Effects of organic compounds produced by plants on soil nutrient availability

This review aimed to compile information on the effect of plant-produced organic compounds on soil nutrient availability, especially on the cations Ca, Mg and K, and on the anion phosphate. The tillage system alters the soil chemical and physical properties, especially the nutrient availability and soil physical conditions. Due to the absence of soil plowing and deposition of crop residue on the soil surface, nutrient accumulation has been observed in soil surface layers in the no-till system. Plant organic acids call interact with the soil solid phase and occupy nutrient adsorption sites, and making nutrients more available. The addition of plant residues can promote a soil pH increment prior to humification, by complexing H and Al with plant residue compounds, maintaining more Ca, Mg and K free in solution, which in turn can increase CEC saturation by these basic cations. It is also usual to observe an increment in phosphorus availability following plant residue addition, due to P in the plant residue or the competition of residue-derived organic compounds for soil P adsorption sites. The persistency of organic compounds is also a very crucial factor in the cation and anion sorption / desorption processes in soil, and is determined by the soil microbial activity, carbon substrate bioavailability and colloid sorption.