FACTOR INTERACTIONS AND THEIR INFLUENCE ON HYDROLYSIS OF CONDENSED PHOSPHATES IN SOILS1

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Abstract
In a laboratory study, we determined the main and first-order interactive effects of soil moisture, organic matter content, temperature, pH, texture, and incubation time on hydrolysis of pyrophosphate and tripolyphosphate. We used six diverse soils from Texas that were classified as entisols, alfisols, or vertisols and ranged in pH from 4.3 to 7.9, in organic matter contents from 0.8 to 4.9%, and in texture from loams to clay. Significant main effects for pyrophosphate hydrolysis were soil texture, pH, moisture content, temperature, and time; tripolyphosphate hydrolysis was affected only by soil pH, temperature, and time. The main effects did not represent statistically valid indications of the importance of these parameters on hydrolysis, however, because these factors were also involved in significant interactions. Significant interactions for pyrophosphate hydrolysis were texture .times. organic matter content, texture .times. pH, texture .times. time, organic matter .times. time, pH .times. soil moisture, pH .times. time, and temperature .times. time. Texture .times. moisture, pH .times. moisture, pH .times. time, moisture .times. time, and temperature .times. time were interactions that significantly altered hydrolysis of tripolyphosphate. The presence of interactions demonstrated that the studied parameters were not independent and confirmed the intricacy of polyphosphate hydrolysis reactions. Significant interactions were delineated into component factors to determine the nature of each interaction and its influence on hydrolysis.