to several greenhouse crops so this use had not been adopted. We considered that removal of some of the more readily soluble zinc from the tires could alleviate the potential for zinc phytotoxicity even to sensitive crop species such as tomato. Based on earlier tests, strong acid was used to remove over 50% of the rubber zinc (originally 2.5% zinc) before testing both acid-washed and non-washed shredded rubber in hydroponic media for production of tomato fruits. Tomato yield was increased by using the acid-washed rubber in the media compared to the control medium comprised of peat and perlite, while non-acid-washed rubber somewhat reduced yield. Plant zinc, both shoots and fruits, were increased by using the acid-wasted rubber in the media. In this experiment, the nutrient solution contained nitrate-N, which tends to cause nutrient solution pH to rise during growth, while most of the previous literature which observed zinc phytotoxicity when rubber was used in media, used nutrient solutions with ammonium-N which causes solution pH to decline over time which could cause much greater release of zinc from the rubber. Thus, acid-washed shredded waste tire rubber can be safely and effectively used in hydroponic media for crop production when nitrate-N is supplied for growth. Acid-washed tire rubber can replace peat in many media, allowing the rubber to be recycled/reused, and to reduce the non-sustainable use of peat in growing media.
Technical Abstract: 'Cerasiforne’ tomato (Lycopersicon esculentum Mill.) was grown in soilless potting media contained different substrate formulas including 25:25:50 volume ratio of acid-washed (AWR) or non-washed shredded rubber (NAWR): vermiculite or zeolite: perlite. Additionally, plants were grown in a peat: perlite substrate. Plants grown in media containing AWR had greater root and shoot dry weight and fruit production than those grown in the NAWR media or the peat: perlite substrate. Fruit Zn and Fe concentration of plants grown in AWR-containing media was significantly lower than those grown in NAWR-containing media. Plants grown in the presence of waste rubber accumulated greater Zn in their shoots compared to those grown in the peat: perlite media. Acid washing of rubber reduced significantly shoot Zn concentration. Shredded waste rubber might be used as a component of container media in production of hydroponically-grown tomato. However, acid-washing of rubber is required to prevent potential Zn toxicity for plant.