Abstract:

The fertilization of potato (Solanum tuberosum L.) crop in the Andean region of Peru is strongly dependant on local sources of organic matter. A field experiment was set up to evaluate the effect of the application of four composts on some chemical properties and microbial population of an alluvial soil cultivated with potato in the farm community of Sincos (Junin-Peru). Two crop residues: wheat (Triticum aestivum L.) straw and common vetch (Vicia sativa L.) residue were composted with and without the addition of wood ash at 0.41% w/w using mixed farmyard manure. A control without organic matter application was included. Composts were applied at seeding time on plant furrows at a dose of 16.7 t ha-1. The contents of total organic C, labile C, extractable P, total N, NH4+-N, NO3--N, populations of total bacteria, actinomycetes and fungi and microbial activity were evaluated in the soil at harvest time using a complete randomized blocks design. All compost applied significantly increased the contents of organic C, extractable P and total N in the soil compared to control. Labile organic C was significantly increased by all treatments. For the content of N-NO3-; only the compost of mixed residues + ash was similar to control. All composts increased also soil basal respiration and microbial biomass carbon. Composted wheat straw + ash significantly increased soil bacterial population and produced the highest basal respiration rate, followed by compost of the mixture of residues with and without ash. Soil microbial biomass carbon was the highest after application of composted vetch residue + ash.

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