COMPARISON OF UNIFORM AND VARIABLE RATE FERTILIZER APPLICATIONS USING A VARIABLE RATE LIQUID APPLICATOR

Authors: Everitt, James; YANG, CHENGHAI - TX A&M EXPERIMENT STATION; Bradford, Joe

Submitted to: Transactions of the ASAE
Publication Type: Proceedings
Publication Acceptance Date: 8/20/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Variable rate fertilizer application enables farmers to improve fertilizer use efficiency, increase economic returns, and reduce environmental impacts by adjusting rates of fertilizers to specific conditions within discrete areas of a field. During the 1997 and 1998 growing seasons, a variable rate applicator, capable of varying two liquid fertilizers, was used to compare yield difference and economic returns resulting from uniform and variable rate fertilizer applications. The experiment was conducted on 18 experimental plots across three 14-ha grain sorghum fields based on a statistical design. A yield monitor was used to measure grain yields from the plots. Although dry weather conditions greatly reduced grain yields in both years, the variable rate fertilizer application resulted in significantly higher grain yields than the uniform treatments. Moreover, the variable rate treatment had a positive economic return ($30/ha) over the uniform treatments for 1998. These results showed that variable rate fertilization could increase yield and economic returns.

Technical Abstract: Variable rate fertilizer application has the potential to improve fertilizer use efficiency, increase economic returns and reduce environmental impacts. During the 1997 and 1998 growing seasons, a variable rate applicator, capable of varying two liquid fertilizers, was used to evaluate three fertility strategies: conventional uniform N; uniform N and P; and variable rate N and P. The three treatments were assigned in six blocks across three 14-ha grain sorghum fields in a randomized complete block design. A yield monitor was used to measure grain yields from the 18 experimental plots. Although adverse weather conditions greatly reduced grain yields in both years, the variable rate treatment resulted in significantly higher grain yields than the uniform treatments. Moreover, the variable rate treatment had a positive economic return over the uniform treatments for 1998. These results showed that variable rate fertilization could increase yield and economic returns. More experiments will be conducted to evaluate the long-term agronomic, economic and environmental viability of variable rate technology.