PHOSPHORUS FRACTIONS IN SOIL AMENDED BY MANURE, INORGANIC AND BIO NITROGEN FERTILIZERS UNDER VARIOUS INCUBATION PERIODS

The peril of phosphorus wastage from manured soils is more related to phosphorus fraction than the total phosphorus concentration in manure. Biogeochemical change of different forms of organic and inorganic phosphorus controls soil phosphorus availability. This study aimed to assess the impact of different nitrogen fertilizers (slow or fast release mineral, organic and bio) under various incubation periods (14, 30 and 60 days) on soil phosphorus forms. Under treatment of fast release nitrogen + organic + bio fertilizers (FOB), total and organic P increased by increasing incubation period to one month, then decreased when the incubation period reached two months. The inorganic P decreased as the incubation period increased while the opposite trend was noticed for available P. The treatments of slow release nitrogen + organic + bio fertilizers (SOB), fast release nitrogen + organic fertilizers (FO) and slow release nitrogen + organic fertilizers (SO) realized an increase in both total and organic P by increasing the incubation period. As the incubation period increased, the SOB, FO and SO treatments decreased the inorganic P while the available P remained almost constant. Under the OB treatment (organic + bio fertilizers), both total and organic P were decreased as the incubation period increased. The inorganic P changed slightly and the available P increased by increasing the incubation period. After 14 days of incubation period, the low values of C:P ratio (2830) that resulted from OB and C treatments maximized the values of available P (35.5136.85 ppm), organic P (247.1 – 258.8 ppm) and total P (314.9 – 331.0 ppm), while reduced the value of inorganic p (67.8472.19 ppm) and the opposite trend was true. After one month incubation period, a decrease in C:P ratio with FO, SO and OB treatments was erved. The highest values of both total P (351.8 ppm) and available P (40.1 ppm) were recorded at C:P ratio value of 29. The least values of both total P (197.7 ppm) and available P (18.2 ppm) were recorded at 47 C:P. After two month of incubation period, C:P ratios were less than those at 14 and 30 days incubation period under all soil treatments. Available P increased as the C:P ratio increased. The highest values of C:P ratio (35) was recorded at (41.94 ppm) available P value that resulted from FOB treatment. While, the least values of C: P ratio (28) was recorded at (26.1 ppm) available P value that resulted from FO treatment. It was noticed that the lowest C:P ratio and the highest value of available P were recorded under OB treatment.