Cotton Gin Compost As an Alternative Substrate for Horticultural Crop Production

Abstract

Nursery and greenhouse vegetable growers are always concerned about the availability and cost of materials used as substrates in their production systems. In recent years, alternative organic substrate components have increased in demand, yet pine bark (PB) remains the most common and traditional substrate for horticultural crop production. With increasing concerns over the availability and consistency of PB, the need for alternative substrates to be incorporated into production systems is even more urgent today that in the past. Cotton gin compost (CGC) is one such organic substrate that is abundant in the Southeastern U.S. and has potential use as a substrate, or substrate amendment for horticultural crops.

In a greenhouse study three common species, Lycopersicon esculentum ‘Blitz’, Ficus benjamina, and Lantana camara ‘Hot Country’, were grown in increasing ratios of PB:CGC. Plants were grown in Horhizotrons™ and root growth was evaluated every week to observe root growth rates and distribution in the different treatments. Root growth of all species in all substrates containing CGC had increased root growth and higher proliferation of roots in the root ball.

In a greenhouse study, Lycopersicon esculentum ‘Blitz’ were potted into six PB:CGC substrate blends. Tomato yield and quality were evaluated over the course of two different studies conducted in 2004. Physical and chemical properties of each substrate were determined at the beginning of experiment. Tomato yield in both spring and fall of 2004 was similar in substrates containing CGC compared to the PB control. Total yields and marketable yields were similar among treatments in each season (early, mid, and late) of both studies. Cull percentages of total yield were low in both studies and did not differ in either study among any treatment.