Which of the following is the best measure of plant available phosphorus in soil?

Soil Test Phosphorus is the best measure of plant available phosphorus in soil because it directly assesses the concentration of phosphorus that is readily available for uptake by plants. This test typically involves extracting phosphorus from a soil sample using specific chemical solutions that mimic the conditions in which plants would absorb nutrients.

The results from this test provide a quantitative measure of the phosphorus levels and can help guide fertilization practices to ensure that crops receive the optimal amount of this essential nutrient for growth and development.

In contrast, while soil organic matter contributes to the long-term availability of nutrients and supports overall soil health, it does not directly quantify immediate phosphorus availability. Soil pH can influence nutrient availability, including phosphorus, but does not measure it directly. Soil texture analysis focuses on the physical composition of the soil (sand, silt, clay) and its influence on water retention and drainage, but this does not assess phosphorus levels. Therefore, Soil Test Phosphorus is the most appropriate choice for determining the availability of phosphorus for plant uptake.