Extracting Insoluble Inorganic Phosphorus from Organic Farm Soils in Mountains: Identifying Effective Organic Acid Extractants

Abstract

Phosphorus, among others, is quite a vital nutrient for the life of a plant. Because of the dominance of iron and aluminium oxides in acidic soils, they facilitate the fixation of phosphorus which results into phosphorus deficiency in large amounts. Hence, proper replenishment of the soil phosphorus (P) is very much important to cater the need of plant P requirement for better yield and development. The agricultural soils of Meghalaya (India) are by default rich in organic contents and organic P pool contributes 15-80% of the total plant P nutrition. Moreover, a different nature of nutrient pools is present in organic farming system compared to the conventional farming system. Lack of knowledge of these pools results in an imbalanced manuring plan, which hinders successful production system. The dynamic fraction of P cannot represent the correct status of phosphorus in soils under organic production systems, as the conventional soil testing protocols do not take into account the potentially available inorganic pools of phosphorus. Hence, a different extractant that can extract such potentially available P in an acidic soil under organic production system is highly required. The mineralization, solubilization and extraction (of the potentially available P pool) by using various organic acids produced through the beneficial soil microorganisms can serve this purpose. Therefore, the present research work was carried out to identify the best suitable P extractant to extract such potentially available inorganic P pool. The result of the present investigation revealed that out of 6 different extractants selected, 2% citric acid and double lactate extractants were found to be strongly correlated to the total P of the selected sites. Conventional Bray 1 extractant was taken as a check extractant. The outcome of the research is to develop a proper recommendation of fertilizer dose and an appropriate soil testing protocol for phosphorus being used in organic cultivation.