Influence of the Use of Spent Mushroom Substrates of Pleurotus Eous var. on the Availability of Phosphorus in Acid Soils of Humid Forest Regions of Côte d'Ivoire

Phosphorus (P) availability in acid soils of humid forest regions is a major constraint to the development of agriculture. In fact, the bonds between the orthophosphates and iron and aluminum oxides and hydroxides in quantity in these soils give to them abilities to fix P, reducing its availability for plant nutrition. The inputs of P in different forms actually contribute to meeting the needs of the crops, but remain under-exploited because of the very high P binding capacity of these soils, which further increases the acidity of the soils. The addition of organic matter contributes significantly to reduce the fixing power of P and increasing the availability of this nutrient (Eastwood and Sartain, 1990). The residual substrates for mushroom production or spent mushroom substrates (SMS), in increasing quantity in the subregion due to the development of mushroom cultivation, may be an alternative. Indeed, rich in organic matter and with a near neutral pH, the add of these substrates to the soil makes it possible to reduce the sites of fixation of the metal ions, lowering the P fixation capacity and increasing its availability (Sun and al. ., 2008). Experiment conducted for this purpose by application of two residual substrates S1 and S2 from fungi production on acid soils from two sites in the humid forest zone in Côte d'Ivoire, including Man and Abengourou respectively to the west and in the eastern part of the country has shown a decrease in the binding capacity of P. According to the results, the decrease in the fixing power of P depends on the characteristics of the substrate, including the pH but also the rate of incorporation of substrate into soil. Thus, the S2 substrate from a rice straw compost is more appropriate for lowering the ability or P-fixing ability of acid soils in moist forest regions. In fact, a contribution of 15p.c. by volume of this substrate suffices to impact the availability of P in the soils.