ChileanJAR

In a Typic Haploxerand soil (Santa Bárbara) from the VIII Region, Chile, the effect of the addition of N and P on mineralization of C and N as indicators of the rate of wheat (Triticum aestivum L.) straw decomposition was studied. Wheat straw was either left as a cover or incorporated into the soil in combination with N (0 and 100 mg kg^-1 soil) and P applications (0 and 65 mg kg^-1 soil). Respiratory activity of microbial biomass was determined by soil incubation without air influx. Results showed highly significant effects (P ≤ 0.01) of wheat straw and P treatments on C mineralization. Wheat straw treatments showed 3 to 4 times more mineralization than the control treatment without straw. There was a greater positive effect on C mineralization when the straw was incorporated (12-15% higher) than when it was only left on the soil surface until 32 days and the application of P until day 12. There was no significant (P ≤ 0.01) effect of N application on C mineralization. There was no difference in the rate of straw decomposition in the treatments with straw on the soil surface. Soil-N mineralization increased at 92 days with N addition to the soil. The average values determined were 90.18 and 33.79 mg N kg^-1 soil for treatments with and without N addition, respectively. However, straw addition caused highly significant immobilization of N at both 45 and 92 days.