[Calibrate nitrogen and phosphorous soil test results with maize response to these nutrients under rainfed conditions in the Mixteca of Cardenas, Oaxaca State]
1988
Volke Haller, V. | Etchevers Barra, J.D.
The successful use of soil test results in making fertilizer recommendations for farmers depends upon: 1) selecting the best chemical procedure for measuring the availability of a given nutrient, and 2) calibrating the results obtained with the best method and field response data. The objective of the present study was to calibrate nitrogen and phosphorous soil test results with maize response to these nutrients under rainfed conditions in the Mixteca de Cardenas, Oax. Results from 54 field experiments conducted in the area were employed in the present study. Using regresion analysis, economic optimal rates of nitrogen and phosphorus were associated with soil contents of these nutrients as determined by soil test as well as other soil, climatic and management factors. The best regresion model for nitrogen (R*2=0.86) included three soil variables -total nitrogen, clay percentage and total carbonates-plus a drought index; the best model for phosphorus (r*2=0.845) also included three soil variables, -Bray-1 extractable phosphorus total nitrogen and total carbonates- plus a drought index. Four levels of drougth were arbitrarity defined. The long term distribution of these levels was calculated and based on this distribution, the risk due to drought was taken into account in making fertilizer recommendations.
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