Impact of Compost Application on Citrus Production under Drip and Microjet Spray Irrigation Systems

摘要

Texas is the third largest citrus producing state in the USA, after Florida and California. The majority of citrus in the Lower Rio Grande Valley (LRGV) of south Texas is grown under flood irrigation. Due to rapid urban development, periodic droughtsand dependence upon irrigation water flows along the Rio Grande River, the semi arid conditions of South Texas commonly results in rapid decline in irrigation water supplies. Perennial crops in the LRGV, like citrus, have an annual evapotranspiration demand that far exceeds annual precipitation in this semi-arid climate. Due to limited water supplies, alternative irrigation and cultural practices are being sought to increase the irrigation use efficiency, enhance plant growth and sustain citrus crop production. A field experiment was conducted from 2003 to 2006 at the Texas A&M University-Kingsville, Citrus Center located in Weslaco, Texas. In this study, 20 year old Rio Red grapefruit trees {Citrus paradisi Macf.) received compost and non-compost treatments and were compared using drip and micro-jet spray irrigation systems. The objectives of this study were to evaluate whether annual compost and fertilization application would positively impact citrus root development, growth, and crop production under low-flow irrigation systems, drip and microjet spray. After one year of compost application, a trend of higher crop production was observed in three consecutive harvest years in composted trees compared to non-composted trees under both irrigation systems. Root density was found to be higher under composted than non-composted tree canopies, and a more uniform root growth proliferation was observed under microjet spray than drip irrigated systems. Furthermore, soil moisture sensing equipment continually showed higher soil moisture content under composted vs non-composted trees, suggesting that annual compost application under low water use systems may be ideal for improving water conservation in citrus production for south Texas.