Environmental friendliness fertilizer recommendation: Phosphorous calibration for yard long bean production in ultisol
The basic purpose of soil fertility evaluation is to provide information on the nutrient status of the soil and predict the relative response to added nutrient. The Crop Nutrient Requirement (CNR) values are those amounts of nutrients needed to produce optimum, economic yields from a fertilization standpoint. It is important to remember that these nutrient amounts are supplied to the crop from both soil and fertilizer. The amounts are applied as fertilizer only when a properly calibrated soil test indicates very small extractable amounts of these nutrients to be present in the soil.