Composted Cotton Stalks and Cotton Gin Trash Substrate Amendments and Irrigation/Ground Cover Management I. Effect on Physical and Chemical Properties of Pine Bark and Pine Tree Substrates

Abstract

This project evaluated two cotton waste products (cotton stalks and cotton gin trash) as amendments to pine bark (PB) and pine tree (PT) substrates for their impact on substrate physical and chemical properties. PB or PT substrates were amended (v/v) with cotton stalks composted with a N source (CSN), cotton stalks composted without an N source (CS), or aged cotton gin trash (CGT) at 4:1 PB:CS (PB:CS), 4:1 PB:CSN (PB:CSN), 9:1 PB:CGT (PB:CGT), 1:1 PT:CS (PT:CS), 1:1 PT:CSN (PT:CSN) and 4:1 PT:CGT (PT:CGT) (by vol). In 2010, PB-amended substrates had larger percentages of coarse (> 2.0 mm) and fine (< 0.5 mm) particles while PT-amended substrates had larger percentages of medium (0.5–2.0 mm) particles. In 2011, PB-amended substrates again had larger percentages of coarse particles, while PT-amended substrates had more medium and fine particles. Generally, most physical properties were within adequate ranges and were better than or comparable to the 100% PB control. Substrate solution pH was generally higher in the PT- than the PB-based substrates. Electrical conductivity (EC) of the substrate solution was also generally higher in the PT-based substrates compared to the PB-based substrates. Inorganic nitrogen (NH4 + NO3 + NO2), urea, P, K, Ca, and Mg concentrations in all substrate solutions, regardless of compost addition, were all below the recommended ranges by the last sample time (October 4, 2011) for the study indicating that nutrients supplied by the composts were depleted or below detection limits. However, CGT increased substrate solution P concentrations in both PB- and PT-based substrates with both overhead, sprinkler irrigation with black geotextile weed fabric covering the ground (OH) and low-volume, spray stake irrigation with gravel covering the ground (LV).