Cellulose Acetate Film and Layered Double Hydroxide as Determination Method of Available Phosphorus in the Soil

Abstract

The determination of available phosphorus (P) in soil is essential to the evaluation of the current fertility status, and therefore, for recommending the required phosphate fertilizers for the cultivation of crops. The mostly used extractants around the country are Mehlich-1 (M-1) and anionic resins (AR) and mixed resins (MR). However, there are still controversies in relation to the method that should be used, due to of particularities of each extractor. Therefore, the main objectives of this work was to assess the applicability of films of binary combination between cellulose acetate (CA) biopolymer and calcinated layered double hydroxide (LDH-c), named CAF-LDH-c, as a new extractor of available P in soils. For this, two experiments were set out. In the first one, sub-samples of an Oxisol layer 0-20 cm were used and submitted to increasing doses of total P (0, 250, 750 and 2,250 mg/dm 3) in the form of monoammonium phosphate (MAP) at different incubation time (5, 30, 60 and 90 d). In the second experiment, samples of 20 soils from different origins and contents of available P were used with distinct chemical and physical attributes. The analysis of available P by M-1, AR, MR, Mehlich-3 (M-3) and CAF-LDH-c extractants was done in both experiments. The efficiency of the extractants was evaluated by Pearson's linear correlation. The correlation between values of P extracted from soil in the first experiment was highly significant among all extraction methods used, including for CAF-LDH-c. In the second experiment, CAF-LDH-c showed significant correlation (p < 0.01) with M-1, M-3, AR and MR. Thus, the significant correlations of the extractant being tested (CAF-LDH-c) with those usually used indicates the possibility of this new method of routine laboratories for assessing the P availability of for the cultivation of crops.