TEXAS A&M AGRILIFE ROLLING PLAINS AGRONOMY PROGRAM

DIVERSIFYING ORGANIC COTTON PRODUCTION IN SEMI-ARID ENVIRONMENTS OF TEXAS

PI: Paul DeLaune

Project summary, goals, and objectives

Objective 2 update (September 2022-August 2023)

Determine the effects of compost application rate and placement on soil nutrient cycling, greenhouse gas emissions and agronomic and economic viability of organic systems

This portion of the project was initiated with the planting of a rye cover crop in fall 2022 at both the Lubbock and Vernon locations. Greenhouse gas fluxes were monitored throughout the 2022 and 2023 cotton growing season (May-October). Compost applications were made 3-6 weeks after cotton emergence. Compost treatments included a surface broadcast application rate of 8.96 Mg ha-1. The surface broadcast application was not incorporated as applications were made post-germination. Subsurface applications were made post-emergence at about 15 cm from the row and 15 cm deep at rates of 4.48 and 8.96 Mg ha-1. These applications occurred on the same plots as 2022. In 2023, poor stands due to seed quality led to re-planting at the Vernon location while it was deemed too late to re-plant at the Lubbock location. Subsurface applications decreased soil nitrate concentrations relative to broadcast applications. It is hypothesized this is due to an increase in microbial activity and immobilization/greater use of the nitrate pool. In contrast, significant increases in soil ammonium were observed early in season in subsurface treatments at Vernon whereas broadcast and subsurface applications had similar nitrate content. Initial data from the 2022 growing season indicated significant differences in GHG fluxes only at Vernon, where high subsurface compost applications had greater fluxes. Collected data from 2023 are undergoing analysis.