Impact of Several Levels of Calcium Phosphate Fertilization on Distribution, Partitioning, and Lability of Soil Phosphorus under Corn-Wheat System

ABSTRACT

Determining how soil-crop management practices affect phosphorus partition and lability in soil may further our understanding of the soil P cycle. The objective of the work was to assessed the long-term effect of P fertilization on different soil P fractions. This study evaluated changes in soil P fractions as affected by long-term P fertilization under conventional tillage. Different P level applied soil samples were sequentially extracted to separate P into distilled deionized water-extractable, 2 M KCl solution-extractable, 0.1 M NaOH-extractable, 4. 0.1 M HCl-extractable, 0.5 M NaOH-extractable, and HCl: HNO3 mixture (2:5) fractions. Changes of all soil P fractions were indicating the occurrence of soil P transformation and movement over the time. The resin-extractable P, H₂O-extractable and NaOH-extractable P were significantly increased under long-term P fertilization. The highest P applied soil had the highest total phosphorus (PT) contents. Also the percent distribution of Ca and Mg‐bound P CaMgP, humic HaP and fulvic acid, and FaP increased with P fertilizer level increases. The other extraction P level did not increase vary consistently with increasing levels of P fertilization. Also soil P lability except soluble reactive phosphorus (SRP), KCl extractable phosphorus (EP), and particulate organic phosphorus (POP) increased consistently by P fertilization. Increasing P fertilization significantly (p < .001) increased the phosphorus management index (PMI) of extracted P fractions except for EP. The work demonstrated that P under long-term corn-wheat treated soils changed as a result of changes in labile P fractions probably due to the solubilization of residual fertilizer P joined with corn/wheat crop rotation factors. The highest P applied soil had the highest total phosphorus (PT) contents.

KEYWORDS:

• Conventional tillage
• soluble reactive P
• humic acid P
• calcium-bound P
• P management index
• stratification